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Sample records for molecules coherent control

  1. Coherent control of atoms and molecules

    NASA Astrophysics Data System (ADS)

    Bartels, Randy Alan

    2002-01-01

    Whenever scientific tools are significantly advanced; new discoveries soon follow. My thesis work relies on advances in ultrafast laser technology that allow precise control over the shape of sub 20-fs laser pulses. This laser system enabled many new experiments that yielded significant advances in attosecond science, atomic physics; extreme nonlinear optics, quantum chemistry, coherent control, molecular physics, ultrafast optical phase modulation, EUV coherent imagines, and EUV radiation sources. By using an automated learning control algorithm coupled to our deformable mirror pulse shaper; we have demonstrated the control of a process on an attosecond time-scale for the first time. We demonstrate the manipulation of the phase of an electron wave packet, allowing us to tailor the EUV spectrum generated by high-order harmonic generation. These optimal fields were discovered by a learning algorithm that both found an unknown optimal solution; but also discovered an unknown phase-matching mechanism that occurs in the interaction of a single atom and light pulse. We control molecular vibrational and rotational coherences with the same learning algorithm; demonstrating selective control in room temperature molecules at atmospheric pressures. Moreover, we demonstrate that modifications to the algorithm can help automatically uncover the physics of the control mechanism found by the learning algorithm. We also demonstrate a new pulse-compression technique using rotational phase modulation, where optical pulses were compressed by an order of magnitude after phase modulation by a molecular rotational coherence and subsequent propagation through a transparent window. This technique will enable efficient pulse compression in the deep-UV. Finally, we measure the coherence of EUV light generated by high-harmonic upconversion of a femtosecond laser. In phase-matched hollow-fiber geometry, the EUV light exhibits the highest inherent spatial coherence of any source in this

  2. Coherent optimal control of photosynthetic molecules

    NASA Astrophysics Data System (ADS)

    Caruso, F.; Montangero, S.; Calarco, T.; Huelga, S. F.; Plenio, M. B.

    2012-04-01

    We demonstrate theoretically that open-loop quantum optimal control techniques can provide efficient tools for the verification of various quantum coherent transport mechanisms in natural and artificial light-harvesting complexes under realistic experimental conditions. To assess the feasibility of possible biocontrol experiments, we introduce the main settings and derive optimally shaped and robust laser pulses that allow for the faithful preparation of specified initial states (such as localized excitation or coherent superposition, i.e., propagating and nonpropagating states) of the photosystem and probe efficiently the subsequent dynamics. With these tools, different transport pathways can be discriminated, which should facilitate the elucidation of genuine quantum dynamical features of photosystems and therefore enhance our understanding of the role that coherent processes may play in actual biological complexes.

  3. Coherent control of single molecules at room temperature.

    PubMed

    Brinks, Daan; Hildner, Richard; Stefani, Fernando D; van Hulst, Niek F

    2011-01-01

    The detection of individual molecules allows to unwrap the inhomogeneously broadened ensemble and reveal the spatial disorder and temporal dynamics of single entities. During 20 years of increasing sophistication this approach has provided valuable insights into biomolecular interactions, cellular processes, polymer dynamics, etc. Unfortunately the detection of fluorescence, i.e. incoherent spontaneous emission, has essentially kept the time resolution of the single molecule approach out of the range of ultrafast coherent processes. In parallel coherent control of quantum interferences has developed as a powerful method to study and actively steer ultrafast molecular interactions and energy conversion processes. However the degree of coherent control that can be reached in ensembles is restricted, due to the intrinsic inhomogeneity of the synchronized subset. Clearly the only way to overcome spatio-temporal disorder and achieve key control is by addressing individual units: coherent control of single molecules. Here we report the observation and manipulation of vibrational wave-packet interference in individual molecules at ambient conditions. We show that adapting the time and phase distribution of the optical excitation field to the dynamics of each molecule results in a superior degree of control compared to the ensemble approach. Phase reversal does invert the molecular response, confirming the control of quantum coherence. Time-phase maps show a rich diversity in excited state dynamics between different, yet chemically identical, molecules. The presented approach is promising for single-unit coherent control in multichromophoric systems. Especially the role of coherence in the energy transfer of single antenna complexes under physiological conditions is subject of great attention. Now the role of energy disorder and variation in coupling strength can be explored, beyond the inhomogeneously broadened ensemble.

  4. Coherent Control of Ground State NaK Molecules

    NASA Astrophysics Data System (ADS)

    Yan, Zoe; Park, Jee Woo; Loh, Huanqian; Will, Sebastian; Zwierlein, Martin

    2016-05-01

    Ultracold dipolar molecules exhibit anisotropic, tunable, long-range interactions, making them attractive for the study of novel states of matter and quantum information processing. We demonstrate the creation and control of 23 Na40 K molecules in their rovibronic and hyperfine ground state. By applying microwaves, we drive coherent Rabi oscillations of spin-polarized molecules between the rotational ground state (J=0) and J=1. The control afforded by microwave manipulation allows us to pursue engineered dipolar interactions via microwave dressing. By driving a two-photon transition, we are also able to observe Ramsey fringes between different J=0 hyperfine states, with coherence times as long as 0.5s. The realization of long coherence times between different molecular states is crucial for applications in quantum information processing. NSF, AFOSR- MURI, Alfred P. Sloan Foundation, DARPA-OLE

  5. Observation and control of coherent torsional dynamics in a quinquethiophene molecule.

    PubMed

    Cirmi, Giovanni; Brida, Daniele; Gambetta, Alessio; Piacenza, Manuel; Della Sala, Fabio; Favaretto, Laura; Cerullo, Giulio; Lanzani, Guglielmo

    2010-07-28

    By applying femtosecond pump-probe spectroscopy to a substituted quinquethiophene molecule in solution, we observe in the time domain the coherent torsional dynamics that drives planarization of the excited state. Our interpretation is based on numerical modeling of the ground and excited state potential energy surfaces and simulation of wavepacket dynamics, which reveals two symmetric excited state deactivation pathways per oscillation period. We use the acquired knowledge on torsional dynamics to coherently control the excited state population with a pump-dump scheme, exploiting the non-stationary Franck-Condon overlap between ground and excited states.

  6. Sub-nanometre control of the coherent interaction between a single molecule and a plasmonic nanocavity

    NASA Astrophysics Data System (ADS)

    Zhang, Yao; Meng, Qiu-Shi; Zhang, Li; Luo, Yang; Yu, Yun-Jie; Yang, Ben; Zhang, Yang; Esteban, Ruben; Aizpurua, Javier; Luo, Yi; Yang, Jin-Long; Dong, Zhen-Chao; Hou, J. G.

    2017-05-01

    The coherent interaction between quantum emitters and photonic modes in cavities underlies many of the current strategies aiming at generating and controlling photonic quantum states. A plasmonic nanocavity provides a powerful solution for reducing the effective mode volumes down to nanometre scale, but spatial control at the atomic scale of the coupling with a single molecular emitter is challenging. Here we demonstrate sub-nanometre spatial control over the coherent coupling between a single molecule and a plasmonic nanocavity in close proximity by monitoring the evolution of Fano lineshapes and photonic Lamb shifts in tunnelling electron-induced luminescence spectra. The evolution of the Fano dips allows the determination of the effective interaction distance of ~1 nm, coupling strengths reaching ~15 meV and a giant self-interaction induced photonic Lamb shift of up to ~3 meV. These results open new pathways to control quantum interference and field-matter interaction at the nanoscale.

  7. Coherent control of the formation of cold heteronuclear molecules by photoassociation

    NASA Astrophysics Data System (ADS)

    de Lima, Emanuel F.

    2017-01-01

    We consider the formation of cold diatomic molecules in the electronic ground state by photoassociation of atoms of dissimilar species. A combination of two transition pathways from the free colliding pair of atoms to a bound vibrational level of the electronic molecular ground state is envisioned. The first pathway consists of a pump-dump scheme with two time-delayed laser pulses in the near-infrared frequency domain. The pump pulse drives the transition to a bound vibrational level of an excited electronic state, while the dump pulse transfers the population to a bound vibrational level of the electronic ground state. The second pathway takes advantage of the existing permanent dipole moment and employs a single pulse in the far-infrared domain to drive the transition from the unbound atoms directly to a bound vibrational level in the electronic ground state. We show that this scheme offers the possibility to coherently control the photoassociation yield by manipulating the relative phase and timing of the pulses. The photoassociation mechanism is illustrated for the formation of cold LiCs molecules.

  8. Coherent control of ultracold molecule dynamics in a magneto-optical trap by use of chirped femtosecond laser pulses.

    PubMed

    Brown, Benjamin L; Dicks, Alexander J; Walmsley, Ian A

    2006-05-05

    We have studied the effects of chirped femtosecond laser pulses on the formation of ultracold molecules in a Rb magneto-optical trap. We have found that application of chirped femtosecond pulses suppressed the formation of (85)Rb and (87)Rb(2) a(3)sigma(+)(u) molecules in contrast to comparable nonchirped pulses, cw illumination, and background formation rates. Variation of the amount of chirp indicated that this suppression is coherent in nature, suggesting that coherent control is likely to be useful for manipulating the dynamics of ultracold quantum molecular gases.

  9. Coherent control of Forster energy transfer in nanoparticle molecules: energy nanogates and plasmonic heat pulses

    NASA Astrophysics Data System (ADS)

    Sadeghi, S. M.; West, R. G.

    2011-10-01

    We study how Forster energy transfer from a semiconductor quantum dot to a metallic nanoparticle can be gated using quantum coherence in quantum dots. We show this allows us to use a laser field to open the flow of the energy transfer for a given period of time (on-state) before it is switched off to about zero. Utilizing such an energy gating process it is shown that quantum-dot-metallic-nanoparticle systems (meta-molecules) can act as functional nanoheaters capable of generating heat pulses with temporal widths determined by their environmental and physical parameters. We discuss the physics behind the energy nanogates using molecular states of such meta-molecules and the resonance fluorescence of the quantum dots.

  10. Chip-Based All-Optical Control of Single Molecules Coherently Coupled to a Nanoguide.

    PubMed

    Türschmann, Pierre; Rotenberg, Nir; Renger, Jan; Harder, Irina; Lohse, Olga; Utikal, Tobias; Götzinger, Stephan; Sandoghdar, Vahid

    2017-08-09

    The feasibility of many proposals in nanoquantum-optics depends on the efficient coupling of photons to individual quantum emitters, the possibility to control this interaction on demand, and the scalability of the experimental platform. To address these issues, we report on chip-based systems made of one-dimensional subwavelength dielectric waveguides (nanoguides) and polycyclic aromatic hydrocarbon molecules. We discuss the design and fabrication requirements, present data on extinction spectroscopy of single molecules coupled to a nanoguide mode, and show how an external optical beam can switch the propagation of light via a nonlinear optical process. The presented architecture paves the way for the investigation of many-body phenomena and polaritonic states and can be readily extended to more complex geometries for the realization of quantum integrated photonic circuits.

  11. Atom-molecule coherence in a Bose-Einstein condensate.

    PubMed

    Donley, Elizabeth A; Claussen, Neil R; Thompson, Sarah T; Wieman, Carl E

    2002-05-30

    Recent advances in the precise control of ultracold atomic systems have led to the realisation of Bose Einstein condensates (BECs) and degenerate Fermi gases. An important challenge is to extend this level of control to more complicated molecular systems. One route for producing ultracold molecules is to form them from the atoms in a BEC. For example, a two-photon stimulated Raman transition in a (87)Rb BEC has been used to produce (87)Rb(2) molecules in a single rotational-vibrational state, and ultracold molecules have also been formed through photoassociation of a sodium BEC. Although the coherence properties of such systems have not hitherto been probed, the prospect of creating a superposition of atomic and molecular condensates has initiated much theoretical work. Here we make use of a time-varying magnetic field near a Feshbach resonance to produce coherent coupling between atoms and molecules in a (85)Rb BEC. A mixture of atomic and molecular states is created and probed by sudden changes in the magnetic field, which lead to oscillations in the number of atoms that remain in the condensate. The oscillation frequency, measured over a large range of magnetic fields, is in excellent agreement with the theoretical molecular binding energy, indicating that we have created a quantum superposition of atoms and diatomic molecules two chemically different species.

  12. Quantum chaos meets coherent control.

    PubMed

    Gong, Jiangbin; Brumer, Paul

    2005-01-01

    Coherent control of atomic and molecular processes has been a rapidly developing field. Applications of coherent control to large and complex molecular systems are expected to encounter the effects of chaos in the underlying classical dynamics, i.e., quantum chaos. Hence, recent work has focused on examining control in model chaotic systems. This work is reviewed, with an emphasis on a variety of new quantum phenomena that are of interest to both areas of quantum chaos and coherent control.

  13. Coherent control of plasma dynamics.

    PubMed

    He, Z-H; Hou, B; Lebailly, V; Nees, J A; Krushelnick, K; Thomas, A G R

    2015-05-15

    Coherent control of a system involves steering an interaction to a final coherent state by controlling the phase of an applied field. Plasmas support coherent wave structures that can be generated by intense laser fields. Here, we demonstrate the coherent control of plasma dynamics in a laser wakefield electron acceleration experiment. A genetic algorithm is implemented using a deformable mirror with the electron beam signal as feedback, which allows a heuristic search for the optimal wavefront under laser-plasma conditions that is not known a priori. We are able to improve both the electron beam charge and angular distribution by an order of magnitude. These improvements do not simply correlate with having the 'best' focal spot, as the highest quality vacuum focal spot produces a greatly inferior electron beam, but instead correspond to the particular laser phase front that steers the plasma wave to a final state with optimal accelerating fields.

  14. Coherent spectroscopy in the single molecule limit (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Potma, Eric O.; Crampton, Kevin; Fast, Alex; Alfonso García, Alba; Apkarian, Vartkess A.

    2016-10-01

    Surface enhanced Raman scattering (SERS) is a popular technique for detecting and analyzing molecules at very low concentrations. The sensitivity of SERS is high enough to detect single molecules. It has proven difficult, however, to perform similar measurements in the so-called nonlinear optical regime, a regime in which the molecule is responding to multiple light pulses. Nonetheless, recent experiments indicate that after careful optimization, it is possible to generate signals derived from nonlinear analogs of SERS. Such measurements make it possible to view molecular vibrations in real time, which amounts to the femto- to pico-second range. In this contribution, we discuss in detail under which conditions detectable surface-enhanced coherent Raman signals can be expected, provide experimental evidence of coherent Raman scattering of single molecules, and highlight the unique information that can be attained from such measurements.

  15. Nonlinear coherent spectroscopy in the single molecule limit (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Potma, Eric O.

    2015-10-01

    Detecting coherent anti-Stokes Raman scattering (CARS) signals from signal molecules is a longstanding experimental challenge. Driving the vibrational CARS response with surface plasmon fields has proven notoriously difficult due to strong background contributions, unfavorable heat dissipation and the phase dispersion of the plasmon modes in the ensemble. In this work we overcome previous experimental limitations and demonstrate time-resolved, vibrational CARS from molecules in the low copy number limit, down to the single molecule level. Our measurements, which are performed under ambient and non-electronic resonance conditions, establish that the coherent response from vibrational modes of individual molecules can be studied experimentally, opening up a new realm of molecular spectroscopic investigations.

  16. Coherent controlization using superconducting qubits

    PubMed Central

    Friis, Nicolai; Melnikov, Alexey A.; Kirchmair, Gerhard; Briegel, Hans J.

    2015-01-01

    Coherent controlization, i.e., coherent conditioning of arbitrary single- or multi-qubit operations on the state of one or more control qubits, is an important ingredient for the flexible implementation of many algorithms in quantum computation. This is of particular significance when certain subroutines are changing over time or when they are frequently modified, such as in decision-making algorithms for learning agents. We propose a scheme to realize coherent controlization for any number of superconducting qubits coupled to a microwave resonator. For two and three qubits, we present an explicit construction that is of high relevance for quantum learning agents. We demonstrate the feasibility of our proposal, taking into account loss, dephasing, and the cavity self-Kerr effect. PMID:26667893

  17. Mode Selective Excitation Using Coherent Control Spectroscopy

    SciTech Connect

    Singh, Ajay K.; Konradi, Jakow; Materny, Arnulf; Sarkar, Sisir K.

    2008-11-14

    Femtosecond time-resolved coherent anti-Stokes Raman scattering (fs-CARS) gives access to ultrafast molecular dynamics. However, femtosecond laser pulses are spectrally broad and therefore coherently excite several molecular modes. While the temporal resolution is high, usually no mode-selective excitation is possible. This paper demonstrates the feasibility of selectively exciting specific molecular vibrations in solution phase with shaped fs laser excitation using a feedback-controlled optimization technique guided by an evolutionary algorithm. This approach is also used to obtain molecule-specific CARS spectra from a mixture of different substances. The optimized phase structures of the fs pulses are characterized to get insight into the control process. Possible applications of the spectrum control are discussed.

  18. Spin coherence in a Mn3 single-molecule magnet

    NASA Astrophysics Data System (ADS)

    Abeywardana, Chathuranga; Mowson, Andrew M.; Christou, George; Takahashi, Susumu

    2016-01-01

    Spin coherence in single crystals of the spin S = 6 single-molecule magnet (SMM) [Mn3O(O2CEt)3(mpko)3]+ (abbreviated Mn3) has been investigated using 230 GHz electron paramagnetic resonance spectroscopy. Coherence in Mn3 was uncovered by significantly suppressing dipolar contribution to the decoherence with complete spin polarization of Mn3 SMMs. The temperature dependence of spin decoherence time (T2) revealed that the dipolar decoherence is the dominant source of decoherence in Mn3 and T2 can be extended up to 267 ns by quenching the dipolar decoherence.

  19. Quantum Zeno control of coherent dissociation

    SciTech Connect

    Khripkov, C.; Vardi, A.

    2011-08-15

    We study the effect of dephasing on the coherent dissociation dynamics of an atom-molecule Bose-Einstein condensate. We show that when phase-noise intensity is strong with respect to the inverse correlation time of the stimulated process, dissociation is suppressed via a Bose enhanced quantum Zeno effect. This is complementary to the quantum Zeno control of phase-diffusion in a bimodal condensate by symmetric noise [Phys. Rev. Lett. 100, 220403 (2008)] in that the controlled process here is phase formation and the required decoherence mechanism for its suppression is purely phase noise.

  20. Atom-Molecule Coherence in a One-Dimensional System

    NASA Astrophysics Data System (ADS)

    Citro, R.; Orignac, E.

    2005-09-01

    We study a model of one-dimensional fermionic atoms with a narrow Feshbach resonance that allows them to bind in pairs to form bosonic molecules. We show that at low energy, a coherence develops between the molecule and fermion Luttinger liquids. At the same time, a gap opens in the spin excitation spectrum. The coherence implies that the order parameters for the molecular Bose-Einstein condensation and the atomic BCS pairing become identical. Moreover, both bosonic and fermionic charge density wave correlations decay exponentially, in contrast with a usual Luttinger liquid. We exhibit a Luther-Emery point where the systems can be described in terms of noninteracting pseudofermions. At this point we discuss the threshold behavior of density-density response functions.

  1. Coherent Control of Quantum Matter

    SciTech Connect

    Cavalleri, Andrea

    2011-10-05

    This talk addresses some recent work aimed at controlling the low-lying electrodynamics of quantum solids using strong field transients. The excitation of selected vibrational resonances to manipulate the many-body physics of one dimensional Mott Hubbard Insulators and to perturb competing orders in High-Tc superconductors is also covered. Finally, the speaker shows how the electrodynamics of layered superconductors can be driven through the orderparameter phase gradient, demonstrating ultrafast transistor action in a layered superconductor. Advances in the use of coherent optics, from tabletop sources to THz and x-ray free-electron lasers are also discussed.

  2. Spectrally resolved coherent transient signal for ultracold rubidium molecules

    NASA Astrophysics Data System (ADS)

    Eimer, F.; Weise, F.; Merli, A.; Birkner, S.; Sauer, F.; Wöste, L.; Lindinger, A.; Aç§Anoç§Lu, R.; Koch, C. P.; Salzmann, W.; Mullins, T.; Götz, S.; Wester, R.; Weidemüller, M.

    2009-09-01

    We present spectrally resolved pump-probe experiments on the photoassociation of ultracold rubidium atoms with shaped ultrashort laser pulses. The pump pulse causes a free-bound transition leading to a coherent transient signal of rubidium molecules in the first excited state. In order to achieve a high frequency resolution the bandwidth of the pump pulse is reduced to a few wavenumbers. The frequency dependence of the transient signal close to the D1 atomic resonance is investigated for characteristic pump-probe delay times. The observed spectra, which show a pronounced dip for pump-probe coincidence, are interpreted using quantum dynamical calculations.

  3. Coherent Dynamics Following Strong Field Ionization of Polyatomic Molecules

    NASA Astrophysics Data System (ADS)

    Konar, Arkaprabha; Shu, Yinan; Lozovoy, Vadim; Jackson, James; Levine, Benjamin; Dantus, Marcos

    2015-03-01

    Molecules, as opposed to atoms, present confounding possibilities of nuclear and electronic motion upon strong field ionization. The dynamics and fragmentation patterns in response to the laser field are structure sensitive; therefore, a molecule cannot simply be treated as a ``bag of atoms'' during field induced ionization. We consider here to what extent molecules retain their molecular identity and properties under strong laser fields. Using time-of-flight mass spectrometry in conjunction with pump-probe techniques we study the dynamical behavior of these molecules, monitoring ion yield modulation caused by intramolecular motions post ionization. The delay scans show that among positional isomers the variations in relative energies, amounting to only a few hundred meVs, influence the dynamical behavior of the molecules despite their having experienced such high fields (V/Å). Ab initio calculations were performed to predict dynamics along with single and multiphoton resonances in the neutral and ionic states. We propose that single electron ionization occurs within an optical cycle with the electron carrying away essentially all of the energy, leaving behind little internal energy in the cation. Evidence for this observation comes from coherent vibrational motion governed by the potential energy surface of the ground state of the cation. Subsequent fragmentation of the cation takes place as a result of further photon absorption modulated by one- and two-photon resonances, which provide sufficient energy to overcome the dissociation energy.

  4. Quantum coherence in Mn-based single molecule magnets

    NASA Astrophysics Data System (ADS)

    Abeywardana, C.; Cho, F. H.; Mowson, A.; Christou, G.; Takahashi, S.

    2015-03-01

    As spin systems in solids, single-molecule magnets (SMMs) form a unique class of materials that have a high-spin, and their spin state and interaction can be easily tuned by changing peripheral organic ligands and solvate molecules. In addition, it has been shown that an individual or a small ensemble of SMMs can be transferred to surface with retention of their magnetic behavior. SMM is therefore a promising system for fundamental quantum science and for applications to dense and efficient quantum memory, computing, and molecular spintronics devices. In spite of diverse interests on quantum properties in SMMs, decoherence properties that ultimately limit such behaviors have not been understood yet. Until now, coherent manipulation of spin states in SMMs has been experimentally demonstrated only in a few SMMs. In this presentation, we investigate quantum coherence in Mn-based SMMs using a high-frequency pulsed EPR technique, which has a significant advantage to quench the spin decoherence due to electron spins.

  5. Coherent (photon) vs incoherent (current) detection of multidimensional optical signals from single molecules in open junctions

    SciTech Connect

    Agarwalla, Bijay Kumar; Hua, Weijie; Zhang, Yu; Mukamel, Shaul; Harbola, Upendra

    2015-06-07

    The nonlinear optical response of a current-carrying single molecule coupled to two metal leads and driven by a sequence of impulsive optical pulses with controllable phases and time delays is calculated. Coherent (stimulated, heterodyne) detection of photons and incoherent detection of the optically induced current are compared. Using a diagrammatic Liouville space superoperator formalism, the signals are recast in terms of molecular correlation functions which are then expanded in the many-body molecular states. Two dimensional signals in benzene-1,4-dithiol molecule show cross peaks involving charged states. The correlation between optical and charge current signal is also observed.

  6. Design of tailored microwave pulses to create rotational coherent states for an asymmetric-top molecule

    NASA Astrophysics Data System (ADS)

    Ortigoso, Juan

    1998-06-01

    Tailored microwave pulses, to guide asymmetric-top molecules from selected rotational states belonging to the vibronic ground state to generalized angular-momentum coherent states, are designed by using optimal control theory. Characteristics that the molecules have to fulfill in order to achieve the goal with feasible pulses are discussed. Properties of the pulses are discussed as well. The further dephasing among the components of the wave packet which, for the simplest coherent state, is a form of dynamical tunneling, can be locked by exploiting the changes that energy levels and eigenfunctions undergo in the presence of an external static electric field with appropriate intensity. For the special case with M=0, periodic fields are more flexible in avoiding dephasing. This is shown by examining properties of quasienergies and dressed states resulting from the diagonalization of a truncated Floquet matrix.

  7. Experimental Demonstration of Coherent Control in Quantum Chaotic Systems

    NASA Astrophysics Data System (ADS)

    Bitter, M.; Milner, V.

    2017-01-01

    We experimentally demonstrate coherent control of a quantum system, whose dynamics is chaotic in the classical limit. Interaction of diatomic molecules with a periodic sequence of ultrashort laser pulses leads to the dynamical localization of the molecular angular momentum, a characteristic feature of the chaotic quantum kicked rotor. By changing the phases of the rotational states in the initially prepared coherent wave packet, we control the rotational distribution of the final localized state and its total energy. We demonstrate the anticipated sensitivity of control to the exact parameters of the kicking field, as well as its disappearance in the classical regime of excitation.

  8. Coherent control of photoelectron wavepacket angular interferograms

    NASA Astrophysics Data System (ADS)

    Hockett, P.; Wollenhaupt, M.; Baumert, T.

    2015-11-01

    Coherent control over photoelectron wavepackets, via the use of polarization-shaped laser pulses, can be understood as a time and polarization-multiplexed process, where the final (time-integrated) observable coherently samples all instantaneous states of the light-matter interaction. In this work, we investigate this multiplexing via computation of the observable photoelectron angular interferograms resulting from multi-photon atomic ionization with polarization-shaped laser pulses. We consider the polarization sensitivity of both the instantaneous and cumulative continuum wavefunction; the nature of the coherent control over the resultant photoelectron interferogram is thus explored in detail. Based on this understanding, the use of coherent control with polarization-shaped pulses as a methodology for a highly multiplexed coherent quantum metrology is also investigated, and defined in terms of the information content of the observable.

  9. Coherent phase control of the photodissociation of HOD

    SciTech Connect

    Allendorf, S.W.; Conaway, W.E.; Krause, J.L.

    1993-07-19

    A goal of chemical reaction dynamics is to control the course of reactions. We are examining the photodissocation of HOD, which is attractive for coherent control studies. A fixed frequency laser at 600 nm and its third harmonic at 200 nm is used to simultaneously and coherently photodissociate the rovibrationally excited parent molecules. Preliminary experiments focussed on confirming individual steps of the complex experiment; results are given of three-photon dissociation of H{sub 2}O, which gives confidence for the HOD three-photon dissociation.

  10. Quantum-Coherence-Assisted Tunable On- and Off-Resonance Tunneling through a Quantum-Dot-Molecule Dielectric Film

    NASA Astrophysics Data System (ADS)

    Shen, Jian Qi; Zeng, Rui Xi

    2017-02-01

    Quantum-dot-molecular phase coherence (and the relevant quantum-interference-switchable optical response) can be utilized to control electromagnetic wave propagation via a gate voltage, since quantum-dot molecules can exhibit an effect of quantum coherence (phase coherence) when quantum-dot-molecular discrete multilevel transitions are driven by an electromagnetic wave. Interdot tunneling of carriers (electrons and holes) controlled by the gate voltage can lead to destructive quantum interference in a quantum-dot molecule that is coupled to an incident electromagnetic wave, and gives rise to a quantum coherence effect (e.g., electromagnetically induced transparency, EIT) in a quantum-dot-molecule dielectric film. The tunable on- and off-resonance tunneling effect of an incident electromagnetic wave (probe field) through such a quantum-coherent quantum-dot-molecule dielectric film is investigated. It is found that a high gate voltage can lead to the EIT phenomenon of the quantum-dot-molecular systems. Under the condition of on-resonance light tunneling through the present quantum-dot-molecule dielectric film, the probe field should propagate without loss if the probe frequency detuning is zero. Such an effect caused by both EIT and resonant tunneling, which is sensitive to the gate voltage, can be utilized for designing devices such as photonic switching, transistors, and logic gates.

  11. Control of Population Flow in Coherently Driven Quantum Ladders

    SciTech Connect

    Garcia-Fernandez, Ruth; Bergmann, Klaas; Ekers, Aigars; Yatsenko, Leonid P.; Vitanov, Nikolay V.

    2005-07-22

    A technique for adiabatic control of the population flow through a preselected decaying excited level in a three-level quantum ladder is presented. The population flow through the intermediate or upper level is controlled efficiently and robustly by varying the pulse delay between a pair of partly overlapping coherent laser pulses. The technique is analyzed theoretically and demonstrated in an experiment with Na{sub 2} molecules.

  12. Theory of coherent control with quantum light

    NASA Astrophysics Data System (ADS)

    Schlawin, Frank; Buchleitner, Andreas

    2017-01-01

    We develop a coherent control theory for multimode quantum light. It allows us to examine a fundamental problem in quantum optics: what is the optimal pulse form to drive a two-photon-transition? In formulating the question as a coherent control problem, we show that—and quantify how much—the strong frequency quantum correlations of entangled photons enhance the transition compared to shaped classical pulses. In ensembles of collectively driven two-level systems, such enhancement requires nonvanishing interactions.

  13. Coherent Control of Thermal Transport

    DTIC Science & Technology

    2011-05-10

    sicnece research in emerging materials. List of Publications and Presesntatins: Journals: 1. Wu, A.Q., Xu, X., and Venkatasubramanian , R., 2008...February 2008 issue of Virtual Journal of Ultrafast Science. 2. Y. Wang, X. Xu, and R. Venkatasubramanian , 2008, “Reduction of Coherent Phonon... Venkatasubramanian , R., Acoustic Phonon Scattering in Bi2Te3/Sb2Te3 Superlattice, Appl. Phys. Lett., Vol. 97, p. 083103. Also selected for the September 2010

  14. Diffractive Imaging of Coherent Nuclear Motion in Isolated Molecules

    NASA Astrophysics Data System (ADS)

    Yang, Jie; Guehr, Markus; Shen, Xiaozhe; Li, Renkai; Vecchione, Theodore; Coffee, Ryan; Corbett, Jeff; Fry, Alan; Hartmann, Nick; Hast, Carsten; Hegazy, Kareem; Jobe, Keith; Makasyuk, Igor; Robinson, Joseph; Robinson, Matthew S.; Vetter, Sharon; Weathersby, Stephen; Yoneda, Charles; Wang, Xijie; Centurion, Martin

    2016-10-01

    Observing the motion of the nuclear wave packets during a molecular reaction, in both space and time, is crucial for understanding and controlling the outcome of photoinduced chemical reactions. We have imaged the motion of a vibrational wave packet in isolated iodine molecules using ultrafast electron diffraction with relativistic electrons. The time-varying interatomic distance was measured with a precision 0.07 Å and temporal resolution of 230 fs full width at half maximum. The method is not only sensitive to the position but also the shape of the nuclear wave packet.

  15. Diffractive imaging of coherent nuclear motion in isolated molecules

    DOE PAGES

    Yang, Jie; Guehr, Markus; Shen, Xiaozhe; ...

    2016-10-03

    Observing the motion of the nuclear wave packets during a molecular reaction, in both space and time, is crucial for understanding and controlling the outcome of photoinduced chemical reactions. We have imaged the motion of a vibrational wave packet in isolated iodine molecules using ultrafast electron diffraction with relativistic electrons. The time-varying interatomic distance was measured with a precision 0.07 Å and temporal resolution of 230 fs full width at half maximum. Lastly, the method is not only sensitive to the position but also the shape of the nuclear wave packet.

  16. Diffractive imaging of coherent nuclear motion in isolated molecules

    SciTech Connect

    Yang, Jie; Guehr, Markus; Shen, Xiaozhe; Li, Renkai; Vecchione, Theodore; Coffee, Ryan; Corbett, Jeff; Fry, Alan; Hartmann, Nick; Hast, Carsten; Hegazy, Kareem; Jobe, Keith; Makasyuk, Igor; Robinson, Joseph; Robinson, Matthew S.; Vetter, Sharon; Weathersby, Stephen; Yoneda, Charles; Wang, Xijie; Centurion, Martin

    2016-10-03

    Observing the motion of the nuclear wave packets during a molecular reaction, in both space and time, is crucial for understanding and controlling the outcome of photoinduced chemical reactions. We have imaged the motion of a vibrational wave packet in isolated iodine molecules using ultrafast electron diffraction with relativistic electrons. The time-varying interatomic distance was measured with a precision 0.07 Å and temporal resolution of 230 fs full width at half maximum. Lastly, the method is not only sensitive to the position but also the shape of the nuclear wave packet.

  17. Diffractive Imaging of Coherent Nuclear Motion in Isolated Molecules

    SciTech Connect

    Yang, Jie; Guehr, Markus; Shen, Xiaozhe; Li, Renkai; Vecchione, Theodore; Coffee, Ryan; Corbett, Jeff; Fry, Alan; Hartmann, Nick; Hast, Carsten; Hegazy, Kareem; Jobe, Keith; Makasyuk, Igor; Robinson, Joseph; Robinson, Matthew S.; Vetter, Sharon; Weathersby, Stephen; Yoneda, Charles; Wang, Xijie; Centurion, Martin

    2016-10-03

    Observing the motion of the nuclear wave packets during a molecular reaction, in both space and time, is crucial for understanding and controlling the outcome of photoinduced chemical reactions. We have imaged the motion of a vibrational wave packet in isolated iodine molecules using ultrafast electron diffraction with relativistic electrons. The time-varying interatomic distance was measured with a precision 0.07 Å and temporal resolution of 230 fs full width at half maximum. The method is not only sensitive to the position but also the shape of the nuclear wave packet.

  18. Cooling Mechanical Oscillators by Coherent Control

    NASA Astrophysics Data System (ADS)

    Frimmer, Martin; Gieseler, Jan; Novotny, Lukas

    2016-10-01

    In optomechanics, electromagnetic fields are harnessed to control a single mode of a mechanically compliant system, while other mechanical degrees of freedom remain unaffected due to the modes' mutual orthogonality and high quality factor. Extension of the optical control beyond the directly addressed mode would require a controlled coupling between mechanical modes. Here, we introduce an optically controlled coupling between two oscillation modes of an optically levitated nanoparticle. We sympathetically cool one oscillation mode by coupling it coherently to the second mode, which is feedback cooled. Furthermore, we demonstrate coherent energy transfer between mechanical modes and discuss its application for ground-state cooling.

  19. Coherent control over the photodissociation of CH3I

    NASA Astrophysics Data System (ADS)

    Kleiman, Valeria D.; Zhu, Langchi; Allen, Jeanette; Gordon, Robert J.

    1995-12-01

    Coherent phase control of the photodissociation of CH3I has been achieved by quantum mechanical interference between competing paths. The control was accomplished by exciting the parent molecules with three UV photons of frequency ω1 and one VUV photon of frequency ω3=3ω1. Varying the phase difference between the two laser beams resulted in a modulation of the I+ and CH+3 signals, without affecting the parent ion signal. We propose a mechanism in which control occurs over the photodissociation step to produce CH3+I*, followed by ionization of the neutral fragments by additional UV photons.

  20. Towards coherent control of energetic material initiation

    SciTech Connect

    Greenfield, Margo T; Mcgrane, Shawn D; Scharff, R Jason; Moore, David S

    2009-01-01

    Direct optical initiation (DOI) of energetic materials using coherent control of localized energy deposition requires depositing energy into the material to produce a critical size hot spot, which allows propagation of the reaction and thereby initiation, The hot spot characteristics needed for growth to initiation can be studied using quantum controlled initiation (QCI). Achieving direct quantum controlled initiation (QCI) in condensed phase systems requires optimally shaped ultrafast laser pulses to coherently guide the energy flow along the desired paths. As a test of our quantum control capabilities we have successfully demonstrated our ability to control the reaction pathway of the chemical system stilbene. An acousto-optical modulator based pulse shaper was used at 266 nm, in a shaped pump/supercontinuum probe technique, to enhance and suppress th relative yields of the cis- to trans-stilbene isomerization. The quantum control techniques tested in the stilbene experiments are currently being used to investigate QCI of the explosive hexanitroazobenzene (HNAB).

  1. Second-scale nuclear spin coherence time of ultracold 23Na40K molecules

    NASA Astrophysics Data System (ADS)

    Park, Jee Woo; Yan, Zoe Z.; Loh, Huanqian; Will, Sebastian A.; Zwierlein, Martin W.

    2017-07-01

    Coherence, the stability of the relative phase between quantum states, is central to quantum mechanics and its applications. For ultracold dipolar molecules at sub-microkelvin temperatures, internal states with robust coherence are predicted to offer rich prospects for quantum many-body physics and quantum information processing. We report the observation of stable coherence between nuclear spin states of ultracold fermionic sodium-potassium (NaK) molecules in the singlet rovibrational ground state. Ramsey spectroscopy reveals coherence times on the scale of 1 second; this enables high-resolution spectroscopy of the molecular gas. Collisional shifts are shown to be absent down to the 100-millihertz level. This work opens the door to the use of molecules as a versatile quantum memory and for precision measurements on dipolar quantum matter.

  2. Coherent control in simple quantum systems

    NASA Technical Reports Server (NTRS)

    Prants, Sergey V.

    1995-01-01

    Coherent dynamics of two, three, and four-level quantum systems, simultaneously driven by concurrent laser pulses of arbitrary and different forms, is treated by using a nonperturbative, group-theoretical approach. The respective evolution matrices are calculated in an explicit form. General aspects of controllability of few-level atoms by using laser fields are treated analytically.

  3. Coherent control of multipartite entanglement

    NASA Astrophysics Data System (ADS)

    Hashemi Rafsanjani, Seyed Mohammad; Eberly, Joseph H.

    2015-01-01

    Quantum entanglement between an arbitrary number of remote qubits is examined analytically. We show that there is a nonprobabilistic way to address in one context the management of entanglement of an arbitrary number of mixed-state qubits by engaging quantitative measures of entanglement and a specific external control mechanism. Both all-party entanglement and weak inseparability are considered. We show that for N ≥4 , the death of all-party entanglement is permanent after an initial collapse. In contrast, weak inseparability can be deterministically managed for an arbitrarily large number of qubits almost indefinitely. Our result suggests a picture of the path that the system traverses in the Hilbert space.

  4. Coherent spin control by electromagnetic vacuum fluctuations

    NASA Astrophysics Data System (ADS)

    Wang, Jing; Liu, Ren-Bao; Zhu, Bang-Fen; Sham, L. J.; Steel, D. G.

    2011-05-01

    In coherent control, electromagnetic vacuum fluctuations usually cause coherence loss through irreversible spontaneous emission. However, since the dissipation via emission is essentially due to correlation of the fluctuations, when emission ends in a superposition of multiple final states, correlation between different pathways may build up if the “which way” information is not fully resolved (i.e., the emission spectrum is broader than the transition energy range). Such correlation can be exploited for spin-flip control in a Λ-type three-level system, which manifests itself as an all-optical spin echo in nonlinear optics with two orders of optical fields saved as compared with stimulated Raman processes. This finding represents a class of optical nonlinearity induced by electromagnetic vacuum fluctuations.

  5. Coherent Control in the Presence of Intrinsic Decoherence: Proton Transfer in Large Molecular Systems

    NASA Astrophysics Data System (ADS)

    Batista, Victor S.; Brumer, Paul

    2002-09-01

    An efficient semiclassical approach is developed and used to calculate the coherent-control map and time dependent decoherence measure for the excited-state proton transfer dynamics associated with the keto-enolic tautomerization reaction of 2-(2'-hydroxyphenyl)-oxazole. The method extends the usual bichromatic coherent-control scenario to simulate control at finite times after photoexcitation of the system. Extensive coherent control is demonstrated in a large molecule despite the ultrafast decoherence phenomena, providing results of broad theoretical and experimental interest.

  6. Coherent atomic soliton molecules for matter-wave switching

    SciTech Connect

    Yin, Chenyun; Berloff, Natalia G.; Perez-Garcia, Victor M.; Novoa, David; Carpentier, Alicia V.; Michinel, Humberto

    2011-05-15

    We discuss the dynamics of interacting dark-bright two-dimensional vector solitons in multicomponent immiscible bulk Bose-Einstein condensates. We describe matter-wave molecules without a scalar counterpart that can be seen as bound states of vector objects. We also analyze the possibility of using these structures as building blocks for the design of matter-wave switchers.

  7. Generation of stochastic electromagnetic beams with complete controllable coherence.

    PubMed

    Chen, Xudong; Chang, Chengcheng; Chen, Ziyang; Lin, Zhili; Pu, Jixiong

    2016-09-19

    We generate a stochastic electromagnetic beam (SEB) with complete controllable coherence, that is, the coherence degree can be controlled independently along two mutually perpendicular directions. We control the coherence of the SEB by adjusting the phase modulation magnitude applied onto two crossed phase only spatial light modulators. We measure the beam's coherence properties using Young's interference experiment, as well as the beam propagation factor. It is shown that the experimental results are consistent with our theoretical predictions.

  8. Shaped and Feedback-Controlled Excitation of Single Molecules in the Weak-Field Limit

    PubMed Central

    2015-01-01

    Coherent control uses tailored femtosecond pulse shapes to influence quantum pathways and drive a light-induced process toward a specific outcome. There has been a long-standing debate whether the absorption properties or the probability for population to remain in an excited state of a molecule can be influenced by the pulse shape, even if only a single photon is absorbed. Most such experiments are performed on many molecules simultaneously, so that ensemble averaging reduces the access to quantum effects. Here, we demonstrate systematic coherent control experiments on the fluorescence intensity of a single molecule in the weak-field limit. We demonstrate that a delay scan of interfering pulses reproduces the excitation spectrum of the molecule upon Fourier transformation, but that the spectral phase of a pulse sequence does not affect the transition probability. We generalize this result to arbitrary pulse shapes by performing the first closed-loop coherent control experiments on a single molecule. PMID:26706166

  9. Feshbach-Resonance-Enhanced Coherent Atom-Molecule Conversion with Ultranarrow Photoassociation Resonance

    NASA Astrophysics Data System (ADS)

    Taie, Shintaro; Watanabe, Shunsuke; Ichinose, Tomohiro; Takahashi, Yoshiro

    2016-01-01

    We reveal the existence of high-density Feshbach resonances in the collision between the ground and metastable states of 171Yb and coherently produce the associated Feshbach molecules by photoassociation. The extremely small transition rate is overcome by the enhanced Franck-Condon factor of the weakly bound Feshbach molecule, allowing us to observe Rabi oscillations with long decay time between an atom pair and a molecule in an optical lattice. We also perform the precision measurement of the binding energies, which characterizes the observed resonances. The ultranarrow photoassociation will be a basis for practical implementation of optical Feshbach resonances.

  10. Decoherence Control by Tracking a Hamiltonian Reference Molecule

    SciTech Connect

    Katz, Gil; Ratner, Mark A.; Kosloff, Ronnie

    2007-05-18

    A molecular system in contact with a bath undergoes strong decoherence processes. We examine a control scheme to minimize dissipation, while maximally retaining coherent evolution, by relating the evolution of the molecule to that of an identical freely propagating system. We seek a driving field that maximizes the projection of the open molecular system onto the freely propagated one. The evolution in time of a molecular system consisting of two nonadiabatically coupled electronic states interacting with a bath is followed. The driving control field that overcomes the decoherence is calculated. A proposition to implement the scheme in the laboratory using feedback control is suggested.

  11. Coherence control of pulse trains by spectral phase modulation

    NASA Astrophysics Data System (ADS)

    Ding, Chaoliang; Koivurova, Matias; Turunen, Jari; Setälä, Tero; Friberg, Ari T.

    2017-09-01

    We propose a technique to control the spectral and temporal coherence properties of pulsed beams of light via time-dependent manipulation of the spectral phase. Modulation schemes for the generation of partially coherent pulse trains from a train of fully coherent pulses are presented. The feasibility of experimental realization of the method is confirmed by numerical estimates.

  12. Coherent Radiative Control of Chemical Reactions

    DTIC Science & Technology

    1992-01-01

    effective were determined and successful control was displayed using a model of Stilbene isomerization. F. Control over Chemically Distinct Products...than, the stilbene molecule for which Si(t>to) = Ia(to)Il14ru-(I’ f = 1, II11 (3) there is a vast array of data available art for which...mechanical o calculation of ground and first excited electronic potential surfaces _o for trans- and cis- stilbene . To minimize computational cost we 0

  13. Electronic control inside a molecule : towards single molecule devices

    NASA Astrophysics Data System (ADS)

    Lastapis, Mathieu; Fukuma, Yurie; Boland, John

    2006-03-01

    The chimerical single molecule engineering has been proven to be accessible through the use of scanning tunnelling microscopy (STM) [1]. In this field, one particularly attractive area is the study of single molecules adsorbed on semiconductor surfaces. It has been recently demonstrated that a spatial fine control of the molecular dynamics is possible through the use of tunnelling current [2]. In order to improve the electronic control of a single molecule, we are currently investigating a promising system: CaF2 on Si(111). This system has been extensively studied as a model system to deposit insulator on silicon. Here we are using this system to electronically decouple the molecule from the substrate. I will present LT STM experiments on atomically thick CaF islands on Si(111). The measured electronic properties of these islands demonstrate their potential as ideal templates to study single molecules. Finally I will present some preliminary results on N-HBC [3] adsorbed on a CaF island. [1] G. Binnig and H. Rohrer, ``In touch with atoms'', Rev. Mod. Phys. 71, S324-S330 (1999) [2] M. Lastapis et al, Science, 308, 1000 (2005) [3] S.Draper et al, JACS, 126, 8694 (2004)

  14. Orienting molecules via an ir and uv pulse pair: Implications for coherent Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Sokolov, Alexei V.; Lehmann, Kevin K.; Scully, Marlan O.; Herschbach, Dudley

    2009-05-01

    Spatial orientation of molecules is a pervasive issue in chemical physics and, by breaking inversion symmetry, has major consequences in nonlinear optics. In this paper, we propose and analyze an approach to molecular orientation. This extracts from an ensemble of aligned diatomic molecules (equally AB and BA , relative to the E vector) a subensemble that is oriented (mostly AB or BA ). Subjecting an aligned molecule to a tailored infrared (ir) laser pulse creates a pair of coherent wave packets that correlate vibrational phase with the AB or BA orientation. Subsequent, suitably phased ultraviolet (uv) or visible pulses dissociate one of these vibrational wave packets, thereby “weeding out” either AB or BA but leaving intact the other orientation. Molecular orientation has significant implications for coherent Raman spectroscopy. In the absence of orientation, coherence between vibrational levels is generated by a pair of laser pulses off which a probe pulse is scattered to produce a signal. Orientation allows direct one-photon ir excitation to achieve (in principle) maximal Raman coherence.

  15. Coherent confinement of plasmonic field in quantum dot-metallic nanoparticle molecules

    NASA Astrophysics Data System (ADS)

    Sadeghi, S. M.; Hatef, A.; Fortin-Deschenes, Simon; Meunier, Michel

    2013-05-01

    Interaction of a hybrid system consisting of a semiconductor quantum dot and a metallic nanoparticle (MNP) with a laser beam can replace the intrinsic plasmonic field of the MNP with a coherently normalized field (coherent-plasmonic or CP field). In this paper we show how quantum coherence effects in such a hybrid system can form a coherent barrier (quantum cage) that spatially confines the CP field. This allows us to coherently control the modal volume of this field, making it significantly smaller or larger than that of the intrinsic plasmonic field of the MNP. We investigate the spatial profiles of the CP field and discuss how the field barrier depends on the collective states of the hybrid system.

  16. Coherent confinement of plasmonic field in quantum dot-metallic nanoparticle molecules.

    PubMed

    Sadeghi, S M; Hatef, A; Fortin-Deschenes, Simon; Meunier, Michel

    2013-05-24

    Interaction of a hybrid system consisting of a semiconductor quantum dot and a metallic nanoparticle (MNP) with a laser beam can replace the intrinsic plasmonic field of the MNP with a coherently normalized field (coherent-plasmonic or CP field). In this paper we show how quantum coherence effects in such a hybrid system can form a coherent barrier (quantum cage) that spatially confines the CP field. This allows us to coherently control the modal volume of this field, making it significantly smaller or larger than that of the intrinsic plasmonic field of the MNP. We investigate the spatial profiles of the CP field and discuss how the field barrier depends on the collective states of the hybrid system.

  17. Long-lived Electronic Coherence of Rydberg States in the Strong-Field Ionization of a Polyatomic Molecule

    NASA Astrophysics Data System (ADS)

    Konar, Arkaprabha; Shu, Yinan; Levine, Benjamin; Lozovoy, Vadim; Dantus, Marcos

    2015-05-01

    Here, we report on quantum coherent control of a large (>20 atoms) polyatomic molecule. In particular, we explore the time resolved dynamics of dicyclopentadiene when excited by a pair of phase-locked intense 800nm femtosecond pulses by monitoring changes in ion yield of the parent and fragments. Long-lived oscillations are observed for ~ 500 fs in the parent ion yield indicating the presence of long lived-electronic states. We take advantage of the long-lived electronic coherence to control the yield of different fragment ions. The presence of Rydberg states is further supported by ab initio calculations at the EOM-CCSD/6-31 +G** level of theory which identified five low-lying electronic states of neutral DCPD in the regions between 6.4 and 7.0 eV in vertical excitation energy. States of both pure Rydberg and mixed π --> π */Rydberg character are observed in this low energy region and are known to originate from ethylene. The multiphoton excitation of two or more Rydberg states, separated by the photon energy is the key to the observed long-lived electronic coherence in DCPD with a quantum beat at the difference frequency. Rydberg states are expected to have very similar potential energy surfaces and the Rydberg electron is relatively uncoupled to the nuclear dynamics, therefore supporting long electronic coherence time.

  18. Coherent Population Transfer in Chiral Molecules Using Tailored Microwave Pulses

    NASA Astrophysics Data System (ADS)

    Perez, Cristobal; Steber, Amanda; Domingos, Sergio R.; Krin, Anna; Schmitz, David; Schnell, Melanie

    2017-06-01

    Over the last years, microwave three-wave mixing (M3WM) experiments have been shown to provide a sensitive way to generate and measure enantiomer-specific molecular responses. These experiments opened the door for enantiomeric excess determination in complex samples without previous separation or purification. We present here a new type of experiment, based on M3WM, to achieve enantiomeric enrichment of a chiral sample by using microwave pulses. We will show that control over the relative phases and polarizations of pulses provides a way to selectively populate a specific quantum rotational state with an enantiomer of choice. The experimental implementation as well as the characterization of the observed enantiomer-selective responses will be presented and discussed. As a proof of concept and to showcase the applicability of our approach we will present the enantiomer enrichment of several terpenes. Sandra Eibenberger, John Doyle, and David Patterson, arXiv:1608.04691 (2016)

  19. Model of the photoexcitation processes of a two-level molecule coherently coupled to an optical antenna.

    PubMed

    Nakatani, Masatoshi; Nobuhiro, Atsushi; Yokoshi, Nobuhiko; Ishihara, Hajime

    2013-06-07

    We theoretically investigate photoexcitation processes of a two-level molecular system coherently coupled with an antenna system having a significant dissipation. The auxiliary antenna enables the whole system to exhibit anomalous optical effects by controlling the coupling with the molecule. For example, in the weak excitation regime, the quantum interference yields a distinctive energy transparency through the antenna, which drastically reduces the energy dissipation. On the other hand, in the strong excitation regime, a population inversion of the two-level molecule appears due to the nonlinear effect. Both phenomena can be explained by regarding the antenna and molecule as one quantum-mechanically coupled system. Such an approach drives further research to exploit the full potential of the coupled systems.

  20. Application of coherent Rayleigh-Brillouin scattering for in situ nanoparticle and large molecule detection

    NASA Astrophysics Data System (ADS)

    Shneider, M. N.; Gimelshein, S. F.

    2013-04-01

    Feasibility of using coherent Rayleigh-Brillouin scattering for nanoparticle and large molecule diagnostics is assessed analytically and numerically through the solution of the Boltzmann equation. It has been shown that for particles of about 1 nm in diameter dispersed in a buffer gas, concentrations as small as 0.005% may be detected. The approach is expected to provide information on particle concentration with high spatial and temporal resolution.

  1. Remarkably enhanced adhesion of coherently aligned catechol-terminated molecules on ultraclean ultraflat gold nanoplates.

    PubMed

    Lee, Miyeon; Park, Changjun; Lee, Hyoban; Kim, Hongki; Kim, Sang Youl; In, Insik; Kim, Bongsoo

    2016-11-25

    We report the characterization and formation of catechol-terminated molecules immobilized on gold nanoplates (Au NPLs) using N-(3,4-dihydroxyphenethyl)-2-mercaptoacetamide (Cat-EAA-SH). Single-crystalline Au NPLs, synthesized using a one-step chemical vapor transport method, have ultraclean and ultraflat surfaces that make Cat-EAA-SH molecules aligned into a well-ordered network of a large-scale. Topographic study of the catechol-terminated molecules on Au NPLs using atomic force microscopy showed more orderly orientation and higher density, leading to significantly higher adhesion as observed from local force-distance curves than those on other Au surfaces. These coherently aligned catechol-terminated molecules on the atomically smooth gold surface led to significanty more reproducible and thus more physico-chemically meaningful measurements than was possible before by employing rough gold surfaces.

  2. Remarkably enhanced adhesion of coherently aligned catechol-terminated molecules on ultraclean ultraflat gold nanoplates

    NASA Astrophysics Data System (ADS)

    Lee, Miyeon; Park, Changjun; Lee, Hyoban; Kim, Hongki; Kim, Sang Youl; In, Insik; Kim, Bongsoo

    2016-11-01

    We report the characterization and formation of catechol-terminated molecules immobilized on gold nanoplates (Au NPLs) using N-(3,4-dihydroxyphenethyl)-2-mercaptoacetamide (Cat-EAA-SH). Single-crystalline Au NPLs, synthesized using a one-step chemical vapor transport method, have ultraclean and ultraflat surfaces that make Cat-EAA-SH molecules aligned into a well-ordered network of a large-scale. Topographic study of the catechol-terminated molecules on Au NPLs using atomic force microscopy showed more orderly orientation and higher density, leading to significantly higher adhesion as observed from local force-distance curves than those on other Au surfaces. These coherently aligned catechol-terminated molecules on the atomically smooth gold surface led to significanty more reproducible and thus more physico-chemically meaningful measurements than was possible before by employing rough gold surfaces.

  3. Fundamental Principles of Coherent-Feedback Quantum Control

    DTIC Science & Technology

    2014-12-08

    AFRL-OSR-VA-TR-2015-0009 FUNDAMENTAL PRINCIPLES OF COHERENT- FEEDBACK QUANTUM CONTROL Hideo Mabuchi LELAND STANFORD JUNIOR UNIV CA Final Report 12/08...foundations and potential applications of coherent- feedback quantum control. We have focused on potential applications in quantum-enhanced metrology and...picture of how coherent feedback can provide a kind of circuit/network theory for quantum engineering, enabling rigorous analysis and numerical simulation

  4. Certifying the quantumness of a generalized coherent control scenario

    SciTech Connect

    Scholak, Torsten Brumer, Paul

    2014-11-28

    We consider the role of quantum mechanics in a specific coherent control scenario, designing a “coherent control interferometer” as the essential tool that links coherent control to quantum fundamentals. Building upon this allows us to rigorously display the genuinely quantum nature of a generalized weak-field coherent control scenario (utilizing 1 vs. 2 photon excitation) via a Bell-CHSH test. Specifically, we propose an implementation of “quantum delayed-choice” in a bichromatic alkali atom photoionization experiment. The experimenter can choose between two complementary situations, which are characterized by a random photoelectron spin polarization with particle-like behavior on the one hand, and by spin controllability and wave-like nature on the other. Because these two choices are conditioned coherently on states of the driving fields, it becomes physically unknowable, prior to measurement, whether there is control over the spin or not.

  5. Coherent control of plasmons in nanoparticles with nonlocal response

    NASA Astrophysics Data System (ADS)

    McArthur, D.; Hourahine, B.; Papoff, F.

    2017-01-01

    We discuss a scheme for the coherent control of light and plasmons in nanoparticles that have nonlocal dielectric permittivity and contain nonlinear impurities or color centers. We consider particles which have a response to light that is strongly influenced by plasmons over a broad range of frequencies. Our coherent control method enables the reduction of absorption and/or suppression of scattering.

  6. Controlling coherent state superpositions with superconducting circuits

    NASA Astrophysics Data System (ADS)

    Vlastakis, Brian Michael

    Quantum computation requires a large yet controllable Hilbert space. While many implementations use discrete quantum variables such as the energy states of a two-level system to encode quantum information, continuous variables could allow access to a larger computational space while minimizing the amount of re- quired hardware. With a toolset of conditional qubit-photon logic, we encode quantum information into the amplitude and phase of coherent state superpositions in a resonator, also known as Schrddinger cat states. We achieve this using a superconducting transmon qubit with a strong off-resonant coupling to a waveguide cavity. This dispersive interaction is much greater than decoherence rates and higher-order nonlinearites and therefore allows for simultaneous control of over one hundred photons. Furthermore, we combine this experiment with fast, high-fidelity qubit state readout to perform composite qubit-cavity state tomography and detect entanglement between a physical qubit and a cat-state encoded qubit. These results have promising applications for redundant encoding in a cavity state and ultimately quantum error correction with superconducting circuits.

  7. Control over group velocity in a three-level closed Λ system via spontaneously generated coherence and dynamically induced coherence

    NASA Astrophysics Data System (ADS)

    Dutta, Sulagna; Dastidar, Krishna Rai

    2007-11-01

    The light propagation of a probe field in a three-level Λ system with incoherent pumping has been studied when both dynamically induced coherence (DIC) and spontaneously generated coherence (SGC) play a significant role. We have investigated the group velocity of probe field and hence the group index of a three-level Λ system with incoherent pumping when both DIC and SGC play a significant role. We have shown that by varying the probe field Rabi frequency one can control the interference between these two coherences which leads to different nonlinear response (amplification without inversion, electromagnetically induced transparency and electromagnetically induced absorption) leading to different (positive and negative) dispersion. Hence control over switching of group velocity from subluminal to superluminal and vice versa can be achieved. We have also shown that when the contributions from both the coherences are comparable, the dependence of group velocity of probe field in a three-level Λ system with incoherent pumping on phase difference between probe and coherent fields is different from that obtained under the weak probe field condition. Going beyond the weak probe field approximation we have derived analytical expressions for group velocity and hence the group index in the steady state limit (keeping all orders of system parameters) to generalize the analysis, and these expressions can be used for any set of system parameters without any restriction. The numerical values obtained by solving the density matrix equations agree well with these exact analytical values at a large time limit. We have proposed a scheme for experimental realization of EIT and hence subluminal light propagation in molecules by invoking spontaneously generated coherence.

  8. How organic molecules can control electronic devices.

    PubMed

    Vilan, Ayelet; Cahen, David

    2002-01-01

    This article examines a somewhat counter-intuitive approach to molecular-based electronic devices. Control over the electronic energy levels at the surfaces of conventional semiconductors and metals is achieved by assembling on the solid surfaces, poorly organized, partial monolayers (MLs) of molecules instead of the more commonly used ideal ones. Once those surfaces become interfaces, these layers exert electrostatic rather than electrodynamic control over the resulting devices, based on both electrical monopole and dipole effects of the molecules. Thus electronic transport devices, incorporating molecules, can be constructed without current flow through the molecules. This is illustrated for a gallium arsenide (GaAs) sensor as well as for gold-silicon (Au-Si) and Au-GaAs diodes. Incorporating molecules into solid interfaces becomes possible, using a 'soft' electrical contacting procedure, so as not to damage the molecules. Because there are only a few molecular restrictions, this approach opens up possibilities for the use of more complex (including biologically active) molecules as it circumvents requirements for ideal MLs and for molecules that can tolerate actual electron transport through them.

  9. Coherent optical propagation and ultrahigh resolution mass sensor based on photonic molecules optomechanics

    NASA Astrophysics Data System (ADS)

    Chen, Hua-Jun; Chen, Chang-Zhao; Li, Yang; Fang, Xian-Wen; Tang, Xu-Dong

    2017-01-01

    We theoretically demonstrate the coherent optical propagation properties based on a photonic molecules optomechanics. With choosing a suitable detuning of the pump field from optomechanical cavity resonance, both the slow- and fast-light effect of the probe field appear in the system. The coupling strength of the two cavities play a key role, which affords a quantum channel and influences the width of the transparency window. Based on the photonic molecules optomechanical system, a high resolution mass sensor is also proposed. The mass of external nanoparticles deposited onto the cavity can be measured straightforward via tracking the mechanical resonance frequency shifts due to mass changes in the probe transmission spectrum. Compared with the single-cavity optomechanics mass sensors, the mass resolution is improved significantly due to the cavity-cavity coupling. The photonic molecules optomechanics provide a new platform for on-chip applications in quantum information processing and ultrahigh resolution sensor devices.

  10. Ultrafast X-Ray Coherent Control

    SciTech Connect

    Reis, David

    2009-05-01

    This main purpose of this grant was to develop the nascent eld of ultrafast x-ray science using accelerator-based sources, and originally developed from an idea that a laser could modulate the di racting properties of a x-ray di racting crystal on a fast enough time scale to switch out in time a shorter slice from the already short x-ray pulses from a synchrotron. The research was carried out primarily at the Advanced Photon Source (APS) sector 7 at Argonne National Laboratory and the Sub-Picosecond Pulse Source (SPPS) at SLAC; in anticipation of the Linac Coherent Light Source (LCLS) x-ray free electron laser that became operational in 2009 at SLAC (all National User Facilities operated by BES). The research centered on the generation, control and measurement of atomic-scale dynamics in atomic, molecular optical and condensed matter systems with temporal and spatial resolution . It helped develop the ultrafast physics, techniques and scienti c case for using the unprecedented characteristics of the LCLS. The project has been very successful with results have been disseminated widely and in top journals, have been well cited in the eld, and have laid the foundation for many experiments being performed on the LCLS, the world's rst hard x-ray free electron laser.

  11. Dynamics and control of coherent structure in turbulent jets

    NASA Technical Reports Server (NTRS)

    Mankbadi, Reda R.

    1992-01-01

    Current understanding of coherent structure dynamics in incompressible turbulent jets as explained by the nonlinear stability theory is reviewed, focusing on nonswirling turbulent jets. Topics addressed include hydrodynamic stability theory and coherent structures; dynamics of energy transfers among different scales of motion; nonlinear development of amplitude; development of single-frequency coherent mode; fundamental-subharmonic interaction and vortex pairing; and reversal of Reynolds stresses. Attention is also given to the effect of initial phase-difference angle between fundamental and subharmonic, conditions for resonance interaction, modulation of spreading rate by controlling coherent structure, turbulence enhancement or suppression due to excitation, 3D effects, jet noise, and swirling jets.

  12. Spin coherence in a Mn{sub 3} single-molecule magnet

    SciTech Connect

    Abeywardana, Chathuranga; Mowson, Andrew M.; Christou, George; Takahashi, Susumu

    2016-01-25

    Spin coherence in single crystals of the spin S = 6 single-molecule magnet (SMM) [Mn{sub 3}O(O{sub 2}CEt){sub 3}(mpko){sub 3}]{sup +} (abbreviated Mn{sub 3}) has been investigated using 230 GHz electron paramagnetic resonance spectroscopy. Coherence in Mn{sub 3} was uncovered by significantly suppressing dipolar contribution to the decoherence with complete spin polarization of Mn{sub 3} SMMs. The temperature dependence of spin decoherence time (T{sub 2}) revealed that the dipolar decoherence is the dominant source of decoherence in Mn{sub 3} and T{sub 2} can be extended up to 267 ns by quenching the dipolar decoherence.

  13. Coherence in the presence of absorption and heating in a molecule interferometer.

    PubMed

    Cotter, J P; Eibenberger, S; Mairhofer, L; Cheng, X; Asenbaum, P; Arndt, M; Walter, K; Nimmrichter, S; Hornberger, K

    2015-06-11

    Matter-wave interferometry can be used to probe the foundations of physics and to enable precise measurements of particle properties and fundamental constants. It relies on beam splitters that coherently divide the wave function. In atom interferometers, such elements are often realised using lasers by exploiting the dipole interaction or through photon absorption. It is intriguing to extend these ideas to complex molecules where the energy of an absorbed photon can rapidly be redistributed across many internal degrees of freedom. Here, we provide evidence that center-of-mass coherence can be maintained even when the internal energy and entropy of the interfering particle are substantially increased by absorption of photons from a standing light wave. Each photon correlates the molecular center-of-mass wave function with its internal temperature and splits it into a superposition with opposite momenta in addition to the beam-splitting action of the optical dipole potential.

  14. Coherence in the presence of absorption and heating in a molecule interferometer

    PubMed Central

    Cotter, J. P.; Eibenberger, S.; Mairhofer, L.; Cheng, X.; Asenbaum, P.; Arndt, M.; Walter, K.; Nimmrichter, S.; Hornberger, K.

    2015-01-01

    Matter-wave interferometry can be used to probe the foundations of physics and to enable precise measurements of particle properties and fundamental constants. It relies on beam splitters that coherently divide the wave function. In atom interferometers, such elements are often realised using lasers by exploiting the dipole interaction or through photon absorption. It is intriguing to extend these ideas to complex molecules where the energy of an absorbed photon can rapidly be redistributed across many internal degrees of freedom. Here, we provide evidence that center-of-mass coherence can be maintained even when the internal energy and entropy of the interfering particle are substantially increased by absorption of photons from a standing light wave. Each photon correlates the molecular center-of-mass wave function with its internal temperature and splits it into a superposition with opposite momenta in addition to the beam-splitting action of the optical dipole potential. PMID:26066053

  15. Interference-free coherence dynamics of gas-phase molecules using spectral focusing.

    PubMed

    Wrzesinski, Paul J; Roy, Sukesh; Gord, James R

    2012-10-08

    Spectral focusing using broadband femtosecond pulses to achieve highly selective measurements has been employed for numerous applications in spectroscopy and microspectroscopy. In this work we highlight the use of spectral focusing for selective excitation and detection of gas-phase species. Furthermore, we demonstrate that spectral focusing, coupled with time-resolved measurements based upon probe delay, allows the observation of interference-free coherence dynamics of multiple molecules and gas-phase temperature making this technique ideal for gas-phase measurements of reacting flows and combustion processes.

  16. Molecule-surface interactions probed by optimized surface-enhanced coherent Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Voronine, Dmitri; Sinyukov, Alexander; Hua, Xia; Zhang, Guowan; Yang, Wenlong; Wang, Kai; Jha, Pankaj; Welch, George; Sokolov, Alexei; Scully, Marlan

    2012-06-01

    Nanoscale molecular sensing is carried out using a time-resolved coherent anti-Stokes Raman scattering (CARS) spectroscopy with optimized laser pulse configurations. This novel technique combines the advantages of an improved spectral resolution, suppressed non-resonant background and near-field surface enhancement of the Raman signal. We detect two species of pyridine in a vicinity of aggregated gold nanoparticles and measure their vibrational dephasing times which reveal the effects of surface environment and molecule-surface interactions on the ultrafast molecular dynamics. This technique may be applied to a variety of artificial and biological systems and complex molecular mixtures and has a potential for nanophotonic sensing applications.

  17. Development of ultrahigh-precision coherent control and its applications

    PubMed Central

    Ohmori, Kenji

    2008-01-01

    Coherent control is based on optical manipulation of the amplitudes and phases of wave functions. It is expected to be a key technique to develop novel quantum technologies such as bond-selective chemistry and quantum computing, and to better understand the quantum worldview founded on wave-particle duality. We have developed high-precision coherent control by imprinting optical amplitudes and phases of ultrashort laser pulses on the quantum amplitudes and phases of molecular wave functions. The history and perspective of coherent control and our recent achievements are described. PMID:18941296

  18. Controlling polar molecules in optical lattices

    SciTech Connect

    Kotochigova, S.; Tiesinga, E.

    2006-04-15

    We theoretically investigate the interaction of polar molecules with optical lattices and microwave fields. We demonstrate the existence of frequency windows in the optical domain where the complex internal structure of the molecule does not influence the trapping potential of the lattice. In such frequency windows the Franck-Condon factors are so small that near-resonant interaction of vibrational levels of the molecule with the lattice fields have a negligible contribution to the polarizability, and light-induced decoherences are kept to a minimum. In addition, we show that microwave fields can induce a tunable dipole-dipole interaction between ground-state rotationally symmetric (J=0) molecules. A combination of a carefully chosen lattice frequency and microwave-controlled interaction between molecules will enable trapping of polar molecules in a lattice and possibly realize molecular quantum logic gates. Our results are based on ab initio relativistic electronic structure calculations of the polar KRb and RbCs molecules combined with calculations of their rovibrational motion.

  19. Simulation of X-ray transient absorption for following vibrations in coherently ionized F2 molecules

    NASA Astrophysics Data System (ADS)

    Dutoi, Anthony D.; Leone, Stephen R.

    2017-01-01

    Femtosecond and attosecond X-ray transient absorption experiments are becoming increasingly sophisticated tools for probing nuclear dynamics. In this work, we explore and develop theoretical tools needed for interpretation of such spectra,in order to characterize the vibrational coherences that result from ionizing a molecule in a strong IR field. Ab initio data for F2 is combined with simulations of nuclear dynamics, in order to simulate time-resolved X-ray absorption spectra for vibrational wavepackets after coherent ionization at 0 K and at finite temperature. Dihalogens pose rather difficult electronic structure problems, and the issues encountered in this work will be reflective of those encountered with any core-valence excitation simulation when a bond is breaking. The simulations reveal a strong dependence of the X-ray absorption maximum on the locations of the vibrational wave packets. A Fourier transform of the simulated signal shows features at the overtone frequencies of both the neutral and the cation, which reflect spatial interferences of the vibrational eigenstates. This provides a direct path for implementing ultrafast X-ray spectroscopic methods to visualize coherent nuclear dynamics.

  20. Coherent Control of Multiphoton Transitions in the Gas and Condensed Phases with Shaped Ultrashort Pulses

    SciTech Connect

    Marcos Dantus

    2008-09-23

    Controlling laser-molecule interactions has become an integral part of developing devices and applications in spectroscopy, microscopy, optical switching, micromachining and photochemistry. Coherent control of multiphoton transitions could bring a significant improvement of these methods. In microscopy, multi-photon transitions are used to activate different contrast agents and suppress background fluorescence; coherent control could generate selective probe excitation. In photochemistry, different dissociative states are accessed through two, three, or more photon transitions; coherent control could be used to select the reaction pathway and therefore the yield-specific products. For micromachining and processing a wide variety of materials, femtosecond lasers are now used routinely. Understanding the interactions between the intense femtosecond pulse and the material could lead to technologically important advances. Pulse shaping could then be used to optimize the desired outcome. The scope of our research program is to develop robust and efficient strategies to control nonlinear laser-matter interactions using ultrashort shaped pulses in gas and condensed phases. Our systematic research has led to significant developments in a number of areas relevant to the AMO Physics group at DOE, among them: generation of ultrashort phase shaped pulses, coherent control and manipulation of quantum mechanical states in gas and condensed phases, behavior of isolated molecules under intense laser fields, behavior of condensed phase matter under intense laser field and implications on micromachining with ultrashort pulses, coherent control of nanoparticles their surface plasmon waves and their nonlinear optical behavior, and observation of coherent Coulomb explosion processes at 10^16 W/cm^2. In all, the research has resulted in 36 publications (five journal covers) and nine invention disclosures, five of which have continued on to patenting

  1. Control of Exciton Valley Coherence in Transition Metal Dichalcogenide Monolayers

    NASA Astrophysics Data System (ADS)

    Wang, G.; Marie, X.; Liu, B. L.; Amand, T.; Robert, C.; Cadiz, F.; Renucci, P.; Urbaszek, B.

    2016-10-01

    The direct gap interband transitions in transition metal dichalcogenide monolayers are governed by chiral optical selection rules. Determined by laser helicity, optical transitions in either the K+ or K- valley in momentum space are induced. Linearly polarized laser excitation prepares a coherent superposition of valley states. Here, we demonstrate the control of the exciton valley coherence in monolayer WSe2 by tuning the applied magnetic field perpendicular to the monolayer plane. We show rotation of this coherent superposition of valley states by angles as large as 30° in applied fields up to 9 T. This exciton valley coherence control on the ps time scale could be an important step towards complete control of qubits based on the valley degree of freedom.

  2. Coherent control of quantum systems as a resource theory

    NASA Astrophysics Data System (ADS)

    Matera, J. M.; Egloff, D.; Killoran, N.; Plenio, M. B.

    2016-08-01

    Control at the interface between the classical and the quantum world is fundamental in quantum physics. In particular, how classical control is enhanced by coherence effects is an important question both from a theoretical as well as from a technological point of view. In this work, we establish a resource theory describing this setting and explore relations to the theory of coherence, entanglement and information processing. Specifically, for the coherent control of quantum systems, the relevant resources of entanglement and coherence are found to be equivalent and closely related to a measure of discord. The results are then applied to the DQC1 protocol and the precision of the final measurement is expressed in terms of the available resources.

  3. Strong Field Coherent Control of Atomic Population Transfer

    NASA Astrophysics Data System (ADS)

    Clow, Stephen; Holscher, Uvo; Trallero, Carlos; Weinacht, Thomas

    2008-05-01

    There is significant interest in controlling atomic and molecular dynamics using shaped ultrafast laser pulses, an important aspect of which is selectively populating a particular target state with high efficiency. In order to achieve this beyond the limits of single photon excitation, one has to consider multiple interfering pathways and dynamic Stark shifts (DSS), which make resonance conditions time-dependent and substantially modify the phase advance of the bare states during the atom/molecule-field interaction. In this work, we demonstrate strong field atomic population transfer in a three level system via three-photon absorption from a single shaped ultrafast laser pulse. The optimal pulse shape for efficient population transfer is discovered using closed-loop learning control and interpreted via pulse shape parameter scans and numerical integration of the Schr"odinger equation. We show a population inversion can be achieved and measured using a combination of spontaneous and stimulated emission. Our results illustrate the importance of dynamic Stark shifts in coherent multi-photon excitation and give rise to the possibility of lasing in the deep ultraviolet.

  4. Coherent Control of Collective Atomic Spins

    NASA Astrophysics Data System (ADS)

    Trail, Collin M.

    2011-12-01

    In this thesis I explore the use of collective spin angular momentum as a platform for quantum information processing. In the limit of a large number of atoms, the collective variables of atomic systems have a natural connection to the bosonic algebra of light (known as the Holstein-Primakoff or HP approximation) where components of the collective spin angular momentum effectively act as quadratures, making them natural systems for coupling to light. I have sought to improve previous schemes for the spin squeezing of atomic ensembles, such as the proposal of Takeuchi et. al. based on coherent quantum feedback [39]. In this scheme a beam of linearly polarized light passes through the atomic ensemble (prepared in a coherent state), coupling to the atoms through a state-dependent index of refraction (the Faraday effect). The light is then passed through a wave-plate and reflected back through the atoms for a second pass. This double-pass scheme leads to an effective nonlinearity as the atomic fluctuations are mapped onto the light on the first pass and then back on to the atoms in the second pass. The light acts as a bus coupling each atom to each of the others. This nonlinear interaction forms a shearing of the atomic coherent state that results in squeezing. The light is entangled to the atoms through these interactions, and remains entangled as it escapes the system. This leads to decoherence of the atoms as the light is lost to the environment, reducing the amount of spin squeezing achieved. The first step towards improving the double-pass scheme was to add a quantum eraser step in which the light is disentangled from the squeezed atoms. By first measuring one quadrature of the light, and then performing a measurement-dependent rotation on the atomic ensemble, it is possible to decouple the atoms and light so that the loss of the light does not reduce the atomic squeezing. This results in an improvement of the rate of atomic spin squeezing. A complete model

  5. Control of dephasing in rotationally hot molecules

    NASA Astrophysics Data System (ADS)

    Bartram, David; Ivanov, Misha

    2010-04-01

    We consider a rotationally hot diatomic molecule as an example of an open quantum system, where molecular vibrational wave packets are subject to dephasing due to rovibrational coupling. We report analytical and numerical results addressing whether the dephasing rate can be controlled by adjustment of the initial wave packet phases. It appears that over long time scales, phase-only control is not possible, but for earlier time scales the possibility of phase-only control of dephasing remains. In addition, we point out that the time dependence of the dephasing process depends significantly upon the degeneracy of the rotational environment states.

  6. Stimulus control topography coherence theory: Foundations and extensions

    PubMed Central

    McIlvane, William J.; Dube, William V.

    2003-01-01

    Stimulus control topography refers to qualitative differences among members of a functional stimulus class. Stimulus control topography coherence refers to the degree of concordance between the stimulus properties specified as relevant by the individual arranging a reinforcement contingency (behavior analyst, experimenter, teacher, etc.) and the stimulus properties that come to control the behavior of the organism (experimental subject, student, etc.) that experiences those contingencies. This paper summarizes the rationale for analyses of discrimination learning outcomes in terms of stimulus control topography coherence and briefly reviews some of the foundational studies that led to this perspective. We also suggest directions for future research, including pursuit of conceptual and methodological challenges to a complete stimulus control topography coherence analysis of processes involved in discriminated and generalized operants. ImagesFigure 3Figure 5 PMID:22478402

  7. Stimulus control topography coherence theory: foundations and extensions.

    PubMed

    McIlvane, William J; Dube, William V

    2003-01-01

    Stimulus control topography refers to qualitative differences among members of a functional stimulus class. Stimulus control topography coherence refers to the degree of concordance between the stimulus properties specified as relevant by the individual arranging a reinforcement contingency (behavior analyst, experimenter, teacher, etc.) and the stimulus properties that come to control the behavior of the organism (experimental subject, student, etc.) that experiences those contingencies. This paper summarizes the rationale for analyses of discrimination learning outcomes in terms of stimulus control topography coherence and briefly reviews some of the foundational studies that led to this perspective. We also suggest directions for future research, including pursuit of conceptual and methodological challenges to a complete stimulus control topography coherence analysis of processes involved in discriminated and generalized operants.

  8. Controlling quantum transport through a single molecule.

    PubMed

    Cardamone, David M; Stafford, Charles A; Mazumdar, Sumit

    2006-11-01

    We investigate multiterminal quantum transport through single monocyclic aromatic annulene molecules, and their derivatives, using the nonequilibrium Green function approach within the self-consistent Hartree-Fock approximation. We propose a new device concept, the quantum interference effect transistor, that exploits perfect destructive interference stemming from molecular symmetry and controls current flow by introducing decoherence and/or elastic scattering that break the symmetry. This approach overcomes the fundamental problems of power dissipation and environmental sensitivity that beset nanoscale device proposals.

  9. Coherent control with qudit photon states

    NASA Astrophysics Data System (ADS)

    Rodrigues, I.; Cosme, O.; Pádua, S.

    2010-06-01

    In this paper the two-photon absorption by a molecule is studied when photons are prepared in a high-dimension entangled state. The light field is prepared in a spatial two-photon qudit state and its interaction with a molecule shows new interference effects observed in the calculated absorption cross-section. Oscillations in the absorption cross-section demonstrate its dependence on the path phases of the two-qudit state. The two-photon absorption cross-section is dependent on the dimension of the two-qudit photonic state.

  10. Coherent electron emission beyond Young-type interference from diatomic molecules

    NASA Astrophysics Data System (ADS)

    Agueny, H.; Makhoute, A.; Dubois, A.; Hansen, J. P.

    2016-01-01

    It has been known for more than 15 years that the differential cross section of electrons emitted from diatomic molecules during interaction with energetic charged particles oscillates as a function of electron momentum. The origin of the phenomenon is two-center interference, which naturally relates it back to the Young double-slit experiment. In addition to a characteristic frequency which can be described by lowest-order perturbation theories, the observation and origin of higher-order harmonics of the basic oscillation frequency has been much discussed. Here, we show that high harmonics of the fundamental Young-type oscillation frequency observed in electron spectra in fast ion-molecule collisions can be clearly exposed in numerical solutions of the time-dependent Schrödinger equation within a one-dimensional model. Momentum distribution of the ejected electron is analyzed and shows that the phenomenon emerges when the charged particle beam collides with diatomic molecules with substantial large internuclear distance. Frequency spectra from nonperturbative calculations for electron emission from Rb2+ and Cs2+ exhibit a pronounced high-order oscillation in contrast to similar close-coupling calculations performed on H2 targets. The electron emission from these heavy molecules contains second- and third-order harmonics which are fully reproduced in an analytic model based on the Born series. Extending to triatomic molecular targets displays an increased range of harmonics. This suggests that electron emission spectra from new experiments on heavy diatomic and linear polyatomic molecular targets may provide a unique insight into competing coherent emission mechanisms and their relative strength.

  11. Molecular alignment using coherent resonant excitation: A new proposal for stereodynamic control of chemical reactions.

    PubMed

    Mukherjee, Nandini

    2009-10-28

    For the mode-selective control of chemical reaction, we present a new approach of molecular alignment using coherent resonant interaction with low intensity midinfrared optical pulses. Under coherent excitation, the alignment of vibrationally excited molecules becomes a function of the optical pulse area. Depending on the type of transition, with certain values of the pulse areas, a narrow group of magnetic substates are selectively excited, which results in aligning the rotational axis of the molecular ensemble. It is shown that for a P-type transition, significant alignment in the excited vibrational state can be realized using a resonant midinfrared pulse of area approximately 2pi. Under the steady state excitation (pulse duration longer than the vibrational relaxation time), the molecular alignment is destroyed due to saturation. We design a polarization spectroscopy experiment to coherently excite and probe the molecular alignment in real time.

  12. Theory of perturbative pulse train based coherent control

    NASA Astrophysics Data System (ADS)

    Grinev, Timur; Brumer, Paul

    2014-03-01

    A theoretical description of coherent control of excited state dynamics using pulse trains in the perturbative regime, as carried out in recent experiments, is presented. Analytical expressions relating the excited state populations to the pulse train control parameters are derived. Numerical examples are provided for models of pyrazine and β-carotene, and the significant role of overlapping resonances is exposed.

  13. Wavefront manipulation with a dipolar metasurface under coherent control

    NASA Astrophysics Data System (ADS)

    Kang, Ming; Wang, Hui-Tian; Zhu, Weiren

    2017-07-01

    Full phase manipulation with equal amplitude is critical for optical wavefront engineering in various systems. Here we theoretically explore a general approach for optical wavefront manipulation using dipolar metasurfaces under the coherent control. From the microscopic perspective, we theoretically show that the dispersion of a dipolar metasurface under the coherent control can provide the phase manipulation within a full range of [0, 2π] and retain an equal amplitude simultaneously. As an example, such a dipolar metasurface can be constructed by compensatory H-shaped unit resonators to avoid polarization conversion. Specifically, we confirm the feasibility of designed metasurfaces for achieving the beam bending and the vortex-phase beam by the full-wave simulation. The proposed approach enriches the well-established wavefront engineering for extending the functionality of metasurface under the coherent control.

  14. Coherent control of optical polarization effects in metamaterials

    PubMed Central

    Mousavi, Seyedmohammad A.; Plum, Eric; Shi, Jinhui; Zheludev, Nikolay I.

    2015-01-01

    Processing of photonic information usually relies on electronics. Aiming to avoid the conversion between photonic and electronic signals, modulation of light with light based on optical nonlinearity has become a major research field and coherent optical effects on the nanoscale are emerging as new means of handling and distributing signals. Here we demonstrate that in slabs of linear material of sub-wavelength thickness optical manifestations of birefringence and optical activity (linear and circular birefringence and dichroism) can be controlled by a wave coherent with the wave probing the polarization effect. We demonstrate this in proof-of-principle experiments for chiral and anisotropic microwave metamaterials, where we show that the large parameter space of polarization characteristics may be accessed at will by coherent control. Such control can be exerted at arbitrarily low intensities, thus arguably allowing for fast handling of electromagnetic signals without facing thermal management and energy challenges. PMID:25755071

  15. Coherent control using kinetic energy and the geometric phase of a conical intersection

    NASA Astrophysics Data System (ADS)

    Liekhus-Schmaltz, Chelsea; McCracken, Gregory A.; Kaldun, Andreas; Cryan, James P.; Bucksbaum, Philip H.

    2016-10-01

    Conical intersections (CIs) between molecular potential energy surfaces with non-vanishing non-adiabatic couplings generally occur in any molecule consisting of at least three atoms. They play a fundamental role in describing the molecular dynamics beyond the Born-Oppenheimer approximation and have been used to understand a large variety of effects, from photofragmentation and isomerization to more exotic applications such as exciton fission in semiconductors. However, few studies have used the features of a CI as a tool for coherent control. Here we demonstrate two modes of control around a conical intersection. The first uses a continuous light field to control the population on the two intersecting electronic states in the vicinity of a CI. The second uses a pulsed light field to control wavepackets that are subjected to the geometric phase shift in transit around a CI. This second technique is likely to be useful for studying the role of nuclear dynamics in electronic coherence phenomena.

  16. Control of coherent backscattering by breaking optical reciprocity

    NASA Astrophysics Data System (ADS)

    Bromberg, Y.; Redding, B.; Popoff, S. M.; Cao, H.

    2016-02-01

    Reciprocity is a universal principle that has a profound impact on many areas of physics. A fundamental phenomenon in condensed-matter physics, optical physics, and acoustics, arising from reciprocity, is the constructive interference of quantum or classical waves which propagate along time-reversed paths in disordered media, leading to, for example, weak localization and metal-insulator transition. Previous studies have shown that such coherent effects are suppressed when reciprocity is broken. Here we experimentally show that by tuning a nonreciprocal phase we can coherently control complex coherent phenomena, rather than simply suppress them. In particular, we manipulate coherent backscattering of light, also known as weak localization. By utilizing a magneto-optical effect, we control the interference between time-reversed paths inside a multimode fiber with strong mode mixing, observe the optical analog of weak antilocalization, and realize a continuous transition from weak localization to weak antilocalization. Our results may open new possibilities for coherent control of waves in complex systems.

  17. Partially dark optical molecule via phase control

    NASA Astrophysics Data System (ADS)

    Wang, Z. H.; Xu, Xun-Wei; Li, Yong

    2017-01-01

    We study the tunable photonic distribution in an optical molecule consisting of two linearly coupled single-mode cavities. With the intercavity coupling and two driving fields, the energy levels of the optical-molecule system form a closed cyclic energy-level diagram, and the phase difference between the driving fields serves as a sensitive controller on the dynamics of the system. Due to the quantum interference effect, we can realize a partially dark optical molecule, where the steady-state mean photon number in one of the cavities achieves zero even under the external driving. And the dark cavity can be changed from one of the cavities to the other by only adjusting the phase difference. We also show that our proposal is robust to the noise at zero temperature. Furthermore, we show that when one of the cavities couples with an atomic ensemble, it will be dark under the same condition as that in the case without atoms, but the condition for the other cavity to be dark is modified.

  18. Ultrafast Coherent Control and Characterization of Surface Reactions using FELs

    SciTech Connect

    Ogasawara, Hirohito; Nordlund, Dennis a Nilsson, Anders; /SLAC, SSRL

    2005-09-30

    The microscopic understanding of reactions at surfaces requires an in-depth knowledge of the dynamics of elementary processes on an ultrafast timescale. This can be accomplished using an ultrafast excitation to initiate a chemical reaction and then probe the progression of the reaction with an ultrashort x-ray pulse from the FEL. There is a great potential to use atom-specific spectroscopy involving core levels to probe the chemical nature, structure and bonding of species on surfaces. The ultrashort electron pulse obtained in the linear accelerator to feed the X-ray FEL can also be used for generation of coherent synchrotron radiation in the low energy THz regime to be used as a pump. This radiation has an energy close to the thermal excitations of low-energy vibrational modes of molecules on surfaces and phonons in substrates. The coherent THz radiation will be an electric field pulse with a certain direction that can collectively manipulate atoms or molecules on surfaces. In this respect a chemical reaction can be initiated by collective atomic motion along a specific reaction coordinate. If the coherent THz radiation is generated from the same source as the X-ray FEL radiation, full-time synchronization for pump-probe experiments will be possible. The combination of THz and X-ray spectroscopy could be a unique opportunity for FEL facilities to conduct ultrafast chemistry studies at surfaces.

  19. Understanding and controlling laser-matter interactions: From solvated dye molecules to polyatomic molecules in gas phase

    NASA Astrophysics Data System (ADS)

    Konar, Arkaprabha

    The goal of my research is to obtain a better understanding of the various processes that occur during and following laser-matter interactions from both the physical and chemical point of view. In particular I focused my research on understanding two very important aspects of laser-matter interaction; 1) Intense laser-matter interactions for polyatomic molecules in the gas phase in order to determine to what extent processes like excitation, ionization and fragmentation can be controlled by modifying the phase and amplitude of the laser field according to the timescales for electronic, vibrational and rotational energy transfer. 2) Developing pulse shaping based single beam methods aimed at studying solvated molecules in order to elucidate processes like inhomogeneous broadening, solvatochromic shift and to determine the electronic coherence lifetimes of solvated molecules. The effect of the chirped femtosecond pulses on fluorescence and stimulated emission from solvated dye molecules was studied and it was observed that the overall effect depends quadratically on pulse energy, even where excitation probabilities range from 0.02 to 5%, in the so-called "linear excitation regime". The shape of the chirp dependence is found to be independent of the energy of the pulse. It was found that the chirp dependence reveals dynamics related to solvent rearrangement following excitation and also depends on electronic relaxation of the chromophore. Furthermore, the chirped pulses were found to be extremely sensitive to solvent environment and that the complementary phases having the opposite sign provide information about the electronic coherence lifetimes. Similar to chirped pulses, the effects of a phase step on the excitation spectrum and the corresponding changes to the stimulated emission spectrum were also studied and it was found that the coherent feature on the spectrum is sensitive to the dephasing time of the system. Therefore a single phase scanning method can

  20. Subfemtosecond directional control of chemical processes in molecules

    NASA Astrophysics Data System (ADS)

    Alnaser, Ali S.; Litvinyuk, Igor V.

    2017-02-01

    Laser pulses with a waveform-controlled electric field and broken inversion symmetry establish the opportunity to achieve directional control of molecular processes on a subfemtosecond timescale. Several techniques could be used to break the inversion symmetry of an electric field. The most common ones include combining a fundamental laser frequency with its second harmonic or with higher -frequency pulses (or pulse trains) as well as using few-cycle pulses with known carrier-envelope phase (CEP). In the case of CEP, control over chemical transformations, typically occurring on a timescale of many femtoseconds, is driven by much faster sub-cycle processes of subfemtosecond to few-femtosecond duration. This is possible because electrons are much lighter than nuclei and fast electron motion is coupled to the much slower nuclear motion. The control originates from populating coherent superpositions of different electronic or vibrational states with relative phases that are dependent on the CEP or phase offset between components of a two-color pulse. In this paper, we review the recent progress made in the directional control over chemical processes, driven by intense few-cycle laser pulses a of waveform-tailored electric field, in different molecules.

  1. Injectable controlled release depots for large molecules

    PubMed Central

    Schwendeman, Steven P.; Shah, Ronak B.; Bailey, Brittany A.; Schwendeman, Anna S.

    2014-01-01

    Biodegradable, injectable depot formulations for long-term controlled drug release have improved therapy for a number of drug molecules and led to over a dozen highly successful pharmaceutical products. Until now, success has been limited to several small molecules and peptides, although remarkable improvements have been accomplished in some of these cases. For example, twice-a-year depot injections with leuprolide are available compared to the once-a-day injection of the solution dosage form. Injectable depots are typically prepared by encapsulation of the drug in poly(lactic-co-glycolic acid) (PLGA), a polymer that is used in children every day as a resorbable suture material, and therefore, highly biocompatible. PLGAs remain today as one of the few “real world” biodegradable synthetic biomaterials used in US FDA-approved parenteral long-acting-release (LAR) products. Despite their success, there remain critical barriers to the more widespread use of PLGA LAR products, particularly for delivery of more peptides and other large molecular drugs, namely proteins. In this review, we describe key concepts in the development of injectable PLGA controlled-release depots for peptides and proteins, and then use this information to identify key issues impeding greater widespread use of PLGA depots for this class of drugs. Finally, we examine important approaches, particularly those developed in our research laboratory, toward overcoming these barriers to advance commercial LAR development. PMID:24929039

  2. Injectable controlled release depots for large molecules.

    PubMed

    Schwendeman, Steven P; Shah, Ronak B; Bailey, Brittany A; Schwendeman, Anna S

    2014-09-28

    Biodegradable, injectable depot formulations for long-term controlled drug release have improved therapy for a number of drug molecules and led to over a dozen highly successful pharmaceutical products. Until now, success has been limited to several small molecules and peptides, although remarkable improvements have been accomplished in some of these cases. For example, twice-a-year depot injections with leuprolide are available compared to the once-a-day injection of the solution dosage form. Injectable depots are typically prepared by encapsulation of the drug in poly(lactic-co-glycolic acid) (PLGA), a polymer that is used in children every day as a resorbable suture material, and therefore, highly biocompatible. PLGAs remain today as one of the few "real world" biodegradable synthetic biomaterials used in US FDA-approved parenteral long-acting-release (LAR) products. Despite their success, there remain critical barriers to the more widespread use of PLGA LARproducts, particularly for delivery of more peptides and other large molecular drugs, namely proteins. In this review, we describe key concepts in the development of injectable PLGA controlled-release depots for peptides and proteins, and then use this information to identify key issues impeding greater widespread use of PLGA depots for this class of drugs. Finally, we examine important approaches, particularly those developed in our research laboratory, toward overcoming these barriers to advance commercial LAR development.

  3. Coherent-control of linear signals: Frequency-domain analysis

    NASA Astrophysics Data System (ADS)

    Mukamel, Shaul

    2013-10-01

    The dependence of various types of linear signals on the phase profile of broadband optical pulses is examined using fundamental time translation invariance symmetry of multipoint correlation functions. The frequency-domain wave-mixing analysis presented here unifies several arguments made earlier with respect to the conditions whereby coherent control schemes may be used.

  4. Coherent control of meta-device (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Tseng, Ming Lun; Fang, Xu; Chu, Cheng Hung; Wu, Hui Jun; Huang, Yao-Wei; Tsai, Wei-Yi; Chen, Mu-Ku; Wang, Hsiang-Chu; Chen, Ching-Fu; Zheludev, Nikolay I.; Tsai, Din Ping

    2016-09-01

    Selective excitation of specific multipolar resonances in matter can be of great utility in understanding the internal make-up of the underlying material and, as a result, in developing novel nanophotonic devices. Many efforts have been addressed on this topic. For example, the emission spectra related to the different multipolar transitions of trivalent europium can be modulated by changing the thickness of the dielectric spacer between the gold mirror and the fluorescent layer. In this talk, we reported the results about active control of the multipolar resonance in metadevices using the coherent control technique. In the coherent control spectroscopy system, the optical standing wave constructed from two counterpart propagation coherent beams is utilized as the excitation. By controlling the time delay between two ultrafast pulses to decide the location of metadivce as the electromagnetic field node or antinode node of standing wave, the absorption related to the specific multipolar resonance can be controlled. Using this technique, with the 30-nm-thick metadevice, the broadband controlling light with light without nonlinearity can be realized. The switching contrast ratios can be as high as 3:1 with a modulation bandwidth in excess of 2 THz. The active control of the high order and complex optical resonance related to the magnetic dipole, electric quadrupole, and toroidal dipole in the metamaterial is reported as well. This research can be applied in the all ultrafast all-optical data processing and the active control of the resonances of metadevice with high order multipolar resonance.

  5. Nonlocal Nuclear Spin Quieting in Quantum Dot Molecules: Optically Induced Extended Two-Electron Spin Coherence Time

    NASA Astrophysics Data System (ADS)

    Chow, Colin M.; Ross, Aaron M.; Kim, Danny; Gammon, Daniel; Bracker, Allan S.; Sham, L. J.; Steel, Duncan G.

    2016-08-01

    We demonstrate the extension of coherence between all four two-electron spin ground states of an InAs quantum dot molecule (QDM) via nonlocal suppression of nuclear spin fluctuations in two vertically stacked quantum dots (QDs), while optically addressing only the top QD transitions. Long coherence times are revealed through dark-state spectroscopy as resulting from nuclear spin locking mediated by the exchange interaction between the QDs. Line shape analysis provides the first measurement of the quieting of the Overhauser field distribution correlating with reduced nuclear spin fluctuations.

  6. Photodissociation of ultracold diatomic strontium molecules with quantum state control

    NASA Astrophysics Data System (ADS)

    McDonald, M.; McGuyer, B. H.; Apfelbeck, F.; Lee, C.-H.; Majewska, I.; Moszynski, R.; Zelevinsky, T.

    2016-07-01

    Chemical reactions at ultracold temperatures are expected to be dominated by quantum mechanical effects. Although progress towards ultracold chemistry has been made through atomic photoassociation, Feshbach resonances and bimolecular collisions, these approaches have been limited by imperfect quantum state selectivity. In particular, attaining complete control of the ground or excited continuum quantum states has remained a challenge. Here we achieve this control using photodissociation, an approach that encodes a wealth of information in the angular distribution of outgoing fragments. By photodissociating ultracold 88Sr2 molecules with full control of the low-energy continuum, we access the quantum regime of ultracold chemistry, observing resonant and nonresonant barrier tunnelling, matter-wave interference of reaction products and forbidden reaction pathways. Our results illustrate the failure of the traditional quasiclassical model of photodissociation and instead are accurately described by a quantum mechanical model. The experimental ability to produce well-defined quantum continuum states at low energies will enable high-precision studies of long-range molecular potentials for which accurate quantum chemistry models are unavailable, and may serve as a source of entangled states and coherent matter waves for a wide range of experiments in quantum optics.

  7. Photodissociation of ultracold diatomic strontium molecules with quantum state control.

    PubMed

    McDonald, M; McGuyer, B H; Apfelbeck, F; Lee, C-H; Majewska, I; Moszynski, R; Zelevinsky, T

    2016-07-07

    Chemical reactions at ultracold temperatures are expected to be dominated by quantum mechanical effects. Although progress towards ultracold chemistry has been made through atomic photoassociation, Feshbach resonances and bimolecular collisions, these approaches have been limited by imperfect quantum state selectivity. In particular, attaining complete control of the ground or excited continuum quantum states has remained a challenge. Here we achieve this control using photodissociation, an approach that encodes a wealth of information in the angular distribution of outgoing fragments. By photodissociating ultracold (88)Sr2 molecules with full control of the low-energy continuum, we access the quantum regime of ultracold chemistry, observing resonant and nonresonant barrier tunnelling, matter-wave interference of reaction products and forbidden reaction pathways. Our results illustrate the failure of the traditional quasiclassical model of photodissociation and instead are accurately described by a quantum mechanical model. The experimental ability to produce well-defined quantum continuum states at low energies will enable high-precision studies of long-range molecular potentials for which accurate quantum chemistry models are unavailable, and may serve as a source of entangled states and coherent matter waves for a wide range of experiments in quantum optics.

  8. Coherent phase control of the product branching ratio in the photodissociation of dimethylsulfide

    SciTech Connect

    Nagai, Hidekazu; Ohmura, Hideki; Ito, Fumiyuki; Nakanaga, Taisuke; Tachiya, Masanori

    2006-01-21

    Coherent phase control of the photodissociation reaction of the dimethylsulfide has been achieved by means of quantum-mechanical interference between one- and three-photon transitions. Dimethylsulfide was irradiated by fundamental and frequency-tripled outputs of a visible laser (600.5-602.5 nm), simultaneously to yield CH{sub 3}S{sup +} and CH{sub 3}SCH{sub 2}{sup +} fragment ions. The branching ratio of the two product channels could be modulated with variation of the phase difference between the light fields. This accounted for the difference between the molecular phases of the two product channels. The phase lag was observed to have a maximum value of 8 deg. at 601.5 nm. This is the first result of a selective bond breaking in a polyatomic molecule by the coherent phase control.

  9. Coherent feedback control of a single qubit in diamond

    NASA Astrophysics Data System (ADS)

    Hirose, Masashi; Cappellaro, Paola

    2016-04-01

    Engineering desired operations on qubits subjected to the deleterious effects of their environment is a critical task in quantum information processing, quantum simulation and sensing. The most common approach relies on open-loop quantum control techniques, including optimal-control algorithms based on analytical or numerical solutions, Lyapunov design and Hamiltonian engineering. An alternative strategy, inspired by the success of classical control, is feedback control. Because of the complications introduced by quantum measurement, closed-loop control is less pervasive in the quantum setting and, with exceptions, its experimental implementations have been mainly limited to quantum optics experiments. Here we implement a feedback-control algorithm using a solid-state spin qubit system associated with the nitrogen vacancy centre in diamond, using coherent feedback to overcome the limitations of measurement-based feedback, and show that it can protect the qubit against intrinsic dephasing noise for milliseconds. In coherent feedback, the quantum system is connected to an auxiliary quantum controller (ancilla) that acquires information about the output state of the system (by an entangling operation) and performs an appropriate feedback action (by a conditional gate). In contrast to open-loop dynamical decoupling techniques, feedback control can protect the qubit even against Markovian noise and for an arbitrary period of time (limited only by the coherence time of the ancilla), while allowing gate operations. It is thus more closely related to quantum error-correction schemes, although these require larger and increasing qubit overheads. Increasing the number of fresh ancillas enables protection beyond their coherence time. We further evaluate the robustness of the feedback protocol, which could be applied to quantum computation and sensing, by exploring a trade-off between information gain and decoherence protection, as measurement of the ancilla-qubit correlation

  10. Two beam coherent control in semiconductors

    NASA Astrophysics Data System (ADS)

    Král, P.; Sipe, J. E.

    1998-03-01

    Recently, DC current has been generated in superlatices and bulk semiconductors [1] by a simultaneous excitations with two laser beams, giving one-photon and two-photon transitions with frequencies 2ω, ω. In these experiments directionality of the current can be controlled by the relative phase of the two fields. We develop a methodology, based on nonequilibrium Green functions, describing this phenomenon in the presence of many-particle scattering. In the mean-field level of this approach, simultaneous action of the two fields can be reduced to an effective field with a tunable relative excitation strength for different wave vectors of the Brillouine zone. We derive transport equations for a `quasi'-linear, nonlinear and pulse-like excitations in this effective field. In the weak scattering limit, they agree with the Boltzmann equation with generation rates obtained from the Fermi's Golden Rule [2]. We apply the steady-state `quasi'-linear equations to a model 1D quantum wire in the presence of LA phonons, which serves as a reference system for future calculations in realistic 3D systems. Numerical results for the induced dc current are presented in many details. [1] E. Dupont et al., Phys. Rev. Lett. 74, 3596 (1995); A. Haché et al., Phys. Rev. Lett. 78, 306 (1997). [2] R. Atanasov et al., Phys. Rev. Lett. 76, 1703 (1996).

  11. Enhancing coherent transport in a photonic network using controllable decoherence

    NASA Astrophysics Data System (ADS)

    Biggerstaff, Devon N.; Heilmann, René; Zecevik, Aidan A.; Gräfe, Markus; Broome, Matthew A.; Fedrizzi, Alessandro; Nolte, Stefan; Szameit, Alexander; White, Andrew G.; Kassal, Ivan

    2016-04-01

    Transport phenomena on a quantum scale appear in a variety of systems, ranging from photosynthetic complexes to engineered quantum devices. It has been predicted that the efficiency of coherent transport can be enhanced through dynamic interaction between the system and a noisy environment. We report an experimental simulation of environment-assisted coherent transport, using an engineered network of laser-written waveguides, with relative energies and inter-waveguide couplings tailored to yield the desired Hamiltonian. Controllable-strength decoherence is simulated by broadening the bandwidth of the input illumination, yielding a significant increase in transport efficiency relative to the narrowband case. We show integrated optics to be suitable for simulating specific target Hamiltonians as well as open quantum systems with controllable loss and decoherence.

  12. Enhancing coherent transport in a photonic network using controllable decoherence.

    PubMed

    Biggerstaff, Devon N; Heilmann, René; Zecevik, Aidan A; Gräfe, Markus; Broome, Matthew A; Fedrizzi, Alessandro; Nolte, Stefan; Szameit, Alexander; White, Andrew G; Kassal, Ivan

    2016-04-15

    Transport phenomena on a quantum scale appear in a variety of systems, ranging from photosynthetic complexes to engineered quantum devices. It has been predicted that the efficiency of coherent transport can be enhanced through dynamic interaction between the system and a noisy environment. We report an experimental simulation of environment-assisted coherent transport, using an engineered network of laser-written waveguides, with relative energies and inter-waveguide couplings tailored to yield the desired Hamiltonian. Controllable-strength decoherence is simulated by broadening the bandwidth of the input illumination, yielding a significant increase in transport efficiency relative to the narrowband case. We show integrated optics to be suitable for simulating specific target Hamiltonians as well as open quantum systems with controllable loss and decoherence.

  13. Enhancing coherent transport in a photonic network using controllable decoherence

    PubMed Central

    Biggerstaff, Devon N.; Heilmann, René; Zecevik, Aidan A.; Gräfe, Markus; Broome, Matthew A.; Fedrizzi, Alessandro; Nolte, Stefan; Szameit, Alexander; White, Andrew G.; Kassal, Ivan

    2016-01-01

    Transport phenomena on a quantum scale appear in a variety of systems, ranging from photosynthetic complexes to engineered quantum devices. It has been predicted that the efficiency of coherent transport can be enhanced through dynamic interaction between the system and a noisy environment. We report an experimental simulation of environment-assisted coherent transport, using an engineered network of laser-written waveguides, with relative energies and inter-waveguide couplings tailored to yield the desired Hamiltonian. Controllable-strength decoherence is simulated by broadening the bandwidth of the input illumination, yielding a significant increase in transport efficiency relative to the narrowband case. We show integrated optics to be suitable for simulating specific target Hamiltonians as well as open quantum systems with controllable loss and decoherence. PMID:27080915

  14. Coherent control of plasmonic nanoantennas using optical eigenmodes

    PubMed Central

    Kosmeier, Sebastian; De Luca, Anna Chiara; Zolotovskaya, Svetlana; Di Falco, Andrea; Dholakia, Kishan; Mazilu, Michael

    2013-01-01

    The last decade has seen subwavelength focusing of the electromagnetic field in the proximity of nanoplasmonic structures with various designs. However, a shared issue is the spatial confinement of the field, which is mostly inflexible and limited to fixed locations determined by the geometry of the nanostructures, which hampers many applications. Here, we coherently address numerically and experimentally single and multiple plasmonic nanostructures chosen from a given array, resorting to the principle of optical eigenmodes. By decomposing the light field into optical eigenmodes, specifically tailored to the nanostructure, we create a subwavelength, selective and dynamic control of the incident light. The coherent control of plasmonic nanoantennas using this approach shows an almost zero crosstalk. This approach is applicable even in the presence of large transmission aberrations, such as present in holographic diffusers and multimode fibres. The method presents a paradigm shift for the addressing of plasmonic nanostructures by light. PMID:23657743

  15. Spatiotemporal Coherent Control of Thermal Excitations in Solids

    NASA Astrophysics Data System (ADS)

    Sander, M.; Herzog, M.; Pudell, J. E.; Bargheer, M.; Weinkauf, N.; Pedersen, M.; Newby, G.; Sellmann, J.; Schwarzkopf, J.; Besse, V.; Temnov, V. V.; Gaal, P.

    2017-08-01

    X-ray reflectivity measurements of femtosecond laser-induced transient gratings (TG) are applied to demonstrate the spatiotemporal coherent control of thermally induced surface deformations on ultrafast time scales. Using grazing incidence x-ray diffraction we unambiguously measure the amplitude of transient surface deformations with sub-Å resolution. Understanding the dynamics of femtosecond TG excitations in terms of superposition of acoustic and thermal gratings makes it possible to develop new ways of coherent control in x-ray diffraction experiments. Being the dominant source of TG signal, the long-living thermal grating with spatial period Λ can be canceled by a second, time-delayed TG excitation shifted by Λ /2 . The ultimate speed limits of such an ultrafast x-ray shutter are inferred from the detailed analysis of thermal and acoustic dynamics in TG experiments.

  16. Coherent control of the isomerization of retinal in bacteriorhodopsin in the high intensity regime

    SciTech Connect

    Prokhorenko, Valentyn I.; Halpin, Alexei; Johnson, Philip J. M.; Miller, R. J. Dwayne; Brown, Leonid S.

    2011-02-28

    Coherent control protocols provide a direct experimental determination of the relative importance of quantum interference or phase relationships of coupled states along a selected pathway. These effects are most readily observed in the high intensity regime where the field amplitude is sufficient to overcome decoherence effects. The coherent response of retinal photoisomerization in bacteriorhodopsin to the phase of the photoexcitation pulses was examined at fluences of 10{sup 15}- 2.5 x 10{sup 16} photons per square centimeter, comparable to or higher than the saturation excitation level of the S{sub 0}-S{sub 1} retinal electronic transition. At moderate excitation levels of {approx}6 x 10{sup 15} photons/cm{sup 2} (<100 GW/cm{sup 2}), chirping the excitation pulses increases the all-trans to 13-cis isomerization yield by up to 16% relative to transform limited pulses. The reported results extend previous weak-field studies [Prokhorenko et al., Science 313, 1257 (2006)] and further illustrate that quantum coherence effects persist along the reaction coordinate in strong fields even for systems as complex as biological molecules. However, for higher excitation levels of {approx}200 GW/cm{sup 2}, there is a dramatic change in photophysics that leads to multiphoton generated photoproducts unrelated to the target isomerization reaction channel and drastically changes the observed isomerization kinetics that appears, in particular, as a red shift of the transient spectra. These results explain the apparent contradictions of the work by Florean et al.[Proc. Natl. Acad. Sci. U.S.A. 106, 10896 (2009)] in the high intensity regime. We are able to show that the difference in observations and interpretation is due to artifacts associated with additional multiphoton-induced photoproducts. At the proper monitoring wavelengths, coherent control in the high intensity regime is clearly observable. The present work highlights the importance of conducting coherent control

  17. Coherent control of the isomerization of retinal in bacteriorhodopsin in the high intensity regime.

    PubMed

    Prokhorenko, Valentyn I; Halpin, Alexei; Johnson, Philip J M; Miller, R J Dwayne; Brown, Leonid S

    2011-02-28

    Coherent control protocols provide a direct experimental determination of the relative importance of quantum interference or phase relationships of coupled states along a selected pathway. These effects are most readily observed in the high intensity regime where the field amplitude is sufficient to overcome decoherence effects. The coherent response of retinal photoisomerization in bacteriorhodopsin to the phase of the photoexcitation pulses was examined at fluences of 10(15) - 2.5 × 10(16) photons per square centimeter, comparable to or higher than the saturation excitation level of the S(0) - S(1) retinal electronic transition. At moderate excitation levels of ∼6 × 10(15) photons/cm(2) (<100 GW/cm(2)), chirping the excitation pulses increases the all-trans to 13-cis isomerization yield by up to 16% relative to transform limited pulses. The reported results extend previous weak-field studies [Prokhorenko et al., Science 313, 1257 (2006)] and further illustrate that quantum coherence effects persist along the reaction coordinate in strong fields even for systems as complex as biological molecules. However, for higher excitation levels of ∼200 GW/cm(2), there is a dramatic change in photophysics that leads to multiphoton generated photoproducts unrelated to the target isomerization reaction channel and drastically changes the observed isomerization kinetics that appears, in particular, as a red shift of the transient spectra. These results explain the apparent contradictions of the work by Florean et al. [Proc. Natl. Acad. Sci. U.S.A. 106, 10896 (2009)] in the high intensity regime. We are able to show that the difference in observations and interpretation is due to artifacts associated with additional multiphoton-induced photoproducts. At the proper monitoring wavelengths, coherent control in the high intensity regime is clearly observable. The present work highlights the importance of conducting coherent control experiments in the low intensity regime

  18. Coherent control of the silicon-vacancy spin in diamond

    NASA Astrophysics Data System (ADS)

    Pingault, Benjamin; Jarausch, David-Dominik; Hepp, Christian; Klintberg, Lina; Becker, Jonas N.; Markham, Matthew; Becher, Christoph; Atatüre, Mete

    2017-05-01

    Spin impurities in diamond have emerged as a promising building block in a wide range of solid-state-based quantum technologies. The negatively charged silicon-vacancy centre combines the advantages of its high-quality photonic properties with a ground-state electronic spin, which can be read out optically. However, for this spin to be operational as a quantum bit, full quantum control is essential. Here we report the measurement of optically detected magnetic resonance and the demonstration of coherent control of a single silicon-vacancy centre spin with a microwave field. Using Ramsey interferometry, we directly measure a spin coherence time, T2*, of 115+/-9 ns at 3.6 K. The temperature dependence of coherence times indicates that dephasing and decay of the spin arise from single-phonon-mediated excitation between orbital branches of the ground state. Our results enable the silicon-vacancy centre spin to become a controllable resource to establish spin-photon quantum interfaces.

  19. Coherent control of the silicon-vacancy spin in diamond.

    PubMed

    Pingault, Benjamin; Jarausch, David-Dominik; Hepp, Christian; Klintberg, Lina; Becker, Jonas N; Markham, Matthew; Becher, Christoph; Atatüre, Mete

    2017-05-30

    Spin impurities in diamond have emerged as a promising building block in a wide range of solid-state-based quantum technologies. The negatively charged silicon-vacancy centre combines the advantages of its high-quality photonic properties with a ground-state electronic spin, which can be read out optically. However, for this spin to be operational as a quantum bit, full quantum control is essential. Here we report the measurement of optically detected magnetic resonance and the demonstration of coherent control of a single silicon-vacancy centre spin with a microwave field. Using Ramsey interferometry, we directly measure a spin coherence time, T2*, of 115±9 ns at 3.6 K. The temperature dependence of coherence times indicates that dephasing and decay of the spin arise from single-phonon-mediated excitation between orbital branches of the ground state. Our results enable the silicon-vacancy centre spin to become a controllable resource to establish spin-photon quantum interfaces.

  20. Controlled Tethering Molecules via Crystal Surface Engineering

    NASA Astrophysics Data System (ADS)

    Cheng, Stephen Z. D.; Zheng, Joseph X.; Chen, William Y.

    2004-03-01

    So far, almost all experiments in tethering chain molecules onto substrates are via "grafting to" or "grafting from" polymerizations in addition to physical absorption. Issues concerning the uniformity of the tethered chain density and the molecular weight distribution of the chains tethered by polymerization always undermine the properties experimentally observed. We proposed a novel design to precisely control the tethering density of polystyrene (PS) brushes on a poly(ethylene oxide) (PEO) or a poly(L-lactic acid) (PLLA) lamellar crystal basal surface using PEO-b-PS or PLLA-b-PS diblock copolymers. As the crystallization temperature (Tc) increased in either a PEO-b-PS/mixed solution (chrolobenzene/octane) or a PLLA-b-PS/amyl acetate solution, the PEO or PLLA lamellar thickness (d) increased, and correspondingly, the number of folds per PEO or PLLA block was reduced. The reduced tethered density (Σ*) of the PS brushes thus increased. At an onset where the PS brushes are overcrowded within the solution, a drastic slope change in the relationship between (d)-1 and Tc occurs in both cases at a Σ* between 3 - 4. This illustrates that the weak to intermediate interaction changes of the PS brushes with their neighbors may be universally represented.

  1. Controlling Electron Dynamics of Oriented Molecules Using Attosecond Pulses

    NASA Astrophysics Data System (ADS)

    Miyabe, S.; Lucchese, R.; Rescigno, T.; Midorikawa, K.; McCurdy, C. W.

    2016-05-01

    Attosecond pulses offer routes to study and potentially manipulate ultrafast electron dynamics of atoms and molecules on their intrinsic time scale, and therefore attracted attention from various disciplines. In this report we show that for a molecule, oriented in space and excited by an attosecond pulse, the amount of electronic coherence left in the ion depends not only on the orientation of the electric field polarization vector in the molecular-frame, but also on the angular distribution in molecular-frame of electrons ejected in different ionization channels. In our numerical simulation we use one-photon single ionization amplitudes calculated using the complex-Kohn variational method, and we express the amount of coherence in the ion in terms of the (N+1)-electron reduced density matrix of the full N-electron system of the ion plus ionized electron.

  2. Coherent control of long-range photoinduced electron transfer by stimulated X-ray Raman processes

    PubMed Central

    Dorfman, Konstantin E.; Zhang, Yu; Mukamel, Shaul

    2016-01-01

    We show that X-ray pulses resonant with selected core transitions can manipulate electron transfer (ET) in molecules with ultrafast and atomic selectivity. We present possible protocols for coherently controlling ET dynamics in donor–bridge–acceptor (DBA) systems by stimulated X-ray resonant Raman processes involving various transitions between the D, B, and A sites. Simulations presented for a Ru(II)–Co(III) model complex demonstrate how the shapes, phases and amplitudes of the X-ray pulses can be optimized to create charge on demand at selected atoms, by opening up otherwise blocked ET pathways. PMID:27559082

  3. Coherent control of long-range photoinduced electron transfer by stimulated X-ray Raman processes.

    PubMed

    Dorfman, Konstantin E; Zhang, Yu; Mukamel, Shaul

    2016-09-06

    We show that X-ray pulses resonant with selected core transitions can manipulate electron transfer (ET) in molecules with ultrafast and atomic selectivity. We present possible protocols for coherently controlling ET dynamics in donor-bridge-acceptor (DBA) systems by stimulated X-ray resonant Raman processes involving various transitions between the D, B, and A sites. Simulations presented for a Ru(II)-Co(III) model complex demonstrate how the shapes, phases and amplitudes of the X-ray pulses can be optimized to create charge on demand at selected atoms, by opening up otherwise blocked ET pathways.

  4. Quantum coherence effects in hybrid nanoparticle molecules in the presence of ultra-short dephasing times

    NASA Astrophysics Data System (ADS)

    Sadeghi, S. M.

    2012-11-01

    We study quantum coherence effects in single nanoparticle systems consisting of a semiconductor quantum dot and a metallic nanoparticle in the presence of the ultra-short dephasing times of the quantum dots. The results suggest that coherent exciton-plasmon coupling can sustain the collective molecular resonances (plasmonic meta-resonances) of these systems at about room temperature. We investigate quantum optical properties of the quantum dots under this condition, demonstrating formation of ultranarrow gain and absorption spectral lines. These results are discussed in terms of plasmonic normalization of coherent population oscillation and the collective states of the nanoparticle systems.

  5. Coherent control of ultracold collisions with chirped light: Direction matters

    SciTech Connect

    Wright, M. J.; Pechkis, J. A.; Carini, J. L.; Gould, P. L.; Kallush, S.; Kosloff, R.

    2007-05-15

    We demonstrate the ability to coherently control ultracold atomic Rb collisions using frequency-chirped light on the nanosecond time scale. For certain center frequencies of the chirp, the rate of inelastic trap-loss collisions induced by negatively chirped light is dramatically suppressed compared to the case of a positive chirp. We attribute this to a fundamental asymmetry in the system: an excited wave packet moves inward on the attractive molecular potential. For a positive chirp, the resonance condition moves outward in time, while for a negative chirp, it moves inward, in the same direction as the excited wave packet; this allows multiple interactions between the wave packet and the light, enabling the wave packet to be returned coherently to the ground state. Classical and quantum calculations support this interpretation.

  6. Non-Markovian coherent feedback control of quantum dot systems

    NASA Astrophysics Data System (ADS)

    Xue, Shibei; Wu, Rebing; Hush, Michael R.; Tarn, Tzyh-Jong

    2017-03-01

    In this paper we present a non-Markovian coherent feedback scheme for decoherence suppression in single quantum dot systems. The feedback loop is closed via a quantum tunnelling junction between the natural source and drain baths of the quantum dot. The exact feedback-controlled non-Markovian Langevin equation is derived for describing the dynamics of the quantum dot. To deal with the nonlinear memory function in the Langevin equation, we analyse the Green’s function-based root locus, from which we show that the decoherence of the quantum dot can be suppressed via increasing the feedback coupling strength. The effectiveness of decoherence suppression induced by non-Markovian coherent feedback is demonstrated by a single quantum dot example bathed with Lorentzian noises.

  7. Coherent feedback control of multipartite quantum entanglement for optical fields

    SciTech Connect

    Yan, Zhihui; Jia, Xiaojun; Xie, Changde; Peng, Kunchi

    2011-12-15

    Coherent feedback control (CFC) of multipartite optical entangled states produced by a nondegenerate optical parametric amplifier is theoretically studied. The features of the quantum correlations of amplitude and phase quadratures among more than two entangled optical modes can be controlled by tuning the transmissivity of the optical beam splitter in the CFC loop. The physical conditions to enhance continuous variable multipartite entanglement of optical fields utilizing the CFC loop are obtained. The numeric calculations based on feasible physical parameters of realistic systems provide direct references for the design of experimental devices.

  8. Coherent Anti-Stokes Raman Scattering Spectroscopy of Single Molecules in Solution

    SciTech Connect

    Sunney Xie, Wei Min, Chris Freudiger, Sijia Lu

    2012-01-18

    During this funding period, we have developed two breakthrough techniques. The first is stimulated Raman scattering microscopy, providing label-free chemical contrast for chemical and biomedical imaging based on vibrational spectroscopy. Spontaneous Raman microscopy provides specific vibrational signatures of chemical bonds, but is often hindered by low sensitivity. We developed a three-dimensional multiphoton vibrational imaging technique based on stimulated Raman scattering (SRS). The sensitivity of SRS imaging is significantly greater than that of spontaneous Raman microscopy, which is achieved by implementing high-frequency (megahertz) phase-sensitive detection. SRS microscopy has a major advantage over previous coherent Raman techniques in that it offers background-free and readily interpretable chemical contrast. We demonstrated a variety of biomedical applications, such as differentiating distributions of omega-3 fatty acids and saturated lipids in living cells, imaging of brain and skin tissues based on intrinsic lipid contrast, and monitoring drug delivery through the epidermis. This technology offers exciting prospect for medical imaging. The second technology we developed is stimulated emission microscopy. Many chromophores, such as haemoglobin and cytochromes, absorb but have undetectable fluorescence because the spontaneous emission is dominated by their fast non-radiative decay. Yet the detection of their absorption is difficult under a microscope. We use stimulated emission, which competes effectively with the nonradiative decay, to make the chromophores detectable, as a new contrast mechanism for optical microscopy. We demonstrate a variety of applications of stimulated emission microscopy, such as visualizing chromoproteins, non-fluorescent variants of the green fluorescent protein, monitoring lacZ gene expression with a chromogenic reporter, mapping transdermal drug distribu- tions without histological sectioning, and label-free microvascular

  9. High resolution atomic coherent control via spectral phase manipulation of an optical frequency comb.

    PubMed

    Stowe, Matthew C; Cruz, Flavio C; Marian, Adela; Ye, Jun

    2006-04-21

    We demonstrate high resolution coherent control of cold atomic rubidium utilizing spectral phase manipulation of a femtosecond optical frequency comb. Transient coherent accumulation is directly manifested by the enhancement of signal amplitude and spectral resolution via the pulse number. The combination of frequency comb technology and spectral phase manipulation enables coherent control techniques to enter a new regime with natural linewidth resolution.

  10. High Resolution Atomic Coherent Control via Spectral Phase Manipulation of an Optical Frequency Comb

    SciTech Connect

    Stowe, Matthew C.; Cruz, Flavio C.; Marian, Adela; Ye Jun

    2006-04-21

    We demonstrate high resolution coherent control of cold atomic rubidium utilizing spectral phase manipulation of a femtosecond optical frequency comb. Transient coherent accumulation is directly manifested by the enhancement of signal amplitude and spectral resolution via the pulse number. The combination of frequency comb technology and spectral phase manipulation enables coherent control techniques to enter a new regime with natural linewidth resolution.

  11. Prospect of detection and recognition of single biological molecules using ultrafast coherent dynamics in quantum dot-metallic nanoparticle systems

    NASA Astrophysics Data System (ADS)

    Sadeghi, S. M.

    2015-08-01

    Conventional plasmonic sensors are based on the intrinsic resonances of metallic nanoparticles. In such sensors wavelength shift of such resonances are used to detect biological molecules. Recently we introduced ultra-sensitive timedomain nanosensors based on the way variations in the environmental conditions influence coherent dynamics of hybrid systems consisting of metallic nanoparticles and quantum dots. Such dynamics are generated via interaction of these systems with a laser field, generating quantum coherence and coherent exciton-plasmon coupling. These sensors are based on impact of variations of the refractive index of the environment on such dynamics, generating time-dependent changes in the emission of the QDs. In this paper we study the impact of material properties of the metallic nanoparticles on this process and demonstrate the key role played by the design of the quantum dots. We show that Ag nanoparticles, even in a simple spherical shape, may allow these sensors to operate at room temperature, owing to the special properties of quantum dot-metallic nanoparticle systems that may allow coherent effects utilized in such sensors happen in the presence of the ultrafast polarization dephasing of quantum dots.

  12. Control of Coherently Coupled Exciton Polaritons in Monolayer Tungsten Disulphide

    NASA Astrophysics Data System (ADS)

    Liu, Xiaoze; Bao, Wei; Li, Quanwei; Ropp, Chad; Wang, Yuan; Zhang, Xiang

    2017-07-01

    Monolayer transition metal dichalcogenides (TMD) with confined 2D Wannier-Mott excitons are intriguing for the fundamental study of strong light-matter interactions and the exploration of exciton polaritons at high temperatures. However, the research of 2D exciton polaritons has been hindered because the polaritons in these atomically thin semiconductors discovered so far can hardly support strong nonlinear interactions and quantum coherence due to uncontrollable polariton dynamics and weakened coherent coupling. In this work, we demonstrate, for the first time, a precisely controlled hybrid composition with angular dependence and dispersion-correlated polariton emission by tuning the polariton dispersion in TMD over a broad temperature range of 110-230 K in a single cavity. This tamed polariton emission is achieved by the realization of robust coherent exciton-photon coupling in monolayer tungsten disulphide (WS2 ) with large splitting-to-linewidth ratios (>3.3 ). The unprecedented ability to manipulate the dispersion and correlated properties of TMD exciton polaritons at will offers new possibilities to explore important quantum phenomena such as inversionless lasing, Bose-Einstein condensation, and superfluidity.

  13. Small molecule control of bacterial biofilms

    PubMed Central

    Worthington, Roberta J.; Richards, Justin J.

    2012-01-01

    Bacterial biofilms are defined as a surface attached community of bacteria embedded in a matrix of extracellular polymeric substances that they have produced. When in the biofilm state, bacteria are more resistant to antibiotics and the host immune response than are their planktonic counterparts. Biofilms are increasingly recognized as being significant in human disease, accounting for 80% of bacterial infections in the body and diseases associated with bacterial biofilms include: lung infections of cystic fibrosis, colitis, urethritis, conjunctivitis, otitis, endocarditis and periodontitis. Additionally, biofilm infections of indwelling medical devices are of particular concern, as once the device is colonized infection is virtually impossible to eradicate. Given the prominence of biofilms in infectious diseases, there has been an increased effort toward the development of small molecules that will modulate bacterial biofilm development and maintenance. In this review, we highlight the development of small molecules that inhibit and/or disperse bacterial biofilms through non-microbicidal mechanisms. The review discuses the numerous approaches that have been applied to the discovery of lead small molecules that mediate biofilm development. These approaches are grouped into: 1) the identification and development of small molecules that target one of the bacterial signaling pathways involved in biofilm regulation, 2) chemical library screening for compounds with anti-biofilm activity, and 3) the identification of natural products that possess anti-biofilm activity, and the chemical manipulation of these natural products to obtain analogues with increased activity. PMID:22733439

  14. Shaping femtosecond coherent anti-Stokes Raman spectra using optimal control theory.

    PubMed

    Pezeshki, Soroosh; Schreiber, Michael; Kleinekathöfer, Ulrich

    2008-04-21

    Optimal control theory is used to tailor laser pulses which enhance a femtosecond time-resolved coherent anti-Stokes Raman scattering (fs-CARS) spectrum in a certain frequency range. For this aim the optimal control theory has to be applied to a target state distributed in time. Explicit control mechanisms are given for shaping either the Stokes or the probe pulse in the four-wave mixing process. A simple molecule for which highly accurate potential energy surfaces are available, namely molecular iodine, is used to test the procedure. This approach of controlling vibrational motion and delivering higher intensities to certain frequency ranges might also be important for the improvement of CARS microscopy.

  15. Coherent control of atomic tunneling in a driven triple well

    SciTech Connect

    Lu Gengbiao; Hai Wenhua; Xie Qiongtao

    2011-01-15

    Coherent control of quantum tunneling is investigated for a single atom held in a driven triple-well potential without tight-binding approximation. In the high-frequency regime within or without multiphoton resonance, we find the analytical solutions and their numerical correspondences, including the special Floquet states of invariant populations and the non-Floquet states of slowly varying populations. The Floquet quasienergy spectrum exhibits anticrossings and crossings for different values of the driving parameters, which are associated with different tunneling properties described by the non-Floquet states. Applying the presented results, we suggest a scheme for transporting a single atom between nonadjacent wells or between adjacent wells.

  16. Coherent control of atomic transport in spinor optical lattices

    SciTech Connect

    Mischuck, Brian; Deutsch, Ivan H.; Jessen, Poul S.

    2010-02-15

    Coherent transport of atoms trapped in an optical lattice can be controlled by microwave-induced spin flips that correlate with site-to-site hopping. We study the controllability of homogeneous one-dimensional systems of noninteracting atoms in the absence of site addressability. Given these restrictions, we construct a deterministic protocol to map an initially localized Wannier state to a wave packet that is coherently distributed over n sites. As an example, we consider a one dimensional quantum walk in the presence of both realistic photon scattering and inhomogeneous broadening of the microwave transition due to the optical lattice. Using composite pulses to suppress errors, fidelities of over 95% can be achieved for a 25-step walk. We extend the protocol for state preparation to analytic solutions for arbitrary unitary maps given homogeneous systems and in the presence of time-dependent uniform forces. Such control is important for applications in quantum information processing, such as quantum computing and quantum simulations of condensed matter phenomena.

  17. Environmentally Mediated Coherent Control of a Spin Qubit in Diamond.

    PubMed

    Lillie, Scott E; Broadway, David A; Wood, James D A; Simpson, David A; Stacey, Alastair; Tetienne, Jean-Philippe; Hollenberg, Lloyd C L

    2017-04-21

    The coherent control of spin qubits forms the basis of many applications in quantum information processing and nanoscale sensing, imaging, and spectroscopy. Such control is conventionally achieved by direct driving of the qubit transition with a resonant global field, typically at microwave frequencies. Here we introduce an approach that relies on the resonant driving of nearby environment spins, whose localized magnetic field in turn drives the qubit when the environmental spin Rabi frequency matches the qubit resonance. This concept of environmentally mediated resonance (EMR) is explored experimentally using a qubit based on a single nitrogen-vacancy (NV) center in diamond, with nearby electronic spins serving as the environmental mediators. We demonstrate EMR driven coherent control of the NV spin state, including the observation of Rabi oscillations, free induction decay, and spin echo. This technique also provides a way to probe the nanoscale environment of spin qubits, which we illustrate by acquisition of electron spin resonance spectra from single NV centers in various settings.

  18. Coherent control with a multi-octave source

    NASA Astrophysics Data System (ADS)

    Goda, Sunil

    2007-12-01

    Ultrawide bandwidth sources of coherent light are useful for applications such as observing ultrafast chemical changes, spectroscopy, controlling chemical reactions, and nonlinear optics. Many of these applications require controllable pulses of particular temporal shape. Over the last decade, our group has constructed a source capable of generating a discrete set of optical frequency components spanning nearly two octaves of bandwidth from the ultraviolet to the near infrared. In addition, using a liquid crystal spatial light modulator, we control the relative phases of these frequency components. This work describes the use of pulse shaping with this multioctave source for coherent control of nonlinear optical processes. I describe an analytical technique using four-wave mixing for determining the phase relationship between frequency components (and consequently the temporal envelope) generated by this source. Using the same four-wave mixing process, I show simulations in which we are able to generate a prescribed amplitude spectrum of ultraviolet frequencies. The principle component that allows generation of arbitrary spectra is the use of a genetic algorithm to quickly find optimal pulse shapes. I use a genetic algorithm to experimentally control nonlinear optical processes. Using a resonantly-enhanced Raman mixing process I show the ability to efficiently alter the amplitude spectrum of our source. I alter the ratio of energy between sidebands by more than a factor of 50 as well as alter individual sideband energies by millijoules. I also experimentally control properties of laser-induced optical breakdown including its timing, its location, and whether it occurs. Finally, in the vein of source improvement, I show molecular modulation in a hollow fiber. The benefit of the fiber is that it requires 20 times less drive energy to be efficient allowing more stable, cheaper, higher repetition rate drive lasers. Together, these experiments and simulations show

  19. Interplay of polarization geometry and rotational dynamics in high-order harmonic generation from coherently rotating linear molecules.

    PubMed

    Faisal, F H M; Abdurrouf, A

    2008-03-28

    Recent reports on intense-field pump-probe experiments for high-order harmonic generation (HHG) from coherently rotating linear molecules have revealed remarkable characteristic effects of the simultaneous variation of the polarization geometry and the time delay on the high-order harmonic signals. We analyze the effects and give a unified theoretical account of the experimental observations. Furthermore, characteristic behavior at critical polarization angles are found that can help to identify the molecular orbital symmetry in connection with the problem of molecular imaging from the HHG data.

  20. Direct frequency comb spectroscopy and high-resolution coherent control

    NASA Astrophysics Data System (ADS)

    Stowe, Matthew C.

    We present the first experiments demonstrating absolute frequency measurements of one- and two-photon transitions using direct frequency comb spectroscopy (DFCS). In particular we phase stabilized the inter-pulse period and optical phases of the pulses emitted from a mode-locked Ti:Sapphire laser, creating a broad-bandwidth optical frequency comb. By referencing the optical comb directly to the cesium microwave frequency standard, we were able to measure absolute transition frequencies over greater than a 50 nm bandwidth, utilizing the phase coherence between wavelengths spanning from 741 nm to 795 nm. As an initial demonstration of DFCS we studied transitions from the 5S to 5P, 5D, and 7S states in Rb. To reduce Doppler broadening the atoms were laser cooled in a magneto-optical trap. We present an overview of several systematic error sources that perturb the natural transition frequencies, magnitudes, and linewidths. These include radiation pressure from the probe beam, AC-Stark shifts, Zeeman shifts, power-broadening, and incoherent optical pumping. After careful study and suppression of these systematic error sources, we measured transition linewidths as narrow as 1.1 MHz FWHM and 10 kHz linecenter uncertainties. Our measurements of the 5S to 7S two-photon transition frequency demonstrated the ability to determine the comb mode order numbers when the initial transition frequency is not known to better than the comb mode frequency spacing. By modifying the spectral phase of the pulses we demonstrated high-resolution coherent control. Our first coherent control experiment utilized a grating based pulse stretcher/compressor to apply a large chirp to the pulses. We measured the two-photon transition rate as a function of linear frequency chirp. The results illustrate the differences between similar classic coherent experiments done with a single femtosecond pulse and ours conducted with multiple pulses. Furthermore, we show that it is possible to reduce the two

  1. Physics of lateral triple quantum-dot molecules with controlled electron numbers.

    PubMed

    Hsieh, Chang-Yu; Shim, Yun-Pil; Korkusinski, Marek; Hawrylak, Pawel

    2012-11-01

    We review the recent progress in theory and experiments with lateral triple quantum dots with controlled electron numbers down to one electron in each dot. The theory covers electronic and spin properties as a function of topology, number of electrons, gate voltage and external magnetic field. The orbital Hund's rules and Nagaoka ferromagnetism, magnetic frustration and chirality, interplay of quantum interference and electron-electron interactions and geometrical phases are described and related to charging and transport spectroscopy. Fabrication techniques and recent experiments are covered, as well as potential applications of triple quantum-dot molecule in coherent control, spin manipulation and quantum computation.

  2. Coherence and control of single electron spins in quantum dots

    NASA Astrophysics Data System (ADS)

    Vandersypen, Lieven

    2008-03-01

    Following our earlier work on single-shot read-out and relaxation of a single spin in a quantum dot, we now demonstrate coherent control of a single spin (detection is done using a second spin in a neighbouring dot). First, we manipulate the spin using conventional magnetic resonance. Next, we show that we can also rotate the spin using electric fields instead of magnetic fields. In both cases, 90 rotations can be realized in about 50 ns or less. We use these control techniques to probe decoherence of an isolated electron spin. The spin dephases in about 30 ns, due to the hyperfine interaction with the uncontrolled nuclear spin bath in the host material of the dot. However, since the nuclear spin dynamics is very slow, this dephasing can be largely reversed using a spin-echo pulse. Echo decay times of about 0.5 us are obtained at 70 mT. In parallel, we have started work on quantum dots in graphene, which is expected to offer superior coherence times. As a first step, we have succeeded in opening a bandgap in bilayer graphene, necessary for electrostatic confinement of carriers. F.H.L. Koppens et al., Nature 446, 56 (2006). K.C. Nowack et al., Science Express, 1 Nov 2007. F.H.L. Koppens et al., arXiv:0711.0479. J.B. Oostinga, Nature Mat., in press.

  3. Automated alignment method for coherence-controlled holographic microscope

    NASA Astrophysics Data System (ADS)

    Dostal, Zbynek; Slaby, Tomas; Kvasnica, Lukas; Lostak, Martin; Krizova, Aneta; Chmelik, Radim

    2015-11-01

    A coherence-controlled holographic microscope (CCHM) was developed particularly for quantitative phase imaging and measurement of live cell dynamics, which is the proper subject of digital holographic microscopy (DHM). CCHM in low-coherence mode extends DHM in the study of living cells. However, this advantage is compensated by sensitivity of the system to easily become misaligned, which is a serious hindrance to wanted performance. Therefore, it became clear that introduction of a self-correcting system is inevitable. Accordingly, we had to devise a theory of a suitable control and design an automated alignment system for CCHM. The modulus of the reconstructed holographic signal was identified as a significant variable for guiding the alignment procedures. From this, we derived the original basic realignment three-dimensional algorithm, which encompasses a unique set of procedures for automated alignment that contains processes for initial and advanced alignment as well as long-term maintenance of microscope tuning. All of these procedures were applied to a functioning microscope and the tested processes were successfully validated. Finally, in such a way, CCHM is enabled to substantially contribute to study of biology, particularly of cancer cells in vitro.

  4. Coherent 2D Spectroscopy and Control of Molecular Complexes

    NASA Astrophysics Data System (ADS)

    Brixner, Tobias

    2007-03-01

    Coherent two-dimensional femtosecond spectroscopy is used to investigate electronic couplings within molecular complexes. Third-order optical response functions are measured in a non-collinear three-pulse photon echo geometry with heterodyne signal detection. In combination with suitable simulations this allows recovering the delocalization of excited-state wavefunctions, their coupling, and the corresponding energy transport pathways, with nanometer spatial and femtosecond temporal resolution. Examples of multichromophoric systems are the FMO and the LH3 light-harvesting complexes from green sulfur bacteria and purple bacteria, respectively, for which energy transfer processes have been determined. Additional challenges arise if one is interested in the spectroscopy of photochemical rather than photophysical processes in molecular complexes: The product yields attained by a single femtosecond laser pulse are often very small, and hence time-dependent signals are hard to measure with good signal-to-noise ratio. In the context of coherent control, this implies that bond-breaking photochemistry in liquids is still difficult despite the many successes of optimal control in gas-phase photodissociation. In a novel accumulative scheme, macroscopic amounts of stable photoproducts are generated in an optimal fashion and with high product detection sensitivity. In connection with time-resolved spectroscopy, the accumulative scheme furthermore provides kinetic information on the pathways of low-efficiency chemical reaction channels. This was applied to investigate the photoconversion of green fluorescent protein.

  5. Coherent control through near-resonant Raman transitions

    SciTech Connect

    Dai Xingcan; Lerch, Eliza-Beth W.; Leone, Stephen R.

    2006-02-15

    The phase of an electronic wave function is shown to play an important role in coherent control experiments. By using a pulse shaping system with a femtosecond laser, we explore the phase relationships among resonant and off-resonant Raman transitions in Li{sub 2} by measuring the phases of the resulting wave packets, or quantum beats. Specific pixels in a liquid-crystal spatial light modulator are used to isolate the resonant and off-resonant portions of the Raman transitions in Li{sub 2}. The off-resonant Raman transitions have an approximately 90 degree sign phase shift with respect to the resonant Raman transition, and there is an approximately 180 degree sign phase shift between the blue-detuned and the red-detuned off-resonant Raman transitions. Calculations using second-order time-dependent perturbation theory for the electronic transitions agree with the experimental results for the laser pulse intensities used here. Interferences between the off-resonant Raman transitions as a function of detuning are used to demonstrate coherent control of the Raman quantum wave packet.

  6. Ultrafast laser based coherent control methods for explosives detection

    SciTech Connect

    Moore, David Steven

    2010-12-06

    The detection of explosives is a notoriously difficult problem, especially at stand-off, due to their (generally) low vapor pressure, environmental and matrix interferences, and packaging. We are exploring Optimal Dynamic Detection of Explosives (ODD-Ex), which exploits the best capabilities of recent advances in laser technology and recent discoveries in optimal shaping of laser pulses for control of molecular processes to significantly enhance the standoff detection of explosives. The core of the ODD-Ex technique is the introduction of optimally shaped laser pulses to simultaneously enhance sensitivity to explosives signatures while dramatically improving specificity, particularly against matrix materials and background interferences. These goals are being addressed by operating in an optimal non-linear fashion, typically with a single shaped laser pulse inherently containing within it coherently locked control and probe subpulses. Recent results will be presented.

  7. Quantum phase gate and controlled entanglement with polar molecules

    SciTech Connect

    Charron, Eric; Keller, Arne; Atabek, Osman; Milman, Perola

    2007-03-15

    We propose an alternative scenario for the generation of entanglement between rotational quantum states of two polar molecules. This entanglement arises from dipole-dipole interaction, and is controlled by a sequence of laser pulses simultaneously exciting both molecules. We study the efficiency of the process, and discuss possible experimental implementations with cold molecules trapped in optical lattices or in solid matrices. Finally, various entanglement detection procedures are presented, and their suitability for these two physical situations is analyzed.

  8. Coherent Structures and Chaos Control in High-Power Microwave Devices

    DTIC Science & Technology

    2006-06-29

    06/29/2006 Final 1 April 2003- 30 March 2006 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER Coherent Structures and Chaos Control in High-Power Microwave...Final Report Coherent Structures and Chaos Control in High-Power Microwave Devices AFOSR Grant No. F49620-03-1-0230 Submitted to: Dr. Arje Nachman...for HPM Device Applications 22 6. References 23 2 Final Report Coherent Structures and Chaos Control in High-Power Microwave Devices AFOSR Grant No

  9. Measurement of a weak transition moment using Coherent Control

    NASA Astrophysics Data System (ADS)

    Antypas, Dionysios

    We have developed a two-pathway Coherent Control technique for measurements of weak optical transition moments. We demonstrate this technique through a measurement of the transition moment of the highly-forbidden magnetic dipole transition between the 6s2S 1/21/2 and 7s2S 1/21/2 states in atomic Cesium. The experimental principle is based on a two-pathway excitation, using two phase-coherent laser fields, a fundamental field at 1079 nm and its second harmonic at 539.5 nm. The IR field induces a strong two-photon transition, while the 539.5 nm field drives a pair of weak one-photon transitions: a Stark-induced transition of controllable strength as well as the magnetic dipole transition. Observations of the interference between these transitions for different Stark-induced transition amplitudes, allow a measurement of the ratio of the magnetic dipole to the Stark-induced moment. The interference between the transitions is controlled by modulation of the phase-delay between the two optical fields. Our determination of the magnetic dipole moment is at the 0.4% level and in good agreement with previous measurements, and serves as a benchmark for our technique and apparatus. We anticipate that with further improvement of the apparatus detection sensitivity, the demonstrated scheme can be used for measurements of the very weak Parity Violation transition moment on the Cesium 6s2 S1/2→7s2 S1/2 transition.

  10. Controlling single-molecule junction conductance by molecular interactions

    PubMed Central

    Kitaguchi, Y.; Habuka, S.; Okuyama, H.; Hatta, S.; Aruga, T.; Frederiksen, T.; Paulsson, M.; Ueba, H.

    2015-01-01

    For the rational design of single-molecular electronic devices, it is essential to understand environmental effects on the electronic properties of a working molecule. Here we investigate the impact of molecular interactions on the single-molecule conductance by accurately positioning individual molecules on the electrode. To achieve reproducible and precise conductivity measurements, we utilize relatively weak π-bonding between a phenoxy molecule and a STM-tip to form and cleave one contact to the molecule. The anchoring to the other electrode is kept stable using a chalcogen atom with strong bonding to a Cu(110) substrate. These non-destructive measurements permit us to investigate the variation in single-molecule conductance under different but controlled environmental conditions. Combined with density functional theory calculations, we clarify the role of the electrostatic field in the environmental effect that influences the molecular level alignment. PMID:26135251

  11. Picosecond Control of Quantum Dot Laser Emission by Coherent Phonons

    NASA Astrophysics Data System (ADS)

    Czerniuk, T.; Wigger, D.; Akimov, A. V.; Schneider, C.; Kamp, M.; Höfling, S.; Yakovlev, D. R.; Kuhn, T.; Reiter, D. E.; Bayer, M.

    2017-03-01

    A picosecond acoustic pulse can be used to control the lasing emission from semiconductor nanostructures by shifting their electronic transitions. When the active medium, here an ensemble of (In,Ga)As quantum dots, is shifted into or out of resonance with the cavity mode, a large enhancement or suppression of the lasing emission can dynamically be achieved. Most interesting, even in the case when gain medium and cavity mode are in resonance, we observe an enhancement of the lasing due to shaking by coherent phonons. In order to understand the interactions of the nonlinearly coupled photon-exciton-phonon subsystems, we develop a semiclassical model and find an excellent agreement between theory and experiment.

  12. Coherent optical control of polarization with a critical metasurface

    NASA Astrophysics Data System (ADS)

    Kang, Ming; Chong, Y. D.

    2015-10-01

    We present a mechanism by which a metamaterial surface, or metasurface, can act as an ideal phase-controlled rotatable linear polarizer. Using coupled-mode theory and the idea of coherent perfect absorption into auxiliary polarization channels, we show how the losses and near-field couplings on the metasurface can be balanced so that, with equal-power linearly polarized beams incident on each side, varying the relative phase rotates the polarization angles of the output beams while maintaining zero ellipticity. The system can be described by a non-Hermitian effective Hamiltonian which is parity-time (P T ) symmetric, although there is no actual gain present; perfect polarization conversion occurs at the eigenfrequencies of this Hamiltonian, and the polarization rotating behavior occurs at the critical point of its P T -breaking transition.

  13. Generation of tunable radially polarized array beams by controllable coherence

    NASA Astrophysics Data System (ADS)

    Wang, Jing; Zhang, Jipeng; Zhu, Shijun; Li, Zhenhua

    2017-05-01

    In this paper, a new method for converting a single radial polarization beam into an arbitrary radially polarized array (RPA) beam such as a radial or rectangular symmetry array in the focal plane by modulating a periodic correlation structure is introduced. The realizability conditions for such source and the beam condition for radiation generated by such source are derived. It is illustrated that both the amplitude and the polarization are controllable by means of initial correlation structure and coherence parameter. Furthermore, by designing the source correlation structure, a tunable NUST-shaped RPA beam is demonstrated, which can find widespread applications in micro-nano engineering. Such a method for generation of arbitrary vector array beams is useful in beam shaping and optical tweezers.

  14. Ion-molecule collision frequencies in gases determined by phase coherent pulsed ICR.

    NASA Technical Reports Server (NTRS)

    Lieder, C. A.; Wien, R. W.; Mciver, R. T., Jr.

    1972-01-01

    The transient method considered is analogous to similar phase coherence experiments performed in NMR and plasma physics. Using a pulsed ion cyclotron resonance (ICR) spectrometer equipped with a trapped ion analyzer cell, gaseous ions are formed by a pulse of an electron beam and then trapped in the cell by the combined effects of the magnetic and electrostatic fields. The results obtained in the experiments indicate that the classical mobility treatment of Wannier (1953) is helpful in the understanding of collision frequencies under the considered conditions.

  15. Toward quantum processing in molecules: a THz-bandwidth coherent memory for light.

    PubMed

    Bustard, Philip J; Lausten, Rune; England, Duncan G; Sussman, Benjamin J

    2013-08-23

    The unusual features of quantum mechanics are enabling the development of technologies not possible with classical physics. These devices utilize nonclassical phenomena in the states of atoms, ions, and solid-state media as the basis for many prototypes. Here we investigate molecular states as a distinct alternative. We demonstrate a memory for light based on storing photons in the vibrations of hydrogen molecules. The THz-bandwidth molecular memory is used to store 100-fs pulses for durations up to ~1 ns, enabling ~10(4) operational time bins. The results demonstrate the promise of molecules for constructing compact ultrafast quantum photonic technologies.

  16. Dynamic Colloidal Molecules Maneuvered by Light-Controlled Janus Micromotors.

    PubMed

    Gao, Yirong; Mou, Fangzhi; Feng, Yizheng; Che, Shengping; Li, Wei; Xu, Leilei; Guan, Jianguo

    2017-07-12

    In this work, we propose and demonstrate a dynamic colloidal molecule that is capable of moving autonomously and performing swift, reversible, and in-place assembly dissociation in a high accuracy by manipulating a TiO2/Pt Janus micromotor with light irradiation. Due to the efficient motion of the TiO2/Pt Janus motor and the light-switchable electrostatic interactions between the micromotor and colloidal particles, the colloidal particles can be captured and assembled one by one on the fly, subsequently forming into swimming colloidal molecules by mimicking space-filling models of simple molecules with central atoms. The as-demonstrated dynamic colloidal molecules have a configuration accurately controlled and stabilized by regulating the time-dependent intensity of UV light, which controls the stop-and-go motion of the colloidal molecules. The dynamic colloidal molecules are dissociated when the light irradiation is turned off due to the disappearance of light-switchable electrostatic interaction between the motor and the colloidal particles. The strategy for the assembly of dynamic colloidal molecules is applicable to various charged colloidal particles. The simulated optical properties of a dynamic colloidal molecule imply that the results here may provide a novel approach for in-place building functional microdevices, such as microlens arrays, in a swift and reversible manner.

  17. Controllable double tunneling induced transparency and solitons formation in a quantum dot molecule.

    PubMed

    She, Yanchao; Zheng, Xuejun; Wang, Denglong; Zhang, Weixi

    2013-07-15

    We consider the coupling effect between interdot tunneling coupling and external optical control field to study the linear optical property and the formation of temporal optical solitons in a quantum dot molecules system, analytically. The results show that the double tunneling induced transparency (TIT) windows are appeared in the absorption curve of probe field because of the formation of dynamic Stark splitting and quantum destructive interference effect from the two upper levels. Interestingly, the width of the TIT window becomes wider with the increasing intensity of the optical control field. We also find that the Kerr nonlinear effect of the probe field can be modulated effectively through coherent control both the control field and the interdot tunneling coupling in this system. Meanwhile, we demonstrate that the formation of dark or bright solitons can be practical regulated by varying the intensity of the optical control field.

  18. Controlling the magnetism of adsorbed metal-organic molecules.

    PubMed

    Kuch, Wolfgang; Bernien, Matthias

    2017-01-18

    Gaining control on the size or the direction of the magnetic moment of adsorbed metal-organic molecules constitutes an important step towards the realization of a surface-mounted molecular spin electronics. Such control can be gained by taking advantage of interactions of the molecule's magnetic moment with the environment. The paramagnetic moments of adsorbed metal-organic molecules, for example, can be controlled by the interaction with magnetically ordered substrates. Metalloporphyrins and -phthalocyanines display a quasi-planar geometry, allowing the central metal ion to interact with substrate electronic states. This can lead to magnetic coupling with a ferromagnetic or even antiferromagnetic substrate. The molecule-substrate coupling can be mediated and controlled by insertion layers such as oxygen atoms, graphene, or nonmagnetic metal layers. Control on the magnetic properties of adsorbed metalloporphyrins or -phthalocyanines can also be gained by on-surface chemical modification of the molecules. The magnetic moment or the magnetic coupling to ferromagnetic substrates can be changed by adsorption and thermal desorption of small molecules that interact with the fourfold-coordinated metal center via the remaining axial coordination site. Spin-crossover molecules, which possess a metastable spin state that can be switched by external stimuli such as temperature or light, are another promising class of candidates for control of magnetic properties. However, the immobilization of such molecules on a solid surface often results in a quench of the spin transition due to the interaction with the substrate. We present examples of Fe(II) spin-crossover complexes in direct contact with a solid surface that undergo a reversible spin-crossover transition as a function of temperature, by illumination with visible light, or can be switched by the tip of a scanning tunneling microscope.

  19. Probing Electron Correlations in Molecules by Two-Dimensional Coherent Optical Spectroscopy

    PubMed Central

    Li, Zhenyu; Abramavicius, Darius; Mukamel, Shaul

    2010-01-01

    The nonlinear optical signal generated in phenol by three femtosecond pulses with wavevectors k1, k2, and k3 in the phase-matching direction k1 + k2 − k3 is simulated. This two-dimensional coherent spectroscopy (2DCS) signal has a rich pattern containing information on double-excitation states. The signal vanishes for uncorrelated electrons due to interference among quantum pathways and, thus, provides direct signatures of correlated many-electron wavefunctions. This is illustrated by the very different 2DCS signals predicted by two levels of electronic structure calculations: state-averaged complete active space self-consistent field (SA-CASSCF) and multistate multiconfigurational second-order perturbation theory (MS-CASPT2). PMID:18288841

  20. Towards noninvasive drug distribution in tissues: coherent Raman microspectroscopy of chiral molecules

    NASA Astrophysics Data System (ADS)

    Petrov, Georgi I.; Yakovlev, Vladislav V.

    2017-02-01

    Many biologically active molecules are chiral. Many drugs, which are currently in use, are supplied as an equimolar mixture of enantiomers. Although they have the same chemical structure, i.e. are not distinguishable by conventional Raman spectroscopy, most isomers of chiral drugs exhibit marked differences in biological activities such as pharmacology, toxicology, pharmacokinetics, metabolism, etc. In this report we introduced a new spectroscopic tool to extend nonlinear Raman spectroscopy to chiral substances.

  1. Coherent control of a classical nanomechanical two-level system

    NASA Astrophysics Data System (ADS)

    Faust, T.; Rieger, J.; Seitner, M. J.; Kotthaus, J. P.; Weig, E. M.

    2013-08-01

    The Bloch sphere is a generic picture describing the coherent dynamics of coupled classical or quantum-mechanical two-level systems under the control of electromagnetic fields. It is commonly applied to systems such as spin ensembles, atoms, quantum dots and superconducting circuits. The underlying Bloch equations describe the state evolution of the two-level system and allow the characterization of both energy and phase relaxation processes. Here we realize a classical nanomechanical two-level system driven by radiofrequency signals. It is based on the two orthogonal fundamental flexural modes of a high-quality-factor nanostring resonator that are strongly coupled by dielectric gradient fields. Full Bloch sphere control is demonstrated by means of Rabi, Ramsey and Hahn echo experiments. Furthermore, we determine the energy relaxation time T1and phase relaxation times T2 and T2*, and find them all to be equal. Thus decoherence is dominated by energy relaxation, implying that not only T1 but also T2 can be increased by engineering larger mechanical quality factors.

  2. Closed loop coherent control of electronic transitions in gallium arsenide.

    PubMed

    Singha, Sima; Hu, Zhan; Gordon, Robert J

    2011-06-16

    A genetic algorithm was used to control the photoluminesce-nce (PL) from GaAs(100). A spatial light modulator (SLM) used feedback from the emission to optimize the spectral phase profile of an ultrashort laser pulse. Most of the experiments were performed using a sine phase function to optimize the integrated PL spectrum over a specified wavelength range, with the amplitude and period of the phase function treated as genetic parameters. An order of magnitude increase in signal was achieved after only one generation, and an optimized waveform, consisting of three equally spaced pulses approximately 0.8 ps apart, was obtained after 15 generations. The effects of fluence, polarization, relative phase of the subpulses, and spectral range of the optimized PL were investigated. In addition, preliminary experiments were performed using the phases of individual pixels of the SLM as genetic variables. The PL spectrum is identified with recombination of electron-hole pairs in the L-valley of the Brillouin zone. Control is achieved by coherent manipulation of plasma electrons. It is proposed that hot electrons excite lattice phonons, which in turn scatter carriers into the L-valley.

  3. Mechanical control of spin states in single molecules

    NASA Astrophysics Data System (ADS)

    Parks, J. J.; Champagne, A. R.; Costi, T. A.; Pasupathy, A. N.; Shum, W. W.; Neuscamman, E.; Chan, G. K.-L.; Abruña, H. D.; Ralph, D. C.

    2010-03-01

    We study individual Co(tpy-SH)2 complexes by connecting them within mechanically controllable break-junction devices that allow us to controllably stretch the molecule while measuring its electrical conductance. At low temperature, this molecule produces the Kondo effect, observed as a peak in the conductance at zero bias. We find that as a function of stretching the Kondo peak splits in two, in distinct contrast to behavior observed in spin-1/2 molecules. The temperature dependence of the Kondo signal for the unstretched molecule is in agreement with the scaling prediction for an underscreened S = 1 Kondo effect. The splitting of the Kondo resonance by mechanical stretching can be explained by a spin-orbit-induced lifting of the degeneracy of the S = 1 triplet upon distortion from octahedral symmetry of the Co ion. We observe evidence of the resultant spin anisotropy in the magnetic-field dependence of the Kondo peaks.

  4. Controlling the magnetism of adsorbed metal-organic molecules

    NASA Astrophysics Data System (ADS)

    Kuch, Wolfgang; Bernien, Matthias

    2017-01-01

    Gaining control on the size or the direction of the magnetic moment of adsorbed metal-organic molecules constitutes an important step towards the realization of a surface-mounted molecular spin electronics. Such control can be gained by taking advantage of interactions of the molecule’s magnetic moment with the environment. The paramagnetic moments of adsorbed metal-organic molecules, for example, can be controlled by the interaction with magnetically ordered substrates. Metalloporphyrins and -phthalocyanines display a quasi-planar geometry, allowing the central metal ion to interact with substrate electronic states. This can lead to magnetic coupling with a ferromagnetic or even antiferromagnetic substrate. The molecule-substrate coupling can be mediated and controlled by insertion layers such as oxygen atoms, graphene, or nonmagnetic metal layers. Control on the magnetic properties of adsorbed metalloporphyrins or -phthalocyanines can also be gained by on-surface chemical modification of the molecules. The magnetic moment or the magnetic coupling to ferromagnetic substrates can be changed by adsorption and thermal desorption of small molecules that interact with the fourfold-coordinated metal center via the remaining axial coordination site. Spin-crossover molecules, which possess a metastable spin state that can be switched by external stimuli such as temperature or light, are another promising class of candidates for control of magnetic properties. However, the immobilization of such molecules on a solid surface often results in a quench of the spin transition due to the interaction with the substrate. We present examples of Fe(II) spin-crossover complexes in direct contact with a solid surface that undergo a reversible spin-crossover transition as a function of temperature, by illumination with visible light, or can be switched by the tip of a scanning tunneling microscope.

  5. Controlling the orbital sequence in individual Cu-phthalocyanine molecules.

    PubMed

    Uhlmann, C; Swart, I; Repp, J

    2013-02-13

    We report on the controlled change of the energetic ordering of molecular orbitals. Negatively charged copper(II)phthalocyanine on NaCl/Cu(100) undergoes a Jahn-Teller distortion that lifts the degeneracy of two frontier orbitals. The energetic order of the levels can be controlled by Au and Ag atoms in the vicinity of the molecule. As only one of the states is occupied, the control of the energetic order is accompanied by bistable changes of the charge distribution inside the molecule, rendering it a bistable switch.

  6. Holography and coherent diffraction with low-energy electrons: A route towards structural biology at the single molecule level.

    PubMed

    Latychevskaia, Tatiana; Longchamp, Jean-Nicolas; Escher, Conrad; Fink, Hans-Werner

    2015-12-01

    The current state of the art in structural biology is led by NMR, X-ray crystallography and TEM investigations. These powerful tools however all rely on averaging over a large ensemble of molecules. Here, we present an alternative concept aiming at structural analysis at the single molecule level. We show that by combining electron holography and coherent diffraction imaging estimations concerning the phase of the scattered wave become needless as the phase information is extracted from the data directly and unambiguously. Performed with low-energy electrons the resolution of this lens-less microscope is just limited by the De Broglie wavelength of the electron wave and the numerical aperture, given by detector geometry. In imaging freestanding graphene, a resolution of 2Å has been achieved revealing the 660.000 unit cells of the graphene sheet from a single data set. Once applied to individual biomolecules the method shall ultimately allow for non-destructive imaging and imports the potential to distinguish between different conformations of proteins with atomic resolution.

  7. Flexible coherent control of plasmonic spin-Hall effect

    PubMed Central

    Xiao, Shiyi; Zhong, Fan; Liu, Hui; Zhu, Shining; Li, Jensen

    2015-01-01

    The surface plasmon polariton is an emerging candidate for miniaturizing optoelectronic circuits. Recent demonstrations of polarization-dependent splitting using metasurfaces, including focal-spot shifting and unidirectional propagation, allow us to exploit the spin degree of freedom in plasmonics. However, further progress has been hampered by the inability to generate more complicated and independent surface plasmon profiles for two incident spins, which work coherently together for more flexible and tunable functionalities. Here by matching the geometric phases of the nano-slots on silver to specific superimpositions of the inward and outward surface plasmon profiles for the two spins, arbitrary spin-dependent orbitals can be generated in a slot-free region. Furthermore, motion pictures with a series of picture frames can be assembled and played by varying the linear polarization angle of incident light. This spin-enabled control of orbitals is potentially useful for tip-free near-field scanning microscopy, holographic data storage, tunable plasmonic tweezers, and integrated optical components. PMID:26415636

  8. Flexible coherent control of plasmonic spin-Hall effect

    NASA Astrophysics Data System (ADS)

    Xiao, Shiyi; Zhong, Fan; Liu, Hui; Zhu, Shining; Li, Jensen

    2015-09-01

    The surface plasmon polariton is an emerging candidate for miniaturizing optoelectronic circuits. Recent demonstrations of polarization-dependent splitting using metasurfaces, including focal-spot shifting and unidirectional propagation, allow us to exploit the spin degree of freedom in plasmonics. However, further progress has been hampered by the inability to generate more complicated and independent surface plasmon profiles for two incident spins, which work coherently together for more flexible and tunable functionalities. Here by matching the geometric phases of the nano-slots on silver to specific superimpositions of the inward and outward surface plasmon profiles for the two spins, arbitrary spin-dependent orbitals can be generated in a slot-free region. Furthermore, motion pictures with a series of picture frames can be assembled and played by varying the linear polarization angle of incident light. This spin-enabled control of orbitals is potentially useful for tip-free near-field scanning microscopy, holographic data storage, tunable plasmonic tweezers, and integrated optical components.

  9. Dissipation and coherent control in nano-optomechanical systems

    NASA Astrophysics Data System (ADS)

    Fong, King Yan

    system. Lastly, a hybrid opto-electro-mechanical system combining an optomechanical resonator with microwave piezoelectric actuation is developed. This integration of optomechanics with microwaves provides an extra degree of freedom for coherent control of the system. Enabled by this strong piezoelectric actuation, nonlinear operation of optomechanical system which manifests as multi-phonon scattering is demonstrated. Our demonstration shows that the strong coherent microwave drive can be a useful tool for studying the nonlinear dynamics of optomechanical systems driven in large amplitude. Examining the noise characteristic in this regime will be an interesting topic for further study.

  10. Small-molecule control of protein function through Staudinger reduction

    NASA Astrophysics Data System (ADS)

    Luo, Ji; Liu, Qingyang; Morihiro, Kunihiko; Deiters, Alexander

    2016-11-01

    Using small molecules to control the function of proteins in live cells with complete specificity is highly desirable, but challenging. Here we report a small-molecule switch that can be used to control protein activity. The approach uses a phosphine-mediated Staudinger reduction to activate protein function. Genetic encoding of an ortho-azidobenzyloxycarbonyl amino acid using a pyrrolysyl transfer RNA synthetase/tRNACUA pair in mammalian cells enables the site-specific introduction of a small-molecule-removable protecting group into the protein of interest. Strategic placement of this group renders the protein inactive until deprotection through a bioorthogonal Staudinger reduction delivers the active wild-type protein. This developed methodology was applied to the conditional control of several cellular processes, including bioluminescence (luciferase), fluorescence (enhanced green fluorescent protein), protein translocation (nuclear localization sequence), DNA recombination (Cre) and gene editing (Cas9).

  11. Method and apparatus for single-stepping coherence events in a multiprocessor system under software control

    DOEpatents

    Blumrich, Matthias A.; Salapura, Valentina

    2010-11-02

    An apparatus and method are disclosed for single-stepping coherence events in a multiprocessor system under software control in order to monitor the behavior of a memory coherence mechanism. Single-stepping coherence events in a multiprocessor system is made possible by adding one or more step registers. By accessing these step registers, one or more coherence requests are processed by the multiprocessor system. The step registers determine if the snoop unit will operate by proceeding in a normal execution mode, or operate in a single-step mode.

  12. Time-delayed quantum coherent Pyragas feedback control of photon squeezing in a degenerate parametric oscillator

    NASA Astrophysics Data System (ADS)

    Kraft, Manuel; Hein, Sven M.; Lehnert, Judith; Schöll, Eckehard; Hughes, Stephen; Knorr, Andreas

    2016-08-01

    Quantum coherent feedback control is a measurement-free control method fully preserving quantum coherence. In this paper we show how time-delayed quantum coherent feedback can be used to control the degree of squeezing in the output field of a cavity containing a degenerate parametric oscillator. We focus on the specific situation of Pyragas-type feedback control where time-delayed signals are fed back directly into the quantum system. Our results show how time-delayed feedback can enhance or decrease the degree of squeezing as a function of time delay and feedback strength.

  13. Control of coherence transfer via tunneling in quadruple and multiple quantum dots

    NASA Astrophysics Data System (ADS)

    Tian, Si-Cong; Xing, En-Bo; Wan, Ren-Gang; Wang, Chun-Liang; Wang, Li-Jie; Shu, Shi-Li; Tong, Cun-Zhu; Wang, Li-Jun

    2016-12-01

    Transfer and manipulation of coherence among the ground state and indirect exciton states via tunneling in quadruple and multiple quantum dots is analyzed. By applying suitable amplitudes and sequences of the pump and tunneling pulses, a complete transfer of coherence or an arbitrary distribution of coherence of multiple states can be realized. The method, which is an adiabatic passage process, is different from previous works on quantum dot molecules in the way that the population can transfer from the ground state to the indirect exciton states without populating the direct exciton state, and thus no spontaneous emission occurs. This investigation can provide further insight to help the experimental development of coherence transfer in semiconductor structures, and may have potential applications in quantum information processing.

  14. Coherent control of atomic qubits by non-classical light

    NASA Astrophysics Data System (ADS)

    Balybin, Stepan N.; Sharapova, Polina R.; Tikhonova, Olga V.

    2017-05-01

    In this work we investigate analytically the interaction between a quantum atomic model system and non-classical light and suggest a method to transfer phase information from the field qubit to the atomic one. A rather realistic atomic system with bound levels and the continuum is considered. The influence of ionization on the possibility of the phase transfer is analyzed. The atomic state formed during the interaction is shown to be controlled by the relative phase of the field qubit. The possibility to measure the transferred phase is demonstrated. Contribution to the Topical Issue "Many Particle Spectroscopy of Atoms, Molecules, Clusters and Surfaces", edited by A.N. Grum-Grzhimailo, E.V. Gryzlova, Yu V. Popov, and A.V. Solov'yov.

  15. EDITORIAL: Quantum control theory for coherence and information dynamics Quantum control theory for coherence and information dynamics

    NASA Astrophysics Data System (ADS)

    Viola, Lorenza; Tannor, David

    2011-08-01

    Precisely characterizing and controlling the dynamics of realistic open quantum systems has emerged in recent years as a key challenge across contemporary quantum sciences and technologies, with implications ranging from physics, chemistry and applied mathematics to quantum information processing (QIP) and quantum engineering. Quantum control theory aims to provide both a general dynamical-system framework and a constructive toolbox to meet this challenge. The purpose of this special issue of Journal of Physics B: Atomic, Molecular and Optical Physics is to present a state-of-the-art account of recent advances and current trends in the field, as reflected in two international meetings that were held on the subject over the last summer and which motivated in part the compilation of this volume—the Topical Group: Frontiers in Open Quantum Systems and Quantum Control Theory, held at the Institute for Theoretical Atomic, Molecular and Optical Physics (ITAMP) in Cambridge, Massachusetts (USA), from 1-14 August 2010, and the Safed Workshop on Quantum Decoherence and Thermodynamics Control, held in Safed (Israel), from 22-27 August 2010. Initial developments in quantum control theory date back to (at least) the early 1980s, and have been largely inspired by the well-established mathematical framework for classical dynamical systems. As the above-mentioned meetings made clear, and as the burgeoning body of literature on the subject testifies, quantum control has grown since then well beyond its original boundaries, and has by now evolved into a highly cross-disciplinary field which, while still fast-moving, is also entering a new phase of maturity, sophistication, and integration. Two trends deserve special attention: on the one hand, a growing emphasis on control tasks and methodologies that are specifically motivated by QIP, in addition and in parallel to applications in more traditional areas where quantum coherence is nevertheless vital (such as, for instance

  16. Coherent control of a strongly driven silicon vacancy optical transition in diamond

    NASA Astrophysics Data System (ADS)

    Zhou, Yu; Rasmita, Abdullah; Li, Ke; Xiong, Qihua; Aharonovich, Igor; Gao, Wei-Bo

    2017-02-01

    The ability to prepare, optically read out and coherently control single quantum states is a key requirement for quantum information processing. Optically active solid-state emitters have emerged as promising candidates with their prospects for on-chip integration as quantum nodes and sources of coherent photons connecting these nodes. Under a strongly driving resonant laser field, such quantum emitters can exhibit quantum behaviour such as Autler-Townes splitting and the Mollow triplet spectrum. Here we demonstrate coherent control of a strongly driven optical transition in silicon vacancy centre in diamond. Rapid optical detection of photons enabled the observation of time-resolved coherent Rabi oscillations and the Mollow triplet spectrum. Detection with a probing transition further confirmed Autler-Townes splitting generated by a strong laser field. The coherence time of the emitted photons is comparable to its lifetime and robust under a very strong driving field, which is promising for the generation of indistinguishable photons.

  17. Coherent control of a strongly driven silicon vacancy optical transition in diamond

    PubMed Central

    Zhou, Yu; Rasmita, Abdullah; Li, Ke; Xiong, Qihua; Aharonovich, Igor; Gao, Wei-bo

    2017-01-01

    The ability to prepare, optically read out and coherently control single quantum states is a key requirement for quantum information processing. Optically active solid-state emitters have emerged as promising candidates with their prospects for on-chip integration as quantum nodes and sources of coherent photons connecting these nodes. Under a strongly driving resonant laser field, such quantum emitters can exhibit quantum behaviour such as Autler–Townes splitting and the Mollow triplet spectrum. Here we demonstrate coherent control of a strongly driven optical transition in silicon vacancy centre in diamond. Rapid optical detection of photons enabled the observation of time-resolved coherent Rabi oscillations and the Mollow triplet spectrum. Detection with a probing transition further confirmed Autler–Townes splitting generated by a strong laser field. The coherence time of the emitted photons is comparable to its lifetime and robust under a very strong driving field, which is promising for the generation of indistinguishable photons. PMID:28218237

  18. Assessment of radiation damage in single-shot coherent diffraction of DNA molecules by an extreme-ultraviolet free-electron laser.

    PubMed

    Park, Jaehyun; Nam, Daewoong; Kohmura, Yoshiki; Nagasono, Mitsuru; Jeon, Yongmoon; Lee, Jong-Bong; Ishikawa, Tetsuya; Song, Changyong

    2012-10-01

    We have investigated the progress of structural distortions in DNA molecules by single-shot coherent diffraction using extreme-ultraviolet radiation from a free-electron laser. A speckle pattern of DNA molecules was successfully acquired using photons in a single pulse with a 100 fs pulse width. The radiation damage was assessed by a cross correlation, revealing that the first exposure has significantly deformed most of the original structures. Molecules were not completely destroyed by the first single-shot exposure and underwent subsequent distortions through continued exposure, until eventually deforming into a radiation-hard structure.

  19. Activation of coherent lattice phonon following ultrafast molecular spin-state photo-switching: A molecule-to-lattice energy transfer

    PubMed Central

    Marino, A.; Cammarata, M.; Matar, S. F.; Létard, J.-F.; Chastanet, G.; Chollet, M.; Glownia, J. M.; Lemke, H. T.; Collet, E.

    2015-01-01

    We combine ultrafast optical spectroscopy with femtosecond X-ray absorption to study the photo-switching dynamics of the [Fe(PM-AzA)2(NCS)2] spin-crossover molecular solid. The light-induced excited spin-state trapping process switches the molecules from low spin to high spin (HS) states on the sub-picosecond timescale. The change of the electronic state (<50 fs) induces a structural reorganization of the molecule within 160 fs. This transformation is accompanied by coherent molecular vibrations in the HS potential and especially a rapidly damped Fe-ligand breathing mode. The time-resolved studies evidence a delayed activation of coherent optical phonons of the lattice surrounding the photoexcited molecules. PMID:26798836

  20. Nanoscale Assemblies of Small Molecules Control the Fate of Cells.

    PubMed

    Shi, Junfeng; Xu, Bing

    2015-10-01

    Being driven by non-covalent interactions, the formation of functional assemblies (or aggregates) of small molecules at nanoscale is a more common process in water than one would think. While most efforts on self-assembly in cellular environment concentrate on the assemblies of proteins (e.g., microtubules or amyloid fibers), nanoscale assemblies of small molecules are emerging functional entities that exhibit important biological function in cellular environments. This review describes the increasing efforts on the exploration of nanoscale assemblies of small molecules that largely originate from the serendipitous observations in research fields other than nanoscience and technology. Specifically, we describe that nanoscale assemblies of small molecules exhibit unique biological functions in extracellular and intracellular environment, thus inducing various cellular responses, like causing cell death or promoting cell proliferation. We first survey certain common feature of nanoscale molecular assemblies, then discuss several specific examples, such as, nanoscale assemblies of small peptides accumulated in the cells for selectively inhibiting cancer cells via promiscuous interactions with proteins, and nanoscale assemblies of a glycoconjugate for promoting the proliferation of stem cells or for suppressing immune responses. Subsequently, we emphasize the spatiotemporal control of nanoscale assemblies for controlling the cell fate, particularly illustrate a paradigm-shifting approach-enzyme-instructed self-assembly (EISA), that is, the integration of enzymatic reaction and self-assembly-for generating nanoscale assemblies from innocuous monomers for selectively inhibiting cancer cells. Moreover, we introduce a convenient assay for proteomic study of the proteins that interact with nanoscale assemblies of small molecules in cellular environment. Furthermore, we introduce the use of ligand-receptor interaction to catalyze the formation of nanoscale assemblies. By

  1. Perspective: Ultracold molecules and the dawn of cold controlled chemistry

    NASA Astrophysics Data System (ADS)

    Balakrishnan, N.

    2016-10-01

    Ultracold molecules offer unprecedented opportunities for the controlled interrogation of molecular events, including chemical reactivity in the ultimate quantum regime. The proliferation of methods to create, cool, and confine them has allowed the investigation of a diverse array of molecular systems and chemical reactions at temperatures where only a single partial wave contributes. Here we present a brief account of recent progress on the experimental and theoretical fronts on cold and ultracold molecules and the opportunities and challenges they provide for a fundamental understanding of bimolecular chemical reaction dynamics.

  2. Attosecond-recollision-controlled selective fragmentation of polyatomic molecules.

    PubMed

    Xie, Xinhua; Doblhoff-Dier, Katharina; Roither, Stefan; Schöffler, Markus S; Kartashov, Daniil; Xu, Huailiang; Rathje, Tim; Paulus, Gerhard G; Baltuška, Andrius; Gräfe, Stefanie; Kitzler, Markus

    2012-12-14

    Control over various fragmentation reactions of a series of polyatomic molecules (acetylene, ethylene, 1,3-butadiene) by the optical waveform of intense few-cycle laser pulses is demonstrated experimentally. We show both experimentally and theoretically that the responsible mechanism is inelastic ionization from inner-valence molecular orbitals by recolliding electron wave packets, whose recollision energy in few-cycle ionizing laser pulses strongly depends on the optical waveform. Our work demonstrates an efficient and selective way of predetermining fragmentation and isomerization reactions in polyatomic molecules on subfemtosecond time scales.

  3. Coherent phase control of internal conversion in pyrazine

    SciTech Connect

    Gordon, Robert J. Singha, Sima; Zhao, Youbo; Hu, Zhan; Seideman, Tamar; Sukharev, Maxim

    2015-04-14

    Shaped ultrafast laser pulses were used to study and control the ionization dynamics of electronically excited pyrazine in a pump and probe experiment. For pump pulses created without feedback from the product signal, the ion growth curve (the parent ion signal as a function of pump/probe delay) was described quantitatively by the classical rate equations for internal conversion of the S{sub 2} and S{sub 1} states. Very different, non-classical behavior was observed when a genetic algorithm (GA) employing phase-only modulation was used to minimize the ion signal at some pre-determined target time, T. Two qualitatively different control mechanisms were identified for early (T < 1.5 ps) and late (T > 1.5 ps) target times. In the former case, the ion signal was largely suppressed for t < T, while for t ≫ T, the ion signal produced by the GA-optimized pulse and a transform limited (TL) pulse coalesced. In contrast, for T > 1.5 ps, the ion growth curve followed the classical rate equations for t < T, while for t ≫ T, the quantum yield for the GA-optimized pulse was much smaller than for a TL pulse. We interpret the first type of behavior as an indication that the wave packet produced by the pump laser is localized in a region of the S{sub 2} potential energy surface where the vertical ionization energy exceeds the probe photon energy, whereas the second type of behavior may be described by a reduced absorption cross section for S{sub 0} → S{sub 2} followed by incoherent decay of the excited molecules. Amplitude modulation observed in the spectrum of the shaped pulse may have contributed to the control mechanism, although this possibility is mitigated by the very small focal volume of the probe laser.

  4. Coherent phase control of internal conversion in pyrazine

    NASA Astrophysics Data System (ADS)

    Gordon, Robert J.; Hu, Zhan; Seideman, Tamar; Singha, Sima; Sukharev, Maxim; Zhao, Youbo

    2015-04-01

    Shaped ultrafast laser pulses were used to study and control the ionization dynamics of electronically excited pyrazine in a pump and probe experiment. For pump pulses created without feedback from the product signal, the ion growth curve (the parent ion signal as a function of pump/probe delay) was described quantitatively by the classical rate equations for internal conversion of the S2 and S1 states. Very different, non-classical behavior was observed when a genetic algorithm (GA) employing phase-only modulation was used to minimize the ion signal at some pre-determined target time, T. Two qualitatively different control mechanisms were identified for early (T < 1.5 ps) and late (T > 1.5 ps) target times. In the former case, the ion signal was largely suppressed for t < T, while for t ≫ T, the ion signal produced by the GA-optimized pulse and a transform limited (TL) pulse coalesced. In contrast, for T > 1.5 ps, the ion growth curve followed the classical rate equations for t < T, while for t ≫ T, the quantum yield for the GA-optimized pulse was much smaller than for a TL pulse. We interpret the first type of behavior as an indication that the wave packet produced by the pump laser is localized in a region of the S2 potential energy surface where the vertical ionization energy exceeds the probe photon energy, whereas the second type of behavior may be described by a reduced absorption cross section for S0 → S2 followed by incoherent decay of the excited molecules. Amplitude modulation observed in the spectrum of the shaped pulse may have contributed to the control mechanism, although this possibility is mitigated by the very small focal volume of the probe laser.

  5. Comprehension through explanation as the interaction of the brain’s coherence and cognitive control networks

    PubMed Central

    Moss, Jarrod; Schunn, Christian D.

    2015-01-01

    Discourse comprehension processes attempt to produce an elaborate and well-connected representation in the reader’s mind. A common network of regions including the angular gyrus, posterior cingulate, and dorsal frontal cortex appears to be involved in constructing coherent representations in a variety of tasks including social cognition tasks, narrative comprehension, and expository text comprehension. Reading strategies that require the construction of explicit inferences are used in the present research to examine how this coherence network interacts with other brain regions. A psychophysiological interaction analysis was used to examine regions showing changed functional connectivity with this coherence network when participants were engaged in either a non-inferencing reading strategy, paraphrasing, or a strategy requiring coherence-building inferences, self-explanation. Results of the analysis show that the coherence network increases in functional connectivity with a cognitive control network that may be specialized for the manipulation of semantic representations and the construction of new relations among these representations. PMID:26557066

  6. Heterodyne coherent anti-Stokes Raman scattering by the phase control of its intrinsic background

    SciTech Connect

    Wang Xi; Wang Kai; Welch, George R.; Sokolov, Alexei V.

    2011-08-15

    We demonstrate the use of femtosecond laser pulse shaping for precise control of the interference between the coherent anti-Stokes Raman scattering (CARS) signal and the coherent nonresonant background generated within the same sample volume. Our technique is similar to heterodyne detection with the coherent background playing the role of the local oscillator field. In our experiment, we first apply two ultrashort (near-transform-limited) femtosecond pump and Stokes laser pulses to excite coherent molecular oscillations within a sample. After a short and controllable delay, we then apply a laser pulse that scatters off of these oscillations to produce the CARS signal. By making fine adjustments to the probe field spectral profile, we vary the relative phase between the Raman-resonant signal and the nonresonant background, and we observe a varying spectral interference pattern. These controlled variations of the measured pattern reveal the phase information within the Raman spectrum.

  7. Communication: Conditions for one-photon coherent phase control in isolated and open quantum systems

    SciTech Connect

    Spanner, Michael; Arango, Carlos A.; Brumer, Paul

    2010-10-21

    Coherent control of observables using the phase properties of weak light that induces one-photon transitions is considered. Measurable properties are shown to be categorizable as either class A, where control is not possible, or class B, where control is possible. Using formal arguments, we show that phase control in open systems can be environmentally assisted.

  8. Coherent control of Floquet-mode dressed plasmon polaritons

    NASA Astrophysics Data System (ADS)

    Frank, Regine

    2012-05-01

    We study the coherent properties of plasmon polaritons optically excited on periodic nanostructures. The gold grains are coupled to a single-mode photonic waveguide which exhibits a dramatically reduced transmission originating from the derived quantum interference. With a nonequilibrium description of Floquet-dressed polaritons we demonstrate the switching of light transmission through the waveguide due to sheer existence of intraband transitions in gold from right above the Fermi level driven by the external laser light.

  9. Adhesion Molecules: Master Controllers of the Circulatory System.

    PubMed

    Schmidt, Eric P; Kuebler, Wolfgang M; Lee, Warren L; Downey, Gregory P

    2016-03-15

    This manuscript will review our current understanding of cellular adhesion molecules (CAMs) relevant to the circulatory system, their physiological role in control of vascular homeostasis, innate and adaptive immune responses, and their importance in pathophysiological (disease) processes such as acute lung injury, atherosclerosis, and pulmonary hypertension. This is a complex and rapidly changing area of research that is incompletely understood. By design, we will begin with a brief overview of the structure and classification of the major groups of adhesion molecules and their physiological functions including cellular adhesion and signaling. The role of specific CAMs in the process of platelet aggregation and hemostasis and leukocyte adhesion and transendothelial migration will be reviewed as examples of the complex and cooperative interplay between CAMs during physiological and pathophysiological processes. The role of the endothelial glycocalyx and the glycobiology of this complex system related to inflammatory states such as sepsis will be reviewed. We will then focus on the role of adhesion molecules in the pathogenesis of specific disease processes involving the lungs and cardiovascular system. The potential of targeting adhesion molecules in the treatment of immune and inflammatory diseases will be highlighted in the relevant sections throughout the manuscript.

  10. Coherent phonon control via electron-lattice interaction in ferromagnetic Co/Pt multilayers

    PubMed Central

    Kim, Chul Hoon; Shim, Je-Ho; Lee, Kyung Min; Jeong, Jong-Ryul; Kim, Dong-Hyun; Kim, Dong Eon

    2016-01-01

    The manipulation of coherent phonons in condensed systems has attracted fundamental interest, particularly for its applications to future devices. We demonstrate that a coherent phonon in Co/Pt nano-multilayer can be quantitatively controlled via electron-lattice coupling, specifically by changing the multilayer repeat number. To that end, systematic measurement of the time-resolved reflectivity and magneto-optical Kerr effect in Co/Pt multilayers was performed. The coherent phonon frequency was observed to be shifted with the change of the multilayer repeat number. This shift could be clearly explained based on the two-temperature model. Detailed analysis indicated that the lattice heat capacity and electron-lattice coupling strength are linearly dependent on the repeat number of the periodic multilayer structures. Accessing the control of coherent phonons using nanostructures opens a new avenue for advanced phonon-engineering applications. PMID:26928846

  11. Coherent phonon optics in a chip with an electrically controlled active device.

    PubMed

    Poyser, Caroline L; Akimov, Andrey V; Campion, Richard P; Kent, Anthony J

    2015-02-05

    Phonon optics concerns operations with high-frequency acoustic waves in solid media in a similar way to how traditional optics operates with the light beams (i.e. photons). Phonon optics experiments with coherent terahertz and sub-terahertz phonons promise a revolution in various technical applications related to high-frequency acoustics, imaging, and heat transport. Previously, phonon optics used passive methods for manipulations with propagating phonon beams that did not enable their external control. Here we fabricate a phononic chip, which includes a generator of coherent monochromatic phonons with frequency 378 GHz, a sensitive coherent phonon detector, and an active layer: a doped semiconductor superlattice, with electrical contacts, inserted into the phonon propagation path. In the experiments, we demonstrate the modulation of the coherent phonon flux by an external electrical bias applied to the active layer. Phonon optics using external control broadens the spectrum of prospective applications of phononics on the nanometer scale.

  12. Coherent phonon optics in a chip with an electrically controlled active device

    PubMed Central

    Poyser, Caroline L.; Akimov, Andrey V.; Campion, Richard P.; Kent, Anthony J.

    2015-01-01

    Phonon optics concerns operations with high-frequency acoustic waves in solid media in a similar way to how traditional optics operates with the light beams (i.e. photons). Phonon optics experiments with coherent terahertz and sub-terahertz phonons promise a revolution in various technical applications related to high-frequency acoustics, imaging, and heat transport. Previously, phonon optics used passive methods for manipulations with propagating phonon beams that did not enable their external control. Here we fabricate a phononic chip, which includes a generator of coherent monochromatic phonons with frequency 378 GHz, a sensitive coherent phonon detector, and an active layer: a doped semiconductor superlattice, with electrical contacts, inserted into the phonon propagation path. In the experiments, we demonstrate the modulation of the coherent phonon flux by an external electrical bias applied to the active layer. Phonon optics using external control broadens the spectrum of prospective applications of phononics on the nanometer scale. PMID:25652241

  13. Estimating the Coherence of Noise in Quantum Control of a Solid-State Qubit

    NASA Astrophysics Data System (ADS)

    Feng, Guanru; Wallman, Joel J.; Buonacorsi, Brandon; Cho, Franklin H.; Park, Daniel K.; Xin, Tao; Lu, Dawei; Baugh, Jonathan; Laflamme, Raymond

    2016-12-01

    To exploit a given physical system for quantum information processing, it is critical to understand the different types of noise affecting quantum control. Distinguishing coherent and incoherent errors is extremely useful as they can be reduced in different ways. Coherent errors are generally easier to reduce at the hardware level, e.g., by improving calibration, whereas some sources of incoherent errors, e.g., T2* processes, can be reduced by engineering robust pulses. In this work, we illustrate how purity benchmarking and randomized benchmarking can be used together to distinguish between coherent and incoherent errors and to quantify the reduction in both of them due to using optimal control pulses and accounting for the transfer function in an electron spin resonance system. We also prove that purity benchmarking provides bounds on the optimal fidelity and diamond norm that can be achieved by correcting the coherent errors through improving calibration.

  14. Manipulating atomic fragmentation processes by controlling the projectile coherence.

    PubMed

    Egodapitiya, K N; Sharma, S; Hasan, A; Laforge, A C; Madison, D H; Moshammer, R; Schulz, M

    2011-04-15

    We have measured the scattering angle dependence of cross sections for ionization in p+H2 collisions for a fixed projectile energy loss. Depending on the projectile coherence, interference due to indistinguishable diffraction of the projectile from the two atomic centers was either present or absent in the data. This shows that, due to the fundamentals of quantum mechanics, the preparation of the beam must be included in theoretical calculations. The results have far-reaching implications on formal atomic scattering theory because this critical aspect has been overlooked for several decades.

  15. Coherent control of double deflected anomalous modes in ultrathin trapezoid-shaped slit metasurface

    PubMed Central

    Zhu, Z.; Liu, H.; Wang, D.; Li, Y. X.; Guan, C. Y.; Zhang, H.; Shi, J. H.

    2016-01-01

    Coherent light-matter interaction in ultrathin metamaterials has been demonstrated to dynamically modulate intensity, polarization and propagation direction of light. The gradient metasurface with a transverse phase variation usually exhibits an anomalous refracted beam of light dictated by so-called generalized Snell’s law. However, less attention has been paid to coherent control of the metasurface with multiple anomalous refracted beams. Here we propose an ultrathin gradient metasurface with single trapezoid-shaped slot antenna as its building block that allows one normal and two deflected transmitted beams. It is numerically demonstrated that such metasurface with multiple scattering modes can be coherently controlled to modulate output intensities by changing the relative phase difference between two counterpropagating coherent beams. Each mode can be coherently switched on/off and two deflected anomalous beams can be synchronously dictated by the phase difference. The coherent control effect in the trapezoid-shaped slit metasurface will offer a promising opportunity for multichannel signals modulation, multichannel sensing and wave front shaping. PMID:27874053

  16. Coherent control of double deflected anomalous modes in ultrathin trapezoid-shaped slit metasurface

    NASA Astrophysics Data System (ADS)

    Zhu, Z.; Liu, H.; Wang, D.; Li, Y. X.; Guan, C. Y.; Zhang, H.; Shi, J. H.

    2016-11-01

    Coherent light-matter interaction in ultrathin metamaterials has been demonstrated to dynamically modulate intensity, polarization and propagation direction of light. The gradient metasurface with a transverse phase variation usually exhibits an anomalous refracted beam of light dictated by so-called generalized Snell’s law. However, less attention has been paid to coherent control of the metasurface with multiple anomalous refracted beams. Here we propose an ultrathin gradient metasurface with single trapezoid-shaped slot antenna as its building block that allows one normal and two deflected transmitted beams. It is numerically demonstrated that such metasurface with multiple scattering modes can be coherently controlled to modulate output intensities by changing the relative phase difference between two counterpropagating coherent beams. Each mode can be coherently switched on/off and two deflected anomalous beams can be synchronously dictated by the phase difference. The coherent control effect in the trapezoid-shaped slit metasurface will offer a promising opportunity for multichannel signals modulation, multichannel sensing and wave front shaping.

  17. Realistic and verifiable coherent control of excitonic states in a light-harvesting complex

    NASA Astrophysics Data System (ADS)

    Hoyer, Stephan; Caruso, Filippo; Montangero, Simone; Sarovar, Mohan; Calarco, Tommaso; Plenio, Martin B.; Whaley, K. Birgitta

    2014-04-01

    We explore the feasibility of the coherent control of excitonic dynamics in light-harvesting complexes, analyzing the limits imposed by the open nature of these quantum systems. We establish feasible targets for phase and phase/amplitude control of the electronically excited state populations in the Fenna-Mathews-Olson (FMO) complex and analyze the robustness of this control with respect to orientational and energetic disorder, as well as the decoherence arising from coupling to the protein environment. We further present two possible routes to verification of the control target, with simulations for the FMO complex showing that steering of the excited state is experimentally verifiable either by extending excitonic coherence or by producing novel states in a pump-probe setup. Our results provide a first step toward coherent control of these complex biological quantum systems in an ultrafast spectroscopy setup.

  18. Optimal bang-bang control for SU(1,1) coherent states

    SciTech Connect

    Wu Jianwu; Li Chunwen; Zhang Jing; Tarn, T.-J.

    2007-11-15

    In this paper, the problem of achieving an arbitrary SU(1,1) coherent state is considered via switching the control field back and forth between admissible values with minimal number of switching times. When the controlled system Hamiltonian is hyperbolical or parabolical, the results show that the minimal switching number is one or two, which lies on whether the argument of the involved control is adjustable or not, and is independent of the target SU(1,1) coherent state. While for the elliptical case, the results indicate that the minimal number of switches needed depends on the target SU(1,1) coherent state and is provided as a function of it. In this case, one switch can also be saved if the argument of the involved control is adjustable. The theory developed here can also be extended to solve the optimal bang-bang control problem for a general SU(1,1) time evolution.

  19. Central Coherence in Typically Developing Preschoolers: Does It Cohere and Does It Relate to Mindreading and Executive Control?

    ERIC Educational Resources Information Center

    Pellicano, Elizabeth; Maybery, Murray; Durkin, Kevin

    2005-01-01

    Background: Frith and Happe (1994) describe central coherence (CC) as the normal tendency to integrate individual elements into a coherent whole, a cognitive style which varies in the general population. Individuals with autism are at the extreme (weak) end of the continuum of coherence. There has been debate over whether CC is independent from…

  20. Harvesting, Coupling, and Control of Single-Exciton Coherences in Photonic Waveguide Antennas

    NASA Astrophysics Data System (ADS)

    Mermillod, Q.; Jakubczyk, T.; Delmonte, V.; Delga, A.; Peinke, E.; Gérard, J.-M.; Claudon, J.; Kasprzak, J.

    2016-04-01

    We perform coherent nonlinear spectroscopy of individual excitons strongly confined in single InAs quantum dots (QDs). The retrieval of their intrinsically weak four-wave mixing (FWM) response is enabled by a one-dimensional dielectric waveguide antenna. Compared to a similar QD embedded in bulk media, the FWM detection sensitivity is enhanced by up to 4 orders of magnitude, over a broad operation bandwidth. Three-beam FWM is employed to investigate coherence and population dynamics within individual QD transitions. We retrieve their homogenous dephasing in a presence of low-frequency spectral wandering. Two-dimensional FWM reveals off-resonant Förster coupling between a pair of distinct QDs embedded in the antenna. We also detect a higher order QD nonlinearity (six-wave mixing) and use it to coherently control the FWM transient. Waveguide antennas enable us to conceive multicolor coherent manipulation schemes of individual emitters.

  1. The dominant coherent structure of the circular jet organized by controlled perturbation

    NASA Technical Reports Server (NTRS)

    Zaman, K. B. M. Q.; Hussain, A. K. M. F.

    1982-01-01

    The dominant large-scale coherent structure of a circular jet has been organized through controlled perturbation at the jet Strouhal number of 0.3, induced acoustically in two air jets through cavity resonance. Selected phases of the coherent structure were studied for three Reynolds numbers (25,000; 55,000; and 110,000), and two limiting initial conditions; laminar and fully turbulent initial boundary layers. Distributions of phase-average structure properties, i.e., longitudinal and lateral velocities, coherent vorticity and Reynolds stress, phase-random turbulence intensities and Reynolds stress, and streamline and pseudo-streamfunction patterns are obtained. The phase-random turbulence intensity is greatest at the structure center where the coherent vorticity is also the maximum. Some properties of the structure show mild but systematic dependence on Reynolds number.

  2. How to control the coherent oscillations in Landau-Zener-Stueckelberg dynamics of three-level system

    NASA Astrophysics Data System (ADS)

    Qin, Xiao-Ke

    2016-02-01

    Coherent pulse is used to control and measure the quantum state of three-level system in double quantum dots. We analyze the coherent oscillations in Landau-Zener-Stueckelberg (LZS) dynamics by the adiabatic-impulse model, which simplifies the applied pulse as an optical interference device. Under the designed “hat-shape” pulse, the sweeping speed through each avoid crossing can be tuned independently. The coherent oscillations in LZS dynamics of three-level system are optimized by the control pulse. Moreover, we can filter out the coherent oscillations with the unexpected frequency and only keep the coherent oscillations with the frequency we are interested in.

  3. Phase control of light transmission and reflection based biexciton coherence in a defect dielectric medium.

    PubMed

    Asadpour, Seyyed Hossein; Soleimani, H Rahimpour

    2014-10-01

    Phase control of two weak probe lights' transmission and reflection based biexciton coherence in a defect dielectric medium doped by four-level GaAs/AlGaAs multiple quantum wells with 15 periods of 17.5 nm GaAs wells and 15 nm Al0.3Ga0.7As barriers is theoretically investigated. The biexciton coherence in this scheme is set up by two continuous wave control fields that couple to a resonance of biexcitons. It is shown that the transmission and reflection properties versus relative phase between applied fields can be controlled by the intensity of control fields and exciton spin relaxation between exciton states. Our studies show that many-particle interactions due to Coulomb correlations in semiconductors can be harnessed by quantum coherence in an interacting many-particle system.

  4. Stabilization of ultracold molecules using optimal control theory

    SciTech Connect

    Koch, Christiane P.; Palao, Jose P.; Kosloff, Ronnie; Masnou-Seeuws, Francoise

    2004-07-01

    In recent experiments on ultracold matter, molecules have been produced from ultracold atoms by photoassociation, Feshbach resonances, and three-body recombination. The created molecules are translationally cold, but vibrationally highly excited. This will eventually lead them to be lost from the trap due to collisions. We propose shaped laser pulses to transfer these highly excited molecules to their ground vibrational level. Optimal control theory is employed to find the light field that will carry out this task with minimum intensity. We present results for the sodium dimer. The final target can be reached to within 99% provided the initial guess field is physically motivated. We find that the optimal fields contain the transition frequencies required by a good Franck-Condon pumping scheme. The analysis identifies the ranges of intensity and pulse duration which are able to achieve this task before any other competing processes take place. Such a scheme could produce stable ultracold molecular samples or even stable molecular Bose-Einstein condensates.

  5. Multimonth controlled small molecule release from biodegradable thin films

    PubMed Central

    Hsu, Bryan B.; Park, Myoung-Hwan; Hagerman, Samantha R.; Hammond, Paula T.

    2014-01-01

    Long-term, localized delivery of small molecules from a biodegradable thin film is challenging owing to their low molecular weight and poor charge density. Accomplishing highly extended controlled release can facilitate high therapeutic levels in specific regions of the body while significantly reducing the toxicity to vital organs typically caused by systemic administration and decreasing the need for medical intervention because of its long-lasting release. Also important is the ability to achieve high drug loadings in thin film coatings to allow incorporation of significant drug amounts on implant surfaces. Here we report a sustained release formulation for small molecules based on a soluble charged polymer–drug conjugate that is immobilized into nanoscale, conformal, layer-by-layer assembled films applicable to a variety of substrate surfaces. We measured a highly predictable sustained drug release from a polymer thin film coating of 0.5–2.7 μm that continued for more than 14 mo with physiologically relevant drug concentrations, providing an important drug delivery advance. We demonstrated this effect with a potent small molecule nonsteroidal anti-inflammatory drug, diclofenac, because this drug can be used to address chronic pain, osteoarthritis, and a range of other critical medical issues. PMID:25092310

  6. Coherent control of a linear microwave cavity via single flux quantum pulses

    NASA Astrophysics Data System (ADS)

    Zhu, Shaojiang; Ribeill, Guilhem; Thorbeck, Ted; Leonard, Edward; Vavilov, Maxim; Plourde, Britton; McDermott, Robert

    Classical Josephson digital logic based on single flux quantum (SFQ) pulses offers a path to robust, low-latency control of a large-scale quantum processor. Here we describe the coherent control of a linear superconducting cavity by direct excitation via SFQ pulses. Resonant trains of SFQ pulses are capacitively coupled to a thin-film coplanar waveguide cavity. We examine the resulting cavity states as a function of subharmonic drive and temperature. In addition, we describe first steps toward the coherent control of a superconducting qubit with SFQ pulses.

  7. Controllable dissociations of PH3 molecules on Si(001)

    NASA Astrophysics Data System (ADS)

    Liu, Qin; Lei, Yanhua; Shao, Xiji; Ming, Fangfei; Xu, Hu; Wang, Kedong; Xiao, Xudong

    2016-04-01

    We demonstrate for the first time to our knowledge that controllable dissociation of PH3 adsorption products PH x (x = 2, 1) can be realized by STM (scanning tunneling microscope) manipulation techniques at room temperature. Five dissociative products and their geometric structures are identified via combining STM experiments and first-principle calculations and simulations. In total we realize nine kinds of controllable dissociations by applying a voltage pulse among the PH3-related structures on Si(001). The dissociation rates of the five most common reactions are measured by the I-t spectrum method as a function of voltage. The suddenly increased dissociation rate at 3.3 V indicates a transition from multivibrational excitation to single-step excitation induced by inelastic tunneling electrons. Our studies prove that selectively breaking the chemical bonds of a single molecule on semiconductor surface by STM manipulation technique is feasible.

  8. Quantum optimal control theory applied to transitions in diatomic molecules

    NASA Astrophysics Data System (ADS)

    Lysebo, Marius; Veseth, Leif

    2014-12-01

    Quantum optimal control theory is applied to control electric dipole transitions in a real multilevel system. The specific system studied in the present work is comprised of a multitude of hyperfine levels in the electronic ground state of the OH molecule. Spectroscopic constants are used to obtain accurate energy eigenstates and electric dipole matrix elements. The goal is to calculate the optimal time-dependent electric field that yields a maximum of the transition probability for a specified initial and final state. A further important objective was to study the detailed quantum processes that take place during such a prescribed transition in a multilevel system. Two specific transitions are studied in detail. The computed optimal electric fields as well as the paths taken through the multitude of levels reveal quite interesting quantum phenomena.

  9. Electronic control of coherence in a two-dimensional array of photonic crystal surface emitting lasers.

    PubMed

    Taylor, R J E; Childs, D T D; Ivanov, P; Stevens, B J; Babazadeh, N; Crombie, A J; Ternent, G; Thoms, S; Zhou, H; Hogg, R A

    2015-08-20

    We demonstrate a semiconductor PCSEL array that uniquely combines an in-plane waveguide structure with nano-scale patterned PCSEL elements. This novel geometry allows two-dimensional electronically controllable coherent coupling of remote vertically emitting lasers. Mutual coherence of the PCSEL elements is verified through the demonstration of a two-dimensional Young's Slits experiment. In addition to allowing the all-electronic control of the interference pattern, this type of device offers new routes to power and brightness scaling in semiconductor lasers, and opportunities for all-electronic beam steering.

  10. Electronic control of coherence in a two-dimensional array of photonic crystal surface emitting lasers

    NASA Astrophysics Data System (ADS)

    Taylor, R. J. E.; Childs, D. T. D.; Ivanov, P.; Stevens, B. J.; Babazadeh, N.; Crombie, A. J.; Ternent, G.; Thoms, S.; Zhou, H.; Hogg, R. A.

    2015-08-01

    We demonstrate a semiconductor PCSEL array that uniquely combines an in-plane waveguide structure with nano-scale patterned PCSEL elements. This novel geometry allows two-dimensional electronically controllable coherent coupling of remote vertically emitting lasers. Mutual coherence of the PCSEL elements is verified through the demonstration of a two-dimensional Young’s Slits experiment. In addition to allowing the all-electronic control of the interference pattern, this type of device offers new routes to power and brightness scaling in semiconductor lasers, and opportunities for all-electronic beam steering.

  11. Quantum manipulation and enhancement of deterministic entanglement between atomic ensemble and light via coherent feedback control

    NASA Astrophysics Data System (ADS)

    Yan, Zhihui; Jia, Xiaojun

    2017-06-01

    A quantum mechanical model of the non-measurement based coherent feedback control (CFC) is applied to deterministic atom-light entanglement with imperfect retrieval efficiency, which is generated based on Raman process. We investigate the influence of different experimental parameters on entanglement property of CFC Raman system. By tailoring the transmissivity of coherent feedback controller, it is possible to manipulate the atom-light entanglement. Particularly, we show that CFC allows atom-light entanglement enhancement under appropriate operating conditions. Our work can provide entanglement source between atomic ensemble and light of high quality for high-fidelity quantum networks and quantum computation based on atomic ensemble.

  12. Use of coherent control methods through scattering biological tissue to achieve functional imaging

    PubMed Central

    Dela Cruz, Johanna M.; Pastirk, Igor; Comstock, Matthew; Lozovoy, Vadim V.; Dantus, Marcos

    2004-01-01

    We test whether coherent control methods based on ultrashort-pulse phase shaping can be applied when the laser light propagates through biological tissue. Our results demonstrate experimentally that the spectral-phase properties of shaped laser pulses optimized to achieve selective two-photon excitation survive as the laser pulses propagate through tissue. This observation is used to obtain functional images based on selective two-photon excitation of a pH-sensitive chromophore in a sample that is placed behind a slice of biological tissue. Our observation of coherent control through scattering tissue suggests possibilities in multiphoton-based imaging and photodynamic therapy. PMID:15569924

  13. Electronic control of coherence in a two-dimensional array of photonic crystal surface emitting lasers

    PubMed Central

    Taylor, R. J. E.; Childs, D. T. D.; Ivanov, P.; Stevens, B. J.; Babazadeh, N.; Crombie, A. J.; Ternent, G.; Thoms, S.; Zhou, H.; Hogg, R. A.

    2015-01-01

    We demonstrate a semiconductor PCSEL array that uniquely combines an in-plane waveguide structure with nano-scale patterned PCSEL elements. This novel geometry allows two-dimensional electronically controllable coherent coupling of remote vertically emitting lasers. Mutual coherence of the PCSEL elements is verified through the demonstration of a two-dimensional Young’s Slits experiment. In addition to allowing the all-electronic control of the interference pattern, this type of device offers new routes to power and brightness scaling in semiconductor lasers, and opportunities for all-electronic beam steering. PMID:26289621

  14. Controlled generation of coherent matter currents using a periodic driving field.

    PubMed

    Creffield, C E; Sols, F

    2008-06-27

    We study the effect of a strong, oscillating driving field on the dynamics of ultracold bosons held in an optical lattice. Modeling the system as a Bose-Hubbard model, we show how the driving field can be used to produce and maintain a coherent atomic current by controlling the phase of the intersite tunneling processes. We investigate both the stroboscopic and time-averaged behavior using Floquet theory, and demonstrate that this procedure provides a stable and precise method of controlling coherent quantum systems.

  15. Coherent Control of Biomolecules and Imaging Using Nanodoublers

    NASA Astrophysics Data System (ADS)

    Bonacina, L.; Wolf, Jean-Pierre

    In the quest for the next generation of imaging bio-markers, successful probes have to prove to be non toxic, bright, stable against long term excitation, and able to generate a sharp contrast against background fluorescence. In all these respects, Harmonic Nanoparticles (HNPs, "nanodoublers") are receiving an increasing attention as they also open a series of alternative detection possibilities simply not accessible with the present generation of fluorescent dyes and quantum dots. In the first part of the chapter, we report on this novel labelling method with unprecedented wavelength flexibility, enabled by the non-resonant nature of the second harmonic process. The possibility of employing infrared excitation and the consequent deeper tissue penetration is especially promising for their in vivo applications [1]. The phase-coherent optical response of HNPs can also be exploited to fully characterize the excitation laser pulse in the focal spot of a high-NA objective with nanometric resolution. This proof-of-principle "nano-FROG" experiment [2] sets the ground for further phase-sensitive self-referenced applications, after the recent demonstration of harmonic holography and heterodyne detection with external references.

  16. Optical control and coherence of electron or hole spins in coupled quantum dots

    NASA Astrophysics Data System (ADS)

    Carter, Samuel

    2013-03-01

    The spin of an electron or hole in an InAs quantum dot is an attractive qubit because it combines the advantages of a semiconductor platform with the power of ultrafast optical coherent control techniques. In the last few years, basic quantum operations such as initialization, rotation, and readout have become possible using single spins, but now improvements in spin coherence and demonstrations of multi-qubit systems are needed. In this work, we combine advances in the design and growth of coupled quantum dots with optical coherent control techniques to demonstrate ultrafast manipulation and coherence improvements for one or two interacting electron or hole spins in a coupled pair of InAs dots. For each of these spin systems, we use a sequence of picosecond and nanosecond pulses to initialize, manipulate, and measure the coherent spin dynamics. These dynamics include precession about a magnetic field and also entangling dynamics from the exchange interaction for coupled spins. For a single electron spin, precession dephases after only a few nanoseconds due to the hyperfine interaction with nuclear spins. For hole spins, we measure a dephasing time an order of magnitude longer due to a weaker hyperfine interaction. Coupled electron and hole spins are essential for multi-qubit systems, and they can also be used to decrease sensitivity to the environment. In these systems, we typically measure the coherent dynamics of the singlet-triplet states (ms = 0), which are much less sensitive to the nuclear environment. At present, dephasing is due to fluctuations in the electrical environment. With careful sample design, we can make these systems much less sensitive to electrical fluctuations, giving a powerful combination of long coherence times and ultrafast gates. Finally, we demonstrate that these spin qubits can be incorporated into a photonic crystal cavity and manipulated with optical pulses, a major step toward a quantum interface between photons and these spin

  17. Complete Coherent Control of a Quantum Dot Strongly Coupled to a Nanocavity.

    PubMed

    Dory, Constantin; Fischer, Kevin A; Müller, Kai; Lagoudakis, Konstantinos G; Sarmiento, Tomas; Rundquist, Armand; Zhang, Jingyuan L; Kelaita, Yousif; Vučković, Jelena

    2016-04-26

    Strongly coupled quantum dot-cavity systems provide a non-linear configuration of hybridized light-matter states with promising quantum-optical applications. Here, we investigate the coherent interaction between strong laser pulses and quantum dot-cavity polaritons. Resonant excitation of polaritonic states and their interaction with phonons allow us to observe coherent Rabi oscillations and Ramsey fringes. Furthermore, we demonstrate complete coherent control of a quantum dot-photonic crystal cavity based quantum-bit. By controlling the excitation power and phase in a two-pulse excitation scheme we achieve access to the full Bloch sphere. Quantum-optical simulations are in good agreement with our experiments and provide insight into the decoherence mechanisms.

  18. Complete Coherent Control of a Quantum Dot Strongly Coupled to a Nanocavity

    PubMed Central

    Dory, Constantin; Fischer, Kevin A.; Müller, Kai; Lagoudakis, Konstantinos G.; Sarmiento, Tomas; Rundquist, Armand; Zhang, Jingyuan L.; Kelaita, Yousif; Vučković, Jelena

    2016-01-01

    Strongly coupled quantum dot-cavity systems provide a non-linear configuration of hybridized light-matter states with promising quantum-optical applications. Here, we investigate the coherent interaction between strong laser pulses and quantum dot-cavity polaritons. Resonant excitation of polaritonic states and their interaction with phonons allow us to observe coherent Rabi oscillations and Ramsey fringes. Furthermore, we demonstrate complete coherent control of a quantum dot-photonic crystal cavity based quantum-bit. By controlling the excitation power and phase in a two-pulse excitation scheme we achieve access to the full Bloch sphere. Quantum-optical simulations are in good agreement with our experiments and provide insight into the decoherence mechanisms. PMID:27112420

  19. Coherent control of plasma dynamics by feedback-optimized wavefront manipulation

    SciTech Connect

    He, Z.-H.; Hou, B.; Gao, G.; Nees, J. A.; Krushelnick, K.; Thomas, A. G. R.; Lebailly, V.; Clarke, R.

    2015-05-15

    Plasmas generated by an intense laser pulse can support coherent structures such as large amplitude wakefield that can affect the outcome of an experiment. We investigate the coherent control of plasma dynamics by feedback-optimized wavefront manipulation using a deformable mirror. The experimental outcome is directly used as feedback in an evolutionary algorithm for optimization of the phase front of the driving laser pulse. In this paper, we applied this method to two different experiments: (i) acceleration of electrons in laser driven plasma waves and (ii) self-compression of optical pulses induced by ionization nonlinearity. The manipulation of the laser wavefront leads to orders of magnitude improvement to electron beam properties such as the peak charge, beam divergence, and transverse emittance. The demonstration of coherent control for plasmas opens new possibilities for future laser-based accelerators and their applications.

  20. Enabling coherent control of trapped ions with economical multi-laser frequency stabilization technology

    NASA Astrophysics Data System (ADS)

    Lybarger, Warren Emanuel, Jr.

    A phase-locked scanning stability transfer cavity (SSTC) for transferring the absolute frequency stability of an iodine referenced He-Ne (master) laser to three otherwise uncalibrated (slave) lasers (at 844, 1033, & 1092 nm) of a trapped-Sr+ quantum information processing (QIP) apparatus is described. When locked, the 422 nm frequency-doubled Doppler-cooling laser exhibits an error of <1 MHz RMS for several hours, and similar stability is achieved with the other slave lasers. When unlocked, each slave laser drifts by a large fraction (or more) of the corresponding transition linewidth in minutes, thus making reliable laser cooling, ion state readout, and execution of QIP algorithms practically infeasible. The SSTC makes coherent control of Sr+ possible by addressing this problem, and the QIP apparatus is now sufficiently stable for single user operation. New single-ion experimental capabilities include ground state cooling, high-fidelity Rabi flopping, Ramsey interferometry, and sympathetic cooling of 88Sr+( 86Sr+) with 86Sr+( 88Sr+). A 2.5 msec coherence time has been achieved with the optical quoit encoded in a |5 2S 1/2> ↔ |4 2D5/2> quadrupole transition, a precision measurement of the isotope shift of the qubit transition in 86Sr+ relative to 88Sr+ is reported, and a single-ion heating rate consistent with results throughout the trapped-ion community is reported. The SSTC is simple to implement, uses no custom optics, and it has a higher scanning rate than previously demonstrated SSTC's. Phase-locked SSTC's are shown to have an advantage over the more common displacement-locked SSTC in the low finesse regime, and they are an attractive alternative to passively stable but complex optical references and diode lasers designed to address the same problem. The SSTC is useful in spectroscopic applications with other ion species, atoms, and molecules, in general. An appendix is dedicated to describing in detail an advanced trapped-ion quantum processor concept

  1. Controlled storage and transfer of photonic space-time quantum-coherence in active quantum dot nanomaterials.

    PubMed

    Gehrig, E; Hess, O

    2008-03-17

    We demonstrate the potential of semiconductor quantum dot nanomaterials for solid-state based controllable quantum memories in which losses may be compensated by gain. The dynamic photonic quantum-coherence present in a quantum dot ensemble and generated by a coherent signal pulse is influenced and controlled by disorder, spectral detuning and the power of the pulse. We show that the high coupling of spatial and temporal degrees of freedom is a key requirement for coherence transfer and/or storage.

  2. Controlling spins in adsorbed molecules by a chemical switch

    PubMed Central

    Wäckerlin, Christian; Chylarecka, Dorota; Kleibert, Armin; Müller, Kathrin; Iacovita, Cristian; Nolting, Frithjof; Jung, Thomas A.; Ballav, Nirmalya

    2010-01-01

    The development of chemical systems with switchable molecular spins could lead to the architecture of materials with controllable magnetic or spintronic properties. Here, we present conclusive evidence that the spin of an organometallic molecule coupled to a ferromagnetic substrate can be switched between magnetic off and on states by a chemical stimulus. This is achieved by nitric oxide (NO) functioning as an axial ligand of cobalt(II)tetraphenylporphyrin (CoTPP) ferromagnetically coupled to nickel thin-film (Ni(001)). On NO addition, the coordination sphere of Co2+ is modified and a NO–CoTPP nitrosyl complex is formed, which corresponds to an off state of the Co spin. Thermal dissociation of NO from the nitrosyl complex restores the on state of the Co spin. The NO-induced reversible off–on switching of surface-adsorbed molecular spins observed here is attributed to a spin trans effect. PMID:20975713

  3. Coherent control of the waveforms of recoilless γ-ray photons.

    PubMed

    Vagizov, Farit; Antonov, Vladimir; Radeonychev, Y V; Shakhmuratov, R N; Kocharovskaya, Olga

    2014-04-03

    The concepts and ideas of coherent, nonlinear and quantum optics have been extended to photon energies in the range of 10-100 kiloelectronvolts, corresponding to soft γ-ray radiation (the term used when the radiation is produced in nuclear transitions) or, equivalently, hard X-ray radiation (the term used when the radiation is produced by electron motion). The recent experimental achievements in this energy range include the demonstration of parametric down-conversion in the Langevin regime, electromagnetically induced transparency in a cavity, the collective Lamb shift, vacuum-assisted generation of atomic coherences and single-photon revival in nuclear absorbing multilayer structures. Also, realization of single-photon coherent storage and stimulated Raman adiabatic passage were recently proposed in this regime. More related work is discussed in a recent review. However, the number of tools for the coherent manipulation of interactions between γ-ray photons and nuclear ensembles remains limited. Here we suggest and implement an efficient method to control the waveforms of γ-ray photons coherently. In particular, we demonstrate the conversion of individual recoilless γ-ray photons into a coherent, ultrashort pulse train and into a double pulse. Our method is based on the resonant interaction of γ-ray photons with an ensemble of nuclei with a resonant transition frequency that is periodically modulated in time. The frequency modulation, which is achieved by a uniform vibration of the resonant absorber, owing to the Doppler effect, renders resonant absorption and dispersion both time dependent, allowing us to shape the waveforms of the incident γ-ray photons. We expect that this technique will lead to advances in the emerging fields of coherent and quantum γ-ray photon optics, providing a basis for the realization of γ-ray-photon/nuclear-ensemble interfaces and quantum interference effects at nuclear γ-ray transitions.

  4. Coherent Control of Optical Spin-to-Orbital Angular Momentum Conversion in Metasurface.

    PubMed

    Zhang, Huifang; Kang, Ming; Zhang, Xueqian; Guo, Wengao; Lv, Changgui; Li, Yanfeng; Zhang, Weili; Han, Jiaguang

    2017-02-01

    Efficient control over the conversion of optical angular momentum from spin to orbital form in a metasurface system is achieved. Under coherent symmetric incidence, it can support nearly 100% conversion and unitary output, while it can support 50% conversion with 25% transmittance under one beam incidence.

  5. Generalization of the theory of coherent control of photocurrent generation in semiconductors

    NASA Astrophysics Data System (ADS)

    L. P. Hughes, James; Sipe, J. E.; Shkrebtii, A. I.

    1998-03-01

    The theoretical prediction of the coherent control of photocurrent generation in bulk semiconductors [1] has recently been experimentally confirmed for GaAs [2]. When two monochromatic beams of frequency ω and 2ω are incident on an intrinsic semiconductor, a photocurrent is generated whose direction and magnitude can be controlled by simply adjusting the relative phase between the two pulses. Such a process is very interesting from a technological and scientific point of view. The aims of this presentation are twofold. First, the theoretical approach of [1] is generalized for nondegenerate frequencies, and second, we examine the physics behind the coherent control effect in more detail as a means of gaining more insight into the process. We analyze the origin of the coherent photocurrent in terms of contributing regions in separate parts of the Brillouin zone, fine details of the electronic band structure, the dependence on contributions from various real and virtual bands, and the velocity distribution of electrons and holes for various energies and relative phases. The possibility of observing coherently controlled photocurrent for a wider class of semiconductors will be discussed, and in this regard, we present results for this current in Germanium. [1] R. Atanasov, et. al, Phys. Rev. Lett. 76 1703 (1996). [2] A. Hache, et. al, Phys. Rev. Lett. 78 306 (1997).

  6. Radiationless relaxation in “large” molecules: Experimental evidence for preparation of true molecular eigenstates and Born-Oppenheimer states by a coherent light source

    PubMed Central

    Zewail, A. H.; Orlowski, T. E.; Jones, K. E.

    1977-01-01

    Photon absorption and emission by molecules that undergo radiationless transitions are examined using the single modes of lasers having well-defined coherence properties. Contrary to the usual beliefs, where it is assumed that the molecule is prepared in a Born-Oppenheimer singlet state and then “crosses-over” to other states (vibrationally “hot” singlets and/or triplets), it is shown experimentally that the true eigenstates of the molecule can be prepared, even in “large” molecules, if the laser correlation time is relatively long and the molecular relaxation is made slow. On the other hand, lasers with short (psec) correlation time have yielded effectively the singlet Born-Oppenheimer state, which has a much shorter lifetime than the true eigenstates. Effects of magnetic fields and temperature are also reported. The former changes the amount of mixing amongst the Born-Oppenheimer states. The latter, on the other hand, swings the molecule from being “small” (i.e., sparse vibronic structure with long lifetimes) to being “large” (i.e., dense statistical distribution of levels) since the relaxation between levels is very effective at high temperatures. Finally, the results of this work show that the words fluorescence and phosphorescence in their strict meaning are misleading if the true eigenstates, which may contain both singlet and triplet character, are prepared. Images PMID:16578747

  7. Optimal nonlinear coherent mode transitions in Bose-Einstein condensates utilizing spatiotemporal controls

    NASA Astrophysics Data System (ADS)

    Hocker, David; Yan, Julia; Rabitz, Herschel

    2016-05-01

    Bose-Einstein condensates (BECs) offer the potential to examine quantum behavior at large length and time scales, as well as forming promising candidates for quantum technology applications. Thus, the manipulation of BECs using control fields is a topic of prime interest. We consider BECs in the mean-field model of the Gross-Pitaevskii equation (GPE), which contains linear and nonlinear features, both of which are subject to control. In this work we report successful optimal control simulations of a one-dimensional GPE by modulation of the linear and nonlinear terms to stimulate transitions into excited coherent modes. The linear and nonlinear controls are allowed to freely vary over space and time to seek their optimal forms. The determination of the excited coherent modes targeted for optimization is numerically performed through an adaptive imaginary time propagation method. Numerical simulations are performed for optimal control of mode-to-mode transitions between the ground coherent mode and the excited modes of a BEC trapped in a harmonic well. The results show greater than 99 % success for nearly all trials utilizing reasonable initial guesses for the controls, and analysis of the optimal controls reveals primarily direct transitions between initial and target modes. The success of using solely the nonlinearity term as a control opens up further research toward exploring novel control mechanisms inaccessible to linear Schrödinger-type systems.

  8. A Coherence Preservation Control Strategy in Cavity QED Based on Classical Quantum Feedback

    PubMed Central

    Chen, Wei; Gao, Junli

    2013-01-01

    For eliminating the unexpected decoherence effect in cavity quantum electrodynamics (cavity QED), the transfer function of Rabi oscillation is derived theoretically using optical Bloch equations. In particular, the decoherence in cavity QED from the atomic spontaneous emission is especially considered. A feedback control strategy is proposed to preserve the coherence through Rabi oscillation stabilization. In the scheme, a classical quantum feedback channel for the quantum information acquisition is constructed via the quantum tomography technology, and a compensation system based on the root locus theory is put forward to suppress the atomic spontaneous emission and the associated decoherence. The simulation results have proved its effectiveness and superiority for the coherence preservation. PMID:23781154

  9. All-fiber phase-control-free coherent-beam combining toward femtosecond-pulse amplification

    NASA Astrophysics Data System (ADS)

    Kambayashi, Yuta; Yoshida, Minoru; Sasaki, Toshiki; Yoshikawa, Masashi

    2017-01-01

    Our present work is to develop an all-fiber coherent-beam-combining system that achieves a high-energy femtosecond-pulse fiber laser beyond pulse energy limits due to the nonlinear effects in fiber amplifiers. Coherent-beam combining (CBC) using optical fibers is technically difficult because the optical phases and the polarizations in the optical fibers fluctuate due to disturbances. We developed an all-fiber passive CBC system that does not need to control optical phases and polarizations that achieved a beam-combining efficiency of 95.9%. The combined output changes of the passive CBC system are the less than 1.0% in full width.

  10. A coherence preservation control strategy in cavity QED based on classical quantum feedback.

    PubMed

    Li, Ming; Chen, Wei; Gao, Junli

    2013-01-01

    For eliminating the unexpected decoherence effect in cavity quantum electrodynamics (cavity QED), the transfer function of Rabi oscillation is derived theoretically using optical Bloch equations. In particular, the decoherence in cavity QED from the atomic spontaneous emission is especially considered. A feedback control strategy is proposed to preserve the coherence through Rabi oscillation stabilization. In the scheme, a classical quantum feedback channel for the quantum information acquisition is constructed via the quantum tomography technology, and a compensation system based on the root locus theory is put forward to suppress the atomic spontaneous emission and the associated decoherence. The simulation results have proved its effectiveness and superiority for the coherence preservation.

  11. Experimental control of transport resonances in a coherent quantum rocking ratchet

    PubMed Central

    Grossert, Christopher; Leder, Martin; Denisov, Sergey; Hänggi, Peter; Weitz, Martin

    2016-01-01

    The ratchet phenomenon is a means to get directed transport without net forces. Originally conceived to rectify stochastic motion and describe operational principles of biological motors, the ratchet effect can be used to achieve controllable coherent quantum transport. This transport is an ingredient of several perspective quantum devices including atomic chips. Here we examine coherent transport of ultra-cold atoms in a rocking quantum ratchet. This is realized by loading a rubidium atomic Bose–Einstein condensate into a periodic optical potential subjected to a biharmonic temporal drive. The achieved long-time coherence allows us to resolve resonance enhancement of the atom transport induced by avoided crossings in the Floquet spectrum of the system. By tuning the strength of the temporal modulations, we observe a bifurcation of a single resonance into a doublet. Our measurements reveal the role of interactions among Floquet eigenstates for quantum ratchet transport. PMID:26852803

  12. Coherent spin control of a nanocavity-enhanced qubit in diamond

    DOE PAGES

    Li, Luozhou; Lu, Ming; Schroder, Tim; ...

    2015-01-28

    A central aim of quantum information processing is the efficient entanglement of multiple stationary quantum memories via photons. Among solid-state systems, the nitrogen-vacancy centre in diamond has emerged as an excellent optically addressable memory with second-scale electron spin coherence times. Recently, quantum entanglement and teleportation have been shown between two nitrogen-vacancy memories, but scaling to larger networks requires more efficient spin-photon interfaces such as optical resonators. Here we report such nitrogen-vacancy nanocavity systems in strong Purcell regime with optical quality factors approaching 10,000 and electron spin coherence times exceeding 200 µs using a silicon hard-mask fabrication process. This spin-photon interfacemore » is integrated with on-chip microwave striplines for coherent spin control, providing an efficient quantum memory for quantum networks.« less

  13. Coherent spin control of a nanocavity-enhanced qubit in diamond

    SciTech Connect

    Li, Luozhou; Lu, Ming; Schroder, Tim; Chen, Edward H.; Walsh, Michael; Bayn, Igal; Goldstein, Jordan; Gaathon, Ophir; Trusheim, Matthew E.; Mower, Jacob; Cotlet, Mircea; Markham, Matthew L.; Twitchen, Daniel J.; Englund, Dirk

    2015-01-28

    A central aim of quantum information processing is the efficient entanglement of multiple stationary quantum memories via photons. Among solid-state systems, the nitrogen-vacancy centre in diamond has emerged as an excellent optically addressable memory with second-scale electron spin coherence times. Recently, quantum entanglement and teleportation have been shown between two nitrogen-vacancy memories, but scaling to larger networks requires more efficient spin-photon interfaces such as optical resonators. Here we report such nitrogen-vacancy nanocavity systems in strong Purcell regime with optical quality factors approaching 10,000 and electron spin coherence times exceeding 200 µs using a silicon hard-mask fabrication process. This spin-photon interface is integrated with on-chip microwave striplines for coherent spin control, providing an efficient quantum memory for quantum networks.

  14. Non-linear optics of coupled quantum dots and atomic systems with coherent control fields

    NASA Astrophysics Data System (ADS)

    Mumba, Mambwe

    Presented herein is an investigation of quantum systems with coherent optical control fields. Three such systems are examined. The first consists of two dipole-dipole coupled quantum dots or dimers which behave as an effective three or four-level system whose susceptibility and hence transmissivity for an optical beam at some frequency may be switched on or off in response to a coherent control field. The second quantum system consists of a model cluster of three coupled dots that is shown to display light intermittency or blinking when irradiated by a coherent field. Results indicate that the observed variation in rate, intensity and duration of blinking times occasioned by the rare but observable rapid blinking at higher rate and intensity (superradiance) can be traced back to the groupings of states in different manifolds that the coupled system is capable of being found in at any given time. It is shown, however, that the experimentally observed blinking can not be entirely accounted for by dipole-dipole coupling alone. The third system investigated consists of Rubidium atoms in a cell placed in a ring cavity. A coherent control field drives the system. A mathematical model of the system is developed which consists of propagating a gaussian beam around the system and examining the output spectrum when a steady state value of the electromagnetic field is attained in the Rubidium cell. Some interesting features occurring in the output spectrum of the field at some cavity detuning are reproduced and match those experimentally observed.

  15. Multi-wave coherent control of a solid-state single emitter

    NASA Astrophysics Data System (ADS)

    Fras, F.; Mermillod, Q.; Nogues, G.; Hoarau, C.; Schneider, C.; Kamp, M.; Höfling, S.; Langbein, W.; Kasprzak, J.

    2016-03-01

    Coherent control of individual two-level systems is at the heart of any quantum information protocol. In solids, two-level systems generated by bound electron-hole excitonic states, trapped in semiconductor quantum dots, display a robust coupling with light, enabling their optical manipulation via avant-garde approaches of nonlinear spectroscopy. Here, we develop a novel toolbox for coherent control of a quantum dot exciton based on the nonlinear wave-mixing responses, which are enhanced by a photonic nanostructure. By employing three, short, resonant laser pulses, we show that we can manipulate, at will, the intrinsic coherence of the quantum dot dipole and therefore engineer the spectro-temporal shape of its coherent emission. Multi-pulse quantum control sequences, which have been successful in NMR spectroscopy and quantum computation, can now be applied to optically active solid-state quantum bits with application in high-order nonlinear spectroscopy, ultrafast quantum optoelectronics and spread spectrum technology at the single emitter level.

  16. Coherent control of quantum fluctuations using cavity electromagnetically induced transparency.

    PubMed

    Souza, J A; Figueroa, E; Chibani, H; Villas-Boas, C J; Rempe, G

    2013-09-13

    We study the all-optical control of the quantum fluctuations of a light beam via a combination of single-atom cavity quantum electrodynamics (CQED) and electromagnetically induced transparency (EIT). Specifically, the EIT control field is used to tune the CQED transition frequencies in and out of resonance with the probe light. In this way, photon blockade and antiblockade effects are employed to produce sub-Poissonian and super-Poissonian light fields, respectively. The achievable quantum control paves the way towards the realization of a prototype of a novel quantum transistor which amplifies or attenuates the relative intensity noise of a light beam. Its feasibility is demonstrated by calculations using realistic parameters from recent experiments.

  17. Optimal pulse shaping for coherent control by the penalty algorithm

    NASA Astrophysics Data System (ADS)

    Shen, Hai; Dussault, Jean-Pièrre; Bandrauk, André D.

    1994-04-01

    We use penalty methods coupled with unitary exponential operator methods to solve the optimal control problem for molecular time-dependent Schrödinger equations involving laser pulse excitations. A stable numerical algorithm is presented which propagates directly from initial states to given final states. Results are reported for an analytically solvable model for the complete inversion of a three-state system.

  18. Coherent combining of second-harmonic generators by active phase control of the fundamental waves.

    PubMed

    Odier, Alice; Durécu, Anne; Melkonian, Jean-Michel; Lombard, Laurent; Lefebvre, Michel; Bourdon, Pierre

    2017-08-15

    Coherent beam combining by active phase control could be useful for power scaling fiber-laser-pumped optical frequency converters. However, a fast phase modulator operating at the frequency-converted wavelength, a non-standard component, would be necessary. Fortunately, nonlinear conversion processes rely on a phase-matching condition allowing for indirect phase control using standard phase modulators. In this Letter, coherent combining of second-harmonic generators is demonstrated in both birefringent and quasi-phase-matching schemes in CW regime. Phase control operates at the fundamental wavelength, using all-fiber electro-optic modulators. An excellent beam combination is achieved with a residual phase error of λ/30 on the second-harmonic wave.

  19. STM CONTROL OF CHEMICAL REACTIONS: Single-Molecule Synthesis

    NASA Astrophysics Data System (ADS)

    Hla, Saw-Wai; Rieder, Karl-Heinz

    2003-10-01

    The fascinating advances in single atom/molecule manipulation with a scanning tunneling microscope (STM) tip allow scientists to fabricate atomic-scale structures or to probe chemical and physical properties of matters at an atomic level. Owing to these advances, it has become possible for the basic chemical reaction steps, such as dissociation, diffusion, adsorption, readsorption, and bond-formation processes, to be performed by using the STM tip. Complete sequences of chemical reactions are able to induce at a single-molecule level. New molecules can be constructed from the basic molecular building blocks on a one-molecule-at-a-time basis by using a variety of STM manipulation schemes in a systematic step-by-step manner. These achievements open up entirely new opportunities in nanochemistry and nanochemical technology. In this review, various STM manipulation techniques useful in the single-molecule reaction process are reviewed, and their impact on the future of nanoscience and technology are discussed.

  20. Theory of nonlinear phononics for coherent light control of solids

    NASA Astrophysics Data System (ADS)

    Subedi, Alaska; Cavalleri, Andrea; Georges, Antoine

    2014-06-01

    We present a microscopic theory for ultrafast control of solids with high-intensity terahertz frequency optical pulses. When resonant with selected infrared-active vibrations, these pulses transiently modify the crystal structure and lead to new collective electronic properties. The theory predicts the dynamical path taken by the crystal lattice using first-principles calculations of the energy surface and classical equations of motion, as well as symmetry considerations. Two classes of dynamics are identified. In the perturbative regime, displacements along the normal mode coordinate of symmetry-preserving Raman active modes can be achieved by cubic anharmonicities. This explains the light-induced insulator-to-metal transition reported experimentally in manganites. We predict a regime in which ultrafast instabilities that break crystal symmetry can be induced. This nonperturbative effect involves a quartic anharmonic coupling and occurs above a critical threshold, below which the nonlinear dynamics of the driven mode displays softening and dynamical stabilization.

  1. Controlled Orientation of Polyconjugated Guest Molecules in Tunable Host Cavities

    SciTech Connect

    Soegiarto, Airon C.; Comotti, Angiolina; Ward, Michael D.

    2010-12-07

    Linear conjugated guest molecules with high aspect ratios form inclusion compounds with guanidinium organodisulfonate (GDS) host frameworks in which organodisulfonate 'pillars' connect opposing GS sheets to generate lamellar architectures that reflect templating by the guest. Through judicious selection of pillars having adjustable lengths (l{sub S-S}, as measured by the separation between distal sulfur atoms) and guests of various lengths (l{sub g}), the framework architecture can be controlled systematically in a manner that enables regulation of the guest orientation and aggregation in the host framework. Inclusion compounds for which l{sub g}/l{sub S-S} {le} 0.9 exhibit a bilayer architecture with 1-D channels containing guests oriented parallel to the long axis of the pillar. Guests with values of l{sub g} comparable to l{sub S-S}, however, promote the formation of a brick architecture in which the guests and the pillar are arranged in a herringbone motif. Surprisingly, longer guests (l{sub g} = 1.25l{sub S-S}) favor the formation of the bilayer architecture despite their larger volume because the guests are forced to align end-to-end as single-file arrays due to the vertical constraints of the 1-D channels. Bithiophene and biphenyl guests (l{sub g} < l{sub S-S}) are exceptional, promoting bilayer structures in which turnstile rotations of the pillars afford an unusual motif in which the guests are isolated from one another. The ability to synthesize a large family of compounds based on a common supramolecular building block (the GS sheet) permits construction of a structural 'phase diagram' based on two simple molecular parameters, l{sub g} and l{sub S-S}, that can be used to sort the inclusion compounds according to their framework architectures and enable prediction of crystal structures for new host-guest combinations. The effects of these different framework architectures and packing motifs is manifested as bathochromic shifts in the absorption and

  2. Coherent control in quantum transport: amplification, filtering and switching at finite bias

    NASA Astrophysics Data System (ADS)

    Thethi, Rajpal; Emary, Clive

    2017-06-01

    We consider coherent feedback control of quantum transport and focus on the application of simple controllers and the effects of a finite bias voltage. We show that simple single-parameter controllers can give rise to a range of useful effects such as amplification of changes in plant transmission, increased resolution of energy filtration, and the detection of differences between otherwise indistinguishable plants. We explore how these effects are impacted by the phase-averaging effects associated with finite bias and identify important voltage scales for the maintenance of the functionalities achieved through feedback control.

  3. Quantum Coherent Feedback Control for Generation System of Optical Entangled State

    PubMed Central

    Zhou, Yaoyao; Jia, Xiaojun; Li, Fang; Yu, Juan; Xie, Changde; Peng, Kunchi

    2015-01-01

    The non-measurement based coherent feedback control (CFC) is a control method without introducing any backaction noise into the controlled system, thus is specially suitable to manipulate various quantum optical systems for preparing nonclassical states of light. By simply tuning the transmissivity of an optical controller in a CFC loop attached to a non-degenerate optical parametric amplifier (NOPA), the quantum entanglement degree of the output optical entangled state of the system is improved. At the same time, the threshold pump power of the NOPA is reduced also. The experimental results are in reasonable agreement with the theoretical expectation. PMID:26047357

  4. Control of anisotropic interactions with microwaves in ultracold NaK molecules

    NASA Astrophysics Data System (ADS)

    Yan, Zoe; Loh, Huanqian; Park, Jee Woo; Will, Sebastian; Zwierlein, Martin

    2016-05-01

    Ultracold polar molecules offer long range anisotropic interactions, which can provide access to novel phases of condensed matter physics. The recent creation of fermionic NaK polar molecules in the ground hyperfine-rovibronic state, which is chemically stable, demonstrates an important step towards the study of new dipolar physics. To engineer dipolar interactions between molecules with large electric dipole moments, one can apply microwaves to mix the lowest and first excited rotational states. Hyperfine interaction in the first excited rotational state mixes nuclear spin and rotation, leading to states with rich character, which we map out by performing microwave spectroscopy. The admixed hyperfine character serves as a tool to engineer wide ranges of ``magic'' trap polarization angles, at which the lowest and first excited rotational states have matching polarizabilities. Finally, we demonstrate that we can access large dipole moments by coherently dressing the molecules with microwaves.

  5. Investigating the Use of Coherence Analysis on Mandibular Electromyograms to Investigate Neural Control of Early Oromandibular Behaviours: A Pilot Study

    ERIC Educational Resources Information Center

    Steeve, Roger W.; Price, Christiana M.

    2010-01-01

    An empirical method for investigating differences in neural control of jaw movement across oromandibular behaviours is to compute the coherence function for electromyographic signals obtained from mandibular muscle groups. This procedure has been used with adults but not extended to children. This pilot study investigated if coherence analysis…

  6. Investigating the Use of Coherence Analysis on Mandibular Electromyograms to Investigate Neural Control of Early Oromandibular Behaviours: A Pilot Study

    ERIC Educational Resources Information Center

    Steeve, Roger W.; Price, Christiana M.

    2010-01-01

    An empirical method for investigating differences in neural control of jaw movement across oromandibular behaviours is to compute the coherence function for electromyographic signals obtained from mandibular muscle groups. This procedure has been used with adults but not extended to children. This pilot study investigated if coherence analysis…

  7. Characteristic oscillations in the coherent transients of ultracold rubidium molecules using red and blue detuned pulses for photoassociation

    NASA Astrophysics Data System (ADS)

    Weise, Fabian; Merli, Andrea; Eimer, Frauke; Birkner, Sascha; Sauer, Franziska; Wöste, Ludger; Lindinger, Albrecht; Salzmann, Wenzel; Mullins, Terence G.; Wester, Roland; Weidemüller, Matthias; Ağanoğlu, Ruzin; Koch, Christiane P.

    2009-11-01

    We investigate the interaction of femtosecond laser pulses with an ensemble of ultracold rubidium atoms by applying shaped excitation pulses with two different types of spectral filtering. Although the pulses, which are frequency filtered with a high pass, have no spectral overlap with molecular states, we observe coherent molecular transients. Similar transients obtained with nearly transform-limited pulses, where only the atomic resonance is removed, reveal two differing oscillatory components. The resulting transients are compared among themselves and supported with quantum dynamical simulations which indicate a photoassociation process. The effect is due to the strong field interaction of the pulse with the colliding atom pair.

  8. Control of cell interaction using quasi-monochromatic light with varying spatiotemporal coherence

    NASA Astrophysics Data System (ADS)

    Budagovsky, A. V.; Maslova, M. V.; Budagovskaya, O. N.; Budagovsky, I. A.

    2017-02-01

    By the example of plants, fungi and bacteria, we consider the possibility of controlling the interaction of cells, being in competitive, antagonistic, or parasitic relations. For this aim we used short-time irradiation (a few seconds or minutes) with the red (633 nm) quasi-monochromatic light having different spatiotemporal coherence. It is shown that the functional activity is mostly increased in the cells whose size does not exceed the coherence length and the correlation radius of the light field. Thus, in the case of cells essentially differing in size, it is possible to increase the activity of smaller cells, avoiding the stimulation of larger ones. For example, the radiation having relatively low coherence (Lcoh, rcor <= 10 μm) facilitates mainly the damage of large-size plant cells by pathogen fungi, while the exposure to light with less statistical regularity (Lcoh = 4 μm, rcor = 5 μm) inhibits the growth of the Fusarium microcera fungus, infected by the bacterium of the Pseudomonas species. The quasi-monochromatic radiation with sufficiently high spatiotemporal coherence stimulated all interacting species (bacteria, fungi, plants). In the considered biocenosis, the equilibrium was shifted towards the favour of organisms having the highest rate of cell division or the ones better using their adaptation potential.

  9. Nonresonant coherent control: Intersubband excitations manipulated by a nonresonant terahertz pulse

    NASA Astrophysics Data System (ADS)

    Folpini, Giulia; Morrill, Drew; Somma, Carmine; Reimann, Klaus; Woerner, Michael; Elsaesser, Thomas; Biermann, Klaus

    2015-08-01

    We present an approach for controlling quantum coherences in condensed matter by interaction with a nonresonant optical control field. Coherent intersubband (IS) excitations of electrons in GaAs/AlGaAs quantum wells are manipulated by a strong nonresonant terahertz (THz) field as demonstrated by phase-resolved two-color two-dimensional spectroscopy. In the linear regime of IS response, we observe a THz-induced enhancement of the midinfrared (MIR) IS absorption and a dispersive perturbed free induction decay caused by a THz-induced blueshift of the IS polarization. In the regime of IS Rabi oscillations, the THz field causes pronounced phase shifts of the coherently emitted MIR field, while the IS Rabi frequency remains unaffected. Such behavior is accounted for by a full solution of the Maxwell-Bloch equations, treating the THz and MIR fields without approximations. Our control scheme paves the way for THz control of IS emitters and holds potential for an extension to other systems.

  10. Controlled spatial separation of spins and coherent dynamics in spin-orbit-coupled nanostructures

    NASA Astrophysics Data System (ADS)

    Lo, Shun-Tsung; Chen, Chin-Hung; Fan, Ju-Chun; Smith, L. W.; Creeth, G. L.; Chang, Che-Wei; Pepper, M.; Griffiths, J. P.; Farrer, I.; Beere, H. E.; Jones, G. A. C.; Ritchie, D. A.; Chen, Tse-Ming

    2017-07-01

    The spatial separation of electron spins followed by the control of their individual spin dynamics has recently emerged as an essential ingredient in many proposals for spin-based technologies because it would enable both of the two spin species to be simultaneously utilized, distinct from most of the current spintronic studies and technologies wherein only one spin species could be handled at a time. Here we demonstrate that the spatial spin splitting of a coherent beam of electrons can be achieved and controlled using the interplay between an external magnetic field and Rashba spin-orbit interaction in semiconductor nanostructures. The technique of transverse magnetic focusing is used to detect this spin separation. More notably, our ability to engineer the spin-orbit interactions enables us to simultaneously manipulate and probe the coherent spin dynamics of both spin species and hence their correlation, which could open a route towards spintronics and spin-based quantum information processing.

  11. Controlled spatial separation of spins and coherent dynamics in spin-orbit-coupled nanostructures

    PubMed Central

    Lo, Shun-Tsung; Chen, Chin-Hung; Fan, Ju-Chun; Smith, L. W.; Creeth, G. L.; Chang, Che-Wei; Pepper, M.; Griffiths, J. P.; Farrer, I.; Beere, H. E.; Jones, G. A. C.; Ritchie, D. A.; Chen, Tse-Ming

    2017-01-01

    The spatial separation of electron spins followed by the control of their individual spin dynamics has recently emerged as an essential ingredient in many proposals for spin-based technologies because it would enable both of the two spin species to be simultaneously utilized, distinct from most of the current spintronic studies and technologies wherein only one spin species could be handled at a time. Here we demonstrate that the spatial spin splitting of a coherent beam of electrons can be achieved and controlled using the interplay between an external magnetic field and Rashba spin–orbit interaction in semiconductor nanostructures. The technique of transverse magnetic focusing is used to detect this spin separation. More notably, our ability to engineer the spin–orbit interactions enables us to simultaneously manipulate and probe the coherent spin dynamics of both spin species and hence their correlation, which could open a route towards spintronics and spin-based quantum information processing. PMID:28691707

  12. Controlled spatial separation of spins and coherent dynamics in spin-orbit-coupled nanostructures.

    PubMed

    Lo, Shun-Tsung; Chen, Chin-Hung; Fan, Ju-Chun; Smith, L W; Creeth, G L; Chang, Che-Wei; Pepper, M; Griffiths, J P; Farrer, I; Beere, H E; Jones, G A C; Ritchie, D A; Chen, Tse-Ming

    2017-07-10

    The spatial separation of electron spins followed by the control of their individual spin dynamics has recently emerged as an essential ingredient in many proposals for spin-based technologies because it would enable both of the two spin species to be simultaneously utilized, distinct from most of the current spintronic studies and technologies wherein only one spin species could be handled at a time. Here we demonstrate that the spatial spin splitting of a coherent beam of electrons can be achieved and controlled using the interplay between an external magnetic field and Rashba spin-orbit interaction in semiconductor nanostructures. The technique of transverse magnetic focusing is used to detect this spin separation. More notably, our ability to engineer the spin-orbit interactions enables us to simultaneously manipulate and probe the coherent spin dynamics of both spin species and hence their correlation, which could open a route towards spintronics and spin-based quantum information processing.

  13. Coherent control with optical pulses for deterministic spin-photon entanglement

    NASA Astrophysics Data System (ADS)

    Truex, Katherine; Webster, L. A.; Duan, L.-M.; Sham, L. J.; Steel, D. G.

    2013-11-01

    We present a procedure for the optical coherent control of quantum bits within a quantum dot spin-exciton system, as a preliminary step to implementing a proposal by Yao, Liu, and Sham [Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.95.030504 95, 030504 (2005)] for deterministic spin-photon entanglement. The experiment proposed here utilizes a series of picosecond optical pulses from a single laser to coherently control a single self-assembled quantum dot in a magnetic field, creating the precursor state in 25 ps with a predicted fidelity of 0.991. If allowed to decay in an appropriate cavity, the ideal precursor superposition state would create maximum spin-photon entanglement. Numerical simulations using values typical of InAs quantum dots give a predicted entropy of entanglement of 0.929, largely limited by radiative decay and electron spin flips.

  14. Coherent control of quantum tunneling in different driving-frequency regions

    SciTech Connect

    Lu, Gengbiao; Hai, Wenhua; Zhong, Honghua; Xie, Qiongtao

    2010-06-15

    We investigate the coherent control of quantum tunneling for a single particle held in a driven double-well potential. For a moderate-frequency region, we demonstrate that the irregular quantum tunneling is associated with classically chaotic dynamics. A set of lower resonance-like frequencies is found, for which the coherent destruction of tunneling in the sense of the time average is illustrated numerically. For a high-frequency region, it is shown that the particle is located at the bottom of each well alternately for a long time and the time located in one well can be modulated by adjusting the driving field. The results could be useful for the experiments of controlling single-particle tunneling [see, e.g., E. Kierig, U. Schnorrberger, A. Schietinger, J. Tomkovic, and M. K. Oberthaler, Phys. Rev. Lett. 100, 190405 (2008).].

  15. Coherent Control and Manipulation of Three Spin States in a Triple Quantum Dot

    NASA Astrophysics Data System (ADS)

    Sachrajda, Andrew

    2013-03-01

    The triple quantum dot energy level spectrum is far more complex than its double quantum dot counterpart. As a result it is a challenge to cleanly manipulate only the two required qubit states without invoking more complex multi- state coherent evolution. In this talk I will describe experiments and modeling of lateral triple quantum dot devices where by suitable device gate (i.e. energy level spectrum) tuning and pulse characteristics we were able to characterize and manipulate various three spin qubit species. In particular I will describe measurements where the Landau-Zener -Stückelberg approach previously demonstrated in double dots is extended to three- interacting spin states permitting us to demonstrate phenomena such as pairwise exchange control. I will also demonstrate how by tuning the experimental parameters one can controllably switch to coherent oscillations originating from alternative potentially useful qubit states and how to distinguish them. This work was funded by NRC, NSERC and CIFAR.

  16. Optical Realization of Double-Continuum Fano Interference and Coherent Control in Plasmonic Metasurfaces.

    PubMed

    Arju, Nihal; Ma, Tzuhsuan; Khanikaev, Alexander; Purtseladze, David; Shvets, Gennady

    2015-06-12

    Classical realization of a ubiquitous quantum mechanical phenomenon of double-continuum Fano interference using metasurfaces is experimentally demonstrated by engineering the near-field interaction between two bright and one dark plasmonic modes. The competition between the bright modes, one of them effectively suppressing the Fano interference for the orthogonal light polarization, is discovered. Coherent control of optical energy concentration and light absorption by the ellipticity of the incident light is theoretically predicted.

  17. Optical Realization of Double-Continuum Fano Interference and Coherent Control in Plasmonic Metasurfaces

    NASA Astrophysics Data System (ADS)

    Arju, Nihal; Ma, Tzuhsuan; Khanikaev, Alexander; Purtseladze, David; Shvets, Gennady

    2015-06-01

    Classical realization of a ubiquitous quantum mechanical phenomenon of double-continuum Fano interference using metasurfaces is experimentally demonstrated by engineering the near-field interaction between two bright and one dark plasmonic modes. The competition between the bright modes, one of them effectively suppressing the Fano interference for the orthogonal light polarization, is discovered. Coherent control of optical energy concentration and light absorption by the ellipticity of the incident light is theoretically predicted.

  18. Coherence-Controlled Nonadiabatic Dynamics via State-Space Decomposition: A Consistent Way To Incorporate Ehrenfest and Born-Oppenheimer-Like Treatments of Nuclear Motion.

    PubMed

    Tao, Guohua

    2016-11-03

    Accurately describing nuclear motion is crucial in electronically nonadiabatic dynamics simulations. In this work, a coherence-controlled (CC) approach is proposed based on the mapping between the classical state space and the full electronic matrix and that between the decomposed state space and different nuclear dynamics that allows nuclear motion to properly follow either Ehrenfest dynamics in the coherence domain or Born-Oppenheimer-like dynamics in the single-state domain in a consistent manner. This new method is applied to several benchmark models involving nonadiabatic transitions in two-state or three-state systems, and the obtained results are in excellent agreement with exact quantum calculations. As a generalization of the recently developed symmetrical quasiclassical approach and the augmented image (AI) version of the multistate trajectory approach, the proposed method is extremely efficient and numerically stable. Therefore, it has great potential for implementation in nonadiabatic molecular dynamics simulations for realistic complex systems, such as materials and biological molecules.

  19. Synthesis of technomimetic molecules: towards rotation control in single-molecular machines and motors.

    PubMed

    Rapenne, Gwénaël

    2005-04-07

    Technomimetic molecules are molecules designed to imitate macroscopic objects at the molecular level, also transposing the motions that these objects are able to undergo. This article focuses on technomimetic molecules with rotary motions, including gears, wheelbarrows and motors. Following the bottom-up approach the synthesis of technomimetic molecules grants access to the study of mechanical properties at the molecular level. These molecules are designed to operate as single molecules on surfaces under the control of the tip of a scanning tunneling microscope or atomic force microscope.

  20. Control of coherent excitation of neon in the extreme ultraviolet regime.

    PubMed

    Plenge, Jürgen; Wirsing, Andreas; Raschpichler, Christopher; Wassermann, Bernhard; Rühl, Eckart

    2011-01-01

    Coherent excitation of a superposition of Rydberg states in neon by the 13th harmonic of an intense 804 nm pulse and the formation of a wave packet is reported. Pump-probe experiments are performed, where the 3d-manifold of the 2p6-->2p5 (2P3/2) 3d [1/2]1- and 2p6-->2p5 (2P3/2) 3d [3/2]1-transitions are excited by an extreme ultraviolet (XUV) radiation pulse, which is centered at 20.05 eV photon energy. The temporal evolution of the excited state population is probed by ionization with a time-delayed 804 nm pulse. Control of coherent transient excitation and wave packet dynamics in the XUV-regime is demonstrated, where the spectral phase of the 13th harmonic is used as a control parameter. Modulation of the phase is achieved by propagation of the XUV-pulse through neon of variable gas density. The experimental results indicate that phase-shaped high-order harmonics can be used to control fundamental coherent excitation processes in the XUV-regime.

  1. Coherent control of radiation patterns of nonlinear multiphoton processes in nanoparticles

    PubMed Central

    Papoff, Francesco; McArthur, Duncan; Hourahine, Ben

    2015-01-01

    We propose a scheme for the coherent control of light waves and currents in metallic nanospheres which applies independently of the nonlinear multiphoton processes at the origin of waves and currents. We derive conditions on the external control field which enable us to change the radiation pattern and suppress radiative losses or to reduce absorption, enabling the particle to behave as a perfect scatterer or as a perfect absorber. The control introduces narrow features in the response of the particles that result in high sensitivity to small variations in the local environment, including subwavelength spatial shifts. PMID:26155833

  2. Coherent control in strongly driven multi-level systems: quantum vs classical features

    NASA Astrophysics Data System (ADS)

    Ivanov, Misha; Bartram, David; Smirnova, Olga

    2012-08-01

    We look at wavepacket dynamics in multi-level systems driven by resonant two-colour fields. We show that control of this dynamics, performed by controlling the relative phase between the driving fields, can be mapped on a problem of molecular alignment and orientation on a plane. Changing the relative phase between the two colours corresponds to changing the angle between aligning and orienting fields. This map offers physically transparent qualitative and quantitative insight into the seemingly complex dynamics, including the analysis of quantum versus classical features of the two-colour coherent control.

  3. The Development of the Undulator Controls Module at the Linac Coherent Light Source

    SciTech Connect

    Alarcon, A.D.; /SLAC

    2009-12-11

    The Linac Coherent Light Source, LCLS, at the SLAC National Accelerator Laboratory, SNAL, is the first hard x-ray Free Electron Laser. The Undulator Controls Module, UCM, controls five cams and two translation stages that regulate the position of each of the 33 permanent undulator magnet segments within 10 microns. The UCM package, hardware and software, was designed and built by the Advanced Photon Source at Argonne. Important lessons were learned throughout the collaborative design, installation, testing, and commissioning periods that could be invaluable to future similar controls projects.

  4. Controllable optical bistability and multistability in asymmetric double quantum wells via spontaneously generated coherence

    SciTech Connect

    Chen, Yuan; Deng, Li; Chen, Aixi

    2015-02-15

    We investigate the nonlinear optical phenomena of the optical bistability and multistability via spontaneously generated coherence in an asymmetric double quantum well structure coupled by a weak probe field and a controlling field. It is shown that the threshold and hysteresis cycle of the optical bistability can be conveniently controlled only by adjusting the intensity of the SGC or the controlling field. Moreover, switching between optical bistability and multistability can be achieved. These studies may have practical significance for the preparation of optical bistable switching device.

  5. Small-molecule pheromones and hormones controlling nematode development.

    PubMed

    Butcher, Rebecca A

    2017-05-17

    The existence of small-molecule signals that influence development in Caenorhabditis elegans has been known for several decades, but only in recent years have the chemical structures of several of these signals been established. The identification of these signals has enabled connections to be made between these small molecules and fundamental signaling pathways in C. elegans that influence not only development but also metabolism, fertility, and lifespan. Spurred by these important discoveries and aided by recent advances in comparative metabolomics and NMR spectroscopy, the field of nematode chemistry has the potential to expand dramatically in the coming years. This Perspective will focus on small-molecule pheromones and hormones that influence developmental events in the nematode life cycle (ascarosides, dafachronic acids, and nemamides), will cover more recent work regarding the biosynthesis of these signals, and will explore how the discovery of these signals is transforming our understanding of nematode development and physiology.

  6. All-optical Fresnel lens in coherent media: controlling image with image.

    PubMed

    Zhao, L; Duan, Wenhui; Yelin, S F

    2011-01-17

    We theoretically explore an all-optical method for generating tunable diffractive Fresnel lenses in coherent media based on electromagnetically induced transparency. In this method, intensity-modulated images in coupling light fields can pattern the coherent media to induce the desired modulo-2π quadratic phase profiles for the lenses to diffract probe light fields. We characterize the focusing and imaging properties of the induced lenses. In particular, we show that the images in coupling fields can flexibly control the images in probe fields by diffraction, where large focal length tunability from 1 m to infinity and high output (∼ 88% diffraction efficiency) can be achieved. Additionally, we also find that the induced Fresnel lenses can be rapidly modulated with megahertz refresh rates using image-bearing square pulse trains in coupling fields. Our proposed lenses may find a wide range of applications for multimode all-optical signal processing in both the classical and quantum regimes.

  7. Coherent control of single spins in silicon carbide at room temperature

    NASA Astrophysics Data System (ADS)

    Widmann, Matthias; Lee, Sang-Yun; Rendler, Torsten; Son, Nguyen Tien; Fedder, Helmut; Paik, Seoyoung; Yang, Li-Ping; Zhao, Nan; Yang, Sen; Booker, Ian; Denisenko, Andrej; Jamali, Mohammad; Momenzadeh, S. Ali; Gerhardt, Ilja; Ohshima, Takeshi; Gali, Adam; Janzén, Erik; Wrachtrup, Jörg

    2015-02-01

    Spins in solids are cornerstone elements of quantum spintronics. Leading contenders such as defects in diamond or individual phosphorus dopants in silicon have shown spectacular progress, but either lack established nanotechnology or an efficient spin/photon interface. Silicon carbide (SiC) combines the strength of both systems: it has a large bandgap with deep defects and benefits from mature fabrication techniques. Here, we report the characterization of photoluminescence and optical spin polarization from single silicon vacancies in SiC, and demonstrate that single spins can be addressed at room temperature. We show coherent control of a single defect spin and find long spin coherence times under ambient conditions. Our study provides evidence that SiC is a promising system for atomic-scale spintronics and quantum technology.

  8. Isolation and Control of Spins in Silicon Carbide with Millisecond-Coherence Times

    NASA Astrophysics Data System (ADS)

    Christle, David J.; Falk, Abram L.; Andrich, Paolo; Klimov, Paul V.; Awschalom, David D.; Hassan, Jawad Ul; Son, Nguyen T.; Janzén, Erik; Ohshima, Takeshi

    2015-03-01

    The elimination of defects from silicon carbide (SiC) has facilitated its move to the forefront of the optoelectronics and power-electronics industries. Nonetheless, because the electronic states of SiC defects can have sharp optical and spin transitions, they are increasingly recognized as a valuable resource for quantum-information and nanoscale-sensing applications. We demonstrate that individual electronic spin states of the divacancy defect in highly purified monocrystalline 4H-SiC can be isolated and coherently controlled. This defect has analogous behavior to the prominent nitrogen-vacancy center in diamond, yet exists in a material amenable to modern growth and microfabrication techniques. We spectroscopically identify the different forms of divacancies, and show that divacancy spins exhibit an exceptionally long ensemble Hahn-echo coherence time that exceeds one millisecond. Funding by NSF, AFOSR MURI, and the Knut & Alice Wallenberg Foundation is gratefully acknowledged.

  9. Coherent control of the dynamics of a single quantum-dot exciton qubit in a cavity

    NASA Astrophysics Data System (ADS)

    de Freitas, Antonio; Sanz, L.; Villas-Bôas, José M.

    2017-03-01

    In this paper we demonstrate theoretically how to use an external laser field to control the population inversion of a single quantum dot exciton qubit in a nanocavity. We consider the Jaynes-Cummings model to describe the system, and the incoherent losses were taken into account by using Lindblad operators. We have demonstrated how to prepare the initial state in a superposition of the exciton in the ground state and the cavity in a coherent state. The effects of exciton-cavity detuning, the laser-cavity detunings, the pulse area, and losses over the qubit dynamics are analyzed. We also show how to use a continuous laser pumping in resonance with the cavity mode to sustain a coherent state inside the cavity, providing some protection to the qubit against cavity loss.

  10. Entropic Elasticity Controls Nanomechanics of Single Tropocollagen Molecules

    PubMed Central

    Buehler, Markus J.; Wong, Sophie Y.

    2007-01-01

    We report molecular modeling of stretching single molecules of tropocollagen, the building block of collagen fibrils and fibers that provide mechanical support in connective tissues. For small deformation, we observe a dominance of entropic elasticity. At larger deformation, we find a transition to energetic elasticity, which is characterized by first stretching and breaking of hydrogen bonds, followed by deformation of covalent bonds in the protein backbone, eventually leading to molecular fracture. Our force-displacement curves at small forces show excellent quantitative agreement with optical tweezer experiments. Our model predicts a persistence length ξp ≈ 16 nm, confirming experimental results suggesting that tropocollagen molecules are very flexible elastic entities. We demonstrate that assembly of single tropocollagen molecules into fibrils significantly decreases their bending flexibility, leading to decreased contributions of entropic effects during deformation. The molecular simulation results are used to develop a simple continuum model capable of describing an entire deformation range of tropocollagen molecules. Our molecular model is capable of describing different regimes of elastic and permanent deformation, without relying on empirical parameters, including a transition from entropic to energetic elasticity. PMID:17434941

  11. All-electrical coherent control of the exciton states in a single quantum dot

    NASA Astrophysics Data System (ADS)

    Boyer de La Giroday, A.; Bennett, A. J.; Pooley, M. A.; Stevenson, R. M.; Sköld, N.; Patel, R. B.; Farrer, I.; Ritchie, D. A.; Shields, A. J.

    2010-12-01

    We demonstrate high-fidelity reversible transfer of quantum information from the polarization of photons into the spin state of an electron-hole pair in a semiconductor quantum dot. Moreover, spins are electrically manipulated on a subnanosecond time scale, allowing us to coherently control their evolution. By varying the area of the electrical pulse, we demonstrate phase-shift and spin-flip gate operations with near-unity fidelities. Our system constitutes a controllable quantum interface between flying and stationary qubits, an enabling technology for quantum logic in the solid state.

  12. Spatiotemporal Coherent Control of Light through a Multiple Scattering Medium with the Multispectral Transmission Matrix

    NASA Astrophysics Data System (ADS)

    Mounaix, Mickael; Andreoli, Daria; Defienne, Hugo; Volpe, Giorgio; Katz, Ori; Grésillon, Samuel; Gigan, Sylvain

    2016-06-01

    We report the broadband characterization of the propagation of light through a multiple scattering medium by means of its multispectral transmission matrix. Using a single spatial light modulator, our approach enables the full control of both the spatial and spectral properties of an ultrashort pulse transmitted through the medium. We demonstrate spatiotemporal focusing of the pulse at any arbitrary position and time with any desired spectral shape. Our approach opens new perspectives for fundamental studies of light-matter interaction in disordered media, and has potential applications in sensing, coherent control, and imaging.

  13. Coherent control of interacting particles using dynamical and Aharonov-Bohm phases.

    PubMed

    Creffield, C E; Platero, G

    2010-08-20

    A powerful method of manipulating the dynamics of quantum coherent particles is to control the phase of their tunneling. We consider a system of two electrons hopping on a quasi-one-dimensional lattice in the presence of a uniform magnetic field and study the effect of adding a time-periodic driving potential. We show that the dynamical phases produced by the driving can combine with the Aharonov-Bohm phases to give precise control of the localization and dynamics of the particles, even in the presence of strong particle interactions.

  14. Control of Four-Level Quantum Coherence via Discrete Spectral Shaping of an Optical Frequency Comb

    SciTech Connect

    Stowe, Matthew C.; Peer, Avi; Ye Jun

    2008-05-23

    We present experiments demonstrating high-resolution and wide-bandwidth coherent control of a four-level atomic system in a diamond configuration. A femtosecond frequency comb is used to excite a specific pair of two-photon transitions in cold {sup 87}Rb. The optical-phase-sensitive response of the closed-loop diamond system is studied by controlling the phase of the comb modes with a pulse shaper. Finally, the pulse shape is optimized resulting in a 256% increase in the two-photon transition rate by forcing constructive interference between the mode pairs detuned from an intermediate resonance.

  15. Single pulse phase-control interferometric coherent anti-StokesRaman scattering spectroscopy (CARS)

    SciTech Connect

    Lim, Sang-Hyun; Caster, Allison G.; Leone, Stephen R.

    2005-09-28

    In coherent anti-Stokes Raman scattering spectroscopy (CARS) experiments, usually the amplitude of the signal is measured and the phase information is lost. With a polarization- and phase-controlled pulse shaping technique, the relative phase between the resonant and non-resonant CARS signals is controlled, and spectral interferometry is performed without an interferometer. Both the real and imaginary parts of the background-free resonant CARS spectrum are measured via spectral interferometry between the resonant and non-resonant signals from the same sample. The resonant signal is amplified significantly by homodyne mixing with the non-resonant signal as a local oscillator, greatly improving the detection limit.

  16. Quantum multiscattering interferences in collision-induced coherent electron emission from diatomic molecules by swift ion impact

    NASA Astrophysics Data System (ADS)

    Agueny, H.; Hansen, J. P.

    2016-11-01

    In the intramolecular scattering process, the interference between the rescattered electron waves emanating from each atomic center gives rise to additional oscillations superimposed on the Young-type oscillatory structure in the observed electron intensity. Here we explore numerically this behavior for coherent electron emission from the dimer Rb2 + by fast-moving highly charged ions, which is achieved by solving the two-dimensional time-dependent Schrödinger equation. Well-defined modulations with higher frequency are observed in the momentum distribution of the ejected electron, which are well reproduced by additional quantitative calculations based on the third-order Born series. This demonstrates without ambiguity the dynamic interference induced by multiple scattering paths of the electron prior to emission. Furthermore, the dependence of the phenomenon on the emission direction of the electron and the orientation of the molecular axis also is investigated. The phenomenon is not specific to Rb2 + as investigated in the present study, but is broadly applicable to other systems with sufficiently large internuclear distances, thus opening new prospects for the investigation of electron emission process from large systems.

  17. Coherent Rayleigh-Brillouin scattering for in situ detection of nanoparticles and large molecules in gas and plasma

    NASA Astrophysics Data System (ADS)

    Gerakis, A.; Shneider, M. N.; Stratton, B. C.; Santra, B.; Car, R.; Raitses, Y.

    2016-09-01

    Laser-based diagnostics methods, such as Spontaneous and Coherent Rayleigh and Rayleigh-Brillouin scattering (SRBS and CRBS), can be used for in-situ detection and characterization of nanoparticle shape and size as well as their concentration in an inert gas atmosphere. We recently developed and tested this advanced diagnostic at PPPL. It was shown that the signal intensity of the CRBS signal depends on the gas-nanoparticle mixture composition, density and the polarizabilities of the mixture components. The measured results agree well with theoretical predictions of Refs. In this work, we report the application of this diagnostic to monitor nucleation and growth of nanoparticles in a carbon arc discharge. In support of these measurements, A time-dependent density functional theory was used to compute the frequency-dependent polarizabilities of various nanostructures in order to predict the corresponding Rayleigh scattering intensities as well as light depolarization. Preliminary results of measurements demonstrate that CRBS is capable to detect nanoparticles in volume. This work was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division.

  18. Electrodynamics analysis on coherent perfect absorber and phase-controlled optical switch.

    PubMed

    Chen, Tianjie; Duan, Shaoguang; Chen, Y C

    2012-05-01

    A coherent perfect absorber is essentially a specially designed Fabry-Perot interferometer, which completely extinguishes the incident coherent light. The one- and two-beam coherent perfect absorbers have been analyzed using classical electrodynamics by considering index matching in layered structures to totally suppress reflections. This approach presents a clear and physically intuitive picture for the principle of operation of a perfect absorber. The results show that the incident beam(s) must have correct phases and amplitudes, and the real and imaginary parts of the refractive indices of the media in the interferometer must satisfy a well-defined relation. Our results are in agreement with those obtained using the S-matrix analysis. However, the results were obtained solely based on the superposition of waves from multiple reflections without invoking the concept of time reversal as does the S-matrix approach. Further analysis shows that the two-beam device can be configured to function as a phase-controlled three-state switch.

  19. Control of laser wavelength tuning and its application in coherent optical time domain reflectometer

    NASA Astrophysics Data System (ADS)

    Lu, Lidong; Sun, Xiaoyan; Li, Binglin

    2017-02-01

    A laser diode temperature control scheme is adopted to achieve the laser wavelength tuning of a narrow linewidth laser, which sends commands by serial communication to change the laser diode temperature. The laser diode temperature is presented by the temperature sensitive resistance. And then the laser wavelength tuning method is also used in a coherent optical time domain reflectometer (C-OTDR) to reduce the coherent Rayleigh noise (CRN) caused by the coherence of the narrow linewidth laser. As the serial communication for the laser wavelength tuning is time-consuming which costs at least 10ms to finish the wavelength tuning once, the measurement time and efficiency of the C-OTDR should be considered. And then the relationship between the times for the laser wavelength changing and the CRN fluctuation is experimentally studied to balance the measurement time consumption and the measurement results, which illustrates that the laser wavelength needs not be changed in each measurement period of the C-OTDR and it can also obtain the ideal result to change the laser wavelength every 500 measurement periods. In traditional C-OTDR, by serial communication, the laser wavelength is changed in each measurement period and the total measurement periods are 218, so by the new scheme it can save about 2600 seconds to achieve an ideal measurement, which is of high efficiency.

  20. Controllable binding of polar molecules and metastability of one-dimensional gases with attractive dipole forces.

    PubMed

    Byrd, Jason N; Montgomery, John A; Côté, Robin

    2012-08-24

    We explore one-dimensional samples of ultracold polar molecules with attractive dipole-dipole interactions and show the existence of a repulsive barrier caused by a strong quadrupole interaction between molecules. This barrier can stabilize a gas of ultracold KRb molecules and even lead to long-range wells supporting bound states between the molecules. The properties of these wells can be controlled by external electric fields, allowing the formation of long polymerlike chains of KRb and studies of quantum phase transitions by varying the effective interaction between molecules. We discuss the generalization of those results to other systems.

  1. Approximation of reachable sets for coherently controlled open quantum systems: Application to quantum state engineering

    NASA Astrophysics Data System (ADS)

    Li, Jun; Lu, Dawei; Luo, Zhihuang; Laflamme, Raymond; Peng, Xinhua; Du, Jiangfeng

    2016-07-01

    Precisely characterizing and controlling realistic quantum systems under noises is a challenging frontier in quantum sciences and technologies. In developing reliable controls for open quantum systems, one is often confronted with the problem of the lack of knowledge on the system controllability. The purpose of this paper is to give a numerical approach to this problem, that is, to approximately compute the reachable set of states for coherently controlled quantum Markovian systems. The approximation consists of setting both upper and lower bounds for system's reachable region of states. Furthermore, we apply our reachability analysis to the control of the relaxation dynamics of a two-qubit nuclear magnetic resonance spin system. We implement some experimental tasks of quantum state engineering in this open system at a near optimal performance in view of purity: e.g., increasing polarization and preparing pseudopure states. These results demonstrate the usefulness of our theory and show interesting and promising applications of environment-assisted quantum dynamics.

  2. Coherent detectors

    NASA Astrophysics Data System (ADS)

    Lawrence, C. R.; Church, S.; Gaier, T.; Lai, R.; Ruf, C.; Wollack, E.

    2009-03-01

    Coherent systems offer significant advantages in simplicity, testability, control of systematics, and cost. Although quantum noise sets the fundamental limit to their performance at high frequencies, recent breakthroughs suggest that near-quantum-limited noise up to 150 or even 200 GHz could be realized within a few years. If the demands of component separation can be met with frequencies below 200 GHz, coherent systems will be strong competitors for a space CMB polarization mission. The rapid development of digital correlator capability now makes space interferometers with many hundreds of elements possible. Given the advantages of coherent interferometers in suppressing systematic effects, such systems deserve serious study.

  3. Two-Color Coherent Control of Optical Bistability in Asymmetric Semiconductor Quantum Wells

    NASA Astrophysics Data System (ADS)

    Li, Jia-Hua; Hao, Xiang-Ying

    We investigate optical bistability in intersubband transitions of an asymmetric semiconductor quantum well structure that has equidistant transitions between three subbands of the system and is placed in a unidirectional cavity. The system is simultaneously coupled by a fundamental field and its second harmonic. The second harmonic field acts as a control field and significantly influences the optical bistability. In addition, the two-color coherent control of optical bistability by the relative phase of the fundamental and the second harmonic fields is shown. The influence of the electronic cooperation parameter on the OB behavior is also discussed. This investigation may be used for optimizing and controlling the optical switching process in the SQW solid-state system, which is much more practical than that in the atomic system because of its flexible design and the controllable interference strength.

  4. Coherent phase control of resonance-mediated two-photon absorption in rare-earth ions

    SciTech Connect

    Zhang, Shian Lu, Chenhui; Jia, Tianqing; Sun, Zhenrong; Qiu, Jianrong

    2013-11-04

    We theoretically and experimentally demonstrate the quantum coherent control of the resonance-mediated two-photon absorption in rare-earth ions by the phase-shaped femtosecond laser pulse. Our theoretical results show that the resonance-mediated two-photon absorption can be effectively controlled, but the control efficiency depends on the laser repetition rate in real experiment due to the long lifetime and the short decoherence time of the excited state, and the larger laser repetition rate yields the lower control efficiency. These theoretical results are experimentally confirmed in glass sample doped with Er{sup 3+} by utilizing the femtosecond lasers with low repetition rate of 1 kHz and high repetition rate of 80 MHz.

  5. Two-Color Coherent Control of Femtosecond Above-Threshold Photoemission from a Tungsten Nanotip.

    PubMed

    Förster, Michael; Paschen, Timo; Krüger, Michael; Lemell, Christoph; Wachter, Georg; Libisch, Florian; Madlener, Thomas; Burgdörfer, Joachim; Hommelhoff, Peter

    2016-11-18

    We demonstrate coherent control of multiphoton and above-threshold photoemission from a single solid-state nanoemitter driven by a fundamental and a weak second harmonic laser pulse. Depending on the relative phase of the two pulses, electron emission is modulated with a contrast of the oscillating current signal of up to 94%. Electron spectra reveal that all observed photon orders are affected simultaneously and similarly. We confirm that photoemission takes place within 10 fs. Accompanying simulations indicate that the current modulation with its large contrast results from two interfering quantum pathways leading to electron emission.

  6. Two-Color Coherent Control of Femtosecond Above-Threshold Photoemission from a Tungsten Nanotip

    NASA Astrophysics Data System (ADS)

    Förster, Michael; Paschen, Timo; Krüger, Michael; Lemell, Christoph; Wachter, Georg; Libisch, Florian; Madlener, Thomas; Burgdörfer, Joachim; Hommelhoff, Peter

    2016-11-01

    We demonstrate coherent control of multiphoton and above-threshold photoemission from a single solid-state nanoemitter driven by a fundamental and a weak second harmonic laser pulse. Depending on the relative phase of the two pulses, electron emission is modulated with a contrast of the oscillating current signal of up to 94%. Electron spectra reveal that all observed photon orders are affected simultaneously and similarly. We confirm that photoemission takes place within 10 fs. Accompanying simulations indicate that the current modulation with its large contrast results from two interfering quantum pathways leading to electron emission.

  7. Coherent control of light-matter interactions in polarization standing waves

    PubMed Central

    Fang, Xu; MacDonald, Kevin F.; Plum, Eric; Zheludev, Nikolay I.

    2016-01-01

    We experimentally demonstrate that standing waves formed by two coherent counter-propagating light waves can take a variety of forms, offering new approaches to the interrogation and control of polarization-sensitive light-matter interactions in ultrathin (subwavelength thickness) media. In contrast to familiar energy standing waves, polarization standing waves have constant electric and magnetic energy densities and a periodically varying polarization state along the wave axis. counterintuitively, anisotropic ultrathin (meta)materials can be made sensitive or insensitive to such polarization variations by adjusting their azimuthal angle. PMID:27514307

  8. Generation and coherent control of pure spin currents via terahertz pulses

    NASA Astrophysics Data System (ADS)

    Schüler, Michael; Berakdar, Jamal

    2014-04-01

    We inspect the time and spin-dependent, inelastic tunneling in engineered semiconductor-based double quantum well driven by time-structured terahertz pulses. An essential ingredient is an embedded spin-active structure with vibrational modes that scatter the pulse driven carriers. Due to the different time scales of the charge and spin dynamics, the spin-dependent electron-vibron coupling may result in pure net spin current (with negligible charge current). Heating the vibrational site may affect the resulting spin current. Furthermore, by controlling the charge dynamics, the spin dynamics and the generated spin current can be manipulated and switched on and off coherently.

  9. Large-signal coherent control of normal modes in quantum-well semiconductor microcavity

    SciTech Connect

    Lee, Y.-S.; Norris, T. B.; Maslov, A.; Citrin, D. S.; Prineas, J.; Khitrova, G.; Gibbs, H. M.

    2001-06-18

    We demonstrate coherent control of the cavity-polariton modes of a quantum-well semiconductor microcavity in a two-color scheme. The cavity enhancement of the excitonic nonlinearity gives rise to a large signal; modulating the relative phase of the excitation pulses between zero and {pi} produces a differential reflectivity ({Delta}R/R) of up to 20%. The maximum nonlinear signal is obtained for cocircular pump and probe polarization. Excitation-induced dephasing is responsible for the incoherent nonlinear response, and limits the contrast ratio of the optical switching. {copyright} 2001 American Institute of Physics.

  10. Coherent control of light-matter interactions in polarization standing waves

    NASA Astrophysics Data System (ADS)

    Fang, Xu; MacDonald, Kevin F.; Plum, Eric; Zheludev, Nikolay I.

    2016-08-01

    We experimentally demonstrate that standing waves formed by two coherent counter-propagating light waves can take a variety of forms, offering new approaches to the interrogation and control of polarization-sensitive light-matter interactions in ultrathin (subwavelength thickness) media. In contrast to familiar energy standing waves, polarization standing waves have constant electric and magnetic energy densities and a periodically varying polarization state along the wave axis. counterintuitively, anisotropic ultrathin (meta)materials can be made sensitive or insensitive to such polarization variations by adjusting their azimuthal angle.

  11. Realization of a time-domain Fresnel lens with coherent control.

    PubMed

    Degert, Jérôme; Wohlleben, Wendel; Chatel, Béatrice; Motzkus, Marcus; Girard, Bertrand

    2002-11-11

    Perturbative chirped pulse excitation leads to oscillations of the excited state amplitude. These coherent transients are governed by interferences between resonant and off-resonant contributions. Control mechanisms in both frequency and time domain are used to modify these dynamics. First, by applying a phase step in the spectrum, we manipulate the phase of the oscillations. By direct analogy with Fresnel zone lenses, we then conceive highly phase-amplitude modulated pulse shapes that slice destructive interferences out of the excitation time structure and enhance the final population.

  12. Dynamic control of coherent orbital-angular-momentum beams in turbid environments

    NASA Astrophysics Data System (ADS)

    Morgan, K. S.; Miller, J. K.; Cochenour, B. M.; Johnson, E. G.

    2016-05-01

    This work examines the propagation properties of two superimposed coherent orbital angular momentum (OAM) modes for use in underwater systems as an alternative to amplitude modulation. An OAM mode of l=+2 is interfered with OAM mode l=-1 from a λ = 540 nm laser source. These OAM modes are superimposed using a Mach-Zehnder (MZ) interferometer combined with diffractive optical elements. By manipulating the optical path length of one of the MZ legs, the interference of these beams can be temporally controlled. The spatial profile is maintained in a turbid environment up through 4.9 attenuation lengths for both cases.

  13. Ultrafast all-optical coherent control of single silicon vacancy colour centres in diamond

    PubMed Central

    Becker, Jonas Nils; Görlitz, Johannes; Arend, Carsten; Markham, Matthew; Becher, Christoph

    2016-01-01

    Complete control of the state of a quantum bit (qubit) is a fundamental requirement for any quantum information processing (QIP) system. In this context, all-optical control techniques offer the advantage of a well-localized and potentially ultrafast manipulation of individual qubits in multi-qubit systems. Recently, the negatively charged silicon vacancy centre (SiV−) in diamond has emerged as a novel promising system for QIP due to its superior spectral properties and advantageous electronic structure, offering an optically accessible Λ-type level system with large orbital splittings. Here, we report on all-optical resonant as well as Raman-based coherent control of a single SiV− using ultrafast pulses as short as 1 ps, significantly faster than the centre's phonon-limited ground state coherence time of about 40 ns. These measurements prove the accessibility of a complete set of single-qubit operations relying solely on optical fields and pave the way for high-speed QIP applications using SiV− centres. PMID:27841265

  14. Coherent combining of pulsed fiber amplifiers in the nonlinear chirp regime with intra-pulse phase control.

    PubMed

    Palese, Stephen; Cheung, Eric; Goodno, Gregory; Shih, Chun-Ching; Di Teodoro, Fabio; McComb, Timothy; Weber, Mark

    2012-03-26

    Two high pulse contrast (> 95 dB) polarization maintaining all-fiber amplifier chains were coherently combined to generate 0.42 mJ, 1 ns 25 kHz pulses with 79% efficiency despite 38 radians of intra-pulse phase distortion. A recursive intra-pulse phase compensation method was utilized to correct for the large nonlinear chirp providing a path for improved coherent waveform control of nanosecond pulse trains.

  15. Using strain to control molecule chemisorption on silicene

    NASA Astrophysics Data System (ADS)

    Marjaoui, Adil; Stephan, Régis; Hanf, Marie-Christine; Diani, Mustapha; Sonnet, Philippe

    2017-07-01

    The strain dependence of benzene chemisorption on a silicene freestanding layer has been studied by means of density functional theory calculations. It appears that the molecule, which is adsorbed via a [4+2] pseudo-cycloaddition on the substrate, is more stable when adsorbed on strained than on unstrained silicene since the adsorption energy increases (in absolute value) with tensile or compressive strain. These results, which were not easily predictable, are interpreted in terms of strain-induced reinforcement of the Si-C bonds, formation of a pz-like atomic orbital at the silicene atoms, which augments the silicene reactivity and, for compressive or large tensile strains, increasing of the sp3 character of the Si-Si bonds.

  16. Motion and Form Coherence Detection in Autistic Spectrum Disorder: Relationship to Motor Control and 2:4 Digit Ratio

    ERIC Educational Resources Information Center

    Milne, Elizabeth; White, Sarah; Campbell, Ruth; Swettenham, John; Hansen, Peter; Ramus, Franck

    2006-01-01

    Children with autistic spectrum disorder and controls performed tasks of coherent motion and form detection, and motor control. Additionally, the ratio of the 2nd and 4th digits of these children, which is thought to be an indicator of foetal testosterone, was measured. Children in the experimental group were impaired at tasks of motor control,…

  17. Motion and Form Coherence Detection in Autistic Spectrum Disorder: Relationship to Motor Control and 2:4 Digit Ratio

    ERIC Educational Resources Information Center

    Milne, Elizabeth; White, Sarah; Campbell, Ruth; Swettenham, John; Hansen, Peter; Ramus, Franck

    2006-01-01

    Children with autistic spectrum disorder and controls performed tasks of coherent motion and form detection, and motor control. Additionally, the ratio of the 2nd and 4th digits of these children, which is thought to be an indicator of foetal testosterone, was measured. Children in the experimental group were impaired at tasks of motor control,…

  18. Pupil tracking optical coherence tomography for precise control of pupil entry position

    PubMed Central

    Carrasco-Zevallos, Oscar; Nankivil, Derek; Keller, Brenton; Viehland, Christian; Lujan, Brandon J.; Izatt, Joseph A.

    2015-01-01

    To maximize the collection efficiency of back-scattered light, and to minimize aberrations and vignetting, the lateral position of the scan pivot of an optical coherence tomography (OCT) retinal scanner should be imaged to the center of the ocular pupil. Additionally, several retinal structures including Henle’s Fiber Layer (HFL) exhibit reflectivities that depend on illumination angle, which can be controlled by varying the pupil entry position of the OCT beam. In this work, we describe an automated method for controlling the lateral pupil entry position in retinal OCT by utilizing pupil tracking in conjunction with a 2D fast steering mirror placed conjugate to the retinal plane. We demonstrate that pupil tracking prevents lateral motion artifacts from impeding desired pupil entry locations, and enables precise pupil entry positioning and therefore control of the illumination angle of incidence at the retinal plane. We use our prototype pupil tracking OCT system to directly visualize the obliquely oriented HFL. PMID:26417510

  19. Pupil tracking optical coherence tomography for precise control of pupil entry position.

    PubMed

    Carrasco-Zevallos, Oscar; Nankivil, Derek; Keller, Brenton; Viehland, Christian; Lujan, Brandon J; Izatt, Joseph A

    2015-09-01

    To maximize the collection efficiency of back-scattered light, and to minimize aberrations and vignetting, the lateral position of the scan pivot of an optical coherence tomography (OCT) retinal scanner should be imaged to the center of the ocular pupil. Additionally, several retinal structures including Henle's Fiber Layer (HFL) exhibit reflectivities that depend on illumination angle, which can be controlled by varying the pupil entry position of the OCT beam. In this work, we describe an automated method for controlling the lateral pupil entry position in retinal OCT by utilizing pupil tracking in conjunction with a 2D fast steering mirror placed conjugate to the retinal plane. We demonstrate that pupil tracking prevents lateral motion artifacts from impeding desired pupil entry locations, and enables precise pupil entry positioning and therefore control of the illumination angle of incidence at the retinal plane. We use our prototype pupil tracking OCT system to directly visualize the obliquely oriented HFL.

  20. An intensity modulation and coherent balanced detection intersatellite microwave photonic link using polarization direction control

    NASA Astrophysics Data System (ADS)

    Li, Xuan; Zhu, Zihang; Zhao, Shanghong; Li, Yongjun; Han, Lei; Zhao, Jing

    2014-03-01

    A simple approach for high loss intersatellite microwave photonic link with intensity modulation and coherent balanced detection is proposed. In the transmitter, the double sideband-suppressed carrier (DSB-SC) modulated optical signal and optical carrier (OC) are combined by employing a polarization combiner to chose and control the signals polarization directions, while in the receiver, they are selected respectively by using a polarization splitter for they have orthogonal polarization directions. The separated DSB-SC signal and OC put into balanced detectors and the coherent detection is realized without a local oscillator (LO). At the output, the fundamental signal is augmented and the third-order distortion is suppressed for the DSB-SC modulation, the second-order distortion is removed for the balanced detection and the noise is reduced for the polarization direction control. The signal to noise and distortion ratio (SNDR) can be optimized by adjusting the power of OC and modulation index. The simulation results show that, a SNDR higher than 30 dB can be obtained for the proposed method, which is in agreement with the theoretical analysis.

  1. Automated classification of cell morphology by coherence-controlled holographic microscopy

    NASA Astrophysics Data System (ADS)

    Strbkova, Lenka; Zicha, Daniel; Vesely, Pavel; Chmelik, Radim

    2017-08-01

    In the last few years, classification of cells by machine learning has become frequently used in biology. However, most of the approaches are based on morphometric (MO) features, which are not quantitative in terms of cell mass. This may result in poor classification accuracy. Here, we study the potential contribution of coherence-controlled holographic microscopy enabling quantitative phase imaging for the classification of cell morphologies. We compare our approach with the commonly used method based on MO features. We tested both classification approaches in an experiment with nutritionally deprived cancer tissue cells, while employing several supervised machine learning algorithms. Most of the classifiers provided higher performance when quantitative phase features were employed. Based on the results, it can be concluded that the quantitative phase features played an important role in improving the performance of the classification. The methodology could be valuable help in refining the monitoring of live cells in an automated fashion. We believe that coherence-controlled holographic microscopy, as a tool for quantitative phase imaging, offers all preconditions for the accurate automated analysis of live cell behavior while enabling noninvasive label-free imaging with sufficient contrast and high-spatiotemporal phase sensitivity.

  2. Tobacco control, global health policy and development: towards policy coherence in global governance

    PubMed Central

    Collin, Jeff

    2015-01-01

    The WHO Framework Convention on Tobacco Control (FCTC) demonstrates the international political will invested in combating the tobacco pandemic and a newfound prominence for tobacco control within the global health agenda. However, major difficulties exist in managing conflicts with foreign and trade policy priorities, and significant obstacles confront efforts to create synergies with development policy and avoid tensions with other health priorities. This paper uses the concept of policy coherence to explore congruence and inconsistencies in objectives, policy, and practice between tobacco control and trade, development and global health priorities. Following the inability of the FCTC negotiations to satisfactorily address the relationship between trade and health, several disputes highlight the challenges posed to tobacco control policies by multilateral and bilateral agreements. While the work of the World Bank has demonstrated the potential contribution of tobacco control to development, the absence of non-communicable diseases from the Millennium Development Goals has limited scope to offer developing countries support for FCTC implementation. Even within international health, tobacco control priorities may be hard to reconcile with other agendas. The paper concludes by discussing the extent to which tobacco control has been pursued via a model of governance very deliberately different from those used in other health issues, in what can be termed ‘tobacco exceptionalism’. The analysis developed here suggests that non-communicable disease (NCD) policies, global health, development and tobacco control would have much to gain from re-examining this presumption of difference. PMID:22345267

  3. Tobacco control, global health policy and development: towards policy coherence in global governance.

    PubMed

    Collin, Jeff

    2012-03-01

    The WHO Framework Convention on Tobacco Control (FCTC) demonstrates the international political will invested in combating the tobacco pandemic and a newfound prominence for tobacco control within the global health agenda. However, major difficulties exist in managing conflicts with foreign and trade policy priorities, and significant obstacles confront efforts to create synergies with development policy and avoid tensions with other health priorities. This paper uses the concept of policy coherence to explore congruence and inconsistencies in objectives, policy, and practice between tobacco control and trade, development and global health priorities. Following the inability of the FCTC negotiations to satisfactorily address the relationship between trade and health, several disputes highlight the challenges posed to tobacco control policies by multilateral and bilateral agreements. While the work of the World Bank has demonstrated the potential contribution of tobacco control to development, the absence of non-communicable diseases from the Millennium Development Goals has limited scope to offer developing countries support for FCTC implementation. Even within international health, tobacco control priorities may be hard to reconcile with other agendas. The paper concludes by discussing the extent to which tobacco control has been pursued via a model of governance very deliberately different from those used in other health issues, in what can be termed 'tobacco exceptionalism'. The analysis developed here suggests that non-communicable disease (NCD) policies, global health, development and tobacco control would have much to gain from re-examining this presumption of difference.

  4. Coherent diffraction imaging analysis of shape-controlled nanoparticles with focused hard X-ray free-electron laser pulses.

    PubMed

    Takahashi, Yukio; Suzuki, Akihiro; Zettsu, Nobuyuki; Oroguchi, Tomotaka; Takayama, Yuki; Sekiguchi, Yuki; Kobayashi, Amane; Yamamoto, Masaki; Nakasako, Masayoshi

    2013-01-01

    We report the first demonstration of the coherent diffraction imaging analysis of nanoparticles using focused hard X-ray free-electron laser pulses, allowing us to analyze the size distribution of particles as well as the electron density projection of individual particles. We measured 1000 single-shot coherent X-ray diffraction patterns of shape-controlled Ag nanocubes and Au/Ag nanoboxes and estimated the edge length from the speckle size of the coherent diffraction patterns. We then reconstructed the two-dimensional electron density projection with sub-10 nm resolution from selected coherent diffraction patterns. This method enables the simultaneous analysis of the size distribution of synthesized nanoparticles and the structures of particles at nanoscale resolution to address correlations between individual structures of components and the statistical properties in heterogeneous systems such as nanoparticles and cells.

  5. Assembly and Commissioning of a Liquid Argon Detector and Development of a Slow Control System for the COHERENT Experiment

    NASA Astrophysics Data System (ADS)

    Kaemingk, Michael; Cooper, Robert; Coherent Collaboration

    2016-09-01

    COHERENT is a collaboration whose goal is to measure coherent elastic neutrino-nucleus scattering (CEvNS). COHERENT plans to deploy a suite of detectors to measure the expected number-of-neutrons squared dependence of CEvNS at the Spallation Neutron Source at Oak Ridge National Laboratory. One of these detectors is a liquid argon detector which can measure these low energy nuclear recoil interactions. Ensuring optimal functionality requires the development of a slow control system to monitor and control various aspects, such as the temperature and pressure, of these detectors. Electronics manufactured by Beckhoff, Digilent, and Arduino among others are being used to create these slow control systems. This poster will generally discuss the assembly and commissioning of this CENNS-10 liquid argon detector at Indiana University and will feature work on the slow control systems.

  6. Temporal dynamics of primary motor cortex γ oscillation amplitude and piper corticomuscular coherence changes during motor control.

    PubMed

    Muthukumaraswamy, Suresh D

    2011-08-01

    In recent years, the use of non-invasive techniques (EEG/MEG) to measure the ~80 Hz ("gamma") oscillations generated by the primary motor cortex during motor control has been well validated. However, primary motor cortex gamma oscillations have yet to be systematically compared with lower frequency (30-50 Hz, 'piper') corticomuscular coherence in the same tasks. In this paper, primary cortex gamma oscillations and piper corticomuscular coherence are compared for three types of movements: simple abductions of the index finger, repetitive abductions of the index finger of different extents and frequencies and static abduction of the index finger at two different force levels. For simple movements, piper coherence and gamma amplitude followed very similar time courses with coherence appearing at approximately half the frequency of cortical gamma oscillations. No evidence of 2:1 phase-phase coupling was observed. A similar pattern of results was observed for repetitive movements varying in size and frequency; however, during the production of static force, the time courses became dissociated. During these movements, EMG piper amplitude was sustained for the entire contraction; gamma power showed a burst at onset but no piper corticomuscular coherence was observed. For these data, this dissociation suggests that while primary motor cortex gamma oscillations and piper corticomuscular coherence may often co-occur during the production of dynamic movements, they probably reflect different functional processes in motor control.

  7. TOPICAL REVIEW A review of the coherent optical control of the exciton and spin states of semiconductor quantum dots

    NASA Astrophysics Data System (ADS)

    Ramsay, A. J.

    2010-10-01

    The spin of a carrier trapped in a self-assembled quantum dot has the potential to be a robust optically active qubit that is compatible with existing III-V semiconductor device technology. A key requirement for building a quantum processor is the ability to dynamically prepare, control and detect single quantum states. Here, experimental progress in the coherent optical control of single semiconductor quantum dots over the past decade is reviewed, alongside an introductory discussion of the basic principles of coherent control.

  8. Coherent control of magnetization precession in electrically detected time domain ferromagnetic resonance

    SciTech Connect

    Wid, O.; Wahler, M.; Homonnay, N.; Richter, T.; Schmidt, G.

    2015-11-15

    We demonstrate coherent control of time domain ferromagnetic resonance by all electrical excitation and detection. Using two ultrashort magnetic field steps with variable time delay we control the induction decay in yttrium iron garnet (YIG). By setting suitable delay times between the two steps the precession of the magnetization can either be enhanced or completely stopped. The method allows for a determination of the precession frequency within a few precession periods and with an accuracy much higher than can be achieved using fast fourier transformation. Moreover it holds the promise to massively increase precession amplitudes in pulsed inductive microwave magnetometry (PIMM) using low amplitude finite pulse trains. Our experiments are supported by micromagnetic simulations which nicely confirm the experimental results.

  9. Prospects of coherent control in turbid media: Bounds on focusing broadband laser pulses

    SciTech Connect

    Shapiro, Evgeny A.; Drane, Thomas M.; Milner, Valery

    2011-11-15

    We study the prospects of controlling transmission of broadband and bichromatic laser pulses through turbid samples. The ability to focus transmitted broadband light is limited via both the scattering properties of the medium and the technical characteristics of the experimental setup. There are two time scales given by pulse stretching in the near- and far-field regions which define the maximum bandwidth of a pulse amenable to focusing. In the geometric-optics regime of wave propagation in the medium, a single setup can be optimal for focusing light at frequencies {omega} and n{omega} simultaneously, providing the basis for the 1+n coherent quantum control. Beyond the regime of geometric optics, we discuss a simple solution for the shaping, which provides the figure of merit for one's ability to simultaneously focus several transmission modes.

  10. Laser process monitoring and automatic control at kHz rates through inline coherent imaging

    NASA Astrophysics Data System (ADS)

    Fraser, James M.

    2012-07-01

    Laser processing can achieve high transverse precision but control of the axial penetration depth in percussion drilling and keyhole welding has proved problematic. Processing can be highly stochastic (due to plasma, gas and melt flow dynamics). Normal imaging techniques can provide only minimal depth information and may be blinded by intense backscatter, black body and plasma emission. Inline coherent imaging (ICI) provides in situ, micron-scale depth measurements of laser machining processes at >300 kHz without any requirement for sample transparency or specialized geometry. The imaging beam is delivered coaxially with the laser processing beam facilitating integration into most laser processing platforms. With the ability to image deep (multi-mm) into high aspect features at high acquisition rates, ICI is a promising tool for both process development and online control of laser manufacturing systems.

  11. Dataset on coherent control of fields and induced currents in nonlinear multiphoton processes in a nanosphere

    PubMed Central

    McArthur, Duncan; Hourahine, Ben; Papoff, Francesco

    2015-01-01

    We model a scheme for the coherent control of light waves and currents in metallic nanospheres which applies independently of the nonlinear multiphoton processes at the origin of waves and currents. Using exact mathematical formulae, we calculate numerically with a custom fortran code the effect of an external control field which enable us to change the radiation pattern and suppress radiative losses or to reduce absorption, enabling the particle to behave as a perfect scatterer or as a perfect absorber. Data are provided in tabular, comma delimited value format and illustrate narrow features in the response of the particles that result in high sensitivity to small variations in the local environment, including subwavelength spatial shifts. PMID:26601699

  12. Controlled Bioactive Molecules Delivery Strategies for Tendon and Ligament Tissue Engineering using Polymeric Nanofibers.

    PubMed

    Hiong Teh, Thomas Kok; Hong Goh, James Cho; Toh, Siew Lok

    2015-01-01

    The interest in polymeric nanofibers has escalated over the past decade given its promise as tissue engineering scaffolds that can mimic the nanoscale structure of the native extracellular matrix. With functionalization of the polymeric nanofibers using bioactive molecules, localized signaling moieties can be established for the attached cells, to stimulate desired biological effects and direct cellular or tissue response. The inherently high surface area per unit mass of polymeric nanofibers can enhance cell adhesion, bioactive molecules loading and release efficiencies, and mass transfer properties. In this review article, the application of polymeric nanofibers for controlled bioactive molecules delivery will be discussed, with a focus on tendon and ligament tissue engineering. Various polymeric materials of different mechanical and degradation properties will be presented along with the nanofiber fabrication techniques explored. The bioactive molecules of interest for tendon and ligament tissue engineering, including growth factors and small molecules, will also be reviewed and compared in terms of their nanofiber incorporation strategies and release profiles. This article will also highlight and compare various innovative strategies to control the release of bioactive molecules spatiotemporally and explore an emerging tissue engineering strategy involving controlled multiple bioactive molecules sequential release. Finally, the review article concludes with challenges and future trends in the innovation and development of bioactive molecules delivery using polymeric nanofibers for tendon and ligament tissue engineering.

  13. Nonparalytic botulinum molecules for the control of pain.

    PubMed

    Mangione, Antonina S; Obara, Ilona; Maiarú, Maria; Geranton, Sandrine M; Tassorelli, Cristina; Ferrari, Enrico; Leese, Charlotte; Davletov, Bazbek; Hunt, Stephen P

    2016-05-01

    Local injections of botulinum toxins have been reported to be useful not only for the treatment of peripheral neuropathic pain and migraine but also to cause long-lasting muscle paralysis, a potentially serious side effect. Recently, a botulinum A-based molecule ("BiTox") has been synthesized that retains neuronal silencing capacity without triggering muscle paralysis. In this study, we examined whether BiTox delivered peripherally was able to reduce or prevent the increased nociceptive sensitivity found in animal models of inflammatory, surgical, and neuropathic pain. Plasma extravasation and edema were also measured as well as keratinocyte proliferation. No motor deficits were seen and acute thermal and mechanical nociceptive thresholds were unimpaired by BiTox injections. We found reduced plasma extravasation and inflammatory edema as well as lower levels of keratinocyte proliferation in cutaneous tissue after local BiTox injection. However, we found no evidence that BiTox was transported to the dorsal root ganglia or dorsal horn and no deficits in formalin-elicited behaviors or capsaicin or formalin-induced c-Fos expression within the dorsal horn. In contrast, Bitox treatment strongly reduced A-nociceptor-mediated secondary mechanical hyperalgesia associated with either complete Freund's adjuvant (CFA)-induced joint inflammation or capsaicin injection and the hypersensitivity associated with spared nerve injury. These results imply that although local release of neuromodulators from C-fibers was inhibited by BiTox injection, C-nociceptive signaling function was not impaired. Taken together with recent clinical data the results suggest that BiTox should be considered for treatment of pain conditions in which A-nociceptors are thought to play a significant role.

  14. Nonparalytic botulinum molecules for the control of pain

    PubMed Central

    Mangione, Antonina S.; Obara, Ilona; Maiarú, Maria; Geranton, Sandrine M.; Tassorelli, Cristina; Ferrari, Enrico; Leese, Charlotte; Davletov, Bazbek; Hunt, Stephen P.

    2016-01-01

    Abstract Local injections of botulinum toxins have been reported to be useful not only for the treatment of peripheral neuropathic pain and migraine but also to cause long-lasting muscle paralysis, a potentially serious side effect. Recently, a botulinum A-based molecule (“BiTox”) has been synthesized that retains neuronal silencing capacity without triggering muscle paralysis. In this study, we examined whether BiTox delivered peripherally was able to reduce or prevent the increased nociceptive sensitivity found in animal models of inflammatory, surgical, and neuropathic pain. Plasma extravasation and edema were also measured as well as keratinocyte proliferation. No motor deficits were seen and acute thermal and mechanical nociceptive thresholds were unimpaired by BiTox injections. We found reduced plasma extravasation and inflammatory edema as well as lower levels of keratinocyte proliferation in cutaneous tissue after local BiTox injection. However, we found no evidence that BiTox was transported to the dorsal root ganglia or dorsal horn and no deficits in formalin-elicited behaviors or capsaicin or formalin-induced c-Fos expression within the dorsal horn. In contrast, Bitox treatment strongly reduced A-nociceptor-mediated secondary mechanical hyperalgesia associated with either complete Freund’s adjuvant (CFA)-induced joint inflammation or capsaicin injection and the hypersensitivity associated with spared nerve injury. These results imply that although local release of neuromodulators from C-fibers was inhibited by BiTox injection, C-nociceptive signaling function was not impaired. Taken together with recent clinical data the results suggest that BiTox should be considered for treatment of pain conditions in which A-nociceptors are thought to play a significant role. PMID:26761389

  15. Mars Organic Molecule Analyzer (MOMA) as an Example for Contamination Control for Life Detection Instrumentation

    NASA Astrophysics Data System (ADS)

    Steininger, H.; Goesmann, F.; Raulin, F.; Brinckerhoff, W. B.; Mahaffy, P. R.; Szopa, C.

    2016-10-01

    The contamination control approach for life detection instrument is presented on the example of the Mars Organic Molecule Analyzer. A combined pyrolysis gas chromatograph mass spectrometer and laser desorption mass spectrometer.

  16. Coherent control of diamond defects for quantum information science and quantum sensing

    NASA Astrophysics Data System (ADS)

    Maurer, Peter

    Quantum mechanics, arguably one of the greatest achievements of modern physics, has not only fundamentally changed our understanding of nature but is also taking an ever increasing role in engineering. Today, the control of quantum systems has already had a far-reaching impact on time and frequency metrology. By gaining further control over a large variety of different quantum systems, many potential applications are emerging. Those applications range from the development of quantum sensors and new quantum metrological approaches to the realization of quantum information processors and quantum networks. Unfortunately most quantum systems are very fragile objects that require tremendous experimental effort to avoid dephasing. Being able to control the interaction between a quantum system with its local environment embodies therefore an important aspect for application and hence is at the focus of this thesis. Nitrogen Vacancy (NV) color centers in diamond have recently attracted attention as a room temperature solid state spin system that expresses long coherence times. The electronic spin associated with NV centers can be efficiently manipulated, initialized and readout using microwave and optical techniques. Inspired by these extraordinary properties, much effort has been dedicated to use NV centers as a building block for scalable room temperature quantum information processing and quantum communication as well as a quantum sensing. In the first part of this thesis we demonstrate that by decoupling the spin from the local environment the coherence time of a NV quantum register can be extended by three order of magnitudes. Employing a novel dissipative mechanism in combination with dynamical decoupling, memory times exceeding one second are observed. The second part shows that, based on quantum control, NV centers in nano-diamonds provide a nanoscale temperature sensor with unprecedented accuracy enabling local temperature measurements in living biological cells

  17. Observation and coherent control of interface-induced electronic resonances in a field-effect transistor

    NASA Astrophysics Data System (ADS)

    Tenorio-Pearl, J. O.; Herbschleb, E. D.; Fleming, S.; Creatore, C.; Oda, S.; Milne, W. I.; Chin, A. W.

    2017-02-01

    Electronic defect states at material interfaces provide highly deleterious sources of noise in solid-state nanostructures, and even a single trapped charge can qualitatively alter the properties of short one-dimensional nanowire field-effect transistors (FET) and quantum bit (qubit) devices. Understanding the dynamics of trapped charge is thus essential for future nanotechnologies, but their direct detection and manipulation is rather challenging. Here, a transistor-based set-up is used to create and probe individual electronic defect states that can be coherently driven with microwave (MW) pulses. Strikingly, we resolve a large number of very high quality (Q ~ 1 × 105) resonances in the transistor current as a function of MW frequency and demonstrate both long decoherence times (~1 μs--40 μs) and coherent control of the defect-induced dynamics. Efficiently characterizing over 800 individually addressable resonances across two separate defect-hosting materials, we propose that their properties are consistent with weakly driven two-level systems.

  18. Control of coherent information via on-chip photonic–phononic emitter–receivers

    DOE PAGES

    Shin, Heedeuk; Cox, Jonathan A.; Jarecki, Robert; ...

    2015-03-05

    We report that rapid progress in integrated photonics has fostered numerous chip-scale sensing, computing and signal processing technologies. However, many crucial filtering and signal delay operations are difficult to perform with all-optical devices. Unlike photons propagating at luminal speeds, GHz-acoustic phonons moving at slower velocities allow information to be stored, filtered and delayed over comparatively smaller length-scales with remarkable fidelity. Hence, controllable and efficient coupling between coherent photons and phonons enables new signal processing technologies that greatly enhance the performance and potential impact of integrated photonics. Here we demonstrate a mechanism for coherent information processing based on travelling-wave photon–phonon transduction,more » which achieves a phonon emit-and-receive process between distinct nanophotonic waveguides. Using this device, physics—which supports GHz frequencies—we create wavelength-insensitive radiofrequency photonic filters with frequency selectivity, narrow-linewidth and high power-handling in silicon. More generally, this emit-receive concept is the impetus for enabling new signal processing schemes.« less

  19. Coherence-controlled holographic microscopy for live-cell quantitative phase imaging

    NASA Astrophysics Data System (ADS)

    Slabý, TomáÅ.¡; Křížová, Aneta; Lošt'ák, Martin; Čolláková, Jana; Jůzová, Veronika; Veselý, Pavel; Chmelík, Radim

    2015-03-01

    In this paper we present coherence-controlled holographic microscopy (CCHM) and various examples of observations of living cells including combination of CCHM with fluorescence microscopy. CCHM is a novel technique of quantitative phase imaging (QPI). It is based on grating off-axis interferometer, which is fully adapted for the use of incoherent illumination. This enables high-quality QPI free from speckles and parasitic interferences and lateral resolution of classical widefield microscopes. Label-free nature of QPI makes CCHM a useful tool for long-term observations of living cells. Moreover, coherence-gating effect induced by the use of incoherent illumination enables QPI of cells even in scattering media. Combination of CCHM with common imaging techniques brings the possibility to exploit advantages of QPI while simultaneously identifying the observed structures or processes by well-established imaging methods. We used CCHM for investigation of general parameters of cell life cycles and for research of cells reactions to different treatment. Cells were also visualized in 3D collagen gel with the use of CCHM. It was found that both the cell activity and movement of the collagen fibers can be registered. The method of CCHM in combination with fluorescence microscopy was used in order to obtain complementary information about cell morphology and identify typical morphological changes associated with different types of cell death. This combination of CCHM with common imaging technique has a potential to provide new knowledge about various processes and simultaneously their confirmation by comparison with known imaging method.

  20. Control of coherent information via on-chip photonic-phononic emitter-receivers.

    PubMed

    Shin, Heedeuk; Cox, Jonathan A; Jarecki, Robert; Starbuck, Andrew; Wang, Zheng; Rakich, Peter T

    2015-03-05

    Rapid progress in integrated photonics has fostered numerous chip-scale sensing, computing and signal processing technologies. However, many crucial filtering and signal delay operations are difficult to perform with all-optical devices. Unlike photons propagating at luminal speeds, GHz-acoustic phonons moving at slower velocities allow information to be stored, filtered and delayed over comparatively smaller length-scales with remarkable fidelity. Hence, controllable and efficient coupling between coherent photons and phonons enables new signal processing technologies that greatly enhance the performance and potential impact of integrated photonics. Here we demonstrate a mechanism for coherent information processing based on travelling-wave photon-phonon transduction, which achieves a phonon emit-and-receive process between distinct nanophotonic waveguides. Using this device, physics--which supports GHz frequencies--we create wavelength-insensitive radiofrequency photonic filters with frequency selectivity, narrow-linewidth and high power-handling in silicon. More generally, this emit-receive concept is the impetus for enabling new signal processing schemes.

  1. Control of coherent information via on-chip photonic–phononic emitter–receivers

    SciTech Connect

    Shin, Heedeuk; Cox, Jonathan A.; Jarecki, Robert; Starbuck, Andrew; Wang, Zheng; Rakich, Peter T.

    2015-03-05

    We report that rapid progress in integrated photonics has fostered numerous chip-scale sensing, computing and signal processing technologies. However, many crucial filtering and signal delay operations are difficult to perform with all-optical devices. Unlike photons propagating at luminal speeds, GHz-acoustic phonons moving at slower velocities allow information to be stored, filtered and delayed over comparatively smaller length-scales with remarkable fidelity. Hence, controllable and efficient coupling between coherent photons and phonons enables new signal processing technologies that greatly enhance the performance and potential impact of integrated photonics. Here we demonstrate a mechanism for coherent information processing based on travelling-wave photon–phonon transduction, which achieves a phonon emit-and-receive process between distinct nanophotonic waveguides. Using this device, physics—which supports GHz frequencies—we create wavelength-insensitive radiofrequency photonic filters with frequency selectivity, narrow-linewidth and high power-handling in silicon. More generally, this emit-receive concept is the impetus for enabling new signal processing schemes.

  2. Phase control in an open Λ-type system with spontaneously generated coherence

    NASA Astrophysics Data System (ADS)

    Cui, Ni; Fan, Xi-Jun; Li, Ai-Yun; Liu, Cheng-Pu; Gong, Shang-Qing; Xu, Zhi-Zhan

    2007-03-01

    This paper investigates the control role of the relative phase between the probe and driving fields on the gain, dispersion and populations in an open Λ system with spontaneously generated coherence (SGC). It shows that by adjusting the value of the relative phase, a change from lasing with inversion to lasing without inversion can be realized; the values and frequency spectrum regions of the inversionless gain and dispersion can be obviously varied; high refractive index with zero absorption and electromagnetically induced transparency can be achieved. It is also found that when the driving field is resonant, the shapes of the dispersion and the gain curves versus the probe detuning are very similar if the relative phase of the dispersion lags π/2 than that of the gain, however for the off-resonant driving field the similarity will disappear; the gain, dispersion and populations are periodical functions of the relative phase, the modulation period is always 2π the contribution of SGC to the inversionless gain and dispersion is much larger than that of the dynamically induced coherence.

  3. Control of coherent information via on-chip photonic–phononic emitter–receivers

    PubMed Central

    Shin, Heedeuk; Cox, Jonathan A.; Jarecki, Robert; Starbuck, Andrew; Wang, Zheng; Rakich, Peter T.

    2015-01-01

    Rapid progress in integrated photonics has fostered numerous chip-scale sensing, computing and signal processing technologies. However, many crucial filtering and signal delay operations are difficult to perform with all-optical devices. Unlike photons propagating at luminal speeds, GHz-acoustic phonons moving at slower velocities allow information to be stored, filtered and delayed over comparatively smaller length-scales with remarkable fidelity. Hence, controllable and efficient coupling between coherent photons and phonons enables new signal processing technologies that greatly enhance the performance and potential impact of integrated photonics. Here we demonstrate a mechanism for coherent information processing based on travelling-wave photon–phonon transduction, which achieves a phonon emit-and-receive process between distinct nanophotonic waveguides. Using this device, physics—which supports GHz frequencies—we create wavelength-insensitive radiofrequency photonic filters with frequency selectivity, narrow-linewidth and high power-handling in silicon. More generally, this emit-receive concept is the impetus for enabling new signal processing schemes. PMID:25740405

  4. Coherent control of wavepacket launch and evolution in molecular cations in strong-field regime

    NASA Astrophysics Data System (ADS)

    Romanov(1, 3), Dmitri; Moore Tibbetts(2, 3), Katharine; Tarazkar(2, 3), Maryam; Bohinsky(2, 3), Timothy; Matsika(2, 3), Spiridoula; Levis(2, 3), Robert

    2016-05-01

    The time-resolved dissociative ionization dynamics for a family of acetophenone radical cations has been studied in pump-probe experiments. Modifications of the relative fragment yield have been measured as a function of the pump laser wavelength from 790 nm to 1500 nm. In the case of tunnel ionization (1150 - 1500 nm pump), the time-resolved transients of the parent and fragment ions probed with a weak 790 nm pulse reveal an order-of-magnitude enhancement of the peak-to-peak amplitude oscillations, ~ 100 fs longer coherence time, and an order-of-magnitude increase in the ratio of parent to fragment ions, as compared to the case of multiphoton ionization (790 nm pump). The results are quantitatively explained with a model of wavepacket evolution on the ground (D0) and excited (D1 and D2) ionic potential energy surfaces, with the probe-induced and conical-intersection-related transitions between the surfaces. The theory predicts the periods of fragment-ratio oscillations, thus confirming the ability to prepare and manipulate multiple wavepackets in the vicinity of a conical intersection for polyatomic molecules on the time scale of picoseconds.

  5. Precision Control of Ultracold Molecules in Optical Lattices

    DTIC Science & Technology

    2011-07-20

    control and precision. For example, a Stark-cancellation, or magic frequency , technique has enabled state-of-the-art neutral atom clocks. This approach...NUMBER OF PAGES 19a. NAME OF RESPONSIBLE PERSON a. REPORT b. ABSTRACT c. THIS PAGE 17. LIMITATION OF ABSTRACT Standard Form 298...precision frequency measurements with the goal to find evidence for a possible time variation of the electron-proton mass ratio. The proposal also included

  6. Coherent control of optical bistability and multistability in a triple semiconductor quantum well nanostructure

    NASA Astrophysics Data System (ADS)

    Raheli, A.; Afshari, H.; Hamedi, H. R.

    2015-10-01

    This paper deals with optical bistability (OB) and optical multistability (OM) behaviors for a triple semiconductor quantum well (SQW) structure driven coherently with two control fields, confined in a unidirectional ring cavity. The effect of different system parameters on OB and OM is explored. It is found that the threshold of onset of the OB can be controlled by manipulating the Rabi frequency of control fields. In this case, OB can be converted to OM. Then we investigate the effect of probe and control field detunings on OB behaviors. We found that the frequency detuning of probe field affects only the upper-lower branches of the OB curves but has no specific impact on OB threshold. By manipulating the first control field detuning, neither the OB threshold intensity nor upper-lower branches change. Finally, it is found that increasing the second control field detuning can reduce merely the OB threshold intensity, while no change happens in upper-lower OB branches. The results may be applicable in real experiments for realizing an all-optical switching or coding element in a solid-state platform.

  7. Phase control of Goos-Hänchen shift via biexciton coherence in a multiple quantum well

    NASA Astrophysics Data System (ADS)

    Asadpour, Seyyed Hossein; Nasehi, Rajab; Soleimani, H. Rahimpour; Mahmoudi, M.

    2015-09-01

    The behavior of the Goos-Hänchen (GH) shifts of the reflected and transmitted probe and signal pulses through a cavity containing four-level GaAs/AlGaAs multiple quantum wells with 15 periods of 17.5 nm GaAs wells and 15-nm Al0.3Ga0.7As barriers is theoretically discussed. The biexciton coherence set up by two coupling fields can induce the destructive interference to control the absorption and gain properties of probe field under appropriate conditions. It is realized that for the specific values of the intensities and the relative phase of applied fields, the simultaneous negative or positive GH shift in the transmitted and reflected light beam can be obtained via amplification in a probe light. It is found that by adjusting the controllable parameters, the GH shifts can be switched between the large positive and negative values in the medium. Moreover, the effect of exciton spin relaxation on the GH shift has also been discussed. We find that the exciton spin relaxation can manipulate the behavior of GH shift in the reflected and transmitted probe beam through the cavity. We show that by controlling the incident angles of probe beam and under certain conditions, the GH shifts in the reflected and transmitted probe beams can become either negative or positive corresponding to the superluminal or subluminal light propagation. Our proposed model may supply a new prospect in technological applications for the light amplification in optical sensors working on quantum coherence impacts in solid-state systems.

  8. The artificial control of enhanced optical processes in fluorescent molecules on high-emittance metasurfaces

    NASA Astrophysics Data System (ADS)

    Iwanaga, Masanobu; Choi, Bongseok; Miyazaki, Hideki T.; Sugimoto, Yoshimasa

    2016-05-01

    Plasmon-enhanced optical processes in molecules have been extensively but individually explored for Raman scattering, fluorescence, and infrared light absorption. In contrast to recent progress in the interfacial control of hot electrons in plasmon-semiconductor hybrid systems, plasmon-molecule hybrid systems have remained to be a conventional scheme, mainly assuming electric-field enhancement. This was because it was difficult to control the plasmon-molecule interface in a well-controlled manner. We here experimentally substantiate an obvious change in artificially enhanced optical processes of fluorescence/Raman scattering in fluorescent molecules on high-emittance plasmo-photonic metasurfaces with/without a self-assembled monolayer of sub-nm thickness. These results indicate that the enhanced optical processes were successfully selected under artificial configurations without any additional chemical treatment that modifies the molecules themselves. Although Raman-scattering efficiency is generally weak in high-fluorescence-yield molecules, it was found that Raman scattering becomes prominent around the molecular fingerprint range on the metasurfaces, being enhanced by more than 2000 fold at the maximum for reference signals. In addition, the highly and uniformly enhancing metasurfaces are able to serve as two-way functional, reproducible, and wavelength-tunable platforms to detect molecules at very low densities, being distinct from other platforms reported so far. The change in the enhanced signals suggests that energy diagrams in fluorescent molecules are changed in the configuration that includes the metal-molecule interface, meaning that plasmon-molecule hybrid systems are rich in the phenomena beyond the conventional scheme.Plasmon-enhanced optical processes in molecules have been extensively but individually explored for Raman scattering, fluorescence, and infrared light absorption. In contrast to recent progress in the interfacial control of hot electrons

  9. Coherence-controlled holographic microscopy principle embodiment into Q-PHASE microscope: story of a successful technology transfer

    NASA Astrophysics Data System (ADS)

    Lostak, M.; Chmelik, R.

    2016-03-01

    Curiously, the coherence-controlled holographic microscopy (CCHM) was brought into the world owing to the endeavor of Chmelik's team at Brno University of Technology (BUT) to avoid scanning in confocal microscopy. As coherence gating seemed to be the way, the Leith & Upatnieks proposal of incoherent holography had been considered attractive. Their method made interference system free from strict dependence on both spatial and temporal coherence. Off axis holographic system proposed on such basis has been proved capable of coherence based depth discrimination in single wide-field shot in reflected-light arrangement. Consequently, extremely low-coherence holographic imaging had been found highly contributive also to the image quality depriving it from coherence artefacts and improving its transversal resolution. This is why CCHM promised high precision of quantitative phase imaging (QPI) in transmitted light set up that was realized for cell biology. However the cost of necessarily complicated optical design and need of very precise mechanics forced the team of prof Chmelik at BUT to search for a company capable of mastering the instrument. It was TESCAN ORSAY the highly successful scanning electron microscopes producer that finally took charge of the commercial design. Long-term collaboration of the company with BUT made possible both the CCHM technology successful transfer up to Q-PHASE microscope production as well as the company Light microscopy division reinforcement. This contribution merges views of CCHM technology author and the TESCAN development team.

  10. Small Molecule Control of Virulence Gene Expression in Francisella tularensis

    PubMed Central

    Charity, James C.; Blalock, LeeAnn T.; Costante-Hamm, Michelle M.; Kasper, Dennis L.; Dove, Simon L.

    2009-01-01

    In Francisella tularensis, the SspA protein family members MglA and SspA form a complex that associates with RNA polymerase (RNAP) to positively control the expression of virulence genes critical for the intramacrophage growth and survival of the organism. Although the association of the MglA-SspA complex with RNAP is evidently central to its role in controlling gene expression, the molecular details of how MglA and SspA exert their effects are not known. Here we show that in the live vaccine strain of F. tularensis (LVS), the MglA-SspA complex works in concert with a putative DNA-binding protein we have called PigR, together with the alarmone guanosine tetraphosphate (ppGpp), to regulate the expression of target genes. In particular, we present evidence that MglA, SspA, PigR and ppGpp regulate expression of the same set of genes, and show that mglA, sspA, pigR and ppGpp null mutants exhibit similar intramacrophage growth defects and are strongly attenuated for virulence in mice. We show further that PigR interacts directly with the MglA-SspA complex, suggesting that the central role of the MglA and SspA proteins in the control of virulence gene expression is to serve as a target for a transcription activator. Finally, we present evidence that ppGpp exerts its effects by promoting the interaction between PigR and the RNAP-associated MglA-SspA complex. Through its responsiveness to ppGpp, the contact between PigR and the MglA-SspA complex allows the integration of nutritional cues into the regulatory network governing virulence gene expression. PMID:19876386

  11. A theory of diffusion controlled reactions in polyatomic molecule system

    NASA Astrophysics Data System (ADS)

    Kasahara, Kento; Sato, Hirofumi

    2016-11-01

    The conventional Smoluchowski equation has been extensively utilized to investigate diffusion controlled reactions. However, application of the equation is limited to spherical-particle system. In the present study, a new Smoluchowski equation for polyatomic molecular system is derived based on Zwanzig-Mori projection operator method and reference interaction site model (RISM) theory. The theory is applied to monoatomic molecular liquid, and the obtained time-dependent rate constant is virtually identical with that from conventional Smoluchowski equation. For diatomic molecular liquid, time-dependent distribution function and rate constant are obtained, showing a good agreement with those from molecular dynamics simulation.

  12. 12-Channel Peltier array temperature control unit for single molecule enzymology studies using capillary electrophoresis.

    PubMed

    Craig, Douglas B; Reinfelds, Gundars; Henderson, Anna

    2014-08-01

    Capillary electrophoresis has been used to demonstrate that individual molecules of a given enzyme support different catalytic rates. In order to determine how rate varies with temperature, and determine activation energies for individual β-galactosidase molecules, a 12-channel Peltier array temperature control device was constructed where the temperature of each cell was separately controlled. This array was used to control the temperature of the central 30 cm of a 50 cm long capillary, producing a temperature gradient along its length. Continuous flow single β-galactosidase molecule assays were performed allowing measurement of the catalytic rates at different temperatures. Arrhenius plots were produced and the distribution of activation energies for individual β-galactosidase molecules was found to be 56 ± 10 kJ/mol with a range of 34-72 kJ/mol.

  13. Pulse-shaping algorithm of a coherent matter-wave-controlling reaction dynamics

    SciTech Connect

    Joergensen, Solvejg; Kosloff, Ronnie

    2004-07-01

    A pulse-shaping algorithm for a matter wave with the purpose of controlling a binary reaction has been designed. The scheme is illustrated for an Eley-Rideal reaction where an impinging matter-wave atom recombines with an adsorbed atom on a metal surface. The wave function of the impinging atom is shaped such that the desorbing molecule leaves the surface in a specific vibrational state.

  14. Controlling the development of coherent structures in high speed jets and the resultant near field

    NASA Astrophysics Data System (ADS)

    Speth, Rachelle

    This work uses Large-Eddy Simulations to examine the effect of actuator parameters and jet exit properties on the evolution of coherent structures and their impact on the near-acoustic field without and with control. For the controlled cases, Localized Arc Filament Plasma Actuators (LAFPAs) are considered, and modeled with a simple heating approach that successfully reproduces the main observations and trends of experiments. A parametric study is first conducted, using the flapping mode (m = +/-1), to investigate the sensitivity of the results to various actuator parameters including: actuator model temperature, actuator duty cycle, and excitation frequency. It is shown by considering a Mach 1.3 jet at Reynolds number of 1 x 106 that the response of the jet is relatively insensitive to actuator model temperature within the limits of the experimentally measured temperature values. Furthermore, duty cycles in the range of 20%--90% were observed to be effective in reproducing the characteristic coherent structures of the flapping mode. Next, jet flow parameters were explored to determine the control authority under different operating conditions. To begin, the effect of the laminar nozzle exit boundary layer thickness was examined by varying its value from essentially uniform flow to 25% of the diameter. In the absence of control, the distance between the nozzle lip and the initial appearance of breakdown is proportional to the boundary-layer thickness, which is consistent with theory and previous results obtained by other researchers at Mach 0.9. The second flow parameter studied was the effect of Reynolds number on a Mach 1.3 jet controlled by the flapping mode at an excitation Strouhal number of 0.3. The higher Reynolds number (Re=1,100,000) jet exhibited reduced control authority compared to the Re=100,000 jet. Like the effect of increasing the nozzle exit boundary layer thickness, increasing the Reynolds number cause a reduction in spreading on the flapping plane

  15. Cascaded multi-dithering technique using PZT modulators for high control bandwidth in coherent laser beam combining

    NASA Astrophysics Data System (ADS)

    Ahn, Hee Kyung; Kong, Hong Jin

    2017-09-01

    A cascaded multi-dithering (CMD) technique using piezoelectric ceramic transducer (PZT) tubes as phase modulators is proposed as a tool for obtaining high control bandwidth in coherent laser beam combination. To prove its validity, eight coherent fiber beam elements were combined using the CMD technique with PZT tubes. As a result, residual phase error was recorded to be λ/54 at 100 Hz control bandwidth, which is comparable to that of a four laser beam combination in the previous experiment. To our knowledge, this is the first case to date of combining eight laser beam elements using PZT tubes as phase modulators and achieving such good results.

  16. Effect of polarization controlling on coherent beam combining of two-fiber laser arrays of interferometric configuration.

    PubMed

    Cao, Jianqiu; Lu, Qisheng; Chen, Sheng-Ping; Hou, Jing; Xu, Xiaojun

    2009-01-15

    The effect of polarization controlling on coherent beam combining of two-fiber laser arrays of interferometric configuration is researched. Three kinds of arrays, built on the basis of Michelson and Mach-Zehnder interferometers, are investigated experimentally. It is found that polarization controlling is not necessary for coherent beam combining of the Michelson interferometric array but necessary for that of Mach-Zehnder interferometric arrays. These results reveal the important role of polarization in the self-organization process of interferometric laser arrays.

  17. Generation of large coherent states by bang–bang control of a trapped-ion oscillator

    PubMed Central

    Alonso, J.; Leupold, F. M.; Solèr, Z. U.; Fadel, M.; Marinelli, M.; Keitch, B. C.; Negnevitsky, V.; Home, J. P.

    2016-01-01

    Fast control of quantum systems is essential to make use of quantum properties before they degrade by decoherence. This is important for quantum-enhanced information processing, as well as for pushing quantum systems towards the boundary between quantum and classical physics. ‘Bang–bang' control attains the ultimate speed limit by making large changes to control fields much faster than the system can respond, but is often challenging to implement experimentally. Here we demonstrate bang–bang control of a trapped-ion oscillator using nanosecond switching of the trapping potentials. We perform controlled displacements with which we realize coherent states with up to 10,000 quanta of energy. We use these displaced states to verify the form of the ion-light interaction at high excitations far outside the usual regime of operation. These methods provide new possibilities for quantum-state manipulation and generation, alongside the potential for a significant increase in operational clock speed for trapped-ion quantum information processing. PMID:27046513

  18. Formation and control of Turing patterns in a coherent quantum fluid

    NASA Astrophysics Data System (ADS)

    Ardizzone, Vincenzo; Lewandowski, Przemyslaw; Luk, M. H.; Tse, Y. C.; Kwong, N. H.; Lücke, Andreas; Abbarchi, Marco; Baudin, Emmanuel; Galopin, Elisabeth; Bloch, Jacqueline; Lemaitre, Aristide; Leung, P. T.; Roussignol, Philippe; Binder, Rolf; Tignon, Jerome; Schumacher, Stefan

    2013-10-01

    Nonequilibrium patterns in open systems are ubiquitous in nature, with examples as diverse as desert sand dunes, animal coat patterns such as zebra stripes, or geographic patterns in parasitic insect populations. A theoretical foundation that explains the basic features of a large class of patterns was given by Turing in the context of chemical reactions and the biological process of morphogenesis. Analogs of Turing patterns have also been studied in optical systems where diffusion of matter is replaced by diffraction of light. The unique features of polaritons in semiconductor microcavities allow us to go one step further and to study Turing patterns in an interacting coherent quantum fluid. We demonstrate formation and control of these patterns. We also demonstrate the promise of these quantum Turing patterns for applications, such as low-intensity ultra-fast all-optical switches.

  19. Controllable preparation of two-mode entangled coherent states in circuit QED

    NASA Astrophysics Data System (ADS)

    Ji, Ying-Hua; Liu, Yong-Mei

    2014-11-01

    Although the multi-level structure of superconducting qubits may result in calculation errors, it can be rationally used to effectively improve the speed of gate operations. Utilizing a current-biased Josephson junction (λ-type rf-SQUID) as a tunable coupler for superconducting transmission line resonators (TLRs), under the large detuning condition, we demonstrate the controllable generation of entangled coherent states in circuit quantum electrodynamics (circuit QED). The coupling between the TLRs and the qubit can be effectively regulated by an external bias current or coupling capacitor. Further investigations indicate that the maximum entangled state can be obtained through measuring the excited state of the superconducting qubits. Then, the influence of the TLR decay on the prepared entangled states is analyzed.

  20. Formation and control of Turing patterns in a coherent quantum fluid

    PubMed Central

    Ardizzone, Vincenzo; Lewandowski, Przemyslaw; Luk, M. H.; Tse, Y. C.; Kwong, N. H.; Lücke, Andreas; Abbarchi, Marco; Baudin, Emmanuel; Galopin, Elisabeth; Bloch, Jacqueline; Lemaitre, Aristide; Leung, P. T.; Roussignol, Philippe; Binder, Rolf; Tignon, Jerome; Schumacher, Stefan

    2013-01-01

    Nonequilibrium patterns in open systems are ubiquitous in nature, with examples as diverse as desert sand dunes, animal coat patterns such as zebra stripes, or geographic patterns in parasitic insect populations. A theoretical foundation that explains the basic features of a large class of patterns was given by Turing in the context of chemical reactions and the biological process of morphogenesis. Analogs of Turing patterns have also been studied in optical systems where diffusion of matter is replaced by diffraction of light. The unique features of polaritons in semiconductor microcavities allow us to go one step further and to study Turing patterns in an interacting coherent quantum fluid. We demonstrate formation and control of these patterns. We also demonstrate the promise of these quantum Turing patterns for applications, such as low-intensity ultra-fast all-optical switches. PMID:24145394

  1. Cavity-Assisted Measurement and Coherent Control of Collective Atomic Spin Oscillators

    NASA Astrophysics Data System (ADS)

    Kohler, Jonathan; Spethmann, Nicolas; Schreppler, Sydney; Stamper-Kurn, Dan M.

    2017-02-01

    We demonstrate continuous measurement and coherent control of the collective spin of an atomic ensemble undergoing Larmor precession in a high-finesse optical cavity. The coupling of the precessing spin to the cavity field yields phenomena similar to those observed in cavity optomechanics, including cavity amplification, damping, and optical spring shifts. These effects arise from autonomous optical feedback onto the atomic spin dynamics, conditioned by the cavity spectrum. We use this feedback to stabilize the spin in either its high- or low-energy state, where, in equilibrium with measurement backaction heating, it achieves a steady-state temperature, indicated by an asymmetry between the Stokes and the anti-Stokes scattering rates. For sufficiently large Larmor frequency, such feedback stabilizes the spin ensemble in a nearly pure quantum state, in spite of continuous measurement by the cavity field.

  2. Coherent phase-matched VUV generation by field-controlled bound states

    NASA Astrophysics Data System (ADS)

    Chini, Michael; Wang, Xiaowei; Cheng, Yan; Wang, He; Wu, Yi; Cunningham, Eric; Li, Peng-Cheng; Heslar, John; Telnov, Dmitry A.; Chu, Shih-I.; Chang, Zenghu

    2014-06-01

    The generation of high-order harmonics and attosecond pulses at ultrahigh repetition rates (>1 MHz) promises to revolutionize ultrafast spectroscopy. Such vacuum ultraviolet (VUV) and soft X-ray sources could potentially be driven directly by plasmonic enhancement of laser pulses from a femtosecond oscillator, but recent experiments suggest that the VUV signal is actually dominated by incoherent atomic line emission. Here, we demonstrate a new regime of phase-matched below-threshold harmonic generation, for which the generation and phase matching is enabled only near resonance structures of the atomic target. The coherent VUV line emission exhibits low divergence and quadratic growth with increasing target density up to nearly 1,000 torr mm and can be controlled by the sub-cycle field of a few-cycle driving laser with an intensity of only ~1 × 1013 W cm-2, which is achievable directly from few-cycle femtosecond oscillators with nanojoule energy.

  3. Arbitrary control of coherent dynamics for distant qubits in a quantum network

    SciTech Connect

    Zheng Shibiao; Yang Chuiping; Nori, Franco

    2010-10-15

    We show that the coherent coupling of atomic qubits at distant nodes of a quantum network, composed of several cavities linked by optical fibers, can be arbitrarily controlled via the selective pairing of Raman transitions. The adiabatic elimination of the atomic excited states and photonic states leads to selective qubit-qubit interactions, which would have important applications in quantum-information processing. Quantum gates between any pair of distant qubits and parallel two-qubit operations on selected qubit pairs can be implemented through suitable choices of the parameters of the external fields. Selective pairing of Raman transitions also allows the generation of spin chains and cluster states without the requirement that the cavity-fiber coupling be smaller than the detunings of the Raman transitions.

  4. A stable pattern of EEG spectral coherence distinguishes children with autism from neuro-typical controls - a large case control study

    PubMed Central

    2012-01-01

    Background The autism rate has recently increased to 1 in 100 children. Genetic studies demonstrate poorly understood complexity. Environmental factors apparently also play a role. Magnetic resonance imaging (MRI) studies demonstrate increased brain sizes and altered connectivity. Electroencephalogram (EEG) coherence studies confirm connectivity changes. However, genetic-, MRI- and/or EEG-based diagnostic tests are not yet available. The varied study results likely reflect methodological and population differences, small samples and, for EEG, lack of attention to group-specific artifact. Methods Of the 1,304 subjects who participated in this study, with ages ranging from 1 to 18 years old and assessed with comparable EEG studies, 463 children were diagnosed with autism spectrum disorder (ASD); 571 children were neuro-typical controls (C). After artifact management, principal components analysis (PCA) identified EEG spectral coherence factors with corresponding loading patterns. The 2- to 12-year-old subsample consisted of 430 ASD- and 554 C-group subjects (n = 984). Discriminant function analysis (DFA) determined the spectral coherence factors' discrimination success for the two groups. Loading patterns on the DFA-selected coherence factors described ASD-specific coherence differences when compared to controls. Results Total sample PCA of coherence data identified 40 factors which explained 50.8% of the total population variance. For the 2- to 12-year-olds, the 40 factors showed highly significant group differences (P < 0.0001). Ten randomly generated split half replications demonstrated high-average classification success (C, 88.5%; ASD, 86.0%). Still higher success was obtained in the more restricted age sub-samples using the jackknifing technique: 2- to 4-year-olds (C, 90.6%; ASD, 98.1%); 4- to 6-year-olds (C, 90.9%; ASD 99.1%); and 6- to 12-year-olds (C, 98.7%; ASD, 93.9%). Coherence loadings demonstrated reduced short-distance and reduced, as well as increased

  5. On-chip generation of high-dimensional entangled quantum states and their coherent control

    NASA Astrophysics Data System (ADS)

    Kues, Michael; Reimer, Christian; Roztocki, Piotr; Cortés, Luis Romero; Sciara, Stefania; Wetzel, Benjamin; Zhang, Yanbing; Cino, Alfonso; Chu, Sai T.; Little, Brent E.; Moss, David J.; Caspani, Lucia; Azaña, José; Morandotti, Roberto

    2017-06-01

    Optical quantum states based on entangled photons are essential for solving questions in fundamental physics and are at the heart of quantum information science. Specifically, the realization of high-dimensional states (D-level quantum systems, that is, qudits, with D > 2) and their control are necessary for fundamental investigations of quantum mechanics, for increasing the sensitivity of quantum imaging schemes, for improving the robustness and key rate of quantum communication protocols, for enabling a richer variety of quantum simulations, and for achieving more efficient and error-tolerant quantum computation. Integrated photonics has recently become a leading platform for the compact, cost-efficient, and stable generation and processing of non-classical optical states. However, so far, integrated entangled quantum sources have been limited to qubits (D = 2). Here we demonstrate on-chip generation of entangled qudit states, where the photons are created in a coherent superposition of multiple high-purity frequency modes. In particular, we confirm the realization of a quantum system with at least one hundred dimensions, formed by two entangled qudits with D = 10. Furthermore, using state-of-the-art, yet off-the-shelf telecommunications components, we introduce a coherent manipulation platform with which to control frequency-entangled states, capable of performing deterministic high-dimensional gate operations. We validate this platform by measuring Bell inequality violations and performing quantum state tomography. Our work enables the generation and processing of high-dimensional quantum states in a single spatial mode.

  6. On-chip generation of high-dimensional entangled quantum states and their coherent control.

    PubMed

    Kues, Michael; Reimer, Christian; Roztocki, Piotr; Cortés, Luis Romero; Sciara, Stefania; Wetzel, Benjamin; Zhang, Yanbing; Cino, Alfonso; Chu, Sai T; Little, Brent E; Moss, David J; Caspani, Lucia; Azaña, José; Morandotti, Roberto

    2017-06-28

    Optical quantum states based on entangled photons are essential for solving questions in fundamental physics and are at the heart of quantum information science. Specifically, the realization of high-dimensional states (D-level quantum systems, that is, qudits, with D > 2) and their control are necessary for fundamental investigations of quantum mechanics, for increasing the sensitivity of quantum imaging schemes, for improving the robustness and key rate of quantum communication protocols, for enabling a richer variety of quantum simulations, and for achieving more efficient and error-tolerant quantum computation. Integrated photonics has recently become a leading platform for the compact, cost-efficient, and stable generation and processing of non-classical optical states. However, so far, integrated entangled quantum sources have been limited to qubits (D = 2). Here we demonstrate on-chip generation of entangled qudit states, where the photons are created in a coherent superposition of multiple high-purity frequency modes. In particular, we confirm the realization of a quantum system with at least one hundred dimensions, formed by two entangled qudits with D = 10. Furthermore, using state-of-the-art, yet off-the-shelf telecommunications components, we introduce a coherent manipulation platform with which to control frequency-entangled states, capable of performing deterministic high-dimensional gate operations. We validate this platform by measuring Bell inequality violations and performing quantum state tomography. Our work enables the generation and processing of high-dimensional quantum states in a single spatial mode.

  7. Vibrational control of electron-transfer reactions: a feasibility study for the fast coherent transfer regime.

    PubMed

    Antoniou, P; Ma, Z; Zhang, P; Beratan, D N; Skourtis, S S

    2015-12-14

    Molecular vibrations and electron-vibrational interactions are central to the control of biomolecular electron and energy-transfer rates. The vibrational control of molecular electron-transfer reactions by infrared pulses may enable the precise probing of electronic-vibrational interactions and of their roles in determining electron-transfer mechanisms. This type of electron-transfer rate control is advantageous because it does not alter the electronic state of the molecular electron-transfer system or irreversibly change its molecular structure. For bridge-mediated electron-transfer reactions, infrared (vibrational) excitation of the bridge linking the electron donor to the electron acceptor was suggested as being capable of influencing the electron-transfer rate by modulating the bridge-mediated donor-to-acceptor electronic coupling. This kind of electron-transfer experiment has been realized, demonstrating that bridge-mediated electron-transfer rates can be changed by exciting vibrational modes of the bridge. Here, we use simple models and ab initio computations to explore the physical constraints on one's ability to vibrationally perturb electron-transfer rates using infrared excitation. These constraints stem from the nature of molecular vibrational spectra, the strengths of the electron-vibrational coupling, and the interaction between molecular vibrations and infrared radiation. With these constraints in mind, we suggest parameter regimes and molecular architectures that may enhance the vibrational control of electron transfer for fast coherent electron-transfer reactions.

  8. Nanoscale Molecules Under Thermodynamic Control:" Digestive Ripening" or " Nanomachining"

    SciTech Connect

    Klabunde, Kenneth J.

    2015-06-04

    Overall Research Goals and Specific Objectives: Nanoscale materials are becoming ubiquitous in science and engineering, and are found widely in nature. However, their formation processes and uniquely high chemical reactivities are not understood well, indeed are often mysterious. Over recent years, a number of research teams have described nanoparticle synthesis, and aging, thermal treatment, or etching times have been mentioned. We have used the terms “digestive ripening” and “nanomachining” and have suggested that thermodynamics plays an important part in the size adjustment to monodisperse arrays being formed. Since there is scant theoretical understanding of digestive ripening, the overall goal in our research is to learn what experimental parameters (ligand used, temperature, solvent, time) are most important, how to control nanoparticle size and shape after initial crude nanoparticles have been synthesized, and gain better understanding of the chemical mechanism details. Specific objectives for the past twentynine months since the grant began have been to (1) Secure and train personnel;as of 2011, a postdoc Deepa Jose, female from the Indian Institute of Science in Bangalore, India; Yijun Sun, a second year graduate student, female from China; and Jessica Changstrom, female from the USA, GK12 fellow (program for enhancing teaching ability) are actively carrying out research. (2) Find out what happens to sulfur bound hydrogen of thiol when it interacts with gold nanoparticles. Our findings are discussed in detail later. (3) Determine the effect of particle size, shape, and temperature on dodecyl thiol assited digestive ripening of gold nanoparticles. See our discussions later. (4) To understand in detail the ligand interaction in molecular clusters and nanoparticles (5) Determine the effect of chain length of amines on Au nanoparticle size under digestive ripening conditions (carbon chain length varied from 4-18). (6) Determine the catalytic activity

  9. Metal-Controlled Magnetoresistance at Room Temperature in Single-Molecule Devices.

    PubMed

    Aragonès, Albert C; Aravena, Daniel; Valverde-Muñoz, Francisco J; Real, José Antonio; Sanz, Fausto; Díez-Pérez, Ismael; Ruiz, Eliseo

    2017-03-03

    The appropriate choice of the transition metal complex and metal surface electronic structure opens the possibility to control the spin of the charge carriers through the resulting hybrid molecule/metal spinterface in a single-molecule electrical contact at room temperature. The single-molecule conductance of a Au/molecule/Ni junction can be switched by flipping the magnetization direction of the ferromagnetic electrode. The requirements of the molecule include not just the presence of unpaired electrons: the electronic configuration of the metal center has to provide occupied or empty orbitals that strongly interact with the junction metal electrodes and that are close in energy to their Fermi levels for one of the electronic spins only. The key ingredient for the metal surface is to provide an efficient spin texture induced by the spin-orbit coupling in the topological surface states that results in an efficient spin-dependent interaction with the orbitals of the molecule. The strong magnetoresistance effect found in this kind of single-molecule wire opens a new approach for the design of room-temperature nanoscale devices based on spin-polarized currents controlled at molecular level.

  10. Bap31 enhances the endoplasmic reticulum export and quality control of human class I MHC molecules.

    PubMed

    Ladasky, John J; Boyle, Sarah; Seth, Malini; Li, Hewang; Pentcheva, Tsvetelina; Abe, Fumiyoshi; Steinberg, Steven J; Edidin, Michael

    2006-11-01

    The assembly of class I MHC molecules and their export from the endoplasmic reticulum (ER) is governed by chaperones and accessory proteins. We present evidence that the putative cargo receptor protein Bap31 participates in the transport and the quality control of human class I molecules. Transfection of the human adenocarcinoma cell line HeLa with yellow fluorescent protein-Bap31 chimeras increased surface levels of class I in a dose-dependent manner, by as much as 3.7-fold. The increase in surface class I resulted from an increase in the rate of export of newly synthesized class I molecules to the cell surface and from an increase in the stability of the exported molecules. We propose that Bap31 performs quality control on class I molecules in two distinct phases: first, by exporting peptide-loaded class I molecules to the ER/Golgi intermediate compartment, and second, by retrieving class I molecules that have lost peptides in the acidic post-ER environment. This function of Bap31 is conditional or redundant, because we find that Bap31 deficiency does not reduce surface class I levels. Overexpression of the Bap31 homolog, Bap29, decreases surface class levels in HeLa, indicating that it does not substitute for Bap31.

  11. Stable and controlled amphoteric doping by encapsulation of organic molecules inside carbon nanotubes.

    PubMed

    Takenobu, Taishi; Takano, Takumi; Shiraishi, Masashi; Murakami, Yousuke; Ata, Masafumi; Kataura, Hiromichi; Achiba, Yohji; Iwasa, Yoshihiro

    2003-10-01

    Single-walled carbon nanotubes (SWNTs) have strong potential for molecular electronics, owing to their unique structural and electronic properties. However, various outstanding issues still need to be resolved before SWNT-based devices can be made. In particular, large-scale, air-stable and controlled doping is highly desirable. Here we present a method for integrating organic molecules into SWNTs that promises to push the performance limit of these materials for molecular electronics. Reaction of SWNTs with molecules having large electron affinity and small ionization energy achieved p- and n-type doping, respectively. Optical characterization revealed that charge transfer between SWNTs and molecules starts at certain critical energies. X-ray diffraction experiments revealed that molecules are predominantly encapsulated inside SWNTs, resulting in an improved stability in air. The simplicity of the synthetic process offers a viable route for the large-scale production of SWNTs with controlled doping states.

  12. Ultrafast optical coherent control of individual electron and hole spins in a semiconductor quantum dot

    NASA Astrophysics Data System (ADS)

    de Greve, Kristiaan

    2012-02-01

    We report on the complete optical coherent control of individual electron and hole spin qubits in InAs quantum dots. With a magnetic field in Voigt geometry, broadband, detuned optical pulses couple the spin-split ground states, resulting in Rabi flopping. In combination with the Larmor precession around the external magnetic field, this allows an arbitrary single-qubit operation to be realized in less than 20 picoseconds [1,2]. Slow fluctuations in the spin's environment lead to shot-to-shot variations in the Larmor precession frequency. In a time-ensemble measurement, these would prevent a measurement of the true decoherence of the qubit, and instead give rise to ensemble dephasing. This effect was overcome by implementing a spin echo measurement scheme for both electron and hole spins, where an optical π-pulse refocuses the spin coherence and filters out the slow variations in Larmor precession frequency. We measured coherence times up to 3 microseconds [2,3]. Finally, our optical pulse manipulation scheme allows us to probe the hyperfine interaction between the single spin and the nuclei in the quantum dot. Interesting non-Markovian dynamics could be observed in the free-induction decay of a single electron spin, whereas the complete absence of such effects illustrates the reduction of the hyperfine interaction for hole spin qubits. We measured and modeled these effects, and explain the non-Markovian electron spin dynamics as involving a feedback effect resulting from both the strong Overhauser shift of the electron spin and spin dependent nuclear relaxation [2,4]. [4pt] [1] D. Press, T. D. Ladd, B. Zhang and Y. Yamamoto, Nature 456, 218 (2008)[0pt] [2] K. De Greve, P. McMahon, D. Press et al., Nat. Phys. 7, 872 (2011)[0pt] [3] D. Press, K. De Greve, P. McMahon et al., Nat. Phot. 4, 367 (2010)[0pt] [4] T. D. Ladd, D. Press, K. De Greve et al., Phys. Rev. Lett. 105, 107401 (2010)

  13. Coherent structures in plasma-actuator controlled supersonic jets: Axisymmetric and mixed azimuthal modes

    NASA Astrophysics Data System (ADS)

    Gaitonde, D. V.; Samimy, M.

    2011-09-01

    High-fidelity simulations are employed to study the effect of eight localized arc filament plasma actuators placed around the periphery of a Mach 1.3 converging-diverging nozzle exit. Emphasis is placed on understanding the coherent structures generated by axisymmetric (m = 0), flapping or first mixed (m = ±1) and second mixed (m = ±2) modes, which are excited at the jet column-mode frequency corresponding to a Strouhal number based on jet diameter of 0.3. Baseline (no control) and constant excitation (actuators on continuously) cases are also simulated. Comparisons with experimental results indicate that the computational model reproduces the main features induced by the actuators. Furthermore, the mean flow exhibits many similarities with the theoretical predictions of Cohen and Wygnanski [J. Fluid Mech. 176, 221 (1987)]. Overall, the results indicate a complex coherent structure generation, evolution, and disintegration process. For m = ±1, the phase-averaged flow reveals successive distorted elliptic vortex rings with axes in the flapping plane but alternating on either side of the jet axis. This generates a chain of structures each of which interacts with its predecessor on one side of the major plane and its successor on the other. Through self and mutual induction, the leading segment of each loop is pinched and passes through the previous ring before rapidly breaking up. The m = ±2 mode yields elliptic structures with major axes of successive rings being aligned with the two symmetry planes, which are orthogonal to each other. The minor axis side is pulled downstream faster than the rest of the structure because of the higher velocity near the jet centerline and self-induced effects, yielding a horse-shoe shape when viewed in profile. The m = 0 mode exhibits axisymmetric roll-up events, with vortex ribs in the braid regions connecting successive large coherent structures. The constant excitation (with largest energy input) and baseline cases are similar

  14. Multilayer films with nanocontainers: redox-controlled reversible encapsulation of guest molecules.

    PubMed

    Zhang, Jiawei; Liu, Yiliu; Yuan, Bin; Wang, Zhiqiang; Schönhoff, Monika; Zhang, Xi

    2012-11-19

    Stable multilayer films with cucurbit[8]uril have been fabricated on the basis of the alternating layer-by-layer assembly of a novel side-chain pseudopolyrotaxane and a photoreactive polyanion. The as-prepared multilayer films exhibit good properties as surface-imprinted multilayers, because cucurbit[8]uril molecules that are locked inside the multilayers can act as nanocontainers with specific binding to certain guest molecules, and the loading and release of the guest is redox-controllable and reversible.

  15. Geometries for the coherent control of four-wave mixing in graphene multilayers

    PubMed Central

    Rao, Shraddha M.; Lyons, Ashley; Roger, Thomas; Clerici, Matteo; Zheludev, Nikolay I.; Faccio, Daniele

    2015-01-01

    Deeply sub-wavelength two-dimensional films may exhibit extraordinarily strong nonlinear effects. Here we show that 2D films exhibit the remarkable property of a phase-controllable nonlinearity, i.e., the amplitude of the nonlinear polarisation wave in the medium can be controlled via the pump beam phase and determines whether a probe beam will “feel” or not the nonlinearity. This is in stark contrast to bulk nonlinearities where propagation in the medium averages out any such phase dependence. We perform a series of experiments in multilayer graphene that highlight some of the consequences of the optical nonlinearity phase-dependence, such as the coherent control of nonlinearly diffracted beams, single-pump-beam induced phase-conjugation and the demonstration of a nonlinear mirror characterised by negative reflection. The observed phase sensitivity is not specific to graphene but rather is solely a result of the dimensionality and is therefore expected in all 2D materials. PMID:26486075

  16. The use and manipulation of insect reproductive molecules for controlling insect populations

    USDA-ARS?s Scientific Manuscript database

    The use and manipulation of insect reproductive molecules, and the genes that encode them, provides a variety of methods to control insect fertility and thus a means of population control for insect pests. Towards this end, we first studied the yolk polypeptide gene from the caribfly, Anastrepha su...

  17. Coherence, the Rebel Angel.

    ERIC Educational Resources Information Center

    Buchmann, Margret; Floden, Robert E.

    1992-01-01

    Among concepts that seem to be the guardian angels of school reform, coherence is a rebel angel, advancing human learning, but escaping control. Coherence must not be confused with consistency. It allows for change and imagination but remains true to concepts and experiences that construct coherence without fabricating consistency. (SLD)

  18. Creation of Long-Term Coherent Optical Memory via Controlled Nonlinear Interactions in Bose-Einstein Condensates

    SciTech Connect

    Zhang Rui; Garner, Sean R.; Hau, Lene Vestergaard

    2009-12-04

    A Bose-Einstein condensate confined in an optical dipole trap is used to generate long-term coherent memory for light, and storage times of more than 1 s are observed. Phase coherence of the condensate as well as controlled manipulations of elastic and inelastic atomic scattering processes are utilized to increase the storage fidelity by several orders of magnitude over previous schemes. The results have important applications for creation of long-distance quantum networks and for generation of entangled states of light and matter.

  19. Spatiotemporal stability of a femtosecond hard-x-ray undulator source studied by control of coherent optical phonons.

    PubMed

    Beaud, P; Johnson, S L; Streun, A; Abela, R; Abramsohn, D; Grolimund, D; Krasniqi, F; Schmidt, T; Schlott, V; Ingold, G

    2007-10-26

    We report on the temporal and spatial stability of the first tunable femtosecond undulator hard-x-ray source for ultrafast diffraction and absorption experiments. The 2.5-1 Angstrom output radiation is driven by an initial 50 fs laser pulse employing the laser-electron slicing technique. By using x-ray diffraction to probe laser-induced coherent optical phonons in bulk bismuth, we estimate an x-ray pulse duration of 140+/-30 fs FWHM with timing drifts below 30 fs rms measured over 5 days. Optical control of coherent lattice motion is demonstrated.

  20. Altered corticomuscular coherence elicited by paced isotonic contractions in individuals with cerebral palsy: a case-control study.

    PubMed

    Riquelme, Inmaculada; Cifre, Ignacio; Muñoz, Miguel A; Montoya, Pedro

    2014-12-01

    The purpose of the study was to analyze corticomuscular coherence during planning and execution of simple hand movements in individuals with cerebral palsy (CP) and healthy controls (HC). Fourteen individuals with CP and 15 HC performed voluntary paced movements (opening and closing the fist) in response to a warning signal. Simultaneous scalp EEG and surface EMG of extensor carpi radialis brevis were recorded during 15 isotonic contractions. Time-frequency corticomuscular coherence (EMG-C3/C4) before and during muscular contraction, as well as EMG intensity, onset latency and duration were analyzed. Although EMG intensity was similar in both groups, individuals with CP exhibited longer onset latency and increased duration of the muscular contraction than HC. CP also showed higher corticomuscular coherence in beta EEG band during both planning and execution of muscular contraction, as well as lower corticomuscular coherence in gamma EEG band at the beginning of the contraction as compared with HC. In conclusion, our results suggest that individuals with CP are characterized by an altered functional coupling between primary motor cortex and effector muscles during planning and execution of isotonic contractions. In addition, the usefulness of corticomuscular coherence as a research tool for exploring deficits in motor central processing in persons with early brain damage is discussed.

  1. Spatially, Temporally, and Quantitatively Controlled Delivery of Broad Range of Molecules into Selected Cells through Plasmonic Nanotubes.

    PubMed

    Messina, Gabriele C; Dipalo, Michele; La Rocca, Rosanna; Zilio, Pierfrancesco; Caprettini, Valeria; Proietti Zaccaria, Remo; Toma, Andrea; Tantussi, Francesco; Berdondini, Luca; De Angelis, Francesco

    2015-11-25

    A Universal plasmonic/microfluidic platform for spatial and temporal controlled intracellular delivery is described. The system can inject/transfect the desired amount of molecules with an efficacy close to 100%. Moreover, it is highly scalable from single cells to large ensembles without administering the molecules to an extracellular bath. The latter enables quantitative control over the amount of injected molecules.

  2. Wireless, Web-Based Interactive Control of Optical Coherence Tomography with Mobile Devices.

    PubMed

    Mehta, Rajvi; Nankivil, Derek; Zielinski, David J; Waterman, Gar; Keller, Brenton; Limkakeng, Alexander T; Kopper, Regis; Izatt, Joseph A; Kuo, Anthony N

    2017-01-01

    Optical coherence tomography (OCT) is widely used in ophthalmology clinics and has potential for more general medical settings and remote diagnostics. In anticipation of remote applications, we developed wireless interactive control of an OCT system using mobile devices. A web-based user interface (WebUI) was developed to interact with a handheld OCT system. The WebUI consisted of key OCT displays and controls ported to a webpage using HTML and JavaScript. Client-server relationships were created between the WebUI and the OCT system computer. The WebUI was accessed on a cellular phone mounted to the handheld OCT probe to wirelessly control the OCT system. Twenty subjects were imaged using the WebUI to assess the system. System latency was measured using different connection types (wireless 802.11n only, wireless to remote virtual private network [VPN], and cellular). Using a cellular phone, the WebUI was successfully used to capture posterior eye OCT images in all subjects. Simultaneous interactivity by a remote user on a laptop was also demonstrated. On average, use of the WebUI added only 58, 95, and 170 ms to the system latency using wireless only, wireless to VPN, and cellular connections, respectively. Qualitatively, operator usage was not affected. Using a WebUI, we demonstrated wireless and remote control of an OCT system with mobile devices. The web and open source software tools used in this project make it possible for any mobile device to potentially control an OCT system through a WebUI. This platform can be a basis for remote, teleophthalmology applications using OCT.

  3. Coherent Control of Population Transfer via Linear Chirp in Liquid Solution: The Role of Motional Narrowing.

    PubMed

    McRobbie, Porscha L; Geva, Eitan

    2016-05-19

    The conditions under which linear chirp can be used to control population transfer between the electronic states of a chromophore dissolved in liquid solution are investigated. To this end, we model the chromophore as a two-state system with shifted electronic potential energy surfaces and a fluctuating electronic transition frequency. The fluctuations are described as an exponentially correlated Gaussian stochastic process, which can be characterized by the average fluctuation amplitude, σ, and correlation time, τc. The time-dependent Schrödinger equation is solved numerically for an ensemble of stochastic histories, at different values of σ and τc, and under a wide range of pulse intensities and linear chirp coefficients. In the limit τc → ∞, we find that control diminishes rapidly as soon as σ exceeds the bandwidth of the pulse. However, we also find that control can be regained by reducing τc. We attribute this trend to motional narrowing, whereby decreasing τc narrows down the effective bandwidth of the solvent-induced fluctuations. The results suggest that the choice of methanol as a solvent in the actual experimental demonstration of chirp control by Cerullo et al. [ Chem. Phys. Lett. 1996 , 262 , 362 - 368 ] may have contributed to its success, due to the particularly short τc (∼20 fs) that the rapid librations of this hydrogen bonded liquid give rise to. The results also give rise to the rather surprising prediction that coherent control in liquid solution can be strongly dependent on the choice of solvent and be improved upon by choosing solvents that correspond to lower values of στc.

  4. Wireless, Web-Based Interactive Control of Optical Coherence Tomography with Mobile Devices

    PubMed Central

    Mehta, Rajvi; Nankivil, Derek; Zielinski, David J.; Waterman, Gar; Keller, Brenton; Limkakeng, Alexander T.; Kopper, Regis; Izatt, Joseph A.; Kuo, Anthony N.

    2017-01-01

    Purpose Optical coherence tomography (OCT) is widely used in ophthalmology clinics and has potential for more general medical settings and remote diagnostics. In anticipation of remote applications, we developed wireless interactive control of an OCT system using mobile devices. Methods A web-based user interface (WebUI) was developed to interact with a handheld OCT system. The WebUI consisted of key OCT displays and controls ported to a webpage using HTML and JavaScript. Client–server relationships were created between the WebUI and the OCT system computer. The WebUI was accessed on a cellular phone mounted to the handheld OCT probe to wirelessly control the OCT system. Twenty subjects were imaged using the WebUI to assess the system. System latency was measured using different connection types (wireless 802.11n only, wireless to remote virtual private network [VPN], and cellular). Results Using a cellular phone, the WebUI was successfully used to capture posterior eye OCT images in all subjects. Simultaneous interactivity by a remote user on a laptop was also demonstrated. On average, use of the WebUI added only 58, 95, and 170 ms to the system latency using wireless only, wireless to VPN, and cellular connections, respectively. Qualitatively, operator usage was not affected. Conclusions Using a WebUI, we demonstrated wireless and remote control of an OCT system with mobile devices. Translational Relevance The web and open source software tools used in this project make it possible for any mobile device to potentially control an OCT system through a WebUI. This platform can be a basis for remote, teleophthalmology applications using OCT. PMID:28138415

  5. Coherent control of charge exchange in strong-field dissociation of LiF

    NASA Astrophysics Data System (ADS)

    Armstrong, Greg; Esry, Brett

    2016-05-01

    The alkali-metal-halides family of molecules are useful prototypes in the study of laser-assisted charge exchange. Typically these molecules possess a field-free crossing between the ionic and covalent diabatic Born-Oppenheimer potential curves, leading to Li+ + F- and Li + F in LiF. These channels are energetically well-separated from higher-lying potentials, and may be easily distinguished experimentally. Moreover, charge exchange involves non-adiabatic transitions between the ionic and covalent channels, thereby allowing the investigation of physics beyond the Born-Oppenheimer approximation. The focus of this work is to control the preference between ionic and covalent dissociative products. We solve the time-dependent Schrödinger equation for the nuclear motion in full dimensionality, and investigate a pump-probe scheme for charge-exchange control. The degree of control is investigated by calculating the kinetic-energy release spectrum as a function of pump-probe delay for the ionic and covalent fragments. This work is supported by the Chemical Sciences, Geosciences, and Biosciences Division, Office of Basic Energy Sciences, Office of Science, U.S. Department of Energy.

  6. Wigner spectrum and coherent feedback control of continuous-mode single-photon Fock states

    NASA Astrophysics Data System (ADS)

    Dong, Zhiyuan; Cui, Lei; Zhang, Guofeng; Fu, Hongchen

    2016-10-01

    Single photons are very useful resources in quantum information science. In real applications it is often required that the photons have a well-defined spectral (or equivalently temporal) modal structure. For example, a rising exponential pulse is able to fully excite a two-level atom while a Gaussian pulse cannot. This motivates the study of continuous-mode single-photon Fock states. Such states are characterized by a spectral (or temporal) pulse shape. In this paper we investigate the statistical property of continuous-mode single-photon Fock states. Instead of the commonly used normal ordering (Wick order), the tool we proposed is the Wigner spectrum. The Wigner spectrum has two advantages: (1) it allows to study continuous-mode single-photon Fock states in the time domain and frequency domain simultaneously; (2) because it can deal with the Dirac delta function directly, it has the potential to provide more information than the normal ordering where the Dirac delta function is always discarded. We also show how various control methods in particular coherent feedback control can be used to manipulate the pulse shapes of continuous-mode single-photon Fock states.

  7. Coherent Control of Nanoscale Ballistic Currents in Transition Metal Dichalcogenide ReS2.

    PubMed

    Cui, Qiannan; Zhao, Hui

    2015-04-28

    Transition metal dichalcogenides are predicted to outperform traditional semiconductors in ballistic devices with nanoscale channel lengths. So far, experimental studies on charge transport in transition metal dichalcogenides are limited to the diffusive regime. Here we show, using ReS2 as an example, all-optical injection, detection, and coherent control of ballistic currents. By utilizing quantum interference between one-photon and two-photon interband transition pathways, ballistic currents are injected in ReS2 thin film samples by a pair of femtosecond laser pulses. We find that the current decays on an ultrafast time scale, resulting in an electron transport of only a fraction of one nanometer. Following the relaxation of the initially injected momentum, backward motion of the electrons for about 1 ps is observed, driven by the Coulomb force from the oppositely moved holes. We also show that the injected current can be controlled by the phase of the laser pulses. These results demonstrate a new platform to study ballistic transport of nonequilibrium carriers in transition metal dichalcogenides.

  8. Creation and control of entanglement by time-delayed quantum-coherent feedback

    NASA Astrophysics Data System (ADS)

    Hein, Sven M.; Carmele, Alexander; Knorr, Andreas

    2016-03-01

    Quantum information science relies on the feature of distant quantum entities (mostly "qubits") to form non-local states. A main challenge consists of generating such non-local entangled states between qubits. We exploit the fact that for coupled qubits, the eigenstates of the coupled system are usually highly entangled, and of different excitation energies. This allows to address the different entangled eigenstates by frequency-dependent control schemes. In our proposal, we present such a control mechanism, and demonstrate how it can be used to create entanglement from a fully separable initial state. The mechanism of our choice is time-delayed quantum-coherent feedback. If a qubit occupation decays via the emission of a photon, one can store this photon for a delay time τ and couple the radiation back into the qubit afterwards. Through the choice of τ, one can set the phase of the feedback, which will then lead to either an increased or decreased qubit decay. Since this phase depends on sin(ωτ), this effect strongly depends on the qubit frequency ω. In particular, it can be used to separate different entangled states in a quantum network by enhancing the decay of all entangled eigenstates except one. We discuss this protocol on the example of two coupled qubits, and analyze in detail its effectiveness depending on the feedback delay time τ.

  9. Effect of the Gouy phase on the coherent phase control of chemical reactions

    SciTech Connect

    Gordon, Robert J.; Barge, Vishal J.

    2007-11-28

    We show how the spatial phase of a focused laser beam may be used as a tool for controlling the branching ratio of a chemical reaction. Guoy discovered [Acad. Sci., Paris, C. R. 110, 1250 (1890)] that when an electromagnetic wave passes through a focus its phase increases by {pi}. In a coherent control scheme involving the absorption of n photons of frequency {omega}{sub m} and m photons of frequency {omega}{sub n}, the overall phase shift produced by the Gouy phase is (n-m){pi}. At any given point in space, this phase shift is identical for all reaction products. Nevertheless, if the yields for different reaction channels have different intensity dependencies, the Gouy phase produces a net phase lag between the products that varies with the axial coordinate of the laser focus. We obtain here analytical and numerical values of this phase as the laser focus is scanned across the diameter of the molecular beam, taking into account the Rayleigh range and astigmatism of the laser beam and saturation of the transition. We also show that the modulation depth of the interference pattern may be increased by optimizing the relative intensities of the two fields.

  10. Single molecule tunneling conductance: The temperature and length dependences controlled by conformational fluctuations

    NASA Astrophysics Data System (ADS)

    Kornyshev, A. A.; Kuznetsov, A. M.

    2006-05-01

    We present a model for a tunnelling conductance of a chain molecule controlled by fluctuations of relative conformations between nearest neighbour units of the chain molecule. The model leads to a simple formula which in one regime reproduces recently reported Arrhenius dependences for alkanedithiols [W. Haiss, H. van Zalinge, D. Bethel, J. Ulstrup, D.J. Schiffrin, R.J. Nichols, Faraday Discuss. 131 (19) (2005)] with an activation energy proportional to the length of the molecule, whereas in other regimes it shows activationless behaviour corresponding to the tunnelling across more rigid molecules. The general formula covers the transition between the two limits, predicting some new dependences that could be interesting to verify experimentally.

  11. [From endoplasmic reticulum to Golgi apparatus: a secretory pathway controlled by signal molecules].

    PubMed

    Wang, Jiasheng; Luo, Jianhong; Zhang, Xiaomin

    2013-07-01

    Protein transport from endoplasmic reticulum (ER) to Golgi apparatus has long been known to be a central process for protein quality control and sorting. Recent studies have revealed that a large number of signal molecules are involved in regulation of membrane trafficking through ER, ER-Golgi intermediate compartment and Golgi apparatus. These molecules can significantly change the transport rate of proteins by regulating vesicle budding and fusion. Protein transport from ER to Golgi apparatus is not only controlled by signal pathways triggered from outside the cell, it is also regulated by feedback signals from the transport pathway.

  12. Coherent control of population transfer between vibrational states in an optical lattice via two-path quantum interference.

    PubMed

    Zhuang, Chao; Paul, Christopher R; Liu, Xiaoxian; Maneshi, Samansa; Cruz, Luciano S; Steinberg, Aephraim M

    2013-12-06

    We demonstrate coherent control of population transfer between vibrational states in an optical lattice by using interference between a one-phonon transition at 2ω and a two-phonon transition at ω. The ω and 2ω transitions are driven by phase- and amplitude-modulation of the lattice laser beams, respectively. By varying the relative phase of these two pathways, we control the branching ratio between transitions to the first excited state and those to the higher states. Our best result shows a branching ratio of 17±2, which is the highest among coherent control experiments using analogous schemes. Such quantum control techniques may find broad application in suppressing leakage errors in a variety of quantum information architectures.

  13. Fast and automatic depth control of iterative bone ablation based on optical coherence tomography data

    NASA Astrophysics Data System (ADS)

    Fuchs, Alexander; Pengel, Steffen; Bergmeier, Jan; Kahrs, Lüder A.; Ortmaier, Tobias

    2015-07-01

    Laser surgery is an established clinical procedure in dental applications, soft tissue ablation, and ophthalmology. The presented experimental set-up for closed-loop control of laser bone ablation addresses a feedback system and enables safe ablation towards anatomical structures that usually would have high risk of damage. This study is based on combined working volumes of optical coherence tomography (OCT) and Er:YAG cutting laser. High level of automation in fast image data processing and tissue treatment enables reproducible results and shortens the time in the operating room. For registration of the two coordinate systems a cross-like incision is ablated with the Er:YAG laser and segmented with OCT in three distances. The resulting Er:YAG coordinate system is reconstructed. A parameter list defines multiple sets of laser parameters including discrete and specific ablation rates as ablation model. The control algorithm uses this model to plan corrective laser paths for each set of laser parameters and dynamically adapts the distance of the laser focus. With this iterative control cycle consisting of image processing, path planning, ablation, and moistening of tissue the target geometry and desired depth are approximated until no further corrective laser paths can be set. The achieved depth stays within the tolerances of the parameter set with the smallest ablation rate. Specimen trials with fresh porcine bone have been conducted to prove the functionality of the developed concept. Flat bottom surfaces and sharp edges of the outline without visual signs of thermal damage verify the feasibility of automated, OCT controlled laser bone ablation with minimal process time.

  14. Ultrafast Quantum Control and Quantum Processing in the Vibronic States of Molecules and Solids

    NASA Astrophysics Data System (ADS)

    Sussman, Benjamin; Bustard, Philip; England, Duncan; Lausten, Rune

    2014-05-01

    The unusual features of quantum mechanics are enabling the development of technologies not possible with classical physics, including applications in secure communications, quantum processing, and enhanced measurement. Efforts to build these devices utilize nonclassical states in numerous quantum systems, including cavity quantum electrodynamics, trap ions, nuclear spins, etc. as the basis for many prototypes. Here we investigate vibronic states in both molecules and bulk solids as distinct alternatives. We demonstrate a memory for light based on storing photons in the vibrations of hydrogen molecules and the optical phonons of diamond. Both classical and nonclassical photon states are used. These THz-bandwidth memories can be used to store femtosecond pulses for many operational time bins before the states decohere, making them viable for local photonic processing. We investigate decoherence and major sources of competing noise. While sustaining quantum coherence is critical for most quantum processing, rapid dephasing can also be used as a resource in these systems for rapid quantum random number generation, suitable for high-performance cryptography. NSERC

  15. Composite microsphere-functionalized scaffold for the controlled release of small molecules in tissue engineering

    PubMed Central

    Pandolfi, Laura; Minardi, Silvia; Taraballi, Francesca; Liu, Xeuwu; Ferrari, Mauro; Tasciotti, Ennio

    2016-01-01

    Current tissue engineering strategies focus on restoring damaged tissue architectures using biologically active scaffolds. The ideal scaffold would mimic the extracellular matrix of any tissue of interest, promoting cell proliferation and de novo extracellular matrix deposition. A plethora of techniques have been evaluated to engineer scaffolds for the controlled and targeted release of bioactive molecules to provide a functional structure for tissue growth and remodeling, as well as enhance recruitment and proliferation of autologous cells within the implant. Recently, novel approaches using small molecules, instead of growth factors, have been exploited to regulate tissue regeneration. The use of small synthetic molecules could be very advantageous because of their stability, tunability, and low cost. Herein, we propose a chitosan–gelatin scaffold functionalized with composite microspheres consisting of mesoporous silicon microparticles and poly(dl-lactic-co-glycolic acid) for the controlled release of sphingosine-1-phospate, a small molecule of interest. We characterized the platform with scanning electron microscopy, Fourier transform infrared spectroscopy, and confocal microscopy. Finally, the biocompatibility of this multiscale system was analyzed by culturing human mesenchymal stem cells onto the scaffold. The presented strategy establishes the basis of a versatile scaffold for the controlled release of small molecules and for culturing mesenchymal stem cells for regenerative medicine applications. PMID:26977286

  16. Biexcitonic effects in the coherent control of the excitonic polarization detected in six-wave-mixing signals

    NASA Astrophysics Data System (ADS)

    Voss, T.; Breunig, H. G.; Rückmann, I.; Gutowski, J.; Axt, V. M.; Kuhn, T.

    2002-10-01

    Coherently controlled six-wave-mixing experiments on a ZnSe single quantum well are performed with different polarizations of the excitation pulses to enable or disable the creation of a biexcitonic polarization. A significant contribution of the biexcitonic polarization and other two-pair correlations is observed in the signal which is mainly modulated with the exciton transition frequency. A microscopic theory based on the dynamics controlled truncation scheme including six-point correlations is able to reproduce the experimental results.

  17. Precision control of charge coherence in parallel double dot systems through spin-orbit interaction

    NASA Astrophysics Data System (ADS)

    Jin, Jinshuang; Tu, Matisse Wei-Yuan; Wang, Nien-En; Zhang, Wei-Min

    2013-08-01

    In terms of the exact quantum master equation solution for open electronic systems, the coherent dynamics of two charge states described by two parallel quantum dots with one fully polarized electron on either dot is investigated in the presence of spin-orbit interaction. We demonstrate that the double dot system can stay in a dynamically decoherence free space. The coherence between two double dot charge states can be precisely manipulated through a spin-orbit coupling. The effects of the temperature, the finite bandwidth of lead, and the energy deviations during the coherence manipulation are also explored.

  18. Changes in Frontal EEG Coherence across Infancy Predict Cognitive Abilities at Age 3: The Mediating Role of Attentional Control

    PubMed Central

    Whedon, Margaret; Perry, Nicole B.; Calkins, Susan D.; Bell, Martha Ann

    2016-01-01

    Theoretical perspectives of cognitive development have maintained that functional integration of the prefrontal cortex across infancy underlies the emergence of attentional control and higher cognitive abilities in early childhood. To investigate these proposed relations, we tested whether functional integration of prefrontal regions across the second half of the first year predicted observed cognitive performance in early childhood indirectly through observed attentional control one year prior (N=300). Results indicated that greater change in left—but not right—frontal EEG coherence between 5- and 10-months was positively associated with attentional control, cognitive flexibility, receptive language, and behavioral inhibitory control. Specifically, a larger increase in coherence between left frontal regions was positively associated with accuracy on a visual search task at age 2; and visual search accuracy was positively associated with receptive vocabulary, performance on a set-shifting task (DCCS), and delay of gratification at age 3. Finally, the indirect effects from the change in left frontal EEG coherence to 3-year cognitive flexibility, receptive language, and behavioral inhibitory control were significant, suggesting that internally controlled attention is a mechanism through which early neural maturation influences children’s cognitive development. PMID:27441486

  19. A simulation environment for assisting system design of coherent laser doppler wind sensor for active wind turbine pitch control

    NASA Astrophysics Data System (ADS)

    Shinohara, Leilei; Pham Tran, Tuan Anh; Beuth, Thorsten; Umesh Babu, Harsha; Heussner, Nico; Bogatscher, Siegwart; Danilova, Svetlana; Stork, Wilhelm

    2013-05-01

    In order to assist a system design of laser coherent Doppler wind sensor for active pitch control of wind turbine systems (WTS), we developed a numerical simulation environment for modeling and simulation of the sensor system. In this paper we present this simulation concept. In previous works, we have shown the general idea and the possibility of using a low cost coherent laser Doppler wind sensing system for an active pitch control of WTS in order to achieve a reduced mechanical stress, increase the WTS lifetime and therefore reduce the electricity price from wind energy. Such a system is based on a 1.55μm Continuous-Wave (CW) laser plus an erbium-doped fiber amplifier (EDFA) with an output power of 1W. Within this system, an optical coherent detection method is chosen for the Doppler frequency measurement in megahertz range. A comparatively low cost short coherent length laser with a fiber delay line is used for achieving a multiple range measurement. In this paper, we show the current results on the improvement of our simulation by applying a Monte Carlo random generation method for positioning the random particles in atmosphere and extend the simulation to the entire beam penetrated space by introducing a cylindrical co-ordinate concept and meshing the entire volume into small elements in order to achieve a faster calculation and gain more realistic simulation result. In addition, by applying different atmospheric parameters, such as particle sizes and distributions, we can simulate different weather and wind situations.

  20. Controlling Spatial Distributions of Molecules in Multicomponent Organic Crystals, with Quantitative Mapping by Confocal Raman Microspectrometry

    PubMed Central

    2013-01-01

    We report four experimental strategies for controlling the three-dimensional arrangement of molecules in multicomponent organic crystals, exploiting confocal Raman microspectrometry to quantify the three-dimensional spatial distributions. Specifically, we focus on controlling the distribution of two types of guest molecule in solid organic inclusion compounds to produce composite core–shell crystals, crystals with a homogeneous distribution of the components, crystals with continuous compositional variation from the core to the surface, and crystals with alternating shells of the components. In this context, confocal Raman microspectrometry is particularly advantageous over optical microscopy as it is nondestructive, offers micrometric spatial resolution, and relies only on the component molecules having different vibrational properties. PMID:24004273

  1. Rotational Control of Asymmetric Molecules: Dipole- versus Polarizability-Driven Rotational Dynamics

    NASA Astrophysics Data System (ADS)

    Damari, Ran; Kallush, Shimshon; Fleischer, Sharly

    2016-09-01

    We experimentally study the optical- and terahertz-induced rotational dynamics of asymmetric molecules in the gas phase. Terahertz and optical fields are identified as two distinct control handles over asymmetric molecules, as they couple to the rotational degrees of freedom via the molecular dipole and polarizability selectively. The distinction between those two rotational handles is highlighted by different types of quantum revivals observed in long-duration (>100 ps ) field-free rotational evolution. The experimental results are in excellent agreement with random phase wave function (RPWF) simulations [Phys. Rev. A 91, 063420 (2015)] and provide verification of the RPWF as an efficient method for calculating asymmetric molecular dynamics at ambient temperatures, where exact calculation methods are practically not feasible. Our observations and analysis pave the way for orchestrated excitations by both optical and terahertz fields as complementary rotational handles that enable a plethora of new possibilities in three-dimensional rotational control of asymmetric molecules.

  2. Precise control of coupling strength in photonic molecules over a wide range using nanoelectromechanical systems

    PubMed Central

    Du, Han; Zhang, Xingwang; Chen, Guoqiang; Deng, Jie; Chau, Fook Siong; Zhou, Guangya

    2016-01-01

    Photonic molecules have a range of promising applications including quantum information processing, where precise control of coupling strength is critical. Here, by laterally shifting the center-to-center offset of coupled photonic crystal nanobeam cavities, we demonstrate a method to precisely and dynamically control the coupling strength of photonic molecules through integrated nanoelectromechanical systems with a precision of a few GHz over a range of several THz without modifying the nature of their constituent resonators. Furthermore, the coupling strength can be tuned continuously from negative (strong coupling regime) to zero (weak coupling regime) and further to positive (strong coupling regime) and vice versa. Our work opens a door to the optimization of the coupling strength of photonic molecules in situ for the study of cavity quantum electrodynamics and the development of efficient quantum information devices. PMID:27097883

  3. Ultrafast dynamics of single molecules.

    PubMed

    Brinks, Daan; Hildner, Richard; van Dijk, Erik M H P; Stefani, Fernando D; Nieder, Jana B; Hernando, Jordi; van Hulst, Niek F

    2014-04-21

    The detection of individual molecules has found widespread application in molecular biology, photochemistry, polymer chemistry, quantum optics and super-resolution microscopy. Tracking of an individual molecule in time has allowed identifying discrete molecular photodynamic steps, action of molecular motors, protein folding, diffusion, etc. down to the picosecond level. However, methods to study the ultrafast electronic and vibrational molecular dynamics at the level of individual molecules have emerged only recently. In this review we present several examples of femtosecond single molecule spectroscopy. Starting with basic pump-probe spectroscopy in a confocal detection scheme, we move towards deterministic coherent control approaches using pulse shapers and ultra-broad band laser systems. We present the detection of both electronic and vibrational femtosecond dynamics of individual fluorophores at room temperature, showing electronic (de)coherence, vibrational wavepacket interference and quantum control. Finally, two colour phase shaping applied to photosynthetic light-harvesting complexes is presented, which allows investigation of the persistent coherence in photosynthetic complexes under physiological conditions at the level of individual complexes.

  4. Coherent structures in swirling flows and their role in acoustic combustion control

    NASA Astrophysics Data System (ADS)

    Paschereit, Christian Oliver; Gutmark, Ephraim; Weisenstein, Wolfgang

    1999-09-01

    Interaction between flow instabilities and acoustic resonant modes and their effect on heat release were investigated and controlled in an experimental low-emission swirl stabilized combustor. Acoustic boundary conditions of the combustor were modified to excite combustion instability at various axisymmetric and helical unstable modes in a fully premixed combustion. The combustion unstable modes were related to flow instabilities in the recirculating wakelike region on the combustor axis and the separating shear layer at the sudden expansion (dump plane). Flow field measurements were performed in a water tunnel using a simulated combustor configuration. The water tunnel tests demonstrated the existence of several modes of flow instabilities in a highly swirling flow, modes which were shown to affect the combustion process. Mean and turbulent characteristics of the internal and external swirling shear layers were measured and unstable flow modes were identified. Instability modes during combustion were visualized by phase locked images of OH chemiluminescence. The axisymmetric mode showed large variation of the heat release during one cycle, while the helical modes showed variations in the radial location of maximal heat release. Closed loop active control system was employed to suppress the thermoacoustic pressure oscillations and to reduce NOx emissions. Microphone and OH emission detection sensors monitored the combustion process and provided input to the control system. An acoustic source modulated the airflow and thus affected the mixing process and the combustion. Effective suppression of the pressure oscillations and the concomitant reduction of NOx emissions were associated with a reduced coherence of the flow structures which excited the thermoacoustic instability.

  5. Single-molecule diodes with high rectification ratios through environmental control.

    PubMed

    Capozzi, Brian; Xia, Jianlong; Adak, Olgun; Dell, Emma J; Liu, Zhen-Fei; Taylor, Jeffrey C; Neaton, Jeffrey B; Campos, Luis M; Venkataraman, Latha

    2015-06-01

    Molecular electronics aims to miniaturize electronic devices by using subnanometre-scale active components. A single-molecule diode, a circuit element that directs current flow, was first proposed more than 40 years ago and consisted of an asymmetric molecule comprising a donor-bridge-acceptor architecture to mimic a semiconductor p-n junction. Several single-molecule diodes have since been realized in junctions featuring asymmetric molecular backbones, molecule-electrode linkers or electrode materials. Despite these advances, molecular diodes have had limited potential for applications due to their low conductance, low rectification ratios, extreme sensitivity to the junction structure and high operating voltages. Here, we demonstrate a powerful approach to induce current rectification in symmetric single-molecule junctions using two electrodes of the same metal, but breaking symmetry by exposing considerably different electrode areas to an ionic solution. This allows us to control the junction's electrostatic environment in an asymmetric fashion by simply changing the bias polarity. With this method, we reliably and reproducibly achieve rectification ratios in excess of 200 at voltages as low as 370 mV using a symmetric oligomer of thiophene-1,1-dioxide. By taking advantage of the changes in the junction environment induced by the presence of an ionic solution, this method provides a general route for tuning nonlinear nanoscale device phenomena, which could potentially be applied in systems beyond single-molecule junctions.

  6. High-Field High-Repetition-Rate Sources for the Coherent THz Control of Matter

    DOE PAGES

    Green, B.; Kovalev, S.; Asgekar, V.; ...

    2016-02-29

    Ultrashort flashes of THz light with low photon energies of a few meV, but strong electric or magnetic field transients have recently been employed to prepare various fascinating nonequilibrium states in matter. Here we present a new class of sources based on superradiant enhancement of radiation from relativistic electron bunches in a compact electron accelerator that we believe will revolutionize experiments in this field. Our prototype source generates high-field THz pulses at unprecedented quasi-continuous-wave repetition rates up to the MHz regime. We demonstrate parameters that exceed state-of-the-art laser-based sources by more than 2 orders of magnitude. The peak fields andmore » the repetition rates are highly scalable and once fully operational this type of sources will routinely provide 1 MV/cm electric fields and 0.3 T magnetic fields at repetition rates of few 100 kHz. In conclusion, we benchmark the unique properties by performing a resonant coherent THz control experiment with few 10 fs resolution.« less

  7. High-Field High-Repetition-Rate Sources for the Coherent THz Control of Matter

    SciTech Connect

    Green, B.; Kovalev, S.; Asgekar, V.; Geloni, G.; Lehnert, U.; Golz, T.; Kuntzsch, M.; Bauer, C.; Hauser, J.; Voigtlaender, J.; Wustmann, B.; Koesterke, I.; Schwarz, M.; Freitag, M.; Arnold, A.; Teichert, J.; Justus, M.; Seidel, W.; Ilgner, C.; Awari, N.; Nicoletti, D.; Kaiser, S.; Laplace, Y.; Rajasekaran, S.; Zhang, L.; Winnerl, S.; Schneider, H.; Schay, G.; Lorincz, I.; Rauscher, A. A.; Radu, I.; Mährlein, S.; Kim, T. H.; Lee, J. S.; Kampfrath, T.; Wall, S.; Heberle, J.; Malnasi-Csizmadia, A.; Steiger, A.; Müller, A. S.; Helm, M.; Schramm, U.; Cowan, T.; Michel, P.; Cavalleri, A.; Fisher, A. S.; Stojanovic, N.; Gensch, M.

    2016-02-29

    Ultrashort flashes of THz light with low photon energies of a few meV, but strong electric or magnetic field transients have recently been employed to prepare various fascinating nonequilibrium states in matter. Here we present a new class of sources based on superradiant enhancement of radiation from relativistic electron bunches in a compact electron accelerator that we believe will revolutionize experiments in this field. Our prototype source generates high-field THz pulses at unprecedented quasi-continuous-wave repetition rates up to the MHz regime. We demonstrate parameters that exceed state-of-the-art laser-based sources by more than 2 orders of magnitude. The peak fields and the repetition rates are highly scalable and once fully operational this type of sources will routinely provide 1 MV/cm electric fields and 0.3 T magnetic fields at repetition rates of few 100 kHz. In conclusion, we benchmark the unique properties by performing a resonant coherent THz control experiment with few 10 fs resolution.

  8. High-Field High-Repetition-Rate Sources for the Coherent THz Control of Matter.

    PubMed

    Green, B; Kovalev, S; Asgekar, V; Geloni, G; Lehnert, U; Golz, T; Kuntzsch, M; Bauer, C; Hauser, J; Voigtlaender, J; Wustmann, B; Koesterke, I; Schwarz, M; Freitag, M; Arnold, A; Teichert, J; Justus, M; Seidel, W; Ilgner, C; Awari, N; Nicoletti, D; Kaiser, S; Laplace, Y; Rajasekaran, S; Zhang, L; Winnerl, S; Schneider, H; Schay, G; Lorincz, I; Rauscher, A A; Radu, I; Mährlein, S; Kim, T H; Lee, J S; Kampfrath, T; Wall, S; Heberle, J; Malnasi-Csizmadia, A; Steiger, A; Müller, A S; Helm, M; Schramm, U; Cowan, T; Michel, P; Cavalleri, A; Fisher, A S; Stojanovic, N; Gensch, M

    2016-02-29

    Ultrashort flashes of THz light with low photon energies of a few meV, but strong electric or magnetic field transients have recently been employed to prepare various fascinating nonequilibrium states in matter. Here we present a new class of sources based on superradiant enhancement of radiation from relativistic electron bunches in a compact electron accelerator that we believe will revolutionize experiments in this field. Our prototype source generates high-field THz pulses at unprecedented quasi-continuous-wave repetition rates up to the MHz regime. We demonstrate parameters that exceed state-of-the-art laser-based sources by more than 2 orders of magnitude. The peak fields and the repetition rates are highly scalable and once fully operational this type of sources will routinely provide 1 MV/cm electric fields and 0.3 T magnetic fields at repetition rates of few 100 kHz. We benchmark the unique properties by performing a resonant coherent THz control experiment with few 10 fs resolution.

  9. High-Field High-Repetition-Rate Sources for the Coherent THz Control of Matter

    PubMed Central

    Green, B.; Kovalev, S.; Asgekar, V.; Geloni, G.; Lehnert, U.; Golz, T.; Kuntzsch, M.; Bauer, C.; Hauser, J.; Voigtlaender, J.; Wustmann, B.; Koesterke, I.; Schwarz, M.; Freitag, M.; Arnold, A.; Teichert, J.; Justus, M.; Seidel, W.; Ilgner, C.; Awari, N.; Nicoletti, D.; Kaiser, S.; Laplace, Y.; Rajasekaran, S.; Zhang, L.; Winnerl, S.; Schneider, H.; Schay, G.; Lorincz, I.; Rauscher, A. A.; Radu, I.; Mährlein, S.; Kim, T. H.; Lee, J. S.; Kampfrath, T.; Wall, S.; Heberle, J.; Malnasi-Csizmadia, A.; Steiger, A.; Müller, A. S.; Helm, M.; Schramm, U.; Cowan, T.; Michel, P.; Cavalleri, A.; Fisher, A. S.; Stojanovic, N.; Gensch, M.

    2016-01-01

    Ultrashort flashes of THz light with low photon energies of a few meV, but strong electric or magnetic field transients have recently been employed to prepare various fascinating nonequilibrium states in matter. Here we present a new class of sources based on superradiant enhancement of radiation from relativistic electron bunches in a compact electron accelerator that we believe will revolutionize experiments in this field. Our prototype source generates high-field THz pulses at unprecedented quasi-continuous-wave repetition rates up to the MHz regime. We demonstrate parameters that exceed state-of-the-art laser-based sources by more than 2 orders of magnitude. The peak fields and the repetition rates are highly scalable and once fully operational this type of sources will routinely provide 1 MV/cm electric fields and 0.3 T magnetic fields at repetition rates of few 100 kHz. We benchmark the unique properties by performing a resonant coherent THz control experiment with few 10 fs resolution. PMID:26924651

  10. Electron beam energy chirp control with a rectangular corrugated structure at the Linac Coherent Light Source

    DOE PAGES

    Zhang, Zhen; Bane, Karl; Ding, Yuantao; ...

    2015-01-30

    In this study, electron beam energy chirp is an important parameter that affects the bandwidth and performance of a linac-based, free-electron laser. In this paper we study the wakefields generated by a beam passing between at metallic plates with small corrugations, and then apply such a device as a passive dechirper for the Linac Coherent Light Source (LCLS) energy chirp control with a multi-GeV and femtosecond electron beam. Similar devices have been tested in several places at relatively low energies (~100 MeV) and with relatively long bunches (> 1ps). In the parameter regime of the LCLS dechirper, with the corrugationmore » size similar to the gap between the plates, the analytical solutions of the wakefields are no longer applicable, and we resort to a field matching program to obtain the wakes. Based on the numerical calculations, we fit the short-range, longitudinal wakes to simple formulas, valid over a large, useful parameter range. Finally, since the transverse wakefields - both dipole and quadrupole-are strong, we compute and include them in beam dynamics simulations to investigate the error tolerances when this device is introduced in the LCLS.« less

  11. Coherent Optical Control of Quantum Dots: Spin Qubits and Flying Qubits

    NASA Astrophysics Data System (ADS)

    Burgers, Alex

    2015-03-01

    Coherent control of solid-state qubits lies at the heart of most quantum information architectures. In quantum dots (QDs), optical fields are an attractive medium for qubit manipulation and readout. The entanglement between a QD spin qubit and an emitted photonic qubit allows for the transport of quantum information between distant quantum memories via decoherence resistant photon channels. I will present recent experimental work showing the entanglement between a single electron spin confined to an InAs QD and its spontaneously emitted photon. This entanglement is significant for the further development of quantum information technologies using QDs and forms the foundation of on-chip technologies using photonic crystal pathways. In addition, I will discuss on-going work on teleportation of information from a single photon generated in a spontaneous parametric down conversion (SPDC) process to a QD spin through intermediate interference between the SPDC photon and the dot's emitted photon. The ability to integrate two quantum information platforms is not only exciting in its own right, but this technique could allow for an entanglement swapping bridge between other matter-qubit (ions, NV centers, etc.) based quantum memories. This work is funded by NSF, ARO, AFOSR, ONR and DARPA.

  12. Doping-controlled Coherent Electron-Phonon Coupling in Vanadium Dioxide

    SciTech Connect

    Appavoo, Kannatassen; Wang, Bin; Nag, Joyeeta; Sfeir, Matthew Y.; Pantelides, Sokrates T.; Haglund, Richard F.

    2015-05-10

    Broadband femtosecond transient spectroscopy and density functional calculations reveal that substitutional tungsten doping of a VO2 film changes the coherent phonon response compared to the undoped film due to altered electronic and structural dynamics.

  13. Controlling Plasmon-Enhanced Fluorescence via Intersystem Crossing in Photoswitchable Molecules.

    PubMed

    Wang, Mingsong; Hartmann, Gregory; Wu, Zilong; Scarabelli, Leonardo; Rajeeva, Bharath Bangalore; Jarrett, Jeremy W; Perillo, Evan P; Dunn, Andrew K; Liz-Marzán, Luis M; Hwang, Gyeong S; Zheng, Yuebing

    2017-10-01

    By harnessing photoswitchable intersystem crossing (ISC) in spiropyran (SP) molecules, active control of plasmon-enhanced fluorescence in the hybrid systems of SP molecules and plasmonic nanostructures is achieved. Specifically, SP-derived merocyanine (MC) molecules formed by photochemical ring-opening reaction display efficient ISC due to their zwitterionic character. In contrast, ISC in quinoidal MC molecules formed by thermal ring-opening reaction is negligible. The high ISC rate can improve fluorescence quantum yield of the plasmon-modified spontaneous emission, only when the plasmonic electromagnetic field enhancement is sufficiently high. Along this line, extensive photomodulation of fluorescence is demonstrated by switching the ISC in MC molecules at Au nanoparticle aggregates, where strongly enhanced plasmonic hot spots exist. The ISC-mediated plasmon-enhanced fluorescence represents a new approach toward controlling the spontaneous emission of fluorophores near plasmonic nanostructures, which expands the applications of active molecular plasmonics in information processing, biosensing, and bioimaging. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Remote control of therapeutic T cells through a small molecule-gated chimeric receptor.

    PubMed

    Wu, Chia-Yung; Roybal, Kole T; Puchner, Elias M; Onuffer, James; Lim, Wendell A

    2015-10-16

    There is growing interest in using engineered cells as therapeutic agents. For example, synthetic chimeric antigen receptors (CARs) can redirect T cells to recognize and eliminate tumor cells expressing specific antigens. Despite promising clinical results, these engineered T cells can exhibit excessive activity that is difficult to control and can cause severe toxicity. We designed "ON-switch" CARs that enable small-molecule control over T cell therapeutic functions while still retaining antigen specificity. In these split receptors, antigen-binding and intracellular signaling components assemble only in the presence of a heterodimerizing small molecule. This titratable pharmacologic regulation could allow physicians to precisely control the timing, location, and dosage of T cell activity, thereby mitigating toxicity. This work illustrates the potential of combining cellular engineering with orthogonal chemical tools to yield safer therapeutic cells that tightly integrate cell-autonomous recognition and user control. Copyright © 2015, American Association for the Advancement of Science.

  15. Remote control of therapeutic T cells through a small molecule-gated chimeric receptor

    PubMed Central

    Wu, Chia-Yung; Roybal, Kole T.; Puchner, Elias M.; Onuffer, James; Lim, Wendell A.

    2016-01-01

    There is growing promise in using engineered cells as therapeutic agents. For example, synthetic Chimeric Antigen Receptors (CARs) can redirect T cells to recognize and eliminate tumor cells expressing specific antigens. Despite promising clinical results, excessive activity and poor control over such engineered T cells can cause severe toxicities. We present the design of “ON-switch” CARs that enable small molecule-control over T cell therapeutic functions, while still retaining antigen specificity. In these split receptors, antigen binding and intracellular signaling components only assemble in the presence of a heterodimerizing small molecule. This titratable pharmacologic regulation could allow physicians to precisely control the timing, location, and dosage of T cell activity, thereby mitigating toxicity. This work illustrates the potential of combining cellular engineering with orthogonal chemical tools to yield safer therapeutic cells that tightly integrate both cell autonomous recognition and user control. PMID:26405231

  16. Precisely Controlled 2D Free-Floating Nanosheets of Amphiphilic Molecules through Frame-Guided Assembly.

    PubMed

    Zhou, Chao; Zhang, Yiyang; Dong, Yuanchen; Wu, Fen; Wang, Dianming; Xin, Ling; Liu, Dongsheng

    2016-11-01

    2D assembly of amphiphilic molecules in aqueous solution is a challenging and intriguing topic as it is normally thermodynamically unfavorable. However, through frame-guided assembly strategy and using DNA origami as the frame, monodispersed and shape-defined nanosheets are prepared. As leading hydrophobic groups (LHGs) are anchored on the frames, amphiphilic molecules in aqueous solution are guided to assemble in the hydrophobic region. By adjusting the distribution of the LHGs, the size and shape of the assemblies can be controlled precisely.

  17. Active control on high-order coherence and statistic characterization on random phase fluctuation of two classical point sources

    PubMed Central

    Hong, Peilong; Li, Liming; Liu, Jianji; Zhang, Guoquan

    2016-01-01

    Young’s double-slit or two-beam interference is of fundamental importance to understand various interference effects, in which the stationary phase difference between two beams plays the key role in the first-order coherence. Different from the case of first-order coherence, in the high-order optical coherence the statistic behavior of the optical phase will play the key role. In this article, by employing a fundamental interfering configuration with two classical point sources, we showed that the high- order optical coherence between two classical point sources can be actively designed by controlling the statistic behavior of the relative phase difference between two point sources. Synchronous position Nth-order subwavelength interference with an effective wavelength of λ/M was demonstrated, in which λ is the wavelength of point sources and M is an integer not larger than N. Interestingly, we found that the synchronous position Nth-order interference fringe fingerprints the statistic trace of random phase fluctuation of two classical point sources, therefore, it provides an effective way to characterize the statistic properties of phase fluctuation for incoherent light sources. PMID:27021589

  18. Sub-Riemannian geometry and time optimal control of three spin systems: Quantum gates and coherence transfer

    NASA Astrophysics Data System (ADS)

    Khaneja, Navin; Glaser, Steffen J.; Brockett, Roger

    2002-03-01

    Radio-frequency pulses are used in nuclear-magnetic-resonance spectroscopy to produce unitary transfer of states. Pulse sequences that accomplish a desired transfer should be as short as possible in order to minimize the effects of relaxation, and to optimize the sensitivity of the experiments. Many coherence-transfer experiments in NMR, involving a network of coupled spins, use temporary spin decoupling to produce desired effective Hamiltonians. In this paper, we demonstrate that significant time can be saved in producing an effective Hamiltonian if spin decoupling is avoided. We provide time-optimal pulse sequences for producing an important class of effective Hamiltonians in three-spin networks. These effective Hamiltonians are useful for coherence-transfer experiments in three-spin systems and implementation of indirect swap and Λ2(U) gates in the context of NMR quantum computing. It is shown that computing these time-optimal pulses can be reduced to geometric problems that involve computing sub-Riemannian geodesics. Using these geometric ideas, explicit expressions for the minimum time required for producing these effective Hamiltonians, transfer of coherence, and implementation of indirect swap gates, in a three-spin network are derived (Theorems 1 and 2). It is demonstrated that geometric control techniques provide a systematic way of finding time-optimal pulse sequences for transferring coherence and synthesizing unitary transformations in quantum networks, with considerable time savings (e.g., 42.3% for constructing indirect swap gates).

  19. Toward Controlled Hierarchical Heterogeneities in Giant Molecules with Precisely Arranged Nano Building Blocks

    PubMed Central

    2016-01-01

    Herein we introduce a unique synthetic methodology to prepare a library of giant molecules with multiple, precisely arranged nano building blocks, and illustrate the influence of minute structural differences on their self-assembly behaviors. The T8 polyhedral oligomeric silsesquioxane (POSS) nanoparticles are orthogonally functionalized and sequentially attached onto the end of a hydrophobic polymer chain in either linear or branched configuration. The heterogeneity of primary chemical structure in terms of composition, surface functionality, sequence, and topology can be precisely controlled and is reflected in the self-assembled supramolecular structures of these giant molecules in the condensed state. This strategy offers promising opportunities to manipulate the hierarchical heterogeneities of giant molecules via precise and modular assemblies of various nano building blocks. PMID:27163025

  20. Reversible single spin control of individual magnetic molecule by hydrogen atom adsorption.

    PubMed

    Liu, Liwei; Yang, Kai; Jiang, Yuhang; Song, Boqun; Xiao, Wende; Li, Linfei; Zhou, Haitao; Wang, Yeliang; Du, Shixuan; Ouyang, Min; Hofer, Werner A; Castro Neto, Antonio H; Gao, Hong-Jun

    2013-01-01

    The reversible control of a single spin of an atom or a molecule is of great interest in Kondo physics and a potential application in spin based electronics. Here we demonstrate that the Kondo resonance of manganese phthalocyanine molecules on a Au(111) substrate have been reversibly switched off and on via a robust route through attachment and detachment of single hydrogen atom to the magnetic core of the molecule. As further revealed by density functional theory calculations, even though the total number of electrons of the Mn ion remains almost the same in the process, gaining one single hydrogen atom leads to redistribution of charges within 3d orbitals with a reduction of the molecular spin state from S = 3/2 to S = 1 that directly contributes to the Kondo resonance disappearance. This process is reversed by a local voltage pulse or thermal annealing to desorb the hydrogen atom.

  1. Dynamic acousto-optic control of a strongly coupled photonic molecule

    PubMed Central

    Kapfinger, Stephan; Reichert, Thorsten; Lichtmannecker, Stefan; Müller, Kai; Finley, Jonathan J.; Wixforth, Achim; Kaniber, Michael; Krenner, Hubert J.

    2015-01-01

    Strongly confined photonic modes can couple to quantum emitters and mechanical excitations. To harness the full potential in quantum photonic circuits, interactions between different constituents have to be precisely and dynamically controlled. Here, a prototypical coupled element, a photonic molecule defined in a photonic crystal membrane, is controlled by a radio frequency surface acoustic wave. The sound wave is tailored to deliberately switch on and off the bond of the photonic molecule on sub-nanosecond timescales. In time-resolved experiments, the acousto-optically controllable coupling is directly observed as clear anticrossings between the two nanophotonic modes. The coupling strength is determined directly from the experimental data. Both the time dependence of the tuning and the inter-cavity coupling strength are found to be in excellent agreement with numerical calculations. The demonstrated mechanical technique can be directly applied for dynamic quantum gate operations in state-of-the-art-coupled nanophotonic, quantum cavity electrodynamic and optomechanical systems. PMID:26436203

  2. Single molecule dynamics at a mechanically controllable break junction in solution at room temperature.

    PubMed

    Konishi, Tatsuya; Kiguchi, Manabu; Takase, Mai; Nagasawa, Fumika; Nabika, Hideki; Ikeda, Katsuyoshi; Uosaki, Kohei; Ueno, Kosei; Misawa, Hiroaki; Murakoshi, Kei

    2013-01-23

    The in situ observation of geometrical and electronic structural dynamics of a single molecule junction is critically important in order to further progress in molecular electronics. Observations of single molecular junctions are difficult, however, because of sensitivity limits. Here, we report surface-enhanced Raman scattering (SERS) of a single 4,4'-bipyridine molecule under conditions of in situ current flow in a nanogap, by using nano-fabricated, mechanically controllable break junction (MCBJ) electrodes. When adsorbed at room temperature on metal nanoelectrodes in solution to form a single molecule junction, statistical analysis showed that nontotally symmetric b(1) and b(2) modes of 4,4'-bipyridine were strongly enhanced relative to observations of the same modes in solid or aqueous solutions. Significant changes in SERS intensity, energy (wavenumber), and selectivity of Raman vibrational bands that are coincident with current fluctuations provide information on distinct states of electronic and geometrical structure of the single molecule junction, even under large thermal fluctuations occurring at room temperature. We observed the dynamics of 4,4'-bipyridine motion between vertical and tilting configurations in the Au nanogap via b(1) and b(2) mode switching. A slight increase in the tilting angle of the molecule was also observed by noting the increase in the energies of Raman modes and the decrease in conductance of the molecular junction.

  3. Shear-induced intracellular loading of cells with molecules by controlled microfluidics

    PubMed Central

    Hallow, Daniel M.; Seeger, Richard A.; Kamaev, Pavel P.; Prado, Gustavo R.; LaPlaca, Michelle C.; Prausnitz, Mark R.

    2010-01-01

    This study tested the hypothesis that controlled flow through microchannels can cause shear-induced intracellular loading of cells with molecules. The overall goal was to design a simple device to expose cells to fluid shear stress and thereby increase plasma membrane permeability. DU145 prostate cancer cells were exposed to fluid shear stress in the presence of fluorescent cell-impermeant molecules by using a cone-and-plate shearing device or high-velocity flow through microchannels. Using a syringe pump, cell suspensions were flowed through microchannels of 50 – 300 μm diameter drilled through Mylar® sheets using an excimer laser. As quantified by flow cytometry, intracellular uptake and loss of viability correlated with the average shear stress. Optimal results were observed when exposing the cells to high shear stress for short durations in conical channels, which yielded uptake to over one third of cells while maintaining viability at approximately 80%. This method was capable of loading cells with molecules including calcein (0.62 kDa), large molecule weight dextrans (150 - 2000 kDa), and bovine serum albumin (66 kDa). These results supported the hypothesis that shear-induced intracellular uptake could be generated by flow of cell suspensions through microchannels and further led to the design of a simple, inexpensive, and effective device to deliver molecules into cells. Such a device could benefit biological research and the biotechnology industry. PMID:17879304

  4. Controlling orbital-selective Kondo effects in a single molecule through coordination chemistry

    SciTech Connect

    Tsukahara, Noriyuki; Kawai, Maki; Takagi, Noriaki; Minamitani, Emi; Kim, Yousoo

    2014-08-07

    Iron(II) phthalocyanine (FePc) molecule causes novel Kondo effects derived from the unique electronic structure of multi-spins and multi-orbitals when attached to Au(111). Two unpaired electrons in the d{sub z}{sup 2} and the degenerate dπ orbitals are screened stepwise, resulting in spin and spin+orbital Kondo effects, respectively. We investigated the impact on the Kondo effects of the coordination of CO and NO molecules to the Fe{sup 2+} ion as chemical stimuli by using scanning tunneling microscopy (STM) and density functional theory calculations. The impacts of the two diatomic molecules are different from each other as a result of the different electronic configurations. The coordination of CO converts the spin state from triplet to singlet, and then the Kondo effects completely disappear. In contrast, an unpaired electron survives in the molecular orbital composed of Fe d{sub z}{sup 2} and NO 5σ and 2π* orbitals for the coordination of NO, causing a sharp Kondo resonance. The isotropic magnetic response of the peak indicates the origin is the spin Kondo effect. The diatomic molecules attached to the Fe{sup 2+} ion were easily detached by applying a pulsed voltage at the STM junction. These results demonstrate that the single molecule chemistry enables us to switch and control the spin and the many-body quantum states reversibly.

  5. Distinctive behaviour of live biopsy-derived carcinoma cells unveiled using coherence-controlled holographic microscopy

    PubMed Central

    2017-01-01

    Head and neck squamous cell carcinoma is one of the most aggressive tumours and is typically diagnosed too late. Late diagnosis requires an urgent decision on an effective therapy. An individualized test of chemosensitivity should quickly indicate the suitability of chemotherapy and radiotherapy. No ex vivo chemosensitivity assessment developed thus far has become a part of general clinical practice. Therefore, we attempted to explore the new technique of coherence-controlled holographic microscopy to investigate the motility and growth of live cells from a head and neck squamous cell carcinoma biopsy. We expected to reveal behavioural patterns characteristic for malignant cells that can be used to imrove future predictive evaluation of chemotherapy. We managed to cultivate primary SACR2 carcinoma cells from head and neck squamous cell carcinoma biopsy verified through histopathology. The cells grew as a cohesive sheet of suspected carcinoma origin, and western blots showed positivity for the tumour marker p63 confirming cancerous origin. Unlike the roundish colonies of the established FaDu carcinoma cell line, the SACR2 cells formed irregularly shaped colonies, eliciting the impression of the collective invasion of carcinoma cells. Time-lapse recordings of the cohesive sheet activity revealed the rapid migration and high plasticity of these epithelial-like cells. Individual cells frequently abandoned the swiftly migrating crowd by moving aside and crawling faster. The increasing mass of fast migrating epithelial-like cells before and after mitosis confirmed the continuation of the cell cycle. In immunofluorescence, analogously shaped cells expressed the p63 tumour marker, considered proof of their origin from a carcinoma. These behavioural traits indicate the feasible identification of carcinoma cells in culture according to the proposed concept of the carcinoma cell dynamic phenotype. If further developed, this approach could later serve in a new functional

  6. Near-infrared resonance-mediated chirp control of a coherently generated broadband deep-ultraviolet spectrum

    SciTech Connect

    Rybak, Leonid; Chuntonov, Lev; Gandman, Andrey; Shakour, Naser; Amitay, Zohar

    2011-09-15

    We investigate the use of shaped near-infrared (NIR) femtosecond pulses to control the generation of coherent broadband deep-ultraviolet (DUV) radiation in an atomic resonance-mediated (2+1) three-photon excitation to a broad far-from-resonance continuum. Previously, we have shown control over the total emitted DUV yield. Here, we experimentally demonstrate phase control over the spectral characteristics (central frequency and bandwidth) of the emitted broadband DUV radiation. It is achieved by tuning the linear chirp applied to the exciting NIR femtosecond pulse. The study is conducted with Na vapor.

  7. Quantum coherence controls the charge separation in a prototypical artificial light-harvesting system

    PubMed Central

    Andrea Rozzi, Carlo; Maria Falke, Sarah; Spallanzani, Nicola; Rubio, Angel; Molinari, Elisa; Brida, Daniele; Maiuri, Margherita; Cerullo, Giulio; Schramm, Heiko; Christoffers, Jens; Lienau, Christoph

    2013-01-01

    The efficient conversion of light into electricity or chemical fuels is a fundamental challenge. In artificial photosynthetic and photovoltaic devices, this conversion is generally thought to happen on ultrafast, femto-to-picosecond timescales and to involve an incoherent electron transfer process. In some biological systems, however, there is growing evidence that the coherent motion of electronic wavepackets is an essential primary step, raising questions about the role of quantum coherence in artificial devices. Here we investigate the primary charge-transfer process in a supramolecular triad, a prototypical artificial reaction centre. Combining high time-resolution femtosecond spectroscopy and time-dependent density functional theory, we provide compelling evidence that the driving mechanism of the photoinduced current generation cycle is a correlated wavelike motion of electrons and nuclei on a timescale of few tens of femtoseconds. We highlight the fundamental role of the interface between chromophore and charge acceptor in triggering the coherent wavelike electron-hole splitting. PMID:23511467

  8. Quantum coherence controls the charge separation in a prototypical artificial light-harvesting system.

    PubMed

    Rozzi, Carlo Andrea; Falke, Sarah Maria; Spallanzani, Nicola; Rubio, Angel; Molinari, Elisa; Brida, Daniele; Maiuri, Margherita; Cerullo, Giulio; Schramm, Heiko; Christoffers, Jens; Lienau, Christoph

    2013-01-01

    The efficient conversion of light into electricity or chemical fuels is a fundamental challenge. In artificial photosynthetic and photovoltaic devices, this conversion is generally thought to happen on ultrafast, femto-to-picosecond timescales and to involve an incoherent electron transfer process. In some biological systems, however, there is growing evidence that the coherent motion of electronic wavepackets is an essential primary step, raising questions about the role of quantum coherence in artificial devices. Here we investigate the primary charge-transfer process in a supramolecular triad, a prototypical artificial reaction centre. Combining high time-resolution femtosecond spectroscopy and time-dependent density functional theory, we provide compelling evidence that the driving mechanism of the photoinduced current generation cycle is a correlated wavelike motion of electrons and nuclei on a timescale of few tens of femtoseconds. We highlight the fundamental role of the interface between chromophore and charge acceptor in triggering the coherent wavelike electron-hole splitting.

  9. Control of Biofilms with the Fatty Acid Signaling Molecule cis-2-Decenoic Acid

    PubMed Central

    Marques, Cláudia N. H.; Davies, David G.; Sauer, Karin

    2015-01-01

    Biofilms are complex communities of microorganisms in organized structures attached to surfaces. Importantly, biofilms are a major cause of bacterial infections in humans, and remain one of the most significant challenges to modern medical practice. Unfortunately, conventional therapies have shown to be inadequate in the treatment of most chronic biofilm infections based on the extraordinary innate tolerance of biofilms to antibiotics. Antagonists of quorum sensing signaling molecules have been used as means to control biofilms. QS and other cell-cell communication molecules are able to revert biofilm tolerance, prevent biofilm formation and disrupt fully developed biofilms, albeit with restricted effectiveness. Recently however, it has been demonstrated that Pseudomonas aeruginosa produces a small messenger molecule cis-2-decenoic acid (cis-DA) that shows significant promise as an effective adjunctive to antimicrobial treatment of biofilms. This molecule is responsible for induction of the native biofilm dispersion response in a range of Gram-negative and Gram-positive bacteria and in yeast, and has been shown to reverse persistence, increase microbial metabolic activity and significantly enhance the cidal effects of conventional antimicrobial agents. In this manuscript, the use of cis-2-decenoic acid as a novel agent for biofilm control is discussed. Stimulating the biofilm dispersion response as a novel antimicrobial strategy holds significant promise for enhanced treatment of infections and in the prevention of biofilm formation. PMID:26610524

  10. Virtual reality visual feedback for hand-controlled scanning probe microscopy manipulation of single molecules.

    PubMed

    Leinen, Philipp; Green, Matthew F B; Esat, Taner; Wagner, Christian; Tautz, F Stefan; Temirov, Ruslan

    2015-01-01

    Controlled manipulation of single molecules is an important step towards the fabrication of single molecule devices and nanoscale molecular machines. Currently, scanning probe microscopy (SPM) is the only technique that facilitates direct imaging and manipulations of nanometer-sized molecular compounds on surfaces. The technique of hand-controlled manipulation (HCM) introduced recently in Beilstein J. Nanotechnol. 2014, 5, 1926-1932 simplifies the identification of successful manipulation protocols in situations when the interaction pattern of the manipulated molecule with its environment is not fully known. Here we present a further technical development that substantially improves the effectiveness of HCM. By adding Oculus Rift virtual reality goggles to our HCM set-up we provide the experimentalist with 3D visual feedback that displays the currently executed trajectory and the position of the SPM tip during manipulation in real time, while simultaneously plotting the experimentally measured frequency shift (Δf) of the non-contact atomic force microscope (NC-AFM) tuning fork sensor as well as the magnitude of the electric current (I) flowing between the tip and the surface. The advantages of the set-up are demonstrated by applying it to the model problem of the extraction of an individual PTCDA molecule from its hydrogen-bonded monolayer grown on Ag(111) surface.

  11. Production of cold formaldehyde molecules for study and control of chemical reaction.

    SciTech Connect

    Taatjes, Craig A.; Bochinski, J. R.; Bohn, John L.; Ye, Jun; Lewandowski, H. J.; Sawyer, Brian C.; Ticknor, Christopher; Hudson, Eric R.

    2005-08-01

    We propose a method for controlling a class of low temperature chemical reactions. Specifically, we show the hydrogen abstraction channel in the reaction of formaldehyde (H{sub 2}CO) and the hydroxyl radical (OH) can be controlled through either the molecular state or an external electric field. We also outline experiments for investigating and demonstrating control over this important reaction. To this end, we report the first Stark deceleration of H{sub 2}CO. We have decelerated a molecular beam of H{sub 2}CO essentially to rest, producing molecules at 100 mK with a density of {approx} 10{sup 6} cm{sup -3}.

  12. Production of cold formaldehyde molecules for study and control of chemical reaction dynamics with hydroxyl radicals

    SciTech Connect

    Hudson, Eric R.; Ticknor, Christopher; Sawyer, Brian C.; Taatjes, Craig A.; Lewandowski, H. J.; Bochinski, J. R.; Bohn, J. L.; Ye Jun

    2006-06-15

    We propose a method for controlling a class of low temperature chemical reactions. Specifically, we show the hydrogen abstraction channel in the reaction of formaldehyde (H{sub 2}CO) and the hydroxyl radical (OH) can be controlled through either the molecular state or an external electric field. We also outline experiments for investigating and demonstrating control over this important reaction. To this end, we report the first Stark deceleration of H{sub 2}CO. We have decelerated a molecular beam of H{sub 2}CO essentially to rest, producing molecules at 100 mK with a density of {approx}10{sup 6} cm{sup -3}.

  13. Controlling stimulated coherent spectroscopy and microscopy by a position-dependent phase

    NASA Astrophysics Data System (ADS)

    Chung, Chao-Yu; Hsu, Julie; Mukamel, Shaul; Potma, Eric O.

    2013-03-01

    We study the role of geometry-dependent phase shifts of the optical electric field in stimulated coherent spectroscopy, a special class of heterodyne optical spectroscopy techniques. We generalize the theoretical description of stimulated spectroscopy to include spatial phase effects, and study the measured material response for several representative excitation and detection configurations. Using stimulated Raman scattering microscopy as an example, we show that different components of the material response are measured by varying the position of the object in focus. We discuss the implications of the position-dependent phase in stimulated coherent microscopy and point out a detection configuration in which its effects are minimized.

  14. Evaluation of a commercially available synthetic RNA lipid enveloped control molecule.

    PubMed

    Maloney, Samuel; Francis, Fleur; Bletchly, Cheryl; Norton, Robert

    2015-01-01

    Detection of viral ribonucleic acid with RT PCR is a useful tool for viral detection. One of the drawbacks of this technique is the difficulty in including an internal control molecule to ensure the validity of the extraction and amplification process. In this study the potential usefulness of a novel lipid enveloped commercially available RNA control molecule is investigated. Initial optimisation of the detection assay was performed by amplification of IC (internal control) spiked into PCR water. Thirty-two clinical respiratory samples were spiked with the IC before and after extraction and RT PCR was then performed. Inefficient extraction was simulated. Inhibition of the RT PCR was achieved by serial dilution of heparin sulfate into samples post extraction. No Targets that matched the IC (Internal Control) primers were identified in 32 extracted sputum samples as determined by the absence of non specific amplification curves. The unextracted IC had an increased CT (cycle threshold) value compared to IC that had been extracted. Inefficient extraction was detected by an increased CT. Increasing concentrations of heparin inhibited the PCR in a predictable fashion. The Bioline IC molecule provides a stable RNA IC that has acceptable performance characteristics. Copyright © 2014 Elsevier B.V. All rights reserved.

  15. Rational design of a small molecule-responsive intramer controlling transgene expression in mammalian cells

    PubMed Central

    Ausländer, David; Wieland, Markus; Ausländer, Simon; Tigges, Marcel; Fussenegger, Martin

    2011-01-01

    Aptamers binding proteins or small molecules have been shown to be versatile and powerful building blocks for the construction of artificial genetic switches. In this study, we present a novel aptamer-based construct regulating the Tet Off system in a tetracycline-independent manner thus achieving control of transgene expression. For this purpose, a TetR protein-inhibiting aptamer was engineered for use in mammalian cells, enabling the RNA-responsive control of the tetracycline-dependent transactivator (tTA). By rationally attaching the theophylline aptamer as a sensor, the inhibitory TetR aptamer and thus tTA activity became dependent on the ligand of the sensor aptamer. Addition of the small molecule theophylline resulted in enhanced binding to the corresponding protein in vitro and in inhibition of reporter gene expression in mammalian cell lines. By using aptamers as adaptors in order to control protein activity by a predetermined small molecule, we present a simple and straightforward approach for future applications in the field of Chemical Biology. Moreover, aptamer-based control of the widely used Tet system introduces a new layer of regulation thereby facilitating the construction of more complex gene networks. PMID:21984476

  16. Quantum controlled fusion

    NASA Astrophysics Data System (ADS)

    Berrios, Eduardo; Gruebele, Martin; Wolynes, Peter G.

    2017-09-01

    Quantum-controlled motion of nuclei, starting from the nanometer-size ground state of a molecule, can potentially overcome some of the difficulties of thermonuclear fusion by compression of a fuel pellet or in a bulk plasma. Coherent laser control can manipulate nuclear motion precisely, achieving large phase space densities for the colliding nuclei. We combine quantum wavepacket propagation of D and T nuclei in a field-bound molecule with coherent control by a shaped laser pulse to demonstrate enhancement of nuclear collision rates. Atom-smashers powered by coherent control may become laboratory sources of particle bursts, and even assist muonic fusion.

  17. Coherent control and detection of spin qubits in semiconductor with magnetic field engineering

    NASA Astrophysics Data System (ADS)

    Tokura, Yasuhiro

    2012-02-01

    Electrical control and detection of the spin qubits in semiconductor quantum dots (QDs) are among the major rapidly progressing fields for possible implementation of scalable quantum information processing. Coherent control of one-[1-3] and two-[4,5] spin qubits by electrical means had been demonstrated with various approaches. We have used an engineered magnetic field structure realized with proximal micro-magnets to transduce the spin and charge degrees of freedom and to selectively address one of the two spins [3]. We have demonstrated an all-electrical two-qubit gate consisting of single-spin rotations and interdot spin exchange in double QDs. A partially entangled output state is obtained by the application of the two-qubit gate to an initial, uncorrelated state. Our calculations taking into account of the nuclear spin fluctuation show the degree of entanglement. Non-uniform magnetic field also enables spin selective photon-assisted tunneling in double QDs, which then constitutes non-demolition spin read-out system in combination with a near-by charge detector [6]. [4pt] In collaboration with R. Brunner, Inst. of Phys., Montanuniversitaet Leoben, 8700, Austria, M. Pioro-Ladrière, D'ep. de Phys., Universit'e de Sherbrooke, Sherbrooke, Qu'ebec, J1K-2R1, Canada, T. Kubo, Y. -S. Shin, T. Obata, and S. Tarucha, ICORP-JST and Dep. of Appl. Phys., Univ. of Tokyo, Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan.[4pt] [1] F. H. Koppens, et al., Nature 442, 766 (2006).[0pt] [2] K. C. Nowack, et al., Science 318, 1430 (2007).[0pt] [3] M. Pioro-Ladrière, et al., Nature Physics 4, 776 (2008).[0pt] [4] J. R. Petta, et al., Science 309, 2180 (2005).[0pt] [5] R. Brunner, et al., Phys. Rev. Lett. 107, 146801 (2011).[0pt] [6] Y. -S. Shin, et al., Phys. Rev. Lett. 104, 046802 (2010).

  18. Real-time control of the energy landscape by force directs the folding of RNA molecules

    PubMed Central

    Li, Pan T. X.; Bustamante, Carlos; Tinoco, Ignacio

    2007-01-01

    The rugged folding-energy landscapes of RNAs often display many competing minima. How do RNAs discriminate among competing conformations in their search for the native state? By using optical tweezers, we show that the folding-energy landscape can be manipulated to control the fate of an RNA: individual RNA molecules can be induced into either native or misfolding pathways by modulating the relaxation rate of applied force and even be redirected during the folding process to switch from misfolding to native folding pathways. Controlling folding pathways at the single-molecule level provides a way to survey the manifold of folding trajectories and intermediates, a capability that previously was available only to theoretical studies. PMID:17438300

  19. Coherent control of ultracold {sup 85}Rb trap-loss collisions with nonlinearly frequency-chirped light

    SciTech Connect

    Pechkis, J. A.; Carini, J. L.; Rogers, C. E. III; Gould, P. L.; Kallush, S.; Kosloff, R.

    2011-06-15

    We present results on coherent control of ultracold trap-loss collisions using 40-ns pulses of nonlinearly frequency-chirped light. The chirps, either positive or negative, sweep {approx}1 GHz in 100 ns and are centered at various detunings below the D{sub 2} line of {sup 85}Rb. At each center detuning, we compare the collisional rate constant {beta} for chirps that are linear in time, concave-down, and concave-up. For positive chirps, we find that {beta} generally depends very little on the shape of the chirp. For negative chirps, however, we find that {beta} can be enhanced by up to 50(20)% for the case of the concave-down shape. This occurs at detunings where the evolution of the wave packet is expected to be coherent. An enhancement at these detunings is also seen in quantum-mechanical simulations of the collisional process.

  20. Site-controlled quantum dots coupled to a photonic crystal molecule

    SciTech Connect

    Rigal, B.; Jarlov, C.; Gallo, P.; Dwir, B.; Rudra, A.; Calic, M.; Kapon, E.

    2015-10-05

    Two site-controlled quantum dots (QDs) were integrated in a photonic crystal molecule (PCM) formed by L3 nanocavities. A statistical analysis of the coupled cavity modes demonstrated the formation of bonding and anti-bonding delocalized PCM states. Excitonic transitions belonging to each QD were identified by scanning micro-photoluminescence spectroscopy. Co-polarization of the QDs photoluminescence with the coupled cavity modes provides evidence for the simultaneous coupling of two spatially separated QDs to the same PCM mode.

  1. A gate controlled conjugated single molecule diode: Its rectification could be reversed

    NASA Astrophysics Data System (ADS)

    Zhang, Qun

    2014-10-01

    A gate controlled Au/diphenyldipyrimidinyl/Au single molecule diode is simulated by a tight-binding Hamiltonian combined with Green's Function and transport methods. After calculating a number of electronic transport characteristics under various gate voltages, a clear modulation by gate is got and when the positive voltage is high enough, the rectification could be reversed. This is advisable for the designing and building future molecular logic devices and integrated circuits.

  2. Controlled Assembly of Biocompatible Metallic Nanoaggregates Using a Small Molecule Crosslinker

    PubMed Central

    Van Haute, Desiree; Longmate, Julia M.; Berlin, Jacob M.

    2015-01-01

    By introducing a capping step and controlling reaction parameters, the assembly of metallic nanoparticle aggregates can be achieved using a small molecule crosslinker. Aggregates can be assembled from particles of varied size and composition and the size of the aggregates can be systematically adjusted. Following cell uptake of 60 nm aggregates, the aggregates are stable and non-toxic to macrophage cells up to 55mM Au. PMID:26208123

  3. Optimal control of multiphoton ionization of Rb2 molecules in a magneto-optical trap

    NASA Astrophysics Data System (ADS)

    Weise, Fabian; Birkner, Sascha; Merli, Andrea; Weber, Stefan M.; Sauer, Franziska; Wöste, Ludger; Lindinger, Albrecht; Salzmann, Wenzel; Mullins, Terence G.; Eng, Judith; Albert, Magnus; Wester, Roland; Weidemüller, Matthias

    2007-12-01

    We present optimal control, using femtosecond laser pulses in a closed-loop experiment, of the ionization process of ultracold rubidium molecules formed in a magneto-optical trap. The resulting spectrum of the optimally shaped pulse exhibits two frequency bands, which drive a resonantly enhanced three-photon ionization. The obtained data reveals the ionization process where only the electronic states corresponding to the 5s5d -asymptote are utilized for the second excitation step.

  4. Decrease of Prefrontal-Posterior EEG Coherence: Loose Control during Social-Emotional Stimulation

    ERIC Educational Resources Information Center

    Reiser, Eva M.; Schulter, Gunter; Weiss, Elisabeth M.; Fink, Andreas; Rominger, Christian; Papousek, Ilona

    2012-01-01

    In two experiments we aimed to investigate if individual differences in state-dependent decreases or increases of EEG coherence between prefrontal and posterior cortical regions may be indicative of a mechanism modulating the impact social-emotional information has on an individual. Two independent samples were exposed to an emotional stimulation…

  5. Time-delayed feedback control of coherence resonance near subcritical Hopf bifurcation: Theory versus experiment

    SciTech Connect

    Semenov, Vladimir; Feoktistov, Alexey; Vadivasova, Tatyana; Schöll, Eckehard Zakharova, Anna

    2015-03-15

    Using the model of a generalized Van der Pol oscillator in the regime of subcritical Hopf bifurcation, we investigate the influence of time delay on noise-induced oscillations. It is shown that for appropriate choices of time delay, either suppression or enhancement of coherence resonance can be achieved. Analytical calculations are combined with numerical simulations and experiments on an electronic circuit.

  6. Decrease of Prefrontal-Posterior EEG Coherence: Loose Control during Social-Emotional Stimulation

    ERIC Educational Resources Information Center

    Reiser, Eva M.; Schulter, Gunter; Weiss, Elisabeth M.; Fink, Andreas; Rominger, Christian; Papousek, Ilona

    2012-01-01

    In two experiments we aimed to investigate if individual differences in state-dependent decreases or increases of EEG coherence between prefrontal and posterior cortical regions may be indicative of a mechanism modulating the impact social-emotional information has on an individual. Two independent samples were exposed to an emotional stimulation…

  7. Yoctowells as a simple model system for the encapsulation and controlled release of bioactive molecules

    PubMed Central

    Bhosale, Sheshanath V.; Bhosale, Sidhanath V.

    2013-01-01

    The development of nanosized drug delivery systems to transport drugs to target cells, are promising tools to improve the drug therapeutic index. Transport systems should have a simple design to control the release of loaded drug to the target areas, thereby increasing concentration and prolonging retention. Herein, we demonstrate the use of yoctoliter wells (1 yL = 10−24 L) as simple model systems for the encapsulation and release of biologically active molecules, by manipulating pH. The drug molecule employed here is doxorubicin, which diffuses into the bottom of yoctowells from a bulk solution at pH 7. Capping of the yoctowells is achieved by addition of an anionic-porphyrin by electrostatic interaction. Furthermore, controlled release of the Doxorubcin and capping agent from the yoctowells is achieved by pH control. The effectiveness of the sustain release of the bioactive molecule from yoctowells, provides potential for development of a new generation of drug-delivery system for practical application. PMID:23760359

  8. Frequency stabilization, tuning, and spatial mode control of terahertz quantum cascade lasers for coherent transceiver applications

    NASA Astrophysics Data System (ADS)

    Danylov, Andriy

    THz quantum cascade lasers (TQCLs) first demonstrated in 2002 are a promising source of THz coherent radiation for use as both transmitters and local oscillators in coherent heterodyne detection systems. However, present TQCLs have deficiencies which include lack of frequency tunability, as well as inadequate spatial and temporal coherence. In this thesis we have addressed these issues to demonstrate an improved 2.408 TQCL which operated as a transmitter in a coherent heterodyne detection imaging system. The 2.408 THz QCL used in this thesis was grown and fabricated by the Photonics Center (University of Massachusetts Lowell). First, we showed that a short hollow Pyrex tube can act as a dielectric waveguide and transform the multimode, highly diverging TQCL beam into the lowest order dielectric waveguide hybrid mode, EH11, which then couples efficiently to the free-space Gaussian mode, TEMo0. This simple approach should enable TQCLs to be employed in applications where a spatially coherent beam is required. Next, the tunability problem was addressed. A compact, tunable, narrowband terahertz source was demonstrated by mixing a single longitudinal mode, 2.408 THz, free running quantum cascade laser with a 2-20 GHz microwave sweeper in a corner-cube-mounted Schottky diode (SD). The sideband spectra were characterized with a Fourier transform spectrometer, and the radiation was tuned through several D2O rotational transitions to estimate the longer term (t ≥ several seconds) bandwidth of the source. A spectral resolution of 2 MHz in the CW mode was observed. The temporal coherence of the TQCL was improved by assembling a simple analog locking circuit, which stabilizes the beat signal between the TQCL and a 2.40976 THz CO2 optically pumped molecular laser (OPL) line to 4 kHz full width at half maximum (FWHM). This is approximately a tenth of the observed long-term (t ˜ sec) linewidth of the OPL showing that the feedback loop corrects for much of the mechanical and

  9. Coherent Electronic Wave Packet Motion in C60 Controlled by the Waveform and Polarization of Few-Cycle Laser Fields

    NASA Astrophysics Data System (ADS)

    Li, H.; Mignolet, B.; Wachter, G.; Skruszewicz, S.; Zherebtsov, S.; Süßmann, F.; Kessel, A.; Trushin, S. A.; Kling, Nora G.; Kübel, M.; Ahn, B.; Kim, D.; Ben-Itzhak, I.; Cocke, C. L.; Fennel, T.; Tiggesbäumker, J.; Meiwes-Broer, K.-H.; Lemell, C.; Burgdörfer, J.; Levine, R. D.; Remacle, F.; Kling, M. F.

    2015-03-01

    Strong laser fields can be used to trigger an ultrafast molecular response that involves electronic excitation and ionization dynamics. Here, we report on the experimental control of the spatial localization of the electronic excitation in the C60 fullerene exerted by an intense few-cycle (4 fs) pulse at 720 nm. The control is achieved by tailoring the carrier-envelope phase and the polarization of the laser pulse. We find that the maxima and minima of the photoemission-asymmetry parameter along the laser-polarization axis are synchronized with the localization of the coherent electronic wave packet at around the time of ionization.

  10. Cyclopentadithiophene organic core in small molecule organic solar cells: morphological control of carrier recombination.

    PubMed

    Domínguez, Rocío; Montcada, Núria F; de la Cruz, Pilar; Palomares, Emilio; Langa, Fernando

    2017-02-01

    Two new planar and symmetrical A-D-A (electron acceptor-electron donor-electron acceptor) small molecules based on a commercial cyclopentadithiophene derivative have been synthesized for solution processed small molecule organic solar cells. The aim was to synthesise the molecules to be energetically identical (similar HOMO-LUMO energy levels) in order to assign the differences observed to changes in the film morphology or to differences in the interfacial recombination kinetics or both. Devices were electrically characterized under one sun simulated (1.5 AM G) conditions by determining current-voltage curves, light harvesting efficiencies and external quantum efficiencies. Moreover, time-resolved photo-induced techniques such as photo-induced charge extraction and photo-induced transient photo-voltage were also performed. The results demonstrate that, despite having the same core, i.e. cyclopentadithiophene, the use of one hexyl chain instead of two in the organic molecule leads to a greater control of the molecular ordering using solvent vapour annealing techniques and also to better solar cell efficiency.

  11. A dual small-molecule rheostat for precise control of protein concentration in Mammalian cells.

    PubMed

    Lin, Yu Hsuan; Pratt, Matthew R

    2014-04-14

    One of the most successful strategies for controlling protein concentrations in living cells relies on protein destabilization domains (DD). Under normal conditions, a DD will be rapidly degraded by the proteasome. However, the same DD can be stabilized or "shielded" in a stoichiometric complex with a small molecule, enabling dose-dependent control of its concentration. This process has been exploited by several labs to post-translationally control the expression levels of proteins in vitro as well as in vivo, although the previous technologies resulted in permanent fusion of the protein of interest to the DD, which can affect biological activity and complicate results. We previously reported a complementary strategy, termed traceless shielding (TShld), in which the protein of interest is released in its native form. Here, we describe an optimized protein concentration control system, TTShld, which retains the traceless features of TShld but utilizes two tiers of small molecule control to set protein concentrations in living cells. These experiments provide the first protein concentration control system that results in both a wide range of protein concentrations and proteins free from engineered fusion constructs. The TTShld system has a greatly improved dynamic range compared to our previously reported system, and the traceless feature is attractive for elucidation of the consequences of protein concentration in cell biology. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Coherent injection and control of ballistic charge currents in single-walled carbon nanotubes and graphite

    NASA Astrophysics Data System (ADS)

    Newson, R. W.; Green, A. A.; Hersam, M. C.; van Driel, H. M.

    2011-03-01

    We report results from a comprehensive set of experiments to study coherently controlled electrical current injection in single-walled carbon nanotubes (SWNTs) and graphite. Photocurrents were injected at room temperature through the quantum interference of single- and two-photon absorption pathways induced by 150-fs optical pulses with 660-980 and 1320-1960-nm central wavelengths, respectively, and with maximum intensities of 10 and 0.15 GW cm-2, respectively. Detection of the photocurrents was achieved via the emitted terahertz radiation. For bulk graphite samples and collinearly polarized 750- and 1500-nm pulses incident along the c axis, injected current densities up to 12 kA cm-2 have been observed just under the surface, independent of crystal azimuthal orientation and comparable to those generated in InP or GaAs. Current densities are ˜5 times smaller for cross-polarized pulses. A vertically aligned forest of carbon nanotubes (tube diameters ˜2.5 ± 1.5 nm) illuminated with 700- and 1400-nm pulses collinearly polarized along the alignment direction yields a maximum current of 8 nA per tube (current density of 35 kA cm-2). Terahertz emission drops by only 3.5 times after 90° sample rotation about the normal, which is explained in terms of an imperfect alignment distribution (angular spread ˜19.5°) and sample birefringence. Unaligned arc discharge and HiPco SWNTs with diameters of 1.44 ± 0.15 and 0.96 ± 0.15 nm, respectively, were sorted into semiconducting and metallic tubes. Photocurrents injected with collinearly polarized 750- and 1500-nm pulses in such semiconducting SWNTs showed peak current magnitudes similar to those in the aligned nanotubes, while metallic tubes yielded currents at least ten times smaller. Semiconducting SWNT currents showed spectral features as the second-harmonic wavelength varied from 660 to 980 nm, which were more consistent with current injection based on band-band transitions than on excitonic absorption effects.

  13. Understanding ultracold polar molecules

    NASA Astrophysics Data System (ADS)

    Julienne, Paul

    2009-05-01

    The successful production of a dense sample of ultracold ground state KRb polar molecules [1] opens the door to a new era of research with dipolar gases and lattices of such species. This feat was achieved by first associating a K and a Rb atom to make a weakly bound Feshbach molecule and then coherently transferring the population to the ground vibrational level of the molecule. This talk focuses on theoretical issues associated with making and using ultracold polar molecules, using KRb as an example [2]. Full understanding of this species and the processes by which it is made requires taking advantage of accurate molecular potentials [3], ab initio calculations [4], and the properties of the long-range potential. A highly accurate model is available for KRb for all bound states below the ground state separated atom limit and could be constructed for other species. The next step is to develop an understanding of the interactions between polar molecules, and their control in the ultracold domain. Understanding long-range interactions and threshold resonances will be crucial for future work. [1] K.-K. Ni, et al, Science 322, 231(2008). [2] P. S. Julienne, arXiv:0812:1233. [3] Pashov et al., Phys. Rev. A76, 022511 (2007). [4] S. Kotochigova, et al., arXiv:0901.1486.

  14. Biomimetic Nanoarchitectures for the Study of T Cell Activation with Single-Molecule Control

    NASA Astrophysics Data System (ADS)

    Cai, Haogang

    Physical factors in the environment of a cell affect its function and behavior in a variety of ways. There is increasing evidence that, among these factors, the geometric arrangement of receptor ligands plays an important role in setting the conditions for critical cellular processes. The goal of this thesis is to develop new techniques for probing the role of extracellular ligand geometry, with a focus on T cell activation. In this work, top-down molecular-scale nanofabrication and bottom-up selective self-assembly were combined in order to present functional nanomaterials (primarily biomolecules) on a surface with precise spatial control and single-molecule resolution. Such biomolecule nanoarrays are becoming an increasingly important tool in surface-based in vitro assays for biosensing, molecular and cellular studies. The nanoarrays consist of metallic nanodots patterned on glass coverslips using electron beam and nanoimprint lithography, combined with self-aligned pattern transfer. The nanodots were then used as anchors for the immobilization of biological ligands, and backfilled with a protein-repellent passivation layer of polyethylene glycol. The passivation efficiency was improved to minimize nonspecific adsorption. In order to ensure true single-molecule control, we developed an on-chip protocol to measure the molecular occupancy of nanodot arrays based on fluorescence photobleaching, while accounting for quenching effects by plasmonic absorption. We found that the molecular occupancy can be interpreted as a packing problem, with the solution depending on the nanodot size and the concentration of self-assembly reagents, where the latter can be easily adjusted to control the molecular occupancy according to the dot size. The optimized nanoarrays were used as biomimetic architectures for the study of T cell activation with single-molecule control. T cell activation involves an elaborate arrangement of signaling, adhesion, and costimulatory molecules

  15. Control of crystallographic orientation in diamond synthesis through laser resonant vibrational excitation of precursor molecules

    PubMed Central

    Xie, Zhi Qiang; Bai, Jaeil; Zhou, Yun Shen; Gao, Yi; Park, Jongbok; Guillemet, Thomas; Jiang, Lan; Zeng, Xiao Cheng; Lu, Yong Feng

    2014-01-01

    Crystallographic orientations determine the optical, electrical, mechanical, and thermal properties of crystals. Control of crystallographic orientations has been studied by changing the growth parameters, including temperature, pressure, proportion of precursors, and surface conditions. However, molecular dynamic mechanisms underlying these controls remain largely unknown. Here we achieved control of crystallographic orientations in diamond growth through a joint experimental and theoretical study of laser resonant vibrational excitation of precursor molecules (ethylene). Resonant vibrational excitation of the ethylene molecules using a wavelength-tunable CO2 laser steers the chemical reactions and promotes proportion of intermediate oxide species, which results in preferential growth of {100}-oriented diamond films and diamond single crystals in open air. Quantum molecular dynamic simulations and calculations of chemisorption energies of radicals detected from our mass-spectroscopy experiment provide an in-depth understanding of molecular reaction mechanisms in the steering of chemical reactions and control of crystallographic orientations. This finding opens up a new avenue for controlled chemical vapor deposition of crystals through resonant vibrational excitations to steer surface chemistry. PMID:24694918

  16. Can Internal Conversion BE Controlled by Mode-Specific Vibrational Excitation in Polyatomic Molecules

    NASA Astrophysics Data System (ADS)

    Portnov, Alexander; Epshtein, Michael; Bar, Ilana

    2017-06-01

    Nonadiabatic processes, dominated by dynamic passage of reactive fluxes through conical intersections (CIs) are considered to be appealing means for manipulating reaction paths. One approach that is considered to be effective in controlling the course of dissociation processes is the selective excitation of vibrational modes containing a considerable component of motion. Here, we have chosen to study the predissociation of the model test molecule, methylamine and its deuterated isotopologues, excited to well-characterized quantum states on the first excited electronic state, S_{1}, by following the N-H(D) bond fission dynamics through sensitive H(D) photofragment probing. The branching ratios between slow and fast H(D) photofragments, the internal energies of their counter radical photofragments and the anisotropy parameters for fast H photofragments, confirm correlated anomalies for predissociation initiated from specific rovibronic states, reflecting the existence of a dynamic resonance in each molecule. This resonance strongly depends on the energy of the initially excited rovibronic states, the evolving vibrational mode on the repulsive S_{1} part during N-H(D) bond elongation, and the manipulated passage through the CI that leads to radicals excited with C-N-H(D) bending and preferential perpendicular bond breaking, relative to the photolyzing laser polarization, in molecules containing the NH_{2} group. The indicated resonance plays an important role in the bifurcation dynamics at the CI and can be foreseen to exist in other photoinitiated processes and to control their outcome.

  17. A Bidirectional System for the Dynamic Small Molecule Control of Intracellular Fusion Proteins

    PubMed Central

    Kuzin, Alexander P.; Lew, Scott; Seetharaman, Jayaraman; Acton, Thomas B.; Kornhaber, Gregory J.; Xiao, Rong; Montelione, Gaetano Thomas; Tong, Liang; Crews, Craig M.

    2014-01-01

    Small molecule control of intracellular protein levels allows temporal and dose-dependent regulation of protein function. Recently, we developed a method to degrade proteins fused to a mutant dehalogenase (HaloTag2) using small molecule hydrophobic tags (HyTs). Here, we introduce a complementary method to stabilize the same HaloTag2 fusion proteins, resulting in a unified system allowing bidirectional control of cellular protein levels in a temporal and dose-dependent manner. From a small molecule screen, we identified N-(3,5-dichloro-2-ethoxybenzyl)-2H-tetrazol-5-amine as a nanomolar HALoTag2 Stabilizer (HALTS1) that reduces the Hsp70:HaloTag2 interaction, thereby preventing HaloTag2 ubiquitination. Finally, we demonstrate the utility of the HyT/HALTS system in probing the physiological role of therapeutic targets by modulating HaloTag2-fused oncogenic H-Ras, which resulted in either the cessation (HyT) or acceleration (HALTS) of cellular transformation. In sum, we present a general platform to study protein function, whereby any protein of interest fused to HaloTag2 can be either degraded 10-fold or stabilized 5-fold using two corresponding compounds. PMID:23978068

  18. A bidirectional system for the dynamic small molecule control of intracellular fusion proteins.

    PubMed

    Neklesa, Taavi K; Noblin, Devin J; Kuzin, Alexander; Lew, Scott; Seetharaman, Jayaraman; Acton, Thomas B; Kornhaber, Gregory; Xiao, Rong; Montelione, Gaetano T; Tong, Liang; Crews, Craig M

    2013-10-18

    Small molecule control of intracellular protein levels allows temporal and dose-dependent regulation of protein function. Recently, we developed a method to degrade proteins fused to a mutant dehalogenase (HaloTag2) using small molecule hydrophobic tags (HyTs). Here, we introduce a complementary method to stabilize the same HaloTag2 fusion proteins, resulting in a unified system allowing bidirectional control of cellular protein levels in a temporal and dose-dependent manner. From a small molecule screen, we identified N-(3,5-dichloro-2-ethoxybenzyl)-2H-tetrazol-5-amine as a nanomolar HALoTag2 Stabilizer (HALTS1) that reduces the Hsp70:HaloTag2 interaction, thereby preventing HaloTag2 ubiquitination. Finally, we demonstrate the utility of the HyT/HALTS system in probing the physiological role of therapeutic targets by modulating HaloTag2-fused oncogenic H-Ras, which resulted in either the cessation (HyT) or acceleration (HALTS) of cellular transformation. In sum, we present a general platform to study protein function, whereby any protein of interest fused to HaloTag2 can be either degraded 10-fold or stabilized 5-fold using two corresponding compounds.

  19. Shifts in controls on the temporal coherence of throughfall chemical flux in Acadia National Park, Maine, USA

    USGS Publications Warehouse

    Nelson, Sarah J.; Webster, Katherine E.; Loftin, Cynthia S.; Weathers, Kathleen C.

    2013-01-01

    Major ion and mercury (Hg) inputs to terrestrial ecosystems include both wet and dry deposition (total deposition). Estimating total deposition to sensitive receptor sites is hampered by limited information regarding its spatial heterogeneity and seasonality. We used measurements of throughfall flux, which includes atmospheric inputs to forests and the net effects of canopy leaching or uptake, for ten major ions and Hg collected during 35 time periods in 1999–2005 at over 70 sites within Acadia National Park, Maine to (1) quantify coherence in temporal dynamics of seasonal throughfall deposition and (2) examine controls on these patterns at multiple scales. We quantified temporal coherence as the correlation between all possible site pairs for each solute on a seasonal basis. In the summer growing season and autumn, coherence among pairs of sites with similar vegetation was stronger than for site-pairs that differed in vegetation suggesting that interaction with the canopy and leaching of solutes differed in coniferous, deciduous, mixed, and shrub or open canopy sites. The spatial pattern in throughfall hydrologic inputs across Acadia National Park was more variable during the winter snow season, suggesting that snow re-distribution affects net hydrologic input, which consequently affects chemical flux. Sea-salt corrected calcium concentrations identified a shift in air mass sources from maritime in winter to the continental industrial corridor in summer. Our results suggest that the spatial pattern of throughfall hydrologic flux, dominant seasonal air mass source, and relationship with vegetation in winter differ from the spatial pattern of throughfall flux in these solutes in summer and autumn. The coherence approach applied here made clear the strong influence of spatial heterogeneity in throughfall hydrologic inputs and a maritime air mass source on winter patterns of throughfall flux. By contrast, vegetation type was the most important influence on

  20. Rapid-Adiabatic Control of Ro-Vibrational Populations in Polyatomic Molecules

    NASA Astrophysics Data System (ADS)

    Zak, Emil J.; Yachmenev, Andrey

    2017-06-01

    We present a simple method for control of ro-vibrational populations in polyatomic molecules in the presence of inhomogeneous electric fields [1]. Cooling and trapping of heavy polar polyatomic molecules has become one of the frontier goals in high-resolution molecular spectroscopy, especially in the context of parity violation measurement in chiral compounds [2]. A key step toward reaching this goal would be development of a robust and efficient protocol for control of populations of ro-vibrational states in polyatomic, often floppy molecules. Here we demonstrate a modification of the stark-chirped rapid-adiabatic-passage technique (SCRAP) [3], designed for achieving high levels of control of ro-vibrational populations over a selected region in space. The new method employs inhomogeneous electric fields to generate space- and time- controlled Stark-shifts of energy levels in molecules. Adiabatic passage between ro-vibrational states is enabled by the pump pulse, which raises the value of the Rabi frequency. This Stark-chirped population transfer can be used in manipulation of population differences between high-field-seeking and low-field-seeking states of molecules in the Stark decelerator [4]. Appropriate timing of voltages on electric rods located along the decelerator combined with a single pump laser renders our method as potentially more efficient than traditional Stark decelerator techniques. Simulations for NH_3 show significant improvement in effectiveness of cooling, with respect to the standard 'moving-potential' method [5]. At the same time a high phase-space acceptance of the molecular packet is maintained. E. J. Zak, A. Yachmenev (submitted). C. Medcraft, R. Wolf, M. Schnell, Angew. Chem. Int. Ed., 53, 43, 11656-11659 (2014) M. Oberst, H. Munch, T. Halfman, PRL 99, 173001 (2007). K. Wohlfart, F. Grätz, F. Filsinger, H. Haak, G. Meijer, J. Küpper, Phys. Rev. A 77, 031404(R) (2008). H. L. Bethlem, F. M. H. Crompvoets, R. T. Jongma, S. Y. T. van de

  1. Electrostatic control over temperature-dependent tunnelling across a single-molecule junction

    PubMed Central

    Garrigues, Alvar R.; Wang, Lejia; del Barco, Enrique; Nijhuis, Christian A.

    2016-01-01

    Understanding how the mechanism of charge transport through molecular tunnel junctions depends on temperature is crucial to control electronic function in molecular electronic devices. With just a few systems investigated as a function of bias and temperature so far, thermal effects in molecular tunnel junctions remain poorly understood. Here we report a detailed charge transport study of an individual redox-active ferrocene-based molecule over a wide range of temperatures and applied potentials. The results show the temperature dependence of the current to vary strongly as a function of the gate voltage. Specifically, the current across the molecule exponentially increases in the Coulomb blockade regime and decreases at the charge degeneracy points, while remaining temperature-independent at resonance. Our observations can be well accounted for by a formal single-level tunnelling model where the temperature dependence relies on the thermal broadening of the Fermi distributions of the electrons in the leads. PMID:27211787

  2. Metal–Organic Frameworks as Platforms for the Controlled Nanostructuring of Single-Molecule Magnets

    SciTech Connect

    Aulakh, Darpandeep; Pyser, Joshua B.; Zhang, Xuan; Yakovenko, Andrey A.; Dunbar, Kim R.; Wriedt, Mario

    2015-07-29

    The prototypical SMM molecule [Mn12O12(O2CCH3)16(OH2)4] was incorporated under mild conditions into a highly porous metal-organic framework (MOF) matrix as a proof of principle for controlled nanostructuring of SMMs. Four independent experiments revealed that the SMM clusters were successfully loaded in the MOF pores, namely synchrotron-based powder diffraction, physisorption analysis, and in-depth magnetic and thermal analyses. The results provide incontrovertible evidence that the magnetic composite, SMM@MOF, combines key SMM properties with the functional properties of MOFs. Most importantly, the incorporated SMMs exhibit a significant enhanced thermal stability with SMM loading advantageously occurring at the periphery of the bulk MOF crystals with only a single SMM molecule isolated in the transverse direction of the pores.

  3. Coherent Optical Control of Electronic Excitations in Wide-Band-Gap Semiconductor Structures

    DTIC Science & Technology

    2015-05-01

    ABSTRACT The main objective of this research is to study coherent quantum effects , such as Rabi oscillations in optical spectra of wide- band-gap...DRI) Research Objectives 1 2. Temperature Effects in the Kinetics of Photoexcited Carriers in Wide- Band-Gap Semiconductors 2 2.1 Theoretical...3 Fig. 2 Calculated polar optical scattering rate for the nonparabolic conduction band in GaN including the screening effect

  4. Coherence protection by the quantum Zeno effect and nonholonomic control in a Rydberg rubidium isotope

    SciTech Connect

    Brion, E.; Akulin, V. M.; Comparat, D.; Kebaili, N.; Pillet, P.; Dumer, I.; Harel, G.; Kurizki, G.; Mazets, I.

    2005-05-15

    The protection of the coherence of open quantum systems against the influence of their environment is a very topical issue. A scheme is proposed here which protects a general quantum system from the action of a set of arbitrary uncontrolled unitary evolutions. This method draws its inspiration from ideas of standard error correction (ancilla adding, coding and decoding) and the quantum Zeno effect. A demonstration of our method on a simple atomic system--namely, a rubidium isotope--is proposed.

  5. Controlling charge transport mechanisms in molecular junctions: Distilling thermally induced hopping from coherent-resonant conduction

    NASA Astrophysics Data System (ADS)

    Kim, Hyehwang; Segal, Dvira

    2017-04-01

    The electrical conductance of molecular junctions may depend strongly on the temperature and weakly on molecular length, under two distinct mechanisms: phase-coherent resonant conduction, with charges proceeding via delocalized molecular orbitals, and incoherent thermally assisted multi-step hopping. While in the case of coherent conduction, the temperature dependence arises from the broadening of the Fermi distribution in the metal electrodes, in the latter case it corresponds to electron-vibration interaction effects on the junction. With the objective to distill the thermally activated hopping component, thus exposing intrinsic electron-vibration interaction phenomena on the junction, we suggest the design of molecular junctions with "spacers," extended anchoring groups that act to filter out phase-coherent resonant electrons. Specifically, we study the electrical conductance of fixed-gap and variable-gap junctions that include a tunneling block, with spacers at the boundaries. Using numerical simulations and analytical considerations, we demonstrate that in our design, resonant conduction is suppressed. As a result, the electrical conductance is dominated by two (rather than three) mechanisms: superexchange (deep tunneling) and multi-step thermally induced hopping. We further exemplify our analysis on DNA junctions with an A:T block serving as a tunneling barrier. Here, we show that the electrical conductance is insensitive to the number of G:C base-pairs at the boundaries. This indicates that the tunneling-to-hopping crossover revealed in such sequences truly corresponds to the properties of the A:T barrier.

  6. Comparison of optic area measurement using fundus photography and optical coherence tomography between optic nerve head drusen and control subjects.

    PubMed

    Flores-Rodríguez, Patricia; Gili, Pablo; Martín-Ríos, María Dolores; Grifol-Clar, Eulalia

    2013-03-01

    To compare optic disc area measurement between optic nerve head drusen (ONHD) and control subjects using fundus photography, time-domain optical coherence tomography (TD-OCT) and spectral-domain optical coherence tomography (SD-OCT). We also made a comparison between each of the three techniques. We performed our study on 66 eyes (66 patients) with ONHD and 70 healthy control subjects (70 controls) with colour ocular fundus photography at 20º (Zeiss FF 450 IR plus), TD-OCT (Stratus OCT) with the Fast Optic Disc protocol and SD-OCT (Cirrus OCT) with the Optic Disc Cube 200 × 200 protocol for measurement of the optic disc area. The measurements were made by two observers and in each measurement a correction of the image magnification factor was performed. Measurement comparison using the Student's t-test/Mann-Whitney U test, the intraclass correlation coefficient, Pearson/Spearman rank correlation coefficient and the Bland-Altman plot was performed in the statistical analysis. Mean and standard deviation (SD) of the optic disc area in ONHD and in controls was 2.38 (0.54) mm(2) and 2.54 (0.42) mm(2), respectively with fundus photography; 2.01 (0.56) mm(2) and 1.66 (0.37) mm(2), respectively with TD-OCT, and 2.03 (0.49) mm(2) and 1.75 (0.38) mm(2), respectively with SD-OCT. In ONHD and controls, repeatability of optic disc area measurement was excellent with fundus photography and optical coherence tomography (TD-OCT and SD-OCT), but with a low degree of agreement between both techniques. Optic disc area measurement is smaller in ONHD compared to healthy subjects with fundus photography, unlike time-domain and spectral-domain optical coherence tomography in which the reverse is true. Both techniques offer good repeatability, but a low degree of correlation and agreement, which means that optic disc area measurement is not interchangeable or comparable between techniques. Ophthalmic & Physiological Optics © 2013 The College of Optometrists.

  7. Quantum optimal control of the isotope-selective rovibrational excitation of diatomic molecules

    NASA Astrophysics Data System (ADS)

    Kurosaki, Yuzuru; Yokoyama, Keiichi

    2017-08-01

    We carry out optimal control theory calculations for isotope-selective pure rotational and vibrational-rotational excitations of diatomic molecules. The fifty-fifty mixture of diatomic isotopologues, 7Li37Cl and 7Li35Cl, is considered and the molecules are irradiated with a control pulse. In the wave packet propagation we employ the method quantum mechanically rigorous for the two-dimensional system including both the radial and angular motions. We investigate quantum controls of the isotope-selective pure rotational excitation for two total times 1280000 and 2560000 a.u. (31.0 and 61.9 ps) and the vibrational-rotational excitation for three total times, 640000, 1280000, and 2560000 a.u. (15.5, 31.0, and 61.9 ps) The initial state is set to the situation that both the isotopologues are in the ground vibrational and rotational levels, v = 0 and J = 0. The target state for pure rotational excitation is set to 7Li37Cl (v = 0, J = 1) and 7Li35Cl (v = 0, J = 0); that for vibrational-rotational excitation is set to 7Li37Cl (v = 1, J = 1) and 7Li35Cl (v = 0, J = 0). The obtained final yields are quite high and those for the longest total time are calculated to be nearly 1.0. When total time is 1280000 a.u., the final yields for the pure rotational excitation are slightly smaller than those for the vibrational-rotational excitation. This is because the isotope shift (difference in transition energy between the two isotopologues) for the pure rotational transition between low-lying levels is much smaller than that for the vibrational-rotational transition. We thus theoretically succeed in controlling the isotope-selective excitations of diatomic molecules using the method including both radial and angular motions quantum mechanically.

  8. Adaptive Control Model Reveals Systematic Feedback and Key Molecules in Metabolic Pathway Regulation

    PubMed Central

    Moffitt, Richard A.; Merrill, Alfred H.; Wang, May D.

    2011-01-01

    Abstract Robust behavior in metabolic pathways resembles stabilized performance in systems under autonomous control. This suggests we can apply control theory to study existing regulation in these cellular networks. Here, we use model-reference adaptive control (MRAC) to investigate the dynamics of de novo sphingolipid synthesis regulation in a combined theoretical and experimental case study. The effects of serine palmitoyltransferase over-expression on this pathway are studied in vitro using human embryonic kidney cells. We report two key results from comparing numerical simulations with observed data. First, MRAC simulations of pathway dynamics are comparable to simulations from a standard model using mass action kinetics. The root-sum-square (RSS) between data and simulations in both cases differ by less than 5%. Second, MRAC simulations suggest systematic pathway regulation in terms of adaptive feedback from individual molecules. In response to increased metabolite levels available for de novo sphingolipid synthesis, feedback from molecules along the main artery of the pathway is regulated more frequently and with greater amplitude than from other molecules along the branches. These biological insights are consistent with current knowledge while being new that they may guide future research in sphingolipid biology. In summary, we report a novel approach to study regulation in cellular networks by applying control theory in the context of robust metabolic pathways. We do this to uncover potential insight into the dynamics of regulation and the reverse engineering of cellular networks for systems biology. This new modeling approach and the implementation routines designed for this case study may be extended to other systems. Supplementary Material is available at www.liebertonline.com/cmb. PMID:21314456

  9. Goal-directed control with cortical units that are gated by both top-down feedback and oscillatory coherence

    PubMed Central

    Kerr, Robert R.; Grayden, David B.; Thomas, Doreen A.; Gilson, Matthieu; Burkitt, Anthony N.

    2014-01-01

    The brain is able to flexibly select behaviors that adapt to both its environment and its present goals. This cognitive control is understood to occur within the hierarchy of the cortex and relies strongly on the prefrontal and premotor cortices, which sit at the top of this hierarchy. Pyramidal neurons, the principal neurons in the cortex, have been observed to exhibit much stronger responses when they receive inputs at their soma/basal dendrites that are coincident with inputs at their apical dendrites. This corresponds to inputs from both lower-order regions (feedforward) and higher-order regions (feedback), respectively. In addition to this, coherence between oscillations, such as gamma oscillations, in different neuronal groups has been proposed to modulate and route communication in the brain. In this paper, we develop a simple, but novel, neural mass model in which cortical units (or ensembles) exhibit gamma oscillations when they receive coherent oscillatory inputs from both feedforward and feedback connections. By forming these units into circuits that can perform logic operations, we identify the different ways in which operations can be initiated and manipulated by top-down feedback. We demonstrate that more sophisticated and flexible top-down control is possible when the gain of units is modulated by not only top-down feedback but by coherence between the activities of the oscillating units. With these types of units, it is possible to not only add units to, or remove units from, a higher-level unit's logic operation using top-down feedback, but also to modify the type of role that a unit plays in the operation. Finally, we explore how different network properties affect top-down control and processing in large networks. Based on this, we make predictions about the likely connectivities between certain brain regions that have been experimentally observed to be involved in goal-directed behavior and top-down attention. PMID:25152715

  10. Goal-directed control with cortical units that are gated by both top-down feedback and oscillatory coherence.

    PubMed

    Kerr, Robert R; Grayden, David B; Thomas, Doreen A; Gilson, Matthieu; Burkitt, Anthony N

    2014-01-01

    The brain is able to flexibly select behaviors that adapt to both its environment and its present goals. This cognitive control is understood to occur within the hierarchy of the cortex and relies strongly on the prefrontal and premotor cortices, which sit at the top of this hierarchy. Pyramidal neurons, the principal neurons in the cortex, have been observed to exhibit much stronger responses when they receive inputs at their soma/basal dendrites that are coincident with inputs at their apical dendrites. This corresponds to inputs from both lower-order regions (feedforward) and higher-order regions (feedback), respectively. In addition to this, coherence between oscillations, such as gamma oscillations, in different neuronal groups has been proposed to modulate and route communication in the brain. In this paper, we develop a simple, but novel, neural mass model in which cortical units (or ensembles) exhibit gamma oscillations when they receive coherent oscillatory inputs from both feedforward and feedback connections. By forming these units into circuits that can perform logic operations, we identify the different ways in which operations can be initiated and manipulated by top-down feedback. We demonstrate that more sophisticated and flexible top-down control is possible when the gain of units is modulated by not only top-down feedback but by coherence between the activities of the oscillating units. With these types of units, it is possible to not only add units to, or remove units from, a higher-level unit's logic operation using top-down feedback, but also to modify the type of role that a unit plays in the operation. Finally, we explore how different network properties affect top-down control and processing in large networks. Based on this, we make predictions about the likely connectivities between certain brain regions that have been experimentally observed to be involved in goal-directed behavior and top-down attention.

  11. Capacity of optical communications over a lossy bosonic channel with a receiver employing the most general coherent electro-optic feedback control

    NASA Astrophysics Data System (ADS)

    Chung, Hye Won; Guha, Saikat; Zheng, Lizhong

    2017-07-01

    We study the problem of designing optical receivers to discriminate between multiple coherent states using coherent processing receivers—i.e., one that uses arbitrary coherent feedback control and quantum-noise-limited direct detection—which was shown by Dolinar to achieve the minimum error probability in discriminating any two coherent states. We first derive and reinterpret Dolinar's binary-hypothesis minimum-probability-of-error receiver as the one that optimizes the information efficiency at each time instant, based on recursive Bayesian updates within the receiver. Using this viewpoint, we propose a natural generalization of Dolinar's receiver design to discriminate M coherent states, each of which could now be a codeword, i.e., a sequence of N coherent states, each drawn from a modulation alphabet. We analyze the channel capacity of the pure-loss optical channel with a general coherent-processing receiver in the low-photon number regime and compare it with the capacity achievable with direct detection and the Holevo limit (achieving the latter would require a quantum joint-detection receiver). We show compelling evidence that despite the optimal performance of Dolinar's receiver for the binary coherent-state hypothesis test (either in error probability or mutual information), the asymptotic communication rate achievable by such a coherent-processing receiver is only as good as direct detection. This suggests that in the infinitely long codeword limit, all potential benefits of coherent processing at the receiver can be obtained by designing a good code and direct detection, with no feedback within the receiver.

  12. Control of coherence among the spins of a single electron and the three nearest neighbor {sup 13}C nuclei of a nitrogen-vacancy center in diamond

    SciTech Connect

    Shimo-Oka, T.; Miwa, S.; Suzuki, Y.; Mizuochi, N.; Kato, H.; Yamasaki, S.; Jelezko, F.

    2015-04-13

    Individual nuclear spins in diamond can be optically detected through hyperfine couplings with the electron spin of a single nitrogen-vacancy (NV) center; such nuclear spins have outstandingly long coherence times. Among the hyperfine couplings in the NV center, the nearest neighbor {sup 13}C nuclear spins have the largest coupling strength. Nearest neighbor {sup 13}C nuclear spins have the potential to perform fastest gate operations, providing highest fidelity in quantum computing. Herein, we report on the control of coherences in the NV center where all three nearest neighbor carbons are of the {sup 13}C isotope. Coherence among the three and four qubits are generated and analyzed at room temperature.

  13. Optical emission of a plasma from low-density targets irradiated with coherence-controllable laser radiation

    NASA Astrophysics Data System (ADS)

    Fronya, A. A.; Borisenko, N. G.; Puzyrev, V. N.; Sahakyan, A. T.; Starodub, A. N.; Yakushev, O. F.

    2017-03-01

    The results of experiments on the interaction of nanosecond laser radiation with low-density volume-structured targets of different density and thickness are reported. The targets were irradiated by laser radiation with controllable coherence. The primary objective was to investigate the effect of target parameters on the characteristics of radiation scattered by the plasma. The spectral characteristics of the radiation scattered by the plasma in the backward direction and in the direction of laser beam propagation were obtained. Also the radiation scattering patterns were recorded.

  14. Smart magnetic poly(N-isopropylacrylamide) to control the release of bio-active molecules.

    PubMed

    Dionigi, Chiara; Lungaro, Lisa; Goranov, Vitaly; Riminucci, Alberto; Piñeiro-Redondo, Yolanda; Bañobre-López, Manuel; Rivas, José; Dediu, Valentin

    2014-10-01

    Thermo switchable magnetic hydrogels undoubtedly have a great potential for medical applications since they can behave as smart carriers able to transport bioactive molecules to a chosen part of the body and release them on demand via magneto-thermal activation. We report on the ability to modify the lower critical solution temperature (LCST) of poly(N-isopropylacrylamide) (PNIPAM) on demand from 32 °C to LCST ≥ 37 °C. This was achieved by the absorption of controlled amounts of magnetite nanoparticles on the polymer chains. We show, through the effect on cell viability, that the resulting magnetic PNIPAM is able to trap and to release bio-active molecules, such as cell growth factors. The activities of the released bio molecule are tested on human umbilical vein endothelial cells culture. We demonstrate that the LCST of the magnetic PNIPAM can be reached remotely via inductive heating with an alternating magnetic field. This approach on magnetic PNIPAM clearly supports appealing applications in safe biomedicine.

  15. Fabrication and Control of Two-Dimensional Crystalline Arrays of Protein Molecules

    NASA Astrophysics Data System (ADS)

    Nagayama, Kuniaki; Takeda, Shigeki; Endo, Shigeru; Yoshimura, Hideyuki

    1995-07-01

    Fabrication methods to produce two-dimensional (2D) crystalline arrays of protein particles are reported. The key innovation in this fabrication is the spreading wetting process which uses the deformable substrate surface such as mercury surface (mercury method) or the air-water interface (subphase method), where protein solution spread to yield a thin liquid film. The thin film of protein solution leaves a monolayer state of protein molecules, for example 2D crystalline films, after the condensation of solute protein molecules by solvent removal by evaporation. The significance of the film fabrication lies in its active natures to harness the directional transport of particles driven by spreading or convective flow of the solution. Wild type and mutant ferritins were employed to spread their solution on substrates and align them to 2D arrays. The control of crystal forms, say hexagonal or tetragonal, has been pursued by changing the interprotein interaction through mutagenic replacements of amino acids at specific sites on the protein surface. With recombinant ferritins, conversion of crystal forms from hexagonal to oblique is observed by eliminating strong interaction of salt bridge kind between adjacent molecules in the crystal.

  16. Observation and electric current control of a local spin in a single-molecule magnet

    PubMed Central

    Komeda, Tadahiro; Isshiki, Hironari; Liu, Jie; Zhang, Yan-Feng; Lorente, Nicolás; Katoh, Keiichi; Breedlove, Brian K.; Yamashita, Masahiro

    2011-01-01

    In molecular spintronics, the spin state of a molecule may be switched on and off by changing the molecular structure. Here, we switch on and off the molecular spin of a double-decker bis(phthalocyaninato)terbium(III) complex (TbPc2) adsorbed on an Au(111) surface by applying an electric current via a scanning tunnelling microscope. The dI/dV curve of the tunnelling current recorded onto a TbPc2 molecule shows a Kondo peak, the origin of which is an unpaired spin of a π-orbital of a phthalocyaninato (Pc) ligand. By applying controlled current pulses, we could rotate the upper Pc ligand in TbPc2, leading to the disappearance and reappearance of the Kondo resonance. The rotation shifts the molecular frontier-orbital energies, quenching the π-electron spin. Reversible switching between two stable ligand orientations by applying a current pulse should make it possible to code information at the single-molecule level. PMID:21364556

  17. Morphology-Controlled High-Efficiency Small Molecule Organic Solar Cells without Additive Solvent Treatment

    PubMed Central

    Kim, Il Ku; Jo, Jun Hyung; Yun, Jung-Ho

    2016-01-01

    This paper focuses on nano-morphology-controlled small-molecule organic solar cells without solvent treatment for high power-conversion efficiencies (PCEs). The maximum high PCE reaches up to 7.22% with a bulk-heterojunction (BHJ) thickness of 320 nm. This high efficiency was obtained by eliminating solvent additives such as 1,8-diiodooctane (DIO) to find an alternative way to control the domain sizes in the BHJ layer. Furthermore, the generalized transfer matrix method (GTMM) analysis has been applied to confirm the effects of applying a different thickness of BHJs for organic solar cells from 100 to 320 nm, respectively. Finally, the study showed an alternative way to achieve high PCE organic solar cells without additive solvent treatments to control the morphology of the bulk-heterojunction.

  18. Selective control over fragmentation reactions in polyatomic molecules using impulsive laser alignment.

    PubMed

    Xie, Xinhua; Doblhoff-Dier, Katharina; Xu, Huailiang; Roither, Stefan; Schöffler, Markus S; Kartashov, Daniil; Erattupuzha, Sonia; Rathje, Tim; Paulus, Gerhard G; Yamanouchi, Kaoru; Baltuška, Andrius; Gräfe, Stefanie; Kitzler, Markus

    2014-04-25

    We investigate the possibility of using molecular alignment for controlling the relative probability of individual reaction pathways in polyatomic molecules initiated by electronic processes on the few-femtosecond time scale. Using acetylene as an example, it is shown that aligning the molecular axis with respect to the polarization direction of the ionizing laser pulse does not only allow us to enhance or suppress the overall fragmentation yield of a certain fragmentation channel but, more importantly, to determine the relative probability of individual reaction pathways starting from the same parent molecular ion. We show that the achieved control over dissociation or isomerization pathways along specific nuclear degrees of freedom is based on a controlled population of associated excited dissociative electronic states in the molecular ion due to relatively enhanced ionization contributions from inner valence orbitals.

  19. Controlled delivery of bioactive molecules into live cells using the bacterial mechanosensitive channel MscL

    PubMed Central

    Doerner, Julia F.; Febvay, Sebastien; Clapham, David E.

    2013-01-01

    Bacterial mechanosensitive channels are some of the largest pores in nature. In particular, MscL, with a pore diameter > 25 Å, allows passage of large organic ions and small proteins. Functional MscL reconstitution into lipids has been proposed for applications in vesicular-based drug release. Here we show that these channels can be functionally expressed in mammalian cells to afford rapid controlled uptake of membrane impermeable molecules. We first demonstrate that MscL gating in response to increased membrane tension is preserved in mammalian cell membranes. Molecular delivery is controlled by adopting an established method of MscL charge-induced activation. We then determine pore size limitations using fluorescently labeled model cargoes. Finally, we activate MscL to introduce the cell-impermeable bi-cyclic peptide phalloidin, a specific marker for actin filaments, into cells. We propose that MscL will be a useful tool for gated and controlled delivery of bioactive molecules into cells. PMID:22871809

  20. Kondo-correlated transport in single molecule ferromagnetic break junction devices with controllable electrode magnetization alignment

    NASA Astrophysics Data System (ADS)

    Scott, Gavin; Hu, Ting-Chen

    A quantum dot attached to electrodes with magnetizations that can be switched between parallel and anti-parallel alignment has been proposed as a platform for investigating quantum criticality associated with the destruction of Kondo entanglement. We have fabricated single molecule break junction devices with elliptical ferromagnetic electrodes designed to suit this purpose. Low temperature transport measurements, supported by micromagnetic simulations, were used to investigate the magnetoresistance response on control samples during the magnetization reversal process. We show results of Kondo-correlated transport as the source and drain contacts are switched between parallel and anti-parallel magnetization configurations.

  1. Imaging and control of interfering wave packets in a dissociating molecule.

    PubMed

    Skovsen, Esben; Machholm, Mette; Ejdrup, Tine; Thøgersen, Jan; Stapelfeldt, Henrik

    2002-09-23

    Using two identical 110 femtosecond (fs) optical pulses separated by 310 fs, we launch two dissociative wave packets in I2. We measure the square of the wave function as a function of both the internuclear separation, /Psi(R)/(2), and of the internuclear velocity, /Psi(v(R))/(2), by ionizing the dissociating molecule with an intense 20 fs probe pulse. Strong interference is observed in both /Psi(R)/(2) and in /Psi(v(R))/(2). The interference, and therefore the shape of the wave function, is controlled through the phase difference between the two dissociation pulses in good agreement with calculations.

  2. Harmonic spectral modulation of an optical frequency comb to control the ultracold molecules formation

    NASA Astrophysics Data System (ADS)

    Malinovskaya, Svetlana A.; Liu, Gengyuan

    2016-11-01

    A method for creation of ultracold molecules by stepwise adiabatic passage from the Feshbach state to the fundamentally ground state using an optical frequency comb is presented within a semiclassical multilevel model. The sine modulation of the spectral phase of the comb leads to the creation of a quasi-dark dressed state. An insignificant population of the excited state manifold in this dark state provides an efficient way of mitigating decoherence in the system. In contrast, the cosine modulation does not lead to the quasi-dark state formation. The results demonstrate the importance of the parity of the spectral chirp in quantum control.

  3. The controllable assembly of nanorods, nanowires and microwires of a perylenediimide molecule with photoswitching property

    NASA Astrophysics Data System (ADS)

    Ma, Ying; An, Boxing; Wang, Meng; Shi, Fangxiao; Wang, Qing; Gu, Yaxin; Niu, Wanyang; Fan, Zhaorong; Shang, Yanli; Wang, Dan; Zhao, Cong

    2015-07-01

    By using an electron donor-acceptor molecule that consists of a perylenediimide (PDI) core bonded with two ferrocene (Fc) units, well-defined nanorods, nanowires and microwires of PDI-Fc were formed through simply adjusting the initial concentration of PDI-Fc in dichloromethane or CH2Cl2. Moreover, the two-ended devices based on individual microwire were fabricated. Highly reproducible and sensitive photo response characteristics were demonstrated in the microwire through controlling the white light on and off with different light intensities. The assembly strategy via complementary donors and acceptors is of significance for constructing photoconductive systems and developing novel functional devices.

  4. Optimizing coherent anti-Stokes Raman scattering by genetic algorithm controlled pulse shaping

    NASA Astrophysics Data System (ADS)

    Yang, Wenlong; Sokolov, Alexei

    2010-10-01

    The hybrid coherent anti-Stokes Raman scattering (CARS) has been successful applied to fast chemical sensitive detections. As the development of femto-second pulse shaping techniques, it is of great interest to find the optimum pulse shapes for CARS. The optimum pulse shapes should minimize the non-resonant four wave mixing (NRFWM) background and maximize the CARS signal. A genetic algorithm (GA) is developed to make a heuristic searching for optimized pulse shapes, which give the best signal the background ratio. The GA is shown to be able to rediscover the hybrid CARS scheme and find optimized pulse shapes for customized applications by itself.

  5. Coherent control of a single nitrogen-vacancy center spin in optically levitated nanodiamond

    DOE PAGES

    Pettit, Robert M.; Neukirch, Levi Patrick; Zhang, Yi; ...

    2017-05-12

    Here, we report the first observation, to the best of our knowledge, of electron spin transients in single negatively charged nitrogen-vacancy (NV-) centers, contained within optically trapped nanodiamonds, in both atmospheric pressure and low vacuum. It is shown that, after an initial exposure to low vacuum, the trapped nanodiamonds remain at temperatures near room temperature even in low vacuum. Furthermore, the transverse coherence time of the NV- center spin, measured to be T2=101.4 ns, is robust over the range of trapping powers considered in this study.

  6. A quantum gas of polar molecules

    NASA Astrophysics Data System (ADS)

    Ni, Kang-Kuen

    Ultracold polar molecular gases promise new directions and exciting applications in precision measurements, ultracold chemistry, electric-field controlled collisions, dipolar quantum gases, and quantum information sciences. This thesis presents experimental realization of a near quantum degenerate gas of polar molecules, where the phase-space density of the gas achieved is more than 10 orders of magnitude higher than previous results. The near quantum degenerate gas of polar molecules is created using two coherent steps. First, atoms in an ultracold gas mixture are converted into extremely weakly bound molecules near a Fano-Feshbach resonance. Second, the weakly bound molecules are transferred to the ro-vibronic ground state using a coherent two-photon Raman technique. The fact that these ground-state molecules are polar is confirmed with a spectroscopic measurement of the permanent electric dipole moment. Finally, manipulation of the molecular hyperfine state is demonstrated; this allows molecules to be populated in a single quantum state, in particular, the lowest energy state. With an ultracold gas of molecules, full control of molecular internal state, and electric field as a new handle, ultracold molecular collisions, including ultracold chemical reactions and dipolar collisions, are studied.

  7. Voluntary control of corticomuscular coherence through neurofeedback: a proof-of-principle study in healthy subjects.

    PubMed

    von Carlowitz-Ghori, K; Bayraktaroglu, Z; Waterstraat, G; Curio, G; Nikulin, V V

    2015-04-02

    Corticomuscular coherence (CMC) relates to synchronization between activity in the motor cortex and the muscle activity. The strength of CMC can be affected by motor behavior. In a proof-of-principle study, we examined whether independent of motor output parameters, healthy subjects are able to voluntarily modulate CMC in a neurofeedback paradigm. Subjects received visual online feedback of their instantaneous CMC strength, which was calculated between an optimized spatial projection of multichannel electroencephalography (EEG) and electromyography (EMG) in an individually defined target frequency range. The neurofeedback training consisted of either increasing or decreasing CMC strength using a self-chosen mental strategy while performing a simple motor task. Evaluation of instantaneous coherence showed that CMC strength was significantly larger when subjects had to increase than when to decrease CMC; this difference between the two task conditions did not depend on motor performance. The exclusion of confounding factors such as motor performance, attention and task complexity in study design provides evidence that subjects were able to voluntarily modify CMC independent of motor output parameters. Additional analysis further strengthened the assumption that the subjects' response was specifically shaped by the neurofeedback. In perspective, we suggest that CMC-based neurofeedback could provide a therapeutic approach in clinical conditions, such as motor stroke, where CMC is altered.

  8. Laser-controlled vibrational heating and cooling of oriented H+2 molecules

    NASA Astrophysics Data System (ADS)

    Niederhausen, Thomas; Thumm, Uwe; Martín, Fernando

    2012-05-01

    We investigate the control of the vibrational dynamics in the hydrogen molecular ion H+2 using strong femto-second infrared control-laser pulses. For our three-dimensional calculations, we use infrared laser pulses of 800 nm wavelength, 6 fs pulse duration and a peak intensity between 1012 and 1015 W cm-2. For laser electric fields aligned along the molecular axis, we numerically solve the full vibronic Schrödinger equation and compare our results with a model calculation that only includes the nuclear motion on the two lowest coupled adiabatic Born-Oppenheimer potential curves. The initial vibrational wave packet is launched with the ionization of the parent H2 molecule in the pump pulse. Precise timing between pump- and control-laser pulses allows for the direct manipulation of the final bound vibrational-state composition and dissociation dynamics of the ion. We show that significant enhancement of the occupation of particular stationary vibrational-state contributions can be achieved for laser intensities below the onset of strong ionization (≈1014 W cm-2). In addition, we find that this vibrational selectivity strongly depends on the delay time but not on the intensity of the control pulse. The relative stationary vibrational-state contributions and the shape of the vibrating wave packet depend sensitively on the control-pulse delay time, and the overall amplitude of the final vibrational wave packet depends on the intensity of the control pulse.

  9. Thermally controlled permeation of ionic molecules through synthetic nanopores functionalized with amine-terminated polymer brushes

    NASA Astrophysics Data System (ADS)

    Nasir, Saima; Ali, Mubarak; Ensinger, Wolfgang

    2012-06-01

    We present temperature-dependent ionic transport through an array of nanopores (cylindrical and conical) and a single conical nanopore functionalized with amine-terminated poly(N-isopropylacrylamide) [PNIPAAM-NH2] brushes. For this purpose, nanopores are fabricated in heavy ion irradiated polyethylene terephthlate (PET) membranes by a controlled chemical track-etching technique, which leads to the generation of carboxyl (COOH) groups on the pore surface. End-functionalized polymer chains are immobilized onto the inner pore walls via a ‘grafting-to’ approach through the covalent linkage of surface COOH moieties with the terminal amine groups of the PNIPAAM molecules by using carbodiimide coupling chemistry. The success of the chemical modification reaction is corroborated by measuring the permeation flux of charged analytes across the multipore membranes in an aqueous solution, and for the case of single conical pore by measuring the current-voltage (I-V) characteristics, which are dictated by the electrostatic interaction of the charged pore surface with the mobile ions in an electrolyte solution. The effective nanopore diameter is tuned by manipulating the environmental temperature due to the swelling/shrinking behaviour of polymer brushes attached to the inner nanopore walls, leading to a decrease/increase in the ionic transport across the membrane. This process should permit the thermal gating and controlled release of ionic drug molecules through the nanopores modified with thermoresponsive polymer chains across the membrane.

  10. A flexible metal–organic framework: Guest molecules controlled dynamic gas adsorption

    DOE PAGES

    Mahurin, Shannon Mark; Li, Man -Rong; Wang, Hailong; ...

    2015-04-13

    A flexible metal–organic framework (MOF) of [Zn3(btca)2(OH)2]·(guest)n (H2btca = 1,2,3-benzotriazole-5-carboxylic acid) that exhibits guest molecule-controlled dynamic gas adsorption is reported in which carbon dioxide molecules rather than N2, He, and Ar induce a structural transition with a corresponding appearance of additional steps in the isotherms. Physical insights into the dynamic adsorption behaviors of flexible compound 1 were detected by gas adsorption at different temperatures and different pressures and confirmed by Fourier transform infrared spectroscopy and molecular simulations. Interestingly, by taking advantage of the flexible nature inherent to the framework, this MOF material enables highly selective adsorption of CO2/N2, CO2/Ar, andmore » CO2/He of 36.3, 32.6, and 35.9, respectively, at 298 K. Furthermore, this class of flexible MOFs has potential applications for controlled release, molecular sensing, noble gas separation, smart membranes, and nanotechnological devices.« less

  11. A flexible metal–organic framework: Guest molecules controlled dynamic gas adsorption

    SciTech Connect

    Mahurin, Shannon Mark; Li, Man -Rong; Wang, Hailong; Lu, Zhengliang; Chen, Banglin; Dai, Sheng; Yue, Yanfeng; Rabone, Jeremy A.; Liu, Hongjun; Wang, Jihang; Fang, Youxing

    2015-04-13

    A flexible metal–organic framework (MOF) of [Zn3(btca)2(OH)2]·(guest)n (H2btca = 1,2,3-benzotriazole-5-carboxylic acid) that exhibits guest molecule-controlled dynamic gas adsorption is reported in which carbon dioxide molecules rather than N2, He, and Ar induce a structural transition with a corresponding appearance of additional steps in the isotherms. Physical insights into the dynamic adsorption behaviors of flexible compound 1 were detected by gas adsorption at different temperatures and different pressures and confirmed by Fourier transform infrared spectroscopy and molecular simulations. Interestingly, by taking advantage of the flexible nature inherent to the framework, this MOF material enables highly selective adsorption of CO2/N2, CO2/Ar, and CO2/He of 36.3, 32.6, and 35.9, respectively, at 298 K. Furthermore, this class of flexible MOFs has potential applications for controlled release, molecular sensing, noble gas separation, smart membranes, and nanotechnological devices.

  12. Quantum control of ultracold NaK polar molecules in optical traps

    NASA Astrophysics Data System (ADS)

    Li, Ming; Petrov, Alexander; Makrides, Constantinos; Kotochigova, Svetlana

    2016-05-01

    Selection of trapping conditions with ultracold molecules, where internal states experience identical trapping potentials, brings substantial benefits for the ultimate control of their internal degrees of freedom. Here we present our work on the control of NaK molecules, when they are subjected to both trapping laser light and external electric and magnetic fields. First, we calculated parallel and perpendicular polarizabilities using a coupled-cluster method at the CCSD level. This enables us to determine the differential Stark shifts of rotational levels of NaK as a function of orientation of external fields. The hyperfine and Zeeman structure of these rotational states was obtained using an effective spin Hamiltonian. We find that under the experimental conditions with NaK, the hyperfine sublevels of the J = 1 rotational state are significantly mixed by the trapping laser light so that the simplified model of Ref. for ``magic'' conditions can not be applied. Adding a modest static electric field, however, can minimize the mixing of magnetic sublevels and make it easier to find ``magic'' conditions. This work is supported by the ARO-MURI Grant No. W911NF-12-1-0476 and the NSF Grant No. PHY-1308573.

  13. The controllable assembly of nanorods, nanowires and microwires of a perylenediimide molecule with photoswitching property

    SciTech Connect

    Ma, Ying; An, Boxing; Wang, Meng; Shi, Fangxiao; Wang, Qing; Gu, Yaxin; Niu, Wanyang; Fan, Zhaorong; Shang, Yanli; Wang, Dan; Zhao, Cong

    2015-07-15

    By using an electron donor–acceptor molecule that consists of a perylenediimide (PDI) core bonded with two ferrocene (Fc) units, well-defined nanorods, nanowires and microwires of PDI-Fc were formed through simply adjusting the initial concentration of PDI-Fc in dichloromethane or CH{sub 2}Cl{sub 2}. Moreover, the two-ended devices based on individual microwire were fabricated. Highly reproducible and sensitive photo response characteristics were demonstrated in the microwire through controlling the white light on and off with different light intensities. The assembly strategy via complementary donors and acceptors is of significance for constructing photoconductive systems and developing novel functional devices. - Graphical abstract: The two-ended devices based on individual microwire were fabricated. Highly reproducible and sensitive photo response characteristics were observed by controlling the white light on and off with different light intensities. - Highlights: • An electron donor–acceptor molecule (PDI-Fc) was synthesized. • Well-defined nanorods, nanowires and microwires of PDI-Fc were formed. • The two-ended devices based on individual microwire were fabricated. • Highly reproducible and sensitive photo response characteristics were observed.

  14. Thermal control of sequential on-surface transformation of a hydrocarbon molecule on a copper surface

    PubMed Central

    Kawai, Shigeki; Haapasilta, Ville; Lindner, Benjamin D.; Tahara, Kazukuni; Spijker, Peter; Buitendijk, Jeroen A.; Pawlak, Rémy; Meier, Tobias; Tobe, Yoshito; Foster, Adam S.; Meyer, Ernst

    2016-01-01

    On-surface chemical reactions hold the potential for manufacturing nanoscale structures directly onto surfaces by linking carbon atoms in a single-step reaction. To fabricate more complex and functionalized structures, the control of the on-surface chemical reactions must be developed significantly. Here, we present a thermally controlled sequential three-step chemical transformation of a hydrocarbon molecule on a Cu(111) surface. With a combination of high-resolution atomic force microscopy and first-principles computations, we investigate the transformation process in step-by-step detail from the initial structure to the final product via two intermediate states. The results demonstrate that surfaces can be used as catalysing templates to obtain compounds, which cannot easily be synthesized by solution chemistry. PMID:27619070

  15. Controlled interference of association paths in the conversion of ultracold atoms into molecules

    NASA Astrophysics Data System (ADS)

    Plata, J.

    2015-12-01

    We present a proposal for controlling the conversion of ultracold atoms into molecules by fixing the phase difference between two oscillating magnetic fields. The scheme is based on the use of a magnetic Feshbach resonance with a field modulation that incorporates terms oscillating with frequencies corresponding to the main resonance and one of the subharmonics. The interference between the two association processes activated by the oscillating terms is controlled via the phase difference. As a result, significant increase or decrease of the effective interaction strength can be achieved. The realization of the proposal is feasible under standard technical conditions. In particular, the method is found to be robust against the effect of the sources of decoherence present in the practical setup. The applicability of the approach to deal with quadratic terms in the field modulation is discussed.

  16. Controlling Protein Conformations to Explore Unprecedented Material Properties by Single-Molecule Surgery

    DTIC Science & Technology

    2012-08-17

    Molecule Protein Conformational Dynamics in Enzymatic Reactions,” Single-Molecule Biophysics Meeting, Aspen , CO, Jan. 4-10, 2009. H. P. Lu, “Single...Donor-Acceptor: Cy3-Cy5) pair labeled HPPK molecule tethered between a glass cover-slip surface and a handle (biotin group plus streptavidin), and a...5, 2008. H. P. Lu, “Probing Single-Molecule Protein Conformational Dynamics in Enzymatic Reactions,” Single-Molecule Biophysics Meeting, Aspen

  17. Peptide-independent stabilization of MHC class I molecules breaches cellular quality control.

    PubMed

    Hein, Zeynep; Uchtenhagen, Hannes; Abualrous, Esam Tolba; Saini, Sunil Kumar; Janßen, Linda; Van Hateren, Andy; Wiek, Constanze; Hanenberg, Helmut; Momburg, Frank; Achour, Adnane; Elliott, Tim; Springer, Sebastian; Boulanger, Denise

    2014-07-01

    The intracellular trafficking of major histocompatibility complex class I (MHC-I) proteins is directed by three quality control mechanisms that test for their structural integrity, which is correlated to the binding of high-affinity antigenic peptide ligands. To investigate which molecular features of MHC-I these quality control mechanisms detect, we have followed the hypothesis that suboptimally loaded MHC-I molecules are characterized by their conformational mobility in the F-pocket region of the peptide-binding site. We have created a novel variant of an MHC-I protein, K(b)-Y84C, in which two α-helices in this region are linked by a disulfide bond that mimics the conformational and dynamic effects of bound high-affinity peptide. K(b)-Y84C shows a remarkable increase in the binding affinity to its light chain, beta-2 microglobulin (β2m), and bypasses all three cellular quality control steps. Our data demonstrate (1) that coupling between peptide and β2m binding to the MHC-I heavy chain is mediated by conformational dynamics; (2) that the folded conformation of MHC-I, supported by β2m, plays a decisive role in passing the ER-to-cell-surface transport quality controls; and (3) that β2m association is also tested by the cell surface quality control that leads to MHC-I endocytosis.

  18. Coherent control of the electron quantum paths for the generation of single ultrashort atto second laser pulse

    SciTech Connect

    Liu, I-Lin; Li, Peng-Cheng; Chu, Shih-I

    2011-09-15

    We report a mechanism and a realizable approach for the coherent control of the generation of an isolated and ultrashort atto second (as) laser pulse from atoms by optimizing the two-color laser fields with a proper time delay. Optimizing the laser pulse shape allows the control of the electron quantum paths and enables high-harmonic generation from the long- and short-trajectory electrons to be enhanced and split near the cutoff region. In addition, it delays the long-trajectory electron emission time and allows the production of extremely short atto second pulses in a relatively narrow time duration. As a case study, we show that an isolated 30 as pulse with a bandwidth of 127 eV can be generated directly from the contribution of long-trajectory electrons alone.

  19. Coherent control of injection currents in high-quality films of Bi{sub 2}Se{sub 3}

    SciTech Connect

    Bas, D. A.; Vargas-Velez, K.; Babakiray, S.; Johnson, T. A.; Borisov, P.; Stanescu, T. D.; Lederman, D.; Bristow, A. D.

    2015-01-26

    Films of the topological insulator Bi{sub 2}Se{sub 3} are grown by molecular beam epitaxy with in-situ reflection high-energy electron diffraction. The films are shown to be high-quality by X-ray reflectivity and diffraction and atomic-force microscopy. Quantum interference control of photocurrents is observed by excitation with harmonically related pulses and detected by terahertz radiation. The injection current obeys the expected excitation irradiance dependence, showing linear dependence on the fundamental pulse irradiance and square-root irradiance dependence of the frequency-doubled optical pulses. The injection current also follows a sinusoidal relative-phase dependence between the two excitation pulses. These results confirm the third-order nonlinear optical origins of the coherently controlled injection current. Experiments are compared to a tight-binding band structure to illustrate the possible optical transitions that occur in creating the injection current.

  20. Optical system design and experimental evaluation of a coherent Doppler wind Lidar system for the predictive control of wind turbine

    NASA Astrophysics Data System (ADS)

    Shinohara, Leilei; Tauscher, Julian Asche; Beuth, Thorsten; Heussner, Nico; Fox, Maik; Babu, Harsha Umesh; Stork, Wilhelm

    2014-09-01

    The control of wind turbine blade pitch systems by Lidar assisted wind speed prediction has been proposed to increase the electric power generation and reduce the mechanical fatigue load on wind turbines. However, the sticking point of such Lidar systems is the price. Hence, our objective is to develop a more cost efficient Lidar system to support the pitch control of horizontal axis wind turbines and therefore to reduce the material requirement, lower the operation and maintenance costs and decrease the cost of wind energy in the long term. Compared to the state of the art Lidar systems, a laser with a shorter coherence length and a corresponding fiber delay line is introduced for reducing the costs. In this paper we present the experimental evaluation of different sending and receiving optics designs for such a system from a free space laboratory setup.

  1. Probability density function formalism for optical coherence tomography signal analysis: a controlled phantom study.

    PubMed

    Weatherbee, Andrew; Sugita, Mitsuro; Bizheva, Kostadinka; Popov, Ivan; Vitkin, Alex

    2016-06-15

    The distribution of backscattered intensities as described by the probability density function (PDF) of tissue-scattered light contains information that may be useful for tissue assessment and diagnosis, including characterization of its pathology. In this Letter, we examine the PDF description of the light scattering statistics in a well characterized tissue-like particulate medium using optical coherence tomography (OCT). It is shown that for low scatterer density, the governing statistics depart considerably from a Gaussian description and follow the K distribution for both OCT amplitude and intensity. The PDF formalism is shown to be independent of the scatterer flow conditions; this is expected from theory, and suggests robustness and motion independence of the OCT amplitude (and OCT intensity) PDF metrics in the context of potential biomedical applications.

  2. Coherence limits and chirp control in long pulse free electron laser oscillator

    NASA Astrophysics Data System (ADS)

    Socol, Y.; Gover, A.; Eliran, A.; Volshonok, M.; Pinhasi, Y.; Kapilevich, B.; Yahalom, A.; Lurie, Y.; Kanter, M.; Einat, M.; Litvak, B.

    2005-08-01

    We report experimental studies of the spectral linewidth and chirp characteristics of the mm-wave rf radiation of the Israeli Electrostatic-Accelerator free electron laser (EA-FEL), along with theory and numerical simulations. The simulations, matching the experimental data, were carried out using a space-frequency-domain model. EA-FELs have the capacity to generate long pulses of tens microseconds and more, that in principle can be elongated indefinitely (cw operation). Since a cold beam FEL is by nature a “homogeneously broadened laser,” EA-FEL can operate, unlike other kinds of FELs, at a single longitudinal mode (single frequency). This allows the generation of very coherent radiation. The current status of the Israeli Tandem Electrostatic-Accelerator FEL, which is based on an electrostatic Van de Graaff accelerator, allows the generation of pulses of tens microseconds duration. It has been operated recently past saturation, and produced single-mode coherent radiation of record narrow inherent relative linewidth ˜Δf/f=10-6 at frequencies near 100 GHz. A frequency chirp was observed during the pulses of tens of microseconds (0.3-0.5MHz/ms). This is essentially a drifting “frequency-pulling effect,” associated with the accelerator voltage drop during the pulse. Additionally, damped relaxation of the FEL oscillator was experimentally measured at the beginning and the end of the lasing pulse, in good correspondence to our theory and numerical simulations. We propose using the chirped signal of the pulsed EA-FEL for single pulse sweep spectroscopy of very fine resolution. The characteristics of this application are analyzed based on the experimental data.

  3. Observation and coherent control of interface-induced electronic resonances in a field-effect transistor.

    PubMed

    Tenorio-Pearl, J O; Herbschleb, E D; Fleming, S; Creatore, C; Oda, S; Milne, W I; Chin, A W

    2017-02-01

    Electronic defect states at material interfaces provide highly deleterious sources of noise in solid-state nanostructures, and even a single trapped charge can qualitatively alter the properties of short one-dimensional nanowire field-effect transistors (FET) and quantum bit (qubit) devices. Understanding the dynamics of trapped charge is thus essential for future nanotechnologies, but their direct detection and manipulation is rather challenging. Here, a transistor-based set-up is used to create and probe individual electronic defect states that can be coherently driven with microwave (MW) pulses. Strikingly, we resolve a large number of very high quality (Q ∼ 1 × 10(5)) resonances in the transistor current as a function of MW frequency and demonstrate both long decoherence times (∼1 μs-40 μs) and coherent control of the defect-induced dynamics. Efficiently characterizing over 800 individually addressable resonances across two separate defect-hosting materials, we propose that their properties are consistent with weakly driven two-level systems.

  4. Emissions enhancement in a pump-coupling V-type coherently controlled four-level atomic system

    NASA Astrophysics Data System (ADS)

    Pentaris, D.; Papademetriou, G.; Efthimiopoulos, T.; Merlemis, N.; Lyras, A.

    2013-12-01

    The nonlinear interaction of a four-level potassium system with a strong pump and a weak coupling laser is investigated. A strong pump pulse excites the two-photon transition ?, causing prompt parametric emissions along the path-1 ? and delayed emissions in the second available de-excitation path-2 ?. A weak coupling pulse is introduced to coherently excite either the transition ? (path-1) or the ? one (path-2) in a V-type scheme. Results are presented for the emissions generated under the combined action of the pump-coupling pulses as a function of their delay for certain peak pulse intensities and coherence relaxation times (CRTs) related to dephasing collisions. We find that emissions in path-1 are considerably enhanced for negative delays (counterintuitive pulse sequence) of the order of the CRT. An approach is suggested for the estimation of CRTs. Emissions in path-2 are enhanced and temporally shifted, suggesting an approach to control this path by varying the pulse delay.

  5. Controlled Modification of Superconductivity in Epitaxial Atomic Layer-Organic Molecule Heterostructures.

    PubMed

    Yoshizawa, Shunsuke; Minamitani, Emi; Vijayaraghavan, Saranyan; Mishra, Puneet; Takagi, Yasumasa; Yokoyama, Toshihiko; Oba, Hiroaki; Nitta, Jun; Sakamoto, Kazuyuki; Watanabe, Satoshi; Nakayama, Tomonobu; Uchihashi, Takashi

    2017-04-12

    Self-assembled organic molecules can potentially be an excellent source of charge and spin for two-dimensional (2D) atomic-layer superconductors. Here we investigate 2D heterostructures based on In atomic layers epitaxially grown on Si and highly ordered metal-phthalocyanine (MPc, M = Mn, Cu) through a variety of techniques: scanning tunneling microscopy, electron transport measurements, angle-resolved photoemission spectroscopy, X-ray magnetic circular dichroism, and ab initio calculations. We demonstrate that the superconducting transition temperature (Tc) of the heterostructures can be modified in a controllable manner. Particularly, the substitution of the coordinated metal atoms from Mn to Cu is found to reverse the Tc shift from negative to positive directions. This distinctive behavior is attributed to a competition of charge and spin effects, the latter of which is governed by the directionality of the relevant d-orbitals. The present study shows the effectiveness of molecule-induced surface doping and the significance of microscopic understanding of the molecular states in these 2D heterostructures.

  6. Controlling the fluorescence of ordinary oxazine dyes for single-molecule switching and superresolution microscopy

    PubMed Central

    Vogelsang, Jan; Cordes, Thorben; Forthmann, Carsten; Steinhauer, Christian; Tinnefeld, Philip

    2009-01-01

    Fluorescent molecular switches have widespread potential for use as sensors, material applications in electro-optical data storages and displays, and superresolution fluorescence microscopy. We demonstrate that adjustment of fluorophore properties and environmental conditions allows the use of ordinary fluorescent dyes as efficient single-molecule switches that report sensitively on their local redox condition. Adding or removing reductant or oxidant, switches the fluorescence of oxazine dyes between stable fluorescent and nonfluorescent states. At low oxygen concentrations, the off-state that we ascribe to a radical anion is thermally stable with a lifetime in the minutes range. The molecular switches show a remarkable reliability with intriguing fatigue resistance at the single-molecule level: Depending on the switching rate, between 400 and 3,000 switching cycles are observed before irreversible photodestruction occurs. A detailed picture of the underlying photoinduced and redox reactions is elaborated. In the presence of both reductant and oxidant, continuous switching is manifested by “blinking” with independently controllable on- and off-state lifetimes in both deoxygenated and oxygenated environments. This “continuous switching mode” is advantageously used for imaging actin filament and actin filament bundles in fixed cells with subdiffraction-limited resolution. PMID:19433792

  7. Topographical control of multiple cell adhesion molecules for traction force microscopy.

    PubMed

    Polio, Samuel R; Parameswaran, Harikrishnan; Canović, Elizabeth P; Gaut, Carolynn M; Aksyonova, Diana; Stamenović, Dimitrije; Smith, Michael L

    2014-03-01

    Cellular traction forces are important quantitative measures in cell biology as they have provided much insight into cell behavior in contexts such as cellular migration, differentiation, and disease progression. However, the complex environment in vivo permits application of cell traction forces through multiple types of cell adhesion molecules. Currently available approaches to differentiate traction forces among multiple cell adhesion molecules are limited to specialized approaches to decouple cell-cell from cell-extracellular matrix (ECM) tractions. Here, we present a technique which uses indirect micropatterning onto a polyacrylamide gel to pattern multiple, spatially distinct fluorescently labeled ECM proteins, specifically gelatin and fibronectin (Fn), and confine the area to which cells can adhere. We found that cells interacting with both gelatin and Fn altered their traction forces significantly in comparison to cells on Fn-only substrates. This crosstalk interaction resulted in a decrease in overall traction forces on dual-patterned substrates as compared to cells on Fn-only substrates. This illustrates the unique need to study such interactions and demonstrates great potential in future studies in multi-ligand environments. Current micropatterning techniques on glass can easily be adapted to present other protein classes, such as cadherins, while maintaining control of adhesion spacing, cell spread area, and stiffness, each of which are important regulators of cell mechanobiology.

  8. Chemical dynamics of vibrationally excited molecules: Controlling reactions in gases and on surfaces

    PubMed Central

    Crim, F. Fleming

    2008-01-01

    Experimental studies of the chemical reaction dynamics of vibrationally excited molecules reveal the ability of different vibrations to control the course of a reaction. This Perspective describes those studies for the prototypical reaction of vibrationally excited methane and its isotopologues in gases and on surfaces and looks to the prospects of similar studies in liquids. The influences of vibrational excitation on the CH bond cleavage in a single collision reaction with Cl and in dissociative adsorption on a Ni surface bear some striking similarities. Both reactions are bond-selective processes in which the initial preparation of a molecular eigenstate containing a large component of CH stretching results in preferential cleavage of that bond. It is possible to cleave either the CH bond or CD bond in the reaction of Cl with CH3D, CH2D2, or CHD3 and, similarly, to use initial excitation of the CH stretch to promote dissociation of CHD3 to CD3 and H on a Ni surface. Different vibrational modes, such as the symmetric and antisymmetric stretches in CH3D or CH4, lead to very different reactivities, and molecules with the symmetric stretching vibration excited can be as much as 10 times more reactive than ones with the antisymmetric stretch excited. The origin of this behavior lies in the change in the vibrational motion induced by the interaction with the atomic reaction partner or the surface. PMID:18765816

  9. Scalable coherent interface

    SciTech Connect

    Alnaes, K.; Kristiansen, E.H. ); Gustavson, D.B. ); James, D.V. )

    1990-01-01

    The Scalable Coherent Interface (IEEE P1596) is establishing an interface standard for very high performance multiprocessors, supporting a cache-coherent-memory model scalable to systems with up to 64K nodes. This Scalable Coherent Interface (SCI) will supply a peak bandwidth per node of 1 GigaByte/second. The SCI standard should facilitate assembly of processor, memory, I/O and bus bridge cards from multiple vendors into massively parallel systems with throughput far above what is possible today. The SCI standard encompasses two levels of interface, a physical level and a logical level. The physical level specifies electrical, mechanical and thermal characteristics of connectors and cards that meet the standard. The logical level describes the address space, data transfer protocols, cache coherence mechanisms, synchronization primitives and error recovery. In this paper we address logical level issues such as packet formats, packet transmission, transaction handshake, flow control, and cache coherence. 11 refs., 10 figs.

  10. Improving sensor response using reduced graphene oxide film transistor biosensor by controlling the adsorption of pyrene as an anchor molecule

    NASA Astrophysics Data System (ADS)

    Negishi, Ryota; Matsui, Yuji; Kobayashi, Yoshihiro

    2017-06-01

    Reduced graphene oxide (rGO) films functionalized with linker molecules that bind specific antibodies to the surface of their films are useful for biosensors based on field-effect transistors. Controlling the density of linker molecules on the rGO channel surface is a crucial issue for improving the sensor structure with the desired sensitivity and stability. In this study, ultraviolet-visible (UV-vis) absorption spectroscopy was utilized for the evaluation of the density of linker molecules adsorbed on the rGO and GO surfaces. We revealed that the density of adsorbed linker molecules on the rGO surface is dominated by oxygen-containing groups slightly remaining on the surfaces, rather than the restoration of the π-conjugated system in the graphitic structure of rGO films. We demonstrate that the difference in the density of adsorbed linker molecules on the rGO films significantly affects the sensitivity of sensor responses.

  11. Coherence, Complexity and Creativity

    NASA Astrophysics Data System (ADS)

    Arecchi, Fortunato Tito

    We review the ideas and experiments that established the onset of laser coherence beyond a suitable threshold. That threshold is the first of a chain of bifurcations in a non linear dynamics, leading eventually to deterministic chaos in lasers. In particular, the so called HC behavior has striking analogies with the electrical activity of neurons. Based on these considerations, we develop a dynamical model of neuron synchronization leading to coherent global perceptions. Synchronization implies a transitory control of neuron chaos. Depending on the time duration of this control, a cognitive agent has different amounts of awareness. Combining this with a stream of external inputs, one can point at an optimal use of internal resources, that is called cognitive creativity. While coherence is associated with long range correlations, complexity arises whenever an array of coupled dynamical systems displays multiple paths of coherence. What is the relation among the three concepts in the title? While coherence is associated with long range correlations, complexity arises whenever an array of coupled dynamical systems displays multiple paths of coherence. Creativity corresponds to a free selection of a coherence path within a complex nest. As sketched above, it seems dynamically related to chaos control.

  12. Insulator-protected mechanically controlled break junctions for measuring single-molecule conductance in aqueous environments

    NASA Astrophysics Data System (ADS)

    Muthusubramanian, N.; Galan, E.; Maity, C.; Eelkema, R.; Grozema, F. C.; van der Zant, H. S. J.

    2016-07-01

    We present a method to fabricate insulated gold mechanically controlled break junctions (MCBJ) by coating the metal with a thin layer of aluminum oxide using plasma enhanced atomic layer deposition. The Al2O3 thickness deposited on the MCBJ devices was varied from 2 to 15 nm to test the suppression of leakage currents in deionized water and phosphate buffered saline. Junctions coated with a 15 nm thick oxide layer yielded atomically sharp electrodes and negligible conductance counts in the range of 1 to 10-4 G0 (1 G0 = 77 μS), where single-molecule conductances are commonly observed. The insulated devices were used to measure the conductance of an amphiphilic oligophenylene ethynylene derivative in deionized water.

  13. Enhancement of ultracold molecule formation by local control in the nanosecond regime

    DOE PAGES

    Carini, J. L.; Kallush, S.; Kosloff, R.; ...

    2015-02-01

    We describe quantum simulations of ultracold 87Rb2 molecule formation using photoassociation (PA) with nanosecond-time-scale pulses of frequency chirped light. In particular, we compare the case of a linear chirp to one where the frequency evolution is optimized by local control (LC) of the phase, and find that LC can provide a significant enhancement. The resulting optimal frequency evolution corresponds to a rapid jump from the PA absorption resonance to a downward transition to a bound level of the lowest triplet state. We also consider the case of two frequencies and investigate interference effects. The assumed chirp parameters should be achievablemore » with nanosecond pulse shaping techniques and are predicted to provide a significant enhancement over recent experiments with linear chirps.« less

  14. Enhancement of VUV and EUV generation by field-controlled resonance structures of diatomic molecules

    NASA Astrophysics Data System (ADS)

    Heslar, John; Telnov, Dmitry A.; Chu, Shih-I.

    2016-06-01

    Below- and near-threshold harmonic generation provides a potential approach to achieve a high conversion efficiency of vacuum-ultraviolet and extreme-ultraviolet sources for the advancement of spectroscopy. Here, we perform a time-dependent density functional theory study for the nonperturbative treatment of below- and near-threshold harmonic generation of CO and N2 diatomic molecules subject to short near-infrared laser pulses and aligned parallel to the laser field polarization. We find that with the use of different driving laser pulse shapes, we can control and enhance harmonic generation through the excited-state resonance structures. Depending on the pulse shape, the enhancement can reach five to seven orders of magnitude as compared to the reference sine-squared laser pulse of the same duration. The results for different driving laser intensities are also presented and discussed in detail.

  15. Enhancement of VUV and EUV generation by field-controlled resonance structures of diatomic molecules

    NASA Astrophysics Data System (ADS)

    Heslar, John; Telnov, Dmitry A.; Chu, Shih-I.

    2016-05-01

    Below- and near-threshold harmonic generation provides a potential approach to achieve a high conversion efficiency of vacuum-ultraviolet and extreme-ultraviolet sources for the advancement of spectroscopy. Here we perform an all-electron time-dependent density functional theory (TDDFT) study for the nonperturbative treatment of below- and near-threshold harmonic generation of CO and N2 diatomic molecules subject to short near-infrared laser pulses and aligned parallel to the laser field polarization. We find that with the use of different driving laser pulse shapes we can control and enhance harmonic generation through the excited state resonance structures. Our analysis reveals several novel features where the HHG signal is enhanced, boosting the conversion efficiency on the microscopic level. Depending on the pulse shape, the enhancement can reach 5 to 7 orders of magnitude as compared to the reference sine-squared laser pulse of the same duration. This work was partially supported by DOE.

  16. Insulator-protected mechanically controlled break junctions for measuring single-molecule conductance in aqueous environments

    SciTech Connect

    Muthusubramanian, N.; Zant, H. S. J. van der; Galan, E.; Maity, C.; Eelkema, R.; Grozema, F. C.

    2016-07-04

    We present a method to fabricate insulated gold mechanically controlled break junctions (MCBJ) by coating the metal with a thin layer of aluminum oxide using plasma enhanced atomic layer deposition. The Al{sub 2}O{sub 3} thickness deposited on the MCBJ devices was varied from 2 to 15 nm to test the suppression of leakage currents in deionized water and phosphate buffered saline. Junctions coated with a 15 nm thick oxide layer yielded atomically sharp electrodes and negligible conductance counts in the range of 1 to 10{sup −4} G{sub 0} (1 G{sub 0} = 77 μS), where single-molecule conductances are commonly observed. The insulated devices were used to measure the conductance of an amphiphilic oligophenylene ethynylene derivative in deionized water.

  17. Biosolar cells: global artificial photosynthesis needs responsive matrices with quantum coherent kinetic control for high yield

    PubMed Central

    Purchase, R. L.; de Groot, H. J. M.

    2015-01-01

    This contribution discusses why we should consider developing artificial photosynthesis with the tandem approach followed by the Dutch BioSolar Cells consortium, a current operational paradigm for a global artificial photosynthesis project. We weigh the advantages and disadvantages of a tandem converter against other approaches, including biomass. Owing to the low density of solar energy per unit area, artificial photosynthetic systems must operate at high efficiency to minimize the land (or sea) area required. In particular, tandem converters are a much better option than biomass for densely populated countries and use two photons per electron extracted from water as the raw material into chemical conversion to hydrogen, or carbon-based fuel when CO2 is also used. For the average total light sum of 40 mol m−2 d−1 for The Netherlands, the upper limits are many tons of hydrogen or carbon-based fuel per hectare per year. A principal challenge is to forge materials for quantitative conversion of photons to chemical products within the physical limitation of an internal potential of ca 2.9 V. When going from electric charge in the tandem to hydrogen and back to electricity, only the energy equivalent to 1.23 V can be stored in the fuel and regained. A critical step is then to learn from nature how to use the remaining difference of ca 1.7 V effectively by triple use of one overpotential for preventing recombination, kinetic stabilization of catalytic intermediates and finally generating targeted heat for the release of oxygen. Probably the only way to achieve this is by using bioinspired responsive matrices that have quantum–classical pathways for a coherent conversion of photons to fuels, similar to what has been achieved by natural selection in evolution. In appendix A for the expert, we derive a propagator that describes how catalytic reactions can proceed coherently by a convergence of time scales of quantum electron dynamics and classical nuclear dynamics

  18. Biosolar cells: global artificial photosynthesis needs responsive matrices with quantum coherent kinetic control for high yield.

    PubMed

    Purchase, R L; de Groot, H J M

    2015-06-06

    This contribution discusses why we should consider developing artificial photosynthesis with the tandem approach followed by the Dutch BioSolar Cells consortium, a current operational paradigm for a global artificial photosynthesis project. We weigh the advantages and disadvantages of a tandem converter against other approaches, including biomass. Owing to the low density of solar energy per unit area, artificial photosynthetic systems must operate at high efficiency to minimize the land (or sea) area required. In particular, tandem converters are a much better option than biomass for densely populated countries and use two photons per electron extracted from water as the raw material into chemical conversion to hydrogen, or carbon-based fuel when CO2 is also used. For the average total light sum of 40 mol m(-2) d(-1) for The Netherlands, the upper limits are many tons of hydrogen or carbon-based fuel per hectare per year. A principal challenge is to forge materials for quantitative conversion of photons to chemical products within the physical limitation of an internal potential of ca 2.9 V. When going from electric charge in the tandem to hydrogen and back to electricity, only the energy equivalent to 1.23 V can be stored in the fuel and regained. A critical step is then to learn from nature how to use the remaining difference of ca 1.7 V effectively by triple use of one overpotential for preventing recombination, kinetic stabilization of catalytic intermediates and finally generating targeted heat for the release of oxygen. Probably the only way to achieve this is by using bioinspired responsive matrices that have quantum-classical pathways for a coherent conversion of photons to fuels, similar to what has been achieved by natural selection in evolution. In appendix A for the expert, we derive a propagator that describes how catalytic reactions can proceed coherently by a convergence of time scales of quantum electron dynamics and classical nuclear dynamics. We

  19. Coherent hybrid electromagnetic field imaging

    DOEpatents

    Cooke, Bradly J.; Guenther, David C.

    2008-08-26

    An apparatus and corresponding method for coherent hybrid electromagnetic field imaging of a target, where an energy source is used to generate a propagating electromagnetic beam, an electromagnetic beam splitting means to split the beam into two or more coherently matched beams of about equal amplitude, and where the spatial and temporal self-coherence between each two or more coherently matched beams is preserved. Two or more differential modulation means are employed to modulate each two or more coherently matched beams with a time-varying polarization, frequency, phase, and amplitude signal. An electromagnetic beam combining means is used to coherently combine said two or more coherently matched beams into a coherent electromagnetic beam. One or more electromagnetic beam controlling means are used for collimating, guiding, or focusing the coherent electromagnetic beam. One or more apertures are used for transmitting and receiving the coherent electromagnetic beam to and from the target. A receiver is used that is capable of square-law detection of the coherent electromagnetic beam. A waveform generator is used that is capable of generation and control of time-varying polarization, frequency, phase, or amplitude modulation waveforms and sequences. A means of synchronizing time varying waveform is used between the energy source and the receiver. Finally, a means of displaying the images created by the interaction of the coherent electromagnetic beam with target is employed.

  20. Optically controlled coherent X-ray radiations from photo-excited nanotubes

    NASA Astrophysics Data System (ADS)

    Shin, Young-Min

    2017-09-01

    Relativistic electrons propagating through a plasmonic medium such as photo-excited plasma channels with negative permittivities undergo betatron motions, emitting photons at oscillating resonance modes. The similar betatron radiation can be generated in X-ray regimes from electrons transported through optically pumped carbon nanotubes (CNTs). The X-ray radiation condition of 0.5 and 6 MeV electrons phase-matched with plasmonic waves in CNTs is analyzed with a theoretical model of the CNT dispersion relation. Based on the dispersion analysis, radiation intensities and the brilliance of the coherent X-ray source averaged over the pulse duration are estimated using a typical range of system parameters of conventional electron sources and tabletop femtosecond lasers. The assessment indicates that the average brilliance of the harmonic radiation can reach 1010-1013 photons/s/mm2/mrad2/0.1%BW with 0.5-6 MeV electrons and X-ray energy up to a few keV.