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Sample records for molecules coherent control

  1. Towards coherent control of ultracold molecule formation

    NASA Astrophysics Data System (ADS)

    Brown, Benjamin L.

    This thesis details experimental and theoretical investigations advancing the use of closed-loop coherent control for state-selective ultracold molecule formation in a magneto-optical trap (MOT). To date, no efficient scheme to produce a robust sample of ultracold (T ≤ 1 mK) molecules in arbitrarily-prescribed bound states has been demonstrated. The research presented here addresses this problem through the first experimental union of the fields of ultracold matter and ultrafast coherent control. A promising technique for producing ultracold molecules is to synthesize them directly from trapped ultracold atoms via photoassociation. This thesis explores a new extension of this approach: the application of closed-loop coherent control techniques employing broadband femtosecond optical pulses to enhance the efficiency and state-selectivity of photoassociative ultracold molecule formation. The experiments presented here studied the effects of chirped femtosecond pulses on the formation of ultracold triplet a3 S+u molecules in 85Rb and 87Rb MOTs. The application of femtosecond pulses suppressed, rather than increased, the formation of 85Rb2 and 87Rb2 a3 S+u molecules in contrast to comparable cw illumination and background formation rates. Positively chirped pulses were more efficient than non-chirped pulses of equivalent energy and spectral character at stimulating this quenching phenomenon. These results indicated that this suppression effect was coherent in nature, suggesting that coherent control is likely to be useful for manipulating the dynamics of ultracold quantum molecular gases. Time-dependent two-surface model simulations were performed to study several intuitive dynamical schemes employing femtosecond optical pulses to stimulate the formation of ground singlet X1 S+g molecules. These simulations focused on optical manipulation of the collision process at short-to-intermediate range (R < 50A), where stabilization of ultracold molecules to deeply bound

  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 optically induced birefringence in azoaromatic molecules

    SciTech Connect

    Mendonca, C. R.; Neves, U. M.; Guedes, I.; Zilio, S. C.; Misoguti, L.

    2006-08-15

    Here we present the coherent control of two-photon induced birefringence in polymeric films containing Disperse Red 13 (DR13) azoaromatic molecules. Such control is achieved by enhancing and reducing the azochromophor cis-trans photoisomerization rate, which leads to the molecular orientation, inducing the birefringence. The dependence on chirp and phase mask of the birefringence signal was studied and modeled.

  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. Coherent Microwave Control of Ultracold 23Na 4K Molecules

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

    We demonstrate coherent microwave control of rotational and hyperfine states of trapped, ultracold, and chemically stable 23Na 40K molecules. Starting with all molecules in the absolute rovibrational and hyperfine ground state, we study rotational transitions in combined magnetic and electric fields and explain the rich hyperfine structure. Following the transfer of the entire molecular ensemble into a single hyperfine level of the first rotationally excited state, J =1 , we observe lifetimes of more than 3 s, comparable to those in the rovibrational ground state, J =0 . Long-lived ensembles and full quantum state control are prerequisites for the use of ultracold molecules in quantum simulation, precision measurements, and quantum information processing.

  6. Attosecond Coherent Control of the Photo-Dissociation of Oxygen Molecules

    NASA Astrophysics Data System (ADS)

    Sturm, Felix; Ray, Dipanwita; Wright, Travis; Shivaram, Niranjan; Bocharova, Irina; Slaughter, Daniel; Ranitovic, Predrag; Belkacem, Ali; Weber, Thorsten

    2016-05-01

    Attosecond Coherent Control has emerged in recent years as a technique to manipulate the absorption and ionization in atoms as well as the dissociation of molecules on an attosecond time scale. Single attosecond pulses and attosecond pulse trains (APTs) can coherently excite multiple electronic states. The electronic and nuclear wave packets can then be coupled with a second pulse forming multiple interfering quantum pathways. We have built a high flux extreme ultraviolet (XUV) light source delivering APTs based on HHG that allows to selectively excite neutral and ion states in molecules. Our beamline provides spectral selectivity and attosecond interferometric control of the pulses. In the study presented here, we use APTs, generated by High Harmonic Generation in a high flux extreme ultraviolet light source, to ionize highly excited states of oxygen molecules. We identify the ionization/dissociation pathways revealing vibrational structure with ultra-high resolution ion 3D-momentum imaging spectroscopy. Furthermore, we introduce a delay between IR pulses and XUV/IR pulses to constructively or destructively interfere the ionization and dissociation pathways, thus, enabling the manipulation of both the O2+and the O+ ion yields with attosecond precision. Supported by DOE under Contract No. DE-AC02-05CH11231.

  7. Rotational coherence imaging and control for CN molecules through time-frequency resolved coherent anti-Stokes Raman scattering.

    PubMed

    Lindgren, Johan; Hulkko, Eero; Pettersson, Mika; Kiljunen, Toni

    2011-12-14

    Numerical wave packet simulations are performed for studying coherent anti-Stokes Raman scattering (CARS) for CN radicals. Electronic coherence is created by femtosecond laser pulses between the X(2)Σ and B(2)Σ states. Due to the large energy separation of vibrational states, the wave packets are superpositions of rotational states only. This allows for a specially detailed inspection of the second- and third-order coherences by a two-dimensional imaging approach. We present the time-frequency domain images to illustrate the intra- and intermolecular interferences, and discuss the procedure to rationally control and experimentally detect the interferograms in solid Xe environment. PMID:22168710

  8. Coherent control of interfering wave packets in dissociating HD+ molecules: the role of phase and delay time

    NASA Astrophysics Data System (ADS)

    Qin, Chaochao; Zhang, Lili; Qiu, Xuejun; Zhang, Xianzhou; Liu, Yufang

    2016-02-01

    The coherent control of interference between dissociating wave packets of the HD+ molecules generated by a pair of time-delayed and phase-locked femtosecond laser pulses is theoretically studied by using the time-dependent quantum wave packet method. The density function in both coordinate and momentum representation are presented and discussed. It is demonstrated that the interference pattern is observed in both coordinate and momentum density functions. The interference undergoes a π-phase shift when the delay time between the two phase-locked femtosecond laser pulses is changed by half an optical period. In particular, the number of interference fringes, the fringe spacing in the R-dependent density distribution |ψ(R)|2, and the modulation period of the energy-dependent distribution of the fragments P(E) can be tuned by two phase-locked femtosecond pulses.

  9. Wave-Packet and Coherent Control Dynamics

    NASA Astrophysics Data System (ADS)

    Ohmori, Kenji

    2009-05-01

    This review summarizes progress in coherent control as well as relevant recent achievements, highlighting, among several different schemes of coherent control, wave-packet interferometry (WPI). WPI is a fundamental and versatile scenario used to control a variety of quantum systems with a sequence of short laser pulses whose relative phase is finely adjusted to control the interference of electronic or nuclear wave packets (WPs). It is also useful in retrieving quantum information such as the amplitudes and phases of eigenfunctions superposed to generate a WP. Experimental and theoretical efforts to retrieve both the amplitude and phase information are recounted. This review also discusses information processing based on the eigenfunctions of atoms and molecules as one of the modern and future applications of coherent control. The ultrafast coherent control of ultracold atoms and molecules and the coherent control of complex systems are briefly discussed as future perspectives.

  10. Coherent control of metamaterials

    NASA Astrophysics Data System (ADS)

    Chakrabarti, Sangeeta; Ramakrishna, S. Anantha; Wanare, Harshawardhan

    2009-08-01

    We theoretically demonstrate the possibility of dynamically controlling the response of metamaterials at optical frequencies using the well known phenomenon of coherent control. Our results predict a variety of effects ranging from dramatic reduction of losses associated with the resonant response of metamaterials to switchable ultraslow to superluminal propagation of pulses governed by the magnetic field of the incident wave. These effects, generic to all metamaterials having a resonant response, involve embedding the metamaterial in resonant dispersive coherent atomic/molecular media. These effects may be utilized for narrow band switching applications and detectors for radiation below predetermined cut-off frequencies.

  11. Coherent control of plasma dynamics.

    PubMed

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

    2015-01-01

    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. PMID:25975737

  12. 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

  13. 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.

  14. 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.

  15. Coherent control near metallic nanostructures

    SciTech Connect

    Efimov, Ilya; Efimov, Anatoly

    2008-01-01

    We study coherent control in the vicinity of metallic nanostructures. Unlike in the case of control in gas or liquid phase, the collective response of electrons in a metallic nanostructure can significantly enhance different frequency components of the control field. This enhancement strongly depends on the geometry of the nanostructure and can substantially modify the temporal profile of the local control field. The changes in the amplitude and phase of the control field near the nanostructure are studied using linear response theory. The inverse problem of finding the external electromagnetic field to generate the desired local control field is considered and solved.

  16. Long Hyperfine Coherence Time of Ultracold Fermionic 23 Na40 K Molecules

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

    Ultracold molecules created and trapped at sub uK temperatures allow the full control of the molecule's external and internal degrees of freedom down to a single hyperfine state. In particular, an ensemble of molecules all initialized in a single rotational and hyperfine state can be prepared and be coherently addressed using microwave fields. In this talk, we report on the observation of long coherence time between two hyperfine states of fermionic 23 Na40 K molecules in the ro-vibronic ground state (v = 0 , J = 0). A direct two-photon microwave transition via the J = 1 state is used to prepare a superposition of two lowest hyperfine states of J = 0 , and we perform Ramsey spectroscopy as a direct probe of phase coherence between these states. The fermionic nature of the molecules and the lack of electronic angular momentum in the ro-vibronic ground state heavily suppress the decoherence from collisions and external fields, respectively, and we observe long coherence times upto 0.5 sec for this hyperfine superposition state. The observed long coherence time is a crucial step for applications of trapped dipolar molecules in quantum information processing schemes.

  17. 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.

  18. Control over coherent light fields enables multidimensional coherent spectroscopy and multispectral coherent control

    NASA Astrophysics Data System (ADS)

    Nelson, Keith A.

    2012-02-01

    Using a combination of spatial and temporal shaping of optical laser fields, fully coherent spectroscopy and coherent control can be carried out to high order from optical to THz spectral ranges. A single beam with a single femtosecond pulse can be transformed into multiple beams and multiple pulses, reconfigurably under computer control with no human alignment needed, retaining full phase coherence among all the noncollinear fields. This enables multiple-quantum 2D and 3D Fourier transform optical spectroscopy of excitons and exciton-polaritons in inorganic quantum wells and microcavities, in organic J-aggregate films, and in inorganic/organic hybrid structures, the results of which will be discussed. Spatiotemporal shaping also enables coherent control over THz phonon-polariton waves in ferroelectric crystals. The THz waves can be coherently superposed to reach extremely large field amplitudes both in the host crystals and in free space, and the fields can be further enhanced in dipolar antenna and metamaterial structures, enabling highly nonlinear coherent spectroscopy and coherent control in the THz regime. Results from solid, liquid, and gas phases, including multiple-quantum rotational coherences in molecular gases and THz-induced phase transitions in crystalline solids, will be presented. Prospects for further generalization of the approach all the way to the hard x-ray regime will be discussed.

  19. 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.

  20. Observing a coherent superposition of an atom and a molecule

    SciTech Connect

    Dowling, Mark R.; Bartlett, Stephen D.; Rudolph, Terry; Spekkens, Robert W.

    2006-11-15

    We demonstrate that it is possible, in principle, to perform a Ramsey-type interference experiment to exhibit a coherent superposition of a single atom and a diatomic molecule. This gedanken experiment, based on the techniques of Aharonov and Susskind [Phys. Rev. 155, 1428 (1967)], explicitly violates the commonly accepted superselection rule that forbids coherent superpositions of eigenstates of differing atom number. A Bose-Einstein condensate plays the role of a reference frame that allows for coherent operations analogous to Ramsey pulses. We also investigate an analogous gedanken experiment to exhibit a coherent superposition of a single boson and a fermion, violating the commonly accepted superselection rule forbidding coherent superpositions of states of differing particle statistics. In this case, the reference frame is realized by a multimode state of many fermions. This latter case reproduces all of the relevant features of Ramsey interferometry, including Ramsey fringes over many repetitions of the experiment. However, the apparent inability of this proposed experiment to produce well-defined relative phases between two distinct systems each described by a coherent superposition of a boson and a fermion demonstrates that there are additional, outstanding requirements to fully 'lift' the univalence superselection rule.

  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. Core hole-electron correlation in coherently coupled molecules.

    PubMed

    Scholz, M; Holch, F; Sauer, C; Wiessner, M; Schöll, A; Reinert, F

    2013-07-26

    We study the core hole-electron correlation in coherently coupled molecules by energy dispersive near edge x-ray absorption fine-structure spectroscopy. In a transient phase, which exists during the transition between two bulk arrangements, 1,4,5,8-naphthalene-tetracarboxylicacid-dianhydride multilayer films exhibit peculiar changes of the line shape and energy position of the x-ray absorption signal at the C K-edge with respect to the bulk and gas phase spectra. By a comparison to a theoretical model based on a coupling of transition dipoles, which is established for optical absorption, we demonstrate that the observed spectroscopic differences can be explained by an intermolecular delocalized core hole-electron pair. By applying this model we can furthermore quantify the coherence length of the delocalized core exciton. PMID:23931410

  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. 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.

  5. 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.

  6. 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.

  7. 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.

  8. Attosecond vacuum UV coherent control of molecular dynamics

    PubMed Central

    Ranitovic, Predrag; Hogle, Craig W.; Rivière, Paula; Palacios, Alicia; Tong, Xiao-Ming; Toshima, Nobuyuki; González-Castrillo, Alberto; Martin, Leigh; Martín, Fernando; Murnane, Margaret M.; Kapteyn, Henry

    2014-01-01

    High harmonic light sources make it possible to access attosecond timescales, thus opening up the prospect of manipulating electronic wave packets for steering molecular dynamics. However, two decades after the birth of attosecond physics, the concept of attosecond chemistry has not yet been realized; this is because excitation and manipulation of molecular orbitals requires precisely controlled attosecond waveforms in the deep UV, which have not yet been synthesized. Here, we present a unique approach using attosecond vacuum UV pulse-trains to coherently excite and control the outcome of a simple chemical reaction in a deuterium molecule in a non-Born–Oppenheimer regime. By controlling the interfering pathways of electron wave packets in the excited neutral and singly ionized molecule, we unambiguously show that we can switch the excited electronic state on attosecond timescales, coherently guide the nuclear wave packets to dictate the way a neutral molecule vibrates, and steer and manipulate the ionization and dissociation channels. Furthermore, through advanced theory, we succeed in rigorously modeling multiscale electron and nuclear quantum control in a molecule. The observed richness and complexity of the dynamics, even in this very simplest of molecules, is both remarkable and daunting, and presents intriguing new possibilities for bridging the gap between attosecond physics and attochemistry. PMID:24395768

  9. Optics of a gas of coherently spinning molecules.

    PubMed

    Steinitz, Uri; Prior, Yehiam; Averbukh, Ilya Sh

    2014-01-10

    We consider the optical properties of a gas of molecules that are brought to fast unidirectional spinning by a pulsed laser field. It is shown that a circularly polarized probe light passing through the medium inverts its polarization handedness and experiences a frequency shift controllable by the sense and the rate of molecular rotation. Our analysis is supported by two recent experiments on the laser-induced rotational Doppler effect in molecular gases and provides a good qualitative and quantitative description of the experimental observations. PMID:24483895

  10. Goniometer Control System for Coherent Bremsstrahlung Production

    SciTech Connect

    Acosta, Victor M

    2002-08-15

    A system for the generation of a high-intensity, quasi-monochromatic photon beam is discussed. The theory behind coherent bremsstrahlung photon beam production is analyzed and developed. The mechanics of a goniometer control system are presented. The software developed for remote control of the goniometer is also discussed. Finally, the results from various performance measurements are included.

  11. Controlling Casimir force via coherent driving field

    NASA Astrophysics Data System (ADS)

    Ahmad, Rashid; Abbas, Muqaddar; Ahmad, Iftikhar; Qamar, Sajid

    2016-04-01

    A four level atom-field configuration is used to investigate the coherent control of Casimir force between two identical plates made up of chiral atomic media and separated by vacuum of width d. The electromagnetic chirality-induced negative refraction is obtained via atomic coherence. The behavior of Casimir force is investigated using Casimir-Lifshitz formula. It is noticed that Casimir force can be switched from repulsive to attractive and vice versa via coherent control of the driving field. This switching feature provides new possibilities of using the repulsive Casimir force in the development of new emerging technologies, such as, micro-electro-mechanical and nano-electro-mechanical systems, i.e., MEMS and NEMS, respectively.

  12. Attosecond Coherent Control of Single and Double Photoionization in Argon

    NASA Astrophysics Data System (ADS)

    Hogle, C. W.; Tong, X. M.; Martin, L.; Murnane, M. M.; Kapteyn, H. C.; Ranitovic, P.

    2015-10-01

    Ultrafast high harmonic beams provide new opportunities for coherently controlling excitation and ionization processes in atoms, molecules, and materials on attosecond time scales by employing multiphoton two-pathway electron-wave-packet quantum interferences. Here we use spectrally tailored and frequency tuned vacuum and extreme ultraviolet harmonic combs, together with two phase-locked infrared laser fields, to show how the total single and double photoionization yields of argon can be coherently modulated by controlling the relative phases of both optical and electronic-wave-packet quantum interferences. This Letter is the first to apply quantum control techniques to double photoionization, which is a fundamental process where a single, high-energy photon ionizes two electrons simultaneously from an atom.

  13. Attosecond Coherent Control of Single and Double Photoionization in Argon.

    PubMed

    Hogle, C W; Tong, X M; Martin, L; Murnane, M M; Kapteyn, H C; Ranitovic, P

    2015-10-23

    Ultrafast high harmonic beams provide new opportunities for coherently controlling excitation and ionization processes in atoms, molecules, and materials on attosecond time scales by employing multiphoton two-pathway electron-wave-packet quantum interferences. Here we use spectrally tailored and frequency tuned vacuum and extreme ultraviolet harmonic combs, together with two phase-locked infrared laser fields, to show how the total single and double photoionization yields of argon can be coherently modulated by controlling the relative phases of both optical and electronic-wave-packet quantum interferences. This Letter is the first to apply quantum control techniques to double photoionization, which is a fundamental process where a single, high-energy photon ionizes two electrons simultaneously from an atom. PMID:26551112

  14. 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.

  15. Towards Coherent Control of Energetic Material Initiation

    NASA Astrophysics Data System (ADS)

    Greenfield, M. T.; McGrane, S. D.; Scharff, R. J.; Moore, D. S.

    2009-12-01

    We present direct optical initiation (DOI) of energetic materials using coherent control of localized energy deposition. DOI 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 QCI in condensed phase energetic materials requires optimally shaped ultrafast laser pulses to coherently guide the energy flow along 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 the 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).

  16. Coherent control in hybrid materials

    NASA Astrophysics Data System (ADS)

    Tian, Chao; Sukharev, Maxim; Malinovskaya, Svetlana

    2013-05-01

    A quickly growing field of hybrid materials is emerging on the base of latest advancements in nanoplasmonic science. Here one merges plasmonics with atomic and molecular physics considering systems comprised of quantum emitters and metal nano-structures. Such systems exhibit a wide variety of new phenomena. It has long been realized that quantum control could be successfully applied to optically active nano-systems. In this paper we explore the ideas of stimulated Raman adiabatic passage (STIRAP) applied to ensembles of atoms optically coupled to plasmonic systems. We demonstrate the implementation of STIRAP as a tool to control scattering, reflection, and transmission properties of hybrid systems. As an example we consider a core-shell silver nanowire with resonantly coupled layer of three-level atoms. A self-consistent model of Maxwell-Liouville-von Neumann equations is implemented that allows taking into account the collective effects between atoms. We show that both linear and nonlinear optical properties of atomic ensembles may be controlled by coupling to plasmonic nano-structures. The work is partially supported by NSF.

  17. Coherent control of photoionization of atomic barium

    NASA Astrophysics Data System (ADS)

    Yamazaki, Rekishu

    We present the results of our study on coherent control of photoionization of atomic barium. Our study focused on the understanding of the controllability, especially due to the effect of the coherent interaction between the atomic system and the laser field. The first half of the study investigates the mechanisms of the control behind the previously observed laser phase-insensitive product state control. The controllability of this excitation scheme, two-color two-photon resonantly enhanced excitation, was analyzed from two aspects, the role of ac Stark shift introduced by the strong laser field and the multi-pathway quantum mechanical interferences. We have analyzed the excitation scheme from the analysis of the photoelectron angular distribution measured using the excitation scheme and the monitoring of the intermediate state population. Analysis of the data as well as the numerical simulation showed clear understanding of the role of two mechanisms in the product state control reported. We also investigated the control of the phase lag during the product state control. We conducted the control of the phase lag in the study of asymmetric photoelectron angular distribution, which arises from the concurrent even-odd parity outgoing electron wave excitation. The phase lag was controlled in full range, 2pi, and the results were analyzed in terms of the role of autoionizing resonance structures as well as the nature of outgoing electron waves at different locations of the autoionizing resonances.

  18. Coherent spin control by electromagnetic vacuum fluctuations

    SciTech Connect

    Wang Jing; Liu Renbao; Zhu Bangfen; Sham, L. J.; Steel, D. G.

    2011-05-15

    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 {Lambda}-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.

  19. Using Feedback for Coherent Control of Quantum Systems

    NASA Astrophysics Data System (ADS)

    Weinacht, Thomas

    2001-05-01

    The control of atoms and molecules using coherent light fields has been a longstanding goal in chemical physics. I will discuss experiments which use a programmable pulse shaper to control the quantum state of electronic wavepackets in Rydberg atoms and nuclear dynamics in molecular liquids. The shape of Rydberg wavepackets was controlled by using tailored ultrafast laser pulses to excite a beam of cesium atoms. The quantum state of these atoms was measured using holographic techniques borrowed from optics. The experiments with molecular liquids involved the contstruction of an automated learning machine. A Genetic Algorithm directed the choice of shaped pulses which interacted with the molecular system inside a learning control loop. Analysis of successful pulse shapes that were found by the algorithm yield insight into the systems being controlled.

  20. 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.

  1. Coherence in Rydberg Atoms: Measurement and Control

    NASA Astrophysics Data System (ADS)

    Kutteruf, Mary

    We demonstrate a variety of techniques for measuring and controlling dephasing and decoherence in alkali metal Rydberg atom systems. Specifically, we investigate the coherence of the spin-orbit interaction in individual atoms and of dipole-dipole resonant energy exchange between pairs of atoms. Rydberg atoms are a good model system for exploring decoherence because they are sensitive to noise in their environments. The phase coherence of wave packets encoded on the fine-structure Rydberg states of lithium atoms is measured using a population echo and preserved using pulsed and continuous dynamic decoupling techniques. Pulsed electric fields toggle the spin-orbit coupling, repeatedly flipping the state vector, and preventing the slow acquisition of phase noise in a bang-bang scheme. Continuous dynamic decoupling is implemented by driving population between the relevant electronic states with a resonant rf field. The energy spacing between the levels is locked to the rf frequency as long as the Rabi rate is much greater than the dephasing rate. We demonstrate a technique which reduces the average relative velocity between interacting potassium Rydberg atoms, extending the atom transit time and allowing us to control when all resonant energy exchange interactions in the ensemble begin and end. Velocity reduction is achieved without the use of a chopper wheel by exciting a small cylinder of atoms and allowing them to thermally expand prior to tuning them into resonance. Resonant energy transfer is explored further in a nearly frozen rubidium Rydberg gas. We observe enhancement in the transition signal when the probability amplitudes acquired on opposite sides of the resonance interfere constructively compared to the population transferred when remaining on either side of the resonance. This enhancement reflects the coherence of the energy exchange interaction and decays over 10 us microseconds. The observed coherence time is much longer than previously measured

  2. Coherent control of Rydberg states in silicon.

    PubMed

    Greenland, P T; Lynch, S A; van der Meer, A F G; Murdin, B N; Pidgeon, C R; Redlich, B; Vinh, N Q; Aeppli, G

    2010-06-24

    Laser cooling and electromagnetic traps have led to a revolution in atomic physics, yielding dramatic discoveries ranging from Bose-Einstein condensation to the quantum control of single atoms. Of particular interest, because they can be used in the quantum control of one atom by another, are excited Rydberg states, where wavefunctions are expanded from their ground-state extents of less than 0.1 nm to several nanometres and even beyond; this allows atoms far enough apart to be non-interacting in their ground states to strongly interact in their excited states. For eventual application of such states, a solid-state implementation is very desirable. Here we demonstrate the coherent control of impurity wavefunctions in the most ubiquitous donor in a semiconductor, namely phosphorus-doped silicon. In our experiments, we use a free-electron laser to stimulate and observe photon echoes, the orbital analogue of the Hahn spin echo, and Rabi oscillations familiar from magnetic resonance spectroscopy. As well as extending atomic physicists' explorations of quantum phenomena to the solid state, our work adds coherent terahertz radiation, as a particularly precise regulator of orbitals in solids, to the list of controls, such as pressure and chemical composition, already familiar to materials scientists. PMID:20577211

  3. 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.

  4. Control of the entanglement between triple quantum dot molecule and its spontaneous emission fields via quantum entropy

    NASA Astrophysics Data System (ADS)

    Sahrai, M.; Arzhang, B.; Taherkhani, D.; Boroojerdi, V. Tahmoorian Askari

    2015-03-01

    The time evolution of the quantum entropy in a coherently driven triple quantum dot molecule is investigated. The entanglement of the quantum dot molecule and its spontaneous emission field is coherently controlled by the gate voltage and the rate of an incoherent pump field. The degree of entanglement between a triple quantum dot molecule and its spontaneous emission fields is decreased by increasing the tunneling parameter.

  5. Certifying the quantumness of a generalized coherent control scenario.

    PubMed

    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. PMID:25429946

  6. Certifying the quantumness of a generalized coherent control scenario

    NASA Astrophysics Data System (ADS)

    Scholak, Torsten; Brumer, Paul

    2014-11-01

    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.

  7. 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.

  8. 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.

  9. Spin-boson theory for charge photogeneration in organic molecules: Role of quantum coherence

    NASA Astrophysics Data System (ADS)

    Yao, Yao

    2015-01-01

    The charge photogeneration process in organic molecules is investigated by a quantum heat engine model, in which two molecules are modeled by a two-spin system sandwiched between two bosonic baths. The two baths represent the high-temperature photon emission source and the low-temperature phonon environment, respectively. We utilize the time-dependent density matrix renormalization group algorithm to investigate the quantum dynamics of the model. It is found that the transient energy current flowing through the two molecules exhibits two stages. In the first stage the energy current is of a coherent feature and represents the ultrafast delocalization of the charge-transfer state, and in the second stage a steady incoherent current is established. The power conversion efficiency is significantly high and may reach the maximum value of 93 % with optimized model parameters. The long-lived quantum entanglement between the two spins is found to be primarily responsible for the hyperefficiency.

  10. Coherent Control of the Optical Absorption in a Plasmonic Lattice Coupled to a Luminescent Layer.

    PubMed

    Pirruccio, Giuseppe; Ramezani, Mohammad; Rodriguez, Said Rahimzadeh-Kalaleh; Rivas, Jaime Gómez

    2016-03-11

    We experimentally demonstrate the coherent control, i.e., phase-dependent enhancement and suppression, of the optical absorption in an array of metallic nanoantennas covered by a thin luminescent layer. The coherent control is achieved by using two collinear, counterpropagating, and phase-controlled incident waves with wavelength matching the absorption spectrum of dye molecules coupled to the array. Symmetry arguments shed light on the relation between the relative phase of the incident waves and the excitation efficiency of the optical resonances of the system. This coherent control is associated with a phase-dependent distribution of the electromagnetic near fields in the structure which enables a significant reduction of the unwanted dissipation in the metallic structures. PMID:27015478

  11. Coherent Control of the Optical Absorption in a Plasmonic Lattice Coupled to a Luminescent Layer

    NASA Astrophysics Data System (ADS)

    Pirruccio, Giuseppe; Ramezani, Mohammad; Rodriguez, Said Rahimzadeh-Kalaleh; Rivas, Jaime Gómez

    2016-03-01

    We experimentally demonstrate the coherent control, i.e., phase-dependent enhancement and suppression, of the optical absorption in an array of metallic nanoantennas covered by a thin luminescent layer. The coherent control is achieved by using two collinear, counterpropagating, and phase-controlled incident waves with wavelength matching the absorption spectrum of dye molecules coupled to the array. Symmetry arguments shed light on the relation between the relative phase of the incident waves and the excitation efficiency of the optical resonances of the system. This coherent control is associated with a phase-dependent distribution of the electromagnetic near fields in the structure which enables a significant reduction of the unwanted dissipation in the metallic structures.

  12. Electron dynamics and its control in molecules

    NASA Astrophysics Data System (ADS)

    de Vivie-Riedle, Regina

    2014-03-01

    The accessibility of few femtosecond or even attoseconds pulses opens the door to direct observation of electron dynamics. The idea to steer chemical reactions by localization of electronic wavepackets is intriguing, since electrons are directly involved in bond breaking and formation. The formation of a localized electronic wavepacket requires the superposition of two or more appropriate electronic states. Its guidance is only possible within the coherence time of the system and has to be synchronized with the vibrational molecular motions. In theoretical studies we elucidate the role of electron wavepacket motion for the control of molecular processes. We give three examples with direct connection to experiments. From our analysis, we extract the systems requirements defining the time window for intramolecular electronic coherence, the basis for efficient control. Based on these findings we map out a photoreaction that allows direct control by guiding electronic wavepackets. The carrier envelope of a femtosecond few cycle IR pulse is the control parameter that steers the photoreaction through a conical intersection.

  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

    2015-01-01

    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

  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. 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

  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. Effects of spontaneously generated coherence on resonance fluorescence from triple quantum dot molecules

    NASA Astrophysics Data System (ADS)

    Tian, Si-Cong; Tong, Cun-Zhu; Wang, Chun-Liang; Ning, Yong-Qiang

    2014-09-01

    We investigate the spectrum of the resonance fluorescence from the lateral triple quantum dots controlled by voltage and obtain some interesting features such as controllable triple narrow peaks. In our system we use tunneling instead of coupling lasers, and the positions, widths and heights of the resonance fluorescence peaks can be controlled by tuning the tunneling couplings. We explain the observed spectrum with the transition properties of the dressed states generated by the coupling of the two tunneling and the laser field. These features can also be viewed as the effects of Spontaneously Generated Coherence between the close-lying levels in the dressed state picture of the tunneling couplings. And the scheme proposed here can permit the observation of Spontaneously Generated Coherence.

  18. Coherent controllers for optical-feedback cooling of quantum oscillators

    NASA Astrophysics Data System (ADS)

    Hamerly, Ryan; Mabuchi, Hideo

    2013-01-01

    We study the cooling performance of optical-feedback controllers for open optical and mechanical resonators in the linear quadratic Gaussian setting of stochastic control theory. We utilize analysis and numerical optimization of closed-loop models based on quantum stochastic differential equations to show that coherent control schemes, where we embed the resonator in an interferometer to achieve all-optical feedback, can outperform optimal measurement-based feedback control schemes in the quantum regime of low steady-state excitation number. These performance gains are attributed to the coherent controller's ability to simultaneously process both quadratures of an optical probe field without measurement or loss of fidelity, and may guide the design of coherent feedback schemes for more general problems of robust nonlinear and robust control.

  19. 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

  20. 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

  1. Coherent control of light interaction with graphene

    NASA Astrophysics Data System (ADS)

    Rao, Shraddha M.; Heitz, Julius J. F.; Roger, Thomas; Westerberg, Niclas; Faccio, Daniele

    2014-09-01

    We report the experimental observation of all-optical modulation of light in a graphene film. The graphene film is scanned across a standing wave formed by two counter-propagating laser beams in a Sagnac interferometer. Through a coherent absorption process the on-axis transmission is modulated with close to 80% efficiency. Furthermore we observe modulation of the scattered energy by mapping the off-axis scattered optical signal: scattering is minimized at a node of the standing wave pattern and maximized at an antinode. The results highlight the possibility to switch and modulate any given optical interaction with deeply sub-wavelength films.

  2. Coherent Population Trapping with Controlled Interparticle Interactions

    NASA Astrophysics Data System (ADS)

    Schempp, H.; Günter, G.; Hofmann, C. S.; Giese, C.; Saliba, S. D.; Depaola, B. D.; Amthor, T.; Weidemüller, M.; Sevinçli, S.; Pohl, T.

    2010-04-01

    We investigate coherent population trapping in a strongly interacting ultracold Rydberg gas. Despite the strong van der Waals interactions and interparticle correlations, we observe the persistence of a resonance with subnatural linewidth at the single-particle resonance frequency as we tune the interaction strength. This narrow resonance cannot be understood within a mean-field description of the strong Rydberg-Rydberg interactions. Instead, a many-body density matrix approach, accounting for the dynamics of interparticle correlations, is shown to reproduce the observed spectral features.

  3. Quantum-field coherent control: Preparation of broken-symmetry entangled states

    SciTech Connect

    Kral, Petr; Thanopulos, Ioannis; Shapiro, Moshe

    2005-08-15

    We show that entangled radiation-matter states with broken symmetries can be prepared by using nonclassical light in the coherent control techniques. We demonstrate the method by realizing the entanglement in degenerate continuum electronic momentum states of opposite directionality and discrete states of opposite handedness in chiral molecules. When the material system is excited simultaneously by classical light and quantum light in a state with several semiclassical phases, the interference conditions guide the system to such entangled radiation-matter states.

  4. Phase-controlled coherent population trapping in superconducting quantum circuits

    NASA Astrophysics Data System (ADS)

    Cheng, Guang-Ling; Wang, Yi-Ping; Chen, Ai-Xi

    2015-04-01

    We investigate the influences of the-applied-field phases and amplitudes on the coherent population trapping behavior in superconducting quantum circuits. Based on the interactions of the microwave fields with a single Δ-type three-level fluxonium qubit, the coherent population trapping could be obtainable and it is very sensitive to the relative phase and amplitudes of the applied fields. When the relative phase is tuned to 0 or π, the maximal atomic coherence is present and coherent population trapping occurs. While for the choice of π/2, the atomic coherence becomes weak. Meanwhile, for the fixed relative phase π/2, the value of coherence would decrease with the increase of Rabi frequency of the external field coupled with two lower levels. The responsible physical mechanism is quantum interference induced by the control fields, which is indicated in the dressed-state representation. The microwave coherent phenomenon is present in our scheme, which will have potential applications in optical communication and nonlinear optics in solid-state devices. Project supported by the National Natural Science Foundation of China (Grant Nos. 11165008 and 11365009), the Foundation of Young Scientist of Jiangxi Province, China (Grant No. 20142BCB23011), and the Scientific Research Foundation of Jiangxi Provincial Department of Education (Grant No. GJJ13348).

  5. Control of atomic spin squeezing via quantum coherence

    NASA Astrophysics Data System (ADS)

    Shao, Xuping; Ling, Yang; Yang, Xihua; Xiao, Min

    2016-06-01

    We propose a scheme to generate and control atomic spin squeezing via atomic coherence induced by the strong coupling and probe fields in the Λ-type electromagnetically-induced-transparency configuration in an atomic ensemble. Manipulation of squeezing of the two components in the plane orthogonal to the mean atomic spin direction and generation of nearly perfect squeezing in either component can be achieved by varying the relative intensities of the coupling and probe fields. This method provides a flexible and convenient way to create and control atomic spin squeezing, which may find potential applications in high-precision atomic-physics measurement, quantum coherent control, and quantum information processing.

  6. Frequency domain Fourier transform THz-EPR on single molecule magnets using coherent synchrotron radiation.

    PubMed

    Schnegg, Alexander; Behrends, Jan; Lips, Klaus; Bittl, Robert; Holldack, Karsten

    2009-08-21

    Frequency domain Fourier transform THz electron paramagnetic resonance (FD-FT THz-EPR) based on coherent synchrotron radiation (CSR) is presented as a novel tool to ascertain very large zero field splittings in transition metal ion complexes. A description of the FD-FT THz-EPR at the BESSY II storage ring providing CSR in a frequency range from 5 cm(-1) up to 40 cm(-1) at external magnetic fields from -10 T to +10 T is given together with first measurements on the single molecule magnet Mn(12)Ac where we studied DeltaM(S) = +/-1 spin transition energies as a function of the external magnetic field and temperature. PMID:19639156

  7. Broadband standoff detection of large molecules by mid-infrared active coherent laser spectrometry.

    PubMed

    Macleod, Neil A; Molero, Francisco; Weidmann, Damien

    2015-01-26

    A widely tunable active coherent laser spectrometer (ACLaS) has been demonstrated for standoff detection of broadband absorbers in the 1280 to 1318 cm-1 spectral region using an external cavity quantum cascade laser as a mid-infrared source. The broad tuning range allows detection and quantification of vapor phase molecules, such as dichloroethane, ethylene glycol dinitrate, and tetrafluoroethane. The level of confidence in molecular mixing ratios retrieved from interfering spectral measurements is assessed in a quantitative manner. A first qualitative demonstration of condensed phase chemical detection on nitroacetanilide has also been conducted. Detection performances of the broadband ACLaS have been placed in the context of explosive detection and compared to that obtained using distributed feedback quantum cascade lasers. PMID:25835851

  8. Coherent control of optical polarization effects in metamaterials.

    PubMed

    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

  9. 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

  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. 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

  12. Theory of coherent polarization anisotropy in time-resolved two-photon ionization of isolated molecules. Effects of Coriolis couplings

    NASA Astrophysics Data System (ADS)

    Sato, S.; Nomura, Y.; Fujimura, Y.

    1987-09-01

    Effects of vibration-rotation (Coriolis) couplings on the coherent polarization anisotropy are theoretically studied in a time-resolved two-photon ionization of a symmetric top molecule. This polarization anisotropy originates from a coherent excitation of the resonant rovibronic molecular eigenstates (rovibronic coherence) whose zeroth order states are mixed through the Coriolis coupling. Expressions for the time-dependent degree of polarization after the coherent excitation of the rovibronic states produced by the Coriolis coupling are derived as a function of the delay time in the pump-probe two-photon ionization. Model calculations of the time-dependent degree of polarization as well as the probabilities of the two-photon ionization are performed to demonstrate the Coriolis coupling effects in the low excess energy regions of the resonant intermediate state. It is shown that oscillatory behaviors in the time-dependent degree of polarization should be observed as a result of the creation of the rovibronic coherence. It is demonstrated that oscillations of the degree of polarization involve both contribution of the purely rotational J-coherence and that of the rovibronic coherence in the resonant manifold when the rotational branches are coherently excited and the characteristic rotation-vibration interaction energy is larger than a typical free rotational energy under jet-cooled condition.

  13. 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.

  14. Controllable coherent perfect absorption in a composite film.

    PubMed

    Dutta-Gupta, Shourya; Martin, O J F; Gupta, S Dutta; Agarwal, G S

    2012-01-16

    We exploit the versatility provided by metal-dielectric composites to demonstrate controllable coherent perfect absorption (CPA) or anti-lasing in a slab of heterogeneous medium. The slab is illuminated by coherent light from both sides, at the same angle of incidence and the conditions required for CPA are investigated as a function of the different system parameters. Our calculations clearly elucidate the role of absorption as a necessary prerequisite for CPA. We further demonstrate the controllability of the CPA frequency to the extent of having the same at two distinct frequencies even in presence of dispersion, rendering the realization of anti-lasers more flexible. PMID:22274478

  15. 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

  16. Coherent control of birefringence and optical activity

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

    We show that polarization effects due to anisotropy and chirality affecting a wave propagating through a thin slab of material can be controlled by another electromagnetic wave. No nonlinearity of the metamaterial slab is required and the control can be exercised at arbitrarily low intensities. In proof-of-principle experiments with anisotropic and chiral microwave metamaterials, we show that manifestations of linear and circular birefringence and dichroism can be modulated by the control wave from their maximum value to zero.

  17. Coherent control of quantum dynamics in laser kicked molecular rotors

    NASA Astrophysics Data System (ADS)

    Bitter, Martin; Milner, Valery

    2016-05-01

    We investigate experimentally the dynamics of true quantum kicked rotors - oxygen and nitrogen molecules subject to a sequence of more than 20 ultrashort laser pulses with peak intensities exceeding 1013 W/ cm2 per pulse. Using state-resolved rotational Raman spectroscopy, we show that the centrifugal distortion is the main obstacle in reaching high rotational states, as it results in the coherent oscillations of rotational population similar to Bloch oscillations in condensed matter. We demonstrate that the timing of the individual pulses can be optimized to partially mitigate the centrifugal limit and produce broader rotational wave packets with higher degrees of rotational coherence. Progress towards the experimental observation of Anderson localization in laser-kicked molecular rotors will be discussed.

  18. Gas biology: tiny molecules controlling metabolic systems.

    PubMed

    Kajimura, Mayumi; Nakanishi, Tsuyoshi; Takenouchi, Toshiki; Morikawa, Takayuki; Hishiki, Takako; Yukutake, Yoshinori; Suematsu, Makoto

    2012-11-15

    It has been recognized that gaseous molecules and their signaling cascades play a vital role in alterations of metabolic systems in physiologic and pathologic conditions. Contrary to this awareness, detailed mechanisms whereby gases exert their actions, in particular in vivo, have been unclear because of several reasons. Gaseous signaling involves diverse reactions with metal centers of metalloproteins and thiol modification of cysteine residues of proteins. Both the multiplicity of gas targets and the technical limitations in accessing local gas concentrations make dissection of exact actions of any gas mediator a challenge. However, a series of advanced technologies now offer ways to explore gas-responsive regulatory processes in vivo. Imaging mass spectrometry combined with quantitative metabolomics by capillary-electrophoresis/mass spectrometry reveals spatio-temporal profiles of many metabolites. Comparing the metabolic footprinting of murine samples with a targeted deletion of a specific gas-producing enzyme makes it possible to determine sites of actions of the gas. In this review, we intend to elaborate on the ideas how small gaseous molecules interact with metabolic systems to control organ functions such as cerebral vascular tone and energy metabolism in vivo. PMID:22516267

  19. USING COHERENT WATER JETS TO CONTROL OIL SPILLS

    EPA Science Inventory

    The ability of coherent water streams to induce a surface current in water and thus control a floating oil slick was examined at the U.S. Environmental Protection Agency's (USEPA) Oil and Hazardous Materials Simulated Environmental Test Tank (OHMSETT). The objective of the tests ...

  20. Non-Markovian response of ultrafast coherent electronic ring currents in chiral aromatic molecules in a condensed phase

    NASA Astrophysics Data System (ADS)

    Mineo, H.; Lin, S. H.; Fujimura, Y.; Xu, J.; Xu, R. X.; Yan, Y. J.

    2013-12-01

    Results of a theoretical study on non-Markov response for femtosecond laser-driven coherent ring currents in chiral aromatic molecules embedded in a condensed phase are presented. Coherent ring currents are generated by coherent excitation of a pair of quasi-degenerated π-electronic excited states. The coherent electronic dynamical behaviors are strongly influenced by interactions between the electronic system and phonon bath in a condensed phase. Here, the bath correlation time is not instantaneous but should be taken to be a finite time in ultrashort time-resolved experiments. In such a case, Markov approximation breaks down. A hierarchical master equation approach for an improved semiclassical Drude dissipation model was adopted to examine the non-Markov effects on ultrafast coherent electronic ring currents of (P)-2,2'-biphenol in a condensed phase. Time evolution of the coherent ring current derived in the hierarchical master equation approach was calculated and compared with those in the Drude model in the Markov approximation and in the static limit. The results show how non-Markovian behaviors in quantum beat signals of ring currents depend on the Drude bath damping constant. Effects of temperatures on ultrafast coherent electronic ring currents are also clarified.

  1. Non-Markovian response of ultrafast coherent electronic ring currents in chiral aromatic molecules in a condensed phase

    SciTech Connect

    Mineo, H.; Lin, S. H.; Fujimura, Y.; Xu, J.; Xu, R. X.; Yan, Y. J.

    2013-12-07

    Results of a theoretical study on non-Markov response for femtosecond laser-driven coherent ring currents in chiral aromatic molecules embedded in a condensed phase are presented. Coherent ring currents are generated by coherent excitation of a pair of quasi-degenerated π-electronic excited states. The coherent electronic dynamical behaviors are strongly influenced by interactions between the electronic system and phonon bath in a condensed phase. Here, the bath correlation time is not instantaneous but should be taken to be a finite time in ultrashort time-resolved experiments. In such a case, Markov approximation breaks down. A hierarchical master equation approach for an improved semiclassical Drude dissipation model was adopted to examine the non-Markov effects on ultrafast coherent electronic ring currents of (P)-2,2{sup ′}-biphenol in a condensed phase. Time evolution of the coherent ring current derived in the hierarchical master equation approach was calculated and compared with those in the Drude model in the Markov approximation and in the static limit. The results show how non-Markovian behaviors in quantum beat signals of ring currents depend on the Drude bath damping constant. Effects of temperatures on ultrafast coherent electronic ring currents are also clarified.

  2. Non-Markovian response of ultrafast coherent electronic ring currents in chiral aromatic molecules in a condensed phase.

    PubMed

    Mineo, H; Lin, S H; Fujimura, Y; Xu, J; Xu, R X; Yan, Y J

    2013-12-01

    Results of a theoretical study on non-Markov response for femtosecond laser-driven coherent ring currents in chiral aromatic molecules embedded in a condensed phase are presented. Coherent ring currents are generated by coherent excitation of a pair of quasi-degenerated π-electronic excited states. The coherent electronic dynamical behaviors are strongly influenced by interactions between the electronic system and phonon bath in a condensed phase. Here, the bath correlation time is not instantaneous but should be taken to be a finite time in ultrashort time-resolved experiments. In such a case, Markov approximation breaks down. A hierarchical master equation approach for an improved semiclassical Drude dissipation model was adopted to examine the non-Markov effects on ultrafast coherent electronic ring currents of (P)-2,2'-biphenol in a condensed phase. Time evolution of the coherent ring current derived in the hierarchical master equation approach was calculated and compared with those in the Drude model in the Markov approximation and in the static limit. The results show how non-Markovian behaviors in quantum beat signals of ring currents depend on the Drude bath damping constant. Effects of temperatures on ultrafast coherent electronic ring currents are also clarified. PMID:24320379

  3. 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.

  4. 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

    2016-07-01

    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 (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. PMID:27383945

  5. Coherence times of precise depth controlled NV centers in diamond

    NASA Astrophysics Data System (ADS)

    Wang, Junfeng; Zhang, Wenlong; Zhang, Jian; You, Jie; Li, Yan; Guo, Guoping; Feng, Fupan; Song, Xuerui; Lou, Liren; Zhu, Wei; Wang, Guanzhong

    2016-03-01

    We investigated the depth dependence of coherence times of nitrogen-vacancy (NV) centers through precise depth control using oxidative etching at 580 °C in air. By successive nanoscale etching, NV centers could be brought close to the diamond surface step by step, which enabled us to track the evolution of the number of NV centers remaining in the chip and to study the depth dependence of coherence times of NV centers with diamond etching. Our results showed that the coherence times of NV centers declined rapidly with the depth reduction in the last about 22 nm before they finally disappeared, which revealed a critical depth for the influence of a rapid fluctuating surface spin bath. Moreover, by using the slow etching method combined with low-energy nitrogen implantation, NV centers with depths shallower than the initially implanted depths can be generated, which are preferred for detecting external spins with higher sensitivity.

  6. 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

  7. Coherent feedback control of a single qubit in diamond.

    PubMed

    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

  8. Multiphoton coherent control in complex systems

    PubMed Central

    Goswami, Debabrata

    2005-01-01

    Control of multiphoton transitions is demonstrated for a multilevel system by generalizing the instantaneous phase of any chirped pulse as individual terms of a Taylor series expansion. In the case of a simple two-level system, all odd terms in the series lead to population inversion while the even terms lead to self-induced transparency. The results hold for multiphoton transitions that do not have any lower-order photon resonance or any intermediate virtual state dynamics within the laser pulse width. PMID:17396157

  9. Tunneling induced dark states and the controllable resonance fluorescence spectrum in quantum dot molecules

    NASA Astrophysics Data System (ADS)

    Tian, Si-Cong; Wan, Ren-Gang; Tong, Cun-Zhu; Ning, Yong-Qiang; Qin, Li; Liu, Yun

    2014-08-01

    Optical spectroscopy, a powerful tool for probing and manipulating quantum dots (QDs), has been used to investigate the resonance fluorescence spectrum from linear triple quantum dot molecules controlled by tunneling, using atomic physics methods. Interesting features such as quenching and narrowing of the fluorescence are observed. In such molecules the tunneling between the quantum dots can also induce a dark state. The results are explained by the transition properties of the dressed states generated by the coupling of the laser and the tunneling. Unlike the atomic system, in such quantum dot molecules quantum coherence can be induced using tunneling, requiring no coupling lasers, which will allow tunneling controllable quantum dot molecules to be applied to quantum optics and photonics.

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

    PubMed

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

    2016-08-12

    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. PMID:27563998

  11. 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.

  12. 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.

  13. Quantum coherence and entanglement control for atom-cavity systems

    NASA Astrophysics Data System (ADS)

    Shu, Wenchong

    Coherence and entanglement play a significant role in the quantum theory. Ideal quantum systems, "closed" to the outside world, remain quantum forever and thus manage to retain coherence and entanglement. Real quantum systems, however, are open to the environment and are therefore susceptible to the phenomenon of decoherence and disentanglement which are major hindrances to the effectiveness of quantum information processing tasks. In this thesis we have theoretically studied the evolution of coherence and entanglement in quantum systems coupled to various environments. We have also studied ways and means of controlling the decay of coherence and entanglement. We have studied the exact qubit entanglement dynamics of some interesting initial states coupled to a high-Q cavity containing zero photon, one photon, two photons and many photons respectively. We have found that an initially correlated environmental state can serve as an enhancer for entanglement decay or generation processes. More precisely, we have demonstrated that the degree of entanglement, including its collapse as well as its revival times, can be significantly modified by the correlated structure of the environmental modes. We have also studied dynamical decoupling (DD) technique --- a prominent strategy of controlling decoherence and preserving entanglement in open quantum systems. We have analyzed several DD control methods applied to qubit systems that can eliminate the system-environment coupling and prolong the quantum coherence time. Particularly, we have proposed a new DD sequence consisting a set of designed control operators that can universally protected an unknown qutrit state against colored phase and amplitude environment noises. In addition, in a non-Markovian regime, we have reformulated the quantum state diffusion (QSD) equation to incorporate the effect of the external control fields. Without any assumptions on the system-environment coupling and the size of environment, we have

  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. 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.

  16. 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

    2016-01-01

    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

  17. 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

  18. Coherent Terahertz Control of Vertical Transport in Semiconductor Heterostructures

    NASA Astrophysics Data System (ADS)

    Vänskä, O.; Tittonen, I.; Koch, S. W.; Kira, M.

    2015-03-01

    Coherent-control protocols are introduced to selectively transport electrons, excitons, or pure two-particle correlations through semiconductor interfaces. The scheme is tested in a double-quantum-well structure where a sequence of terahertz pulses is applied to induce the vertical excitation transfer between the wells. Using a microscopic theory, it is shown that efficient and highly selective transfer can be realized even in the presence of the unavoidable scattering and dephasing processes.

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

    PubMed

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

    2016-09-01

    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

  20. Spectroscopy and quantum control of cryogenically buffered polyatomic molecules

    NASA Astrophysics Data System (ADS)

    Patterson, David

    2016-05-01

    Cold polyatomic molecules offer rich possibilities for precision measurement, quantum control, and tests of fundamental symmetries. While manipulating, cooling, and detecting atoms and certain diatomic molecules at the single quantum state level is now possible, analogous tools for controlling polyatomic molecules lag far behind. Buffer gas cooling has emerged as a versatile tool for cooling such molecules. We will present recent demonstrations of state-specific and enantiomer-specific preparation of chiral molecules, and novel sensitive and ultra-specific chemical analysis techniques enabled by the combination of modern microwave spectroscopy techniques and the broad applicability of cryogenically buffered molecular samples.

  1. Atomic-Scale Control of Electron Transport through Single Molecules

    NASA Astrophysics Data System (ADS)

    Wang, Y. F.; Kröger, J.; Berndt, R.; Vázquez, H.; Brandbyge, M.; Paulsson, M.

    2010-04-01

    Tin-phthalocyanine molecules adsorbed on Ag(111) were contacted with the tip of a cryogenic scanning tunneling microscope. Orders-of-magnitude variations of the single-molecule junction conductance were achieved by controllably dehydrogenating the molecule and by modifying the atomic structure of the surface electrode. Nonequilibrium Green’s function calculations reproduce the trend of the conductance and visualize the current flow through the junction, which is guided through molecule-electrode chemical bonds.

  2. Coherent terahertz polarization control through manipulation of electron trajectories.

    PubMed

    Wen, Haidan; Lindenberg, Aaron M

    2009-07-10

    The dynamics of ionized electrons in a plasma can be controlled by synthetic optical fields composed of the fundamental and the second harmonic of femtosecond optical pulses with an arbitrary phase and polarization. We show here that the plasma-emitted half-cycle THz radiation directly reflects the two-dimensional trajectories of the electrons through polarization sensitive THz emission spectroscopy. As a result, we find that the THz polarization smoothly rotates through 2pi radians as the relative phase between the two pulses is adjusted, providing a new means of coherently controlling the polarization of light at THz frequencies. PMID:19659205

  3. Coherent Terahertz Polarization Control through Manipulation of Electron Trajectories

    SciTech Connect

    Wen Haidan; Lindenberg, Aaron M.

    2009-07-10

    The dynamics of ionized electrons in a plasma can be controlled by synthetic optical fields composed of the fundamental and the second harmonic of femtosecond optical pulses with an arbitrary phase and polarization. We show here that the plasma-emitted half-cycle THz radiation directly reflects the two-dimensional trajectories of the electrons through polarization sensitive THz emission spectroscopy. As a result, we find that the THz polarization smoothly rotates through 2pi radians as the relative phase between the two pulses is adjusted, providing a new means of coherently controlling the polarization of light at THz frequencies.

  4. 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. PMID:16712153

  5. 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.

  6. Electric field controlled magnetic anisotropy in a single molecule.

    PubMed

    Zyazin, Alexander S; van den Berg, Johan W G; Osorio, Edgar A; van der Zant, Herre S J; Konstantinidis, Nikolaos P; Leijnse, Martin; Wegewijs, Maarten R; May, Falk; Hofstetter, Walter; Danieli, Chiara; Cornia, Andrea

    2010-09-01

    We have measured quantum transport through an individual Fe(4) single-molecule magnet embedded in a three-terminal device geometry. The characteristic zero-field splittings of adjacent charge states and their magnetic field evolution are observed in inelastic tunneling spectroscopy. We demonstrate that the molecule retains its magnetic properties and, moreover, that the magnetic anisotropy is significantly enhanced by reversible electron addition/subtraction controlled with the gate voltage. Single-molecule magnetism can thus be electrically controlled. PMID:20687519

  7. Electric Field Controlled Magnetic Anisotropy in a Single Molecule

    NASA Astrophysics Data System (ADS)

    Zyazin, Alexander S.; van den Berg, Johan W. G.; Osorio, Edgar A.; van der Zant, Herre S. J.; Konstantinidis, Nikolaos P.; Leijnse, Martin; Wegewijs, Maarten R.; May, Falk; Hofstetter, Walter; Danieli, Chiara; Cornia, Andrea

    2010-09-01

    We have measured quantum transport through an individual Fe$_4$ single-molecule magnet embedded in a three-terminal device geometry. The characteristic zero-field splittings of adjacent charge states and their magnetic field evolution are observed in inelastic tunneling spectroscopy. We demonstrate that the molecule retains its magnetic properties, and moreover, that the magnetic anisotropy is significantly enhanced by reversible electron addition / subtraction controlled with the gate voltage. Single-molecule magnetism can thus be electrically controlled.

  8. 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

  9. 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

  10. Focus on coherent control of complex quantum systems

    NASA Astrophysics Data System (ADS)

    Whaley, Birgitta; Milburn, Gerard

    2015-10-01

    The rapid growth of quantum information sciences over the past few decades has fueled a corresponding rise in high profile applications in fields such as metrology, sensors, spintronics, and attosecond dynamics, in addition to quantum information processing. Realizing this potential of today’s quantum science and the novel technologies based on this requires a high degree of coherent control of quantum systems. While early efforts in systematizing methods for high fidelity quantum control focused on isolated or closed quantum systems, recent advances in experimental design, measurement and monitoring, have stimulated both need and interest in the control of complex or large scale quantum systems that may also be coupled to an interactive environment or reservoir. This focus issue brings together new theoretical and experimental work addressing the formulation and implementation of quantum control for a broad range of applications in quantum science and technology today.

  11. 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.

  12. 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.

  13. 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.

  14. 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. PMID:23072742

  15. 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.

  16. Density functional theory based direct comparison of coherent tunneling and electron hopping in redox-active single-molecule junctions

    NASA Astrophysics Data System (ADS)

    Kastlunger, Georg; Stadler, Robert

    2015-03-01

    To define the conductance of single-molecule junctions with a redox functionality in an electrochemical cell, two conceptually different electron transport mechanisms, namely, coherent tunneling and vibrationally induced hopping, compete with each other, where implicit parameters of the setup such as the length of the molecule and the applied gate voltage decide which mechanism is the dominant one. Although coherent tunneling is most efficiently described within Landauer theory and the common theoretical treatment of electron hopping is based on Marcus theory, both theories are adequate for the processes they describe without introducing accuracy-limiting approximations. For a direct comparison, however, it has to be ensured that the crucial quantities obtained from electronic structure calculations, i.e., the transmission function T (E ) in Landauer theory and the transfer integral V , the reorganization energy λ , and the driving force Δ G0 in Marcus theory, are derived from similar grounds, as pointed out by Nitzan and coworkers in a series of publications. In this paper our framework is a single-particle picture, for which we perform density functional theory calculations for the conductance corresponding to both transport mechanisms for junctions with the central molecule containing one, two, or three Ruthenium centers, from which we extrapolate our results in order to define the critical length of the transition point of the two regimes which we identify at 5.76nm for this type of molecular wire. We also discuss trends in the dependence on an electrochemically induced gate potential.

  17. 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.

  18. Coherent control of multiple vibrational excitations for optimal detection

    NASA Astrophysics Data System (ADS)

    McGrane, S. D.; Scharff, R. J.; Greenfield, M.; Moore, D. S.

    2009-10-01

    While the means to selectively excite a single vibrational mode using ultrafast pulse shaping are well established, the subsequent problem of selectively exciting multiple vibrational modes simultaneously has been largely neglected. The coherent control of multiple vibrational excitations has applications in control of chemistry, chemical detection and molecular vibrational quantum information processing. Using simulations and experiments, we demonstrate that multiple vibrational modes can be selectively excited with the concurrent suppression of multiple interfering modes by orders of magnitude. While the mechanism of selectivity is analogous to that of single mode selectivity, the interferences required to select multiple modes require complicated non-intuitive pulse trains. Additionally, we show that selective detection can be achieved by the optimal pulse shape, even when the nature of the interfering species is varied, suggesting that optimized detection should be practical in real world applications. Experimental measurements of the multiplex coherent anti-Stokes Raman spectra (CARS) and CARS decay times of toluene, acetone, cis-stilbene and nitromethane liquids are reported, along with optimizations attempting to selectively excite nitromethane in a mixture of the four solvents. The experimental implementation exhibits a smaller degree of signal to background enhancement than predicted, which is primarily attributed to the single objective optimization methodology and not to fundamental limitations.

  19. Controlled Ensembles of Formaldehyde Molecules at Ultracold Temperatures

    NASA Astrophysics Data System (ADS)

    Zeppenfeld, Martin; Prehn, Alexander; Ibrügger, Martin; Glöckner, Rosa; Rempe, Gerhard

    2016-05-01

    Applications of ultracold molecules such as quantum information processing and quantum controlled chemistry require the preparation of ultracold molecule ensembles with a high level of control over all molecular degrees of freedom. Due to the inability to apply standard atom cooling techniques such as laser cooling to most molecule species, developing new methods is essential. We present a toolbox of techniques developed in our group for controlling molecules. A microstructured electric trap allows us to trap molecules in predominantly homogeneous electric fields with trapping times of up to a minute. Optical pumping on a vibrational transition allows us to transfer the population from a large number of rotational states to a single rotational M-sublevel. Our experiment provides excellent conditions for precision spectroscopy and investigation of ultracold collisions.

  20. Control of vascular permeability by adhesion molecules.

    PubMed

    Sarelius, Ingrid H; Glading, Angela J

    2015-01-01

    Vascular permeability is a vital function of the circulatory system that is regulated in large part by the limited flux of solutes, water, and cells through the endothelial cell layer. One major pathway through this barrier is via the inter-endothelial junction, which is driven by the regulation of cadherin-based adhesions. The endothelium also forms attachments with surrounding proteins and cells via 2 classes of adhesion molecules, the integrins and IgCAMs. Integrins and IgCAMs propagate activation of multiple downstream signals that potentially impact cadherin adhesion. Here we discuss the known contributions of integrin and IgCAM signaling to the regulation of cadherin adhesion stability, endothelial barrier function, and vascular permeability. Emphasis is placed on known and prospective crosstalk signaling mechanisms between integrins, the IgCAMs- ICAM-1 and PECAM-1, and inter-endothelial cadherin adhesions, as potential strategic signaling nodes for multipartite regulation of cadherin adhesion. PMID:25838987

  1. Coherent control of optical information with matter wave dynamics.

    PubMed

    Ginsberg, Naomi S; Garner, Sean R; Hau, Lene Vestergaard

    2007-02-01

    In recent years, significant progress has been achieved in manipulating matter with light, and light with matter. Resonant laser fields interacting with cold, dense atom clouds provide a particularly rich system. Such light fields interact strongly with the internal electrons of the atoms, and couple directly to external atomic motion through recoil momenta imparted when photons are absorbed and emitted. Ultraslow light propagation in Bose-Einstein condensates represents an extreme example of resonant light manipulation using cold atoms. Here we demonstrate that a slow light pulse can be stopped and stored in one Bose-Einstein condensate and subsequently revived from a totally different condensate, 160 mum away; information is transferred through conversion of the optical pulse into a travelling matter wave. In the presence of an optical coupling field, a probe laser pulse is first injected into one of the condensates where it is spatially compressed to a length much shorter than the coherent extent of the condensate. The coupling field is then turned off, leaving the atoms in the first condensate in quantum superposition states that comprise a stationary component and a recoiling component in a different internal state. The amplitude and phase of the spatially localized light pulse are imprinted on the recoiling part of the wavefunction, which moves towards the second condensate. When this 'messenger' atom pulse is embedded in the second condensate, the system is re-illuminated with the coupling laser. The probe light is driven back on and the messenger pulse is coherently added to the matter field of the second condensate by way of slow-light-mediated atomic matter-wave amplification. The revived light pulse records the relative amplitude and phase between the recoiling atomic imprint and the revival condensate. Our results provide a dramatic demonstration of coherent optical information processing with matter wave dynamics. Such quantum control may find

  2. 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.

  3. Ultrafast coherent optical control of a single diamond spin

    NASA Astrophysics Data System (ADS)

    Bassett, L. C.; Heremans, F. J.; Awschalom, D. D.; Burkard, G.

    2013-03-01

    As an optically addressable solid-state electronic spin, the nitrogen-vacancy (NV) center in diamond has great promise for applications in quantum information science and metrology. At temperatures below ~ 10 K, the NV center's optical fine structure facilitates coherent coupling between the electronic spin and light, providing the means for all-optical spin control and other applications in quantum optics. Here, using ultrafast optical pump-probe techniques, we investigate the interplay of orbital, vibrational, and spin dynamics on timescales ranging from femtoseconds to nanoseconds. These techniques provide a flexible and powerful probe of orbital dynamics in the NV center's optically excited state, and enable optical spin control with sub-picosecond resolution. Work supported by AFOSR, ARO, and DARPA.

  4. 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

  5. Controlling single-molecule junction conductance by molecular interactions.

    PubMed

    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

  6. 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.

  7. Microscopy beyond the diffraction limit using actively controlled single molecules

    PubMed Central

    MOERNER, W.E.

    2013-01-01

    Summary In this short review, the general principles are described for obtaining microscopic images with resolution beyond the optical diffraction limit with single molecules. Although it has been known for several decades that single-molecule emitters can blink or turn on and off, in recent work the addition of on/off control of molecular emission to maintain concentrations at very low levels in each imaging frame combined with sequential imaging of sparse subsets has enabled the reconstruction of images with resolution far below the optical diffraction limit. Single-molecule active control microscopy provides a powerful window into information about nanoscale structures that was previously unavailable. PMID:22582796

  8. Coherent control of the Goos-Haenchen shift

    SciTech Connect

    Ziauddin; Qamar, Sajid; Zubairy, M. Suhail

    2010-02-15

    The behavior of the Goos-Haenchen (GH) shifts in the reflected and transmitted light beam which is incident on a cavity containing an intracavity medium of three-level or four-level atoms with electromagnetically induced transparency (EIT) is discussed. We report a coherent control of the GH shift in a fixed configuration or device via superluminal and subluminal wave propagation. For superluminal wave propagation, we observe negative GH shifts in the reflected part of the incident light whereas the shifts are positive in the transmitted light beam. This corresponds to the negative group index of the cavity in the former case and positive group index of the cavity in the latter. For subluminal wave propagation, the behavior of the GH shifts in the reflected light changes and positive shifts appear; however, the GH shifts in the transmitted light remains positive. The corresponding group index of the cavity is positive in both cases.

  9. Label-Free Fluctuation Spectroscopy Based on Coherent Anti-Stokes Raman Scattering from Bulk Water Molecules.

    PubMed

    Rabasovic, M D; Sisamakis, E; Wennmalm, S; Widengren, J

    2016-04-01

    Nanoparticles (NPs) and molecules can be analyzed by inverse fluorescence correlation spectroscopy (iFCS) as they pass through an open detection volume, displacing fractions of the fluorescence-emitting solution in which they are dissolved. iFCS does not require the NPs or molecules to be labeled. However, fluorophores in μm-mm concentrations are needed for the solution signal. Here, we instead use coherent anti-Stokes Raman scattering (CARS) from plain water molecules as the signal from the solution. By this fully label-free approach, termed inverse CARS-based correlation spectroscopy (iCARS-CS), NPs that are a few tenths of nm in diameter and at pM concentrations can be analyzed, and their absolute volumes/concentrations can be determined. Likewise, lipid vesicles can be analyzed as they diffuse/flow through the detection volume by using CARS fluctuations from the surrounding water molecules. iCARS-CS could likely offer a broadly applicable, label-free characterization technique of, for example, NPs, small lipid exosomes, or microparticles in biomolecular diagnostics and screening, and can also utilize CARS signals from biologically relevant media other than water. PMID:26819085

  10. Coherence-Modulated Third Harmonic Generation for Second Hyper-Raman Spectroscopy of Molecules at an Interface

    NASA Astrophysics Data System (ADS)

    Dillman, Kevin; Wilson, Jesse; Bartels, Randy; Levinger, Nancy

    2012-02-01

    We have developed a method of probing the low-frequency (sub-1000 cm-1) vibrational modes of molecules at interfaces using third-harmonic generation (THG). The THG process is enhanced at an interface due to the differences in the third-order nonlinear susceptibilities of the materials. We have used this method to collect low-frequency second hyper-Raman spectra from BGO, BaF2 and CdWO4 crystals. In addition, we have observed coherent second hyper-Raman scattering arising from CCl4 molecules at the liquid-glass interface. We are presently extending these techniques to observe resonant second hyper-Raman scattering from dye molecules adsorbed on gold nanoparticles in order to gain surface enhancement effects. We aim to use this method to characterize the environment at interfaces of reverse micelle systems. The development of this method is significant because we can sensitively probe the low-frequency vibrational modes of only those molecules at an interface.

  11. Toward Quantum Processing in Molecules: A THz-Bandwidth Coherent Memory for Light

    NASA Astrophysics Data System (ADS)

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

    2013-08-01

    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 ˜1ns, enabling ˜104 operational time bins. The results demonstrate the promise of molecules for constructing compact ultrafast quantum photonic technologies.

  12. Coherent Control of Molecular Torsion and the Active-space Decomposition Method

    NASA Astrophysics Data System (ADS)

    Parker, Shane Matthew

    This dissertation discusses schemes and applications for the strong-field control of molecular torsions as well as introduces the active-space decomposition method. In the first part, a route to realize general control over the torsional motions of a class of biaryl compounds is proposed. Torsion in biaryl compounds--molecules with two aromatic moieties connected by a bond about which the barrier to rotation is small--mediates the electronic coupling between the two rings in the molecule. Thus, by controlling the torsion angle, one also controls the electron transfer and transport rates, the absorption and emission spectra, and the molecule's chirality. In our scheme, a non-resonant half-cycle pulse interacts with the permanent dipole of only one moiety of the pre-oriented biaryl compound. In the non-adiabatic regime, coherent motion is initiated by the half-cycle pulse. In the adiabatic regime, the torsion angle is tuned by the pulse. By properly choosing the parameters and polarization of the half-cycle pulse, we show that free internal rotation can be started or that the molecular chirality can be inverted. Then, with the aid of optimal control theory, we design "deracemizing" control pulses, i.e., control pulses that convert a racemic mixture into an enantiopure mixture. Finally, we explore the potential for this type of control in a single-molecule pulling experiment. In the second part, we describe the active space decomposition method for computing excited states of molecular dimers. In this method, the dimer's wavefunction is expressed as a linear combination of direct products of orthogonal localized monomer states. The adiabatic dimer states are found by diagonalizing the Hamiltonian in this direct product space. Matrix elements between direct product states are computed directly, without ever explicitly forming the dimer wavefunction, thus enabling calculations of dimers with active space sizes that would be otherwise impossible. The decomposed

  13. Theory of femtosecond coherent double-pump single-molecule spectroscopy: Application to light harvesting complexes

    SciTech Connect

    Chen, Lipeng; Zhao, Yang; Gelin, Maxim F.; Domcke, Wolfgang

    2015-04-28

    We develop a first principles theoretical description of femtosecond double-pump single-molecule signals of molecular aggregates. We incorporate all singly excited electronic states and vibrational modes with significant exciton-phonon coupling into a system Hamiltonian and treat the ensuing system dynamics within the Davydov D{sub 1} Ansatz. The remaining intra- and inter-molecular vibrational modes are treated as a heat bath and their effect is accounted for through lineshape functions. We apply our theory to simulate single-molecule signals of the light harvesting complex II. The calculated signals exhibit pronounced oscillations of mixed electron-vibrational (vibronic) origin. Their periods decrease with decreasing exciton-phonon coupling.

  14. 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.

  15. Flexible coherent control of plasmonic spin-Hall effect.

    PubMed

    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

  16. 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

  17. Controlled release of fragrant molecules with visible light.

    PubMed

    Wang, Zhuozhi; Johns, Valentine K; Liao, Yi

    2014-11-01

    Controlled release of odorous molecules is the key to digital scent technology which will add another dimension to electronics. Photorelease is a cold mechanism that promises better temporal and spatial control than thermal release. Herein we report a novel material composed of an acid-sensitive polymer carrying a fragrant aldehyde and a reversible metastable-state photoacid. It releases the fragrant molecule under visible light, and stops releasing it after the light is turned off. A metastable-state photoacid with a fast reverse-reaction rate was developed to quickly stop the release after irradiation. Both the carrier polymer and the photoacid can be reused after all the fragrant molecules have been released. The material combines the advantages of visible-light activity, fast on/off rate, easy preparation, and recyclability, and thus is promising for digital scent technology. PMID:25284277

  18. 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.

  19. 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.

  20. 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

  1. Statistical properties in Young's interference pattern formed with a radially polarized beam with controllable spatial coherence.

    PubMed

    Zhu, Shijun; Wang, Fei; Chen, Yahong; Li, Zhenhua; Cai, Yangjian

    2014-11-17

    Experimental generation of a radially polarized (RP) beam with controllable spatial coherence (i.e., partially coherent RP beam) was reported recently [Appl. Phys. Lett. 100, 051108 (2012)]. In this paper, we carry out theoretical and experimental studies of the statistical properties in Young's two-slit interference pattern formed with a partially coherent RP beam. An approximate analytical expression for the cross-spectral density matrix of a partially coherent RP beam in the observation plane is obtained, and it is found that the statistical properties, such as the intensity, the degree of coherence and the degree of polarization, are strongly affected by the spatial coherence of the incident beam. Our experimental results are consistent with the theoretical predictions, and may be useful in some applications, where light field with special statistical properties are required. PMID:25402110

  2. Attosecond-Recollision-Controlled Selective Fragmentation of Polyatomic Molecules

    NASA Astrophysics Data System (ADS)

    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

    2012-12-01

    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. 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. PMID:23368312

  4. Vacuum-Assisted Generation and Control of Atomic Coherences at X-Ray Energies

    NASA Astrophysics Data System (ADS)

    Heeg, Kilian P.; Wille, Hans-Christian; Schlage, Kai; Guryeva, Tatyana; Schumacher, Daniel; Uschmann, Ingo; Schulze, Kai S.; Marx, Berit; Kämpfer, Tino; Paulus, Gerhard G.; Röhlsberger, Ralf; Evers, Jörg

    2013-08-01

    The control of light-matter interaction at the quantum level usually requires coherent laser fields. But already an exchange of virtual photons with the electromagnetic vacuum field alone can lead to quantum coherences, which subsequently suppress spontaneous emission. We demonstrate such spontaneously generated coherences (SGC) in a large ensemble of nuclei operating in the x-ray regime, resonantly coupled to a common cavity environment. The observed SGC originates from two fundamentally different mechanisms related to cooperative emission and magnetically controlled anisotropy of the cavity vacuum. This approach opens new perspectives for quantum control, quantum state engineering and simulation of quantum many-body physics in an essentially decoherence-free setting.

  5. Effects of bonding type and interface geometry on coherent transport through the single-molecule magnet Mn12

    NASA Astrophysics Data System (ADS)

    Park, Kyungwha; Barraza-Lopez, Salvador; García-Suárez, Víctor M.; Ferrer, Jaime

    2010-03-01

    We examine theoretically coherent electron transport through the single-molecule magnet Mn12 , bridged between Au(111) electrodes, using the nonequilibrium Green’s function method and the density-functional theory. We analyze the effects of bonding type, molecular orientation, and geometry relaxation on the electronic properties and charge and spin transport across the single-molecule junction. We consider nine interface geometries leading to five bonding mechanisms and two molecular orientations: (i) Au-C bonding, (ii) Au-Au bonding, (iii) Au-S bonding, (iv) Au-H bonding, and (v) physisorption via van der Waals forces. The two molecular orientations of Mn12 correspond to the magnetic easy axis of the molecule aligned perpendicular [hereafter denoted as orientation (1)] or parallel [orientation (2)] to the direction of electron transport. We find that the electron transport is carried by the lowest unoccupied molecular orbital (LUMO) level in all the cases that we have simulated. Relaxation of the junction geometries mainly shifts the relevant occupied molecular levels toward the Fermi energy as well as slightly reduces the broadening of the LUMO level. As a result, the current slightly decreases at low bias voltage. Our calculations also show that placing the molecule in the orientation (1) broadens the LUMO level much more than in the orientation (2) due to the internal structure of the Mn12 . Consequently, junctions with the former orientation yield a higher current than those with the latter. Among all of the bonding types considered, the Au-C bonding gives rise to the highest current (about one order of magnitude higher than the Au-S bonding), for a given distance between the electrodes. The current through the junction with other bonding types decreases in the order of Au-Au, Au-S, and Au-H. Importantly, the spin-filtering effect in all the nine geometries stays robust and their ratios of the majority-spin to the minority-spin transmission coefficients are

  6. Control of coherent structure in coaxial swirling turbulent jets

    NASA Astrophysics Data System (ADS)

    Lee, Wonjoong

    excitation in the present work. Consequently, the knowledge gained from this research could benefit the fluid dynamic community by increasing the fundamental understanding of turbulent swirling flows and their effective control for the formation and breakdown of coherent structure.

  7. Coherent cancellation of geometric phase for the OH molecule in external fields

    NASA Astrophysics Data System (ADS)

    Bhattacharya, M.; Marin, S.; Kleinert, M.

    2014-05-01

    The OH molecule in its ground state presents a versatile platform for precision measurement and quantum information processing. These applications vitally depend on the accurate measurement of transition energies between the OH levels. Significant sources of systematic errors in these measurements are shifts based on the geometric phase arising from the magnetic and electric fields used for manipulating OH. In this article, we present these geometric phases for fields that vary harmonically in time, as in the Ramsey technique. Our calculation of the phases is exact within the description provided by our recent analytic solution of an effective Stark-Zeeman Hamiltonian for the OH ground state. This Hamiltonian has been shown to model experimental data accurately. We find that the OH geometric phases exhibit rich structure as a function of the field rotation rate. Remarkably, we find rotation rates where the geometric phase accumulated by a specific state is zero, or where the relative geometric phase between two states vanishes. We expect these findings to be of importance to precision experiments on OH involving time-varying fields. More specifically, our analysis quantitatively characterizes an important item in the error budget for precision spectroscopy of ground-state OH.

  8. 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.

  9. Coherent phase control of internal conversion in pyrazine.

    PubMed

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

    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 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. PMID:25877582

  10. 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.

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

    PubMed

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

    2016-03-01

    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

  12. 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

  13. Theoretical analysis of controllability of interference phenomena between partially coherent fields in the intensity matrix theory

    NASA Astrophysics Data System (ADS)

    Yashiki, Satoshi

    2016-09-01

    We analyze the controllability of interference phenomena between partially coherent fields by introducing the Wigner distribution function (WDF) and entropy, which is defined using the intensity matrix [H. Gamo, J. Opt. Soc. Am. 47, 976 (1957)]. The analytical derivation of the WDF and entropy is presented for a partially coherent imaging system consisting of two pinholes illuminated by a circular source. It is shown that the WDF, defined in the 4D space–spatial frequency region, and entropy can be useful tools to understand how one can freely and quantitatively control the interference when any optical components in the partially coherent imaging system are changed.

  14. Comprehension through explanation as the interaction of the brain's coherence and cognitive control networks.

    PubMed

    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

  15. 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

  16. 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.

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

    PubMed

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

    2016-01-01

    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. © 2016 American Physiological Society. Compr Physiol 6:945-973, 2016. PMID:27065171

  18. The manipulation of massive ro-vibronic superpositions using time frequency-resolved coherent anti-Stokes Raman scattering (TFRCARS): from quantum control to quantum computing

    NASA Astrophysics Data System (ADS)

    Zadoyan, R.; Kohen, D.; Lidar, D. A.; Apkarian, V. A.

    2001-05-01

    Molecular ro-vibronic coherences, joint energy-time distributions of quantum amplitudes, are selectively prepared, manipulated, and imaged in time-frequency-resolved coherent anti-Stokes Raman scattering (TFRCARS) measurements using femtosecond laser pulses. The studies are implemented in iodine vapor, with its thermally occupied statistical ro-vibrational density serving as initial state. The evolution of the massive ro-vibronic superpositions, consisting of 10 3 eigenstates, is followed through two-dimensional images. The first- and second-order coherences are captured using time-integrated frequency-resolved CARS, while the third-order coherence is captured using time-gated frequency-resolved CARS. The Fourier filtering provided by time-integrated detection projects out single ro-vibronic transitions, while time-gated detection allows the projection of arbitrary ro-vibronic superpositions from the coherent third-order polarization. A detailed analysis of the data is provided to highlight the salient features of this four-wave mixing process. The richly patterned images of the ro-vibrational coherences can be understood in terms of phase evolution in rotation-vibration-electronic Hilbert space, using time-circuit diagrams. Beside the control and imaging of chemistry, the controlled manipulation of massive quantum coherences suggests the possibility of quantum computing. We argue that the universal logic gates necessary for arbitrary quantum computing - all single qubit operations and the two-qubit controlled-NOT (CNOT) gate - are available in time-resolved four-wave mixing in a molecule. The molecular rotational manifold is naturally "wired" for carrying out all single qubit operations efficiently, and in parallel. We identify vibronic coherences as one example of a naturally available two-qubit CNOT gate, wherein the vibrational qubit controls the switching of the targeted electronic qubit.

  19. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2011-08-01

    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.

  1. Quantum coherent π-electron rotations in a non-planar chiral molecule induced by using a linearly polarized UV laser pulse

    NASA Astrophysics Data System (ADS)

    Mineo, Hirobumi; Fujimura, Yuichi

    2015-06-01

    We propose an ultrafast quantum switching method of π-electron rotations, which are switched among four rotational patterns in a nonplanar chiral aromatic molecule (P)-2,2’- biphenol and perform the sequential switching among four rotational patterns which are performed by the overlapped pump-dump laser pulses. Coherent π-electron dynamics are generated by applying the linearly polarized UV pulse laser to create a pair of coherent quasidegenerated excited states. We also plot the time-dependent π-electron ring current, and discussed ring current transfer between two aromatic rings.

  2. Electric field control of donor pair diatomic molecules in silicon

    NASA Astrophysics Data System (ADS)

    Baena, Alejandra; Saraiva, Andre; Calderón, María J.; Koiller, Belita

    2015-03-01

    Single donors are well-established building blocks for engineering electronic properties of semiconductors, acting effectively as giant hydrogen atoms. Donor pairs, analogous to effective hydrogen molecules, were recently investigated in the strongly interacting regime in silicon. In this regime, electric field control renders timid results. Pairs that are more distant are more susceptible to external fields, and may harbour single electron charge control. Theoretically, the molecular quantum mechanics analogy between a donor pair and the H2 molecule in vacuum is not as straightforward as it may seem. A detailed understanding of the electronic structure of these molecular systems is a current challenge. We analyze the lowest energy states within effective mass theory, including central cell corrected donor potential effects and the conduction band multiplicity in Si. The spectrum of ionized donor pairs and its response to an external electric field will be presented. We contemplate possible advantages of heteropolar diatomic molecules, e.g, Sb -As pairs, as more efficient elements for such devices and applications.

  3. Optimal coherent control of coherent anti-Stokes Raman scattering: Signal enhancement and background elimination

    NASA Astrophysics Data System (ADS)

    Gao, Fang; Shuang, Feng; Shi, Junhui; Rabitz, Herschel; Wang, Haifeng; Cheng, Ji-Xin

    2012-04-01

    The ability to enhance resonant signals and eliminate the non-resonant background is analyzed for coherent anti-Stokes Raman scattering (CARS). The analysis is done at a specific frequency as well as for broadband excitation using femtosecond pulse-shaping techniques. An appropriate objective functional is employed to balance resonant signal enhancement against non-resonant background suppression. Optimal enhancement of the signal and minimization of the background can be achieved by shaping the probe pulse alone while keeping the pump and Stokes pulses unshaped. In some cases analytical forms for the probe pulse can be found, and numerical simulations are carried out for other circumstances. It is found that a good approximate optimal solution for resonant signal enhancement in two-pulse CARS is a superposition of linear and arctangent-type phases for the pump. The well-known probe delay method is shown to be a quasi-optimal scheme for broadband background suppression. The results should provide a basis to improve the performance of CARS spectroscopy and microscopy.

  4. Coherent control with a short-wavelength free-electron laser

    NASA Astrophysics Data System (ADS)

    Prince, K. C.; Allaria, E.; Callegari, C.; Cucini, R.; de Ninno, G.; di Mitri, S.; Diviacco, B.; Ferrari, E.; Finetti, P.; Gauthier, D.; Giannessi, L.; Mahne, N.; Penco, G.; Plekan, O.; Raimondi, L.; Rebernik, P.; Roussel, E.; Svetina, C.; Trovò, M.; Zangrando, M.; Negro, M.; Carpeggiani, P.; Reduzzi, M.; Sansone, G.; Grum-Grzhimailo, A. N.; Gryzlova, E. V.; Strakhova, S. I.; Bartschat, K.; Douguet, N.; Venzke, J.; Iablonskyi, D.; Kumagai, Y.; Takanashi, T.; Ueda, K.; Fischer, A.; Coreno, M.; Stienkemeier, F.; Ovcharenko, Y.; Mazza, T.; Meyer, M.

    2016-03-01

    Extreme ultraviolet and X-ray free-electron lasers (FELs) produce short-wavelength pulses with high intensity, ultrashort duration, well-defined polarization and transverse coherence, and have been utilized for many experiments previously possible only at long wavelengths: multiphoton ionization, pumping an atomic laser and four-wave mixing spectroscopy. However one important optical technique, coherent control, has not yet been demonstrated, because self-amplified spontaneous emission FELs have limited longitudinal coherence. Single-colour pulses from the FERMI seeded FEL are longitudinally coherent, and two-colour emission is predicted to be coherent. Here, we demonstrate the phase correlation of two colours, and manipulate it to control an experiment. Light of wavelengths 63.0 and 31.5 nm ionized neon, and we controlled the asymmetry of the photoelectron angular distribution by adjusting the phase, with a temporal resolution of 3 as. This opens the door to new short-wavelength coherent control experiments with ultrahigh time resolution and chemical sensitivity.

  5. 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

  6. 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

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

    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.

  8. Herbert P. Broida Prize Talk: Experimental realization of coherent control of molecular dynamics and chemical reactions with feedback-optimized laser pulses--Quantum Control of Femtochemistry

    NASA Astrophysics Data System (ADS)

    Gerber, Gustav

    2009-05-01

    By using coherent control techniques we control the behavior of quantum systems on their natural fs-time scale by applying ultrashort coherent light fields in the wavelength range from the IR to the UV. These laser pulses can be variably shaped in space and time using a laser pulse shaper consisting of a liquid-crystal display. [1] Laser-optimized femtochemistry in the gas phase and liquid phase is one field in which this new technique is successfully employed. Automated optimization of branching ratios and total product yields of gas phase photodissociation reactions as well as chemically selective molecular excitation in the liquid phase is performed [2][3]. Structural changes of a molecule in the liquid phase have been controlled by laser-optimized photoisomerization of a cyanine dye molecule [4] and of retinal in bacteriorhodopsin [5]. So far, optimal control techniques have been restricted to gas phase and condensed phase optimization experiments. Recently we have demonstrated femtosecond laser-assisted catalytic reactions on a Pd(100) single crystal surface. By applying a closed-loop optimal control scheme, we manipulate these reactions and selectively optimize the ratio of different bond-forming reaction channels, in contrast to previous quantum control experiments aiming at bond-cleavage. The results represent a first step towards selective photocatalysis of molecules. [4pt] [1] T. Baumert et al, Appl. Phys. B 65, 779 (1997)[0pt] [2] A. Assion et al, Science 282, 919(1998); T. Brixner et al, J. Mod. Opt. 50, 539 (2003)[0pt] [3] T. Brixner et al, Nature, Vol. 414, 57 (2001) and J. Chem. Phys. 118, 3692 (2003)[0pt] [4] G. Krampert et al, Phys. Rev. Lett. 94, 068305 (2005)[0pt] [5] G. Vogt et al, Chem. Phys. Lett. 433, 211 (2006) P. Nuernberger et al, Phys. Chem. Chem. Phys. 9, 2470 (2007)

  9. Coherent Control of the Effective Susceptibility through Wave Mixing in a Duplicated Two-Level System

    NASA Astrophysics Data System (ADS)

    Hashmi, F. A.; Bouchene, M. A.

    2008-11-01

    We theoretically demonstrate the coherent control of the effective susceptibility of a duplicated two-level system. The control is obtained for a linearly polarized weak field in the presence of a much stronger orthogonally polarized field. For small optical depths, the effective susceptibility χeff behaves as χline2iϕ (χlin is the linear susceptibility, ϕ the phase shift) allowing coherent control of the optical response. For large optical depths, χeff≈χlin*, turning an absorber into an amplifier without affecting the dispersion.

  10. 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…

  11. Coherence-controlled holographic microscopy for live-cell quantitative phase imaging in turbid media

    NASA Astrophysics Data System (ADS)

    Lostak, M.; Collakova, J.; Slaby, T.; Krizova, A.; Vesely, P.; Chmelik, R.

    2016-03-01

    In this work we present the coherence controlled holographic microscopy (CCHM)1 and its ability to image the living cells in turbid media2. The CCHM method and its advantages are introduced. A 'coherence gate effect'3, that enables imaging in turbid media, occurs owing to the low coherence illumination in our setup. The coherence gate effect is briefly theoretically explained and comparison of images with different illumination sources is shown. After that, the possibility of imaging in turbid media is applied to investigation of cell reactions to cytopathic turbid emulsions. In our experiments we used human cancer cells treated by biologically active phospholipids (BAPs). Cellular events leading to cell death, that would otherwise remain hidden in turbid media, are clearly observable and according to them cell fate can be deduced.

  12. 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.

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

    PubMed

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

    2016-04-22

    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. PMID:27152807

  14. Temperature-dependent remote control of polarization and coherence intensity with sender's pure initial state

    NASA Astrophysics Data System (ADS)

    Fel'dman, E. B.; Kuznetsova, E. I.; Zenchuk, A. I.

    2016-06-01

    We study the remote creation of the polarization and intensity of the first-order coherence (or coherence intensity) in long spin-1/2 chains with one-qubit sender and receiver. Therewith we use a physically motivated initial condition with the pure state of the sender and the thermodynamical equilibrium state of the other nodes. The main part of the creatable region is a one-to-one map of the initial state (control) parameters, except the small subregion twice covered by the control parameters, which appears owing to the chosen initial state. The polarization and coherence intensity behave differently in the state creation process. In particular, the coherence intensity cannot reach any significant value unless the polarization is large in long chains (unlike the short ones), but the opposite is not true. The coherence intensity vanishes with an increase in the chain length, while the polarization (by absolute value) is not sensitive to this parameter. We represent several characteristics of the creatable polarization and coherence intensity and describe their relation to the parameters of the initial state. The link to the eigenvalue-eigenvector parametrization of the receiver's state space is given.

  15. Temperature-dependent remote control of polarization and coherence intensity with sender's pure initial state

    NASA Astrophysics Data System (ADS)

    Fel'dman, E. B.; Kuznetsova, E. I.; Zenchuk, A. I.

    2016-03-01

    We study the remote creation of the polarization and intensity of the first-order coherence (or coherence intensity) in long spin-1/2 chains with one-qubit sender and receiver. Therewith we use a physically motivated initial condition with the pure state of the sender and the thermodynamical equilibrium state of the other nodes. The main part of the creatable region is a one-to-one map of the initial state (control) parameters, except the small subregion twice covered by the control parameters, which appears owing to the chosen initial state. The polarization and coherence intensity behave differently in the state creation process. In particular, the coherence intensity cannot reach any significant value unless the polarization is large in long chains (unlike the short ones), but the opposite is not true. The coherence intensity vanishes with an increase in the chain length, while the polarization (by absolute value) is not sensitive to this parameter. We represent several characteristics of the creatable polarization and coherence intensity and describe their relation to the parameters of the initial state. The link to the eigenvalue-eigenvector parametrization of the receiver's state space is given.

  16. 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.

  17. 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.

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

    PubMed

    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 PHx (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. PMID:26894452

  19. Strong field coherent control of molecular torsions—Analytical models

    SciTech Connect

    Ashwell, Benjamin A.; Ramakrishna, S.; Seideman, Tamar

    2015-08-14

    We introduce analytical models of torsional alignment by moderately intense laser pulses that are applicable to the limiting cases of the torsional barrier heights. Using these models, we explore in detail the role that the laser intensity and pulse duration play in coherent torsional dynamics, addressing both experimental and theoretical concerns. Our results suggest strategies for minimizing the risk of off-resonant ionization, noting the qualitative differences between the case of torsional alignment subject to a field-free torsional barrier and that of torsional alignment of a barrier-less system (equivalent to a 2D rigid rotor). We also investigate several interesting torsional phenomena, including the onset of impulsive alignment of torsions, field-driven oscillations in quantum number space, and the disappearance of an alignment upper bound observed for a rigid rotor in the impulsive torsional alignment limit.

  20. Strong field coherent control of molecular torsions--Analytical models.

    PubMed

    Ashwell, Benjamin A; Ramakrishna, S; Seideman, Tamar

    2015-08-14

    We introduce analytical models of torsional alignment by moderately intense laser pulses that are applicable to the limiting cases of the torsional barrier heights. Using these models, we explore in detail the role that the laser intensity and pulse duration play in coherent torsional dynamics, addressing both experimental and theoretical concerns. Our results suggest strategies for minimizing the risk of off-resonant ionization, noting the qualitative differences between the case of torsional alignment subject to a field-free torsional barrier and that of torsional alignment of a barrier-less system (equivalent to a 2D rigid rotor). We also investigate several interesting torsional phenomena, including the onset of impulsive alignment of torsions, field-driven oscillations in quantum number space, and the disappearance of an alignment upper bound observed for a rigid rotor in the impulsive torsional alignment limit. PMID:26277138

  1. Contribution of the Gouy phase to two-pathway coherent control of the photoionization and photodissociation of vinyl chloride

    SciTech Connect

    Barge, Vishal J.; Gordon, Robert J.; Hu Zhan

    2008-12-28

    The electric field of a light wave accumulates a {pi} phase shift as it passes through a focus. We show here how this effect, known as the Gouy phase, may be used to control the branching ratio of a unimolecular reaction when the products are formed with different numbers of photons. We demonstrate this control method for the ionization and dissociation of vinyl chloride, using absorption of 177 and 532 nm photons to induce a pair of interfering paths. Excellent agreement between the observed and calculated phase shift as a function of the axial coordinate of the laser focus indicates that fragmentation occurs via a ladder switching mechanism. The axial dependence of the modulation depth is evidence of loss of coherence at higher internal temperatures of the molecule.

  2. Coherent control to prepare an InAs quantum dot for spin-photon entanglement.

    PubMed

    Webster, L A; Truex, K; Duan, L-M; Steel, D G; Bracker, A S; Gammon, D; Sham, L J

    2014-03-28

    We optically generated an electronic state in a single InAs/GaAs self-assembled quantum dot that is a precursor to the deterministic entanglement of the spin of the electron with an emitted photon in the proposal of W. Yao, R.-B. Liu, and L. J. Sham [Phys. Rev. Lett. 95, 030504 (2005). A superposition state is prepared by optical pumping to a pure state followed by an initial pulse. By modulating the subsequent pulse arrival times and precisely controlling them using interferometric measurement of path length differences, we are able to implement a coherent control technique to selectively drive exactly one of the two components of the superposition to the ground state. This optical transition contingent on spin was driven with the same broadband pulses that created the superposition through the use of a two pulse coherent control sequence. A final pulse affords measurement of the coherence of this "preentangled" state. PMID:24724666

  3. Coherent Control of Optically Generated and Detected Picosecond Surface Acoustic Phonons

    SciTech Connect

    David H. Hurley

    2006-11-01

    Coherent control of elementary optical excitations is a key issue in ultrafast materials science. Manipulation of electronic and vibronic excitations in solids as well as chemical and biological systems on ultrafast time scales has attracted a great deal of attention recently. In semiconductors, coherent control of vibronic excitations has been demonstrated for bulk acoustic and optical phonons generated in superlattice structures. The bandwidth of these approaches is typically fully utilized by employing a 1-D geometry where the laser spot size is much larger than the superlattice repeat length. In this presentation we demonstrate coherent control of optically generated picosecond surface acoustic waves using sub-optical wavelength absorption gratings. The generation and detection characteristics of two material systems are investigated (aluminum absorption gratings on Si and GaAs substrates).

  4. Coherent Control to Prepare an InAs Quantum Dot for Spin-Photon Entanglement

    NASA Astrophysics Data System (ADS)

    Webster, L. A.; Truex, K.; Duan, L.-M.; Steel, D. G.; Bracker, A. S.; Gammon, D.; Sham, L. J.

    2014-03-01

    We optically generated an electronic state in a single InAs /GaAs self-assembled quantum dot that is a precursor to the deterministic entanglement of the spin of the electron with an emitted photon in the proposal of W. Yao, R.-B. Liu, and L. J. Sham [Phys. Rev. Lett. 95, 030504 (2005).]. A superposition state is prepared by optical pumping to a pure state followed by an initial pulse. By modulating the subsequent pulse arrival times and precisely controlling them using interferometric measurement of path length differences, we are able to implement a coherent control technique to selectively drive exactly one of the two components of the superposition to the ground state. This optical transition contingent on spin was driven with the same broadband pulses that created the superposition through the use of a two pulse coherent control sequence. A final pulse affords measurement of the coherence of this "preentangled" state.

  5. 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

    2015-01-01

    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

  6. 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

  7. Cell cycle control of DNA joint molecule resolution.

    PubMed

    Wild, Philipp; Matos, Joao

    2016-06-01

    The establishment of stable interactions between chromosomes underpins vital cellular processes such as recombinational DNA repair and bipolar chromosome segregation. On the other hand, timely disengagement of persistent connections is necessary to assure efficient partitioning of the replicated genome prior to cell division. Whereas great progress has been made in defining how cohesin-mediated chromosomal interactions are disengaged as cells prepare to undergo chromosome segregation, little is known about the metabolism of DNA joint molecules (JMs), generated during the repair of chromosomal lesions. Recent work on Mus81 and Yen1/GEN1, two conserved structure-selective endonucleases, revealed unforeseen links between JM-processing and cell cycle progression. Cell cycle kinases and phosphatases control Mus81 and Yen1/GEN1 to restrain deleterious JM-processing during S-phase, while safeguarding chromosome segregation during mitosis. PMID:26970388

  8. Optical control of nonradiative decay in polyatomic molecules

    SciTech Connect

    Sukharev, Maxim; Seideman, Tamar

    2005-01-01

    We propose an approach for elimination of radiationless transitions in the excited states of polyatomic molecules. Our method is based on the concept of electronically localized eigenstates of coupled vibronic Hamiltonians--the occurrence of stationary eigenfunctions of essentially pure electronic character in the (otherwise strongly mixed) spectra of excited manifold Hamiltonians of systems undergoing nonradiative decay. The origin of this phenomenon and its generality are explained within the framework of the theory of scars of unstable periodic orbits. Optimal control theory is combined with the notion of electronically localized states to prepare the system in an excited superposition that is immune to nonradiative decay. The approach is applied to suppress ultrafast radiationless transitions in two model systems that differ widely in coupling strength and electronic structure.

  9. 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

  10. 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

  11. 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

    2016-01-01

    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

  12. 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.

  13. 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

  14. Coherent control of plasma dynamics by feedback-optimized wavefront manipulationa)

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

    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.

  16. Coherent control in quantum dot gain media using shaped pulses: a numerical study.

    PubMed

    Mishra, Akhilesh Kumar; Karni, Ouri; Eisenstein, Gadi

    2015-11-16

    We present a numerical study of coherent control in a room temperature InAs/InP quantum dot (QD) semiconductor optical amplifier (SOA) using shaped ultra-short pulses. Both the gain and absorption regimes were analyzed for pulses with central wavelengths lying on either side of the inhomogeneously broadened gain spectrum. The numerical experiments predict that in the gain regime the coherent interactions between a QD SOA and a pulse can be controlled by incorporating a quadratic spectral phase (QSP) in the pulse profile. The sequential interaction with the gain medium of different spectral components of the pulse results in either suppression or enhancement of the coherent signatures on the pulse profile depending upon their proximity to the gain spectrum peak. In the absorption regime, positive QSP induces a negative chirp that adds up to that of a two photon absorption induced Kerr-like effect resulting in pulse compression while negative QSP enhances dispersive broadening of the pulse. PMID:26698476

  17. 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.

  18. Coherently controlled adiabatic passage to multiple continuum channels

    SciTech Connect

    Thanopulos, Ioannis; Shapiro, Moshe

    2006-09-15

    We present a solution to the multichannel quantum control problem, where selective and complete population transfer from an initial bound state to M energetically degenerate continuum channels is achieved under loss-free conditions. The control is affected by adiabatic passage proceeding via N bound intermediate states, where even in the presence of real loss from these states, the control efficiency remains significant, about 40-50%. We illustrate the viability of the method by computationally controlling the CH{sub 3}(v)+I*({sup 2}P{sub 1/2})<-CH{sub 3}I{yields}CH{sub 3}(v)+I({sup 2}P{sub 3/2}) multichannel photodissociation process.

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

    PubMed

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

    2014-04-01

    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. PMID:24670656

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

    PubMed

    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

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

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

    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.

  2. Electroencephalographic coherence in Alzheimer's disease: comparisons with a control group and population norms.

    PubMed

    Knott, V; Mohr, E; Mahoney, C; Ilivitsky, V

    2000-01-01

    Previous research from independent laboratories has shown reduced electroencephalographic coherence in patients diagnosed with dementia of the Alzheimer type (DAT). This study added to this work by comparing interhemispheric and intrahemispheric coherence in nonmedicated DAT patients (n = 35) with that of a normal control group (n = 30), as well as with a data bank of population norms. Raw and Z-score transformed values showed reduced coherence, interhemispherically (in delta, theta, alpha, and beta bands) and intrahemispherically (delta and theta bands) in DAT patients with both comparison procedures. Discriminant analysis correctly classified 73% to 75% of patients. The results are discussed in relation to earlier research, "trait" versus "state" factors, the cholinergic system, and cognitive processes in dementia. PMID:10753001

  3. 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

  4. 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.

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

    PubMed

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

    2015-01-01

    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 the 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. PMID:25629223

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

    DOE PAGESBeta

    Li, Luozhou; Lu, Ming; Schroder, Tim; Chen, Edward H.; Walsh, Michael; Bayn, Igal; Goldstein, Jordan; Gaathon, Ophir; Trusheim, Matthew E.; Mower, Jacob; et al

    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

  7. 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.

  8. Small-molecule control of protein degradation using split adaptors

    PubMed Central

    Davis, Joseph H.; Baker, Tania A.; Sauer, Robert T.

    2011-01-01

    Targeted intracellular degradation provides a method to study the biological function of proteins and has numerous applications in biotechnology. One promising approach uses adaptor proteins to target substrates with genetically encoded degradation tags for proteolysis. Here, we describe an engineered split-adaptor system, in which adaptor assembly and delivery of substrates to the ClpXP protease depends on a small molecule (rapamycin). This degradation system does not require modification of endogenous proteases, functions robustly over a wide range of adaptor concentrations, and does not require new synthesis of adaptors or proteases to initiate degradation. We demonstrate the efficacy of this system in E. coli by degrading tagged variants of LacI repressor and FtsA, an essential cell-division protein. In the latter case, addition of rapamycin causes pronounced filamentation because daughter cells cannot divide. Strikingly, washing rapamycin away reverses this phenotype. Our system is highly modular, with clearly-defined interfaces for substrate binding, protease binding, and adaptor assembly, providing a clear path to extend this system to other degradation tags, proteases, or induction systems. Together, these new reagents should be useful in controlling protein degradation in bacteria. PMID:21866931

  9. Small-molecule control of protein degradation using split adaptors.

    PubMed

    Davis, Joseph H; Baker, Tania A; Sauer, Robert T

    2011-11-18

    Targeted intracellular degradation provides a method to study the biological function of proteins and has numerous applications in biotechnology. One promising approach uses adaptor proteins to target substrates with genetically encoded degradation tags for proteolysis. Here, we describe an engineered split-adaptor system, in which adaptor assembly and delivery of substrates to the ClpXP protease depends on a small molecule (rapamycin). This degradation system does not require modification of endogenous proteases, functions robustly over a wide range of adaptor concentrations, and does not require new synthesis of adaptors or proteases to initiate degradation. We demonstrate the efficacy of this system in E. coli by degrading tagged variants of LacI repressor and FtsA, an essential cell-division protein. In the latter case, addition of rapamycin causes pronounced filamentation because daughter cells cannot divide. Strikingly, washing rapamycin away reverses this phenotype. Our system is highly modular, with clearly defined interfaces for substrate binding, protease binding, and adaptor assembly, providing a clear path to extend this system to other degradation tags, proteases, or induction systems. Together, these new reagents should be useful in controlling protein degradation in bacteria. PMID:21866931

  10. Weak-field multiphoton femtosecond coherent control in the single-cycle regime.

    PubMed

    Chuntonov, Lev; Fleischer, Avner; Amitay, Zohar

    2011-03-28

    Weak-field coherent phase control of atomic non-resonant multiphoton excitation induced by shaped femtosecond pulses is studied theoretically in the single-cycle regime. The carrier-envelope phase (CEP) of the pulse, which in the multi-cycle regime does not play any control role, is shown here to be a new effective control parameter that its effect is highly sensitive to the spectral position of the ultrabroad spectrum. Rationally chosen position of the ultrabroadband spectrum coherently induces several groups of multiphoton transitions from the ground state to the excited state of the system: transitions involving only absorbed photons as well as Raman transitions involving both absorbed and emitted photons. The intra-group interference is controlled by the relative spectral phase of the different frequency components of the pulse, while the inter-group interference is controlled jointly by the CEP and the relative spectral phase. Specifically, non-resonant two- and three-photon excitation is studied in a simple model system within the perturbative frequency-domain framework. The developed intuition is then applied to weak-field multiphoton excitation of atomic cesium (Cs), where the simplified model is verified by non-perturbative numerical solution of the time-dependent Schrödinger equation. We expect this work to serve as a basis for a new line of femtosecond coherent control experiments. PMID:21451714

  11. 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

  12. 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.

  13. Inverse Doppler shift and control field as coherence generators for the stability in superluminal light

    NASA Astrophysics Data System (ADS)

    Ghafoor, Fazal; Bacha, Bakht Amin; Khan, Salman

    2015-05-01

    A gain-based four-level atomic medium for the stability in superluminal light propagation using control field and inverse Doppler shift as coherence generators is studied. In regimes of weak and strong control field, a broadband and multiple controllable transparency windows are, respectively, identified with significantly enhanced group indices. The observed Doppler effect for the class of high atomic velocity of the medium is counterintuitive in comparison to the effect of the class of low atomic velocity. The intensity of each of the two pump fields is kept less than the optimum limit reported in [M. D. Stenner and D. J. Gauthier, Phys. Rev. A 67, 063801 (2003), 10.1103/PhysRevA.67.063801] for stability in the superluminal light pulse. Consequently, superluminal stable domains with the generated coherence are explored.

  14. Optimal control of the population dynamics of the ground vibrational state of a polyatomic molecule

    NASA Astrophysics Data System (ADS)

    de Clercq, Ludwig E.; Botha, Lourens R.; Rohwer, Erich G.; Uys, Hermann; Du Plessis, Anton

    2011-03-01

    Simulating coherent control with femtosecond pulses on a polyatomic molecule with anharmonic splitting was demonstrated. The simulation mimicked pulse shaping of a Spatial Light Modulator (SLM) and the interaction was described with the Von Neumann equation. A transform limited pulse with a fluence of 600 J/m2 produced 18% of the population in an arbitrarily chosen upper vibrational state, n =2. Phase only and amplitude only shaped pulse produced optimum values of 60% and 40% respectively, of the population in the vibrational state, n=2, after interaction with the ultra short pulse. The combination of phase and amplitude shaping produced the best results, 80% of the population was in the targeted vibrational state, n=2, after interaction. These simulations were carried out with all the population initially in the ground vibrational level. It was found that even at room temperatures (300 Kelvin) that the population in the selected level is comparable with the case where all population is initially in the ground vibrational state. With a 10% noise added to the amplitude and phase masks, selective excitation of the targeted vibrational state is still possible.

  15. 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.

  16. 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

  17. Complete photoionization experiments via ultrafast coherent control with polarization multiplexing.

    PubMed

    Hockett, P; Wollenhaupt, M; Lux, C; Baumert, T

    2014-06-01

    Photoelectron angular distributions (PADs) obtained from ionization of potassium atoms using moderately intense femtosecond IR fields (∼10^{12}  W cm^{-2}) of various polarization states are shown to provide a route to "complete" photoionization experiments. Ionization occurs by a net three-photon absorption process, driven via the 4s→4p resonance at the one-photon level. A theoretical treatment incorporating the intrapulse electronic dynamics allows for a full set of ionization matrix elements to be extracted from 2D imaging data. 3D PADs generated from the extracted matrix elements are also compared to experimental, tomographically reconstructed, 3D photoelectron distributions, providing a sensitive test of their validity. Finally, application of the determined matrix elements to ionization via more complex, polarization-shaped, pulses is demonstrated, illustrating the utility of this methodology towards detailed understanding of complex ionization control schemes and suggesting the utility of such "multiplexed" intrapulse processes as powerful tools for measurement. PMID:24949763

  18. 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.

  19. 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…

  20. 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.

  1. 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. PMID:26196826

  2. 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

  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. 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. PMID:22452090

  6. Coherent control of a transmon qubit with a nanowire-based Josephson junction

    NASA Astrophysics Data System (ADS)

    Larsen, T. W.; Petersson, K. D.; Kuemmeth, F.; Jespersen, T. S.; Krogstrup, P.; Nygård, J.; Marcus, C. M.

    2015-03-01

    Transmon qubits have taken great leaps towards realizing a quantum processor. Here we present measurements on a novel, gateable transmon. By tuning the electron density in a semiconducting nanowire Josephson junction we can control the qubit frequency from ~3 GHz to ~8 GHz. The transmon was embedded into an aluminum coplanar waveguide cavity for readout and qubit control. In the resonant regime we observe strong cavity-qubit coupling. In the dispersive regime we demonstrate coherent control on the Bloch sphere. The life- and coherence times were measured to T2* ~ 2T1 ~ 1 μ s. The coherence time was measured to almost 1 μs. Fast gate operations facilitate z-rotations as well as promising fast two-qubit operations in future multiple-qubit devices. These measurements open new possibilities for gateable superconducting qubits and promise a plausible system for Majorana hybrid devices. Research supported by Microsoft Station Q, Danish National Research Foundation, Villum Foundation, Lundbeck Foundation, and the European Commission.

  7. 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

  8. Coherent beam combining of pulsed fibre amplifiers with active phase control

    SciTech Connect

    Wang, X L; Zhou, Pu; Ma, Y X; Ma, H T; Xu, X J; Liu, Z J; Zhao, Y J

    2011-12-31

    Coherent beam combining of pulsed fibre lasers is a promising method for power scaling while simultaneously maintaining good beam quality. We propose and demonstrate a scalable architecture for coherent beam combining of all-fibre pulsed amplifiers with active phase control using the stochastic parallel gradient descent (SPGD) algorithm. A low-pass filter is introduced to eliminate the fluctuation of the metric function caused by pulsed lasers and to extract the exact phase noise signal. Active control is thereby based on the SPGD algorithm, resulting in stable coherent beam combining at the receiving plane even in a turbulent environment. Experimental results show that the fringe visibility of the long exposure pattern increases from 0 to 0.4, and the power encircled in the main-lobe increases by 1.6 times when the system evolves from the open-loop phase-locking scheme to the closed-loop scheme. This architecture can be easily scaled up to a higher power by increasing the number of amplifying channels and the power of a single amplifier.

  9. Ultrafast dynamics of coherent optical phonons in GeTe/Sb2Te3 superlattices: thermal conductivity and coherent control

    NASA Astrophysics Data System (ADS)

    Hase, Muneaki; Tominaga, Junji

    2012-03-01

    We report on the evaluation of lattice thermal conductivity of GeTe/Sb2Te3 superlattice (SL) by using a coherent phonon spectroscopy at various lattice temperatures. The time-resolved transient reflectivity obtained in amorphous and crystalline GeTe/Sb2Te3 SL films exhibits the coherent A1 optical modes at terahertz (THz) frequencies with picoseconds dephasing time. The relaxation time and frequency of the coherent A1 modes are used to compute the lattice thermal conductivity based on the Debye theory, including scattering by grain boundary and point defect, umklapp process, and phonon resonant scattering. The results indicate that the thermal conductivity in the amorphous SL film is less temperature dependent, due to the dominant phonon-defect scattering, while in the crystalline SL it is temperature dependent because of the main contributions from umklapp and phonon resonant scatterings. We argue the higher thermal conductivity in the GeTe/Sb2Te3 SL films than that in the Ge2Sb2Te5 alloy films implies that the phase change in GeTe/Sb2Te3 SL is not purely promoted by thermal process, i.e., lattice heating, but rather by nonthermal process, i.e., coherent lattice excitation, because the thermal process generally requires lower thermal conductivity.

  10. Controllable cavity linewidth narrowing via spontaneously generated coherence in a four level atomic system

    NASA Astrophysics Data System (ADS)

    Tian, Si-Cong; Wan, Ren-Gang; Shan, Xiao-Nan; Tong, Cun-Zhu; Qin, Li; Ning, Yong-Qiang

    2015-12-01

    A scheme for cavity linewidth narrowing in a four-level atomic system with spontaneously generated coherence is proposed. The atomic system consists of three closely spaced excited levels, which decay to one common ground level. In such a system, spontaneously generated coherence can result in the appearance of two narrow transparency windows accomplished by steep normal dispersion. When the medium is embedded in a ring cavity, two ultranarrow transmission peaks locating close to the position of the transparency windows can be obtained simultaneously. The cavity linewidth narrowing is owing to the quantum interference between the three decay channels and can be controlled by the frequency splitting of the excited levels, requiring no coupling lasers.

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

    PubMed

    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. PMID:25437256

  12. 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.

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

    PubMed

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

    2016-06-24

    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. PMID:27391722

  14. 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.

  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. 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.

  17. Ultrafast Coherent Control of a Single Electron Spin in a Quantum Dot

    NASA Astrophysics Data System (ADS)

    Mikkelsen, Maiken H.

    2009-03-01

    Practical quantum information processing schemes require fast single-qubit operations. For spin-based qubits, this involves performing arbitrary coherent rotations of the spin state on timescales much faster than the spin coherence time. While we recently demonstrated the ability to initialize and monitor the evolution of single spins in quantum dots (QDs)ootnotetextM. H. Mikkelsen, J. Berezovsky, N. G. Stoltz, L. A. Coldren, D. D. Awschalom, Nature Physics 3, 770 (2007); J. Berezovsky, M. H. Mikkelsen, O. Gywat, N. G. Stoltz, L. A. Coldren, and D. D. Awschalom, Science 314, 1916 (2006)., here we present an all-optical scheme for ultrafast manipulation of these states through arbitrary angles. The GaAs QDs are embedded in a diode structure to allow controllable charging of the QDs and positioned within a vertical optical cavity to enhance the small single spin signal. By applying off-resonant optical pulses, we coherently rotate a single electron spin in a QD up to π radians on picosecond timescales ootnotetextJ. Berezovsky, M. H. Mikkelsen, N. G. Stoltz, L. A. Coldren, D. D. Awschalom, Science 320, 349 (2008)..We directly observe this spin manipulation using time-resolved Kerr rotation spectroscopy at T=10K. Measurements of the spin rotation as a function of laser detuning and intensity confirm that the optical Stark effect is the operative mechanism and the results are well-described by a model including the electron-nuclear spin interaction. Using short tipping pulses, this technique enables one to perform a large number of operations within the coherence time. This ability to perform arbitrary single-qubit operations enables sequential all-optical initialization, ultrafast control and detection of a single electron spin for quantum information purposes.

  18. Advantages of the coherent antistokes Raman scattering (CARS) in environmental monitoring and industrial process control

    NASA Astrophysics Data System (ADS)

    Voss, Eberhard; de Vries, Thorsten; Darpel, H.; Anders, Angelika

    1999-02-01

    The objective of this investigation was to develop a fast method for the in-situ characterization of chemicals solved in water based on Coherent Antistokes Raman Scattering (CARS). In order to test the potential of CARS as a tool for the in-situ spectroscopy scanning and multiplex CARS techniques were investigated. Polarization CARS (PCARS) was used to reduce the nonvibrational resonant signal generated by the electron cloud of the solvent molecules. The spectra of some alcohols and pollutants such as pyridine, nitrate and sulfate were investigated. Computer simulations were applied for the evaluation of the CARS spectra. The most evident advantage of CARS in comparison with other Raman methods is the very short time to achieve a spectrum. The shortest time to get a spectrum is limited by the length of the laser pulse (e.g. 5 ns). In addition no sample preparation is necessary.

  19. 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.

  20. Effects of molecule anchoring and dispersion on nanoscopic friction under electrochemical control.

    PubMed

    de Wijn, A S; Fasolino, A; Filippov, A E; Urbakh, M

    2016-03-16

    The application of electric fields is a promising strategy for in situ control of friction. While there have recently been many experimental studies on friction under the influence of electric fields, theoretical understanding is very limited. Recently, we introduced a simple theoretical model for friction under electrochemical conditions that focused on the interaction of a force microscope tip with adsorbed molecules whose orientation was dependent on the applied electric field. Here we focus on the effects of anchoring of the molecules on friction. We show that anchoring affects the intensity and width of the peak in the friction that occurs near a reorientation transition of adsorbed molecules, and explain this by comparing the strength of molecule-molecule and molecule-tip interactions. We derive a dispersion relation for phonons in the layer of adsorbed molecules and demonstrate that it can be used to understand important features of the frictional response. PMID:26871411

  1. Pupil shaping and coherence control in an EUV mask-imaging microscope

    NASA Astrophysics Data System (ADS)

    Mochi, Iacopo; Goldberg, Kenneth A.; Benk, Markus P.; Naulleau, Patrick P.

    2013-09-01

    We are investigating the effect of pupil-fill patterns and partial coherence settings on EUV reticle images on the new SEMATECH High-NA Actinic Reticle review Project (SHARP), to deepen our understanding of its performance, and improve the emulation of image formation in arbitrary printing tools. SHARP is an EUV mask microscope developed as the successor of the SEMATECH Berkeley Actinic Inspection Tool (AIT). It is equipped with a unique, MEMS-based Fourier synthesis illuminator that generates arbitrary, customized pupil fill patterns to control the illumination partial coherence. The high-magnification objective lenses are an array of interchangeable Fresnel zoneplates with 4×NA values ranging from 0.25 to 0.625. We have used SHARP to inspect isolated and dense features with half pitch as low as 55 nm using lenses with a range of NA values, and common illumination patterns, such as annular, dipole and QUASAR™. We will show the effect of illumination on important, measured pattern parameters, including contrast, normalized image log-slope, and depth of focus. We have also studied the effect of partial coherence on the imaging of on multilayer roughness observed in bright mask regions, a topic important for expanding our understanding of the causes of LER.

  2. Influence of polymer-molecule/wall interactions on mobility control

    SciTech Connect

    Duda, J.L.; Klaus, E.E.; Fan, S.K.

    1981-10-01

    This study presents the results of a study of molecule/wall interactions on permeability modification of consolidated porous media by polymer solutions. The experiments were conducted with a newly developed low-shear porous media viscometer. The key for obtaining reproducible, steady-state results was to expose the porous medium to several hundred pore volumes of polymer solution to saturate it with polymer. The effective permeability during polymer flow and the residual permeability were determined for xanthan gum and polyacrylamide solutions in Berea sandstone, Bradford sandstone, filter papers, and Nuclepore filters. 25 refs.

  3. 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.

  4. 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.

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

    SciTech Connect

    Schüler, Michael Berakdar, Jamal

    2014-04-21

    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.

  6. Coherent dynamics of singlet fission controlled by nonlocal electron-phonon coupling

    NASA Astrophysics Data System (ADS)

    Yao, Yao

    2016-03-01

    Based on the Frenkel and charge transfer mixing model of singlet fission (SF), we incorporate both the local and nonlocal phonon baths into the Hamiltonian and adopt the algorithm of the time-dependent density matrix renormalization group to simulate the SF process in tetracene and pentacene. The endergonic SF is found to be facilitated by the robust quantum coherence, which concurrently gives rise to a notable quantum beating effect. Being controlled by the nonlocal electron-phonon coupling, the SF process is accelerated and the triplet yield manifests a nonlinear relationship with the singlet density.

  7. Coherent state transfer through a multi-channel quantum network: Natural versus controlled evolution passage

    NASA Astrophysics Data System (ADS)

    Chen, Bing; Li, Yong

    2016-04-01

    Quantum state transfer (QST) is an important task in quantum information processing. In this study, we describe two approaches for the high-fidelity transfer of a quantum state between two opposite quantum dots attached to a multi-channel quantum network. First, we demonstrate that a high-efficiency QST can be achieved with the coherent time evolution of a quantum system without any external control. Second, we present an approach that uses an alternative mechanism for a high-fidelity QST. By adiabatically varying tunnel couplings, it is possible to implement the complete transmission of a quantum state based on this quantum mechanical mechanism.

  8. 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

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

    PubMed

    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

  10. Cell adhesion molecule control of planar spindle orientation.

    PubMed

    Tuncay, Hüseyin; Ebnet, Klaus

    2016-03-01

    Polarized epithelial cells align the mitotic spindle in the plane of the sheet to maintain tissue integrity and to prevent malignant transformation. The orientation of the spindle apparatus is regulated by the immobilization of the astral microtubules at the lateral cortex and depends on the precise localization of the dynein-dynactin motor protein complex which captures microtubule plus ends and generates pulling forces towards the centrosomes. Recent developments indicate that signals derived from intercellular junctions are required for the stable interaction of the dynein-dynactin complex with the cortex. Here, we review the molecular mechanisms that regulate planar spindle orientation in polarized epithelial cells and we illustrate how different cell adhesion molecules through distinct and non-overlapping mechanisms instruct the cells to align the mitotic spindle in the plane of the sheet. PMID:26698907