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Sample records for quantum recoil effects

  1. Quantum recoil and Bohm diffusion

    SciTech Connect

    Melrose, D. B.; Mushtaq, A.

    2009-09-15

    It is argued that the inclusion of the Bohm potential in quantum fluid equations is equivalent to inclusion of a nonrelativistic form of the quantum recoil in plasma kinetic theory. The Bohm term is incorrect when applied to waves with phase speed greater than the speed of light.

  2. Charge transport-induced recoil and dissociation in double quantum dots.

    PubMed

    Pozner, Roni; Lifshitz, Efrat; Peskin, Uri

    2014-11-12

    Colloidal quantum dots (CQDs) are free-standing nanostructures with chemically tunable electronic properties. This combination of properties offers intriguing new possibilities for nanoelectromechanical devices that were not explored yet. In this work, we consider a new scanning tunneling microscopy setup for measuring ligand-mediated effective interdot forces and for inducing motion of individual CQDs within an array. Theoretical analysis of a double quantum dot structure within this setup reveals for the first time voltage-induced interdot recoil and dissociation with pronounced changes in the current. Considering realistic microscopic parameters, our approach enables correlating the onset of mechanical motion under bias voltage with the effective ligand-mediated binding forces. PMID:25259800

  3. Dielectric barrier structure with hollow electrodes and its recoil effect

    NASA Astrophysics Data System (ADS)

    Yu, Shuang; Chen, Qunzhi; Liu, Jiahui; Wang, Kaile; Jiang, Zhe; Sun, Zhili; Zhang, Jue; Fang, Jing

    2015-06-01

    A dielectric barrier structure with hollow electrodes (HEDBS), in which gas flow oriented parallel to the electric field, was proposed. Results showed that with this structure, air can be effectively ignited, forming atmospheric low temperature plasma, and the proposed HEDBS could achieve much higher electron density (5 1015/cm3). It was also found that the flow condition, including outlet diameter and flow rate, played a key role in the evolution of electron density. Optical emission spectroscopy diagnostic results showed that the concentration of reactive species had the same variation trend as the electron density. The simulated distribution of discharge gas flow indicated that the HEDBS had a strong recoil effect on discharge gas, and could efficiently promote generating electron density as well as reactive species.

  4. Dielectric barrier structure with hollow electrodes and its recoil effect

    SciTech Connect

    Yu, Shuang; Chen, Qunzhi; Liu, Jiahui; Wang, Kaile; Jiang, Zhe; Sun, Zhili; Zhang, Jue; Fang, Jing

    2015-06-15

    A dielectric barrier structure with hollow electrodes (HEDBS), in which gas flow oriented parallel to the electric field, was proposed. Results showed that with this structure, air can be effectively ignited, forming atmospheric low temperature plasma, and the proposed HEDBS could achieve much higher electron density (5 × 10{sup 15}/cm{sup 3}). It was also found that the flow condition, including outlet diameter and flow rate, played a key role in the evolution of electron density. Optical emission spectroscopy diagnostic results showed that the concentration of reactive species had the same variation trend as the electron density. The simulated distribution of discharge gas flow indicated that the HEDBS had a strong recoil effect on discharge gas, and could efficiently promote generating electron density as well as reactive species.

  5. Hadronic effects and observables in B ?? ?+?- decay at large recoil

    NASA Astrophysics Data System (ADS)

    Hambrock, Christian; Khodjamirian, Alexander; Rusov, Aleksey

    2015-10-01

    We calculate the amplitude of the rare flavor-changing neutral-current decay B ?? ?+?- at large recoil of the pion. The nonlocal contributions in which the weak effective operators are combined with the electromagnetic lepton-pair emission are systematically taken into account. These amplitudes are calculated at off-shell values of the lepton-pair mass squared, q2<0 , employing the operator-product expansion, QCD factorization and light-cone sum rules. The results are fitted to hadronic dispersion relations in q2, including the intermediate vector meson contributions. The dispersion relations are then used in the physical region q2>0 . Our main result is the process-dependent addition ? C9(B ? )(q2) to the Wilson coefficient C9 obtained at 4 m?2

  6. Effect of recoil atoms on resolution in ion-beam lithography

    NASA Astrophysics Data System (ADS)

    Karapiperis, L.; Dieumegard, D.; Adesida, I.

    1983-05-01

    A previously developed computer simulation scheme of the Monte Carlo type which provides implantation and energy-loss distributions of ions implanted in amorphous materials is extended to include recoils. Damage produced by such recoil atoms can thus be simulated. Theoretical results are obtained using the Kalbitzer and Oetzmann empirical nuclear scattering potential. In the present work, primarily results concerning the effect of the inclusion of recoil atoms on the deposited energy distributions in organic resist materials are presented. In the case of heavy ions with energies in the range 200-300 keV there is a significant number of recoil atoms with energies of up to several keV. Our extended Monte Carlo simulation scheme is applied in the study of the effect of recoils on the lithographic resolution of focused ion-beam resist exposure, and in particular the effect of the inclusion of recoils in the case of Ga + exposed PMMA. The model is also applied in a number of other cases such as damage produced in Si by Sb implantation, and recoil implantation of Al in Si.

  7. Quantum effects in electron beam pumped GaAs

    SciTech Connect

    Yahia, M. E.; National Institute of Laser Enhanced Sciences , Cairo University ; Azzouz, I. M.; Moslem, W. M.

    2013-08-19

    Propagation of waves in nano-sized GaAs semiconductor induced by electron beam are investigated. A dispersion relation is derived by using quantum hydrodynamics equations including the electrons and holes quantum recoil effects, exchange-correlation potentials, and degenerate pressures. It is found that the propagating modes are instable and strongly depend on the electron beam parameters, as well as the quantum recoil effects and degenerate pressures. The instability region shrinks with the increase of the semiconductor number density. The instability arises because of the energetic electron beam produces electron-hole pairs, which do not keep in phase with the electrostatic potential arising from the pair plasma.

  8. Nuclear Recoil Effect in the Lamb Shift of Light Hydrogenlike Atoms

    NASA Astrophysics Data System (ADS)

    Yerokhin, V. A.; Shabaev, V. M.

    2015-12-01

    We report high-precision calculations of the nuclear recoil effect to the Lamb shift of hydrogenlike atoms to the first order in the electron-nucleus mass ratio and to all orders in the nuclear binding strength parameter Z ? . The results are in excellent agreement with the known terms of the Z ? expansion and allow an accurate identification of the nonperturbative higher-order remainder. For hydrogen, the higher-order remainder was found to be much larger than anticipated. This result resolves the long-standing disagreement between the numerical all-order and analytical Z ? -expansion approaches to the recoil effect and completely removes the second-largest theoretical uncertainty in the hydrogen Lamb shift of the 1 S and 2 S states.

  9. Nuclear Recoil Effect in the Lamb Shift of Light Hydrogenlike Atoms.

    PubMed

    Yerokhin, V A; Shabaev, V M

    2015-12-01

    We report high-precision calculations of the nuclear recoil effect to the Lamb shift of hydrogenlike atoms to the first order in the electron-nucleus mass ratio and to all orders in the nuclear binding strength parameter Z?. The results are in excellent agreement with the known terms of the Z? expansion and allow an accurate identification of the nonperturbative higher-order remainder. For hydrogen, the higher-order remainder was found to be much larger than anticipated. This result resolves the long-standing disagreement between the numerical all-order and analytical Z?-expansion approaches to the recoil effect and completely removes the second-largest theoretical uncertainty in the hydrogen Lamb shift of the 1S and 2S states. PMID:26684115

  10. Nuclear recoil and vacuum-polarization effects on the binding energies of supercritical H-like ions

    NASA Astrophysics Data System (ADS)

    Aleksandrov, Ivan A.; Plunien, Gnter; Shabaev, Vladimir M.

    2016-01-01

    The Dirac Hamiltonian including nuclear recoil and vacuum-polarization operators is considered in a supercritical regime Z> 137. It is found that the nuclear recoil operator derived within the Breit approximation "regularizes" the Hamiltonian for the point-nucleus model and allows the ground state level to go continuously down and reach the negative energy continuum at a critical value Zcr ? 145. If the Hamiltonian contains both the recoil operator and the Uehling potential, the 1s level reaches the negative energy continuum at Zcr ? 144. The corresponding calculations for the excited states have been also performed. This study shows that, in contrast to previous investigations, a point-like nucleus can have effectively the charge Z> 137.

  11. Frequency-Dependent Polarizability of Helium Including Relativistic Effects with Nuclear Recoil Terms

    NASA Astrophysics Data System (ADS)

    Piszczatowski, Konrad; Puchalski, Mariusz; Komasa, Jacek; Jeziorski, Bogumi?; Szalewicz, Krzysztof

    2015-05-01

    Future metrology standards will be partly based on physical quantities computed from first principles rather than measured. In particular, a new pressure standard can be established if the dynamic polarizability of helium can be determined from theory with an uncertainty smaller than 0.2 ppm. We present calculations of the frequency-dependent part of this quantity including relativistic effects with full account of leading nuclear recoil terms and using highly optimized explicitly correlated basis sets. A particular emphasis is put on uncertainty estimates. At the He-Ne laser wavelength of 632.9908 nm, the computed polarizability value of 1.39181141 a.u. has uncertainty of 0.1 ppm that is 2 orders of magnitude smaller than those of the most accurate polarizability measurements. We also obtained an accurate expansion of the helium refractive index in powers of density.

  12. Quantum Radiation Reaction Effects in Multiphoton Compton Scattering

    SciTech Connect

    Di Piazza, A.; Hatsagortsyan, K. Z.; Keitel, C. H.

    2010-11-26

    Radiation reaction effects in the interaction of an electron and a strong laser field are investigated in the realm of quantum electrodynamics. We identify the quantum radiation reaction with the multiple photon recoils experienced by the laser-driven electron due to consecutive incoherent photon emissions. After determining a quantum radiation dominated regime, we demonstrate how in this regime quantum signatures of the radiation reaction strongly affect multiphoton Compton scattering spectra and that they could be measurable in principle with presently available laser technology.

  13. Effect of a target size on the recoil momentum upon laser irradiation of absorbing materials

    SciTech Connect

    Chumakou, A N; Petrenko, A M; Bosak, N A

    2004-10-31

    The dependence of a recoil momentum on the radius of a target irradiated by a single-pulse Nd{sup 3+}:YAG laser ({lambda}=1.064 {mu}m, {tau}=20 ns, E{<=}300 mJ) in the air is studied. The recoil momentum decreases three-fold with increasing the relative target radius from 0.3 to 5 and tends to saturation for r>3. The calculation of the recoil momentum on the basis of the Euler and Navier-Stokes equations gave understated values for r>1, which lowered to negative values. The reasons for the qualitative discrepancy between the experimental and calculated data is discussed. (interaction of laser radiation with matter)

  14. 7Be recoil implantation for ultra-thin-layer-activation of medical grade polyethylene: Effect on wear resistance

    NASA Astrophysics Data System (ADS)

    Hoffmann, M.; Abbas, K.; Sauvage, T.; Blondiaux, G.; Vincent, L.; Stroosnijder, M. F.

    2001-10-01

    Wear of ultra-high-molecular-weight-polyethylene (UHMWPE) is usually measured by gravimetric methods making laboratory wear tests a time consuming exercise. Methods for the determination of polyethylene wear with a higher sensitivity would reduce test times and costs. One of these alternative methods is ultra-thin-layer-activation (UTLA), which relies on recoil implantation of heavy radioactive nuclei, such as 7Be, by using light mass particle beams. However, the possibility of damages within the polyethylene surface, which would have consequences on its wear behavior, cannot be excluded. In this work the effect of an implantation of 7Be on wear of a medical grade UHMWPE was studied using a block-on-cylinder screening wear tester. The results show that the implantation of UHMWPE with 7Be recoils under the implantation conditions chosen does not alter the tribological behavior of medical grade UHMWPE.

  15. Temperature Dependence and Recoil-free Fraction Effects in Olivines Across the Mg-Fe Solid Solution

    NASA Technical Reports Server (NTRS)

    Sklute, E. C.; Rothstein, Y.; Dyar, M. D.; Schaefer, M. W.; Menzies, O. N.; Bland, P. A.; Berry, F. J.

    2005-01-01

    Olivine and pyroxene are the major ferromagnesian minerals in most meteorite types and in mafic igneous rocks that are dominant at the surface of the Earth. It is probable that they are the major mineralogical components at the surface of any planetary body that has undergone differentiation processes. In situ mineralogical studies of the rocks and soils on Mars suggest that olivine is a widespread mineral on that planet s surface (particularly at the Gusev site) and that it has been relatively unaffected by alteration. Thus an understanding of the characteristics of Mossbauer spectra of olivine is of great importance in interpreting MER results. However, variable temperature Mossbauer spectra of olivine, which are needed to quantify recoil-free fraction effects and to understand the temperature dependence of olivine spectra, are lacking in the literature. Thus, we present here a study of the temperature dependence and recoil-free fraction of a series of synthetic olivines.

  16. Molecular modeling of the effects of 40Ar recoil in illite particles on their K-Ar isotope dating

    NASA Astrophysics Data System (ADS)

    Szczerba, Marek; Derkowski, Arkadiusz; Kalinichev, Andrey G.; Środoń, Jan

    2015-06-01

    The radioactive decay of 40K to 40Ar is the basis of isotope age determination of micaceous clay minerals formed during diagenesis. The difference in K-Ar ages between fine and coarse grained illite particles has been interpreted using detrital-authigenic components system, its crystallization history or post-crystallization diffusion. Yet another mechanism should also be considered: natural 40Ar recoil. Whether this recoil mechanism can result in a significant enough loss of 40Ar to provide observable decrease of K-Ar age of the finest illite crystallites at diagenetic temperatures - is the primary objective of this study which is based on molecular dynamics (MD) computer simulations. All the simulations were performed for the same kinetic energy (initial velocity) of the 40Ar atom, but for varying recoil angles that cover the entire range of their possible values. The results show that 40Ar recoil can lead to various deformations of the illite structure, often accompanied by the displacement of OH groups or breaking of the Si-O bonds. Depending on the recoil angle, there are four possible final positions of the 40Ar atom with respect to the 2:1 layer at the end of the simulation: it can remain in the interlayer space or end up in the closest tetrahedral, octahedral or the opposite tetrahedral sheet. No simulation angles were found for which the 40Ar atom after recoil passes completely through the 2:1 layer. The energy barrier for 40Ar passing through the hexagonal cavity from the tetrahedral sheet into the interlayer was calculated to be 17 kcal/mol. This reaction is strongly exothermic, therefore there is almost no possibility for 40Ar to remain in the tetrahedral sheet of the 2:1 layer over geological time periods. It will either leave the crystal, if close enough to the edge, or return to the interlayer space. On the other hand, if 40Ar ends up in the octahedral sheet after recoil, a substantially higher energy barrier of 55 kcal/mol prevents it from leaving the TOT layer over geological time. Based on the results of MD simulations, the estimates of the potential effect of 40Ar recoil on the K-Ar dating of illite show that some of 40Ar is lost and the loss is substantially dependent on the crystallite dimensions. The 40Ar loss can vary from 10% for the finest crystallites (two 2:1 layers thickness and <0.02 μm in diameter) to close to zero for the thickest and largest (in the ab plane) ones. Because the decrease of the K-Ar estimated age is approximately proportional to the 40Ar loss, the finer crystallites show lower apparent age than the coarser ones, although the age of crystallization is assumed equal for all the crystallites. From the model it is also clear that the lack of K removal from illite fringes (potentially Ar-free) strongly increases the apparent age differences among crystallites of different size.

  17. Quantum Hall effect in quantum electrodynamics

    SciTech Connect

    Penin, Alexander A.

    2009-03-15

    We consider the quantum Hall effect in quantum electrodynamics and find a deviation from the quantum-mechanical prediction for the Hall conductivity due to radiative antiscreening of electric charge in an external magnetic field. A weak dependence of the universal von Klitzing constant on the magnetic field strength, which can possibly be observed in a dedicated experiment, is predicted.

  18. Potential effects of alpha-recoil on uranium-series dating of calcrete

    USGS Publications Warehouse

    Neymark, L.A.

    2011-01-01

    Evaluation of paleosol ages in the vicinity of Yucca Mountain, Nevada, at the time the site of a proposed high-level nuclear waste repository, is important for fault-displacement hazard assessment. Uranium-series isotope data were obtained for surface and subsurface calcrete samples from trenches and boreholes in Midway Valley, Nevada, adjacent to Yucca Mountain. 230Th/U ages of 33 surface samples range from 1.3 to 423 thousand years (ka) and the back-calculated 234U/238U initial activity ratios (AR) are relatively constant with a mean value of 1.54 0.15 (1?), which is consistent with the closed-system behavior. Subsurface calcrete samples are too old to be dated by the 230Th/U method. U-Pb data for post-pedogenic botryoidal opal from a subsurface calcrete sample show that these subsurface calcrete samples are older than ~ 1.65 million years (Ma), old enough to have attained secular equilibrium had their U-Th systems remained closed. However, subsurface calcrete samples show U-series disequilibrium indicating open-system behavior of 238U daughter isotopes, in contrast with the surface calcrete, where open-system behavior is not evident. Data for 21 subsurface calcrete samples yielded calculable 234U/238U model ages ranging from 130 to 1875 ka (assuming an initial AR of 1.54 0.15, the mean value calculated for the surface calcrete samples). A simple model describing continuous ?-recoil loss predicts that the 234U/238U and 230Th/238U ARs reach steady-state values ~ 2 Ma after calcrete formation. Potential effects of open-system behavior on 230Th/U ages and initial 234U/238U ARs for younger surface calcrete were estimated using data for old subsurface calcrete samples with the 234U loss and assuming that the total time of water-rock interaction is the only difference between these soils. The difference between the conventional closed-system and open-system ages may exceed errors of the calculated conventional ages for samples older than ~ 250 ka, but is negligible for younger soils.

  19. Quantum Effects in Biology

    NASA Astrophysics Data System (ADS)

    Mohseni, Masoud; Omar, Yasser; Engel, Gregory S.; Plenio, Martin B.

    2014-08-01

    List of contributors; Preface; Part I. Introduction: 1. Quantum biology: introduction Graham R. Fleming and Gregory D. Scholes; 2. Open quantum system approaches to biological systems Alireza Shabani, Masoud Mohseni, Seogjoo Jang, Akihito Ishizaki, Martin Plenio, Patrick Rebentrost, Alàn Aspuru-Guzik, Jianshu Cao, Seth Lloyd and Robert Silbey; 3. Generalized Förster resonance energy transfer Seogjoo Jang, Hoda Hossein-Nejad and Gregory D. Scholes; 4. Multidimensional electronic spectroscopy Tomáš Mančal; Part II. Quantum Effects in Bacterial Photosynthetic Energy Transfer: 5. Structure, function, and quantum dynamics of pigment protein complexes Ioan Kosztin and Klaus Schulten; 6. Direct observation of quantum coherence Gregory S. Engel; 7. Environment-assisted quantum transport Masoud Mohseni, Alàn Aspuru-Guzik, Patrick Rebentrost, Alireza Shabani, Seth Lloyd, Susana F. Huelga and Martin B. Plenio; Part III. Quantum Effects in Higher Organisms and Applications: 8. Excitation energy transfer in higher plants Elisabet Romero, Vladimir I. Novoderezhkin and Rienk van Grondelle; 9. Electron transfer in proteins Spiros S. Skourtis; 10. A chemical compass for bird navigation Ilia A. Solov'yov, Thorsten Ritz, Klaus Schulten and Peter J. Hore; 11. Quantum biology of retinal Klaus Schulten and Shigehiko Hayashi; 12. Quantum vibrational effects on sense of smell A. M. Stoneham, L. Turin, J. C. Brookes and A. P. Horsfield; 13. A perspective on possible manifestations of entanglement in biological systems Hans J. Briegel and Sandu Popescu; 14. Design and applications of bio-inspired quantum materials Mohan Sarovar, Dörthe M. Eisele and K. Birgitta Whaley; 15. Coherent excitons in carbon nanotubes Leonas Valkunas and Darius Abramavicius; Glossary; References; Index.

  20. The effect of recoil pressure in the ablation of polycrystalline graphite by a nanosecond laser pulse

    NASA Astrophysics Data System (ADS)

    Hoffman, Jacek

    2015-06-01

    Our experiments with the ablation of graphite by a nanosecond laser pulse showed the formation of craters with a depth of upto 60 m. The creation of such deep craters is hard to explain solely by evaporation. Existing models should be supplemented by an additional mass removal process that ensures penetration of the material. The recoil pressure at the surface of the target generates a compression wave propagating deep into the material. Possible mechanisms of fracture by the longitudinal compression wave are discussed. A phenomenological model of material fragmentation is proposed. Modelling results are in good agreement with the experiment. The model may be used for polycrystalline graphite as well as other brittle materials treated by the nanosecond laser pulse.

  1. Maximum gravitational recoil.

    PubMed

    Campanelli, Manuela; Lousto, Carlos O; Zlochower, Yosef; Merritt, David

    2007-06-01

    Recent calculations of gravitational radiation recoil generated during black-hole binary mergers have reopened the possibility that a merged binary can be ejected even from the nucleus of a massive host galaxy. Here we report the first systematic study of gravitational recoil of equal-mass binaries with equal, but counteraligned, spins parallel to the orbital plane. Such an orientation of the spins is expected to maximize the recoil. We find that recoil velocity (which is perpendicular to the orbital plane) varies sinusoidally with the angle that the initial spin directions make with the initial linear momenta of each hole and scales up to a maximum of approximately 4000 km s-1 for maximally rotating holes. Our results show that the amplitude of the recoil velocity can depend sensitively on spin orientations of the black holes prior to merger. PMID:17677894

  2. Photon Recoil Momentum in Dispersive Media

    SciTech Connect

    Campbell, Gretchen K.; Leanhardt, Aaron E.; Mun, Jongchul; Boyd, Micah; Streed, Erik W.; Ketterle, Wolfgang; Pritchard, David E.

    2005-05-06

    A systematic shift of the photon recoil momentum due to the index of refraction of a dilute gas of atoms has been observed. The recoil frequency was determined with a two-pulse light grating interferometer using near-resonant laser light. The results show that the recoil momentum of atoms caused by the absorption of a photon is n({Dirac_h}/2{pi})k, where n is the index of refraction of the gas and k is the vacuum wave vector of the photon. This systematic effect must be accounted for in high-precision atom interferometry with light gratings.

  3. Gaussian effective potential: Quantum mechanics

    NASA Astrophysics Data System (ADS)

    Stevenson, P. M.

    1984-10-01

    We advertise the virtues of the Gaussian effective potential (GEP) as a guide to the behavior of quantum field theories. Much superior to the usual one-loop effective potential, the GEP is a natural extension of intuitive notions familiar from quantum mechanics. A variety of quantum-mechanical examples are studied here, with an eye to field-theoretic analogies. Quantum restoration of symmetry, dynamical mass generation, and "quantum-mechanical resuscitation" are among the phenomena discussed. We suggest how the GEP could become the basis of a systematic approximation procedure. A companion paper will deal with scalar field theory.

  4. Quantum Effects in Biological Systems

    NASA Astrophysics Data System (ADS)

    Roy, Sisir

    2014-07-01

    The debates about the trivial and non-trivial effects in biological systems have drawn much attention during the last decade or so. What might these non-trivial sorts of quantum effects be? There is no consensus so far among the physicists and biologists regarding the meaning of "non-trivial quantum effects". However, there is no doubt about the implications of the challenging research into quantum effects relevant to biology such as coherent excitations of biomolecules and photosynthesis, quantum tunneling of protons, van der Waals forces, ultrafast dynamics through conical intersections, and phonon-assisted electron tunneling as the basis for our sense of smell, environment assisted transport of ions and entanglement in ion channels, role of quantum vacuum in consciousness. Several authors have discussed the non-trivial quantum effects and classified them into four broad categories: (a) Quantum life principle; (b) Quantum computing in the brain; (c) Quantum computing in genetics; and (d) Quantum consciousness. First, I will review the above developments. I will then discuss in detail the ion transport in the ion channel and the relevance of quantum theory in brain function. The ion transport in the ion channel plays a key role in information processing by the brain.

  5. Transport of Radioactive Material by Alpha Recoil

    SciTech Connect

    Icenhour, A.S.

    2005-05-19

    The movement of high-specific-activity radioactive particles (i.e., alpha recoil) has been observed and studied since the early 1900s. These studies have been motivated by concerns about containment of radioactivity and the protection of human health. Additionally, studies have investigated the potential advantage of alpha recoil to effect separations of various isotopes. This report provides a review of the observations and results of a number of the studies.

  6. The HERMES recoil detector

    NASA Astrophysics Data System (ADS)

    Airapetian, A.; Aschenauer, E. C.; Belostotski, S.; Borisenko, A.; Bowles, J.; Brodski, I.; Bryzgalov, V.; Burns, J.; Capitani, G. P.; Carassiti, V.; Ciullo, G.; Clarkson, A.; Contalbrigo, M.; De Leo, R.; De Sanctis, E.; Diefenthaler, M.; Di Nezza, P.; Dren, M.; Ehrenfried, M.; Guler, H.; Gregor, I. M.; Hartig, M.; Hill, G.; Hoek, M.; Holler, Y.; Hristova, I.; Jo, H. S.; Kaiser, R.; Keri, T.; Kisselev, A.; Krause, B.; Krauss, B.; Lagamba, L.; Lehmann, I.; Lenisa, P.; Lu, S.; Lu, X.-G.; Lumsden, S.; Mahon, D.; Martinez de la Ossa, A.; Murray, M.; Mussgiller, A.; Nowak, W.-D.; Naryshkin, Y.; Osborne, A.; Pappalardo, L. L.; Perez-Benito, R.; Petrov, A.; Pickert, N.; Prahl, V.; Protopopescu, D.; Reinecke, M.; Riedl, C.; Rith, K.; Rosner, G.; Rubacek, L.; Ryckbosch, D.; Salomatin, Y.; Schnell, G.; Seitz, B.; Shearer, C.; Shutov, V.; Statera, M.; Steijger, J. J. M.; Stenzel, H.; Stewart, J.; Stinzing, F.; Trzcinski, A.; Tytgat, M.; Vandenbroucke, A.; Van Haarlem, Y.; Van Hulse, C.; Varanda, M.; Veretennikov, D.; Vilardi, I.; Vikhrov, V.; Vogel, C.; Yaschenko, S.; Ye, Z.; Yu, W.; Zeiler, D.; Zihlmann, B.

    2013-05-01

    For the final running period of HERA, a recoil detector was installed at the HERMES experiment to improve measurements of hard exclusive processes in charged-lepton nucleon scattering. Here, deeply virtual Compton scattering is of particular interest as this process provides constraints on generalised parton distributions that give access to the total angular momenta of quarks within the nucleon. The HERMES recoil detector was designed to improve the selection of exclusive events by a direct measurement of the four-momentum of the recoiling particle. It consisted of three components: two layers of double-sided silicon strip sensors inside the HERA beam vacuum, a two-barrel scintillating fibre tracker, and a photon detector. All sub-detectors were located inside a solenoidal magnetic field with a field strength of 1T. The recoil detector was installed in late 2005. After the commissioning of all components was finished in September 2006, it operated stably until the end of data taking at HERA end of June 2007. The present paper gives a brief overview of the physics processes of interest and the general detector design. The recoil detector components, their calibration, the momentum reconstruction of charged particles, and the event selection are described in detail. The paper closes with a summary of the performance of the detection system.

  7. High acceptance recoil polarimeter

    SciTech Connect

    The HARP Collaboration

    1992-12-05

    In order to detect neutrons and protons in the 50 to 600 MeV energy range and measure their polarization, an efficient, low-noise, self-calibrating device is being designed. This detector, known as the High Acceptance Recoil Polarimeter (HARP), is based on the recoil principle of proton detection from np[r arrow]n[prime]p[prime] or pp[r arrow]p[prime]p[prime] scattering (detected particles are underlined) which intrinsically yields polarization information on the incoming particle. HARP will be commissioned to carry out experiments in 1994.

  8. Effective equations for the quantum pendulum from momentous quantum mechanics

    SciTech Connect

    Hernandez, Hector H.; Chacon-Acosta, Guillermo

    2012-08-24

    In this work we study the quantum pendulum within the framework of momentous quantum mechanics. This description replaces the Schroedinger equation for the quantum evolution of the system with an infinite set of classical equations for expectation values of configuration variables, and quantum dispersions. We solve numerically the effective equations up to the second order, and describe its evolution.

  9. Spin-orbit coupling and quantum spin Hall effect for neutral atoms without spin flips.

    PubMed

    Kennedy, Colin J; Siviloglou, Georgios A; Miyake, Hirokazu; Burton, William Cody; Ketterle, Wolfgang

    2013-11-27

    We propose a scheme which realizes spin-orbit coupling and the quantum spin Hall effect for neutral atoms in optical lattices without relying on near resonant laser light to couple different spin states. The spin-orbit coupling is created by modifying the motion of atoms in a spin-dependent way by laser recoil. The spin selectivity is provided by Zeeman shifts created with a magnetic field gradient. Alternatively, a quantum spin Hall Hamiltonian can be created by all-optical means using a period-tripling, spin-dependent superlattice. PMID:24329453

  10. Quantum effects in biological systems

    NASA Astrophysics Data System (ADS)

    Sarovar, Mohan

    2010-02-01

    Identification of non-trivial quantum mechanical effects in the functioning of biological systems has been a long-standing and elusive goal in the fields of physics, chemistry and biology. Recent progress in control and measurement technologies, especially in the optical spectroscopy domain, have made possible the identification of such effects. In particular, electronic coherence was recently shown to survive for relatively long times in photosynthetic light harvesting complexes despite the effects of noisy biomolecular environments. Motivated by this experimental discovery, several recent studies have combined techniques from quantum information, quantum dynamical theory and chemical physics to characterize the extent and nature of quantum dynamics in light harvesting structures. I will review these results and summarize our understanding of the subtle quantum effects in photosynthetic complexes. Then I will outline the remarkable properties of light harvesting complexes that allow quantum effects to be significant at dynamically relevant timescales, despite the decohering biomolecular environment. Finally, I will conclude by discussing the implications of quantum effects in light harvesting complexes, and in biological systems in general.

  11. Photoelectron Spectroscopy of LiV2O4 with Photons from 8.4 to 8100 eV: Bulk Sensitivity, Hybridization, and Recoil Effects

    NASA Astrophysics Data System (ADS)

    Suga, Shigemasa; Sekiyama, Akira; Fujiwara, Hidenori; Nakatsu, Yasutaka; Yamaguchi, Jun-ichi; Kimura, Masato; Murakami, Keita; Niitaka, Seiji; Takagi, Hidenori; Yabashi, Makina; Tamasaku, Kenji; Higashiya, Atsushi; Ishikawa, Tetsuya; Nekrasov, Igor

    2010-04-01

    Hard- and soft-X-ray photoelectron spectroscopies (HAXPES and SXPES) are very powerful for studying the bulk electronic structures of strongly correlated electron systems. The presence of an intrinsic surface layer on clean fractured surfaces is demonstrated for LiV2O4. In this material, single-nucleus recoil effects are very prominent not only for all core levels but also for valence states at 20 K. However, such recoil effects are negligible in VO2 even at 350 K in spite of the fact that VO2 has a similar V-O6 octahedron structure. The marked intensity increase in the high-binding-energy part of the so-called O 2p band relative to the V 3d band in HAXPES is interpreted to be due to the V 4s state contribution. Very high resolution extremely low energy photoelectron spectroscopy (ELEPES) is performed with Kr and Xe lamps at 10.1 and 8.4 eV, respectively, demonstrating its bulk sensitivity for this material with heavy-Fermion-like behavior.

  12. The effect of quantum memory on quantum games

    NASA Astrophysics Data System (ADS)

    Ramzan, M.; Nawaz, Ahmad; Toor, A. H.; Khan, M. K.

    2008-02-01

    We study quantum games with correlated noise through a generalized quantization scheme. We investigate the effects of memory on quantum games, such as Prisoner's Dilemma, Battle of the Sexes and Chicken, through three prototype quantum-correlated channels. It is shown that the quantum player enjoys an advantage over the classical player for all nine cases considered in this paper for the maximally entangled case. However, the quantum player can also outperform the classical player for subsequent cases that can be noted in the case of the Battle of the Sexes game. It can be seen that the Nash equilibria do not change for all the three games under the effect of memory.

  13. Effect of the recoil pressure induced by evaporation on motion of powder particles in the light field during laser cladding

    NASA Astrophysics Data System (ADS)

    Kovaleva, I. O.; Kovalev, O. B.

    2012-01-01

    A model is proposed, which takes into account acceleration of powder particles by a force induced by recoil of material vapors from the irradiated region of the particle surface. Results of a numerical analysis of heat and mass transfer in the case of motion of individual stainless steel powder particles in a gas flow and in a light field of laser radiation under conditions of laser cladding are presented. Acceleration of particles is found to depend on their diameter, carrier gas velocity, powder material properties, laser radiation power, and degree of attenuation of the power density in the laser beam in the direction of its action on the substrate. The calculated results are compared with experimental data on light-propulsion acceleration of individual particles (of aluminum, aluminum oxide, and graphite) under the action of pulsed laser radiation.

  14. Interpreting Recoil for Undergraduate Students

    ERIC Educational Resources Information Center

    Elsayed, Tarek A.

    2012-01-01

    The phenomenon of recoil is usually explained to students in the context of Newton's third law. Typically, when a projectile is fired, the recoil of the launch mechanism is interpreted as a reaction to the ejection of the smaller projectile. The same phenomenon is also interpreted in the context of the conservation of linear momentum, which is

  15. Interpreting Recoil for Undergraduate Students

    ERIC Educational Resources Information Center

    Elsayed, Tarek A.

    2012-01-01

    The phenomenon of recoil is usually explained to students in the context of Newton's third law. Typically, when a projectile is fired, the recoil of the launch mechanism is interpreted as a reaction to the ejection of the smaller projectile. The same phenomenon is also interpreted in the context of the conservation of linear momentum, which is…

  16. Comparison of quantum confinement effects between quantum wires and dots

    SciTech Connect

    Li, Jingbo; Wang, Lin-Wang

    2004-03-30

    Dimensionality is an important factor to govern the electronic structures of semiconductor nanocrystals. The quantum confinement energies in one-dimensional quantum wires and zero-dimensional quantum dots are quite different. Using large-scale first-principles calculations, we systematically study the electronic structures of semiconductor (including group IV, III-V, and II-VI) surface-passivated quantum wires and dots. The band-gap energies of quantum wires and dots have the same scaling with diameter for a given material. The ratio of band-gap-increases between quantum wires and dots is material-dependent, and slightly deviates from 0.586 predicted by effective-mass approximation. Highly linear polarization of photoluminescence in quantum wires is found. The degree of polarization decreases with the increasing temperature and size.

  17. Interface effect in coupled quantum wells

    SciTech Connect

    Hao, Ya-Fei

    2014-06-28

    This paper intends to theoretically investigate the effect of the interfaces on the Rashba spin splitting of two coupled quantum wells. The results show that the interface related Rashba spin splitting of the two coupled quantum wells is both smaller than that of a step quantum well which has the same structure with the step quantum well in the coupled quantum wells. And the influence of the cubic Dresselhaus spin-orbit interaction of the coupled quantum wells is larger than that of a step quantum well. It demonstrates that the spin relaxation time of the two coupled quantum wells will be shorter than that of a step quantum well. As for the application in the spintronic devices, a step quantum well may be better than the coupled quantum wells, which is mentioned in this paper.

  18. Interpreting Recoil for Undergraduate Students

    NASA Astrophysics Data System (ADS)

    Elsayed, Tarek A.

    2012-04-01

    The phenomenon of recoil is usually explained to students in the context of Newton's third law. Typically, when a projectile is fired, the recoil of the launch mechanism is interpreted as a reaction to the ejection of the smaller projectile. The same phenomenon is also interpreted in the context of the conservation of linear momentum, which is closely related to Newton's third law. Since the actual microscopic causes of recoil differ from one problem to another, some students (and teachers) may not be satisfied with understanding recoil through the principles of conservation of linear momentum and Newton's third law. For these students, the origin of the recoil motion should be presented in more depth.

  19. Velocity Selective Raman Resonances at High Recoil

    NASA Astrophysics Data System (ADS)

    Kritsun, O.; Affolderbach, C.; Metcalf, H.

    2001-05-01

    We are continuing our exploration of the unusual domain of laser cooling where the ratio of the recoil frequency ?r to the natural width ? no longer satisfies ?_r/? ? \\varepsilon << 1. Among the unusual properties is that VSCPT can be performed in a two-level atom(J. Hack et. al., Phys. Rev., A62), 013405 (2000).. We use the 2 ^3Sarrow3 ^3P transition of metastable He at ? = 389 nm, where \\varepsilon ? 1/5 and the recoil velocity is >25 cm/s, comparable to the Doppler limit. Thus sub-recoil resolution is readily achieved in a modest atomic beam apparatus. We have observed the magnetic field and laser detuning dependence of the usual three-level VSCPT(A. Aspect et al., Phys. Rev. Lett., 61) 826 (1988). on the J = 1 arrow 1 transition, and velocity selective resonances on the J = 1 arrow 2 transition in magnetic fields. We have developed a simple quantum mechanical model of these phenomena as well as an appealing semi-classical model.

  20. Wave kinetics of relativistic quantum plasmas

    SciTech Connect

    Mendonca, J. T.

    2011-06-15

    A quantum kinetic equation, valid for relativistic unmagnetized plasmas, is derived here. This equation describes the evolution of a quantum quasi-distribution, which is the Wigner function for relativistic spinless charged particles in a plasma, and it is exactly equivalent to a Klein-Gordon equation. Our quantum kinetic equation reduces to the Vlasov equation in the classical limit, where the Wigner function is replaced by a classical distribution function. An approximate form of the quantum kinetic equation is also derived, which includes first order quantum corrections. This is applied to electron plasma waves, for which a new dispersion relation is obtained. It is shown that quantum recoil effects contribute to the electron Landau damping with a third order derivative term. The case of high frequency electromagnetic waves is also considered. Its dispersion relation is shown to be insensitive to quantum recoil effects for equilibrium plasma distributions.

  1. Quantum discord in the dynamical Casimir effect

    NASA Astrophysics Data System (ADS)

    Sabn, Carlos; Fuentes, Ivette; Johansson, Gran

    2015-07-01

    We analyze the generation of quantum discord by means of the dynamical Casimir effect in superconducting wave guides modulated by superconducting quantum interferometric devices. We show that for realistic experimental parameters, the conditions for the existence of quantum discord are less demanding than the previously considered for quantum entanglement or nonclassicality. These results could facilitate the experimental confirmation of the quantum nature of the dynamical Casimir effect radiation. Moreover, the states with nonzero discord and zero entanglement generated by the dynamical Casimir effect are a useful resource for quantum cryptography.

  2. Quantum mechanical effects from deformation theory

    SciTech Connect

    Much, A.

    2014-02-15

    We consider deformations of quantum mechanical operators by using the novel construction tool of warped convolutions. The deformation enables us to obtain several quantum mechanical effects where electromagnetic and gravitomagnetic fields play a role. Furthermore, a quantum plane can be defined by using the deformation techniques. This in turn gives an experimentally verifiable effect.

  3. Nuclear Quantum Effects in Water

    NASA Astrophysics Data System (ADS)

    Morrone, Joseph A.; Car, Roberto

    2008-07-01

    A path-integral Car-Parrinello molecular dynamics simulation of liquid water and ice is performed. It is found that the inclusion of nuclear quantum effects systematically improves the agreement of first-principles simulations of liquid water with experiment. In addition, the proton momentum distribution is computed utilizing a recently developed open path-integral molecular dynamics methodology. It is shown that these results are in good agreement with experimental data.

  4. Hyperbolic supersymmetric quantum Hall effect

    SciTech Connect

    Hasebe, Kazuki

    2008-12-15

    Developing a noncompact version of the supersymmetric Hopf map, we formulate the quantum Hall effect on a superhyperboloid. Based on OSp(1|2) group theoretical methods, we first analyze the one-particle Landau problem, and successively explore the many-body problem where the Laughlin wave function, hard-core pseudopotential Hamiltonian, and topological excitations are derived. It is also shown that the fuzzy superhyperboloid emerges at the lowest Landau level.

  5. Difference between a photon's momentum and an atom's recoil.

    PubMed

    Gibble, Kurt

    2006-08-18

    When an atom absorbs a photon from a laser beam that is not an infinite plane wave, the atom's recoil is less than variant Planck's k in the propagation direction. We show that the recoils in the transverse directions produce a lensing of the atomic wave functions, which leads to a frequency shift that is not discrete but varies linearly with the field amplitude and strongly depends on the atomic state detection. The same lensing effect is also important for microwave atomic clocks. The frequency shifts are of the order of the naive recoil shift for the transverse wave vector of the photons. PMID:17026225

  6. Difference between a Photon's Momentum and an Atom's Recoil

    SciTech Connect

    Gibble, Kurt

    2006-08-18

    When an atom absorbs a photon from a laser beam that is not an infinite plane wave, the atom's recoil is less than ({Dirac_h}/2{pi})k in the propagation direction. We show that the recoils in the transverse directions produce a lensing of the atomic wave functions, which leads to a frequency shift that is not discrete but varies linearly with the field amplitude and strongly depends on the atomic state detection. The same lensing effect is also important for microwave atomic clocks. The frequency shifts are of the order of the naive recoil shift for the transverse wave vector of the photons.

  7. NMR investigation of the quantum pigeonhole effect

    NASA Astrophysics Data System (ADS)

    V. S., Anjusha; Hegde, Swathi S.; Mahesh, T. S.

    2016-02-01

    NMR quantum simulators have been used for studying various quantum phenomena. Here, using a four-qubit NMR quantum simulator, we investigate the recently postulated quantum pigeonhole effect. In this phenomenon, a set of three particles in a two-path interferometer often appears to be in such a superposition that no two particles can be assigned a single path, thus exhibiting the nonclassical behavior. In our experiments, quantum pigeons are emulated by three nuclear qubits whose states are probed jointly and noninvasively by an ancillary spin. The experimental results are in good agreement with quantum theoretical predictions.

  8. Protection of Quantum Correlation Through the Quantum Erasing Effect

    NASA Astrophysics Data System (ADS)

    Xu, Hui-Yun; Yang, Guo-Hui

    2015-12-01

    By taking into account the quantum erasing effect(QEE), the quantum discord (QD) behavior of a two-qubit system with different initial states are investigated in detail. We find that the quantum correlation can be saved under a scheme of two spatially separated atoms, each located in a leaky cavity through the quantum erasing method. It is shown that QEE can weaken the effects of decoherence, and preserve the maximum information of the coherent item. No matter whether the two atoms are in the mixted or pure state, one can robusty save their initial quantum correlation even the number of erasing events is finite. If one limit the erasing events N → ∞, the QEE can be used to protect the initial quantum correlation independently of the state in which it is stored, the values of QD is always nearly equal to the initial QD values, and it is nearly independent of the decoherence, which imply us more encourage strategy for protecting the quantum correlation properties in some quantum systems.

  9. Quantum communication complexity using the quantum Zeno effect

    NASA Astrophysics Data System (ADS)

    Tavakoli, Armin; Anwer, Hammad; Hameedi, Alley; Bourennane, Mohamed

    2015-07-01

    The quantum Zeno effect (QZE) is the phenomenon in which the unitary evolution of a quantum state is suppressed, e.g., due to frequent measurements. Here, we investigate the use of the QZE in a class of communication complexity problems (CCPs). Quantum entanglement is known to solve certain CCPs beyond classical constraints. However, recent developments have yielded CCPs for which superclassical results can be obtained using only communication of a single d -level quantum state (qudit) as a resource. In the class of CCPs considered here, we show quantum reduction of complexity in three ways: using (i) entanglement and the QZE, (ii) a single qudit and the QZE, and (iii) a single qudit. We have performed a proof of concept experimental demonstrations of three party CCP protocol based on single-qubit communication with and without QZE.

  10. Recoil Based Fuel Breeding Fuel Structure

    SciTech Connect

    Popa-Simil, Liviu

    2008-07-01

    Nuclear transmutation reactions are based on the absorption of a smaller particle as neutron, proton, deuteron, alpha, etc. The resulting compound nucleus gets out of its initial lattice mainly by taking the recoil, also with help from its sudden change in chemical properties. The recoil implantation is used in correlation with thin and ultra thin materials mainly for producing radiopharmaceuticals and ultra-thin layer radioactive tracers. In nuclear reactors, the use of nano-particulate pellets could facilitate the recoil implantation for breeding, transmutation and partitioning purposes. Using enriched {sup 238}U or {sup 232}Th leads to {sup 239}Pu and {sup 233}U production while using other actinides as {sup 240}Pu, {sup 241}Am etc. leads to actinide burning. When such a lattice is immersed into a radiation resistant fluid (water, methanol, etc.), the recoiled product is transferred into the flowing fluid and removed from the hot area using a concentrator/purifier, preventing the occurrence of secondary transmutation reactions. The simulation of nuclear collision and energy transfer shows that the impacted nucleus recoils in the interstitial space creating a defect or lives small lattices. The defect diffuses, and if no recombination occurs it stops at the lattices boundaries. The nano-grains are coated in thin layer to get a hydrophilic shell to be washed by the collection liquid the particle is immersed in. The efficiency of collection depends on particle magnitude and nuclear reaction channel parameters. For {sup 239}Pu the direct recoil extraction rate is about 70% for {sup 238}UO{sub 2} grains of 5 nm diameters and is brought up to 95% by diffusion due to {sup 239}Neptunium incompatibility with Uranium dioxide lattice. Particles of 5 nm are hard to produce so a structure using particles of 100 nm have been tested. The particles were obtained by plasma sputtering in oxygen atmosphere. A novel effect as nano-cluster radiation damage robustness and cluster amplified defects rejection will be discussed. The advantage of the method and device is its ability of producing small amount of isotopic materials easy to separate, using the nuclear reactors, with higher yield than the accelerator based methods and requiring less chemistry. (author)

  11. Quantum Zeno Effect in the Measurement Problem

    NASA Technical Reports Server (NTRS)

    Namiki, Mikio; Pasaczio, Saverio

    1996-01-01

    Critically analyzing the so-called quantum Zeno effect in the measurement problem, we show that observation of this effect does not necessarily mean experimental evidence for the naive notion of wave-function collapse by measurement (the simple projection rule). We also examine what kind of limitation the uncertainty relation and others impose on the observation of the quantum Zeno effect.

  12. Quantum Anomalous Hall Effect in Magnetic Semiconductors

    NASA Astrophysics Data System (ADS)

    Liu, Chaoxing

    2015-03-01

    In the quantum anomalous Hall effect, dissipationless charge currents are carried by chiral edge states and the Hall conductance is quantized, similar to the quantum Hall effect. Different from the conventional quantum Hall effect that requires strong magnetic fields, the quantum anomalous Hall effect is induced by strong exchange coupling between electron spin and magnetic moments in magnetic materials, so it can be realized at zero magnetic field, enabling the potential application of electronic devices with low energy consumption. Recent experiments on Cr or V doped BiSbTe thin films has observed the quantized Hall conductance at zero magnetic field and confirmed this novel effect. In this talk, I would like to discuss our recent work on the quantum anomalous Hall effect in magnetic semiconductors. I will first introduce two key ingredients, inverted band structures and ferromagnetic insulators, for the quantum anomalous Hall effect in realistic magnetic materials. Then, based on these two ingredients, I will discuss different classes of materials for the quantum anomalous Hall effect, focusing on magnetically doped InAs/GaSb quantum wells and magnetically doped LaOSbSe2 films. For magnetically doped InAs/GaSb quantum wells, we will show how band edge singularity can enhance spin susceptibility and lead to the quantum anomalous Hall state at a relatively high critical temperature. For magnetically doped LaOSbSe2 films, we find the quantum anomalous Hall effect can be tuned electrically by a gate voltage and identify layer dependent spin texture as the underlying physical reason. Finally, we will also discuss disordered transport and anisotropic magnetoresistance in the quantum anomalous Hall regime.

  13. α -decay chains of recoiled superheavy nuclei: A theoretical study

    NASA Astrophysics Data System (ADS)

    Niyti, Sawhney, Gudveen; Sharma, Manoj K.; Gupta, Raj K.

    2015-05-01

    A systematic theoretical study of α -decay half-lives in the superheavy mass region of the periodic table of elements is carried out by extending the quantum-mechanical fragmentation theory based on the preformed cluster model (PCM) to include temperature (T ) dependence in its built-in preformation and penetration probabilities of decay fragments. Earlier, the α -decay chains of the isotopes of Z =115 were investigated by using the standard PCM for spontaneous decays, with"hot-optimum" orientation effects included, which required a constant scaling factor of 104 to approach the available experimental data. In the present approach of the PCM (T ≠0 ), the temperature effects are included via the recoil energy of the residual superheavy nucleus (SHN) left after x -neutron emission from the superheavy compound nucleus. The important result is that the α -decay half-lives calculated by the PCM (T ≠0 ) match the experimental data nearly exactly, without using any scaling factor of the type used in the PCM. Note that the PCM (T ≠0 ) is an equivalent of the dynamical cluster-decay model for heavy-ion collisions at angular momentum ℓ =0 . The only parameter of model is the neck-length parameter Δ R , which for the calculated half-lives of α -decay chains of various isotopes of Z =113 to 118 nuclei formed in "hot-fusion" reactions is found to be nearly constant, i.e., Δ R ≈0.95 ±0.05 fm for all the α -decay chains studied. The use of recoiled residue nucleus as a secondary heavy-ion beam for nuclear reactions has also been suggested in the past.

  14. RECOILING SUPERMASSIVE BLACK HOLES IN SPIN-FLIP RADIO GALAXIES

    SciTech Connect

    Liu, F. K.; Wang Dong; Chen Xian

    2012-02-20

    Numerical relativity simulations predict that coalescence of supermassive black hole (SMBH) binaries leads not only to a spin flip but also to a recoiling of the merger remnant SMBHs. In the literature, X-shaped radio sources are popularly suggested to be candidates for SMBH mergers with spin flip of jet-ejecting SMBHs. Here we investigate the spectral and spatial observational signatures of the recoiling SMBHs in radio sources undergoing black hole spin flip. Our results show that SMBHs in most spin-flip radio sources have mass ratio q {approx}> 0.3 with a minimum possible value q{sub min} {approx_equal} 0.05. For major mergers, the remnant SMBHs can get a kick velocity as high as 2100 km s{sup -1} in the direction within an angle {approx}< 40 Degree-Sign relative to the spin axes of remnant SMBHs, implying that recoiling quasars are biased to be with high Doppler-shifted broad emission lines while recoiling radio galaxies are biased to large apparent spatial off-center displacements. We also calculate the distribution functions of line-of-sight velocity and apparent spatial off-center displacements for spin-flip radio sources with different apparent jet reorientation angles. Our results show that the larger the apparent jet reorientation angle is, the larger the Doppler-shifting recoiling velocity and apparent spatial off-center displacement will be. We investigate the effects of recoiling velocity on the dust torus in spin-flip radio sources and suggest that recoiling of SMBHs would lead to 'dust-poor' active galactic nuclei. Finally, we collect a sample of 19 X-shaped radio objects and for each object give the probability of detecting the predicted signatures of recoiling SMBH.

  15. The recoiling of liquid droplets upon collision with solid surfaces

    NASA Astrophysics Data System (ADS)

    Kim, H.-Y.; Chun, J.-H.

    2001-03-01

    Although the spreading behavior of liquid droplets impacting on solid surfaces has been extensively studied, the mechanism of recoiling which takes place after the droplet reaches its maximum spread diameter has not yet been fully understood. This paper reports the study of the recoiling behavior of different liquid droplets (water, ink, and silicone oil) on different solid surfaces (polycarbonate and silicon oxide). The droplet dynamics are experimentally studied using a high speed video system. Analytical methods using the variational principle, which were originated by Kendall and Rohsenow (MIT Technical Report 85694-100, 1978) and Bechtel et al. [IBM J. Res. Dev. 25, 963 (1981)], are modified to account for wetting and viscous effects. In our model, an empirically determined dissipation factor is used to estimate the viscous friction. It is shown that the model closely predicts the experimental results obtained for the varying dynamic impact conditions and wetting characteristics. This study shows that droplets recoil fast and vigorously when the Ohnesorge number decreases or the Weber number increases. Droplets with a large equilibrium contact angle are also found to recoil faster. Here the Ohnesorge number scales the resisting force to the recoiling motion, and is shown to play the most important role in characterizing the recoiling motion.

  16. Nonlinear effects in quantum dissipation

    NASA Astrophysics Data System (ADS)

    Vitali, David; Grigolini, Paolo

    1990-12-01

    We study a two-level system linearly interacting with a set of quantum-mechanical oscillators, referred to as the ``bath.'' This system is formally equivalent to a magnetic dipole, with spin 1/2, precessing with the Larmor frequency ?0 around a fixed magnetic field along the z axis and undergoing the influence of a fluctuating field along the x axis. These bath fluctuations are not independent of the state of the spin, and the crucial problem to be studied in this paper is precisely how to take the reaction field, i.e., the influence of the bath on the system, into account. We find a general result based on neglecting a contribution to the reaction field proportional to ?x(t)-, where the angle brackets denote averaging on both the spin and the bath space, with a density matrix corresponding to the spin polarized along the x axis. We show that under the special condition that the spin does not significantly depart from its initial state, our general result turns out to coincide with the noninteracting-blip approximation (NBA) of Leggett and co-workers [Rev. Mod. Phys. 59, 1 (1987)]. When we make the assumption that both quantum and thermal fluctuations of the bath can be neglected and that the time scale of the bath is virtually zero (adiabatic assumption), our general result turns out to coincide with the prediction of the discrete nonlinear Schrdinger equation (DNSE) of Davydov and Kislukha [Phys. Status Solidi B 59, 465 (1973)] and Davydov $[-Biology and Quantum Mechanics (Pergamon, Oxford, 1982)] in the two-sites case. This means that the nonlinear effects proven by Kenkre and co-workers [Phys. Rev. B 34, 4959 (1986); 35, 1473 (1987)] to accompany a significant departure of the spin from the initial state are lost by the NBA. On the other hand, our approach provides a rigorous evaluation of the effects of the oscillator fluctuations on the predictions of the DNSE. It is shown that the quantum fluctuations might have a significant role also in the region of high temperature to which the nonadiabatic corrections of Kenkre and co-workers apply. Finally, it is shown that a still more accurate approximation would be that of neglecting a reaction field proportional to ?x(t)-s, where s denotes an average carried out only on the spin space. This approximation leads our approach to coincide with the exact result in the special case where both the spin and its bath are replaced by their classical counterparts. Under this approximation, the detrapping would be equivalent to an Arrhenius-like thermal-activation process. When the coupling strength between the system and its bath is decreased, the spin is expected to depart from the initial trapped state. The dynamics of this process is expected to be influenced by the joint action of the bath fluctuations (both thermal and quantum mechanical) and of the nonlinearity stemming from the reaction field, and ignored by the NBA. This intriguing problem should be the subject of further investigations.

  17. Quantum effects in the understanding of consciousness.

    PubMed

    Hameroff, Stuart R; Craddock, Travis J A; Tuszynski, Jack A

    2014-06-01

    This paper presents a historical perspective on the development and application of quantum physics methodology beyond physics, especially in biology and in the area of consciousness studies. Quantum physics provides a conceptual framework for the structural aspects of biological systems and processes via quantum chemistry. In recent years individual biological phenomena such as photosynthesis and bird navigation have been experimentally and theoretically analyzed using quantum methods building conceptual foundations for quantum biology. Since consciousness is attributed to human (and possibly animal) mind, quantum underpinnings of cognitive processes are a logical extension. Several proposals, especially the Orch OR hypothesis, have been put forth in an effort to introduce a scientific basis to the theory of consciousness. At the center of these approaches are microtubules as the substrate on which conscious processes in terms of quantum coherence and entanglement can be built. Additionally, Quantum Metabolism, quantum processes in ion channels and quantum effects in sensory stimulation are discussed in this connection. We discuss the challenges and merits related to quantum consciousness approaches as well as their potential extensions. PMID:25012711

  18. Quantum Zeno effect in parameter estimation

    NASA Astrophysics Data System (ADS)

    Kiilerich, Alexander Holm; Mlmer, Klaus

    2015-09-01

    The quantum Zeno effect freezes the evolution of a quantum system subject to frequent measurements. We apply a Fisher information analysis to show that because of this effect, a closed quantum system should be probed as rarely as possible, while a dissipative quantum system should be probed at specifically determined intervals to yield the optimal estimation of parameters governing the system dynamics. With a Bayesian analysis we show that a few frequent measurements are needed to identify the parameter region within which the Fisher information analysis applies.

  19. The quantum Hall effect helicity

    SciTech Connect

    Shrivastava, Keshav N.

    2015-04-16

    The quantum Hall effect in semiconductor heterostructures is explained by two signs in the angular momentum j=l±s and g=(2j+1)/(2l+1) along with the Landau factor (n+1/2). These modifications in the existing theories explain all of the fractional charges. The helicity which is the sign of the product of the linear momentum with the spin p.s plays an important role for the understanding of the data at high magnetic fields. In particular it is found that particles with positive sign in the spin move in one direction and those with negative sign move in another direction which explains the up and down stream motion of the particles.

  20. Electron emission and recoil effects following the beta decay of He6

    NASA Astrophysics Data System (ADS)

    Schulhoff, Eva E.; Drake, G. W. F.

    2015-11-01

    Probabilities for atomic electron excitation (shake-up) and ionization (shake-off) are studied following the beta-decay process →Li+6He6+e-+ν¯e , and in particular, recoil-induced contributions to the shake-off probability are calculated within the nonrelativistic sudden approximation. A pseudostate expansion method together with Stieltjes imaging is used to represent the complete two-electron spectrum of final Li+6 ,Li26+, and Li36+ states. Results for the recoil correction show a 7 σ disagreement with the experiment of Carlson et al. [Phys. Rev. 129, 2220 (1963), 10.1103/PhysRev.129.2220]. A variety of sum rules, including a newly derived Thomas-Reich-Kuhn oscillator strength sum rule for dipole recoil terms, provides tight constraints on the accuracy of the results. Calculations are performed for the helium 1 s 2 s 3S metastable state, as well as for the 1 s21S ground state. Our results would reduce the recoil-induced correction to the measured electroneutrino coupling constant ae μ from the apparent 0.6% used in the experiments to 0.09%.

  1. Maxwell-Garnett effective medium theory: Quantum nonlocal effects

    SciTech Connect

    Moradi, Afshin

    2015-04-15

    We develop the Maxwell-Garnett theory for the effective medium approximation of composite materials with metallic nanoparticles by taking into account the quantum spatial dispersion effects in dielectric response of nanoparticles. We derive a quantum nonlocal generalization of the standard Maxwell-Garnett formula, by means the linearized quantum hydrodynamic theory in conjunction with the Poisson equation as well as the appropriate additional quantum boundary conditions.

  2. Operator Quantum Zeno Effect: Protecting Quantum Information with Noisy Two-Qubit Interactions

    NASA Astrophysics Data System (ADS)

    Wang, Shu-Chao; Li, Ying; Wang, Xiang-Bin; Kwek, Leong Chuan

    2013-03-01

    The time evolution of some quantum states can be slowed down or even stopped under frequent measurements. This is the usual quantum Zeno effect. Here, we report an operator quantum Zeno effect, in which the evolution of some physical observables is slowed down through measurements even though the quantum state changes randomly with time. Based on the operator quantum Zeno effect, we show how we can protect quantum information from decoherence with two-qubit measurements, realizable with noisy two-qubit interactions.

  3. Effective scenario of loop quantum cosmology.

    PubMed

    Ding, You; Ma, Yongge; Yang, Jinsong

    2009-02-01

    Semiclassical states in isotropic loop quantum cosmology are employed to show that the improved dynamics has the correct classical limit. The effective Hamiltonian for the quantum cosmological model with a massless scalar field is thus obtained, which incorporates also the next to leading order quantum corrections. The possibility that the higher order correction terms may lead to significant departure from the leading order effective scenario is revealed. If the semiclassicality of the model is maintained in the large scale limit, there are great possibilities for a k=0 Friedmann expanding universe to undergo a collapse in the future due to the quantum gravity effect. Thus the quantum bounce and collapse may contribute a cyclic universe in the new scenario. PMID:19257499

  4. Fractional quantum Hall effect revisited

    NASA Astrophysics Data System (ADS)

    Jacak, J.; Łydżba, P.; Jacak, L.

    2015-10-01

    The topology-based explanation of the fractional quantum Hall effect (FQHE) is summarized. The cyclotron braid subgroups crucial for this approach are introduced in order to identify the origin of the Laughlin correlations in 2D (two-dimensional) Hall systems. Flux-tubes and vortices for composite fermions in their standard constructions are explained in terms of cyclotron braids. The derivation of the hierarchy of the FQHE is proposed by mapping onto the integer effect within the topology-based approach. The experimental observations of the FQHE supporting the cyclotron braid picture are reviewed with a special attention paid to recent experiments with a suspended graphene. The triggering role of a carrier mobility for organization of the fractional state in Hall configuration is emphasized. The prerequisites for the FQHE are indicated including topological conditions substantially increasing the previously accepted set of physical necessities. The explanation of numerical studies by exact diagonalizations of the fractional Chern insulator states is formulated in terms of the topology condition applied to the Berry field flux quantization. Some new ideas withz regard to the synthetic fractional states in the optical lattices are also formulated.

  5. Nuclear quantum effects in water

    NASA Astrophysics Data System (ADS)

    Morrone, Joseph; Car, Roberto

    2008-03-01

    In this work, a path integral Car-Parrinello molecular dynamicsootnotetextCPMD V3.11 Copyright IBM Corp 1990-2006, Copyright MPI fuer Festkoerperforschung Stuttgart 1997-2001. simulation of liquid water is performed. It is found that the inclusion of nuclear quantum effects systematically improves the agreement of first-principles simulations of liquid water with experiment. In addition, the proton momentum distribution is computed utilizing a recently developed ``open'' path integral molecular dynamics methodologyootnotetextJ.A. Morrone, V. Srinivasan, D. Sebastiani, R. Car J. Chem. Phys. 126 234504 (2007).. It is shown that these results, which are consistent with our computations of the liquid structure, are in good agreement with neutron Compton scattering dataootnotetextG.F. Reiter, J.C. Li, J. Mayers, T. Abdul-Redah, P. Platzman Braz. J. Phys. 34 142 (2004).. The remaining discrepancies between experiment and the present results are indicative of some degree of over-binding in the hydrogen bond network, likely engendered by the use of semi-local approximations to density functional theory in order to describe the electronic structure.

  6. Median recoil direction as a WIMP directional detection signal

    SciTech Connect

    Green, Anne M.; Morgan, Ben

    2010-03-15

    Direct detection experiments have reached the sensitivity to detect dark matter weakly interacting massive particles (WIMPs). Demonstrating that a putative signal is due to WIMPs, and not backgrounds, is a major challenge, however. The direction dependence of the WIMP scattering rate provides a potential WIMP 'smoking gun'. If the WIMP distribution is predominantly smooth, the Galactic recoil distribution is peaked in the direction opposite to the direction of Solar motion. Previous studies have found that, for an ideal detector, of order 10 WIMP events would be sufficient to reject isotropy, and rule out an isotropic background. We examine how the median recoil direction could be used to confirm the WIMP origin of an anisotropic recoil signal. Specifically, we determine the number of events required to confirm the direction of solar motion as the median inverse recoil direction at 95% confidence. We find that for zero background 31 events are required, a factor of {approx}2 more than are required to simply reject isotropy. We also investigate the effect of a nonzero isotropic background. As the background rate is increased the number of events required increases, initially fairly gradually and then more rapidly, once the signal becomes subdominant. We also discuss the effect of features in the speed distribution at large speeds, as found in recent high resolution simulations, on the median recoil direction.

  7. Median recoil direction as a WIMP directional detection signal

    NASA Astrophysics Data System (ADS)

    Green, Anne M.; Morgan, Ben

    2010-03-01

    Direct detection experiments have reached the sensitivity to detect dark matter weakly interacting massive particles (WIMPs). Demonstrating that a putative signal is due to WIMPs, and not backgrounds, is a major challenge, however. The direction dependence of the WIMP scattering rate provides a potential WIMP smoking gun. If the WIMP distribution is predominantly smooth, the Galactic recoil distribution is peaked in the direction opposite to the direction of Solar motion. Previous studies have found that, for an ideal detector, of order 10 WIMP events would be sufficient to reject isotropy, and rule out an isotropic background. We examine how the median recoil direction could be used to confirm the WIMP origin of an anisotropic recoil signal. Specifically, we determine the number of events required to confirm the direction of solar motion as the median inverse recoil direction at 95% confidence. We find that for zero background 31 events are required, a factor of 2 more than are required to simply reject isotropy. We also investigate the effect of a nonzero isotropic background. As the background rate is increased the number of events required increases, initially fairly gradually and then more rapidly, once the signal becomes subdominant. We also discuss the effect of features in the speed distribution at large speeds, as found in recent high resolution simulations, on the median recoil direction.

  8. Effective constraints for relativistic quantum systems

    NASA Astrophysics Data System (ADS)

    Bojowald, Martin; Tsobanjan, Artur

    2009-12-01

    Determining the physical Hilbert space is often considered the most difficult but crucial part of completing the quantization of a constrained system. In such a situation it can be more economical to use effective constraint methods, which are extended here to relativistic systems as they arise for instance in quantum cosmology. By sidestepping explicit constructions of states, such tools allow one to arrive much more feasibly at results for physical observables at least in semiclassical regimes. Several questions discussed recently regarding effective equations and state properties in quantum cosmology, including the spreading of states and quantum backreaction, are addressed by the examples studied here.

  9. Generalized effective description of loop quantum cosmology

    NASA Astrophysics Data System (ADS)

    Ashtekar, Abhay; Gupt, Brajesh

    2015-10-01

    The effective description of loop quantum cosmology (LQC) has proved to be a convenient platform to study phenomenological implications of the quantum bounce that resolves the classical big bang singularity. Originally, this description was derived using Gaussian quantum states with small dispersions. In this paper we present a generalization to incorporate states with large dispersions. Specifically, we derive the generalized effective Friedmann and Raychaudhuri equations and propose a generalized effective Hamiltonian which are being used in an ongoing study of the phenomenological consequences of a broad class of quantum geometries. We also discuss an interesting interplay between the physics of states with larger dispersions in standard LQC, and of sharply peaked states in (hypothetical) LQC theories with larger area gap.

  10. Quantum well interface broadening effects

    NASA Astrophysics Data System (ADS)

    Gavryushin, Vladimir

    2007-02-01

    We have derived and analyzed the wavefunctions and eigenstates for quantum wells (QW), broadened due to static interface disorder, within Discreet Variable Representation (DVR) approach of Colbert and Miller. The main advantage of this approach, which we have tested, is that it allows to obtain ab-initio and to analyze the shift and broadening of resonance states in a semiconductor quantum wells of different shapes. Calculations based on the convolution methods were used to include the influence of disorder to the formation of heterojunction interfaces.

  11. Classification of macroscopic quantum effects

    NASA Astrophysics Data System (ADS)

    Farrow, Tristan; Vedral, Vlatko

    2015-02-01

    We review canonical experiments on systems that have pushed the boundary between the quantum and classical worlds towards much larger scales, and discuss their unique features that enable quantum coherence to survive. Because the types of systems differ so widely, we use a case by case approach to identifying the different parameters and criteria that capture their behaviour in a quantum mechanical framework. We find it helpful to categorise systems into three broad classes defined by mass, spatio-temporal coherence, and number of particles. The classes are not mutually exclusive and in fact the properties of some systems fit into several classes. We discuss experiments by turn, starting with interference of massive objects like macromolecules and micro-mechanical resonators, followed by self-interference of single particles in complex molecules, before examining the striking advances made with superconducting qubits. Finally, we propose a theoretical basis for quantifying the macroscopic features of a system to lay the ground for a more systematic comparison of the quantum properties in disparate systems.

  12. Locality and universality of quantum memory effects

    PubMed Central

    Liu, B.-H.; Wimann, S.; Hu, X.-M.; Zhang, C.; Huang, Y.-F.; Li, C.-F.; Guo, G.-C.; Karlsson, A.; Piilo, J.; Breuer, H.-P.

    2014-01-01

    The modeling and analysis of the dynamics of complex systems often requires to employ non-Markovian stochastic processes. While there is a clear and well-established mathematical definition for non-Markovianity in the case of classical systems, the extension to the quantum regime recently caused a vivid debate, leading to many different proposals for the characterization and quantification of memory effects in the dynamics of open quantum systems. Here, we derive a mathematical representation for the non-Markovianity measure based on the exchange of information between the open system and its environment, which reveals the locality and universality of non-Markovianity in the quantum state space and substantially simplifies its numerical and experimental determination. We further illustrate the application of this representation by means of an all-optical experiment which allows the measurement of the degree of memory effects in a photonic quantum process with high accuracy. PMID:25209643

  13. Coherent quantum effects through dispersive bosonic media

    SciTech Connect

    Ye Saiyun; Yang Zhenbiao; Zheng Shibiao; Serafini, Alessio

    2010-07-15

    The coherent evolution of two qubits mediated by a set of bosonic field modes is investigated. By assuming a specific asymmetric encoding of the quantum states in the internal levels of the qubits, we show that entangling quantum gates can be realized, with high fidelity, even when a large number of mediating modes is involved. The effect of losses and imperfections on the gates' operation is also considered in detail.

  14. Possible observational effects of loop quantum cosmology

    SciTech Connect

    Mielczarek, Jakub

    2010-03-15

    In this paper, we consider realistic model of inflation embedded in the framework of loop quantum cosmology. Phase of inflation is preceded here by the phase of a quantum bounce. We show how parameters of inflation depend on the initial conditions established in the contracting, prebounce phase. Our investigations indicate that phase of the bounce easily sets proper initial conditions for the inflation. Subsequently, we study observational effects that might arise due to the quantum gravitational modifications. We perform preliminary observational constraints for the Barbero-Immirzi parameter {gamma}, critical density {rho}{sub c}, and parameter {lambda}. In the next step, we study effects on power spectrum of perturbations. We calculate spectrum of perturbations from the bounce and from the joined bounce+inflation phase. Based on these studies, we indicate a possible way to relate quantum cosmological models with the astronomical observations. Using the Sachs-Wolfe approximation, we calculate the spectrum of the superhorizontal CMB anisotropies. We show that quantum cosmological effects can, in the natural way, explain suppression of the low CMB multipoles. We show that fine-tuning is not required here, and the model is consistent with observations. We also analyze other possible probes of the quantum cosmologies and discuss perspectives of their implementation.

  15. Effective pure states for bulk quantum computation

    SciTech Connect

    Knill, E.; Chuang, I.; Laflamme, R.

    1997-11-01

    In bulk quantum computation one can manipulate a large number of indistinguishable quantum computers by parallel unitary operations and measure expectation values of certain observables with limited sensitivity. The initial state of each computer in the ensemble is known but not pure. Methods for obtaining effective pure input states by a series of manipulations have been described by Gershenfeld and Chuang (logical labeling) and Corey et al. (spatial averaging) for the case of quantum computation with nuclear magnetic resonance. We give a different technique called temporal averaging. This method is based on classical randomization, requires no ancilla qubits and can be implemented in nuclear magnetic resonance without using gradient fields. We introduce several temporal averaging algorithms suitable for both high temperature and low temperature bulk quantum computing and analyze the signal to noise behavior of each.

  16. Casimir effect in a quantum space-time

    NASA Astrophysics Data System (ADS)

    Gambini, Rodolfo; Olmedo, Javier; Pullin, Jorge

    2015-06-01

    We apply quantum field theory in quantum space-time techniques to study the Casimir effect for large spherical shells. As background we use the recently constructed exact quantum solution for spherically symmetric vacuum space-time in loop quantum gravity. All calculations are finite and one recovers the usual results without the need for regularization or renormalization. This is an example of how loop quantum gravity provides a natural resolution to the infinities of quantum field theories.

  17. Berkeley Experiments on Superfluid Macroscopic Quantum Effects

    SciTech Connect

    Packard, Richard

    2006-09-07

    This paper provides a brief history of the evolution of the Berkeley experiments on macroscopic quantum effects in superfluid helium. The narrative follows the evolution of the experiments proceeding from the detection of single vortex lines to vortex photography to quantized circulation in 3He to Josephson effects and superfluid gyroscopes in both 4He and 3He.

  18. Quantum metrology and estimation of Unruh effect.

    PubMed

    Wang, Jieci; Tian, Zehua; Jing, Jiliang; Fan, Heng

    2014-01-01

    We study the quantum metrology for a pair of entangled Unruh-Dewitt detectors when one of them is accelerated and coupled to a massless scalar field. Comparing with previous schemes, our model requires only local interaction and avoids the use of cavities in the probe state preparation process. We show that the probe state preparation and the interaction between the accelerated detector and the external field have significant effects on the value of quantum Fisher information, correspondingly pose variable ultimate limit of precision in the estimation of Unruh effect. We find that the precision of the estimation can be improved by a larger effective coupling strength and a longer interaction time. Alternatively, the energy gap of the detector has a range that can provide us a better precision. Thus we may adjust those parameters and attain a higher precision in the estimation. We also find that an extremely high acceleration is not required in the quantum metrology process. PMID:25424772

  19. Quantum metrology and estimation of Unruh effect

    PubMed Central

    Wang, Jieci; Tian, Zehua; Jing, Jiliang; Fan, Heng

    2014-01-01

    We study the quantum metrology for a pair of entangled Unruh-Dewitt detectors when one of them is accelerated and coupled to a massless scalar field. Comparing with previous schemes, our model requires only local interaction and avoids the use of cavities in the probe state preparation process. We show that the probe state preparation and the interaction between the accelerated detector and the external field have significant effects on the value of quantum Fisher information, correspondingly pose variable ultimate limit of precision in the estimation of Unruh effect. We find that the precision of the estimation can be improved by a larger effective coupling strength and a longer interaction time. Alternatively, the energy gap of the detector has a range that can provide us a better precision. Thus we may adjust those parameters and attain a higher precision in the estimation. We also find that an extremely high acceleration is not required in the quantum metrology process. PMID:25424772

  20. Spectral effects in quantum teleportation

    SciTech Connect

    Humble, Travis S.; Grice, Warren P.

    2007-02-15

    We use a multimode description of polarization-encoded qubits to analyze the quantum teleportation protocol. Specifically, we investigate how the teleportation fidelity depends on the spectral correlations inherent to polarization-entangled photons generated by type-II spontaneous parametric down conversion. We find that the maximal obtainable fidelity depends on the spectral entanglement carried by the joint probability amplitude, a result which we quantify for the case of a joint spectrum approximated by a correlated Gaussian function. We contrast these results with a similar analysis of the visibility obtained in a polarization-correlation experiment.

  1. Spectral Effects in Quantum Teleportation

    SciTech Connect

    Humble, Travis S; Grice, Warren P

    2007-01-01

    We use a multimode description of polarization-encoded qubits to analyze the quantum teleportation protocol. Specifically, we investigate how the teleportation fidelity depends on the spectral correlations inherent to polarization-entangled photons generated by type-II spontaneous parametric down conversion. We find that the maximal obtainable fidelity depends on the spectral entanglement carried by the joint probability amplitude, a result which we quantify for the case of a joint spectrum approximated by a correlated Gaussian function. We contrast these results with a similar analysis of the visibility obtained in a polarization-correlation experiment.

  2. Electron recombination in low-energy nuclear recoils tracks in liquid argon

    NASA Astrophysics Data System (ADS)

    Wojcik, M.

    2016-02-01

    This paper presents an analysis of electron-ion recombination processes in ionization tracks of recoiled atoms in liquid argon (LAr) detectors. The analysis is based on the results of computer simulations which use realistic models of electron transport and reactions. The calculations reproduce the recent experimental results of the ionization yield from 6.7 keV nuclear recoils in LAr. The statistical distribution of the number of electrons that escape recombination is found to deviate from the binomial distribution, and estimates of recombination fluctuations for nuclear recoils tracks are obtained. A study of the recombination kinetics shows that a significant part of electrons undergo very fast static recombination, an effect that may be responsible for the weak drift-field dependence of the ionization yield from nuclear recoils in some noble liquids. The obtained results can be useful in the search for hypothetical dark matter particles and in other studies that involve detection of recoiled nuclei.

  3. Quantum Plasma Effects in the Classical Regime

    SciTech Connect

    Brodin, G.; Marklund, M.; Manfredi, G.

    2008-05-02

    For quantum effects to be significant in plasmas it is often assumed that the temperature over density ratio must be small. In this paper we challenge this assumption by considering the contribution to the dynamics from the electron spin properties. As a starting point we consider a multicomponent plasma model, where electrons with spin-up and spin-down are regarded as different fluids. By studying the propagation of Alfven wave solitons we demonstrate that quantum effects can survive in a relatively high-temperature plasma. The consequences of our results are discussed.

  4. Spatially dependent Kondo effect in quantum corrals.

    PubMed

    Rossi, Enrico; Morr, Dirk K

    2006-12-01

    We study the Kondo screening of a single magnetic impurity inside a nonmagnetic quantum corral located on the surface of a metallic host system. We show that the spatial structure of the corral's eigenmodes leads to a spatially dependent Kondo effect whose signatures are spatial variations of the Kondo temperature T K. Moreover, we predict that the Kondo screening is accompanied by the formation of multiple Kondo resonances with characteristic spatial patterns. Our results open new possibilities to manipulate and explore the Kondo effect by using quantum corrals. PMID:17280221

  5. Epitaxial silicide formation on recoil-implanted substrates

    SciTech Connect

    Hashimoto, Shin; Egashira, Kyoko; Tanaka, Tomoya; Etoh, Ryuji; Hata, Yoshifumi; Tung, R. T.

    2005-01-15

    An epitaxy-on-recoil-implanted-substrate (ERIS) technique is presented. A disordered surface layer, generated by forward recoil implantation of {approx}0.7-3x10{sup 15} cm{sup -2} of oxygen during Ar plasma etching of surface oxide, is shown to facilitate the subsequent epitaxial growth of {approx}25-35-nm-thick CoSi{sub 2} layers on Si(100). The dependence of the epitaxial fraction of the silicide on the recoil-implantation parameters is studied in detail. A reduction in the silicide reaction rate due to recoil-implanted oxygen is shown to be responsible for the observed epitaxial formation, similar to mechanisms previously observed for interlayer-mediated growth techniques. Oxygen is found to remain inside the fully reacted CoSi{sub 2} layer, likely in the form of oxide precipitates. The presence of these oxide precipitates, with only a minor effect on the sheet resistance of the silicide layer, has a surprisingly beneficial effect on the thermal stability of the silicide layers. The agglomeration of ERIS-grown silicide layers on polycrystalline Si is significantly suppressed, likely from a reduced diffusivity due to oxygen in the grain boundaries. The implications of the present technique for the processing of deep submicron devices are discussed.

  6. Recoil Experiments Using a Compressed Air Cannon

    NASA Astrophysics Data System (ADS)

    Taylor, Brett

    2006-12-01

    Ping-Pong vacuum cannons, potato guns, and compressed air cannons are popular and dramatic demonstrations for lecture and lab.1-3 Students enjoy them for the spectacle, but they can also be used effectively to teach physics. Recently we have used a student-built compressed air cannon as a laboratory activity to investigate impulse, conservation of momentum, and kinematics. It is possible to use the cannon, along with the output from an electronic force plate, as the basis for many other experiments in the laboratory. In this paper, we will discuss the recoil experiment done by our students in the lab and also mention a few other possibilities that this apparatus could be used for.

  7. Measurement of Nuclear Recoils in the CDMS II Dark Matter Search

    NASA Astrophysics Data System (ADS)

    Fallows, Scott M.

    The Cryogenic Dark Matter Search (CDMS) experiment is designed to directly detect elastic scatters of weakly-interacting massive dark matter particles (WIMPs), on target nuclei in semiconductor crystals composed of Si and Ge. These scatters would occur very rarely, in an overwhelming background composed primarily of electron recoils from photons and electrons, as well as a smaller but non-negligible background of WIMP-like nuclear recoils from neutrons. The CDMS~II generation of detectors simultaneously measure ionization and athermal phonon signals from each scatter, allowing discrimination against virtually all electron recoils in the detector bulk. Pulse-shape timing analysis allows discrimination against nearly all remaining electron recoils taking place near detector surfaces. Along with carefully limited neutron backgrounds, this experimental program allowed for "background-free'' operation of CDMS~II at Soudan, with less than one background event expected in each WIMP-search analysis. As a result, exclusionary upper-limits on WIMP-nucleon interaction cross section were placed over a wide range of candidate WIMP masses, ruling out large new regions of parameter space. These results, like any others, are subject to a variety of systematic effects that may alter their final interpretations. A primary focus of this dissertation will be difficulties in precisely calibrating the energy scale for nuclear recoil events like those from WIMPs. Nuclear recoils have suppressed ionization signals relative to electron recoils of the same recoil energy, so the response of the detectors is calibrated differently for each recoil type. The overall normalization and linearity of the energy scale for electron recoils in CDMS~II detectors is clearly established by peaks of known gamma energy in the ionization spectrum of calibration data from a 133Ba source. This electron-equivalent keVee) energy scale enables calibration of the total phonon signal (keVt) by enforcing unity yield for electron recoils, in aggregate. Subtracting an event's Luke phonon contribution from its calibrated total phonon energy (keV t), as measured by the ionization signal, results in a valid measure of the true recoil energy (keVr) for both electron and nuclear recoils. I discuss systematic uncertainties affecting the reconstruction of this recoil energy, the primary analysis variable, and use several methods to constrain their magnitude. I present the resulting adjusted WIMP limits and discuss their impact in the context of current and projected constraints on the parameter space for WIMP interactions.

  8. Gravitational Recoil Velocities from Eccentric Binary Black Hole Mergers

    NASA Astrophysics Data System (ADS)

    Sopuerta, Carlos F.; Yunes, Nicols; Laguna, Pablo

    2007-02-01

    The formation and growth of supermassive black holes is a key issue to unveil the secrets of galaxy formation. In particular, the gravitational recoil produced in the merger of unequal mass black hole binaries could have a number of astrophysical implications, such as the ejection of black holes from the host galaxy or globular cluster. We present estimates of the recoil velocity that include the effect of small eccentricities. The approach is especially suited for the last stage of the merger, where most of the emission of linear momentum in gravitational waves takes place. Supplementing our estimates with post-Newtonian approximations, we obtain lower and upper bounds that constrain previous recoil velocities estimates, as well as a best estimate that agrees with numerical simulations in the quasi-circular case. For eccentricities e<=0.1, the maximum recoil is found for a mass ratio of M1/M2~0.38 with velocities in the range 79-216 km s-1 (1 + e) and a best estimate of 167 km s-1 (1 + e).

  9. Recoil-decay tagging spectroscopy of 74162W88

    NASA Astrophysics Data System (ADS)

    Li, H. J.; Cederwall, B.; Bäck, T.; Qi, C.; Doncel, M.; Jakobsson, U.; Auranen, K.; Bönig, S.; Drummond, M. C.; Grahn, T.; Greenlees, P.; HerzáÅ, A.; Julin, R.; Juutinen, S.; Konki, J.; Kröll, T.; Leino, M.; McPeake, C.; O'Donnell, D.; Page, R. D.; Pakarinen, J.; Partanen, J.; Peura, P.; Rahkila, P.; Ruotsalainen, P.; Sandzelius, M.; Sarén, J.; Sayǧı, B.; Scholey, C.; Sorri, J.; Stolze, S.; Taylor, M. J.; Thornthwaite, A.; Uusitalo, J.; Xiao, Z. G.

    2015-07-01

    Excited states in the highly neutron-deficient nucleus 162W have been investigated via the 92Mo (78Kr,2α ) 162W reaction. Prompt γ rays were detected by the JUROGAM II high-purity germanium detector array and the recoiling fusion-evaporation products were separated by the recoil ion transport unit (RITU) gas-filled recoil separator and identified with the gamma recoil electron alpha tagging (GREAT) spectrometer at the focal plane of RITU. γ rays from 162W were identified uniquely using mother-daughter and mother-daughter-granddaughter α -decay correlations. The observation of a rotational-like ground-state band is interpreted within the framework of total Routhian surface (TRS) calculations, which suggest an axially symmetric ground-state shape with a γ -soft minimum at β2≈0.15 . Quasiparticle alignment effects are discussed based on cranked shell model calculations. New measurements of the 162W ground-state α -decay energy and half-life were also performed. The observed α -decay energy agrees with previous measurements. The half-life of 162W was determined to be t1 /2=990 (30 ) ms. This value deviates significantly from the currently adopted value of t1 /2=1360 (70 ) ms. In addition, the α -decay energy and half-life of 166Os were measured and found to agree with the adopted values.

  10. Introducing quantum effects in classical theories

    NASA Astrophysics Data System (ADS)

    Fabris, J. C.; Piattella, O. F.; Rodrigues, D. C.; Chauvineau, B.; Daouda, M. H.

    2016-01-01

    In this paper, we explore two different ways of implementing quantum effects in a classical structure. The first one is through an external field. The other one is modifying the classical conservation laws. In both cases, the consequences for the description of the evolution of the universe are discussed.

  11. Surface distortion effects on quantum dot helium

    NASA Astrophysics Data System (ADS)

    Encinosa, Mario; Etemadi, Babak

    1999-06-01

    The Schrdinger equation for a quantum mechanical particle constrained to a surface includes a potential term dependent on surface curvature. We use differential forms to derive this term and employ Monge representations for two surfaces to obtain specific expressions for the potential. We calculate the first order perturbative effect of this potential on the ground state energy of model quantum dot helium. We find that the energy shift can be sensitive to the detailed shape of the surface distortion. This dependence arises from the Coulomb repulsion between the electron pair, which causes each electron to preferentially sample (or not sample) regions where physical curvature leads to comparatively large values of the distortion potential.

  12. Significant Quantum Effects in Hydrogen Activation

    PubMed Central

    2014-01-01

    Dissociation of molecular hydrogen is an important step in a wide variety of chemical, biological, and physical processes. Due to the light mass of hydrogen, it is recognized that quantum effects are often important to its reactivity. However, understanding how quantum effects impact the reactivity of hydrogen is still in its infancy. Here, we examine this issue using a well-defined Pd/Cu(111) alloy that allows the activation of hydrogen and deuterium molecules to be examined at individual Pd atom surface sites over a wide range of temperatures. Experiments comparing the uptake of hydrogen and deuterium as a function of temperature reveal completely different behavior of the two species. The rate of hydrogen activation increases at lower sample temperature, whereas deuterium activation slows as the temperature is lowered. Density functional theory simulations in which quantum nuclear effects are accounted for reveal that tunneling through the dissociation barrier is prevalent for H2 up to ∼190 K and for D2 up to ∼140 K. Kinetic Monte Carlo simulations indicate that the effective barrier to H2 dissociation is so low that hydrogen uptake on the surface is limited merely by thermodynamics, whereas the D2 dissociation process is controlled by kinetics. These data illustrate the complexity and inherent quantum nature of this ubiquitous and seemingly simple chemical process. Examining these effects in other systems with a similar range of approaches may uncover temperature regimes where quantum effects can be harnessed, yielding greater control of bond-breaking processes at surfaces and uncovering useful chemistries such as selective bond activation or isotope separation. PMID:24684530

  13. Significant Quantum Effects in Hydrogen Activation

    SciTech Connect

    Kyriakou, Georgios; Davidson, Erlend R.; Peng, Guowen; Roling, Luke T.; Singh, Suyash; Boucher, Matthew B.; Marcinkowski, Matthew D.; Mavrikakis, Manos; Michaelides, Angelos; Sykes, E. Charles H.

    2014-03-31

    Dissociation of molecular hydrogen is an important step in a wide variety of chemical, biological, and physical processes. Due to the light mass of hydrogen, it is recognized that quantum effects are often important to its reactivity. However, understanding how quantum effects impact the reactivity of hydrogen is still in its infancy. Here, we examine this issue using a well-defined Pd/Cu(111) alloy that allows the activation of hydrogen and deuterium molecules to be examined at individual Pd atom surface sites over a wide range of temperatures. Experiments comparing the uptake of hydrogen and deuterium as a function of temperature reveal completely different behavior of the two species. The rate of hydrogen activation increases at lower sample temperature, whereas deuterium activation slows as the temperature is lowered. Density functional theory simulations in which quantum nuclear effects are accounted for reveal that tunneling through the dissociation barrier is prevalent for H2 up to 190 K and for D2 up to 140 K. Kinetic Monte Carlo simulations indicate that the effective barrier to H2 dissociation is so low that hydrogen uptake on the surface is limited merely by thermodynamics, whereas the D2 dissociation process is controlled by kinetics. These data illustrate the complexity and inherent quantum nature of this ubiquitous and seemingly simple chemical process. Examining these effects in other systems with a similar range of approaches may uncover temperature regimes where quantum effects can be harnessed, yielding greater control of bond-breaking processes at surfaces and uncovering useful chemistries such as selective bond activation or isotope separation.

  14. Doppler- and recoil-free laser excitation of Rydberg states via three-photon transitions

    SciTech Connect

    Ryabtsev, I. I.; Beterov, I. I.; Tretyakov, D. B.; Entin, V. M.; Yakshina, E. A.

    2011-11-15

    Three-photon laser excitation of Rydberg states by three different laser beams can be arranged in a starlike geometry that simultaneously eliminates the recoil effect and Doppler broadening. Our analytical and numerical calculations for a particular laser excitation scheme 5S{sub 1/2}{yields}5P{sub 3/2}{yields}6S{sub 1/2}{yields}nP in Rb atoms have shown that, compared to the one- and two-photon laser excitation, this approach provides much narrower linewidth and longer coherence time for both cold atom samples and hot vapors, if the intermediate one-photon resonances of the three-photon transition are detuned by more than respective single-photon Doppler widths. This method can be used to improve fidelity of Rydberg quantum gates and precision of spectroscopic measurements in Rydberg atoms.

  15. Effective equilibrium theory of nonequilibrium quantum transport

    SciTech Connect

    Dutt, Prasenjit; Koch, Jens; Han, Jong; Le Hur, Karyn

    2011-12-15

    The theoretical description of strongly correlated quantum systems out of equilibrium presents several challenges and a number of open questions persist. Here, we focus on nonlinear electronic transport through an interacting quantum dot maintained at finite bias using a concept introduced by Hershfield [S. Hershfield, Phys. Rev. Lett. 70 2134 (1993)] whereby one can express such nonequilibrium quantum impurity models in terms of the system's Lippmann-Schwinger operators. These scattering operators allow one to reformulate the nonequilibrium problem as an effective equilibrium problem associated with a modified Hamiltonian. In this paper, we provide a pedagogical analysis of the core concepts of the effective equilibrium theory. First, we demonstrate the equivalence between observables computed using the Schwinger-Keldysh framework and the effective equilibrium approach, and relate Green's functions in the two theoretical frameworks. Second, we expound some applications of this method in the context of interacting quantum impurity models. We introduce a novel framework to treat effects of interactions perturbatively while capturing the entire dependence on the bias voltage. For the sake of concreteness, we employ the Anderson model as a prototype for this scheme. Working at the particle-hole symmetric point, we investigate the fate of the Abrikosov-Suhl resonance as a function of bias voltage and magnetic field. - Highlights: > Reformulation of steady-state nonequilibrium quantum transport, following Hershfield. > Derivation of effective equilibrium density operator using the 'open-system' approach. > Equivalence with the Keldysh description and formulas relating the two approaches. > Novel framework to treat interactions perturbatively. > Application to nonequilibrium Anderson model and fate of Abrikosov-Suhl resonance.

  16. Quantum Anomalous Hall Effect in Hg_1-yMn_yTe Quantum Wells

    SciTech Connect

    Liu, Chao-Xing; Qi, Xiao-Liang; Dai, Xi; Fang, Zhong; Zhang, Shou-Cheng; /Stanford U., Phys. Dept.

    2010-03-19

    The quantum Hall effect is usually observed when the two-dimensional electron gas is subjected to an external magnetic field, so that their quantum states form Landau levels. In this work we predict that a new phenomenon, the quantum anomalous Hall effect, can be realized in Hg{sub 1-y}Mn{sub y}Te quantum wells, without the external magnetic field and the associated Landau levels. This effect arises purely from the spin polarization of the Mn atoms, and the quantized Hall conductance is predicted for a range of quantum well thickness and the concentration of the Mn atoms. This effect enables dissipationless charge current in spintronics devices.

  17. Quantum Anomalous Hall Effect in Magnetically Doped InAs/GaSb Quantum Wells

    NASA Astrophysics Data System (ADS)

    Wang, Qing-Ze; Liu, Xin; Zhang, Hai-Jun; Samarth, Nitin; Zhang, Shou-Cheng; Liu, Chao-Xing

    2014-10-01

    The quantum anomalous Hall effect has recently been observed experimentally in thin films of Cr-doped (Bi,Sb)2Te3 at a low temperature (30 mK). In this work, we propose realizing the quantum anomalous Hall effect in more conventional diluted magnetic semiconductors with magnetically doped InAs/GaSb type-II quantum wells. Based on a four-band model, we find an enhancement of the Curie temperature of ferromagnetism due to band edge singularities in the inverted regime of InAs/GaSb quantum wells. Below the Curie temperature, the quantum anomalous Hall effect is confirmed by the direct calculation of Hall conductance. The parameter regime for the quantum anomalous Hall phase is identified based on the eight-band Kane model. The high sample quality and strong exchange coupling make magnetically doped InAs/GaSb quantum wells good candidates for realizing the quantum anomalous Hall insulator at a high temperature.

  18. A programmable quantum current standard from the Josephson and the quantum Hall effects

    SciTech Connect

    Poirier, W. Lafont, F.; Djordjevic, S.; Schopfer, F.; Devoille, L.

    2014-01-28

    We propose a way to realize a programmable quantum current standard (PQCS) from the Josephson voltage standard and the quantum Hall resistance standard (QHR) exploiting the multiple connection technique provided by the quantum Hall effect (QHE) and the exactness of the cryogenic current comparator. The PQCS could lead to breakthroughs in electrical metrology like the realization of a programmable quantum current source, a quantum ampere-meter, and a simplified closure of the quantum metrological triangle. Moreover, very accurate universality tests of the QHE could be performed by comparing PQCS based on different QHRs.

  19. Gas powered fluid gun with recoil mitigation

    SciTech Connect

    Grubelich, Mark C; Yonas, Gerold

    2013-11-12

    A gas powered fluid gun for propelling a stream or slug of a fluid at high velocity toward a target. Recoil mitigation is provided that reduces or eliminates the associated recoil forces, with minimal or no backwash. By launching a quantity of water in the opposite direction, net momentum forces are reduced or eliminated. Examples of recoil mitigation devices include a cone for making a conical fluid sheet, a device forming multiple impinging streams of fluid, a cavitating venturi, one or more spinning vanes, or an annular tangential entry/exit.

  20. Quantum effects in thermal conduction: Nonequilibrium quantum discord and entanglement

    SciTech Connect

    Wu Lianao; Segal, Dvira

    2011-07-15

    We study the process of heat transfer through an entangled pair of two-level systems, demonstrating the role of quantum correlations in this nonequilibrium process. While quantum correlations generally degrade with increasing the temperature bias, introducing spatial asymmetry leads to an intricate behavior: connecting the qubits unequally to the reservoirs, one finds that quantum correlations persist and increase with the temperature bias when the system is more weakly linked to the hot reservoir. In the reversed case, linking the system more strongly to the hot bath, the opposite, more natural behavior is observed, with quantum correlations being strongly suppressed upon increasing the temperature bias.

  1. Quantum confined Stark effect in Gaussian quantum wells: A tight-binding study

    SciTech Connect

    Ramrez-Morales, A.; Martnez-Orozco, J. C.; Rodrguez-Vargas, I.

    2014-05-15

    The main characteristics of the quantum confined Stark effect (QCSE) are studied theoretically in quantum wells of Gaussian profile. The semi-empirical tight-binding model and the Green function formalism are applied in the numerical calculations. A comparison of the QCSE in quantum wells with different kinds of confining potential is presented.

  2. Retention studies of recoiling daughter nuclides of 225Ac in polymer vesicles.

    PubMed

    Wang, G; de Kruijff, R M; Rol, A; Thijssen, L; Mendes, E; Morgenstern, A; Bruchertseifer, F; Stuart, M C A; Wolterbeek, H T; Denkova, A G

    2014-02-01

    Alpha radionuclide therapy is steadily gaining importance and a large number of pre-clinical and clinical studies have been carried out. However, due to the recoil effects the daughter recoil atoms, most of which are alpha emitters as well, receive energies that are much higher than the energies of chemical bonds resulting in decoupling of the radionuclide from common targeting agents. Here, we demonstrate that polymer vesicles (i.e. polymersomes) can retain recoiling daughter nuclei based on an experimental study examining the retention of (221)Fr and (213)Bi when encapsulating (225)Ac. PMID:24374072

  3. Polymer quantum effects on compact stars models

    NASA Astrophysics Data System (ADS)

    Chacn-Acosta, Guillermo; Hernandez-Hernandez, Hctor H.

    2015-03-01

    In this work we study a completely degenerate Fermi gas at zero temperature by a semiclassical approximation for a Hamiltonian that arises in polymer quantum mechanics. Polymer quantum systems are quantum mechanical models quantized in a similar way as in loop quantum gravity, allowing the study of the discreteness of space and other features of the loop quantization in a simplified way. We obtain the polymer modified thermodynamical properties for this system by noticing that the corresponding Fermi energy is exactly the same as if one directly polymerizes the momentum pF. We also obtain the expansion of the corresponding thermodynamical variables in terms of small values of the polymer length scale ?. We apply these results to study a simple model of a compact one-dimensional star where the gravitational collapse is supported by electron degeneracy pressure. As a consequence, polymer corrections to the mass of the object are found. By using bounds for the polymer length found in Bose-Einstein condensates experiments we compute the modification in the mass of the compact object due to polymer effects of order 10-8. This result is similar to the other order found by different approaches such as generalized uncertainty principle (GUP), and that certainly is within the error reported in typical measurements of white dwarf masses.

  4. Reentrant Quantum Hall Effect at Low Fields

    NASA Astrophysics Data System (ADS)

    Jiang, H. W.

    1997-03-01

    Several recent experiments, on various semiconductor heterostructures, have shown that an insulating phase at zero field can undergo a phase transition to the quantum Hall effect phase in an applied magnetic field.(see for example, H. W. Jiang, C. E. Johnson, K. L. Wang, and S. T. Hannahs, Phys. Rev. Lett. 71, 1439 (1993).) To understand this phenomena, we have studied the evolution of the quantum Hall effect at low fields.(I. Glozman, C. E. Johnson, and H. W. Jiang, Phys. Rev. Lett. 74, 594 (1995).) We found that the chemical potential of the lowest delocalized-state band not only deviates from the host Landau level center, but also "floats up" above the Fermi level as B goes to zero. In the region where the floating of delocalized states is observed, we have also found that the position of the conductivity minimum in the density - field plane to be strongly path-dependent. This path dependence has, in fact, given us information to quantitatively link the floating to Landau level mixing.(I. Glozman, C. E. Johnson, and H. W. Jiang, Phys. Rev. B 52, R14348 (1995).) The similar studies have been extended to the fractional quantum Hall effect regime.(L. W. Wong, H. W. Jiang, and W. J. Schaff, Phys. Rev. B54, Dec. 15, in press (1996).) The potential floating of the delocalized states of composite-fermions in a vanishing effective field will be discussed.

  5. Quantum gravity effects in the Kerr spacetime

    SciTech Connect

    Reuter, M.; Tuiran, E.

    2011-02-15

    We analyze the impact of the leading quantum gravity effects on the properties of black holes with nonzero angular momentum by performing a suitable renormalization group improvement of the classical Kerr metric within quantum Einstein gravity. In particular, we explore the structure of the horizons, the ergosphere, and the static limit surfaces as well as the phase space available for the Penrose process. The positivity properties of the effective vacuum energy-momentum tensor are also discussed and the 'dressing' of the black hole's mass and angular momentum are investigated by computing the corresponding Komar integrals. The pertinent Smarr formula turns out to retain its classical form. As for their thermodynamical properties, a modified first law of black-hole thermodynamics is found to be satisfied by the improved black holes (to second order in the angular momentum); the corresponding Bekenstein-Hawking temperature is not proportional to the surface gravity.

  6. Quantum renormalization of the spin Hall effect.

    PubMed

    Gu, Bo; Gan, Jing-Yu; Bulut, Nejat; Ziman, Timothy; Guo, Guang-Yu; Nagaosa, Naoto; Maekawa, Sadamichi

    2010-08-20

    By quantum Monte Carlo simulation of a realistic multiorbital Anderson impurity model, we study the spin-orbit interaction (SOI) of an Fe impurity in Au host metal. We show, for the first time, that the SOI is strongly renormalized by the quantum spin fluctuation. Based on this mechanism, we can explain why the gigantic spin Hall effect in Au with Fe impurities was observed in recent experiments, while it is not visible in the anomalous Hall effect. In addition, we show that the SOI is strongly renormalized by the Coulomb correlation U. Based on this picture, we can explain past discrepancies in the calculated orbital angular momenta for an Fe impurity in an Au host. PMID:20868117

  7. Simulations of Recoiling Massive Black Holes

    NASA Astrophysics Data System (ADS)

    Guedes, Javiera; Madau, Piero; Mayer, Lucio; Kuhlen, Michael; Diemand, Jrg; Zemp, Marcel

    2010-05-01

    The coalescence of black hole binaries is a significant source of gravitational wave radiation. The typically asymmetric nature of this emission, which carries linear momentum, can result in the recoil of the black hole remnant with velocities in the range 100 < Vrecoil < 3750 km s-1. The detectability of recoiling massive black holes (MBH) as off-nuclear QSOs is tightly connected with the properties of the host galaxy, which determine the MBH's orbit and fuel reservoir. We present the results of N-body simulations of recoiling MBHs in high-resolution, non-axisymmetric potentials. We find that if the recoil velocities are high enough to reach regions of the galaxy dominated by the generally triaxial dark matter distribution, the return time is significantly extended when compared to a spherical distribution. We also perform simulations of recoiling MBHs traveling in gas merger remnants, where large amounts of gas have been funneled to the central regions, In this case, the MBHs remain within R<1 kpc from the center of the host even for high recoil velocities (Vrecoil = 1200 km s-1) due to the compactness of the remnant galaxy's nuclear disk. We discuss the implications of both scenarios for detectability.

  8. The pinning effect in quantum dots

    SciTech Connect

    Monisha, P. J.; Mukhopadhyay, Soma

    2014-04-24

    The pinning effect is studied in a Gaussian quantum dot using the improved Wigner-Brillouin perturbation theory (IWBPT) in the presence of electron-phonon interaction. The electron ground state plus one phonon state is degenerate with the electron in the first excited state. The electron-phonon interaction lifts the degeneracy and the first excited states get pinned to the ground state plus one phonon state as we increase the confinement frequency.

  9. Grand unification and enhanced quantum gravitational effects.

    PubMed

    Calmet, Xavier; Hsu, Stephen D H; Reeb, David

    2008-10-24

    In grand unified theories with large numbers of fields, renormalization effects significantly modify the scale at which quantum gravity becomes strong. This in turn can modify the boundary conditions for coupling constant unification, if higher dimensional operators induced by gravity are taken into consideration. We show that the generic size of, and the uncertainty in, these effects from gravity can be larger than the two-loop corrections typically considered in renormalization group analyses of unification. In some cases, gravitational effects of modest size can render unification impossible. PMID:18999739

  10. Quantum Gravitational Effects and Grand Unification

    SciTech Connect

    Calmet, Xavier; Hsu, Stephen D. H.; Reeb, David

    2008-11-23

    In grand unified theories with large numbers of fields, renormalization effects significantly modify the scale at which quantum gravity becomes strong. This in turn can modify the boundary conditions for coupling constant unification, if higher dimensional operators induced by gravity are taken into consideration. We show that the generic size of, and the uncertainty in, these effects from gravity can be larger than the two-loop corrections typically considered in renormalization group analyses of unification. In some cases, gravitational effects of modest size can render unification impossible.

  11. Grand Unification and Enhanced Quantum Gravitational Effects

    SciTech Connect

    Calmet, Xavier; Hsu, Stephen D. H.; Reeb, David

    2008-10-24

    In grand unified theories with large numbers of fields, renormalization effects significantly modify the scale at which quantum gravity becomes strong. This in turn can modify the boundary conditions for coupling constant unification, if higher dimensional operators induced by gravity are taken into consideration. We show that the generic size of, and the uncertainty in, these effects from gravity can be larger than the two-loop corrections typically considered in renormalization group analyses of unification. In some cases, gravitational effects of modest size can render unification impossible.

  12. Quantum nonlocal effects on optical properties of spherical nanoparticles

    SciTech Connect

    Moradi, Afshin

    2015-02-15

    To study the scattering of electromagnetic radiation by a spherical metallic nanoparticle with quantum spatial dispersion, we develop the standard nonlocal Mie theory by allowing for the excitation of the quantum longitudinal plasmon modes. To describe the quantum nonlocal effects, we use the quantum longitudinal dielectric function of the system. As in the standard Mie theory, the electromagnetic fields are expanded in terms of spherical vector wavefunctions. Then, the usual Maxwell boundary conditions are imposed plus the appropriate additional boundary conditions. Examples of calculated extinction spectra are presented, and it is found that the frequencies of the subsidiary peaks, due to quantum bulk plasmon excitations exhibit strong dependence on the quantum spatial dispersion.

  13. Investigation of potential profile effects in quantum dot and onion-like quantum dot-quantum well on optical properties

    NASA Astrophysics Data System (ADS)

    Elyasi, P.; SalmanOgli, A.

    2014-05-01

    This paper investigates GaAs/AlGaAs modified quantum dot nanocrystal and GaAs/AlGaAs/GaAs/AlGaAs quantum dot-quantum well heteronanocrystal. These quantum dots have been analyzed by the finite element numerical methods. Simulations carried out for state n=1, l=0, and m=0 which are original, orbital, and magnetic state of quantum numbers. The effects of variation in radius layers such as total radius, GaAs core, shell and AlGaAs barriers radius on the wavelength and emission coefficient are studied. For the best time, it has also investigated the effect of mole fraction on emission coefficient. Meanwhile, one of the problems in biological applications is alteration of the emission wavelength of a quantum dot by changing in its dimension. This problem will be resolved by changing in potential profile.

  14. Quantum and medium effects in (resonant) leptogenesis

    NASA Astrophysics Data System (ADS)

    Hohenegger, Andreas

    2014-03-01

    Leptogenesis offers a very attractive explanation for the origin of the baryon asymmetry of the universe. Such scenarios based on leptonic CP-violation can be realized already within minimalistic seesaw extensions of the standard model. Apart from model building issues the answer to the question of whether a given particle theory can explain the observed baryon number density depends also on the detailed statistical evolution of the asymmetry. The CP-violation within a given model leads to an asymmetry only if it is accompanied by an out-of-equilibrium evolution in the early universe. Most existing analyses employ Boltzmann-like equations (BEs) to describe it. In this context fundamental issues arise which can be addressed in the framework of non-equilibrium quantum field theory (NEQFT). Here, the relevance of quantum and medium effects for thermal leptogenesis is investigated. Within the 2PI-formalism of NEQFT, questions such as that for the justification of the particle picture arise naturally in subsequent approximations when BEs are to be derived. This specific problem is particularly important in the case of resonant leptogenesis where the relevant particle states are almost degenerate in mass. It is found that Boltzmann like equations can (only) be obtained in certain cases. But it is then possible to account for corrections due to quantum and medium effects.

  15. Multicomponent fractional quantum Hall effect in graphene

    NASA Astrophysics Data System (ADS)

    Dean, C. R.; Young, A. F.; Cadden-Zimansky, P.; Wang, L.; Ren, H.; Watanabe, K.; Taniguchi, T.; Kim, P.; Hone, J.; Shepard, K. L.

    2011-09-01

    The fractional quantum Hall effect (FQHE) in an electron gas with multiple internal degrees of freedom provides a model system to study the interplay between symmetry breaking and emergent topological order. In graphene, the structure of the honeycomb lattice endows the electron wavefunctions with an additional quantum number, termed valley isospin, which, combined with the usual electron spin, yields four-fold degenerate Landau levels (LLs; refs , ). This additional symmetry modifies the FQHE and is conjectured to produce new incompressible ground states in graphene. Here we report multiterminal measurements of the FQHE in high-mobility graphene devices fabricated on hexagonal boron nitride substrates. The measured energy gaps are large, particularly in the second Landau level, where they are up to 10 times larger than those reported in the cleanest conventional systems. In the lowest Landau level the hierarchy of FQH states reflects the additional valley degeneracy.

  16. A recoil resilient lumen support, design, fabrication and mechanical evaluation

    NASA Astrophysics Data System (ADS)

    Mehdizadeh, Arash; Ali, Mohamed Sultan Mohamed; Takahata, Kenichi; Al-Sarawi, Said; Abbott, Derek

    2013-06-01

    Stents are artificial implants that provide scaffolding to a cavity inside the body. This paper presents a new luminal device for reducing the mechanical failure of stents due to recoil, which is one of the most important issues in stenting. This device, which we call a recoil-resilient ring (RRR), is utilized standalone or potentially integrated with existing stents to address the problem of recoil. The proposed structure aims to minimize the need for high-pressure overexpansion that can induce intra-luminal trauma and excess growth of vascular tissue causing later restenosis. The RRR is an overlapped open ring with asymmetrical sawtooth structures that are intermeshed. These teeth can slide on top of each other, while the ring is radially expanded, but interlock step-by-step so as to keep the final expanded state against compressional forces that normally cause recoil. The RRRs thus deliver balloon expandability and, when integrated with a stent, bring both radial rigidity and longitudinal flexibility to the stent. The design of the RRR is investigated through finite element analysis (FEA), and then the devices are fabricated using micro-electro-discharge machining of 200-m-thick Nitinol sheet. The standalone RRR is balloon expandable in vitro by 5-7 Atm in pressure, which is well within the recommended in vivo pressure ranges for stenting procedures. FEA compression tests indicate 13 less reduction of the cross-sectional area of the RRR compared with a typical stainless steel stent. These results also show perfect elastic recovery of the RRR after removal of the pressure compared to the remaining plastic deformations of the stainless steel stent. On the other hand, experimental loading tests show that the fabricated RRRs have 2.8 radial stiffness compared to a two-column section of a commercial stent while exhibiting comparable elastic recovery. Furthermore, testing of in vitro expansion in a mock artery tube shows around 2.9% recoil, approximately 5-11 smaller than the recoil reported for commercial stents. These experimental results demonstrate the effectiveness of the device design for the targeted luminal support and stenting applications.

  17. Excitons in the Fractional Quantum Hall Effect

    DOE R&D Accomplishments Database

    Laughlin, R. B.

    1984-09-01

    Quasiparticles of charge 1/m in the Fractional Quantum Hall Effect form excitons, which are collective excitations physically similar to the transverse magnetoplasma oscillations of a Wigner crystal. A variational exciton wavefunction which shows explicitly that the magnetic length is effectively longer for quasiparticles than for electrons is proposed. This wavefunction is used to estimate the dispersion relation of these excitons and the matrix elements to generate them optically out of the ground state. These quantities are then used to describe a type of nonlinear conductivity which may occur in these systems when they are relatively clean.

  18. Nontrivial quantum and quantum-like effects in biosystems: Unsolved questions and paradoxes.

    PubMed

    Melkikh, Alexey V; Khrennikov, Andrei

    2015-11-01

    Non-trivial quantum effects in biological systems are analyzed. Some unresolved issues and paradoxes related to quantum effects (Levinthal's paradox, the paradox of speed, and mechanisms of evolution) are addressed. It is concluded that the existence of non-trivial quantum effects is necessary for the functioning of living systems. In particular, it is demonstrated that classical mechanics cannot explain the stable work of the cell and any over-cell structures. The need for quantum effects is generated also by combinatorial problems of evolution. Their solution requires a priori information about the states of the evolving system, but within the framework of the classical theory it is not possible to explain mechanisms of its storage consistently. We also present essentials of so called quantum-like paradigm: sufficiently complex bio-systems process information by violating the laws of classical probability and information theory. Therefore the mathematical apparatus of quantum theory may have fruitful applications to describe behavior of bio-systems: from cells to brains, ecosystems and social systems. In quantum-like information biology it is not presumed that quantum information bio-processing is resulted from quantum physical processes in living organisms. Special experiments to test the role of quantum mechanics in living systems are suggested. This requires a detailed study of living systems on the level of individual atoms and molecules. Such monitoring of living systems in vivo can allow the identification of the real potentials of interaction between biologically important molecules. PMID:26160644

  19. Quantum Spin Hall Effect and Topological Phase Transition in HgTe Quantum Wells

    SciTech Connect

    Bernevig, A.

    2010-03-02

    We show that the quantum spin Hall (QSH) effect, a state of matter with topological properties distinct from those of conventional insulators, can be realized in mercury telluride-cadmium telluride semiconductor quantum wells. When the thickness of the quantum well is varied, the electronic state changes from a normal to an 'inverted' type at a critical thickness d{sub c}. We show that this transition is a topological quantum phase transition between a conventional insulating phase and a phase exhibiting the QSH effect with a single pair of helical edge states. We also discuss methods for experimental detection of the QSH effect.

  20. Magnetic field and quantum screening effects on the occurrence time advance in quantum magnetoplasmas

    SciTech Connect

    Ki, Dae-Han; Jung, Young-Dae

    2011-07-15

    The magnetic field and quantum screening effects on the occurrence scattering time advance for the electron-ion collision are investigated in quantum magnetoplasmas. The result shows that the occurrence scattering time advance decreases with an increase of the magnetic-field strength. It is also found that the occurrence time advance decreases with increasing projectile energy and increases with increasing scattering angle. In addition, the occurrence time advance decreases with an increase of the quantum effect, i.e., Fermi wavelength.

  1. Anatomy of the Binary Black Hole Recoil: A Multipolar Analysis

    NASA Technical Reports Server (NTRS)

    Schnittman, Jeremy; Buonanno, Alessandra; vanMeter, James R.; Baker, John G.; Boggs, William D.; Centrella, Joan; Kelly, Bernard J.; McWilliams, Sean T.

    2007-01-01

    We present a multipolar analysis of the recoil velocity computed in recent numerical simulations of binary black hole coalescence, for both unequal masses and non-zero, non-precessing spins. We show that multipole moments up to and including 1 = 4 are sufficient to accurately reproduce the final recoil velocity (= 98%) and that only a few dominant modes contribute significantly to it (2 95%). We describe how the relative amplitude, and more importantly, the relative phase, of these few modes control the way in which the recoil builds up throughout the inspiral, merger, and ring-down phases. We also find that the numerical results can be reproduced, to a high level of accuracy, by an effective Newtonian formula for the multipole moments obtained by replacing in the Newtonian formula the radial separation with an effective radius computed from the numerical data. Beyond the merger, the numerical results are reproduced by a superposition of three Kerr quasi-normal modes. Analytic formulae, obtained by expressing the multipole moments in terms of the fundamental QNMs of a Kerr BH, are able to explain the onset and amount of '.anti-kick" for each of the simulations. Lastly, we apply this multipolar analysis to understand the remarkable difference between the amplitudes of planar and non-planar kicks for equal-mass spinning black holes.

  2. Recoiling from a Kick in the Head-On Case

    NASA Technical Reports Server (NTRS)

    Choi, Dae-Il; Kelly, Bernard J.; Boggs, William D.; Baker, John G.; Centrella, Joan; Van Meter, James

    2007-01-01

    Recoil "kicks" induced by gravitational radiation are expected in the inspiral and merger of black holes. Recently the numerical relativity community has begun to measure the significant kicks found when both unequal masses and spins are considered. Because understanding the cause and magnitude of each component of this kick may be complicated in inspiral simulations, we consider these effects in the context of a simple test problem. We study recoils from collisions of binaries with initially head-on trajectories, starting with the simplest case of equal masses with no spin; adding spin and varying the mass ratio, both separately and jointly. We find spin-induced recoils to be significant even in head-on configurations. Additionally, it appears that the scaling of transverse kicks with spins is consistent with post-Newtonian (PN) theory, even though the kick is generated in the nonlinear merger interaction, where PN theory should not apply. This suggests that a simple heuristic description might be effective in the estimation of spin-kicks.

  3. Cosmic fluctuations from a quantum effective action

    NASA Astrophysics Data System (ADS)

    Wetterich, C.

    2015-10-01

    Does the observable spectrum of cosmic fluctuations depend on detailed initial conditions? This addresses the question if the general inflationary paradigm is sufficient to predict within a given model the spectrum and amplitude of cosmic fluctuations, or if additional particular assumptions about the initial conditions are needed. The answer depends on the number of e -foldings Nin between the beginning of inflation and horizon crossing of the observable fluctuations. We discuss an interacting inflaton field in an arbitrary homogeneous and isotropic geometry, employing the quantum effective action ? . An exact time evolution equation for the correlation function involves the second functional derivative ?(2 ) . The operator formalism and quantum vacua for interacting fields are not needed. Use of the effective action also allows one to address the change of frames by field transformations (field relativity). Within the approximation of a derivative expansion for the effective action we find the most general solution for the correlation function, including mixed quantum states. For not too large Nin the memory of the initial conditions is preserved. In this case the cosmic microwave background cannot disentangle between the initial spectrum and its processing at horizon crossing. The inflaton potential cannot be reconstructed without assumptions about the initial state of the universe. We argue that for very large Nin a universal scaling form of the correlation function is reached for the range of observable modes. This can be due to symmetrization and equilibration effects, not yet contained in our approximation, which drive the short distance tail of the correlation function toward the Lorentz invariant propagator in flat space.

  4. A Double Scattering Analytical Model For Elastic Recoil Detection Analysis

    SciTech Connect

    Barradas, N. P.; Lorenz, K.; Alves, E.; Darakchieva, V.

    2011-06-01

    We present an analytical model for calculation of double scattering in elastic recoil detection measurements. Only events involving the beam particle and the recoil are considered, i.e. 1) an ion scatters off a target element and then produces a recoil, and 2) an ion produces a recoil which then scatters off a target element. Events involving intermediate recoils are not considered, i.e. when the primary ion produces a recoil which then produces a second recoil. If the recoil element is also present in the stopping foil, recoil events in the stopping foil are also calculated. We included the model in the standard code for IBA data analysis NDF, and applied it to the measurement of hydrogen in Si.

  5. The effect of measurements, randomly distributed in time, on quantum systems: stochastic quantum Zeno effect

    NASA Astrophysics Data System (ADS)

    Shushin, A. I.

    2011-02-01

    The manifestation of measurements, randomly distributed in time, on the evolution of quantum systems are analyzed in detail. The set of randomly distributed measurements (RDM) is modeled within the renewal theory, in which the distribution is characterized by the probability density function (PDF) W(t) of times t between successive events (measurements). The evolution of the quantum system affected by the RDM is shown to be described by the density matrix satisfying the stochastic Liouville equation. This equation is applied to the analysis of the RDM effect on the evolution of a two-level system for different types of RDM statistics, corresponding to different PDFs W(t). Obtained general results are illustrated as applied to the cases of the Poissonian (W(t) \\sim \\,e^{-w_r t}) and anomalous (W(t) ~ 1/t1 + α, α <= 1) RDM statistics. In particular, specific features of the quantum and inverse Zeno effects, resulting from the RDM, are thoroughly discussed.

  6. Using the quantum Zeno effect for suppression of decoherence

    NASA Astrophysics Data System (ADS)

    Kondo, Yasushi; Matsuzaki, Yuichiro; Matsushima, Kei; Filgueiras, Jefferson G.

    2016-01-01

    Projective measurements are an essential element of quantum mechanics. In most cases, they cause an irreversible change of the quantum system on which they act. However, measurements can also be used to stabilize quantum states from decay processes, which is known as the quantum Zeno effect (QZE). Here, we demonstrate this effect for the case of a superposition state of a nuclear spin qubit, using an ancilla to perform the measurement. As a result, the quantum state of the qubit is protected against dephasing without relying on an ensemble nature of NMR experiments. We also propose a scheme to protect an arbitrary state by using QZE.

  7. The quantum Zeno effect and quantum feedback in cavity QED

    NASA Astrophysics Data System (ADS)

    Dotsenko, I.; Bernu, J.; Deléglise, S.; Sayrin, C.; Brune, M.; Raimond, J.-M.; Haroche, S.; Mirrahimi, M.; Rouchon, P.

    2010-09-01

    We explore experimentally the fundamental projective properties of a quantum measurement and their application in the control of a system's evolution. We perform quantum non-demolition (QND) photon counting on a microwave field trapped in a very-high-Q superconducting cavity, employing circular Rydberg atoms as non-absorbing probes of light. By repeated measurement of the cavity field we demonstrated the freeze of its initially coherent evolution, illustrating the back action of the photon number measurement on the field's phase. On the contrary, by utilizing a weak QND measurement in combination with the control injection of coherent pulses, we plan to force the field to deterministically evolve towards any target photon-number state. This quantum feedback procedure will enable us to prepare and protect photon-number states against decoherence.

  8. Background charges and quantum effects in quantum dots transport spectroscopy

    NASA Astrophysics Data System (ADS)

    Pierre, M.; Hofheinz, M.; Jehl, X.; Sanquer, M.; Molas, G.; Vinet, M.; Deleonibus, S.

    2009-08-01

    We extend a simple model of a charge trap coupled to a single-electron box to energy ranges and parameters such that it gives new insights and predictions readily observable in many experimental systems. We show that a single background charge is enough to give lines of differential conductance in the stability diagram of the quantum dot, even within undistorted Coulomb diamonds. It also suppresses the current near degeneracy of the impurity charge, and yields negative differential lines far from this degeneracy. We compare this picture to two other accepted explanations for lines in diamonds, based respectively on the excitation spectrum of a quantum dot and on fluctuations of the density-of-states in the contacts. In order to discriminate between these models, we emphasize the specific features related to environmental charge traps. Finally we show that our model accounts very well for all the anomalous features observed in silicon nanowire quantum dots.

  9. Engineering of perturbation effects in onion-like heteronanocrystal quantum dot-quantum well

    NASA Astrophysics Data System (ADS)

    SalmanOgli, A.; Rostami, R.

    2013-10-01

    In this article, the perturbation influences on optical characterization of quantum dot and quantum dot-quantum well (modified quantum dot) heteronanocrystal is investigated. The original aim of this article is to investigate the quantum dot-quantum well heteronanocrystal advantages and disadvantages, when used as a functionalized particle in biomedical applications. Therefore, all of the critical features of quantum dots are fundamentally studied and their influences on optical properties are simulated. For the first time, the perturbation effects on optical characteristics are observed in the quantum dot-quantum well heteronanocrystals by 8-band K.P theory. The impact of perturbation on optical features such as photoluminescence and shifting of wavelength is studied. The photoluminescence and operation wavelength of quantum dots play a vital role in biomedical applications, where their absorption and emission in biological assays are altered by shifting of wavelength. Furthermore, in biomedical applications, by tuning the emission wavelengths of the quantum dot into far-red and near-infrared ranges, non-invasive in-vivo imaging techniques have been easily developed. In this wavelength window, tissue absorption, scattering and auto-fluorescence intensities have minimum quantities; thus fixing or minimizing of wavelength shifting can be regarded as an important goal which is investigated in this work.

  10. Investigation on modeling and controability of a magnetorheological gun recoil damper

    NASA Astrophysics Data System (ADS)

    Hu, Hongsheng; Wang, Juan; Wang, Jiong; Qian, Suxiang; Li, Yancheng

    2009-07-01

    Magnetorheological (MR) fluid as a new smart material has done well in the vibration and impact control engineering fields because of its good electromechanical coupling characteristics, preferable dynamic performance and higher sensitivity. And success of MRF has been apparent in many engineering applied fields, such as semi-active suspension, civil engineering, etc. So far, little research has been done about MR damper applied into the weapon system. Its primary purpose of this study is to identify its dynamic performance and controability of the artillery recoil mechanism equipped with MR damper. Firstly, based on the traditional artillery recoil mechanism, a recoil dynamic model is developed in order to obtain an ideal rule between recoil force and its stroke. Then, its effects of recoil resistance on the stability and firing accuracy of artillery are explored. Because MR gun recoil damper under high impact load shows a typical nonlinear character and there exists a shear-thinning phenomenon, to establish an accurate dynamic model has been a seeking aim of its design and application for MR damper under high impact load. Secondly, in this paper, considering its actual bearing load, an inertia factor was introduced to Herschel-Bulkley model, and some factor's effect on damping force are simulated and analyzed by using numerical simulation, including its dynamic performance under different flow coefficients and input currents. Finally, both of tests with the fixed current and different On-Off control algorithms have been done to confirm its controability of MR gun recoil damper under high impact load. Experimental results show its dynamic performances of the large-scale single-ended MR gun recoil damper can be changed by altering the applied currents and it has a good controllability.

  11. Effect of noise on quantum teleportation

    SciTech Connect

    Kumar, Deepak; Pandey, P. N.

    2003-07-01

    The effect of noise on quantum teleportation of a spin-(1/2) state using an entangled pair is studied. We calculate the time evolution of the density matrix of the three involved particles due to their coupling with the environmental degrees of freedom. We evaluate the fidelity of transmission as a function of time under a variety of conditions and compare the fidelities obtained for different entangled states. We find that for a generic coupling to environment, use of the singlet state for the entangled pair yields the highest fidelity in noisy conditions.

  12. Quantum Rotational Effects in Nanomagnetic Systems

    NASA Astrophysics Data System (ADS)

    O'Keeffe, Michael F.

    Quantum tunneling of the magnetic moment in a nanomagnet must conserve the total angular momentum. For a nanomagnet embedded in a rigid body, reversal of the magnetic moment will cause the body to rotate as a whole. When embedded in an elastic environment, tunneling of the magnetic moment will cause local elastic twists of the crystal structure. In this thesis, I will present a theoretical study of the interplay between magnetization and rotations in a variety of nanomagnetic systems which have some degree of rotational freedom. We investigate the effect of rotational freedom on the tunnel splitting of a nanomagnet which is free to rotate about its easy axis. Calculating the exact instanton of the coupled equations of motion shows that mechanical freedom of the particle renormalizes the easy axis anisotropy, increasing the tunnel splitting. To understand magnetization dynamics in free particles, we study a quantum mechanical model of a tunneling spin embedded in a rigid rotor. The exact energy levels for a symmetric rotor exhibit first and second order quantum phase transitions between states with different values the magnetic moment. A quantum phase diagram is obtained in which the magnetic moment depends strongly on the moments of inertia. An intrinsic contribution to decoherence of current oscillations of a flux qubit must come from the angular momentum it transfers to the surrounding body. Within exactly solvable models of a qubit embedded in a rigid body and an elastic medium, we show that slow decoherence is permitted if the solid is macroscopically large. The spin-boson model is one of the simplest representations of a two-level system interacting with a quantum harmonic oscillator, yet has eluded a closed-form solution. I investigate some possible approaches to understanding its spectrum. The Landau-Zener dynamics of a tunneling spin coupled to a torsional resonator show that for certain parameter ranges the system exhibits multiple Landau-Zener transitions. These transitions coincide in time with changes in the oscillator dynamics. A large number of spins on a single oscillator coupled only through the in-phase oscillations behaves as a single large spin, greatly enhancing the spin-phonon coupling.

  13. Quantum spring from the Casimir effect

    NASA Astrophysics Data System (ADS)

    Feng, Chao-Jun; Li, Xin-Zhou

    2010-07-01

    The Casimir effect arises not only in the presence of material boundaries but also in space with nontrivial topology. In this Letter, we choose a topology of the flat (D + 1)-dimensional spacetime, which causes the helix boundary condition for a Hermitian massless scalar field. Especially, Casimir effect for a massless scalar field on the helix boundary condition is investigated in two and three dimensions by using the zeta function techniques. The Casimir force parallel to the axis of the helix behaves very much like the force on a spring that obeys the Hooke's law when the ratio r of the pitch to the circumference of the helix is small, but in this case, the force comes from a quantum effect, so we would like to call it quantum spring. When r is large, this force behaves like the Newton's law of universal gravitation in the leading order. On the other hand, the force perpendicular to the axis decreases monotonously with the increasing of the ratio r. Both forces are attractive and their behaviors are the same in two and three dimensions.

  14. Composite fermion observation in quantum Hall effect

    NASA Astrophysics Data System (ADS)

    Shrivastava, Keshav

    2004-03-01

    The composite fermion model (CF) applicable to quantum Hall effect has been examined[1] and found to be internally inconsistent. Therefore, the claim of observing it in the experiment[2] has also been examined. What is observed in the data is the spin symmetry and the flux quantization but it is claimed that CFs are observed. It is further claimed by Willett et al that geometric resonance of the CF agrees with the data. Actually, the observation is related to flux quantization but not to CF. The attachment of "flux to charge", has not been found. Indeed the CF is unphysical because it uses flux without current. Therefore, the paper of Willett et al should be retracted. According to the theory[3] of angular momentum, we find that the effective charge is given by [L+(1/2)(+-)S]/(2L+1)=1/2 for L=0, S=0. A two particle state with s_1=+1/2, s_2=-1/2 gives the half filling. All of the predicted fractions agree with the data. [1] K. N. Shrivastava, Bull. Am. Phys. Soc. 48,529(2003). [2] R. L. Willett et al Phys. Rev. Lett.83,2624(1999). [3] K. N. Shrivastava, Introduction to quantum Hall effect, Nova Science, N. Y. 2002.

  15. Jet extinction from nonperturbative quantum gravity effects

    NASA Astrophysics Data System (ADS)

    Kilic, Can; Lath, Amitabh; Rose, Keith; Thomas, Scott

    2014-01-01

    The infrared-ultraviolet properties of quantum gravity suggest on very general grounds that hard short distance scattering processes are highly suppressed for center of mass scattering energies beyond the fundamental Planck scale. If this scale is not too far above the electroweak scale, these nonperturbative quantum gravity effects could be manifest as an extinction of high transverse momentum jets at the LHC. To model these effects, we implement an extinction Monte Carlo modification of the PYTHIA event generator based on a Veneziano form factor with a large absorptive branch cut modification of hard QCD scattering processes. Using this we illustrate the leading effects of extinction on the inclusive jet transverse momentum spectrum at the LHC. We estimate that an extinction mass scale of up to roughly half the center of mass beam collision energy could be probed with high statistics data. Experimental searches at the LHC for jet extinction would be complementary to ongoing searches for the related phenomenon of excess production of high multiplicity final states.

  16. Incoherent tunneling effects in a one-dimensional quantum walk

    NASA Astrophysics Data System (ADS)

    Annabestani, Mostafa; Javad Akhtarshenas, Seyed; Abolhassani, Mohamad Reza

    2016-03-01

    In this article we investigate the effects of shifting position decoherence, arising from the incoherent tunneling effect in the experimental realization of the quantum walk, on the one-dimensional discrete time quantum walk. We show that in the regime of this type of noise the quantum behavior of the walker does not vanish, in contrast to the coin decoherence for which the walker undergoes a quantum-to-classical transition even for weak noise. In particular, we show that the quadratic dependence of the variance on the time and also the coin–position entanglement, i.e. two important quantum aspects of the coherent quantum walk, are preserved in the presence of tunneling decoherence. Furthermore, we present an explicit expression for the probability distribution of the decoherent one-dimensional quantum walk in terms of the corresponding coherent probabilities, and show that this type of decoherence smooths the probability distribution.

  17. Extinction properties of metallic nanowires: Quantum diffraction and retardation effects

    NASA Astrophysics Data System (ADS)

    Moradi, Afshin

    2015-10-01

    The standard Mie theory for the extinction of electromagnetic radiation by a metal cylinder that is irradiated by a normally incident plane wave is extended to the case of a metallic nanowire, where two quantum longitudinal waves are excited. The modification of the Mie theory due to quantum diffraction effects is included by employing the quantum hydrodynamic approximation and applying the appropriate quantum additional boundary conditions. The extinction properties of the system and their differences with previous treatments based on the standard local and nonlocal models are shown. Also, as an example the validity of the nonretarded approximation in the quantum nonlocal optical response of a sodium nanowire is discussed.

  18. Non-Markovian effect on the quantum discord

    SciTech Connect

    Wang Bo; Xu Zhenyu; Chen Zeqian; Feng Mang

    2010-01-15

    We study the non-Markovian effect on the dynamics of the quantum discord by exactly solving a model consisting of two independent qubits subject to two zero-temperature non-Markovian reservoirs, respectively. Considering the two qubits initially prepared in Bell-like or extended Werner-like states, we show that there is no occurrence of the sudden death, but only instantaneous disappearance of the quantum discord at some time points, in comparison to the entanglement sudden death in the same range of the parameters of interest. This implies that the quantum discord is more useful than the entanglement to describe the quantum correlation involved in quantum systems.

  19. A quantum probability account of order effects in inference.

    PubMed

    Trueblood, Jennifer S; Busemeyer, Jerome R

    2011-01-01

    Order of information plays a crucial role in the process of updating beliefs across time. In fact, the presence of order effects makes a classical or Bayesian approach to inference difficult. As a result, the existing models of inference, such as the belief-adjustment model, merely provide an ad hoc explanation for these effects. We postulate a quantum inference model for order effects based on the axiomatic principles of quantum probability theory. The quantum inference model explains order effects by transforming a state vector with different sequences of operators for different orderings of information. We demonstrate this process by fitting the quantum model to data collected in a medical diagnostic task and a jury decision-making task. To further test the quantum inference model, a new jury decision-making experiment is developed. Using the results of this experiment, we compare the quantum inference model with two versions of the belief-adjustment model, the adding model and the averaging model. We show that both the quantum model and the adding model provide good fits to the data. To distinguish the quantum model from the adding model, we develop a new experiment involving extreme evidence. The results from this new experiment suggest that the adding model faces limitations when accounting for tasks involving extreme evidence, whereas the quantum inference model does not. Ultimately, we argue that the quantum model provides a more coherent account for order effects that was not possible before. PMID:21951058

  20. Quantum dissipative effect of one dimension coupled anharmonic oscillator

    SciTech Connect

    Sulaiman, A.; Zen, Freddy P.

    2015-04-16

    Quantum dissipative effect of one dimension coupled anharmonic oscillator is investigated. The systems are two coupled harmonic oscillator with the different masses. The dissipative effect is studied based on the quantum state diffusion formalism. The result show that the anharmonic effect increase the amplitude but the lifetime of the oscillation depend on the damping coefficient and do not depend on the temperature.

  1. Quantum toys for quantum computing: persistent currents controlled by the spin Josephson effect.

    PubMed

    Tatara, Gen; Garcia, N

    2003-08-15

    Quantum devices and computers will need operational units in different architectural configurations for their functioning. The unit should be a simple "quantum toy," an easy to handle superposition state. Here such a novel unit of quantum mechanical flux state (or persistent current) in a conducting ring with three ferromagnetic quantum dots is presented. The state is labeled by the two directions of the persistent current, which is driven by the spin chirality of the dots, and is controlled by the spin (the spin Josephson effect). It is demonstrated that by the use of two connected rings, one can carry out unitary transformations on the input flux state by controlling one spin in one of the rings, enabling us to prepare superposition states. The flux is shown to be a quantum operation gate, and may be useful in quantum computing. PMID:12935044

  2. Covariant effective action for loop quantum cosmology a la Palatini

    SciTech Connect

    Olmo, Gonzalo J.; Singh, Parampreet E-mail: psingh@perimeterinstitute.ca

    2009-01-15

    In loop quantum cosmology, non-perturbative quantum gravity effects lead to the resolution of the big bang singularity by a quantum bounce without introducing any new degrees of freedom. Though fundamentally discrete, the theory admits a continuum description in terms of an effective Hamiltonian. Here we provide an algorithm to obtain the corresponding effective action, establishing in this way the covariance of the theory for the first time. This result provides new insights on the continuum properties of the discrete structure of quantum geometry and opens new avenues to extract physical predictions such as those related to gauge invariant cosmological perturbations.

  3. Quantum Hall effect in (cadmium flouride)-based nanostructures

    SciTech Connect

    Bagraev, N. T. Gimbitskaya, O. N.; Klyachkin, L. E.; Malyarenko, A. M.; Shelykh, I. A.; Ryskin, A. I.; Shcheulin, A. S.

    2009-01-15

    Shubnikov-de Haas oscillations and a ladder of quantum steps in the Hall resistance were observed in a p-CdF{sub 2} quantum well confined by {delta}-like barriers for CdB{sub x}F{sub 2-x} on the surface of n-CdF{sub 2}. Due to the small effective mass of two-dimensional holes, observation of the quantum Hall effect became possible at room temperature.

  4. Guiding effect of quantum wells in semiconductor lasers

    SciTech Connect

    Aleshkin, V Ya; Dikareva, Natalia V; Dubinov, A A; Zvonkov, B N; Karzanova, Maria V; Kudryavtsev, K E; Nekorkin, S M; Yablonskii, A N

    2013-05-31

    The guiding effect of InGaAs quantum wells in GaAs- and InP-based semiconductor lasers has been studied theoretically and experimentally. The results demonstrate that such waveguides can be effectively used in laser structures with a large refractive index difference between the quantum well material and semiconductor matrix and a large number of quantum wells (e.g. in InP-based structures). (semiconductor lasers. physics and technology)

  5. Fractional quantum Hall effect in optical lattices

    SciTech Connect

    Hafezi, M.; Demler, E.; Lukin, M. D.; Soerensen, A. S.

    2007-08-15

    We analyze a recently proposed method to create fractional quantum Hall (FQH) states of atoms confined in optical lattices [A. Soerensen et al., Phys. Rev. Lett. 94, 086803 (2005)]. Extending the previous work, we investigate conditions under which the FQH effect can be achieved for bosons on a lattice with an effective magnetic field and finite on-site interaction. Furthermore, we characterize the ground state in such systems by calculating Chern numbers which can provide direct signatures of topological order and explore regimes where the characterization in terms of wave-function overlap fails. We also discuss various issues which are relevant for the practical realization of such FQH states with ultracold atoms in an optical lattice, including the presence of a long-range dipole interaction which can improve the energy gap and stabilize the ground state. We also investigate a detection technique based on Bragg spectroscopy to probe these systems in an experimental realization.

  6. Fractional Quantum Hall Effect from Phenomenological Bosonization

    NASA Astrophysics Data System (ADS)

    Zyuzin, Vladimir

    2013-03-01

    In this work we propose a model of the fractional quantum Hall effect within conventional one-dimensional bosonization. It is shown that in this formalism the resulting bosonized fermion operator corresponding to momenta of Landau gauge wave function is effectively two-dimensional. At special filling factors the bulk gets gapped, and the theory is described by a sine-Gordon model. The edges are shown to be gapless, chiral, and carrying a fractional charge. The hierarchy of obtained fractional charges is consistent with existing experiments and theories. It is also possible to draw a connection to composite fermion description and to the Laughlin many-body wave function. ARO grant W911NF-09-1-0527 and NSF grant DMR-0955778.

  7. GENERAL: Preservation of quantum states via a super-Zeno effect on ensemble quantum computers

    NASA Astrophysics Data System (ADS)

    Ren, Ting-Ting; Luo, Jun; Sun, Xian-Ping; Zhan, Ming-Sheng

    2009-11-01

    Following a recent proposal by Dhar et al (2006 Phys. Rev. Lett. 96 100405), we demonstrate experimentally the preservation of quantum states in a two-qubit system based on a super-Zeno effect using liquid-state nuclear magnetic resonance techniques. Using inverting radiofrequency pulses and delicately selecting time intervals between two pulses, we suppress the effect of decoherence of quantum states. We observe that preservation of the quantum state |11rangle with the super-Zeno effect is three times more efficient than the ordinary one with the standard Zeno effect.

  8. Anomalous nuclear quantum effects in ice

    NASA Astrophysics Data System (ADS)

    Pamuk, Betl; Soler, Jose M.; Allen, Philip B.; Fernndez-Serra, Marivi

    2012-02-01

    The lattice parameters of light (H2O) and heavy (D2O) Ih ice at 10 K differ by 0.09%.[1] The larger lattice constant is that of the heavier isotope. This isotope shift with anomalous sign is linked to the zero point point energy of phonons in ice. To determine the origin of this anomaly, we use ab initio density functional theory to compute the free energy of ice within the quasiharmonic approximation. As expected, the frozen lattice constant at T = 0 K is smaller than the quantum lattice constant, independent of the isotopic substitution. We find that, the heavy isotope D gives more zero point expansion than H, whereas the heavy isotope ^18O gives normal zero point expansion, i.e smaller than ^16O. Relative to the the classical result, the net effect of quantum nuclei (H and O) on volume has the conventional (positive) sign at T = 0 but it becomes negative above 70 K, indicating that it may be also relevant for liquid water. These results are not reproduced by state of art polarizable empirical potentials.[2] [1] B. K. R"ottger et. al., Acta Cryst. B 50, 644-648 (1994). [2] C. P. Herrero and R. Ram'irez, J. Chem. Phys. 134, 094510 (2011).

  9. Proton recoil scintillator neutron rem meter

    DOEpatents

    Olsher, Richard H. (Los Alamos, NM); Seagraves, David T. (Los Alamos, NM)

    2003-01-01

    A neutron rem meter utilizing proton recoil and thermal neutron scintillators to provide neutron detection and dose measurement. In using both fast scintillators and a thermal neutron scintillator the meter provides a wide range of sensitivity, uniform directional response, and uniform dose response. The scintillators output light to a photomultiplier tube that produces an electrical signal to an external neutron counter.

  10. Quantum confinement effects in CdSe quantum dots

    SciTech Connect

    Zorman, B.; Friesner, R.A.; Ramakrishna, M.V.

    1995-05-11

    The energies of the lowest excited state of hexagonal and zinc-blende CdSe spherical quantum dots are calculated using empirical pseudopotentials of the bulk semiconductor. The lowest excited state energies computed for hexagonal clusters are in reasonable agreement with recent experiments. We predict that zinc-blende and hexagonal dots have nearly the same lowest exciton energy shifts down to very small dot sizes. We have found that small changes in the pseudopotentials can turn the lowest energy transitions of small particles into indirect gaps. 29 refs., 6 figs.

  11. Destruction of the Fractional Quantum Hall Effect by Disorder

    DOE R&D Accomplishments Database

    Laughlin, R. B.

    1985-07-01

    It is suggested that Hall steps in the fractional quantum Hall effect are physically similar to those in the ordinary quantum Hall effect. This proposition leads to a simple scaling diagram containing a new type of fixed point, which is identified with the destruction of the fractional states by disorder. 15 refs., 3 figs.

  12. Recoil-proton polarization in high-energy deuteron photodisintegration with circularly plarized photons.

    SciTech Connect

    Jiang, X.; Arrington, J.; Benmokhtar, F.; Camsonne, A.; Chen, J. P.; Holt, R. J.; Qattan, I. A.; Reimer, P. E.; Schulte, E. C.; Wijesooriya, K.; Physics; Rutgers Univ.; Univ. Blaise Pascal; Thomas Jefferson National Accelerator Facility

    2007-05-01

    We measured the angular dependence of the three recoil-proton polarization components in two-body photodisintegration of the deuteron at a photon energy of 2 GeV. These new data provide a benchmark for calculations based on quantum chromodynamics. Two of the five existing models have made predictions of polarization observables. Both explain the longitudinal polarization transfer satisfactorily. Transverse polarizations are not well described, but suggest isovector dominance.

  13. Recoil-Proton Polarization in High-Energy Deuteron Photodisintegration with Circularly Polarized Photons

    SciTech Connect

    Jiang, X.; Benmokhtar, F.; Glashauser, C.; McCormick, K.; Ransome, R. D.; Arrington, J.; Holt, R. J.; Reimer, P. E.; Schulte, E. C.; Wijesooriya, K.; Camsonne, A.

    2007-05-04

    We measured the angular dependence of the three recoil-proton polarization components in two-body photodisintegration of the deuteron at a photon energy of 2 GeV. These new data provide a benchmark for calculations based on quantum chromodynamics. Two of the five existing models have made predictions of polarization observables. Both explain the longitudinal polarization transfer satisfactorily. Transverse polarizations are not well described, but suggest isovector dominance.

  14. Recoil-Proton Polarization in High-Energy Deuteron Photodisintegration with Circularly Polarized Photons

    SciTech Connect

    X. Jiang; J. Arrington; F. Benmokhtar; A. Camsonne; J. P. Chen; S. Choi; E. Chudakov; F. Cusanno; A. Deur; D. Dutta; F. Garibaldi; D. Gaskell; O. Gayou; R. Gilman; C. Glashauser; D. Hamilton; O. Hansen; D. W. Higinbotham; R. J. Holt; C. W. de Jager; M. K. Jones; L. J. Kaufman; E. R. Kinney; K. Kramer; L. Lagamba; R. de Leo; J. Lerose; D. Lhuillier; R. Lindgren; N. Liyanage; K. McCormick; Z.-E. Meziani; R. Michaels; B. Mof?t; P. Monaghan; S. Nanda; K. D. Paschke; C. F. Perdrisat; V. Punjabi; I. A. Qattan; R. D. Ransome; P. E. Reimer; B. Reitz; A. Saha; E. C. Schulte; R. Sheyor; K. Slifer; P. Solvignon; V. Sulkosky; G. M. Urciuoli; E. Voutier; K. Wang; K. Wijesooriya; B. Wojtsekhowski; and L. Zhu

    2007-05-01

    We measured the angular dependence of the three recoil-proton polarization components in two-body photodisintegration of the deuteron at a photon energy of 2 GeV. These new data provide a benchmark for calculations based on quantum chromodynamics. Two of the five existing models have made predictions of polarization observables. Both explain the longitudinal polarization transfer satisfactorily. Transverse polarizations are not well described, but suggest isovector dominance.

  15. Angular dependence of recoil proton polarization in high-energy \\gamma d \\to p n

    SciTech Connect

    X. Jiang; J. Arrington; F. Benmokhtar; A. Camsonne; J.P. Chen; S. Choi; E. Chudakov; F. Cusanno; A. Deur; D. Dutta; F. Garibaldi; D. Gaskell; O. Gayou; R. Gilman; C. Glashauser; D. Hamilton; O. Hansen; D.W. Higinbotham; R.J. Holt; C.W. de Jager; M.K. Jones; L.J. Kaufman; E.R. Kinney; K. Kramer; L. Lagamba; R. de Leo; J. Lerose; D. Lhuillier; R. Lindgren; N. Liyanage; K. McCormick; Z.-E. Meziani; R. Michaels; B. Moffit; P. Monaghan; S. Nanda; K.D. Paschke; C.F. Perdrisat; V. Punjabi; I.A. Qattan; R.D. Ransome; P.E. Reimer; B. Reitz; A. Saha; E.C. Schulte; R. Sheyor; K. Slifer; P. Solvignon; V. Sulkosky; G.M. Urciuoli; E. Voutier; K. Wang; K. Wijesooriya; B. Wojtsekhowski; L. Zhu

    2007-02-26

    We measured the angular dependence of the three recoil proton polarization components in two-body photodisintegration of the deuteron at a photon energy of 2 GeV. These new data provide a benchmark for calculations based on quantum chromodynamics. Two of the five existing models have made predictions of polarization observables. Both explain the longitudinal polarization transfer satisfactorily.. Transverse polarizations are not well described, but suggest isovector dominance.

  16. BlackMax: A black-hole event generator with rotation, recoil, split branes, and brane tension

    SciTech Connect

    Dai Dechang; Starkman, Glenn; Stojkovic, Dejan; Issever, Cigdem; Tseng, Jeff; Rizvi, Eram

    2008-04-01

    We present a comprehensive black-hole event generator, BlackMax, which simulates the experimental signatures of microscopic and Planckian black-hole production and evolution at the LHC in the context of brane world models with low-scale quantum gravity. The generator is based on phenomenologically realistic models free of serious problems that plague low-scale gravity, thus offering more realistic predictions for hadron-hadron colliders. The generator includes all of the black-hole gray-body factors known to date and incorporates the effects of black-hole rotation, splitting between the fermions, nonzero brane tension, and black-hole recoil due to Hawking radiation (although not all simultaneously). The generator can be interfaced with Herwig and Pythia. The main code can be downloaded from http://www-pnp.physics.ox.ac.uk/{approx}issever/BlackMax/blackmax.html.

  17. Continuous and Pulsed Quantum Zeno Effect

    SciTech Connect

    Streed, Erik W.; Mun, Jongchul; Boyd, Micah; Campbell, Gretchen K.; Medley, Patrick; Ketterle, Wolfgang; Pritchard, David E.

    2006-12-31

    Continuous and pulsed quantum Zeno effects were observed using a {sup 87}Rb Bose-Einstein condensate. Oscillations between two ground hyperfine states of a magnetically trapped condensate, externally driven at a transition rate {omega}{sub R}, were suppressed by destructively measuring the population in one of the states with resonant light. The suppression of the transition rate in the two-level system was quantified for pulsed measurements with a time interval {delta}t between pulses and continuous measurements with a scattering rate {gamma}. We observe that the continuous measurements exhibit the same suppression in the transition rate as the pulsed measurements when {gamma}{delta}t=3.60(0.43), in agreement with the predicted value of 4. Increasing the measurement rate suppressed the transition rate down to 0.005{omega}{sub R}.

  18. Peltier effect in strongly driven quantum wires

    NASA Astrophysics Data System (ADS)

    Mierzejewski, M.; Crivelli, D.; Prelovek, P.

    2014-08-01

    We study a microscopic model of a thermocouple device with two connected correlated quantum wires driven by a constant electric field. In such a closed system we follow the time and position dependence of the entropy density using the concept of the reduced density matrix. At weak driving, the initial changes of the entropy at the junctions can be described by the linear Peltier response. At longer times the quasiequilibrium situation is reached with well defined local temperatures which increase due to an overall Joule heating. On the other hand, a strong electric field induces a nontrivial nonlinear thermoelectric response, e.g., the Bloch oscillations of the energy current. Moreover, we show for the doped Mott insulators that strong driving can reverse the Peltier effect.

  19. Stark effect in diffused quantum wells

    NASA Astrophysics Data System (ADS)

    Vlaev, S. J.; Miteva, A. M.; Contreras-Solorio, D. A.; Velasco, V. R.

    1999-11-01

    We study the longitudinal Stark effect in diffused AlGaAs/GaAs quantum wells grown along the [1,0,0] direction. The energies of the ground electron and hole states and the first excited hole state are calculated for different diffusion lengths and electric field strengths. The energies of the main optical transitions and their Stark shifts are found. The intensities of the transitions are considered in terms of the bound states spatial distributions. The calculations are carried out within the semi-empirical sp 3s * tight-binding model including spin and the surface Green function matching method. We compare our results with those obtained by means of other theoretical methods.

  20. Macroscopic quantum effects for classical light

    NASA Astrophysics Data System (ADS)

    Petrov, N. I.

    2014-10-01

    Optical analogies of macroscopic quantum effects (Schrdinger cat states, squeezing, collapse, and revival) for light beams propagating in an inhomogeneous linear medium are demonstrated theoretically using exact analytical solutions of the wave equation. It is shown that the coherent superposition of macroscopically distinguishable states is generated via mode interference from an initial off-axis single wave packet. Squeezed cat states with a fidelity >99% arise periodically and disappear rapidly within limited intervals of a propagation distance. Collapse and revival of wave packets at long-term nonparaxial evolution due to mode interference is demonstrated. Oscillations of the beam trajectory occur with extremely small amplitude, of the order of 10-19 m, which is typical of the estimated displacement caused by cosmic gravitational waves in gravity-wave detectors.

  1. Quantum Hall effects in a non-Abelian honeycomb lattice

    NASA Astrophysics Data System (ADS)

    Li, Ling; Hao, Ningning; Liu, Guocai; Bai, Zhiming; Li, Zai-Dong; Chen, Shu; Liu, W. M.

    2015-12-01

    We study the tunable quantum Hall effects in a non-Abelian honeycomb optical lattice which is a multi-Dirac-point system. We find that the quantum Hall effects present different features with the change in relative strengths of several perturbations. Namely, the quantum spin Hall effect can be induced by gauge-field-dressed next-nearest-neighbor hopping, which, together with a Zeeman field, can induce the quantum anomalous Hall effect characterized by different Chern numbers. Furthermore, we find that the edge states of the multi-Dirac-point system represent very different features for different boundary geometries, in contrast with the generic two-Dirac-point system. Our study extends the borders of the field of quantum Hall effects in a honeycomb optical lattice with multivalley degrees of freedom.

  2. Effective Fault-Tolerant Quantum Computation with Slow Measurements

    SciTech Connect

    DiVincenzo, David P.; Aliferis, Panos

    2007-01-12

    How important is fast measurement for fault-tolerant quantum computation? Using a combination of existing and new ideas, we argue that measurement times as long as even 1000 gate times or more have a very minimal effect on the quantum accuracy threshold. This shows that slow measurement, which appears to be unavoidable in many implementations of quantum computing, poses no essential obstacle to scalability.

  3. On Quantum Effects in a Theory of Biological Evolution

    PubMed Central

    Martin-Delgado, M. A.

    2012-01-01

    We construct a descriptive toy model that considers quantum effects on biological evolution starting from Chaitin's classical framework. There are smart evolution scenarios in which a quantum world is as favorable as classical worlds for evolution to take place. However, in more natural scenarios, the rate of evolution depends on the degree of entanglement present in quantum organisms with respect to classical organisms. If the entanglement is maximal, classical evolution turns out to be more favorable. PMID:22413059

  4. The effective field theory treatment of quantum gravity

    SciTech Connect

    Donoghue, John F.

    2012-09-24

    This is a pedagogical introduction to the treatment of quantum general relativity as an effective field theory. It starts with an overview of the methods of effective field theory and includes an explicit example. Quantum general relativity matches this framework and I discuss gravitational examples as well as the limits of the effective field theory. I also discuss the insights from effective field theory on the gravitational effects on running couplings in the perturbative regime.

  5. Quantum interference phenomena in the Casimir effect

    NASA Astrophysics Data System (ADS)

    Allocca, Andrew A.; Wilson, Justin H.; Galitski, Victor M.

    2015-06-01

    We propose a definitive test of whether plates involved in Casimir experiments should be modeled with ballistic or diffusive electronsa prominent controversy highlighted by a number of conflicting experiments. The unambiguous test we propose is a measurement of the Casimir force between a disordered quasi-two-dimensional metallic plate and a three-dimensional metallic system at low temperatures, in which disorder-induced weak-localization effects modify the well-known Drude result in an experimentally tunable way. We calculate the weak-localization correction to the Casimir force as a function of magnetic field and temperature and demonstrate that the quantum interference suppression of the Casimir force is a strong, observable effect. The coexistence of weak-localization suppression in electronic transport and Casimir pressure would lend credence to the Drude theory of the Casimir effect, while the lack of such correlation would indicate a fundamental problem with the existing theory. We also study mesoscopic disorder fluctuations in the Casimir effect and estimate the width of the distribution of Casmir energies due to disorder fluctuations.

  6. Nuclear quantum effects and kinetic isotope effects in enzyme reactions.

    PubMed

    Vardi-Kilshtain, Alexandra; Nitoker, Neta; Major, Dan Thomas

    2015-09-15

    Enzymes are extraordinarily effective catalysts evolved to perform well-defined and highly specific chemical transformations. Studying the nature of rate enhancements and the mechanistic strategies in enzymes is very important, both from a basic scientific point of view, as well as in order to improve rational design of biomimetics. Kinetic isotope effect (KIE) is a very important tool in the study of chemical reactions and has been used extensively in the field of enzymology. Theoretically, the prediction of KIEs in condensed phase environments such as enzymes is challenging due to the need to include nuclear quantum effects (NQEs). Herein we describe recent progress in our group in the development of multi-scale simulation methods for the calculation of NQEs and accurate computation of KIEs. We also describe their application to several enzyme systems. In particular we describe the use of combined quantum mechanics/molecular mechanics (QM/MM) methods in classical and quantum simulations. The development of various novel path-integral methods is reviewed. These methods are tailor suited to enzyme systems, where only a few degrees of freedom involved in the chemistry need to be quantized. The application of the hybrid QM/MM quantum-classical simulation approach to three case studies is presented. The first case involves the proton transfer in alanine racemase. The second case presented involves orotidine 5'-monophosphate decarboxylase where multidimensional free energy simulations together with kinetic isotope effects are combined in the study of the reaction mechanism. Finally, we discuss the proton transfer in nitroalkane oxidase, where the enzyme employs tunneling as a catalytic fine-tuning tool. PMID:25769515

  7. Ionization and scintillation of nuclear recoils in gaseous xenon

    NASA Astrophysics Data System (ADS)

    Renner, J.; Gehman, V. M.; Goldschmidt, A.; Matis, H. S.; Miller, T.; Nakajima, Y.; Nygren, D.; Oliveira, C. A. B.; Shuman, D.; Álvarez, V.; Borges, F. I. G.; Cárcel, S.; Castel, J.; Cebrián, S.; Cervera, A.; Conde, C. A. N.; Dafni, T.; Dias, T. H. V. T.; Díaz, J.; Esteve, R.; Evtoukhovitch, P.; Fernandes, L. M. P.; Ferrario, P.; Ferreira, A. L.; Freitas, E. D. C.; Gil, A.; Gómez, H.; Gómez-Cadenas, J. J.; González-Díaz, D.; Gutiérrez, R. M.; Hauptman, J.; Hernando Morata, J. A.; Herrera, D. C.; Iguaz, F. J.; Irastorza, I. G.; Jinete, M. A.; Labarga, L.; Laing, A.; Liubarsky, I.; Lopes, J. A. M.; Lorca, D.; Losada, M.; Luzón, G.; Marí, A.; Martín-Albo, J.; Martínez, A.; Moiseenko, A.; Monrabal, F.; Monserrate, M.; Monteiro, C. M. B.; Mora, F. J.; Moutinho, L. M.; Muñoz Vidal, J.; Natal da Luz, H.; Navarro, G.; Nebot-Guinot, M.; Palma, R.; Pérez, J.; Pérez Aparicio, J. L.; Ripoll, L.; Rodríguez, A.; Rodríguez, J.; Santos, F. P.; dos Santos, J. M. F.; Seguí, L.; Serra, L.; Simón, A.; Sofka, C.; Sorel, M.; Toledo, J. F.; Tomás, A.; Torrent, J.; Tsamalaidze, Z.; Veloso, J. F. C. A.; Villar, J. A.; Webb, R. C.; White, J.; Yahlali, N.

    2015-09-01

    Ionization and scintillation produced by nuclear recoils in gaseous xenon at approximately 14 bar have been simultaneously observed in an electroluminescent time projection chamber. Neutrons from radioisotope α-Be neutron sources were used to induce xenon nuclear recoils, and the observed recoil spectra were compared to a detailed Monte Carlo employing estimated ionization and scintillation yields for nuclear recoils. The ability to discriminate between electronic and nuclear recoils using the ratio of ionization to primary scintillation is demonstrated. These results encourage further investigation on the use of xenon in the gas phase as a detector medium in dark matter direct detection experiments.

  8. Quantum confinement effects across two-dimensional planes in MoS{sub 2} quantum dots

    SciTech Connect

    Gan, Z. X.; Liu, L. Z.; Wu, H. Y.; Hao, Y. L.; Shan, Y.; Wu, X. L. E-mail: paul.chu@cityu.edu.hk; Chu, Paul K. E-mail: paul.chu@cityu.edu.hk

    2015-06-08

    The low quantum yield (∼10{sup −5}) has restricted practical use of photoluminescence (PL) from MoS{sub 2} composed of a few layers, but the quantum confinement effects across two-dimensional planes are believed to be able to boost the PL intensity. In this work, PL from 2 to 9 nm MoS{sub 2} quantum dots (QDs) is excluded from the solvent and the absorption and PL spectra are shown to be consistent with the size distribution. PL from MoS{sub 2} QDs is also found to be sensitive to aggregation due to the size effect.

  9. Quantum confinement effects across two-dimensional planes in MoS2 quantum dots

    NASA Astrophysics Data System (ADS)

    Gan, Z. X.; Liu, L. Z.; Wu, H. Y.; Hao, Y. L.; Shan, Y.; Wu, X. L.; Chu, Paul K.

    2015-06-01

    The low quantum yield (10-5) has restricted practical use of photoluminescence (PL) from MoS2 composed of a few layers, but the quantum confinement effects across two-dimensional planes are believed to be able to boost the PL intensity. In this work, PL from 2 to 9 nm MoS2 quantum dots (QDs) is excluded from the solvent and the absorption and PL spectra are shown to be consistent with the size distribution. PL from MoS2 QDs is also found to be sensitive to aggregation due to the size effect.

  10. InAs/GaSb quantum wells: quantum spin Hall effect and topological superconductivity

    NASA Astrophysics Data System (ADS)

    Sitte, Matthias; Everschor-Sitte, Karin; MacDonald, Allan

    2014-03-01

    In recent years, topological insulators (TIs) have attracted great attention as a new quantum state of matter. The first experimental 2D TIs were HgTe/CdTe quantum well heterostructures. Recently, another semiconducting system - the InAs/GaSb quantum well heterostructure - was shown to be a 2D TI as well. These semiconducting heterojunctions have many advantages compared to HgTe/CdTe systems, including continuously tunable band structure via electric fields and stronger proximity coupling to superconductors. Proximity coupling of a 2D TI and an ordinary superconductor gives rise to one-dimensional topological superconductivity which supports non-local excitations known as Majoranas that can be used for topologically protected quantum computing. We perform empirical tight-binding calculations on these systems, studying the topological phases and their properties. With this knowlegde, we then extend our theory to study the proximity effects when InAs/GaSb quantum wells are coupled to a superconductor.

  11. Quantum teleportation of nonclassical wave packets: An effective multimode theory

    SciTech Connect

    Benichi, Hugo; Takeda, Shuntaro; Lee, Noriyuki; Furusawa, Akira

    2011-07-15

    We develop a simple and efficient theoretical model to understand the quantum properties of broadband continuous variable quantum teleportation. We show that, if stated properly, the problem of multimode teleportation can be simplified to teleportation of a single effective mode that describes the input state temporal characteristic. Using that model, we show how the finite bandwidth of squeezing and external noise in the classical channel affect the output teleported quantum field. We choose an approach that is especially relevant for the case of non-Gaussian nonclassical quantum states and we finally back-test our model with recent experimental results.

  12. Chaos and the quantum: how nonlinear effects can explain certain quantum paradoxes

    NASA Astrophysics Data System (ADS)

    McHarris, Wm C.

    2011-07-01

    In recent years we have suggested that many of the so-called paradoxes resulting from the Copenhagen interpretation of quantum mechanics could well have more logical parallels based in nonlinear dynamics and chaos theory. Perhaps quantum mechanics might not be strictly linear as has been commonly postulated, and indeed, during the past year experimentalists have discovered signatures of chaos in a definitely quantum system. As an illustration of what can go wrong when quantum effects are forced into a linear interpretation, I examine Bell-type inequalities. In conventional derivations of such inequalities, classical systems are found to impose upper limits on the statistical correlations between, say, the properties of a pair of separated but entangled particles, whereas quantum systems allow greater correlations. Numerous experiments have upheld the quantum predictions (greater statistical correlations than allowed classically), which has led to inferences such as the instantaneous transmission of information between effectively infinitely separated particles Einstein's "spooky action-at-a-distance," incompatible with relativity. I argue that there is nothing wrong with the quantum mechanical side of such derivations (the usual point of attack by those attempting to debunk Bell-type arguments), but implicit in the derivations on the classical side is the assumption of independent, uncorrelated particles. As a result, one is comparing uncorrelated probabilities versus conditional probabilities rather than comparing classical versus quantum mechanics, making moot the experimental inferences. Further, nonlinear classical systems are known to exhibit correlations that can easily be as great as and overlap with quantum correlations so-called nonextensive thermodynamics with its nonadditive entropy has verified this with numerous examples. Perhaps quantum mechanics does contain fundamental nonlinear elements. Nonlinear dynamics and chaos theory could well provide a bridge between the determinism so dear to Einstein and the statisical interpretation of the Copenhagen school. Einstein and Bohr both could have been right in their debates.

  13. Quantum electrodynamics in finite volume and nonrelativistic effective field theories

    NASA Astrophysics Data System (ADS)

    Fodor, Z.; Hoelbling, C.; Katz, S. D.; Lellouch, L.; Portelli, A.; Szabo, K. K.; Toth, B. C.

    2016-04-01

    Electromagnetic effects are increasingly being accounted for in lattice quantum chromodynamics computations. Because of their long-range nature, they lead to large finite-size effects over which it is important to gain analytical control. Nonrelativistic effective field theories provide an efficient tool to describe these effects. Here we argue that some care has to be taken when applying these methods to quantum electrodynamics in a finite volume.

  14. Radiation effects in Si-Ge quantum size structure (Review)

    SciTech Connect

    Sobolev, N. A.

    2013-02-15

    The article is dedicated to the review and analysis of the effects and processes occurring in Si-Ge quantum size semiconductor structures upon particle irradiation including ion implantation. Comparisons to bulk materials are drawn. The reasons of the enhanced radiation hardness of superlattices and quantum dots are elucidated. Some technological applications of the radiation treatment are reviewed.

  15. Quantum corrections to conductivity under conditions of the integer quantum Hall effect

    SciTech Connect

    Greshnov, A. A.

    2012-06-15

    Quantum corrections to the conductivity of a two-dimensional electron gas under conditions of the integer quantum Hall effect have been studied. It is shown that violation of the one-parameter scaling under conditions of quantizing magnetic fields, {omega}{sub c}{tau} Much-Greater-Than 1, occurs at a level of the perturbation theory. The results of diagrammatic calculation of the quantum correction are in agreement with the numerical dependences of the peaks in the longitudinal conductivity on the effective size of the sample, in contrast to earlier calculations based on the unitary nonlinear {sigma}-model. Due to this, consideration of Landau quantization represents a criterion for correct description of the quantum Hall effect.

  16. Skyrmion recoil in pion-nucleon scattering

    SciTech Connect

    Hughes, J. Physics Department, University of California at Davis, Davis, California 95616 ); Mathews, G.J. )

    1992-08-01

    We calculate the lowest-order recoil corrections to the pion-nucleon scattering matrix in the SU(2) Skyrme model. The corrections result from a direct semiclassical evaluation of path-integral expressions for relevant finite-time transition amplitudes. The {ital S} matrix for pion-nucleon scattering is extracted from these amplitudes by using a configuration-space representation for the asymptotic nucleons; the quanta are treated just as in the vacuum sector. The recoil corrections result from the Skyrmion freely translating between initial and final positions, and are relevant to a kinematical regime opposite to that where the impulse approximation is valid. The form of the corrections is model independent, unchanged for any chiral model with hedgehog solitary wave solutions. Remarkably, new lowest-lying resonances emerge in the {ital p} channels, whereas the {ital s} and {ital d} waves are not noticeably improved.

  17. Experiments with recoil ions and other considerations

    SciTech Connect

    Cocke, C.L.

    1987-01-01

    Some opportunities in collisions physics with slow, multiply charged ions are addressed. A distinction between inner and outer shell collisions is drawn. The applicability of recoil ion sources to outer shell collision systems is discussed, with emphasis on the quality of the beam desired. An example of an inner shell collision is discussed, and the usefulness of not pushing the collision energy too low is pointed out. 13 refs., 14 figs.

  18. Effective quantum dynamics of two Brownian particles

    NASA Astrophysics Data System (ADS)

    Duarte, O. S.; Caldeira, A. O.

    2009-09-01

    We use the system-plus-reservoir approach to study the quantum dynamics of a bipartite continuous variable system (two generic particles). We present an extension of the traditional model of a bath of oscillators which is capable of inducing an effective coupling between the two parts of the system depending on the choice made for the spectral density of the bath. The coupling is nonlinear in the system variables and an exponential dependence on these variables is imposed in order to guarantee the translational invariance of the model if the two particles are not subject to any external potential. The reduced density operator is obtained by the functional integral method. The dynamical susceptibility of the reservoir is modeled in order to introduce, besides a characteristic frequency, a characteristic length that determines if the effective interaction potential is strong enough to induce entanglement between the particles. Our model provides a criterion of distance for identifying in which cases a common environment can induce entanglement. Three regimes are found: the short distance regime, equivalent to a bilinear system-reservoir coupling, the long distance regime in which the particles act like coupled to independent reservoirs, and the intermediate regime suitable for the competition between decoherence and induced entanglement.

  19. Geometry of the fractional quantum Hall effect

    NASA Astrophysics Data System (ADS)

    Haldane, F. D. M.

    2012-02-01

    Unlike the integer effect, the incompressible electron fluid that exhibits the fractional effect is not invariant under ``area-preserving diffeomorphisms'' of the guiding-center degrees of freedom. Instead (F. D. M. Haldane, Phys. Rev. Lett. 108, 116801 (2011)), it has a shear modulus that characterizes the energy cost of distortions of the correlation hole around the electrons, and a ``guiding-center metric tensor'' that exhibits quantum zero-point fluctuations around a preferred shape. In a simple (one-component) fluid, electronic charge-density fluctuations relative to the background set by the magnetic flux density are given by δρ = (e^*/2π)s K, where e^* is the elementary fractional charge, s is an integer or half-integer ``guiding-center spin'' that is topologically quantized by the Gauss-Bonnet theorem, and K is the local Gaussian curvature of the guiding-center metric. These results provide a simple explanation of the seminal 1985 results of Girvin, MacDonald and Platzman on the FQH structure factor and collective mode, which remained unexplained in previous proposed narrative explanations of FQH incompressibility (Ginzburg-Landau Chern-Simons theory, composite fermions, and non-commutative Chern-Simons field theory).

  20. Oscillatory quantum screening effects on the transition bremsstrahlung radiation in quantum plasmas

    SciTech Connect

    Jung, Young-Dae

    2011-06-15

    The oscillatory screening effects on the transition bremsstrahlung radiation due to the polarization interaction between the electron and shielding cloud are investigated in dense quantum plasmas. The impact-parameter analysis with the modified Debye-Hueckel potential is applied to obtain the bremsstrahlung radiation cross section as a function of the quantum wave number, impact parameter, photon energy, and projectile energy. The results show that the oscillatory quantum screening effect strongly suppresses the transition bremsstrahlung radiation spectrum in dense quantum plasmas. It is also found that the oscillatory quantum screening effect is more significant near the maximum peak of the bremsstrahlung radiation cross section. In addition, the maximum peak of the bremsstrahlung radiation cross section is getting close to the center of the shielding cloud as increasing quantum wave number. It is interesting to note that the range of the bremsstrahlung photon energy would be broadened with an increase of the oscillatory screening effect. It is also found that the oscillatory screening effects on the transition bremsstrahlung spectrum decreases with increasing projectile energy.

  1. Oscillatory quantum screening effects on the transition bremsstrahlung radiation in quantum plasmas

    NASA Astrophysics Data System (ADS)

    Jung, Young-Dae

    2011-06-01

    The oscillatory screening effects on the transition bremsstrahlung radiation due to the polarization interaction between the electron and shielding cloud are investigated in dense quantum plasmas. The impact-parameter analysis with the modified Debye-Hückel potential is applied to obtain the bremsstrahlung radiation cross section as a function of the quantum wave number, impact parameter, photon energy, and projectile energy. The results show that the oscillatory quantum screening effect strongly suppresses the transition bremsstrahlung radiation spectrum in dense quantum plasmas. It is also found that the oscillatory quantum screening effect is more significant near the maximum peak of the bremsstrahlung radiation cross section. In addition, the maximum peak of the bremsstrahlung radiation cross section is getting close to the center of the shielding cloud as increasing quantum wave number. It is interesting to note that the range of the bremsstrahlung photon energy would be broadened with an increase of the oscillatory screening effect. It is also found that the oscillatory screening effects on the transition bremsstrahlung spectrum decreases with increasing projectile energy.

  2. From quantum confinement to quantum Hall effect in graphene nanostructures

    NASA Astrophysics Data System (ADS)

    Guimarães, M. H. D.; Shevtsov, O.; Waintal, X.; van Wees, B. J.

    2012-02-01

    We study the evolution of the two-terminal conductance plateaus with a magnetic field for armchair graphene nanoribbons (GNRs) and graphene nanoconstrictions (GNCs). For GNRs, the conductance plateaus of (2e2)/(h) at zero magnetic field evolve smoothly to the quantum Hall regime, where the plateaus in conductance at even multiples of (2e2)/(h) disappear. It is shown that the relation between the energy and magnetic field does not follow the same behavior as in “bulk” graphene, reflecting the different electronic structure of a GNR. For the nanoconstrictions we show that the conductance plateaus do not have the same sharp behavior in zero magnetic field as in a GNR, which reflects the presence of backscattering in such structures. Our results show good agreement with recent experiments on high-quality graphene nanoconstrictions. The behavior with the magnetic field for a GNC shows some resemblance to the one for a GNR but now depends also on the length of the constriction. By analyzing the evolution of the conductance plateaus in the presence of the magnetic field we can obtain the width of the structures studied and show that this is a powerful experimental technique in the study of the electronic and structural properties of narrow structures.

  3. Monte Carlo simulation of quantum Zeno effect in the brain

    NASA Astrophysics Data System (ADS)

    Georgiev, Danko

    2015-12-01

    Environmental decoherence appears to be the biggest obstacle for successful construction of quantum mind theories. Nevertheless, the quantum physicist Henry Stapp promoted the view that the mind could utilize quantum Zeno effect to influence brain dynamics and that the efficacy of such mental efforts would not be undermined by environmental decoherence of the brain. To address the physical plausibility of Stapp's claim, we modeled the brain using quantum tunneling of an electron in a multiple-well structure such as the voltage sensor in neuronal ion channels and performed Monte Carlo simulations of quantum Zeno effect exerted by the mind upon the brain in the presence or absence of environmental decoherence. The simulations unambiguously showed that the quantum Zeno effect breaks down for timescales greater than the brain decoherence time. To generalize the Monte Carlo simulation results for any n-level quantum system, we further analyzed the change of brain entropy due to the mind probing actions and proved a theorem according to which local projections cannot decrease the von Neumann entropy of the unconditional brain density matrix. The latter theorem establishes that Stapp's model is physically implausible but leaves a door open for future development of quantum mind theories provided the brain has a decoherence-free subspace.

  4. Quantum critical paraelectrics and the Casimir effect in time

    NASA Astrophysics Data System (ADS)

    Plov, L.; Chandra, P.; Coleman, P.

    2009-02-01

    We study the quantum paraelectric-ferroelectric transition near a quantum critical point, emphasizing the role of temperature as a finite-size effect in time. The influence of temperature near quantum criticality may thus be likened to a temporal Casimir effect. The resulting finite-size scaling approach yields (1)/(T2) behavior of the paraelectric susceptibility (?) and the scaling form ?(?,T)=(1)/(?2)F((?)/(T)) , recovering results previously found by more technical methods. We use a Gaussian theory to illustrate how these temperature dependences emerge from a microscopic approach; we characterize the classical-quantum crossover in ? , and the resulting phase diagram is presented. We also show that coupling to an acoustic phonon at low temperatures (T) is relevant and influences the transition line, possibly resulting in a reentrant quantum ferroelectric phase. Observable consequences of our approach for measurements on specific paraelectric materials at low temperatures are discussed.

  5. Effects of the generalised uncertainty principle on quantum tunnelling

    NASA Astrophysics Data System (ADS)

    Blado, Gardo; Prescott, Trevor; Jennings, James; Ceyanes, Joshuah; Sepulveda, Rafael

    2016-03-01

    In a previous paper (Blado et al 2014 Eur. J. Phys. 35 065011), we showed that quantum gravity effects can be discussed with only a background in non-relativistic quantum mechanics at the undergraduate level by looking at the effect of the generalised uncertainty principle (GUP) on the finite and infinite square wells. In this paper, we derive the GUP corrections to the tunnelling probability of simple quantum mechanical systems which are accessible to undergraduates (alpha decay, simple models of quantum cosmogenesis and gravitational tunnelling radiation) and which employ the WKB approximation, a topic discussed in undergraduate quantum mechanics classes. It is shown that the GUP correction increases the tunnelling probability in each of the examples discussed.

  6. Graphene/Si-quantum-dot heterojunction diodes showing high photosensitivity compatible with quantum confinement effect.

    PubMed

    Shin, Dong Hee; Kim, Sung; Kim, Jong Min; Jang, Chan Wook; Kim, Ju Hwan; Lee, Kyeong Won; Kim, Jungkil; Oh, Si Duck; Lee, Dae Hun; Kang, Soo Seok; Kim, Chang Oh; Choi, Suk-Ho; Kim, Kyung Joong

    2015-04-24

    Graphene/Si quantum dot (QD) heterojunction diodes are reported for the first time. The photoresponse, very sensitive to variations in the size of the QDs as well as in the doping concentration of graphene and consistent with the quantum-confinement effect, is remarkably enhanced in the near-ultraviolet range compared to commercially available bulk-Si photodetectors. The photoresponse proves to be dominated by the carriertunneling mechanism. PMID:25776865

  7. Polaronic effects in a Gaussian quantum dot

    NASA Astrophysics Data System (ADS)

    Yanar, Sonay; Sevim, Ata; Boyacioglu, B.; Saglam, Mesude; Mukhopadhyaya, Soma; Chatterjee, Ashok

    2008-03-01

    The problem of an electron interacting with longitudinal-optical (LO) phonons is investigated in an N-dimensional quantum dot with symmetric Gaussian confinement in all directions using the Rayleigh-Schrödinger perturbation theory, a variant of the canonical transformation method of Lee-Low-Pines, and the sophisticated apparatus of the Feynman-Haken path-integral technique for the entire range of the coupling parameters and the results for N=2 and N=3 are obtained as special cases. It is shown that the polaronic effects are quite significant for small dots with deep confining potential well and the parabolic potential is only a poor approximation of the Gaussian confinement. The Feynman-Haken path-integral technique in general gives a good upper bound to the ground state energy for all values of the system parameters and therefore is used as a benchmark for comparison between different methods. It is shown that the perturbation theory yields for the ground state polaron self-energy a simple closed-form analytic expression containing only Gamma functions and in the weak-coupling regime it provides the lowest energy because of an efficient partitioning of the Gaussian potential and the subsequent use of a mean-field kind of treatment. The polarization potential, the polaron radius and the number of virtual phonons in the polaron cloud are obtained using the Lee-Low-Pines-Huybrechts method and their variations with respect to different parameters of the system are discussed.

  8. Towards witnessing quantum effects in complex molecules.

    PubMed

    Farrow, T; Taylor, R A; Vedral, V

    2015-12-12

    Whether many-body objects like organic molecules can exhibit full quantum behaviour, including entanglement, is an open fundamental question. We present a generic theoretical protocol for entangling two organic molecules, such as dibenzoterrylene in anthracene. The availability of organic dye molecules with two-level energy structures characterised by sharp and intense emission lines are characteristics that position them favourably as candidates for quantum information processing technologies involving single-photons. Quantum entanglement can in principle be generated between several organic molecules by carefully interfering their photoluminescence spectra. Major milestones have been achieved in the last 10 years showcasing entanglement in diverse systems including ions, cold atoms, superconductors, photons, quantum dots and NV-centres in diamond, but not yet in molecules. PMID:26428546

  9. Plasmon modes of metallic nanowires including quantum nonlocal effects

    SciTech Connect

    Moradi, Afshin

    2015-03-15

    The properties of electrostatic surface and bulk plasmon modes of cylindrical metallic nanowires are investigated, using the quantum hydrodynamic theory of plasmon excitation which allows an analytical study of quantum tunneling effects through the Bohm potential term. New dispersion relations are obtained for each type of mode and their differences with previous treatments based on the standard hydrodynamic model are analyzed in detail. Numerical results show by considering the quantum effects, as the value of wave number increases, the surface modes are slightly red-shifted first and then blue-shifted while the bulk modes are blue-shifted.

  10. A cavity-mediated collective quantum effect in sonoluminescing bubbles

    NASA Astrophysics Data System (ADS)

    Beige, Almut; Kim, Oleg

    2015-12-01

    This paper discusses a collective quantum effect which might play an important role in sonoluminescence experiments. We suggest that it occurs during the final stages of the collapse phase and enhances the heating of the particles inside the bubble.

  11. Semi-inclusive deep-inelastic scattering off few-nucleon systems: Tagging the EMC effect and hadronization mechanisms with detection of slow recoiling nuclei

    NASA Astrophysics Data System (ADS)

    Ciofi Degli Atti, C.; Kaptari, L. P.

    2011-04-01

    The semi-inclusive deep-inelastic scattering of electrons off H2 and He3 with detection of slow protons and deuterons, respectively, i.e., the processes 2H(e,e'p)X and 3He(e,e'd)X, are calculated within the spectator mechanism, taking into account the final state interaction of the nucleon debris with the detected protons and deuterons. It is shown that by a proper choice of the kinematics the origin of the EMC effect and the details of the interaction between the hadronizing quark and the nuclear medium can be investigated at a level which cannot be reached by inclusive deep-inelastic scattering. A comparison of the results of our calculations, containing no adjustable parameters, with recently available experimental data on the process 2H(e,e'p)X shows a good agreement in the backward hemisphere of the emitted nucleons. Theoretical predictions at energies that will be available at the upgraded Thomas Jefferson National Accelerator Facility are presented, and the possibility to investigate the proposed semi-inclusive processes at electron-ion colliders is briefly discussed.

  12. Electron-exchange and quantum screening effects on the Thomson scattering process in quantum Fermi plasmas

    SciTech Connect

    Lee, Gyeong Won; Jung, Young-Dae; Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, 110 Eighth Street, Troy, New York 12180-3590

    2013-06-15

    The influence of the electron-exchange and quantum screening on the Thomson scattering process is investigated in degenerate quantum Fermi plasmas. The Thomson scattering cross section in quantum plasmas is obtained by the plasma dielectric function and fluctuation-dissipation theorem as a function of the electron-exchange parameter, Fermi energy, plasmon energy, and wave number. It is shown that the electron-exchange effect enhances the Thomson scattering cross section in quantum plasmas. It is also shown that the differential Thomson scattering cross section has a minimum at the scattering angle ?=?/2. It is also found that the Thomson scattering cross section increases with an increase of the Fermi energy. In addition, the Thomson scattering cross section is found to be decreased with increasing plasmon energy.

  13. Intrinsic Spin Hall Effect Induced by Quantum Phase Transition in HgCdTe Quantum Wells

    SciTech Connect

    Yang, Wen; Chang, Kai; Zhang, Shou-Cheng; /Stanford U., Phys. Dept.

    2010-03-19

    Spin Hall effect can be induced both by the extrinsic impurity scattering and by the intrinsic spin-orbit coupling in the electronic structure. The HgTe/CdTe quantum well has a quantum phase transition where the electronic structure changes from normal to inverted. We show that the intrinsic spin Hall effect of the conduction band vanishes on the normal side, while it is finite on the inverted side. This difference gives a direct mechanism to experimentally distinguish the intrinsic spin Hall effect from the extrinsic one.

  14. Accelerating quantum instanton calculations of the kinetic isotope effects.

    PubMed

    Karandashev, Konstantin; Van?ek, Ji?

    2015-11-21

    Path integral implementation of the quantum instanton approximation currently belongs among the most accurate methods for computing quantum rate constants and kinetic isotope effects, but its use has been limited due to the rather high computational cost. Here, we demonstrate that the efficiency of quantum instanton calculations of the kinetic isotope effects can be increased by orders of magnitude by combining two approaches: The convergence to the quantum limit is accelerated by employing high-order path integral factorizations of the Boltzmann operator, while the statistical convergence is improved by implementing virial estimators for relevant quantities. After deriving several new virial estimators for the high-order factorization and evaluating the resulting increase in efficiency, using ?H? + H?H? ? H?H? + ? H? reaction as an example, we apply the proposed method to obtain several kinetic isotope effects on CH4 + ? H ? ? CH3 + H2 forward and backward reactions. PMID:26590524

  15. Accelerating quantum instanton calculations of the kinetic isotope effects

    NASA Astrophysics Data System (ADS)

    Karandashev, Konstantin; Van?ek, Ji?

    2015-11-01

    Path integral implementation of the quantum instanton approximation currently belongs among the most accurate methods for computing quantum rate constants and kinetic isotope effects, but its use has been limited due to the rather high computational cost. Here, we demonstrate that the efficiency of quantum instanton calculations of the kinetic isotope effects can be increased by orders of magnitude by combining two approaches: The convergence to the quantum limit is accelerated by employing high-order path integral factorizations of the Boltzmann operator, while the statistical convergence is improved by implementing virial estimators for relevant quantities. After deriving several new virial estimators for the high-order factorization and evaluating the resulting increase in efficiency, using ?H? + H?H? ? H?H? + ? H? reaction as an example, we apply the proposed method to obtain several kinetic isotope effects on CH4 + ? H ? ? CH3 + H2 forward and backward reactions.

  16. Quantum-confined strain gradient effect in semiconductor nanomembranes

    NASA Astrophysics Data System (ADS)

    Binder, R.; Gu, B.; Kwong, N. H.

    2014-11-01

    Semiconductor nanomembranes can exhibit strain gradients that lead to quantum confinement effects similar to the well known quantum-confined Stark effect (QCSE) in semiconductor quantum wells. The deformation of square well into triangular well potential leads to modifications of the exciton resonance, but important differences between the quantum-confined strain gradient effect (QCsgE) and the QCSE include (i) the versatility of the QCsgE in which conduction and valence bands can have different slopes (even reverse slopes are possible), and (ii) the fact that in the QCsgE exciton shifts are determined by the gradients in the heavy-hole and light-hole energies as well as a gradient in the heavy-hole and light-hole coupling.

  17. Recoiling black holes: prospects for detection and implications of spin alignment

    NASA Astrophysics Data System (ADS)

    Blecha, Laura; Sijacki, Debora; Kelley, Luke Zoltan; Torrey, Paul; Vogelsberger, Mark; Nelson, Dylan; Springel, Volker; Snyder, Gregory; Hernquist, Lars

    2016-02-01

    Supermassive black hole (BH) mergers produce powerful gravitational wave emission. Asymmetry in this emission imparts a recoil kick to the merged BH, which can eject the BH from its host galaxy altogether. Recoiling BHs could be observed as offset active galactic nuclei (AGN). Several candidates have been identified, but systematic searches have been hampered by large uncertainties regarding their observability. By extracting merging BHs and host galaxy properties from the Illustris cosmological simulations, we have developed a comprehensive model for recoiling AGN. Here, for the first time, we model the effects of BH spin alignment and recoil dynamics based on the gas richness of host galaxies. We predict that if BH spins are not highly aligned, seeing-limited observations could resolve offset AGN, making them promising targets for all-sky surveys. For randomly oriented spins, ≲ 10 spatially offset AGN may be detectable in Hubble Space Telescope-Cosmological Evolution Survey, and >103 could be found with the Panoramic Survey Telescope & Rapid Response System (Pan-STARRS), the Large Synoptic Survey Telescope (LSST), Euclid, and the Wide-Field Infrared Survey Telescope (WFIRST). Nearly a thousand velocity offset AGN are predicted within the Sloan Digital Sky Survey (SDSS) footprint; the rarity of large broad-line offsets among SDSS quasars is likely due in part to selection effects but suggests that spin alignment plays a role in suppressing recoils. None the less, in our most physically motivated model where alignment occurs only in gas-rich mergers, hundreds of offset AGN should be found in all-sky surveys. Our findings strongly motivate a dedicated search for recoiling AGN.

  18. Modulational instability of electrostatic acoustic waves in an electron-hole semiconductor quantum plasma

    SciTech Connect

    Wang, Yunliang L, Xiaoxia

    2014-02-15

    The modulational instability of quantum electrostatic acoustic waves in electron-hole quantum semiconductor plasmas is investigated using the quantum hydrodynamic model, from which a modified nonlinear Schrdinger equation with damping effects is derived using the reductive perturbation method. Here, we consider the combined effects of quantum recoil, quantum degenerate pressures, as well as the exchange-correlation effect standing for the electrons (holes) spin. The modulational instability for different semiconductors (GaAs, GaSb, and InP) is discussed. The collision between electron (hole) and phonon is also investigated. The permitted maximum time for modulational instability and the damping features of quantum envelope solitary wave are all determined by the collision. The approximate solitary solution with damping effects is presented in weak collision limit. The damping properties were discussed by numerical method.

  19. Neutron electric form factor via recoil polarimetry

    SciTech Connect

    Madey, Richard; Semenov, Andrei; Taylor, Simon; Aghalaryan, Aram; Crouse, Erick; MacLachlan, Glen; Plaster, Bradley; Tajima, Shigeyuki; Tireman, William; Yan, Chenyu; Ahmidouch, Abdellah; Anderson, Brian; Asaturyan, Razmik; Baker, O; Baldwin, Alan; Breuer, Herbert; Carlini, Roger; Christy, Michael; Churchwell, Steve; Cole, Leon; Danagoulian, Samuel; Day, Donal; Elaasar, Mostafa; Ent, Rolf; Farkhondeh, Manouchehr; Fenker, Howard; Finn, John; Gan, Liping; Garrow, Kenneth; Gueye, Paul; Howell, Calvin; Hu, Bitao; Jones, Mark; Kelly, James; Keppel, Cynthia; Khandaker, Mahbubul; Kim, Wooyoung; Kowalski, Stanley; Lung, Allison; Mack, David; Manley, D; Markowitz, Pete; Mitchell, Joseph; Mkrtchyan, Hamlet; Opper, Allena; Perdrisat, Charles; Punjabi, Vina; Raue, Brian; Reichelt, Tilmann; Reinhold, Joerg; Roche, Julie; Sato, Yoshinori; Seo, Wonick; Simicevic, Neven; Smith, Gregory; Stepanyan, Samuel; Tadevosyan, Vardan; Tang, Liguang; Ulmer, Paul; Vulcan, William; Watson, John; Wells, Steven; Wesselmann, Frank; Wood, Stephen; Yan, Chen; Yang, Seunghoon; Yuan, Lulin; Zhang, Wei-Ming; Zhu, Hong Guo; Zhu, Xiaofeng

    2003-05-01

    The ratio of the electric to the magnetic form factor of the neutron, G_En/G_Mn, was measured via recoil polarimetry from the quasielastic d({pol-e},e'{pol-n)p reaction at three values of Q^2 [viz., 0.45, 1.15 and 1.47 (GeV/c)^2] in Hall C of the Thomas Jefferson National Accelerator Facility. Preliminary data indicate that G_En follows the Galster parameterization up to Q^2 = 1.15 (GeV/c)^2 and appears to rise above the Galster parameterization at Q^2 = 1.47 (GeV/c)^2.

  20. Recombination in liquid xenon for low-energy recoils

    NASA Astrophysics Data System (ADS)

    Wang, Lu; Mei, Dongming; Cubed Collaboration

    2014-09-01

    Detector response to low-energy recoils in sub-keV region is critical to detection of low-mass dark matter particles-WIMPS (Weakly interacting massive particles). The role of electron-ion recombination is important to the interpretation of the relation between ionization yield and scintillation yield, which are in general anti-correlated. Recent experimental results show that ionization yield increases down to keV range. This phenomenon contradicts general understanding for low energy recoils in the keV range in which direct excitation dominates. The explanation is that recombination becomes much less efficient when the track length is smaller than the thermalization distance of electrons. However, recombination rate is also proportional to ionization density, which is very high for keV recoils. To understand how recombination rate behaves for keV recoils, we calculated both initial recombination rate and volume recombination rate for keV recoils in liquid xenon. In this paper, we show the results of the calculated recombination rate as a function of recoil energy for both electronic recoils and nuclear recoils. Detector response to low-energy recoils in sub-keV region is critical to detection of low-mass dark matter particles-WIMPS (Weakly interacting massive particles). The role of electron-ion recombination is important to the interpretation of the relation between ionization yield and scintillation yield, which are in general anti-correlated. Recent experimental results show that ionization yield increases down to keV range. This phenomenon contradicts general understanding for low energy recoils in the keV range in which direct excitation dominates. The explanation is that recombination becomes much less efficient when the track length is smaller than the thermalization distance of electrons. However, recombination rate is also proportional to ionization density, which is very high for keV recoils. To understand how recombination rate behaves for keV recoils, we calculated both initial recombination rate and volume recombination rate for keV recoils in liquid xenon. In this paper, we show the results of the calculated recombination rate as a function of recoil energy for both electronic recoils and nuclear recoils. DE-FG02-10ER46709 and the state of South Dakota.

  1. Thermal recoil force, telemetry, and the Pioneer anomaly

    NASA Astrophysics Data System (ADS)

    Toth, Viktor T.; Turyshev, Slava G.

    2009-02-01

    Precision navigation of spacecraft requires accurate knowledge of small forces, including the recoil force due to anisotropies of thermal radiation emitted by spacecraft systems. We develop a formalism to derive the thermal recoil force from the basic principles of radiative heat exchange and energy-momentum conservation. The thermal power emitted by the spacecraft can be computed from engineering data obtained from flight telemetry, which yields a practical approach to incorporate the thermal recoil force into precision spacecraft navigation. Alternatively, orbit determination can be used to estimate the contribution of the thermal recoil force. We apply this approach to the Pioneer anomaly using a simulated Pioneer 10 Doppler data set.

  2. Thermal recoil force, telemetry, and the Pioneer anomaly

    SciTech Connect

    Toth, Viktor T.; Turyshev, Slava G.

    2009-02-15

    Precision navigation of spacecraft requires accurate knowledge of small forces, including the recoil force due to anisotropies of thermal radiation emitted by spacecraft systems. We develop a formalism to derive the thermal recoil force from the basic principles of radiative heat exchange and energy-momentum conservation. The thermal power emitted by the spacecraft can be computed from engineering data obtained from flight telemetry, which yields a practical approach to incorporate the thermal recoil force into precision spacecraft navigation. Alternatively, orbit determination can be used to estimate the contribution of the thermal recoil force. We apply this approach to the Pioneer anomaly using a simulated Pioneer 10 Doppler data set.

  3. Quantum effects after decoherence in a quenched phase transition.

    PubMed

    Antunes, N D; Lombardo, F C; Monteoliva, D

    2001-12-01

    We study a quantum mechanical toy model that mimics some features of a quenched phase transition. Both by virtue of a time-dependent Hamiltonian or by changing the temperature of the bath we are able to show that even after classicalization has been reached, the system may display quantum behavior again. We explain this behavior in terms of simple nonlinear analysis and estimate relevant time scales that match the results of numerical simulations of the master equation. This opens new possibilities both in the study of quantum effects in nonequilibrium phase transitions and in general time-dependent problems where quantum effects may be relevant even after decoherence has been completed. PMID:11736247

  4. Detecting Quantum Gravitational Effects of Loop Quantum Cosmology in the Early Universe?

    NASA Astrophysics Data System (ADS)

    Zhu, Tao; Wang, Anzhong; Cleaver, Gerald; Kirsten, Klaus; Sheng, Qin; Wu, Qiang

    2015-07-01

    We derive the primordial power spectra and spectral indexes of the density fluctuations and gravitational waves in the framework of loop quantum cosmology (LQC) with holonomy and inverse-volume corrections by using the uniform asymptotic approximation method to its third order, at which the upper error bounds are ? 0.15% and accurate enough for the current and forthcoming cosmological observations. Then, using the Planck, BAO, and supernova data, we obtain the tightest constraints on quantum gravitational effects from LQC corrections and find that such effects could be well within the detection of the current and forthcoming cosmological observations.

  5. Spacetime effects on satellite-based quantum communications

    NASA Astrophysics Data System (ADS)

    Bruschi, David Edward; Ralph, Timothy C.; Fuentes, Ivette; Jennewein, Thomas; Razavi, Mohsen

    2014-08-01

    We investigate the consequences of space-time being curved on space-based quantum communication protocols. We analyze tasks that require either the exchange of single photons in a certain entanglement distribution protocol or beams of light in a continuous-variable quantum key distribution scheme. We find that gravity affects the propagation of photons, therefore adding additional noise to the channel for the transmission of information. The effects could be measured with current technology.

  6. Quantum Electrodynamics Effects in Heavy Ions and Atoms

    SciTech Connect

    Shabaev, V. M.; Andreev, O. V.; Bondarev, A. I.; Glazov, D. A.; Kozhedub, Y. S.; Maiorova, A. V.; Tupitsyn, I. I.; Plunien, G.; Volotka, A. V.

    2011-05-11

    Quantum electrodynamics theory of heavy ions and atoms is considered. The current status of calculations of the binding energies, the hyperfine splitting and g factor values in heavy few-electron ions is reviewed. The theoretical predictions are compared with available experimental data. A special attention is focused on tests of quantum electrodynamics in strong electromagnetic fields and on determination of the fundamental constants. Recent progress in calculations of the parity nonconservation effects with heavy atoms and ions is also reported.

  7. Effective quantum dynamics of interacting systems with inhomogeneous coupling

    SciTech Connect

    Lopez, C. E.; Retamal, J. C.; Christ, H.; Solano, E.

    2007-03-15

    We study the quantum dynamics of a single mode (particle) interacting inhomogeneously with a large number of particles and introduce an effective approach to find the accessible Hilbert space, where the dynamics takes place. Two relevant examples are given: the inhomogeneous Tavis-Cummings model (e.g., N atomic qubits coupled to a single cavity mode, or to a motional mode in trapped ions) and the inhomogeneous coupling of an electron spin to N nuclear spins in a quantum dot.

  8. An effective non-commutative loop quantum cosmology

    NASA Astrophysics Data System (ADS)

    Espinoza-Garca, Abraham; Sabido, M.; Socorro, J.

    2015-11-01

    We construct a Non-Commutative extension of the Loop Quantum Cosmology effective scheme for the open FLRW model. We start from the holonomized Hamiltonian and implement a canonical non-commutativity among the matter degree of freedom and the holonomy variable, in the volume representation. We obtain a noncommutativie extension of the modified Friedmann equation which arises in Loop Quantum Cosmology for a particular case of the theta deformation.

  9. A toy model for quantum spin Hall effect

    NASA Astrophysics Data System (ADS)

    Owerre, S. A.; Nsofini, J.

    2015-09-01

    In this communication, we investigate a toy model of three-dimensional topological insulator surface, coupled homogeneously to a fictitious pseudospin-1/2 particle. We show that this toy model captures the interesting features of topological insulator surface states, which include topological quantum phase transition and quantum spin Hall effect. We further incorporate an out-of-plane magnetic field and obtain the Landau levels.

  10. Numerical simulations of spiral galaxy formation and recoiling black holes

    NASA Astrophysics Data System (ADS)

    Guedes, Javiera M.

    This thesis discusses two major topics in regard to the formation and evolution of galaxies and their central massive black holes (MBH). Part 1 explores the detectability of recoiling massive back as kinematically and spatially offset active galactic nuclei (AGN). Chapter 3 is devoted to understanding the effect of an aspherical dark matter potential on the trajectories of the MBHs. This is done through collisionless N-body simulations of kicked black holes in the Via Lactea I halo and through a semi-analytical model that accounts for the evolution of the halo's triaxiality as a function of radius over cosmic time. We find that the return time of MBHs that wander through a differentially triaxial halo is significantly extended in comparison with spherical models. This is because their trajectories are become highly non-radial which prevents them from passing near the halo's center, where dynamical friction is most efficient. Chapter 4 puts recoiling MBHs into context. Here we carry out N-body + SPH simulations of recoiling MBHs in high-resolution galaxy mergers with mass ratios 1:1 (Mayer et al. 2007), 1:4, and 1:10 (Callegari et al. 2009). We study not only the trajectories and return times of these black holes, but also their detectability as spatially/kinematically offset AGN. We find that the probability of detection of these MBHs is extremely low. The detection of large kinematic offsets requires that the MBH have relative offset velocities Deltav > 600km s-1 at the time of observation. This is unlikely due to (1) the low probability of large recoils to occur from a general-relativistic viewpoint, and (2) the short time scale during which the MBH can sustain large velocities even if the initial kick is high. The large amounts of gas funneled to the center of the host potential during mergers also prevents MBHs from reaching large apocenter distances, which hampers their detection as spatially offset AGN, especially at high redshift when recoil events are expected to be common. Part 2 is dedicated to the formation of massive disk galaxies through N-body + SPH simulations. There, I describe the properties of Eris, the highest resolution cosmological simulation to date of the formation of a Milky Way-like galaxy from z = 90 to z = 0. Eris appears to solve the long-standing problems of mass concentration, which traditionally lead to the formation galaxies with large spheroidal components and small disks. A combination of high-resolution and high star formation threshold was the key to the success of Eris, because stars are only allowed to form at the highest density peaks and therefore feedback is more efficient in removing preferentially low angular momentum gas. Previous simulations tended to over-produce stars in low-density regions, where feedback is ineffective. Eris is in agreement with the Tully-Fischer, and M* - Mhalo relations, matches the observed surface brightness breaks in nearby spirals, is consistent with Sigma SFR - SigmaHI observations in spirals, and agrees with constraints on the hot gas mass abundance in the Galaxy. In addition, Eris' baryon fraction is 30% lower than the universal value, due to star formation driven outflows.

  11. Effects of superpositions of quantum states on quantum isoenergetic cycles: Efficiency and maximum power output

    NASA Astrophysics Data System (ADS)

    Niu, X. Y.; Huang, X. L.; Shang, Y. F.; Wang, X. Y.

    2015-04-01

    Superposition principle plays a crucial role in quantum mechanics, thus its effects on thermodynamics is an interesting topic. Here, the effects of superpositions of quantum states on isoenergetic cycle are studied. We find superposition can improve the heat engine efficiency and release the positive work condition in general case. In the finite time process, we find the efficiency at maximum power output in superposition case is lower than the nonsuperposition case. This efficiency depends on one index of the energy spectrum of the working substance. This result does not mean the superposition discourages the heat engine performance. For fixed efficiency or fixed power, the superposition improves the power or efficiency respectively. These results show how quantum mechanical properties affect the thermodynamical cycle.

  12. Ir Wavelength Dependence Quantum Size Effects in Nb/SiO2 Quantum Wells

    NASA Astrophysics Data System (ADS)

    Villagmez, R.

    This letter deals with the experimental observation of oscillations in the infrared reflectance from Nb ultra-thin films deposited on ?-type SiO2 substrates. P-polarized reflectance (Rp) measurements are made using a tunable p-polarized CO2 waveguide laser using wavelengths between 9.2 and 10.4 ?m. Several Nb/SiO2 quantum wells were specially made by the RF sputtering technique. Tailored thicknesses run between 5.5 and 55 . Because of the strong influence from the chosen substrate, IR reflectivity was fitted to the optical response of our metal-substrate system by using the three-oscillator model and numerical calculations on the basis of the local field calculation for a single metallic quantum well. Although quantum size effects are well studied in semiconductor compounds, there are only a few studies of this effect in metallic films where the present investigation has its most important contribution.

  13. Emergence of integer quantum Hall effect from chaos

    NASA Astrophysics Data System (ADS)

    Tian, Chushun; Chen, Yu; Wang, Jiao

    2016-02-01

    We present an analytic microscopic theory showing that in a large class of spin-1/2 quasiperiodic quantum kicked rotors, a dynamical analog of the integer quantum Hall effect (IQHE) emerges from an intrinsic chaotic structure. Specifically, the inverse of the Planck's quantum (he) and the rotor's energy growth rate mimic the "filling fraction" and the "longitudinal conductivity" in conventional IQHE, respectively, and a hidden quantum number is found to mimic the "quantized Hall conductivity." We show that for an infinite discrete set of critical values of he, the long-time energy growth rate is universal and of order of unity ("metallic" phase), but otherwise vanishes ("insulating" phase). Moreover, the rotor insulating phases are topological, each of which is characterized by a hidden quantum number. This number exhibits universal behavior for small he, i.e., it jumps by unity whenever he decreases, passing through each critical value. This intriguing phenomenon is not triggered by the likes of Landau band filling, well known to be the mechanism for conventional IQHE, and far beyond the canonical Thouless-Kohmoto-Nightingale-Nijs paradigm for quantum Hall transitions. Instead, this dynamical phenomenon is of strong chaos origin; it does not occur when the dynamics is (partially) regular. More precisely, we find that a topological object, similar to the topological theta angle in quantum chromodynamics, emerges from strongly chaotic motion at microscopic scales, and its renormalization gives the hidden quantum number. Our analytic results are confirmed by numerical simulations. Our findings indicate that rich topological quantum phenomena can emerge from chaos and might point to a new direction of study in the interdisciplinary area straddling chaotic dynamics and condensed matter physics. This work is a substantial extension of a short paper published earlier by two of us [Y. Chen and C. Tian, Phys. Rev. Lett. 113, 216802 (2014), 10.1103/PhysRevLett.113.216802].

  14. OPTICS. Quantum spin Hall effect of light.

    PubMed

    Bliokh, Konstantin Y; Smirnova, Daria; Nori, Franco

    2015-06-26

    Maxwell's equations, formulated 150 years ago, ultimately describe properties of light, from classical electromagnetism to quantum and relativistic aspects. The latter ones result in remarkable geometric and topological phenomena related to the spin-1 massless nature of photons. By analyzing fundamental spin properties of Maxwell waves, we show that free-space light exhibits an intrinsic quantum spin Hall effect—surface modes with strong spin-momentum locking. These modes are evanescent waves that form, for example, surface plasmon-polaritons at vacuum-metal interfaces. Our findings illuminate the unusual transverse spin in evanescent waves and explain recent experiments that have demonstrated the transverse spin-direction locking in the excitation of surface optical modes. This deepens our understanding of Maxwell's theory, reveals analogies with topological insulators for electrons, and offers applications for robust spin-directional optical interfaces. PMID:26113717

  15. Angular momentum projection with quantum effects

    SciTech Connect

    Ren, C.; Banerjee, M.K. Department of Astronomy, University of Maryland, College Park, Maryland 20742 )

    1991-04-01

    We have improved a simple and rapid method of calculating expectation values of operators in states of good angular momentum projected from a hedgehog baryon state introduced by Birse {ital et} {ital al}. We have included the contributions of quantum mesons, while in the original method only classical meson fields were included. The method has been applied to models where the mean-field approximation does not include loop terms. Hence, for reasons of consistency, contributions of quantum loops to the matrix elements have been dropped. The symmetry of the hedgehog state under grand reversal (the combined operation of time reversal and {ital e}{sup {ital i}{pi}{bold {cflx I}}}{sub 2}, where {bold {cflx I}} is the isospin operator) introduces remarkable simplification in the calculation of matrix elements of operators which do not contain time derivatives of meson fields. The quantum meson contributions turn out to be 3/2/{l angle}{ital B}{vert bar}{ital {cflx J}}{sup 2}{vert bar}{ital B}{r angle} times the classical meson-field contributions, with {vert bar}{ital B}{r angle} being the hedgehog state. Such operators are encountered in the calculation of nucleon magnetic moments, {ital g}{sub {ital A}}(0) and {ital g}{sub {pi}{ital N}{ital N}}(0)/2{ital M}. Calculation of charge radii involves operators containing time derivatives of meson fields and requires the knowledge of wave functions of quantum mesons. Proper nonperturbative treatment, even though at the tree level, requires that these wave functions describe the motion of the mesons in the potential generated by the baryon. Fortunately, because of the neglect of the loop terms, one needs only the even-parity, grand-spin-1 states which are purely pionic. The Goldberger-Treiman relations, an exact result for the model, serves as a partial test of the method of calculation discussed here.

  16. Entanglement switching via the Kondo effect in triple quantum dots

    NASA Astrophysics Data System (ADS)

    Tooski, S. B.; Bu?ka, Bogdan R.; itko, Rok; Ramak, Anton

    2014-06-01

    We consider a triple quantum dot system in a triangular geometry with one of the dots connected to metallic leads. Using Wilson's numerical renormalization group method, we investigate quantum entanglement and its relation to the thermodynamic and transport properties in the regime where each of the dots is singly occupied on average, but with non-negligible charge fluctuations. It is shown that even in the regime of significant charge fluctuations the formation of the Kondo singlets induces switching between separable and perfectly entangled states. The quantum phase transition between unentangled and entangled states is analyzed quantitatively and the corresponding phase diagram is explained by exactly solvable spin model. In the framework of an effective model we also explain smearing of the entanglement transition for cases when the symmetry of the triple quantum dot system is relaxed.

  17. A quantitative account of quantum effects in liquid water

    SciTech Connect

    Fanourgakis, Georgios S.; Schenter, Gregory K.; Xantheas, Sotiris S.

    2006-10-14

    We report quantum statistical mechanical simulations of liquid water with the TTM2.1-F flexible, polarizable interaction potential for water. The potential is the first representation of the molecular interaction that reproduces the converged Born-Oppenheimer potential energy surface obtained from systematically improvable electronic structure analysis of binding energies of water clusters. Proper quantum statistical simulation of properties allows for a quantitative account of the magnitude of quantum effects in liquid water. We report path integral quantum dynamical simulations of total length of 600 ps with a 0.05 fs time step for a periodic system of 256 molecules. The representation of the quantum effects was achieved using up to 32 replicas per atom. These allow for a quantitative description of the broadening of the radial distribution functions and the corresponding energy shifts in the heat of vaporization. Our best estimate for the enthalpy of the liquid from the results of the quantum simulations is in the range 10.4 ? 10.6 kcal/mol, in agreement with the experimental value of 10.51 kcal/mol. 1Battelle operates PNNL for the USDOE

  18. Quantum dissipative Brownian motion and the Casimir effect

    NASA Astrophysics Data System (ADS)

    Ingold, Gert-Ludwig; Lambrecht, Astrid; Reynaud, Serge

    2009-10-01

    We explore an analogy between the thermodynamics of a free dissipative quantum particle in one dimension and that of an electromagnetic field between two mirrors of finite conductivity. While a free particle isolated from its environment will effectively be in the high-temperature limit for any nonvanishing temperature, a finite coupling to the environment leads to quantum effects ensuring the correct low-temperature behavior. Even then, it is found that under appropriate circumstances the entropy can be a nonmonotonic function of the temperature. Such a scenario with its specific dependence on the ratio of temperature and damping constant also appears for the transverse electric mode in the Casimir effect. The limits of vanishing dissipation for the quantum particle and of infinite conductivity of the mirrors in the Casimir effect both turn out to be noncontinuous.

  19. Effect of quantum statistics on the gravitational weak equivalence principle

    NASA Astrophysics Data System (ADS)

    Mousavi, S. V.; Majumdar, A. S.; Home, D.

    2015-11-01

    We study the effect of quantum statistics on the arrival time distribution of quantum particles computed through the probability current density. It is shown that symmetrization or asymmetrization of the wave function affects the arrival time distribution for even freely propagating particles. In order to investigate the effect of statistics on the weak equivalence principle in quantum mechanics (WEQ), we then compute the mean arrival time for wavepackets in free fall. The violation of WEQ through the effect of statistics on the mass dependence of the mean arrival time is clearly exhibited. We finally evaluate the effect of spin on the violation of WEQ using a different approach by including an explicit spin-dependence in the probability current distribution, and compare it with the approach using particle statistics. Our results show WEQ re-emerges smoothly in the limit of large mass.

  20. Quantum dissipative Brownian motion and the Casimir effect.

    PubMed

    Ingold, Gert-Ludwig; Lambrecht, Astrid; Reynaud, Serge

    2009-10-01

    We explore an analogy between the thermodynamics of a free dissipative quantum particle in one dimension and that of an electromagnetic field between two mirrors of finite conductivity. While a free particle isolated from its environment will effectively be in the high-temperature limit for any nonvanishing temperature, a finite coupling to the environment leads to quantum effects ensuring the correct low-temperature behavior. Even then, it is found that under appropriate circumstances the entropy can be a nonmonotonic function of the temperature. Such a scenario with its specific dependence on the ratio of temperature and damping constant also appears for the transverse electric mode in the Casimir effect. The limits of vanishing dissipation for the quantum particle and of infinite conductivity of the mirrors in the Casimir effect both turn out to be noncontinuous. PMID:19905279

  1. Quantum confinement effects on charge-transfer between PbS quantum dots and 4-mercaptopyridine

    SciTech Connect

    Fu Xiaoqi; Pan Yi; Lombardi, John R.; Wang Xin

    2011-01-14

    We obtain the surface enhanced Raman spectra of 4-mercaptopyridine on lead sulfide (PbS) quantum dots as a function of nanoparticle size and excitation wavelength. The nanoparticle radii are selected to be less than the exciton Bohr radius of PbS, enabling the observation of quantum confinement effects on the spectrum. We utilize the variation of nontotally symmetric modes of both b{sub 1} and b{sub 2} symmetry as compared to the totally symmetric a{sub 1} modes to measure the degree of charge-transfer between the molecule and quantum dot. We find both size dependent and wavelength dependent resonances in the range of these measurements, and attribute them to charge-transfer resonances which are responsible for the Raman enhancement.

  2. Effect of Coulomb correlation on electron transport through a concentric quantum ring-quantum dot structure

    NASA Astrophysics Data System (ADS)

    Chwiej, T.; Kutorasiński, K.

    2010-04-01

    We study transfer of a single-electron through a quantum ring capacitively coupled to the charged quantum dot placed in its center. For this purpose we solve the time-dependent Schrödinger equation for the pair of particles: the electron traveling through the ring and the other carrier confined within the quantum dot. The correlation effects due to the interaction between the charge carriers are described in a numerically exact manner. We find that the amplitude of Aharonov-Bohm oscillations of the transfer probability is significantly affected by the presence of the dot-confined carrier. In particular the Coulomb correlation leads to inelastic scattering. When the inelastic scattering is strong the transmission of electron through the ring is not completely blocked for (n+1/2) magnetic flux quanta.

  3. Confinement and inhomogeneous broadening effects in the quantum oscillatory magnetization of quantum dot ensembles

    NASA Astrophysics Data System (ADS)

    Herzog, F.; Heedt, S.; Goerke, S.; Ibrahim, A.; Rupprecht, B.; Heyn, Ch; Hardtdegen, H.; Schäpers, Th; Wilde, M. A.; Grundler, D.

    2016-02-01

    We report on the magnetization of ensembles of etched quantum dots with a lateral diameter of 460 nm, which we prepared from InGaAs/InP heterostructures. The quantum dots exhibit 1/B-periodic de-Haas–van-Alphen-type oscillations in the magnetization M(B) for external magnetic fields B  >  2 T, measured by torque magnetometry at 0.3 K. We compare the experimental data to model calculations assuming different confinement potentials and including ensemble broadening effects. The comparison shows that a hard wall potential with an edge depletion width of 100 nm explains the magnetic behavior. Beating patterns induced by Rashba spin–orbit interaction (SOI) as measured in unpatterned and nanopatterned InGaAs/InP heterostructures are not observed for the quantum dots. From our model we predict that signatures of SOI in the magnetization could be observed in larger dots in tilted magnetic fields.

  4. Quantum phase transition and underscreened Kondo effect in electron transport through parallel double quantum dots.

    PubMed

    Ding, Guo-Hui; Ye, Fei; Dong, Bing

    2009-11-11

    We investigate electronic transport through a parallel double quantum dot(DQD) system with strong on-site Coulomb interaction and capacitive interdot coupling. By applying the numerical renormalization group(NRG) method, the ground state of the system and the transmission probability at zero temperature have been obtained. For a system of quantum dots with degenerate energy levels and small interdot tunnel coupling, the spin correlations between the DQDs is ferromagnetic and the ground state of the system is a spin-1 triplet state. The linear conductance will reach the unitary limit (2e(2)/h) due to the underscreened Kondo effect at low temperature. As the interdot tunnel coupling increases, there is a quantum phase transition from ferromagnetic to antiferromagnetic spin correlation in DQDs and the linear conductance is strongly suppressed. PMID:21694008

  5. Confinement and inhomogeneous broadening effects in the quantum oscillatory magnetization of quantum dot ensembles.

    PubMed

    Herzog, F; Heedt, S; Goerke, S; Ibrahim, A; Rupprecht, B; Heyn, Ch; Hardtdegen, H; Schpers, Th; Wilde, M A; Grundler, D

    2016-02-01

    We report on the magnetization of ensembles of etched quantum dots with a lateral diameter of 460?nm, which we prepared from InGaAs/InP heterostructures. The quantum dots exhibit 1/B-periodic de-Haas-van-Alphen-type oscillations in the magnetization M(B) for external magnetic fields B??>??2 T, measured by torque magnetometry at 0.3 K. We compare the experimental data to model calculations assuming different confinement potentials and including ensemble broadening effects. The comparison shows that a hard wall potential with an edge depletion width of 100?nm explains the magnetic behavior. Beating patterns induced by Rashba spin-orbit interaction (SOI) as measured in unpatterned and nanopatterned InGaAs/InP heterostructures are not observed for the quantum dots. From our model we predict that signatures of SOI in the magnetization could be observed in larger dots in tilted magnetic fields. PMID:26740509

  6. Heavy-to-light Meson Form Factors at Large Recoil

    SciTech Connect

    Hill, Richard J.; /SLAC

    2005-05-27

    Heavy-to-light meson form factors at large recoil can be described using the same techniques as for hard exclusive processes involving only light hadrons. Two competing mechanisms appear in the large-recoil regime, describing so-called ''soft-overlap'' and ''hard-scattering'' components of the form factors. It is shown how existing experimental data from B and D decays constrain the relative size of these components, and how lattice data can be used to study properties such as the energy scaling laws obeyed by the individual components. Symmetry relations between different form factors (F{sub +}, F{sub 0} and F{sub T}), and between different heavy initial-state mesons (B and D), are derived in the combined heavy-quark and large-recoil limits, and are shown to generalize corresponding relations valid at small recoil. Form factor parameterizations that are consistent with the large-recoil limit are discussed.

  7. Quantum effects in unimolecular reaction dynamics

    SciTech Connect

    Gezelter, J.D.

    1995-12-01

    This work is primarily concerned with the development of models for the quantum dynamics of unimolecular isomerization and photodissociation reactions. We apply the rigorous quantum methodology of a Discrete Variable Representation (DVR) with Absorbing Boundary Conditions (ABC) to these models in an attempt to explain some very surprising results from a series of experiments on vibrationally excited ketene. Within the framework of these models, we are able to identify the experimental signatures of tunneling and dynamical resonances in the energy dependence of the rate of ketene isomerization. Additionally, we investigate the step-like features in the energy dependence of the rate of dissociation of triplet ketene to form {sup 3}B{sub 1} CH{sub 2} + {sup 1}{sigma}{sup +} CO that have been observed experimentally. These calculations provide a link between ab initio calculations of the potential energy surfaces and the experimentally observed dynamics on these surfaces. Additionally, we develop an approximate model for the partitioning of energy in the products of photodissociation reactions of large molecules with appreciable barriers to recombination. In simple bond cleavage reactions like CH{sub 3}COCl {yields} CH{sub 3}CO + Cl, the model does considerably better than other impulsive and statistical models in predicting the energy distribution in the products. We also investigate ways of correcting classical mechanics to include the important quantum mechanical aspects of zero-point energy. The method we investigate is found to introduce a number of undesirable dynamical artifacts including a reduction in the above-threshold rates for simple reactions, and a strong mixing of the chaotic and regular energy domains for some model problems. We conclude by discussing some of the directions for future research in the field of theoretical chemical dynamics.

  8. Fractional quantum Hall effect in Hofstadter butterflies of Dirac fermions

    NASA Astrophysics Data System (ADS)

    Ghazaryan, Areg; Chakraborty, Tapash; Pietiläinen, Pekka

    2015-05-01

    We report on the influence of a periodic potential on the fractional quantum Hall effect (FQHE) states in monolayer graphene. We have shown that for two values of the magnetic flux per unit cell (one-half and one-third flux quantum) an increase of the periodic potential strength results in a closure of the FQHE gap and appearance of gaps due to the periodic potential. In the case of one-half flux quantum this causes a change of the ground state and consequently the change of the momentum of the system in the ground state. While there is also crossing between low-lying energy levels for one-third flux quantum, the ground state does not change with the increase of the periodic potential strength and is always characterized by the same momentum. Finally, it is shown that for one-half flux quantum the emergent gaps are due entirely to the electron-electron interaction, whereas for the one-third flux quantum per unit cell these are due to both non-interacting electrons (Hofstadter butterfly pattern) and the electron-electron interaction.

  9. Phenomenology of effective geometries from quantum gravity

    NASA Astrophysics Data System (ADS)

    Torrom, Ricardo Gallego; Letizia, Marco; Liberati, Stefano

    2015-12-01

    In a recent paper [M. Assanioussi, A. Dapor, and J. Lewandowski, Phys. Lett. B 751, 302 (2015)] a general mechanism for the emergence of cosmological spacetime geometry from a quantum gravity setting was devised and a departure from standard dispersion relations for an elementary particle was predicted. We elaborate here on this approach extending the results obtained in that paper and showing that generically such a framework will not lead to higher order modified dispersion relations in the matter sector. Furthermore, we shall discuss possible phenomenological constraints to this scenario showing that spacetime will have to be classical to a very high degree by now in order to be consistent with current observations.

  10. Quantum dust magnetosonic waves with spin and exchange correlation effects

    NASA Astrophysics Data System (ADS)

    Maroof, R.; Mushtaq, A.; Qamar, A.

    2016-01-01

    Dust magnetosonic waves are studied in degenerate dusty plasmas with spin and exchange correlation effects. Using the fluid equations of magnetoplasma with quantum corrections due to the Bohm potential, temperature degeneracy, spin magnetization energy, and exchange correlation, a generalized dispersion relation is derived. Spin effects are incorporated via spin force and macroscopic spin magnetization current. The exchange-correlation potentials are used, based on the adiabatic local-density approximation, and can be described as a function of the electron density. For three different values of angle, the dispersion relation is reduced to three different modes under the low frequency magnetohydrodynamic assumptions. It is found that the effects of quantum corrections in the presence of dust concentration significantly modify the dispersive properties of these modes. The results are useful for understanding numerous collective phenomena in quantum plasmas, such as those in compact astrophysical objects (e.g., the cores of white dwarf stars and giant planets) and in plasma-assisted nanotechnology (e.g., quantum diodes, quantum free-electron lasers, etc.).

  11. Quantum Zeno effect for a free-moving particle

    NASA Astrophysics Data System (ADS)

    Porras, Miguel A.; Luis, Alfredo; Gonzalo, Isabel

    2014-12-01

    Although the quantum Zeno effect takes its name from Zeno's arrow paradox, the effect of frequently observing the position of a freely moving particle on its motion has not been analyzed in detail in the frame of standard quantum mechanics. We study the evolution of a moving free particle while monitoring whether it lingers in a given region of space, and explain the dependence of the lingering probability on the frequency of the measurements and the initial momentum of the particle. Stopping the particle entails the emergence of Schrdinger cat states during the observed evolution, closely connected to the high-order diffraction modes in Fabry-Prot optical resonators.

  12. Quantum interference effects in chemical vapor deposited graphene

    NASA Astrophysics Data System (ADS)

    Kim, Nam-Hee; Shin, Yun-Sok; Park, Serin; Kim, Hong-Seok; Lee, Jun Sung; Ahn, Chi Won; Lee, Jeong-O.; Doh, Yong-Joo

    2016-01-01

    We report several quantum interference effects in graphene grown by chemical vapor deposition. A crossover between weak localization and weak antilocalization effects is observed when varying the gate voltage and we discuss the underlying scattering mechanisms. The characteristic length scale for phase coherence is compared with that estimated from universal conductance fluctuations in the microporeformed graphene sample. These extensive temperature- and gate-dependent measurements of the intervalley and intravalley scattering lengths provide important and useful insight for the macroscopic applications of graphene-based quantum devices.

  13. Observation of the Kondo effect in a quadruple quantum dot

    NASA Astrophysics Data System (ADS)

    Shang, Runan; Li, Hai-Ou; Cao, Gang; Yu, Guodong; Xiao, Ming; Tu, Tao; Guo, Guang-Can; Jiang, Hongwen; Chang, A. M.; Guo, Guo-Ping

    2015-06-01

    We investigate the Kondo effect in a quadruple-quantum-dot device of coupled double quantum dots (DQDs), which simultaneously contain intra-DQD and inter-DQD coupling. A variety of novel behaviors are observed. The differential conductance dI/dV is measured in the upper DQDs as a function of source drain bias. It is found to exhibit multiple peaks, including a zero-bias peak, where the number of peaks exceeds five. Alternatively, tuning the lower DQDs yielded regions of four peaks. In addition, a Kondo effect switcher is demonstrated, using the lower DQDs as the controller.

  14. Topological insulators in silicene: Quantum hall, quantum spin hall and quantum anomalous hall effects

    SciTech Connect

    Ezawa, Motohiko

    2013-12-04

    Silicene is a monolayer of silicon atoms forming a two-dimensional honeycomb lattice, which shares almost every remarkable property with graphene. The low energy dynamics is described by Dirac electrons, but they are massive due to relatively large spin-orbit interactions. I will explain the following properties of silicene: 1) The band structure is controllable by applying an electric field. 2) Silicene undergoes a phase transition from a topological insulator to a band insulator by applying external electric field. 3) The topological phase transition can be detected experimentally by way of diamagnetism. 4) There is a novel valley-spin selection rules revealed by way of photon absorption. 5) Silicene yields a remarkably many phases such as quantum anomalous Hall phase and valley polarized metal when the exchange field is additionally introduced. 6) A silicon nanotubes can be used to convey spin currents under an electric field.

  15. Topological insulators in silicene: Quantum hall, quantum spin hall and quantum anomalous hall effects

    NASA Astrophysics Data System (ADS)

    Ezawa, Motohiko

    2013-12-01

    Silicene is a monolayer of silicon atoms forming a two-dimensional honeycomb lattice, which shares almost every remarkable property with graphene. The low energy dynamics is described by Dirac electrons, but they are massive due to relatively large spin-orbit interactions. I will explain the following properties of silicene: 1) The band structure is controllable by applying an electric field. 2) Silicene undergoes a phase transition from a topological insulator to a band insulator by applying external electric field. 3) The topological phase transition can be detected experimentally by way of diamagnetism. 4) There is a novel valley-spin selection rules revealed by way of photon absorption. 5) Silicene yields a remarkably many phases such as quantum anomalous Hall phase and valley polarized metal when the exchange field is additionally introduced. 6) A silicon nanotubes can be used to convey spin currents under an electric field.

  16. Microscopic Properties of the Fractional Quantum Hall Effect

    NASA Astrophysics Data System (ADS)

    Kou, Angela

    The fractional quantum Hall effect occurs when an extremely clean 2-dimensional fermion gas is subject to a magnetic field. This simple set of circumstances creates phenomena, such as edge reconstruction and fractional statistics, that remain subjects of experimental study 30 years after the discovery of the fractional quantum Hall effect. This thesis investigates the properties of excitations of the fractional quantum Hall effect. The first set of experiments studies the interaction between fractional quantum Hall quasiparticles and nuclei in a quantum point contact (QPC). Following the application of a DC bias, fractional plateaus in the QPC shift symmetrically about half filling of the lowest Landau level, nu = 1/3, suggesting an interpretation in terms of composite fermions. Mapping the effects from the integer to fractional regimes extends the composite fermion picture to include hyperfine coupling. The second set of experiments studies the tunneling of quasiparticles through an antidot in the integer and fractional quantum Hall effect. In the integer regime, we conclude that oscillations are of the Coulomb type from the scaling of magnetic field period with the number of edges bound to the antidot. Generalizing this picture to the fractional regime, we find (based on magnetic field and gate-voltage periods) at nu = 2/3 a tunneling charge of (2/3)e and a single charged edge. Further unpublished data related to this experiment as well as alternative theoretical explanations are also presented. The third set of experiments investigates the properties of the fractional quantum Hall effect in the lowest Landau level of bilayer graphene using a scanning single-electron transistor. We observe a sequence of states which breaks particle-hole symmetry and instead obeys a nu ? nu + 2 symmetry. This asymmetry highlights the importance of the orbital degeneracy for many-body states in bilayer graphene. The fourth set of experiments investigates the coupling between microwaves and the fractional quantum Hall effect. Reflectometry is used to investigate bulk properties of samples with different electron densities. We observe large changes in the amplitude of the reflected signal at each integer filling factor as well as changes in the capacitance of the system.

  17. Effects of reservoir squeezing on quantum systems and work extraction

    NASA Astrophysics Data System (ADS)

    Huang, X. L.; Wang, Tao; Yi, X. X.

    2012-11-01

    We establish a quantum Otto engine cycle in which the working substance contacts with squeezed reservoirs during the two quantum isochoric processes. We consider two working substances: (1) a qubit and (2) two coupled qubits. Due to the effects of squeezing, the working substance can be heated to a higher effective temperature, which leads to many interesting features different from the ordinary ones, such as (1) for the qubit as working substance, if we choose the squeezed parameters properly, the positive work can be exported even when THquantum fuel is more efficient than the classical one.

  18. Effects of reservoir squeezing on quantum systems and work extraction.

    PubMed

    Huang, X L; Wang, Tao; Yi, X X

    2012-11-01

    We establish a quantum Otto engine cycle in which the working substance contacts with squeezed reservoirs during the two quantum isochoric processes. We consider two working substances: (1) a qubit and (2) two coupled qubits. Due to the effects of squeezing, the working substance can be heated to a higher effective temperature, which leads to many interesting features different from the ordinary ones, such as (1) for the qubit as working substance, if we choose the squeezed parameters properly, the positive work can be exported even when T(H) quantum fuel is more efficient than the classical one. PMID:23214736

  19. Stark shift effects in rectangular and graded gap quantum wells

    NASA Astrophysics Data System (ADS)

    Vlaev, S. J.; Miteva, A. M.; Contreras-Solorio, D. A.; Velasco, V. R.

    1999-04-01

    We study the Stark effect in rectangular quantum wells and in quantum wells with linear variation of the composition. The energies of the bound electronic states, the transition energies and their Stark shifts are calculated when a longitudinal electric field is applied. The spatial overlap of the electron and hole states and the intensity of the main optical transitions are considered, and their dependence on the electric field strength is discussed. We compare the Stark effect characteristics of the rectangular and graded composition quantum wells. Numerical calculations are performed within the framework of a semi-empirical sp 3s? tight-binding model, the virtual crystal approximation and the surface Green function matching method. A comparison between the theoretical results and the experimental data available for these systems is made, and a critical discussion is presented.

  20. Bound polaron in a quantum pseudodot under Rashba effect

    NASA Astrophysics Data System (ADS)

    Khordad, R.

    2015-05-01

    In the present work, the influence of Rashba effect on bound polaron in a quantum pseudodot is studied. Using the Lee-Low-Pines unitary transformation method and the Pekar type variational procedure, we have derived an expression for the bound polaron ground state energy. The ground state energy as functions of the wave vector, the electron-phonon coupling strength, and quantum confinement size is obtained by considering different Coulomb bound potentials. It is found that (i) the ground state energy is decreased with raising the Coulomb bound potential, the electron-phonon coupling strength, and quantum confinement size. (ii) The ground state energy increases when the wave vector is increasing. (iii) The ground state energy splits into two branches (spin-up and spin-down) due to the Rashba effect.

  1. Loss of coherence and memory effects in quantum dynamics Loss of coherence and memory effects in quantum dynamics

    NASA Astrophysics Data System (ADS)

    Benatti, Fabio; Floreanini, Roberto; Scholes, Greg

    2012-08-01

    The last years have witnessed fast growing developments in the use of quantum mechanics in technology-oriented and information-related fields, especially in metrology, in the developments of nano-devices and in understanding highly efficient transport processes. The consequent theoretical and experimental outcomes are now driving new experimental tests of quantum mechanical effects with unprecedented accuracies that carry with themselves the concrete possibility of novel technological spin-offs. Indeed, the manifold advances in quantum optics, atom and ion manipulations, spintronics and nano-technologies are allowing direct experimental verifications of new ideas and their applications to a large variety of fields. All of these activities have revitalized interest in quantum mechanics and created a unique framework in which theoretical and experimental physics have become fruitfully tangled with information theory, computer, material and life sciences. This special issue aims to provide an overview of what is currently being pursued in the field and of what kind of theoretical reference frame is being developed together with the experimental and theoretical results. It consists of three sections: 1. Memory effects in quantum dynamics and quantum channels 2. Driven open quantum systems 3. Experiments concerning quantum coherence and/or decoherence The first two sections are theoretical and concerned with open quantum systems. In all of the above mentioned topics, the presence of an external environment needs to be taken into account, possibly in the presence of external controls and/or forcing, leading to driven open quantum systems. The open system paradigm has proven to be central in the analysis and understanding of many basic issues of quantum mechanics, such as the measurement problem, quantum communication and coherence, as well as for an ever growing number of applications. The theory is, however, well-settled only when the so-called Markovian or memoryless, approximation applies. When strong coupling or long environmental relaxation times make memory effects important for a realistic description of the dynamics, new strategies are asked for and the assessment of the general structure of non-Markovian dynamical equations for realistic systems is a crucial issue. The impact of quantum phenomena such as coherence and entanglement in biology has recently started to be considered as a possible source of the high efficiency of certain biological mechanisms, including e.g. light harvesting in photosynthesis and enzyme catalysis. In this effort, the relatively unknown territory of driven open quantum systems is being explored from various directions, with special attention to the creation and stability of coherent structures away from thermal equilibrium. These investigations are likely to advance our understanding of the scope and role of quantum mechanics in living systems; at the same time they provide new ideas for the developments of next generations of devices implementing highly efficient energy harvesting and conversion. The third section concerns experimental studies that are currently being pursued. Multidimensional nonlinear spectroscopy, in particular, has played an important role in enabling experimental detection of the signatures of coherence. Recent remarkable results suggest that coherenceboth electronic and vibrationalsurvive for substantial timescales even in complex biological systems. The papers reported in this issue describe work at the forefront of this field, where researchers are seeking a detailed understanding of the experimental signatures of coherence and its implications for light-induced processes in biology and chemistry.

  2. Effects of quantum coherence in metalloprotein electron transfer

    NASA Astrophysics Data System (ADS)

    Dorner, Ross; Goold, John; Heaney, Libby; Farrow, Tristan; Vedral, Vlatko

    2012-09-01

    Many intramolecular electron transfer (ET) reactions in biology are mediated by metal centers in proteins. This process is commonly described by a model of diffusive hopping according to the semiclassical theories of Marcus and Hopfield. However, recent studies have raised the possibility that nontrivial quantum mechanical effects play a functioning role in certain biomolecular processes. Here, we investigate the potential effects of quantum coherence in biological ET by extending the semiclassical model to allow for the possibility of quantum coherent phenomena using a quantum master equation based on the Holstein Hamiltonian. We test the model on the structurally defined chain of seven iron-sulfur clusters in nicotinamide adenine dinucleotide plus hydrogen:ubiquinone oxidoreductase (complex I), a crucial respiratory enzyme and one of the longest chains of metal centers in biology. Using experimental parameters where possible, we find that, in limited circumstances, a small quantum mechanical contribution can provide a marked increase in the ET rate above the semiclassical diffusive-hopping rate. Under typical biological conditions, our model reduces to well-known diffusive behavior.

  3. The Observability of Recoiling Black Holes as Offset Quasars

    NASA Astrophysics Data System (ADS)

    Blecha, Laura

    2014-10-01

    The merger of two supermassive black holes (SMBHs) imparts a gravitational-wave (GW) recoil kick to the remnant SMBH, and in extreme cases SMBHs may be ejected from their host galaxies. An accreting, recoiling SMBH may be observable as a spatially or kinematically offset quasar. Prior to the advent of a space-based GW observatory, offset quasars may offer the best evidence of recent SMBH mergers. Indeed, promising candidates have already been identified. However, systematic searches for recoils are hampered by large uncertainties, including how often and in which host galaxies offset quasars should be observable, and whether BH spin alignment prior to merger is efficient at suppressing large recoils. Motivated by this, we have developed a model for recoiling quasars in a cosmological framework, utilizing information about the progenitor galaxies from cosmological hydrodynamic simulations. Varying degrees of BH spin alignment are considered. We find that the observability of offset quasars, and their preferred host galaxies, depend strongly on the efficiency of pre-merger spin alignment, with promising indications that discoveries of recoils could distinguish between at least the extreme limits of spin alignment models. These findings will inform the design of dedicated searches for recoiling quasars.

  4. InAs/GaSb quantum wells: quantum spin Hall effect and topological superconductivity

    NASA Astrophysics Data System (ADS)

    Sitte, Matthias; Everschor-Sitte, Karin; MacDonald, Allan

    2015-03-01

    Topological insulators have attracted a great deal of attention as a new quantum state of matter in the last decade. The first realizations of 2D TIs were HgTe/CdTe quantum well heterostructures, but in recent years another class of semiconductor heterostructures -- namely InAs/GaSb quantum wells -- was shown to yield 2D TIs as well. Compared to the HgTe/CdTe-based systems they have many advantages, most prominently a continuously tunable band structure via external electric fields and stronger proximity coupling to superconductors. We perform empirical tight-binding calculations on these systems to study how topological properties are changed by varying external control parameters such as electric fields or well thicknesses. Since proximity coupling of a 2D TI and an ordinary s-wave superconductor gives rise to 1D topological superconductivity, these systems also support Majorana fermions as non-local excitations. We will present preliminary results on the proximity effects when InAs/GaSb quantum wells are coupled to a superconductor.

  5. The Quantum Spin Hall Effect: Theory and Experiment

    SciTech Connect

    Konig, Markus; Buhmann, Hartmut; Molenkamp, Laurens W.; Hughes, Taylor L.; Liu, Chao-Xing; Qi, Xiao-Liang; Zhang, Shou-Cheng; /Stanford U., Phys. Dept.

    2010-03-19

    The search for topologically non-trivial states of matter has become an important goal for condensed matter physics. Recently, a new class of topological insulators has been proposed. These topological insulators have an insulating gap in the bulk, but have topologically protected edge states due to the time reversal symmetry. In two dimensions the helical edge states give rise to the quantum spin Hall (QSH) effect, in the absence of any external magnetic field. Here we review a recent theory which predicts that the QSH state can be realized in HgTe/CdTe semiconductor quantum wells. By varying the thickness of the quantum well, the band structure changes from a normal to an 'inverted' type at a critical thickness d{sub c}. We present an analytical solution of the helical edge states and explicitly demonstrate their topological stability. We also review the recent experimental observation of the QSH state in HgTe/(Hg,Cd)Te quantum wells. We review both the fabrication of the sample and the experimental setup. For thin quantum wells with well width d{sub QW} < 6.3 nm, the insulating regime shows the conventional behavior of vanishingly small conductance at low temperature. However, for thicker quantum wells (d{sub QW} > 6.3 nm), the nominally insulating regime shows a plateau of residual conductance close to 2e{sup 2}/h. The residual conductance is independent of the sample width, indicating that it is caused by edge states. Furthermore, the residual conductance is destroyed by a small external magnetic field. The quantum phase transition at the critical thickness, d{sub c} = 6.3 nm, is also independently determined from the occurrence of a magnetic field induced insulator to metal transition.

  6. Linear and nonlinear electrostatic modes in a strongly coupled quantum plasma

    SciTech Connect

    Ghosh, Samiran; Chakrabarti, Nikhil

    2012-07-15

    The properties of linear and nonlinear electrostatic waves in a strongly coupled electron-ion quantum plasma are investigated. In this study, the inertialess electrons are degenerate, while non-degenerate inertial ions are strongly correlated. The ion dynamics is governed by the continuity and the generalized viscoelastic momentum equations. The quantum forces associated with the quantum statistical pressure and the quantum recoil effect act on the degenerate electron fluid, whereas strong ion correlation effects are embedded in generalized viscoelastic momentum equation through the viscoelastic relaxation of ion correlations and ion fluid shear viscosities. Hence, the spectra of linear electrostatic modes are significantly affected by the strong ion coupling effect. In the weakly nonlinear limit, due to ion-ion correlations, the quantum plasma supports a dispersive shock wave, the dynamics of which is governed by the Korteweg-de Vries Burgers' equation. For a particular value of the quantum recoil effect, only monotonic shock structure is observed. Possible applications of our investigation are briefly mentioned.

  7. Effect of classical noise on the geometric quantum phase

    SciTech Connect

    Hou, Ji-Xuan

    2007-02-15

    We consider the effect of classical noise applied to the geometric quantum phase of a spin 1/2 in a revolving magnetic field. The Berry phase shows some sensitivity to the noise because the Bloch vector cannot return to its original direction, and the variance caused by noise is proportional to the evolution time.

  8. Macroscopic quantum tunneling and the 'cosmic' Josephson effect

    SciTech Connect

    Barone, A.; Gasperini, M.; Rotoli, G.

    2010-10-15

    We discuss the possible influence of a cosmic magnetic field on the macroscopic quantum tunneling process associated, in a cosmological context, to the decay of the 'false vacuum'. We find a close analogy with the effects of an external magnetic field applied to a Josephson junction in the context of low-temperature/high-temperature superconducting devices.

  9. Effective action for a quantum scalar field in warped spaces

    NASA Astrophysics Data System (ADS)

    Hoff da Silva, J. M.; Mendona, E. L.; Scatena, E.

    2015-11-01

    We investigate the one-loop corrections, at zero as well as finite temperature, of a scalar field taking place in a braneworld motivated warped background. After to reach a well-defined problem, we calculate the effective action with the corresponding quantum corrections to each case.

  10. Quantum gravity effect in torsion driven inflation and CP violation

    NASA Astrophysics Data System (ADS)

    Choudhury, Sayantan; Pal, Barun Kumar; Basu, Banasri; Bandyopadhyay, Pratul

    2015-10-01

    We have derived an effective potential for inflationary scenario from torsion and quantum gravity correction in terms of the scalar field hidden in torsion. A strict bound on the CP violating ? parameter, O(1{0}^{-10})

  11. Low energy theorems of quantum gravity from effective field theory

    NASA Astrophysics Data System (ADS)

    Donoghue, John F.; Holstein, Barry R.

    2015-10-01

    In this survey, we review some of the low energy quantum predictions of general relativity which are independent of details of the yet unknown high-energy completion of the gravitational interaction. Such predictions can be extracted using the techniques of effective field theory.

  12. Local field effects and metamaterials based on colloidal quantum dots

    NASA Astrophysics Data System (ADS)

    Porvatkina, O. V.; Tishchenko, A. A.; Strikhanov, M. N.

    2015-11-01

    Metamaterials are composite structures that exhibit interesting and unusual properties, e.g. negative refractive index. In this article we consider metamaterials based on colloidal quantum dots (CQDs). We investigate these structures taking into account the local field effects and theoretically analyze expressions for permittivity and permeability of metamaterials based on CdSe CQDs. We obtain inequality describing the conditions when material with definite concentration of CQDs is metamaterial. Also we investigate how the values of dielectric polarizability and magnetic polarizability of CQDs depend on the dots radius and properties the material the quantum dots are made of.

  13. Quantum effects in the dynamics of deeply supercooled water.

    PubMed

    Agapov, A L; Kolesnikov, A I; Novikov, V N; Richert, R; Sokolov, A P

    2015-02-01

    Despite its simple chemical structure, water remains one of the most puzzling liquids with many anomalies at low temperatures. Combining neutron scattering and dielectric relaxation spectroscopy, we show that quantum fluctuations are not negligible in deeply supercooled water. Our dielectric measurements reveal the anomalously weak temperature dependence of structural relaxation in vapor-deposited water close to the glass transition temperature T(g)?136K. We demonstrate that this anomalous behavior can be explained well by quantum effects. These results have significant implications for our understanding of water dynamics. PMID:25768510

  14. Analog model for quantum gravity effects: phonons in random fluids.

    PubMed

    Krein, G; Menezes, G; Svaiter, N F

    2010-09-24

    We describe an analog model for quantum gravity effects in condensed matter physics. The situation discussed is that of phonons propagating in a fluid with a random velocity wave equation. We consider that there are random fluctuations in the reciprocal of the bulk modulus of the system and study free phonons in the presence of Gaussian colored noise with zero mean. We show that, in this model, after performing the random averages over the noise function a free conventional scalar quantum field theory describing free phonons becomes a self-interacting model. PMID:21230759

  15. Nuclear Quantum Vibrational Effects in Shock Hugoniot Temperatures

    SciTech Connect

    Goldman, N; Reed, E; Fried, L E

    2009-07-23

    We present a straightforward method for the inclusion of quantum nuclear vibrational effects in molecular dynamics calculations of shock Hugoniot temperatures. Using a Grueneisen equation of state and a quasiharmonic approximation to the vibrational energies, we derive a simple, post-processing method for calculation of the quantum corrected Hugoniot temperatures. We have used our novel technique on ab initio simulations of shock compressed water. Our results indicate significantly closer agreement with all available experimental temperature data. Our formalism and technique can be easily applied to a number of different shock compressed molecular liquids or solids.

  16. Effect of structural disorder on quantum oscillations in graphite

    NASA Astrophysics Data System (ADS)

    Camargo, B. C.; Kopelevich, Y.; Usher, A.; Hubbard, S. B.

    2016-01-01

    We have studied the effect of structural disorder on the de Haas van Alphen and Shubnikov de Haas quantum oscillations measured in natural, Kish, and highly oriented pyrolytic graphite samples at temperatures down to 30 mK and at magnetic fields up to 14 T. The measurements were performed on different samples characterized by means of x-ray diffractometry, transmission electron microscopy, and atomic-force microscopy techniques. Our results reveal a correlation between the amplitude of quantum oscillations and the sample surface roughness.

  17. A holographic model for the fractional quantum Hall effect

    NASA Astrophysics Data System (ADS)

    Lippert, Matthew; Meyer, Ren; Taliotis, Anastasios

    2015-01-01

    Experimental data for fractional quantum Hall systems can to a large extent be explained by assuming the existence of a ?0(2) modular symmetry group commuting with the renormalization group flow and hence mapping different phases of two-dimensional electron gases into each other. Based on this insight, we construct a phenomenological holographic model which captures many features of the fractional quantum Hall effect. Using an -invariant Einstein-Maxwell-axio-dilaton theory capturing the important modular transformation properties of quantum Hall physics, we find dyonic diatonic black hole solutions which are gapped and have a Hall conductivity equal to the filling fraction, as expected for quantum Hall states. We also provide several technical results on the general behavior of the gauge field fluctuations around these dyonic dilatonic black hole solutions: we specify a sufficient criterion for IR normalizability of the fluctuations, demonstrate the preservation of the gap under the action, and prove that the singularity of the fluctuation problem in the presence of a magnetic field is an accessory singularity. We finish with a preliminary investigation of the possible IR scaling solutions of our model and some speculations on how they could be important for the observed universality of quantum Hall transitions.

  18. On the Convergence in Effective Loop Quantum Cosmology

    SciTech Connect

    Corichi, Alejandro; Vukasinac, Tatjana; Zapata, Jose Antonio

    2010-07-12

    In Loop Quantum Cosmology (LQC) there is a discreteness parameter {lambda}, that has been heuristically associated to a fundamental granularity of quantum geometry. It is also possible to consider {lambda} as a regulator in the same spirit as that used in lattice field theory, where it specifies a regular lattice in the real line. A particular quantization of the k = 0 FLRW loop cosmological model yields a completely solvable model, known as solvable loop quantum cosmology(sLQC). In this contribution, we consider effective classical theories motivated by sLQC and study their {lambda}-dependence, with a special interest on the limit {lambda}{yields}0 and the role of the evolution parameter in the convergence of such limit.

  19. Macroscopic quantum effects observed in Mssbauer spectra of antiferromagnetic nanoparticles

    NASA Astrophysics Data System (ADS)

    Chuev, Mikhail A.

    2014-04-01

    The 57Fe Mssbauer spectra of antiferromagnetic nanoparticles have been measured for almost half a century and often displayed a specific (non-superparamagnetic) temperature evolution of the spectral shape which looks like a quantum superposition of well-resolved magnetic hyperfine structure and single line or quadrupolar doublet of lines with the temperature-dependent partial spectral areas. We have developed a quantum-mechanical model for describing thermodynamic characteristics of an ensemble of ideal and "uncompensated" antiferromagnetic nanoparticles with uniaxial magnetic anisotropy in the first approximation of slowly relaxing macrospins of magnetic sublattices. This model allows one to qualitatively describe the macroscopic quantum effects observed in the Mssbauer spectra and to clarify principally the difference in thermodynamic properties of ferromagnetic and antiferromagnetic particles revealed in spectroscopic measurements.

  20. Coupling effect of quantum wells on band structure

    NASA Astrophysics Data System (ADS)

    Jie, Chen; Weiyou, Zeng

    2015-10-01

    The coupling effects of quantum wells on band structure are numerically investigated by using the Matlab programming language. In a one dimensional finite quantum well with the potential barrier V0, the calculation is performed by increasing the number of inserted barriers with the same height Vb, and by, respectively, varying the thickness ratio of separated wells to inserted barriers and the height ratio of Vb to V0. Our calculations show that coupling is strongly influenced by the above parameters of the inserted barriers and wells. When these variables change, the width of the energy bands and gaps can be tuned. Our investigation shows that it is possible for quantum wells to achieve the desired width of the bands and gaps.

  1. The quantum pinch effect in semiconducting quantum wires: A bird’s-eye view

    NASA Astrophysics Data System (ADS)

    Kushwaha, Manvir S.

    2016-01-01

    Those who measure success with culmination do not seem to be aware that life is a journey not a destination. This spirit is best reflected in the unceasing failures in efforts for solving the problem of controlled thermonuclear fusion for even the simplest pinches for over decades; and the nature keeps us challenging with examples. However, these efforts have permitted researchers the obtention of a dense plasma with a lifetime that, albeit short, is sufficient to study the physics of the pinch effect, to create methods of plasma diagnostics, and to develop a modern theory of plasma processes. Most importantly, they have impregnated the solid state plasmas, particularly the electron-hole plasmas in semiconductors, which do not suffer from the issues related with the confinement and which have demonstrated their potential not only for the fundamental physics but also for the device physics. Here, we report on a two-component, cylindrical, quasi-one-dimensional quantum plasma subjected to a radial confining harmonic potential and an applied magnetic field in the symmetric gauge. It is demonstrated that such a system, as can be realized in semiconducting quantum wires, offers an excellent medium for observing the quantum pinch effect at low temperatures. An exact analytical solution of the problem allows us to make significant observations: Surprisingly, in contrast to the classical pinch effect, the particle density as well as the current density display a determinable maximum before attaining a minimum at the surface of the quantum wire. The effect will persist as long as the equilibrium pair density is sustained. Therefore, the technological promise that emerges is the route to the precise electronic devices that will control the particle beams at the nanoscale.

  2. Quantification of 39Ar recoil ejection from GA1550 biotite during neutron irradiation as a function of grain dimensions

    NASA Astrophysics Data System (ADS)

    Paine, Jeffrey H.; Nomade, Sébastien; Renne, Paul R.

    2006-03-01

    This study presents the first measurement of 39Ar recoil ejection loss from individual, dimensionally characterized mineral grains due to neutron irradiation, and reveals the extent to which this recoil loss is problematic for 40Ar/ 39Ar dating. Using the well-characterized biotite standard GA1550, known to have between grain reproducibility of 40Ar*/ 39Ar K of order 0.1%, we measured the thicknesses (3-210 μm) and surface areas (0.07-0.90 mm 2) of 159 grains selected to span the dimensional range represented in the aliquot. Thinner grains with high surface area/volume (SA/V) reveal elevated 40Ar/ 39Ar, as much as 26% higher than thicker grains expected to suffer proportionately negligible depletion. Although the thinner grains yield intrinsically less precise measurements due to small 39Ar ion beams, a regular decrease in net recoil loss with increasing biotite grain thickness is clear for grains thinner than ca. 50 μm. Grains thicker than 50 μm reveal essentially no 39Ar loss within analytical uncertainties. The measured 39Ar loss spectrum is significantly higher than predicted by previous modeling approaches. These results suggest a practical threshold of ca. 50 μm grain thickness for biotites, and probably other phyllosilicates, irradiated with 235U fission spectrum neutrons in order to avoid recoil artifacts. Poor agreement between our data and simulation results indicates that recoil displacement models should be revisited in order to resolve the discrepancy. Further empirical work to determine the recoil loss of 39Ar in other minerals is important not only for routine age measurements, but also to shed more light on the role of recoil in multi-diffusion domain theory and other thermochronologic applications exploiting variable diffusion radii and/or grain size effects.

  3. Mesoscopic effects in quantum phases of ultracold quantum gases in optical lattices

    SciTech Connect

    Carr, L. D.; Schirmer, D. G.; Wall, M. L.; Brown, R. C.; Williams, J. E.; Clark, Charles W.

    2010-01-15

    We present a wide array of quantum measures on numerical solutions of one-dimensional Bose- and Fermi-Hubbard Hamiltonians for finite-size systems with open boundary conditions. Finite-size effects are highly relevant to ultracold quantum gases in optical lattices, where an external trap creates smaller effective regions in the form of the celebrated 'wedding cake' structure and the local density approximation is often not applicable. Specifically, for the Bose-Hubbard Hamiltonian we calculate number, quantum depletion, local von Neumann entropy, generalized entanglement or Q measure, fidelity, and fidelity susceptibility; for the Fermi-Hubbard Hamiltonian we also calculate the pairing correlations, magnetization, charge-density correlations, and antiferromagnetic structure factor. Our numerical method is imaginary time propagation via time-evolving block decimation. As part of our study we provide a careful comparison of canonical versus grand canonical ensembles and Gutzwiller versus entangled simulations. The most striking effect of finite size occurs for bosons: we observe a strong blurring of the tips of the Mott lobes accompanied by higher depletion, and show how the location of the first Mott lobe tip approaches the thermodynamic value as a function of system size.

  4. Quantum confined stark effect in wide parabolic quantum wells: real density matrix approach

    NASA Astrophysics Data System (ADS)

    Zielińska-Raczyńska, Sylwia; Czajkowski, Gerard; Ziemkiewicz, David

    2015-12-01

    We show how to compute the optical functions of wide parabolic quantum wells (WPQWs) exposed to uniform electric F applied in the growth direction, in the excitonic energy region. The effect of the coherence between the electron-hole pair and the electromagnetic field of the propagating wave including the electron-hole screened Coulomb potential is adopted, and the valence band structure is taken into account in the cylindrical approximation. The role of the interaction potential and of the applied electric field, which mix the energy states according to different quantum numbers and create symmetry forbidden transitions, is stressed. We use the real density matrix approach (RDMA) and an effective e-h potential, which enable to derive analytical expressions for the WPQWs electrooptical functions. Choosing the susceptibility, we performed numerical calculations appropriate to a GaAs/GaAlAs WPQWs. We have obtained a red shift of the absorption maxima (quantum confined Stark effect), asymmetric upon the change of the direction of the applied field ( F → - F), parabolic for the ground state and strongly dependent on the confinement parameters (the QWs sizes), changes in the oscillator strengths, and new peaks related to the states with different parity for electron and hole.

  5. Quantum mechanical effects of topological origin

    NASA Technical Reports Server (NTRS)

    Duru, I. H.

    1993-01-01

    Following a brief review of the original Casimir and Aharonov-Bohm effects, some other effects of similar natures are mentioned. A Casimir interaction between AB fluxes is presented. Possible realizations of the Casimir effects for massive charged fields in solid state structures and a new AB effect for photons are suggested.

  6. Magnitude of quantum effects in classical spin ices

    NASA Astrophysics Data System (ADS)

    Rau, Jeffrey G.; Gingras, Michel J. P.

    2015-10-01

    The pyrochlore spin ice compounds Dy2Ti2O7 and Ho2Ti2O7 are well described by classical Ising models down to low temperatures. Given the empirical success of this description, the question of the importance of quantum effects in these materials has been mostly ignored. We show that the common wisdom that the strictly Ising moments of isolated Dy3+ and Ho3+ ions imply Ising interactions is too naïve; a more complex argument is needed to explain the close agreement between theory and experiment. From a microscopic picture of the interactions in rare-earth oxides, we show that the high-rank multipolar interactions needed to induce quantum effects in these two materials are generated only very weakly by superexchange. Using this framework, we formulate an estimate of the scale of quantum effects in Ho2Ti2O7 and Dy2Ti2O7 , finding it to be well below experimentally relevant temperatures. We discuss the implications of these results for realizing quantum spin ice in other materials.

  7. Self-action effects in semiconductor quantum dots

    NASA Astrophysics Data System (ADS)

    Dneprovskii, V. S.; Kanev, A. R.; Kozlova, M. V.; Smirnov, A. M.

    2014-05-01

    Two-dimensional (2D) dynamic photonic crystal regime has been utilized to investigate self-diffraction effect and nonlinear optical properties of excitons in CdSe/ZnS colloidal quantum dots (QDs). Self-diffraction at 2D photonic crystal arises for three intersecting beams of Nd+3:YAG laser second harmonic in the case of one-photon resonant excitation of the exciton (electron - hole) transition QDs. The relaxation time of excited excitons has been measured by pump and probe technique at induced one-dimensional transient diffraction grating. Two-exponential decay with initial fast and slow parts was discovered. Self-action effect has been discovered in the case of stationary resonant excitation of excitons in CdSe/ZnS QDs by the beam of second harmonic of powerful 12-nanosecond laser pulses. The bleaching of exciton absorption and the creation of transparency channel (this effect provokes self-diffraction of the second harmonic beam) was explained by the dominating coexisting and competing processes of state filling in stationary excited quantum dots and Stark-shift of exciton spectral band. The peculiarities of the influence of these processes at the change of exciton absorption in quantum dots in the case of different detuning from exciton resonance (quantum dots with different size have been used) was analyzed.

  8. Microscopic theory of quantum dot interactions with quantum light: Local field effect

    NASA Astrophysics Data System (ADS)

    Slepyan, G. Ya.; Magyarov, A.; Maksimenko, S. A.; Hoffmann, A.

    2007-11-01

    A theory of both linear and nonlinear electromagnetic responses of a single quantum dot (QD) exposed to quantum light, accounting for depolarization induced local field has been developed. Based on the microscopic Hamiltonian accounting for the electron-hole exchange interaction, an effective two-body Hamiltonian has been derived and expressed in terms of the incident electric field, with a separate term describing the QD depolarization. The quantum equations of motion have been formulated and solved using the Hamiltonian for various types of the QD optical excitation, such as Fock qubit, coherent fields, vacuum state of electromagnetic field, and light with arbitrary photonic state distribution. For a QD exposed to coherent light, we predict the appearance of two oscillatory regimes in the Rabi effect separated by the bifurcation. In the first regime, the standard collapse-revival phenomenon does not reveal itself and the QD population inversion is found to be negative, while in the second one, the collapse-revival picture is found to be strongly distorted as compared to that predicted by the standard Jaynes-Cummings model. For the case of QD interaction with an arbitrary quantum light state in the linear regime, it has been shown that the local field induces a fine structure of the absorbtion spectrum. Instead of a single line with frequency corresponding to the exciton transition frequency, a duplet appears, with one component shifted by the amount of the local field coupling parameter. It has been demonstrated that the strong light-matter coupling regime arises in the weak-field limit. A physical interpretation of the predicted effects has been proposed.

  9. A Proton Recoil Telescope for Neutron Spectroscopy

    NASA Astrophysics Data System (ADS)

    Cinausero, M.; Barbui, M.; Prete, G.; Rizzi, V.; Andrighetto, A.; Pesente, S.; Fabris, D.; Lunardon, M.; Nebbia, G.; Viesti, G.; Moretto, S.; Morando, M.; Zenoni, A.; Bocci, F.; Donzella, A.; Bonomi, G.; Fontana, A.

    2006-05-01

    The N2P research program funded by the INFN committee for Experimental Nuclear Physics (CSNIII) has among his goals the construction of a Proton Recoil Telescope (PRT), a detector to measure neutron energy spectra. The interest in such a detector is primarily related to the SPES project for rare beams production at the Laboratori Nazionali di Legnaro. For the SPES project it is, in fact, of fundamental importance to have reliable information about energy spectra and yield for neutrons produced by d or p projectiles on thick light targets to model the ''conversion target'' in which the p or d are converted in neutrons. These neutrons, in a second stage, will induce the Uranium fission in the ''production target''. The fission products are subsequently extracted, selected and re-accelerated to produce the exotic beam. The neutron spectra and angular distribution are important parameters to define the final production of fission fragments. In addition, this detector can be used to measure neutron spectra in the field of cancer therapy (this topic is nowadays of particular interest to INFN, for the National Centre for Hadron therapy (CNAO) in Pavia) and space applications.

  10. Binary Black Hole Mergers and Recoil Kicks

    NASA Technical Reports Server (NTRS)

    Centrella, Joan; Baker, J.; Choi, D.; Koppitz, M.; vanMeter, J.; Miller, C.

    2006-01-01

    Recent developments in numerical relativity have made it possible to follow reliably the coalescence of two black holes from near the innermost stable circular orbit to final ringdown. This opens up a wide variety of exciting astrophysical applications of these simulations. Chief among these is the net kick received when two unequal mass or spinning black holes merge. The magnitude of this kick has bearing on the production and growth of supermassive black holes during the epoch of structure formation, and on the retention of black holes in stellar clusters. Here we report the first accurate numerical calculation of this kick, for two nonspinning black holes in a 1.5:1 mass ratio, which is expected based on analytic considerations to give a significant fraction of the maximum possible recoil. We have performed multiple runs with different initial separations, orbital angular momenta, resolutions, extraction radii, and gauges. The full range of our kick speeds is 86-116 kilometers per second, and the most reliable runs give kicks between 86 and 97 kilometers per second. This is intermediate between the estimates from two recent post-Newtonian analyses and suggests that at redshifts z greater than 10, halos with masses less than 10(exp 9) M(sub SUN) will have difficulty retaining coalesced black holes after major mergers.

  11. Vortices in superconducting films: Statistics and fractional quantum Hall effect

    SciTech Connect

    Dziarmaga, J.

    1996-03-01

    We present a derivation of the Berry phase picked up during exchange of parallel vortices. This derivation is based on the Bogolubov{endash}de Gennes formalism. The origin of the Magnus force is also critically reanalyzed. The Magnus force can be interpreted as an interaction with the effective magnetic field. The effective magnetic field may be even of the order 10{sup 6}{ital T}/A. We discuss a possibility of the fractional quantum Hall effect (FQHE) in vortex systems. As the real magnetic field is varied to drive changes in vortex density, the vortex density will prefer to stay at some quantized values. The mere existence of the FQHE does not depend on vortex quantum statistics, although the pattern of the plateaux does. We also discuss how the density of anyonic vortices can lower the effective strengh of the Magnus force, what might be observable in measurements of Hall resistivity. {copyright} {ital 1996 The American Physical Society.}

  12. Additional Dirac Matrix in Quantum Hall Effect

    SciTech Connect

    Shrivastava, Keshav N.

    2008-05-20

    We find that the predictions of the Dirac equation agree with the idea of fractional charges. We have introduced the combination of spin and orbital quantum numbers, including the negative sign for spin, in such a way that there occur fractional charges through the Bohr magneton. This leads to doubling of eigen values so that we define an additional matrix the properties of which are important when magnetic field is present. There is a spin-charge coupling so that spin (1/2) particle can have the zero or one charge. The Dirac equation can accommodate not only charges of 0 and {+-}e but also fractional values such as 1/3 and 2/3. For spin (1/2) there are two eigen values, {+-}(1/2)g{mu}{sub B}H but when two different g values are taken into account, there are four eigen values, {+-}(1/2)g{+-}{mu}{sub B}H, which are fractionally charged. The Hall resistivity becomes spin dependent. The spin (1/2) particle with zero orbital angular momentum, has two values of resistivity, 3h/e{sup 2} and 3h/(2e{sup 2}) which means that when magnetic field is varied the resistivity can change by a factor of 2. If the spin is 3/2, the value of (1/2)g+ = (1/2)+(3/2) so that g = 4 arises which substituted in the series, {+-}(1/2)g{mu}{sub B}H, {+-}(3/2)g{mu}{sub B}H, {+-}(5/2)g{mu}{sub B}H, ..., gives 2, 6, 10, etc which are the correct numbers found experimentally.

  13. Geometric effects on quantum transport of ultracold atoms in optical lattices: Quantum acceleration and flat band

    NASA Astrophysics Data System (ADS)

    Chien, Chih-Chun; Metcalf, Mekena; di Ventra, Massimiliano; Chern, Gia-Wei

    2015-05-01

    The realizations of interesting optical lattices for ultracold atoms provide opportunities for investigating geometric effects on many-body physics. Thesquare, triangular, honeycomb, kagome lattices, and other geometries have been experimentally demonstrated. When the atoms are driven out of equilibrium by manipulations of the density or trapping potential, their quantum transport can be monitored and fundamental questions regarding transport in isolated systems can be addressed unambiguously. We found that the propagation velocity of the matter wave representing the flowing atoms can be accelerated by tuning the lattice geometry. This acceleration is a pure quantum effect because no shorter path is created as the geometry changes. For lattice geometries supporting a dispersionless flat band, the localized atoms in the flat band do not participate in transport but interfere with the mobile atoms. We found a generic insulating phase exhibiting a density jump in the profile that can be dynamically generated. Interesting spatial patterns may emerge if those flat-band lattices are manipulated, and an analogue of geometric frustration in quantum transport will be presented.

  14. Nonadiabatic quantum molecular dynamics with hopping. II. Role of nuclear quantum effects in atomic collisions

    NASA Astrophysics Data System (ADS)

    Fischer, M.; Handt, J.; Schmidt, R.

    2014-07-01

    The role of electron-nuclear correlations, i.e., quantum effects in the nuclear motion in atomic collisions with complex targets, is discussed using the recently developed nonadiabatic quantum molecular dynamics with hopping method [Fischer, Handt, and Schmidt, paper I of this series, Phys. Rev. A 90, 012525 (2014), 10.1103/PhysRevA.90.012525]. It is shown that the excitation process is nearly unaffected by electron-nuclear correlations as long as integral quantities are considered (total kinetic energy loss), whereas the relaxation mechanism of the molecular target is greatly affected (total fragmentation probability). To describe highly differential quantities (kinetic energy loss as a function of the scattering angle), however, the consideration of nuclear quantum effects during the initial excitation process is indispensable, even in collisions where one would expect purely classical behavior of the nuclei due to their small de Broglie wavelength. The calculations reproduce and explain in detail old but still unexplained experimental data of differential energy-loss spectroscopy in He +He and He +H2 collisions.

  15. 8 ? -periodic Josephson effects in a quantum dot/ quantum spin-Hall josephson junction system

    NASA Astrophysics Data System (ADS)

    Hui, Hoi-Yin; Sau, Jay

    2015-03-01

    Josephson junctions made of conventional s-wave superconductors display 2 ? periodicity. On the other hand, 4 ? -periodic fractional Josephson effect is known to be a characteristic signature of topological superconductors and Majorana fermions [1]. Zhang and Kane have shown that Josephson junctions made of topological superconductors are 8 ? -periodic if interaction is used to avoid dissipation [2]. Here we present a general argument for how time-reversal symmetry and Z2 non-trivial topology constrains the Josephson periodicity to be 8 ? . We then illustrate this through a microscopic model of a quantum dot in a quantum spin-hall Josephson junction. Work supported by NSF-JQI-PFC, LPS-CMTC and Microsoft Q.

  16. Quantum spin Hall effect in nanostructures based on cadmium fluoride

    SciTech Connect

    Bagraev, N. T.; Guimbitskaya, O. N.; Klyachkin, L. E.; Koudryavtsev, A. A.; Malyarenko, A. M.; Romanov, V. V.; Ryskin, A. I.; Shcheulin, A. S.

    2010-10-15

    Tunneling current-voltage (I-V) characteristics and temperature dependences of static magnetic susceptibility and specific heat of the CdB{sub x}F{sub 2-x}/p-CdF{sub 2}-QW/CdB{sub x}F{sub 2-x} planar sandwich structures formed on the surface of an n-CdF{sub 2} crystal have been studied in order to identify superconducting properties of the CdB{sub x}F{sub 2-x} {delta} barriers confining the p-type CdF{sub 2} ultranarrow quantum well. Comparative analysis of current-voltage (I-V) characteristics and conductance-voltage dependences (measured at the temperatures, respectively, below and above the critical temperature of superconducting transition) indicates that there is an interrelation between quantization of supercurrent and dimensional quantization of holes in the p-CdF{sub 2} ultranarrow quantum well. It is noteworthy that detection of the Josephson peak of current in each hole subband is accompanied by the appearance of the spectrum of the multiple Andreev reflection (MAR). A high degree of spin polarization of holes in the edge channels along the perimeter of the p-CdF{sub 2} ultranarrow quantum well appears as a result of MAR and makes it possible to identify the quantum spin Hall effect I-V characteristics; this effect becomes pronounced in the case of detection of nonzero conductance at the zero voltage applied to the vertical gate in the Hall geometry of the experiment. Within the energy range of superconducting gap, the I-V characteristics of the spin transistor and quantum spin Hall effect are controlled by the MAR spectrum appearing as the voltage applied to the vertical gate is varied. Beyond the range of the superconducting gap, the observed I-V characteristic of the quantum spin Hall effect is represented by a quantum conductance staircase with a height of the steps equal to e{sub 2}/h; this height is interrelated with the Aharonov-Casher oscillations of longitudinal and depends on the voltage applied to the vertical gate.

  17. Nambu-Goldstone effective theory of information at quantum criticality

    NASA Astrophysics Data System (ADS)

    Dvali, Gia; Franca, Andre; Gomez, Cesar; Wintergerst, Nico

    2015-12-01

    We establish a fundamental connection between quantum criticality of a many-body system, such as Bose-Einstein condensates, and its capacity of information-storage and processing. For deriving the effective theory of modes in the vicinity of the quantum critical point, we develop a new method by mapping a Bose-Einstein condensate of N -particles onto a sigma model with a continuous global (pseudo)symmetry that mixes bosons of different momenta. The Bogolyubov modes of the condensate are mapped onto the Goldstone modes of the sigma model, which become gapless at the critical point. These gapless Goldstone modes are the quantum carriers of information and entropy. Analyzing their effective theory, we observe information-processing properties strikingly similar to the ones predicted by the black hole portrait. The energy cost per qubit of information-storage vanishes in the large-N limit and the total information-storage capacity increases with N either exponentially or as a power law. The longevity of information-storage also increases with N , whereas the scrambling time in the over-critical regime is controlled by the Lyapunov exponent and scales logarithmically with N . This connection reveals that the origin of black hole information storage lies in the quantum criticality of the graviton Bose-gas, and that much simpler systems that can be manufactured in table-top experiments can exhibit very similar information-processing dynamics.

  18. Unraveling quantum mechanical effects in water using isotopic fractionation

    PubMed Central

    Markland, Thomas E.; Berne, B. J.

    2012-01-01

    When two phases of water are at equilibrium, the ratio of hydrogen isotopes in each is slightly altered because of their different phase affinities. This isotopic fractionation process can be utilized to analyze waters movement in the worlds climate. Here we show that equilibrium fractionation ratios, an entirely quantum mechanical property, also provide a sensitive probe to assess the magnitude of nuclear quantum fluctuations in water. By comparing the predictions of a series of water models, we show that those describing the OH chemical bond as rigid or harmonic greatly overpredict the magnitude of isotope fractionation. Models that account for anharmonicity in this coordinate are shown to provide much more accurate results because of their ability to give partial cancellation between inter- and intramolecular quantum effects. These results give evidence of the existence of competing quantum effects in water and allow us to identify how this cancellation varies across a wide-range of temperatures. In addition, this work demonstrates that simulation can provide accurate predictions and insights into hydrogen fractionation. PMID:22566650

  19. Stability diagram of the collective atomic recoil laser with thermal atoms

    NASA Astrophysics Data System (ADS)

    Tomczyk, H.; Schmidt, D.; Georges, C.; Slama, S.; Zimmermann, C.

    2015-06-01

    We experimentally investigate cold thermal atoms in a single sidedly pumped optical ring resonator for temperatures between 0.4 and 9 μ K . The threshold for collective atomic recoil lasing (CARL) is recorded for various pump-cavity detunings. The resulting stability diagram is interpreted by simulating the classical CARL equations. We find that the stability diagram for thermal atoms shows the same asymmetry as observed for Bose-Einstein condensates in previous experiments. Whereas for condensates the asymmetry is well explained by a Dicke-type quantum model we here discuss a simplified classical model. It complements the quantum model and provides an intuitive explanation based on the change in the long-range atomic interaction with pump-cavity detuning.

  20. Plasma wave instability in a quantum field effect transistor with magnetic field effect

    SciTech Connect

    Zhang, Li-Ping; Xue, Ju-Kui

    2013-08-15

    The current-carrying state of a nanometer Field Effect Transistor (FET) may become unstable against the generation of high-frequency plasma waves and lead to generation of terahertz radiation. In this paper, the influences of magnetic field, quantum effects, electron exchange-correlation, and thermal motion of electrons on the instability of the plasma waves in a nanometer FET are reported. We find that, while the electron exchange-correlation suppresses the radiation power, the magnetic field, the quantum effects, and the thermal motion of electrons can enhance the radiation power. The radiation frequency increases with quantum effects and thermal motion of electrons, but decreases with electron exchange-correlation effect. Interestingly, we find that magnetic field can suppress the quantum effects and the thermal motion of electrons and the radiation frequency changes non-monotonely with the magnetic field. These properties could make the nanometer FET advantageous for realization of practical terahertz oscillations.

  1. Memory effects in attenuation and amplification quantum processes

    SciTech Connect

    Lupo, Cosmo; Giovannetti, Vittorio; Mancini, Stefano

    2010-09-15

    With increasing communication rates via quantum channels, memory effects become unavoidable whenever the use rate of the channel is comparable to the typical relaxation time of the channel environment. We introduce a model of a bosonic memory channel, describing correlated noise effects in quantum-optical processes via attenuating or amplifying media. To study such a channel model, we make use of a proper set of collective field variables, which allows us to unravel the memory effects, mapping the n-fold concatenation of the memory channel to a unitarily equivalent, direct product of n single-mode bosonic channels. We hence estimate the channel capacities by relying on known results for the memoryless setting. Our findings show that the model is characterized by two different regimes, in which the cross correlations induced by the noise among different channel uses are either exponentially enhanced or exponentially reduced.

  2. Evanescent radiation, quantum mechanics and the Casimir effect

    NASA Technical Reports Server (NTRS)

    Schatten, Kenneth H.

    1989-01-01

    An attempt to bridge the gap between classical and quantum mechanics and to explain the Casimir effect is presented. The general nature of chaotic motion is discussed from two points of view: the first uses catastrophe theory and strange attractors to describe the deterministic view of this motion; the underlying framework for chaos in these classical dynamic systems is their extreme sensitivity to initial conditions. The second interpretation refers to randomness associated with probabilistic dynamics, as for Brownian motion. The present approach to understanding evanescent radiation and its relation to the Casimir effect corresponds to the first interpretation, whereas stochastic electrodynamics corresponds to the second viewpoint. The nonlinear behavior of the electromagnetic field is also studied. This well-understood behavior is utilized to examine the motions of two orbiting charges and shows a closeness between the classical behavior and the quantum uncertainty principle. The evanescent radiation is used to help explain the Casimir effect.

  3. Radiation pressure in strong-field-approximation theory: Retardation and recoil corrections

    NASA Astrophysics Data System (ADS)

    Krajewska, K.; Kami?ski, J. Z.

    2015-10-01

    Radiation pressure effects in ionization by short linearly polarized laser pulses are investigated in the framework of strong-field approximation, in both nonrelativistic and relativistic formulations. Differences between both approaches are discussed, and retardation and recoil corrections are defined. It is demonstrated how these corrections can be incorporated into the nonrelativistic approach, leading to the so-called quasirelativistic formulation. These three approaches are further applied to the analysis of signatures of radiation pressure in energy-angular distributions of photoelectrons. It is demonstrated that, for Ti:sapphire laser pulses of intensities up to 1016W /cm2 , predictions of the quasirelativistic formulation agree well with those of the full relativistic one, and that the recoil corrections contribute predominantly to radiation pressure effects.

  4. Quantum spin Hall effect in α -Sn /CdTe(001 ) quantum-well structures

    NASA Astrophysics Data System (ADS)

    Küfner, Sebastian; Matthes, Lars; Bechstedt, Friedhelm

    2016-01-01

    The electronic and topological properties of heterovalent and heterocrystalline α -Sn/CdTe(001) quantum wells (QWs) are studied in dependence on the thickness of α -Sn by means of ab initio calculations. We calculate the topological Z2 invariants of the respective bulk crystals, which identify α -Sn as strong three-dimensional (3D) topological insulators (TIs), whereas CdTe is a trivial insulator. We predict the existence of two-dimensional (2D) topological interface states between both materials and show that a topological phase transition from a trivial insulating phase into the quantum spin Hall (QSH) phase in the QW structures occurs at much higher thicknesses than in the HgTe case. The QSH effect is characterized by the localization, dispersion, and spin polarization of the topological interface states. We address the distinction of the 3D and 2D TI characters of the studied QW structures, which is inevitable for an understanding of the underlying quantum state of matter. The 3D TI nature is characterized by two-dimensional topological interface states, while the 2D phase exhibits one-dimensional edge states. The two different state characteristics are often intermixed in the discussion of the topology of 2D QW structures, especially, the comparison of ab initio calculations and experimental transport studies.

  5. Tunable interactions and the fractional quantum Hall effect

    NASA Astrophysics Data System (ADS)

    Papic, Zlatko

    2013-03-01

    We explore several realistic methods of tuning the interactions in two-dimensional electronic systems in high magnetic fields. We argue that these experimental probes can be useful in studying the interplay of topology, quantum geometry and symmetry breaking in the fractional quantum Hall effect (FQHE). In particular, we show that the mixing of subbands and Landau levels in GaAs wide quantum wells breaks the particle-hole symmetry between the Moore-Read Pfaffian state and its particle-hole conjugate, the anti-Pfaffian, in such a way that the latter is unambiguously favored and generically describes the ground state at 5/2 filling [1]. Furthermore, the tilting of the magnetic field, or more generally variation of the band mass tensor, probes the fluctuation of the intrinsic metric degree of freedom of the incompressible fluids, and ultimately induces the crossover to the broken-symmetry and nematic phases in higher Landau levels [2]. Some of these mechanisms also lead to an enhancement of the excitation gap of the non-Abelian states, as observed in recent experiments. Finally, we compare the tuning capabilities in conventional systems with that in multilayer graphene and related materials with Dirac-type carriers where tuning the band structure and dielectric environment provides a simple and direct method to engineer more robust FQHE states and to study quantum transitions between them [3]. This work was supported by DOE grant DESC0002140.

  6. Fractional quantum Hall effect in a curved space

    NASA Astrophysics Data System (ADS)

    Can, Tankut Uzay

    The fractional quantum Hall (FQH) effect occurs when two-dimensional electrons in a high magnetic field condense to form an incompressible quantum liquid. This quantum phase is known to support particle-like excitations with fractional charge and anyonic statistics. A powerful theoretical approach to understanding these properties involves constructing an ansatz for the ground state wave function, and probing the response to variations in magnetic flux and background metric. The resulting universal kinetic coefficients for electromagnetic and gravitational response provide a nearly complete characterization of the FQH state. However, typically only the response to homogeneous deformations is considered, which leaves open the question of how these quantum liquids couple to local curvature and magnetic field gradients. In this thesis, we discuss FQH states in the lowest Landau level on more general curved spaces and for non-uniform magnetic fields. These states prove to have a rich structure which reveals a close connection between electromagnetic and gravitational responses. We see this by studying local transformation properties of correlation functions under geometric deformations and field variations. We also develop a method for computing the exact asymptotic expansion of ground state correlation functions.

  7. Robust electron pairing in the integer quantum hall effect regime.

    PubMed

    Choi, H K; Sivan, I; Rosenblatt, A; Heiblum, M; Umansky, V; Mahalu, D

    2015-01-01

    Electron pairing is a rare phenomenon appearing only in a few unique physical systems; for example, superconductors and Kondo-correlated quantum dots. Here, we report on an unexpected electron pairing in the integer quantum Hall effect regime. The pairing takes place within an interfering edge channel in an electronic Fabry-Perot interferometer at a wide range of bulk filling factors, between 2 and 5. We report on three main observations: high-visibility Aharonov-Bohm conductance oscillations with magnetic flux periodicity equal to half the magnetic flux quantum; an interfering quasiparticle charge equal to twice the elementary electron charge as revealed by quantum shot noise measurements, and full dephasing of the pairs' interference by induced dephasing of the adjacent inner edge channel-a manifestation of inter-channel entanglement. Although this pairing phenomenon clearly results from inter-channel interaction, the exact mechanism that leads to electron-electron attraction within a single edge channel is not clear. We believe that substantial efforts are needed in order to clarify these intriguing and unexpected findings. PMID:26096516

  8. Aharonov-Bohm effect in the tunnelling of a quantum rotor in a linear Paul trap

    NASA Astrophysics Data System (ADS)

    Noguchi, Atsushi; Shikano, Yutaka; Toyoda, Kenji; Urabe, Shinji

    2014-05-01

    Quantum tunnelling is a common fundamental quantum mechanical phenomenon that originates from the wave-like characteristics of quantum particles. Although the quantum tunnelling effect was first observed 85 years ago, some questions regarding the dynamics of quantum tunnelling remain unresolved. Here we realize a quantum tunnelling system using two-dimensional ionic structures in a linear Paul trap. We demonstrate that the charged particles in this quantum tunnelling system are coupled to the vector potential of a magnetic field throughout the entire process, even during quantum tunnelling, as indicated by the manifestation of the Aharonov-Bohm effect in this system. The tunnelling rate of the structures periodically depends on the strength of the magnetic field, whose period is the same as the magnetic flux quantum ?0 through the rotor [(0.990.07) ?0].

  9. Nuclear quantum effects using selective mode excitation in water

    NASA Astrophysics Data System (ADS)

    Ganeshan, Sriram; Fernandez-Serra, Marivi

    2011-03-01

    Recently, Ceriotti et. al. introduced a comprehensive framework to use a custom-tailored Langevin equation with correlated-noise in the context of MD simulations. One of the interesting applications of these thermostats is that, such a framework can be used to selectively excite normal modes whose frequency falls within a prescribed, narrow range. The general idea of this work is to understand whether, the selective excitation of modes in some systems like water is enough to reproduce the necessary nuclear quantum effects at a given temperature. Ceriotti et. al has also implemented their colored noise thermostat (Langevin) to the PIMD of TIP4P/F model. In this work we study how the TIP4P/f responds to the selective mode excitation using the delta-thermostats. We apply this delta thermostat to the molecular dynamics of TIP4P/F water force field, a model explicitly fitted with the lack of zero point ionic vibrations. TIP4P/F provides us an ideal platform to study the effect of selective mode excitation on water. We address the question of whether selective mode excitations are enough to generate the nuclear quantum effects in water. This work will also provide a way to identify the dominant modes for which the quantum effects are important.

  10. Casimir effects for classical and quantum liquids in slab geometry: A brief review

    NASA Astrophysics Data System (ADS)

    Biswas, Shyamal

    2015-05-01

    We analytically explore Casimir effects for confinement of classical and quantum fluctuations in slab (film) geometry (i) for classical (critical) fluctuations over 4He liquid around the ? point, and (ii) for quantum (phonon) fluctuations of Bogoliubov excitations over an interacting Bose-Einstein condensate. We also briefly review Casimir effects for confinement of quantum vacuum fluctuations confined to two plates of different geometries.

  11. What Can We Learn From Proton Recoils about Heavy-Ion SEE Sensitivity?

    NASA Technical Reports Server (NTRS)

    Ladbury, Raymond L.

    2016-01-01

    The fact that protons cause single-event effects (SEE) in most devices through production of light-ion recoils has led to attempts to bound heavy-ion SEE susceptibility through use of proton data. Although this may be a viable strategy for some devices and technologies, the data must be analyzed carefully and conservatively to avoid over-optimistic estimates of SEE performance. We examine the constraints that proton test data can impose on heavy-ion SEE susceptibility.

  12. Quantum effects in the hot electron microbolometer

    SciTech Connect

    Tang, A.; Richards, P.L.

    1994-10-01

    The theory of the hot electron microbolometer proposed by Nahum et al. assumed that the photon energy is thermalized in the electrons in the Cu absorber before relaxing to the lattice. Since the photons initially excite individual electrons to K{omega}>>k{sub B}T, however, direct relaxation of these hot electrons to phonons must also be considered. Theoretical estimates suggest that this extra relaxation channel increases the effective thermal conductance for K{omega}>>k{sub B}T and influences bolometer noise. Calculations of these effects are presented which predict very useful performance both for ground-based and spacebased astronomical photometry at millimeter and submillimeter wavelengths.

  13. Quasiparticle Aggregation in the Fractional Quantum Hall Effect

    DOE R&D Accomplishments Database

    Laughlin, R. B.

    1984-10-10

    Quasiparticles in the Fractional Quantum Hall Effect behave qualitatively like electrons confined to the lowest landau level, and can do everything electrons can do, including condense into second generation Fractional Quantum Hall ground states. I review in this paper the reasoning leading to variational wavefunctions for ground state and quasiparticles in the 1/3 effect. I then show how two-quasiparticle eigenstates are uniquely determined from symmetry, and how this leads in a natural way to variational wavefunctions for composite states which have the correct densities (2/5, 2/7, ...). I show in the process that the boson, anyon and fermion representations for the quasiparticles used by Haldane, Halperin, and me are all equivalent. I demonstrate a simple way to derive Halperin`s multiple-valued quasiparticle wavefunction from the correct single-valued electron wavefunction. (auth)

  14. Quasiparticle aggregation in the Fractional Quantum Hall Effect

    SciTech Connect

    Laughlin, R.B.

    1984-10-10

    Quasiparticles in the Fractional Quantum Hall Effect behave qualitatively like electrons confined to the lowest landau level, and can do everything electrons can do, including condense into second generation Fractional Quantum Hall ground states. I review in this paper the reasoning leading to variational wavefunctions for ground state and quasiparticles in the 1/3 effect. I then show how two-quasiparticle eigenstates are uniquely determined from symmetry, and how this leads in a natural way to variational wavefunctions for composite states which have the correct densities (2/5, 2/7, ...). I show in the process that the boson, anyon and fermion representations for the quasiparticles used by Haldane, Halperin, and me are all equivalent. I demonstrate a simple way to derive Halperin's multiple-valued quasiparticle wavefunction from the correct single-valued electron wavefunction.

  15. Relativistic and quantum electrodynamic effects in superheavy elements

    NASA Astrophysics Data System (ADS)

    Schwerdtfeger, Peter; Pašteka, Lukáš F.; Punnett, Andrew; Bowman, Patrick O.

    2015-12-01

    The current status of relativistic electronic structure theory for superheavy elements is reviewed. Recent developments in relativistic quantum theory have made it possible to obtain accurate electronic properties for the trans-actinide elements with the aim to predict their chemical and physical behaviour. The role of quantum electrodynamic effects beyond the no-virtual-pair approximation, which is usually neglected in relativistic molecular calculations, is discussed. Changes in periodic trends due to relativistic effects are outlined for the superheavy elements with nuclear charge Z = 111- 120. We also analyse the role of the negative energy states for the electronic stability of superheavy elements beyond the critical nuclear charge (Zcrit ≈ 170), where the 1s state enters the negative energy continuum at - 2mec2.

  16. Effective spin chains for fractional quantum Hall states

    NASA Astrophysics Data System (ADS)

    Bergholtz, Emil J.; Nakamura, Masaaki; Suorsa, Juha

    2011-01-01

    Fractional quantum Hall (FQH) states are topologically ordered which indicates that their essential properties are insensitive to smooth deformations of the manifold on which they are studied. Their microscopic Hamiltonian description, however, strongly depends on geometrical details. Recent work has shown how this dependence can be exploited to generate effective models that are both interesting in their own right and also provide further insight into the quantum Hall system. We review and expand on recent efforts to understand the FQH system close to the solvable thin-torus limit in terms of effective spin chains. In particular, we clarify how the difference between the bosonic and fermionic FQH states, which is not apparent in the thin-torus limit, can be seen at this level. Additionally, we discuss the relation of the Haldane-Shastry chain to the so-called QH circle limit and comment on its significance to recent entanglement studies.

  17. Inflationary back-reaction effects from Relativistic Quantum Geometry

    NASA Astrophysics Data System (ADS)

    Bellini, Mauricio

    2016-03-01

    We study the dynamics of scalar metric fluctuations in a non-perturbative variational formalism recently introduced, by which the dynamics of a geometrical scalar field θ, describes the quantum geometrical effects on a Weylian-like manifold with respect to a background Riemannian space-time. In this letter we have examined an example in the framework of inflationary cosmology. The resulting spectral predictions are in very good agreement with observations and other models of inflation.

  18. Scintillation efficiency measurement of Na recoils in NaI(Tl) below the DAMA/LIBRA energy threshold

    NASA Astrophysics Data System (ADS)

    Xu, Jingke; Shields, Emily; Calaprice, Frank; Westerdale, Shawn; Froborg, Francis; Suerfu, Burkhant; Alexander, Thomas; Aprahamian, Ani; Back, Henning O.; Casarella, Clark; Fang, Xiao; Gupta, Yogesh K.; Ianni, Aldo; Lamere, Edward; Lippincott, W. Hugh; Liu, Qian; Lyons, Stephanie; Siegl, Kevin; Smith, Mallory; Tan, Wanpeng; Kolk, Bryant Vande

    2015-07-01

    The dark matter interpretation of the DAMA modulation signal depends on the NaI(Tl) scintillation efficiency of nuclear recoils. Previous measurements for Na recoils have large discrepancies, especially in the DAMA/LIBRA modulation energy region. We report a quenching effect measurement of Na recoils in NaI(Tl) from 3 to 52 keVnr, covering the whole DAMA/LIBRA energy region for dark matter-Na scattering interpretations. By using a low-energy, pulsed neutron beam, a double time-of-flight technique, and pulse-shape discrimination methods, we obtained the most accurate measurement of this kind for NaI(Tl) to date. The results differ significantly from the DAMA reported values at low energies but fall between the other previous measurements. We present the implications of the new quenching results for the dark matter interpretation of the DAMA modulation signal.

  19. Negative muon chemistry: the quantum muon effect and the finite nuclear mass effect.

    PubMed

    Posada, Edwin; Moncada, Félix; Reyes, Andrés

    2014-10-01

    The any-particle molecular orbital method at the full configuration interaction level has been employed to study atoms in which one electron has been replaced by a negative muon. In this approach electrons and muons are described as quantum waves. A scheme has been proposed to discriminate nuclear mass and quantum muon effects on chemical properties of muonic and regular atoms. This study reveals that the differences in the ionization potentials of isoelectronic muonic atoms and regular atoms are of the order of millielectronvolts. For the valence ionizations of muonic helium and muonic lithium the nuclear mass effects are more important. On the other hand, for 1s ionizations of muonic atoms heavier than beryllium, the quantum muon effects are more important. In addition, this study presents an assessment of the nuclear mass and quantum muon effects on the barrier of Heμ + H2 reaction. PMID:25188920

  20. Kondo effect from a tunable bound state within a quantum wire.

    PubMed

    Sfigakis, F; Ford, C J B; Pepper, M; Kataoka, M; Ritchie, D A; Simmons, M Y

    2008-01-18

    We investigate the conductance of quantum wires with a variable open quantum dot geometry, displaying an exceptionally strong Kondo effect and most of the 0.7 structure characteristics. Our results indicate that the 0.7 structure is not a manifestation of the singlet Kondo effect. However, specific similarities between our devices and many of the clean quantum wires reported in the literature suggest a weakly bound state is often present in real quantum wires. PMID:18232908

  1. Quantum instanton evaluation of the kinetic isotope effects

    SciTech Connect

    Vanicek, Jiri; Miller, William H.; Castillo, Jesus F.; Aoiz, F.Javier

    2005-04-19

    A general quantum-mechanical method for computing kinetic isotope effects is presented. The method is based on the quantum instanton approximation for the rate constant and on the path integral Metropolis Monte-Carlo evaluation of the Boltzmann operator matrix elements. It computes the kinetic isotope effect directly, using a thermodynamic integration with respect to the mass of the isotope, thus avoiding the more computationally expensive process of computing the individual rate constants. The method is more accurate than variational transition-state theories or the semiclassical instanton method since it does not assume a single reaction path and does not use a semiclassical approximation of the Boltzmann operator. While the general Monte-Carlo implementation makes the method accessible to systems with a large number of atoms, we present numerical results for the Eckart barrier and for the collinear and full three-dimensional isotope variants of the hydrogen exchange reaction H+H{sub 2} {yields} H{sub 2}+H. In all seven test cases, for temperatures between 250 K and 600 K, the error of the quantum instanton approximation for the kinetic isotope effects is less than {approx}10%.

  2. Quantum anomalous Hall effect in stable dumbbell stanene

    NASA Astrophysics Data System (ADS)

    Zhang, Huisheng; Zhang, Jiayong; Zhao, Bao; Zhou, Tong; Yang, Zhongqin

    2016-02-01

    Topological property of the dumbbell (DB) stanene, more stable than the stanene with a honeycomb lattice, is investigated by using ab initio methods. The magnetic DB stanene demonstrates an exotic quantum anomalous Hall (QAH) effect due to inversion of the Sn spin-up px,y and spin-down pz states. The QAH gap is found to be opened at Γ point rather than the usual K and K' points, beneficial to observe the effect in experiments. When a 3% tensile strain is applied, a large nontrivial gap (˜50 meV) is achieved. Our results provide another lighthouse for realizing QAH effects in two-dimensional systems.

  3. Diffraction effects on light-atomic-ensemble quantum interface

    SciTech Connect

    Mueller, J.H.; Petrov, P.; Garrido Alzar, C.L.; Polzik, E.S.; Oblak, D.; Echaniz, S.R. de

    2005-03-01

    We present a simple method to include the effects of diffraction into the description of a light-atomic ensemble quantum interface in the context of collective variables. Carrying out a scattering calculation we single out the purely geometrical effect and apply our method to the experimental relevant case of Gaussian-shaped atomic samples stored in single beam optical dipole traps probed by a Gaussian beam. We derive simple scaling relations for the effect of the interaction geometry and compare our findings to the results from one-dimensional models of light propagation.

  4. Thermopower enhancement in quantum wells with the Rashba effect

    SciTech Connect

    Wu, Lihua; Yang, Jiong; Wang, Shanyu; Wei, Ping; Yang, Jihui E-mail: wqzhang@mail.sic.ac.cn; Zhang, Wenqing E-mail: wqzhang@mail.sic.ac.cn; Chen, Lidong

    2014-11-17

    We theoretically demonstrate that the thermopower in two-dimensional quantum wells (QWs) can be significantly enhanced by its Rashba spin-splitting effect, governed by the one-dimensional density of states in the low Fermi energy region. The thermopower enhancement is due to the lower Fermi level for a given carrier concentration in Rashba QWs, as compared with that in normal two-dimensional systems without the spin-splitting effect. The degenerate approximation directly shows that larger strength of Rashba effect leads to higher thermopower and consequently better thermoelectric performance in QWs.

  5. Automation of experiments at Dubna Gas-Filled Recoil Separator

    NASA Astrophysics Data System (ADS)

    Tsyganov, Yu. S.

    2016-01-01

    Approaches to solving the problems of automation of basic processes in long-term experiments in heavy ion beams of the Dubna Gas-Filled Recoil Separator (DGFRS) facility are considered. Approaches in the field of spectrometry, both of rare α decays of superheavy nuclei and those for constructing monitoring systems to provide accident-free experiment running with highly radioactive targets and recording basic parameters of experiment, are described. The specific features of Double Side Silicon Strip Detectors (DSSSDs) are considered, special attention is paid to the role of boundary effects of neighboring p-n transitions in the "active correlations" method. An example of an off-beam experiment attempting to observe Zeno effect is briefly considered. Basic examples for nuclear reactions of complete fusion at 48Ca ion beams of U-400 cyclotron (LNR, JINR) are given. A scenario of development of the "active correlations" method for the case of very high intensity beams of heavy ions at promising accelerators of LNR, JINR, is presented.

  6. Gravitational-wave probe of effective quantum gravity

    NASA Astrophysics Data System (ADS)

    Alexander, Stephon; Finn, Lee Samuel; Yunes, Nicols

    2008-09-01

    All modern routes leading to a quantum theory of gravityi.e., perturbative quantum gravitational one-loop exact correction to the global chiral current in the standard model, string theory, and loop quantum gravityrequire modification of the classical Einstein-Hilbert action for the spacetime metric by the addition of a parity-violating Chern-Simons term. The introduction of such a term leads to spacetimes that manifest an amplitude birefringence in the propagation of gravitational waves. While the degree of birefringence may be intrinsically small, its effects on a gravitational wave accumulate as the wave propagates. Observation of gravitational waves that have propagated over cosmological distances may allow the measurement of even a small birefringence, providing evidence of quantum gravitational effects. The proposed Laser Interferometer Space Antenna (LISA) will be sensitive enough to observe the gravitational waves from sources at cosmological distances great enough that interesting bounds on the Chern-Simons coupling may be found. Here we evaluate the effect of a Chern-Simons induced spacetime birefringence to the propagation of gravitational waves from such systems. Focusing attention on the gravitational waves from coalescing binary black holes systems, which LISA will be capable of observing at redshifts approaching 30, we find that the signature of Chern-Simons gravity is a time-dependent change in the apparent orientation of the binarys orbital angular momentum with respect to the observer line-of-sight, with the magnitude of change reflecting the integrated history of the Chern-Simons coupling over the worldline of the radiation wave front. While spin-orbit coupling in the binary system will also lead to an evolution of the systems orbital angular momentum, the time dependence and other details of this real effect are different than the apparent effect produced by Chern-Simons birefringence, allowing the two effects to be separately identified. In this way gravitational-wave observations with LISA may thus provide our first and only opportunity to probe the quantum structure of spacetime over cosmological distances.

  7. Gravitational-wave probe of effective quantum gravity

    SciTech Connect

    Alexander, Stephon; Finn, Lee Samuel; Yunes, Nicolas

    2008-09-15

    All modern routes leading to a quantum theory of gravity - i.e., perturbative quantum gravitational one-loop exact correction to the global chiral current in the standard model, string theory, and loop quantum gravity - require modification of the classical Einstein-Hilbert action for the spacetime metric by the addition of a parity-violating Chern-Simons term. The introduction of such a term leads to spacetimes that manifest an amplitude birefringence in the propagation of gravitational waves. While the degree of birefringence may be intrinsically small, its effects on a gravitational wave accumulate as the wave propagates. Observation of gravitational waves that have propagated over cosmological distances may allow the measurement of even a small birefringence, providing evidence of quantum gravitational effects. The proposed Laser Interferometer Space Antenna (LISA) will be sensitive enough to observe the gravitational waves from sources at cosmological distances great enough that interesting bounds on the Chern-Simons coupling may be found. Here we evaluate the effect of a Chern-Simons induced spacetime birefringence to the propagation of gravitational waves from such systems. Focusing attention on the gravitational waves from coalescing binary black holes systems, which LISA will be capable of observing at redshifts approaching 30, we find that the signature of Chern-Simons gravity is a time-dependent change in the apparent orientation of the binary's orbital angular momentum with respect to the observer line-of-sight, with the magnitude of change reflecting the integrated history of the Chern-Simons coupling over the worldline of the radiation wave front. While spin-orbit coupling in the binary system will also lead to an evolution of the system's orbital angular momentum, the time dependence and other details of this real effect are different than the apparent effect produced by Chern-Simons birefringence, allowing the two effects to be separately identified. In this way gravitational-wave observations with LISA may thus provide our first and only opportunity to probe the quantum structure of spacetime over cosmological distances.

  8. A coherent understanding of low-energy nuclear recoils in liquid xenon

    SciTech Connect

    Sorensen, Peter

    2010-09-01

    Liquid xenon detectors such as XENON10 and XENON100 obtain a significant fraction of their sensitivity to light (?<10 GeV) particle dark matter by looking for nuclear recoils of only a few keV, just above the detector threshold. Yet in this energy regime a correct treatment of the detector threshold and resolution remains unclear. The energy dependence of the scintillation yield of liquid xenon for nuclear recoils also bears heavily on detector sensitivity, yet numerous measurements have not succeeded in obtaining concordant results. In this article we show that the ratio of detected ionization to scintillation can be leveraged to constrain the scintillation yield. We also present a rigorous treatment of liquid xenon detector threshold and energy resolution. Notably, the effective energy resolution differs significantly from a simple Poisson distribution. We conclude with a calculation of dark matter exclusion limits, and show that existing data from liquid xenon detectors strongly constrain recent interpretations of light dark matter.

  9. Predictive theory for elastic scattering and recoil of protons from 4He

    NASA Astrophysics Data System (ADS)

    Hupin, Guillaume; Quaglioni, Sofia; Navrtil, Petr

    2014-12-01

    Low-energy cross sections for elastic scattering and recoil of protons from 4He nuclei (also known as ? particles) are calculated directly by solving the Schrdinger equation for five nucleons interacting through accurate two- and three-nucleon forces derived within the framework of chiral effective field theory. Precise knowledge of these processes at various proton backscattering/recoil angles and energies is needed for the ion-beam analysis of numerous materials, from the surface layers of solids, to thin films, to fusion-reactor materials. Indeed, the same elastic scattering process, in two different kinematic configurations, can be used to probe the concentrations and depth profiles of either hydrogen or helium. We compare our results to available experimental data and show that direct calculations with modern nuclear potentials can help to resolve remaining inconsistencies among data sets and can be used to predict these cross sections when measurements are not available.

  10. Quantum confined Stark effect in organic fluorophores.

    NASA Astrophysics Data System (ADS)

    Peng, Xihong; Anderson, John; Tepper, Gary; Bandyopadhyay, Supriyo; Nayak, Saroj

    2008-03-01

    Fluorescent molecules have widely been used to detect and visualize structure and processes in biological samples due to its extraordinary sensitivity. However, the emission spectra of flurophores are usually broad and the accurate identification is difficult. Recently, experiments show that energy shifts by Stark effect can be used to aid the identification of organic molecules [1]. Stark effect originates from the shifting/splitting of energy levels when a molecule is under an external electric field, which shows a shift/splitting of a peak in absorption/emission spectra. The size of the shift depends on the magnitude of the external field and the molecular structure. In this talk we will show our theoretical study of the peak shifts on emission spectra for a series of organic fluorophores such as tyrosine, tryptophan, rhodamine123 and coumarin314 using density functional theory. We find that a particular peak shift is determined by the local dipole moments of molecular orbitals rather than the global dipole moment of the molecule. These molecular-specific shifts in emission spectra may enable to improve molecular identification in biosensors. Our results will be compared with experimental data. [1]Unpublished, S. Sarkar, B. Kanchibotla, S. Bandyopadhyay, G. Tepper, J. Edwards, J. Anderson, and R. Kessick.

  11. Effect of carrier dynamics and temperature on two-state lasing in semiconductor quantum dot lasers

    SciTech Connect

    Korenev, V. V. Savelyev, A. V.; Zhukov, A. E.; Omelchenko, A. V.; Maximov, M. V.

    2013-10-15

    It is analytically shown that the both the charge carrier dynamics in quantum dots and their capture into the quantum dots from the matrix material have a significant effect on two-state lasing phenomenon in quantum dot lasers. In particular, the consideration of desynchronization in electron and hole capture into quantum dots allows one to describe the quenching of ground-state lasing observed at high injection currents both qualitatevely and quantitatively. At the same time, an analysis of the charge carrier dynamics in a single quantum dot allowed us to describe the temperature dependences of the emission power via the ground- and excited-state optical transitions of quantum dots.

  12. Quantum Effects in the Nonlinear Response of Graphene Plasmons.

    PubMed

    Cox, Joel D; Silveiro, Iván; García de Abajo, F Javier

    2016-02-23

    The ability of graphene to support long-lived, electrically tunable plasmons that interact strongly with light, combined with its highly nonlinear optical response, has generated great expectations for application of the atomically thin material to nanophotonic devices. These expectations are mainly reinforced by classical analyses performed using the response derived from extended graphene, neglecting finite-size and nonlocal effects that become important when the carbon layer is structured on the nanometer scale in actual device designs. Here we show that finite-size effects produce large contributions that increase the nonlinear response of nanostructured graphene to significantly higher levels than those predicted by classical theories. We base our analysis on a quantum-mechanical description of graphene using tight-binding electronic states combined with the random-phase approximation. While classical and quantum descriptions agree well for the linear response when either the plasmon energy is below the Fermi energy or the size of the structure exceeds a few tens of nanometers, this is not always the case for the nonlinear response, and in particular, third-order Kerr-type nonlinearities are generally underestimated by the classical theory. Our results reveal the complex quantum nature of the optical response in nanostructured graphene, while further supporting the exceptional potential of this material for nonlinear nanophotonic devices. PMID:26718484

  13. Area Distribution and Quantum Interference Effect in Antidot Lattices

    NASA Astrophysics Data System (ADS)

    Maruyama, Hidesuke; Ma, Jun; Nakamura, Katsuhiro

    2000-10-01

    The quantum interference effect in ballistic antidot lattices under avery weak magnetic field is investigated. The area distribution of coherent backscattering orbits obeys the many-peaked structure with each peak located at multiples of the unit-cell area, and can be explained in terms of the length distribution. Using the area distribution in a semiclassical description of Kubo formula, we derive expressions for both h/2e oscillation and negative magneto-resistivity caused by the interference between a time-reversal pair of coherent backscattering orbits. The flux dependence of the oscillation part inthe quantum correction, which qualitatively differs from the one for a single Sinai billiard, is responsible for trapping and jumping motions in the underlying classical dynamics.

  14. Fractional quantum Hall effect in CdTe

    NASA Astrophysics Data System (ADS)

    Piot, B. A.; Kunc, J.; Potemski, M.; Maude, D. K.; Betthausen, C.; Vogl, A.; Weiss, D.; Karczewski, G.; Wojtowicz, T.

    2010-08-01

    The fractional quantum Hall (FQH) effect is reported in a high mobility CdTe quantum well at millikelvin temperatures. Fully developed FQH states are observed at filling factor 4/3 and 5/3 and are found to be both spin-polarized ground state for which the lowest energy excitation is not a spin flip. This can be accounted for by the relatively high intrinsic Zeeman energy in this single valley two-dimensional electron gas. FQH minima are also observed in the first excited (N=1) Landau level at filling factor 7/3 and 8/3 for intermediate temperatures. In contrast, the 5/2 FQH state remains absent down to T10mK .

  15. Fractionally charged skyrmions in fractional quantum Hall effect

    SciTech Connect

    Balram, Ajit C.; Wurstbauer, U.; Wójs, A.; Pinczuk, A.; Jain, J. K.

    2015-11-26

    The fractional quantum Hall effect has inspired searches for exotic emergent topological particles, such as fractionally charged excitations, composite fermions, abelian and nonabelian anyons and Majorana fermions. Fractionally charged skyrmions, which support both topological charge and topological vortex-like spin structure, have also been predicted to occur in the vicinity of 1/3 filling of the lowest Landau level. The fractional skyrmions, however, are anticipated to be exceedingly fragile, suppressed by very small Zeeman energies. Here we show that, slightly away from 1/3 filling, the smallest manifestations of the fractional skyrmion exist in the excitation spectrum for a broad range of Zeeman energies, and appear in resonant inelastic light scattering experiments as well-defined resonances slightly below the long wavelength spin wave mode. The spectroscopy of these exotic bound states serves as a sensitive tool for investigating the residual interaction between composite fermions, responsible for delicate new fractional quantum Hall states in this filling factor region.

  16. Fractionally charged skyrmions in fractional quantum Hall effect

    NASA Astrophysics Data System (ADS)

    Balram, Ajit C.; Wurstbauer, U.; Wójs, A.; Pinczuk, A.; Jain, J. K.

    2015-11-01

    The fractional quantum Hall effect has inspired searches for exotic emergent topological particles, such as fractionally charged excitations, composite fermions, abelian and nonabelian anyons and Majorana fermions. Fractionally charged skyrmions, which support both topological charge and topological vortex-like spin structure, have also been predicted to occur in the vicinity of 1/3 filling of the lowest Landau level. The fractional skyrmions, however, are anticipated to be exceedingly fragile, suppressed by very small Zeeman energies. Here we show that, slightly away from 1/3 filling, the smallest manifestations of the fractional skyrmion exist in the excitation spectrum for a broad range of Zeeman energies, and appear in resonant inelastic light scattering experiments as well-defined resonances slightly below the long wavelength spin wave mode. The spectroscopy of these exotic bound states serves as a sensitive tool for investigating the residual interaction between composite fermions, responsible for delicate new fractional quantum Hall states in this filling factor region.

  17. Fractionally charged skyrmions in fractional quantum Hall effect

    PubMed Central

    Balram, Ajit C.; Wurstbauer, U.; Wójs, A.; Pinczuk, A.; Jain, J. K.

    2015-01-01

    The fractional quantum Hall effect has inspired searches for exotic emergent topological particles, such as fractionally charged excitations, composite fermions, abelian and nonabelian anyons and Majorana fermions. Fractionally charged skyrmions, which support both topological charge and topological vortex-like spin structure, have also been predicted to occur in the vicinity of 1/3 filling of the lowest Landau level. The fractional skyrmions, however, are anticipated to be exceedingly fragile, suppressed by very small Zeeman energies. Here we show that, slightly away from 1/3 filling, the smallest manifestations of the fractional skyrmion exist in the excitation spectrum for a broad range of Zeeman energies, and appear in resonant inelastic light scattering experiments as well-defined resonances slightly below the long wavelength spin wave mode. The spectroscopy of these exotic bound states serves as a sensitive tool for investigating the residual interaction between composite fermions, responsible for delicate new fractional quantum Hall states in this filling factor region. PMID:26608906

  18. Fractionally charged skyrmions in fractional quantum Hall effect.

    PubMed

    Balram, Ajit C; Wurstbauer, U; Wójs, A; Pinczuk, A; Jain, J K

    2015-01-01

    The fractional quantum Hall effect has inspired searches for exotic emergent topological particles, such as fractionally charged excitations, composite fermions, abelian and nonabelian anyons and Majorana fermions. Fractionally charged skyrmions, which support both topological charge and topological vortex-like spin structure, have also been predicted to occur in the vicinity of 1/3 filling of the lowest Landau level. The fractional skyrmions, however, are anticipated to be exceedingly fragile, suppressed by very small Zeeman energies. Here we show that, slightly away from 1/3 filling, the smallest manifestations of the fractional skyrmion exist in the excitation spectrum for a broad range of Zeeman energies, and appear in resonant inelastic light scattering experiments as well-defined resonances slightly below the long wavelength spin wave mode. The spectroscopy of these exotic bound states serves as a sensitive tool for investigating the residual interaction between composite fermions, responsible for delicate new fractional quantum Hall states in this filling factor region. PMID:26608906

  19. z = 3 antiferromagnetic quantum criticality driven by the Kondo effect.

    PubMed

    Kim, Ki-Seok; Jia, Chenglong

    2010-04-16

    We find that the Kondo effect results in a new universality class for an antiferromagnetic (AF) quantum critical point (QCP) in the heavy fermion quantum transition, described by deconfined bosonic spinons with the dynamical exponent z=3. We show that the thermodynamics and transport of the z=3 AF QCP are consistent with the well-known non-Fermi liquid physics such as the divergent Grneisen ratio with an exponent 2/3 and temperature-linear resistivity. We propose that the hallmark of the Kondo-driven AF QCP is a uniform spin susceptibility that diverges with an exponent 2/3, remarkably consistent with the experimental observations for YbRh2Si2. PMID:20482002

  20. Directional recoil rate for direct detection of WIMPs

    NASA Astrophysics Data System (ADS)

    Alenazi, Moqbil; Gondolo, Paolo

    2007-10-01

    The problem of directional direct detection of weakly interacting massive particles (WIMPs) dark matter (DM) is investigated. We compute, analytically and numerically, the directional differential recoil rate dRd? of recoiled target nuclei hit by WIMPs in direct detection experiments in terms of the angle ?, which is the angle between the reference direction and the recoil direction. While the analytic method is for fixed reference direction and Gaussian distribution of WIMPs, the numeric method is a general method. The two methods give the same results. We apply the numeric method to various Maxwellian distributions including; a stream of WIMPs, the standard dark halo, streams of WIMPs from Sikivie's late-infall (SLI) halo model, and streams with anisotropic velocity distributions. We show the results as distributions of the nuclei's directional differential recoil rate dRd? as a function of ?. We introduce a `folded' directional differential recoil rate dRd|?| to overcome the difficulty of head-tail discrimination in some WIMP's direct detectors. We conclude that dRd|?| can be helpful in recognizing cases of anisotropic streams and isotropic standard dark halo but not in the case of SLI streams.

  1. General analysis of B?K(*)?+?- decays at low recoil

    NASA Astrophysics Data System (ADS)

    Bobeth, Christoph; Hiller, Gudrun; van Dyk, Danny

    2013-02-01

    We analyze the angular distributions of B?K*(?K?)?+?- and B?K?+?- decays in the region of low hadronic recoil in a model-independent way by taking into account the complete set of dimension-six operators [s?b][??'?]. We obtain several novel low-recoil observables with high sensitivity to nonstandard-model Dirac structures, including CP asymmetries, which do not require flavor tagging. The transversity observables HT(1,3,4,5) are found to be insensitive to hadronic matrix elements and their uncertainties even when considering the complete set of operators. In the most general scenario we show that the low recoil operator product expansion can be probed at the few-percent level using the angular observable J7. Higher sensitivities are possible assuming no tensor contributions, specifically by testing the low-recoil relation |HT(1)|=1. We explicitly demonstrate the gain in reach of the low-recoil observables in accessing the ratio |C9/C10| compared to the forward-backward asymmetry, and probing CP-violating right-handed currents ImC10'. We give updated Standard Model predictions for key observables in B?K(*)?+?- decays.

  2. Calculation of recoil implantation profiles using known range statistics

    NASA Technical Reports Server (NTRS)

    Fung, C. D.; Avila, R. E.

    1985-01-01

    A method has been developed to calculate the depth distribution of recoil atoms that result from ion implantation onto a substrate covered with a thin surface layer. The calculation includes first order recoils considering projected range straggles, and lateral straggles of recoils but neglecting lateral straggles of projectiles. Projectile range distributions at intermediate energies in the surface layer are deduced from look-up tables of known range statistics. A great saving of computing time and human effort is thus attained in comparison with existing procedures. The method is used to calculate recoil profiles of oxygen from implantation of arsenic through SiO2 and of nitrogen from implantation of phosphorus through Si3N4 films on silicon. The calculated recoil profiles are in good agreement with results obtained by other investigators using the Boltzmann transport equation and they also compare very well with available experimental results in the literature. The deviation between calculated and experimental results is discussed in relation to lateral straggles. From this discussion, a range of surface layer thickness for which the method applies is recommended.

  3. Magnetoelectric effects in an organometallic quantum magnet

    NASA Astrophysics Data System (ADS)

    Zapf, V. S.; Sengupta, P.; Batista, C. D.; Nasreen, F.; Wolff-Fabris, F.; Paduan-Filho, A.

    2011-04-01

    Metal-organic materials constitute a new field in which to search for ferroelectricity and coupling between electricity and magnetism. We observe a magnetic field-induced change in the electric polarization, ?P(H), that reaches 50 ?C/m2 in single crystals of NiCl2-4SC(NH2)2 (DTN). DTN forms a tetragonal structure that breaks inversion symmetry with the electrically polar thiourea molecules [SC(NH2)] all tilted in the same direction along the c axis. The field H induces canted antiferromagnetism of the Ni S=1 spins between 2 and 12 T and our measurements show that the electric polarization increases monotonically in this range, saturating above 12 T. By modeling the microscopic origin of this magnetoelectric effect, we find that the leading contribution to ?P comes from the change in the crystal electric field, with a smaller contribution from magnetic exchange striction. The finite value of ?P induced by magnetostriction results from the polar nature of the thiourea molecules bonded to the Ni atoms, and it is amplified by the softness of these organic molecules.

  4. A theoretical estimation of orientational quantum effects in polar fluids

    NASA Astrophysics Data System (ADS)

    Woodward, C. E.; Nordholm, Sture

    Thermodynamic properties of classical polar fluids can be estimated from those of a simple fluid wherein the central pair potential has been chosen to account for pairwise orientational correlations. This mapping of polar to simple fluids has been extended to account for the quantization of rotational motion and the corresponding damping of orientational correlations. Choosing the model parameters to reflect HCl, HBr and HI we find large rotational quantum effects on the phase diagram and second virial coefficients if dispersion forces are neglected but only very minor such effects when the dominant dispersion forces are included.

  5. Nonlocal Memory Effects in the Dynamics of Open Quantum Systems

    NASA Astrophysics Data System (ADS)

    Laine, Elsi-Mari; Breuer, Heinz-Peter; Piilo, Jyrki; Li, Chuan-Feng; Guo, Guang-Can

    2012-05-01

    We explore the possibility to generate nonlocal dynamical maps of an open quantum system through local system-environment interactions. Employing a generic decoherence process induced by a local interaction Hamiltonian, we show that initial correlations in a composite environment can lead to nonlocal open system dynamics which exhibit strong memory effects, although the local dynamics is Markovian. In a model of two entangled photons interacting with two dephasing environments, we find a direct connection between the degree of memory effects and the amount of correlation in the initial environmental state. The results demonstrate that, contrary to conventional wisdom, enlarging an open system can change the dynamics from Markovian to non-Markovian.

  6. Quantum-tunneling-induced Kondo effect in single molecular magnets.

    PubMed

    Romeike, C; Wegewijs, M R; Hofstetter, W; Schoeller, H

    2006-05-19

    We consider transport through a single-molecule magnet strongly coupled to metallic electrodes. We demonstrate that, for a half-integer spin of the molecule, electron and spin tunneling cooperate to produce both quantum tunneling of the magnetic moment and a Kondo effect in the linear conductance. The Kondo temperature depends sensitively on the ratio of the transverse and easy-axis anisotropies in a nonmonotonic way. The magnetic symmetry of the transverse anisotropy imposes a selection rule on the total spin for the occurrence of the Kondo effect which deviates from the usual even-odd alternation. PMID:16803121

  7. SIMULATIONS OF RECOILING MASSIVE BLACK HOLES IN THE VIA LACTEA HALO

    SciTech Connect

    Guedes, J.; Madau, P.; Diemand, J.; Kuhlen, M.; Zemp, M.

    2009-09-10

    The coalescence of a massive black hole (MBH) binary leads to the gravitational-wave recoil of the system and its ejection from the galaxy core. We have carried out N-body simulations of the motion of a M{sub BH} = 3.7 x 10{sup 6} M{sub sun} MBH remnant in the 'Via Lactea I' simulation, a Milky Way-sized dark matter halo. The black hole receives a recoil velocity of V{sub kick} = 80, 120, 200, 300, and 400 km s{sup -1} at redshift 1.5, and its orbit is followed for over 1 Gyr within a 'live' host halo, subject only to gravity and dynamical friction against the dark matter background. We show that, owing to asphericities in the dark matter potential, the orbit of the MBH is highly nonradial, resulting in a significantly increased decay timescale compared to a spherical halo. The simulations are used to construct a semi-analytic model of the motion of the MBH in a time-varying triaxial Navarro-Frenk-White dark matter halo plus a spherical stellar bulge, where the dynamical friction force is calculated directly from the velocity dispersion tensor. Such a model should offer a realistic picture of the dynamics of kicked MBHs in situations where gas drag, friction by disk stars, and the flattening of the central cusp by the returning black hole are all negligible effects. We find that MBHs ejected with initial recoil velocities V{sub kick} {approx}> 500 km s{sup -1} do not return to the host center within a Hubble time. In a Milky Way-sized galaxy, a recoiling hole carrying a gaseous disk of initial mass {approx}M{sub BH} may shine as a quasar for a substantial fraction of its 'wandering' phase. The long decay timescales of kicked MBHs predicted by this study may thus be favorable to the detection of off-nuclear quasar activity.

  8. CHANDRA HIGH-RESOLUTION OBSERVATIONS OF CID-42, A CANDIDATE RECOILING SUPERMASSIVE BLACK HOLE

    SciTech Connect

    Civano, F.; Elvis, M.; Lanzuisi, G.; Aldcroft, T.; Trichas, M.; Fruscione, A.; Bongiorno, A.; Brusa, M.; Blecha, L.; Loeb, A.; Comastri, A.; Gilli, R.; Salvato, M.; Komossa, S.; Koekemoer, A.; Mainieri, V.; Piconcelli, E.; Vignali, C.

    2012-06-10

    We present Chandra High Resolution Camera observations of CID-42, a candidate recoiling supermassive black hole (SMBH) at z = 0.359 in the COSMOS survey. CID-42 shows two optical compact sources resolved in the HST/ACS image embedded in the same galaxy structure and a velocity offset of {approx}1300 km s{sup -1} between the H{beta} broad and narrow emission line, as presented by Civano et al. Two scenarios have been proposed to explain the properties of CID-42: a gravitational wave (GW) recoiling SMBH and a double Type 1/Type 2 active galactic nucleus (AGN) system, where one of the two is recoiling because of slingshot effect. In both scenarios, one of the optical nuclei hosts an unobscured AGN, while the other one, either an obscured AGN or a star-forming compact region. The X-ray Chandra data allow us to unambiguously resolve the X-ray emission and unveil the nature of the two optical sources in CID-42. We find that only one of the optical nuclei is responsible for the whole X-ray unobscured emission observed and a 3{sigma} upper limit on the flux of the second optical nucleus is measured. The upper limit on the X-ray luminosity plus the analysis of the multiwavelength spectral energy distribution indicate the presence of a star-forming region in the second source rather than an obscured SMBH, thus favoring the GW recoil scenario. However, the presence of a very obscured SMBH cannot be fully ruled out. A new X-ray feature, in a SW direction with respect to the main source, is discovered and discussed.

  9. Quenching factor for low-energy nuclear recoils in a plastic scintillator

    NASA Astrophysics Data System (ADS)

    Reichhart, L.; Akimov, D. Yu.; Arajo, H. M.; Barnes, E. J.; Belov, V. A.; Burenkov, A. A.; Chepel, V.; Currie, A.; DeViveiros, L.; Edwards, B.; Francis, V.; Ghag, C.; Hollingsworth, A.; Horn, M.; Kalmus, G. E.; Kobyakin, A. S.; Kovalenko, A. G.; Lebedenko, V. N.; Lindote, A.; Lopes, M. I.; Lscher, R.; Majewski, P.; Murphy, A. St J.; Neves, F.; Paling, S. M.; Pinto da Cunha, J.; Preece, R.; Quenby, J. J.; Scovell, P. R.; Silva, C.; Solovov, V. N.; Smith, N. J. T.; Smith, P. F.; Stekhanov, V. N.; Sumner, T. J.; Thorne, C.; Walker, R. J.

    2012-06-01

    Plastic scintillators are widely used in industry, medicine, and scientific research, including nuclear and particle physics. Although one of their most common applications is in neutron detection, experimental data on their response to low-energy nuclear recoils are scarce. Here, the relative scintillation efficiency for neutron-induced nuclear recoils in a polystyrene-based plastic scintillator (UPS-923A) is presented, exploring recoil energies between 125 and 850 keV. Monte Carlo simulations, incorporating light collection efficiency and energy resolution effects, are used to generate neutron scattering spectra which are matched to observed distributions of scintillation signals to parameterize the energy-dependent quenching factor. At energies above 300 keV the dependence is reasonably described using the semiempirical formulation of Birks and a kB factor of (0.0140.002) g MeV-1 cm-2 has been determined. Below that energy, the measured quenching factor falls more steeply than predicted by the Birks formalism.

  10. A compact high-resolution elastic recoil detection system for lithium depth profiling

    NASA Astrophysics Data System (ADS)

    Nikko, Masataka; Nakajima, Kaoru; Kimura, Kenji

    2015-07-01

    A compact high-resolution elastic recoil detection analysis (ERDA) system was developed for precise Li analysis. 200-400 keV He+ ions were used as primary ions and the energy spectra of recoiled Li ions were measured using a magnetic spectrometer. Due to its dispersion the background originating from the scattered primary ions is reduced. The recoiled ions of the substrate other than Li, which may also contribute to the background, were rejected by a thin mylar foil placed in front of a focal plane detector. An electrostatic quadrupole lens was installed at the entrance of the magnetic spectrometer to improve the depth resolution by correcting the effect of the kinematic broadening. The performance of the developed high-resolution ERDA was examined by measuring several samples. A thin Li layer (1.5 1015 cm-2) deposited on a graphite surface was clearly observed and the detection limit was estimated to be less than 0.01 ML under typical measurement conditions. The depth resolution was estimated to be 0.5 nm at the surface and was better than 3 nm in the surface region within 5 nm from the surface.

  11. Clean recoil implantation of the 100Pd/Rh TDPAC probe using a solenoidal separator

    NASA Astrophysics Data System (ADS)

    Abiona, A. A.; Kemp, W. J.; Williams, E.; Timmers, H.

    2012-10-01

    The synthesis and recoil implantation of the 100Pd/Rh probe for time differential perturbed angular correlation (TDPAC) spectroscopy using the solenoidal reaction product separator SOLITAIRE has been demonstrated for the first time. The separator suppresses the co-implantation of the intense flux of elastically scattered projectile ions that can affect results obtained with the hyperfine interactions technique. Using three different fusion evaporation reactions, the solenoid field was optimised at 4.5 T to achieve a concentrated, circular focus of evaporation residue ions with a lateral FWHM of 20 mm. Employing the reaction 92Zr(12C,4n)100Pd several samples have been recoil-implanted with the 100Pd/Rh probe. Gamma-ray spectroscopy of a silver sample and a TDPAC measurement on zinc confirm that the new preparation technique is effective. The ratio function measured with TDPAC of an undoped germanium sample may indicate that palladium-defect pairs are absent when implanting with SOLITAIRE. However, a direct comparison with TDPAC results for germanium samples prepared with conventional recoil implantation, which does not suppress the flux of elastics, does not support this assertion.

  12. Recoil polarization observables in the electroproduction of K mesons and Λ's from the proton

    NASA Astrophysics Data System (ADS)

    Maxwell, Oren V.

    2014-09-01

    A model developed previously to investigate the electromagnetic production of strangeness from the proton is used to investigate single and double recoil polarization observables in the reaction ep →e'K+Λ in the relativistic impulse approximation. The formalism is based on a tree-level, effective Lagrangian model, which incorporates a variety of baryon resonances with spins up to 5/2 and the two kaon resonances, K(892) and K1(1270). The parameters of the model were fit to a large pool of photoproduction data from the CLAS, GRAAL, SAPHIR, and LEPS collaborations and to CLAS data for the virtual photoproduction structure functions σU,σT,σL,σTT,σLT, and σLT'. Using two different versions of this model, results are presented for three recoil polarization asymmetries that have been measured recently at CLAS. A new fit is then presented which incorporates the new polarization data in the fitted data set. Results obtained with this new fit are presented for six recoil polarization asymmetries and compared with results from one of the previous fits.

  13. Experimental simulation of the Unruh effect on an NMR quantum simulator

    NASA Astrophysics Data System (ADS)

    Jin, FangZhou; Chen, HongWei; Rong, Xing; Zhou, Hui; Shi, MingJun; Zhang, Qi; Ju, ChenYong; Cai, YiFu; Luo, ShunLong; Peng, XinHua; Du, JiangFeng

    2016-03-01

    The Unruh effect is one of the most fundamental manifestations of the fact that the particle content of a field theory is observer dependent. However, there has been so far no experimental verification of this effect, as the associated temperatures lie far below any observable threshold. Recently, physical phenomena, which are of great experimental challenge, have been investigated by quantum simulations in various fields. Here we perform a proof-of-principle simulation of the evolution of fermionic modes under the Unruh effect with a nuclear magnetic resonance (NMR) quantum simulator. By the quantum simulator, we experimentally demonstrate the behavior of Unruh temperature with acceleration, and we further investigate the quantum correlations quantified by quantum discord between two fermionic modes as seen by two relatively accelerated observers. It is shown that the quantum correlations can be created by the Unruh effect from the classically correlated states. Our work may provide a promising way to explore the quantum physics of accelerated systems.

  14. Fission product release from nuclear fuel by recoil and knockout

    NASA Astrophysics Data System (ADS)

    Lewis, B. J.

    1987-03-01

    An analytical model has been developed to describe the fission product release from nuclear fuel arising from the surface-fission release mechanisms of recoil and knockout. Release expressions are evaluated and compared to the short-lived activity measurements from in-reactor experiments with intact operating fuel. Recoil is shown to be an important process for releasing fission products from free UO 2 surfaces into the fuel-to-sheath gap. The model is also applied to tramp uranium in a power reactor primary heat transport circuit where it is demonstrated that recoil is the dominant release mechanism for small particles of fuel which are deposited on in-core surfaces. A methodology is established whereby release from surface contamination can be distinguished from that of fuel pin failure.

  15. Squeezed State Effects on Continuous Variable Quantum Erasing

    NASA Astrophysics Data System (ADS)

    Bonanno, Peter; Kasisomayajula, Vijay; Russo, Onofrio

    2008-03-01

    Experimental verification of complementarity using quantum erasing for the continuous variable (CV) infinite dimensional Hilbert space has been considered. [1] The complemetary pair is that of the canonically conjugate amplitude and phase quadratures of light. The amplitude quadrature is labeled to a squeezed meter signal by quantum nondemolition (QND) [2] entanglement coupling. [3] Knowledge of which eigenstate (WE) can be obtained by measuring this amplitude in the meter state, and can thereafter be `lost' by measuring the quadrature phase of the meter, thus restoring the quadrature phase of the signal beam in a process known as quantum erasure. [4] The coupling, i.e. the labeling of the signal state to the meter state, is implemented with a beam splitter coupled to the squeezed light meter beam. [4] We investigate the effects of using the unitary squeeze operator S(z)=exp.5ex1 -.1em/ -.15em.25ex2 (z*a^2 - za^+2) where z = re^i(squeezing angle) on selected coherent states under certain conditions. [5,6] [1] U. L. Anderson et al., Phys. Rev. Lett. 93, 100403 (2004). [2] V. B. Braginsky et al., Science 209, 547 (1980). [3] R. Bruckmeimer et al., Phys. Rev. Lett. 79, 43 (1997). [4] P. Grangier et al., Nature 396, 537 (1998). [5] C. M. Caves, Phys. Rev. D 23, 1693 (1981). [6] D. Stoler, Phys. Rev. D. 1, 3217 (1970), D. Stoler, Phys. Rev. D. 4, 1925 (1971). .

  16. Quantum anomalous Hall effect in magnetic topological insulators

    NASA Astrophysics Data System (ADS)

    Wang, Jing; Lian, Biao; Zhang, Shou-Cheng

    2015-12-01

    The search for topologically non-trivial states of matter has become an important goal for condensed matter physics. Here, we give a theoretical introduction to the quantum anomalous Hall (QAH) effect based on magnetic topological insulators in two-dimensions (2D) and three-dimensions (3D). In 2D topological insulators, magnetic order breaks the symmetry between the counter-propagating helical edge states, and as a result, the quantum spin Hall effect can evolve into the QAH effect. In 3D, magnetic order opens up a gap for the topological surface states, and chiral edge state has been predicted to exist on the magnetic domain walls. We present the phase diagram in thin films of a magnetic topological insulator and review the basic mechanism of ferromagnetic order in magnetically doped topological insulators. We also review the recent experimental observation of the QAH effect. We discuss more recent theoretical work on the coexistence of the helical and chiral edge states, multi-channel chiral edge states, the theory of the plateau transition, and the thickness dependence in the QAH effect.

  17. Quantum Hall effect on the Grassmannians Gr2(CN)

    NASA Astrophysics Data System (ADS)

    Ball?, F.; Behtash, A.; Krko?lu, S.; nal, G.

    2014-05-01

    Quantum Hall effects on the complex Grassmann manifolds Gr2(CN) are formulated. We set up the Landau problem in Gr2(CN) and solve it using group theoretical techniques and provide the energy spectrum and the eigenstates in terms of the SU(N) Wigner D functions for charged particles on Gr2(CN) under the influence of Abelian and non-Abelian background magnetic monopoles or a combination of these. In particular, for the simplest case of Gr2(C4), we explicitly write down the U(1) background gauge field as well as the single- and many-particle eigenstates by introducing the Plcker coordinates and show by calculating the two-point correlation function that the lowest Landau level at filling factor ? =1 forms an incompressible fluid. Our results are in agreement with the previous results in the literature for the quantum Hall effect on CPN and generalize them to all Gr2(CN) in a suitable manner. Finally, we heuristically identify a relation between the U(1) Hall effect on Gr2(C4) and the Hall effect on the odd sphere S5, which is yet to be investigated in detail, by appealing to the already-known analogous relations between the Hall effects on CP3 and CP7 and those on the spheres S4 and S8, respectively.

  18. Quantum Confined Stark Effect in a GaAs/AlGaAs Nanowire Quantum Well Tube Device: Probing Exciton Localization.

    PubMed

    Badada, Bekele H; Shi, Teng; Jackson, Howard E; Smith, Leigh M; Zheng, Changlin; Etheridge, Joanne; Gao, Qiang; Tan, H Hoe; Jagadish, Chennupati

    2015-12-01

    In this Letter, we explore the nature of exciton localization in single GaAs/AlGaAs nanowire quantum well tube (QWT) devices using photocurrent (PC) spectroscopy combined with simultaneous photoluminescence (PL) and photoluminescence excitation (PLE) measurements. Excitons confined to GaAs quantum well tubes of 8 and 4 nm widths embedded into an AlGaAs barrier are seen to ionize at high bias levels. Spectroscopic signatures of the ground and excited states confined to the QWT seen in PL, PLE, and PC data are consistent with simple numerical calculations. The demonstration of good electrical contact with the QWTs enables the study of Stark effect shifts in the sharp emission lines of excitons localized to quantum dot-like states within the QWT. Atomic resolution cross-sectional TEM measurements and an analysis of the quantum confined Stark effect of these dots provide insights into the nature of the exciton localization in these nanostructures. PMID:26562619

  19. Photodissociation of laboratory oriented molecules: Revealing molecular frame properties of nonaxial recoil

    SciTech Connect

    Brom, Alrik J. van den; Rakitzis, T. Peter; Janssen, Maurice H.M.

    2004-12-15

    We report the photodissociation of laboratory oriented OCS molecules. A molecular beam of OCS molecules is hexapole state-selected and spatially oriented in the electric field of a velocity map imaging lens. The oriented OCS molecules are dissociated at 230 nm with the linear polarization set at 45 deg. to the orientation direction of the OCS molecules. The CO({nu}=0,J) photofragments are quantum state-selectively ionized by the same 230 nm pulse and the angular distribution is measured using the velocity map imaging technique. The observed CO({nu}=0,J) images are strongly asymmetric and the degree of asymmetry varies with the CO rotational state J. From the observed asymmetry in the laboratory frame we can directly extract the molecular frame angles between the final photofragment recoil velocity and the permanent dipole moment and the transition dipole moment. The data for CO fragments with high rotational excitation reveal that the dissociation dynamics is highly nonaxial, even though conventional wisdom suggests that the nearly limiting {beta} parameter results from fast axial recoil dynamics. From our data we can extract the relative contribution of parallel and perpendicular transitions at 230 nm excitation.

  20. {theta} parameter in loop quantum gravity: Effects on quantum geometry and black hole entropy

    SciTech Connect

    Rezende, Danilo Jimenez; Perez, Alejandro

    2008-10-15

    The precise analog of the {theta}-quantization ambiguity of Yang-Mills theory exists for the real SU(2) connection formulation of general relativity. As in the former case {theta} labels representations of large gauge transformations, which are superselection sectors in loop quantum gravity. We show that unless {theta}=0, the (kinematical) geometric operators such as area and volume are not well defined on spin network states. More precisely the intersection of their domain with the dense set Cyl in the kinematical Hilbert space H of loop quantum gravity is empty. The absence of a well-defined notion of area operator acting on spin network states seems at first in conflict with the expected finite black hole entropy. However, we show that the black hole (isolated) horizon area--which in contrast to kinematical area is a (Dirac) physical observable--is indeed well defined, and quantized so that the black hole entropy is proportional to the area. The effect of {theta} is negligible in the semiclassical limit where proportionality to area holds.

  1. The role of quantum effects in proton transfer reactions in enzymes: quantum tunneling in a noisy environment?

    NASA Astrophysics Data System (ADS)

    Bothma, Jacques P.; Gilmore, Joel B.; McKenzie, Ross H.

    2010-05-01

    We consider the role of quantum effects in the transfer of hydrogen-like species in enzyme-catalyzed reactions. This review is stimulated by claims that the observed magnitude and temperature dependence of kinetic isotope effects (KIEs) implies that quantum tunneling below the energy barrier associated with the transition state significantly enhances the reaction rate in many enzymes. We review the path integral approach and the Caldeira-Leggett model, which provides a general framework to describe and understand tunneling in a quantum system that interacts with a noisy environment at nonzero temperature. Here the quantum system is the active site of the enzyme, and the environment is the surrounding protein and water. Tunneling well below the barrier only occurs for temperatures less than a temperature T0, which is determined by the curvature of the potential energy surface near the top of the barrier. We argue that for most enzymes this temperature is less than room temperature. We review typical values for the parameters in the Caldeira-Leggett Hamiltonian, including the frequency-dependent friction and noise due to the environment. For physically reasonable parameters, we show that quantum transition state theory gives a quantitative description of the temperature dependence and magnitude of KIEs for two classes of enzymes that have been claimed to exhibit signatures of quantum tunneling. The only quantum effects are those associated with the transition state, both reflection at the barrier top and tunneling just below the barrier. We establish that the friction and noise due to the environment are weak and only slightly modify the reaction rate. Furthermore, at room temperature and for typical energy barriers environmental fluctuations with frequencies much less than 1000 cm-1 do not have a significant effect on quantum corrections to the reaction rate. This is essentially because the time scales associated with the dynamics of proton transfer are faster than much of the low-frequency noise associated with the protein and solvent.

  2. Stopping Power of Au for Ti Using Elastic Recoil Technique

    SciTech Connect

    Linares, R.; Freire, J. A.; Ribas, R. V.; Medina, N. H.; Oliveira, J. R. B.; Seale, W. A.; Cybulska, E. W.; Wiedemann, K. T.; Allegro, P. R.; Toufen, D. L.

    2009-06-03

    The slowing down of heavy ions in matter is still not well understood especially at low energies (<0.5 MeV/u). In this contribution we present new experimental data for the stopping power of Au for Ti ions using an elastic recoil technique where a heavy-ion beam at low energies is produced by elastic scattering of an energetic primary beam imping on a thin target. Atoms from the target recoil at low energies. We compare our experimental data with previous data and with semi-empirical and theoretical models.

  3. Self-screening of the quantum confined Stark effect by the polarization induced bulk charges in the quantum barriers

    SciTech Connect

    Zhang, Zi-Hui; Liu, Wei; Ju, Zhengang; Tiam Tan, Swee; Ji, Yun; Kyaw, Zabu; Zhang, Xueliang; Wang, Liancheng; Wei Sun, Xiao E-mail: volkan@stanfordalumni.org; Volkan Demir, Hilmi E-mail: volkan@stanfordalumni.org

    2014-06-16

    InGaN/GaN light-emitting diodes (LEDs) grown along the polar orientations significantly suffer from the quantum confined Stark effect (QCSE) caused by the strong polarization induced electric field in the quantum wells, which is a fundamental problem intrinsic to the III-nitrides. Here, we show that the QCSE is self-screened by the polarization induced bulk charges enabled by designing quantum barriers. The InN composition of the InGaN quantum barrier graded along the growth orientation opportunely generates the polarization induced bulk charges in the quantum barrier, which well compensate the polarization induced interface charges, thus avoiding the electric field in the quantum wells. Consequently, the optical output power and the external quantum efficiency are substantially improved for the LEDs. The ability to self-screen the QCSE using polarization induced bulk charges opens up new possibilities for device engineering of III-nitrides not only in LEDs but also in other optoelectronic devices.

  4. Quantum effects on compressional Alfven waves in compensated semiconductors

    SciTech Connect

    Amin, M. R.

    2015-03-15

    Amplitude modulation of a compressional Alfven wave in compensated electron-hole semiconductor plasmas is considered in the quantum magnetohydrodynamic regime in this paper. The important ingredients of this study are the inclusion of the particle degeneracy pressure, exchange-correlation potential, and the quantum diffraction effects via the Bohm potential in the momentum balance equations of the charge carriers. A modified nonlinear Schrdinger equation is derived for the evolution of the slowly varying amplitude of the compressional Alfven wave by employing the standard reductive perturbation technique. Typical values of the parameters for GaAs, GaSb, and GaN semiconductors are considered in analyzing the linear and nonlinear dispersions of the compressional Alfven wave. Detailed analysis of the modulation instability in the long-wavelength regime is presented. For typical parameter ranges of the semiconductor plasmas and at the long-wavelength regime, it is found that the wave is modulationally unstable above a certain critical wavenumber. Effects of the exchange-correlation potential and the Bohm potential in the wave dynamics are also studied. It is found that the effect of the Bohm potential may be neglected in comparison with the effect of the exchange-correlation potential in the linear and nonlinear dispersions of the compressional Alfven wave.

  5. Mirages and many-body effects in quantum corrals

    NASA Astrophysics Data System (ADS)

    Aligia, A. A.; Lobos, A. M.

    2005-04-01

    In an experiment on quantum mirages, confinement of surface states in an elliptical corral has been used to project the Kondo effect from one focus where a magnetic impurity was placed to the other, empty, focus. The signature of the Kondo effect is seen as a Fano antiresonance in scanning tunnelling spectroscopy. This experiment combines the many-body physics of the Kondo effect with the subtle effects of confinement. In this work we review the essential physics of the quantum mirage experiment, and present new calculations involving other geometries and more than one impurity in the corral, which should be relevant for other experiments that are being made, and to discern the relative importance of the hybridization of the impurity with surface (Vs) and bulk (Vb) states. The intensity of the mirage imposes a lower bound on Vs/Vb which we estimate. Our emphasis is on the main physical ingredients of the phenomenon and the many-body aspects, like the dependence of the observed differential conductance on the geometry, which cannot be calculated with alternative one-body theories. The system is described with an Anderson impurity model solved using complementary approaches: theory of perturbation in the Coulomb repulsion U, slave bosons in the mean field and exact diagonalization plus embedding.

  6. Quantum effects on compressional Alfven waves in compensated semiconductors

    NASA Astrophysics Data System (ADS)

    Amin, M. R.

    2015-03-01

    Amplitude modulation of a compressional Alfven wave in compensated electron-hole semiconductor plasmas is considered in the quantum magnetohydrodynamic regime in this paper. The important ingredients of this study are the inclusion of the particle degeneracy pressure, exchange-correlation potential, and the quantum diffraction effects via the Bohm potential in the momentum balance equations of the charge carriers. A modified nonlinear Schrdinger equation is derived for the evolution of the slowly varying amplitude of the compressional Alfven wave by employing the standard reductive perturbation technique. Typical values of the parameters for GaAs, GaSb, and GaN semiconductors are considered in analyzing the linear and nonlinear dispersions of the compressional Alfven wave. Detailed analysis of the modulation instability in the long-wavelength regime is presented. For typical parameter ranges of the semiconductor plasmas and at the long-wavelength regime, it is found that the wave is modulationally unstable above a certain critical wavenumber. Effects of the exchange-correlation potential and the Bohm potential in the wave dynamics are also studied. It is found that the effect of the Bohm potential may be neglected in comparison with the effect of the exchange-correlation potential in the linear and nonlinear dispersions of the compressional Alfven wave.

  7. Effect of quantum nuclear motion on hydrogen bonding

    NASA Astrophysics Data System (ADS)

    McKenzie, Ross H.; Bekker, Christiaan; Athokpam, Bijyalaxmi; Ramesh, Sai G.

    2014-05-01

    This work considers how the properties of hydrogen bonded complexes, X-H⋯Y, are modified by the quantum motion of the shared proton. Using a simple two-diabatic state model Hamiltonian, the analysis of the symmetric case, where the donor (X) and acceptor (Y) have the same proton affinity, is carried out. For quantitative comparisons, a parametrization specific to the O-H⋯O complexes is used. The vibrational energy levels of the one-dimensional ground state adiabatic potential of the model are used to make quantitative comparisons with a vast body of condensed phase data, spanning a donor-acceptor separation (R) range of about 2.4 - 3.0 , i.e., from strong to weak hydrogen bonds. The position of the proton (which determines the X-H bond length) and its longitudinal vibrational frequency, along with the isotope effects in both are described quantitatively. An analysis of the secondary geometric isotope effect, using a simple extension of the two-state model, yields an improved agreement of the predicted variation with R of frequency isotope effects. The role of bending modes is also considered: their quantum effects compete with those of the stretching mode for weak to moderate H-bond strengths. In spite of the economy in the parametrization of the model used, it offers key insights into the defining features of H-bonds, and semi-quantitatively captures several trends.

  8. Effect of quantum nuclear motion on hydrogen bonding

    SciTech Connect

    McKenzie, Ross H. Bekker, Christiaan; Athokpam, Bijyalaxmi; Ramesh, Sai G.

    2014-05-07

    This work considers how the properties of hydrogen bonded complexes, X–H⋯Y, are modified by the quantum motion of the shared proton. Using a simple two-diabatic state model Hamiltonian, the analysis of the symmetric case, where the donor (X) and acceptor (Y) have the same proton affinity, is carried out. For quantitative comparisons, a parametrization specific to the O–H⋯O complexes is used. The vibrational energy levels of the one-dimensional ground state adiabatic potential of the model are used to make quantitative comparisons with a vast body of condensed phase data, spanning a donor-acceptor separation (R) range of about 2.4 − 3.0 Å, i.e., from strong to weak hydrogen bonds. The position of the proton (which determines the X–H bond length) and its longitudinal vibrational frequency, along with the isotope effects in both are described quantitatively. An analysis of the secondary geometric isotope effect, using a simple extension of the two-state model, yields an improved agreement of the predicted variation with R of frequency isotope effects. The role of bending modes is also considered: their quantum effects compete with those of the stretching mode for weak to moderate H-bond strengths. In spite of the economy in the parametrization of the model used, it offers key insights into the defining features of H-bonds, and semi-quantitatively captures several trends.

  9. The quantum theory analysis of electrical and thermal effects at core/shell quantum dots and laser interactions

    NASA Astrophysics Data System (ADS)

    Wen, Yuanbin; Xu, Lin; Feng, Xiaobo; Duan, Jianjin; Ye, Miao; Yin, Liming; Jiang, Yanling

    2014-01-01

    The interaction between laser and C-SQDB bio-molecule which is related with the fluorescence effect, thermal effects and eliectrical effect from the coupling structure of quantum dots bonded with bio-molecules and of have been wildly researched for the potential application in life science. .As one of the most problems, the electrical effects are analyzed by employing quantum theory in this paper and The research will be conducive to the practical application of C-S QDBS in medical science.

  10. Edge states and integer quantum Hall effect in topological insulator thin films

    PubMed Central

    Zhang, Song-Bo; Lu, Hai-Zhou; Shen, Shun-Qing

    2015-01-01

    The integer quantum Hall effect is a topological state of quantum matter in two dimensions, and has recently been observed in three-dimensional topological insulator thin films. Here we study the Landau levels and edge states of surface Dirac fermions in topological insulators under strong magnetic field. We examine the formation of the quantum plateaux of the Hall conductance and find two different patterns, in one pattern the filling number covers all integers while only odd integers in the other. We focus on the quantum plateau closest to zero energy and demonstrate the breakdown of the quantum spin Hall effect resulting from structure inversion asymmetry. The phase diagrams of the quantum Hall states are presented as functions of magnetic field, gate voltage and chemical potential. This work establishes an intuitive picture of the edge states to understand the integer quantum Hall effect for Dirac electrons in topological insulator thin films. PMID:26304795

  11. Repulsive gravitational effect of a quantum wave packet and experimental scheme with superfluid helium

    NASA Astrophysics Data System (ADS)

    Xiong, Hongwei

    2015-08-01

    We consider the gravitational effect of quantum wave packets when quantum mechanics, gravity, and thermodynamics are simultaneously considered. Under the assumption of a thermodynamic origin of gravity, we propose a general equation to describe the gravitational effect of quantum wave packets. In the classical limit, this equation agrees with Newton's law of gravitation. For quantum wave packets, however, it predicts a repulsive gravitational effect. We propose an experimental scheme using superfluid helium to test this repulsive gravitational effect. Our studies show that, with present technology such as superconducting gravimetry and cold atom interferometry, tests of the repulsive gravitational effect for superfluid helium are within experimental reach.

  12. Relation between quantum effects in general relativity and embedding theory

    NASA Astrophysics Data System (ADS)

    Paston, S. A.

    2015-10-01

    We discuss results relevant to the relation between quantum effects in a Riemannian space and on the surface appearing as a result of its isometric embedding in a flat space of a higher dimension. We discuss the correspondence between the Hawking effect fixed by an observer in the Riemannian space with a horizon and the Unruh effect related to an accelerated motion of this observer in the ambient space. We present examples for which this correspondence holds and examples for which there is no correspondence. We describe the general form of the hyperbolic embedding of the metric with a horizon smoothly covering the horizon and prove that there is a correspondence between the Hawking and Unruh effects for this embedding. We also discuss the possibility of relating two-point functions in a Riemannian space and the ambient space in which it is embedded. We obtain restrictions on the geometric parameters of the embedding for which such a relation is known.

  13. Temperature effects on quantum interference in molecular junctions

    NASA Astrophysics Data System (ADS)

    Markussen, Troels; Thygesen, Kristian S.

    2014-02-01

    A number of experiments have demonstrated that destructive quantum interference (QI) effects in molecular junctions lead to very low conductances even at room temperature. On the other hand, another recent experiment showed increasing conductance with temperature which was attributed to decoherence effects destroying QI at finite temperatures. Here we study the influence of finite temperatures and electron-phonon interactions on QI in molecular junctions. Two different models leading to two inherently different types of QI effects are considered. Each model is exemplified by specific molecules and studied using first-principles calculations. We find that the molecules exhibiting QI show a much stronger temperature dependence of the conductance compared to molecules without QI. However, the large QI-induced suppression of the conductance remains, showing that QI effects are indeed robust against finite temperatures and inelastic scattering.

  14. Monitoring the 1 {Omega} standard resistor by quantum Hall effect

    SciTech Connect

    Kinoshita, Joji; Nakanishi, Masakazu; Yoshihiro, Kazuo

    1994-12-31

    Resistance standards at ETL are maintained by quantum Hall effect. Resistance of the 1 {Omega} resistor named 69J101 is monitored. The result is R{sub 69J101} = 1 - (6.682 {+-} 0.018) x 10{sup -6} + (0.110 {+-} 0.003) x 10{sup -6} t {Omega} where t is time in years from January 1, 1994. The difference of 1 {Omega} standard between ETL and BIPM on 1990 international comparison is reduced from -0.128 ppm to -0.044 ppm.

  15. Quantum Effects in Nanoscale MOSFET Devices at Low Temperature

    NASA Astrophysics Data System (ADS)

    Day, Alexandra

    2014-03-01

    MOSFET transistors are a key component of virtually all modern electronic devices. Today's most advanced MOSFETs are small enough that quantum mechanical effects become relevant when considering their function and use. This project, completed at the National Institute of Standards and Technology as part of a Society of Physics Students internship, presents a first step in describing the theoretical behavior of nanoscale MOSFETs at low temperature. I acknowledge generous support from the Society of Physics Students and the National Institute of Standards and Technology.

  16. Role of Quantum Effects in the GlassTransition.

    SciTech Connect

    Novikov, Vladimir; Sokolov, Alexei P

    2013-01-01

    It is shown that quantum effects lead to a significant decrease of the glass transition temperature Tg with respect to the melting temperature Tm, so that the ratio Tg=Tm can be much smaller than the typical value of 2=3 in materials where Tg is near or below 60 K. Furthermore, it is demonstrated that the viscosity or structural relaxation time in such low temperature glass formers should exhibit highly unusual temperature dependence, namely a decrease of the apparent activation energy upon approaching Tg (instead of traditional increase).

  17. Quantum Hall effect in supersymmetric Chern-Simons theories

    NASA Astrophysics Data System (ADS)

    Tong, David; Turner, Carl

    2015-12-01

    We introduce a supersymmetric Chern-Simons theory whose low energy physics is that of the fractional quantum Hall effect. The supersymmetry allows us to solve the theory analytically. We quantize the vortices and, by relating their dynamics to a matrix model, show that their ground state wave function is in the same universality class as the Laughlin state. We further construct coherent state representations of the excitations of a finite number of vortices. These are quasiholes. By an explicit computation of the Berry phase, without resorting to a plasma analogy, we show that these excitations have fractional charge and spin.

  18. Four-Dimensional Quantum Hall Effect with Ultracold Atoms

    NASA Astrophysics Data System (ADS)

    Price, H. M.; Zilberberg, O.; Ozawa, T.; Carusotto, I.; Goldman, N.

    2015-11-01

    We propose a realistic scheme to detect the 4D quantum Hall effect using ultracold atoms. Based on contemporary technology, motion along a synthetic fourth dimension can be accomplished through controlled transitions between internal states of atoms arranged in a 3D optical lattice. From a semiclassical analysis, we identify the linear and nonlinear quantized current responses of our 4D model, relating these to the topology of the Bloch bands. We then propose experimental protocols, based on current or center-of-mass-drift measurements, to extract the topological second Chern number. Our proposal sets the stage for the exploration of novel topological phases in higher dimensions.

  19. Scalar spin chirality and quantum hall effect on triangular lattices

    SciTech Connect

    Martin, Ivar; Batista, Cristian D

    2008-01-01

    We study the Kondo Lattice and Hubbard models on a triangular lattice for band filling factor 3/4. We show that a simple non-coplanar chiral spin ordering (scalar spin chirality) is naturally realized in both models due to perfect nesting of the fermi surface. The resulting triple-Q magnetic ordering is a natural counterpart of the collinear Neel ordering of the half-filled square lattice Hubbard model. We show that the obtained chiral phase exhibits a spontaneous quantum Hall-effect with {sigma}{sub xy} = e{sup 2}/h.

  20. Charge Kondo effect in a triple quantum dot

    NASA Astrophysics Data System (ADS)

    Yoo, Gwangsu; Park, Jinhong; Lee, S. S.-B.; Sim, H.-S.

    2014-03-01

    We predict that the charge Kondo effect appears in a triangular triple quantum dot. The system has two-fold degenerate ground-state charge configurations, interdot Coulomb interactions, lead-dot electron tunnelings, but no interdot electron tunneling. We show, using bosonization and refermionization, that the system is described by the anisotropic Kondo model. The anisotropy can be tuned by changing lead-dot electron tunneling strength, which allows one to experimentally explore the transition between the ferromagnetic non-Fermi liquid and antiferromagnetic Kondo phases in the Kondo phase diagram. Using numerical renormalization group method, we demonstrate that the transition is manifested in electron conductances through the dot.

  1. Quantum Zeno Effect in an Unstable System with NMR

    NASA Astrophysics Data System (ADS)

    Matsuzaki, Yuichiro; Tanaka, Hirotaka

    2016-01-01

    We theoretically propose a scheme for the verification of the quantum Zeno effect (QZE) to suppress a decay process with nuclear magnetic resonance (NMR). Nuclear spins are affected by low-frequency noise, and thus we can naturally observe non exponential decay behavior, which is a prerequisite in observing the QZE. We also show that a key component for verifying the QZE, namely, the measurement of a nuclear spin, can be realized with NMR using the current technology by using a measurement process with a non selective architecture.

  2. Quantum anomalous Hall effect in topological insulator memory

    SciTech Connect

    Jalil, Mansoor B. A.; Tan, S. G.; Siu, Z. B.

    2015-05-07

    We theoretically investigate the quantum anomalous Hall effect (QAHE) in a magnetically coupled three-dimensional-topological insulator (3D-TI) system. We apply the generalized spin-orbit coupling Hamiltonian to obtain the Hall conductivity σ{sup xy} of the system. The underlying topology of the QAHE phenomenon is then analyzed to show the quantization of σ{sup xy} and its relation to the Berry phase of the system. Finally, we analyze the feasibility of utilizing σ{sup xy} as a memory read-out in a 3D-TI based memory at finite temperatures, with comparison to known magnetically doped 3D-TIs.

  3. Configuration interaction matrix elements for the quantum Hall effect

    NASA Astrophysics Data System (ADS)

    Wooten, Rachel; Macek, Joseph

    2015-03-01

    In the spherical model of the quantum Hall system, the two-body matrix elements and pseudopotentials can be found analytically in terms of a general scalar pair interaction potential by expressing the pair interaction as a weighted sum over Legendre polynomials. For non-infinite systems, only a finite set of terms in the potential expansion contribute to the interactions; the contributing terms define an effective spatial potential for the system. The connection between the effective spatial potential and the pseudopotential is one-to-one for finite systems, and any completely defined model pseudopotential can be analytically inverted to give a unique corresponding spatial potential. This technique of inverting the pseudopotential to derive effective spatial potentials may be of use for developing accurate model spatial potentials for quantum Monte Carlo simulations. We demonstrate the technique and the corresponding spatial potentials for a few example model pseudopotentials. Supported by Office of Basic Energy Sciences, U.S. DOE, Grant DE-FG02-02ER15283 to the University of Tennessee.

  4. Quantum effects in diamond isotopes at high pressures

    NASA Astrophysics Data System (ADS)

    Enkovich, P. V.; Brazhkin, V. V.; Lyapin, S. G.; Kanda, H.; Novikov, A. P.; Stishov, S. M.

    2016-01-01

    An influence of quantum effects on the equation of states and phase transitions in compressed matter is of primary interest in the physics of giant planets and in astrophysics. To gain some insight into the problem we carried out precision Raman studies of diamond isotopes 12C, 13C, and their mixture 12.5C in the pressure range up to 73 GPa using helium as a hydrostatic pressure-transmitting medium. The ratio of Raman frequencies of 12 and 13C diamonds, which differs from the classical value (1.0408), was found to slightly, but nonmonotonically, change up to 60 GPa. One can propose that the quantum effects in diamonds initially are enhanced on compression to ˜30 GPa and then decrease up to the maximum experimentally measured pressure. This behavior probably unveils hidden features of covalent interaction in crystals. Examination of the isotopically mixed 12.5C diamond shows that the effective mass determining the Raman frequency varies under compression from 12.38 a.u. at ambient pressure to 12.33 a.u. at pressure of 73 GPa.

  5. Interference Effects in the Conductance of Multilevel Quantum Dots

    SciTech Connect

    Busser, Carlos A; Martins, G. B.; Al Hassanieh, Khaled A; Moreo, Adriana; Dagotto, Elbio R

    2004-01-01

    Using exact-diagonalization techniques supplemented by a Dyson equation embedding procedure, the transport properties of multilevel quantum dots are investigated in the Kondo regime. The conductance can be decomposed into the contributions of each level. It is shown that these channels can carry a different phase, and destructive interference processes are observed when the phase difference between them is {+-}{pi}. This effect is very different from those observed in bulk metals with magnetic impurities, where the phase differences play no significant role. The effect is also different from other recent studies of interference processes in dots, as discussed in the text. In particular, no external magnetic field is introduced here, and the dot-leads hopping amplitude for all levels are the same. However, conductance cancellations induced by interactions are still observed. Another interesting effect reported here is the formation of localized states that do not participate in the transport. When one of these states crosses the Fermi level, the electronic occupation of the quantum dot changes, modifying the many-body physics of the system and indirectly affecting the transport properties. Unusual discontinuities between two finite conductance values can occur as the gate voltage is varied, as discussed here.

  6. External-field effect on quantum features of radiation emitted by a quantum well in a microcavity

    SciTech Connect

    Sete, Eyob A.; Das, Sumanta; Eleuch, H.

    2011-02-15

    We consider a semiconductor quantum well in a microcavity driven by coherent light and coupled to a squeezed vacuum reservoir. By systematically solving the pertinent quantum Langevin equations in the strong-coupling and low-excitation regimes, we study the effect of exciton-photon detuning, external coherent light, and the squeezed vacuum reservoir on vacuum Rabi splitting and on quantum statistical properties of the light emitted by the quantum well. We show that the exciton-photon detuning leads to a shift in polariton resonance frequencies and a decrease in fluorescence intensity. We also show that the fluorescent light exhibits quadrature squeezing, which predominately depends on the exciton-photon detuning and the degree of the squeezing of the input field.

  7. Scattering approach to quantum transport and many body effects

    SciTech Connect

    Pichard, Jean-Louis

    2010-12-21

    We review a series of works discussing how the scattering approach to quantum transport developed by Landauer and Buttiker for one body elastic scatterers can be extended to the case where electron-electron interactions act inside the scattering region and give rise to many body scattering. Firstly, we give an exact numerical result showing that at zero temperature a many body scatterer behaves as an effective one body scatterer, with an interaction dependent transmission. Secondly, we underline that this effective scatterer depends on the presence of external scatterers put in its vicinity. The implications of this non local scattering are illustrated studying the conductance of a quantum point contact where electrons interact with a scanning gate microscope. Thirdly, using the numerical renormalization group developed by Wilson for the Kondo problem, we study a double dot spinless model with an inter-dot interaction U and inter-dot hopping t{sub d}, coupled to leads by hopping terms t{sub c}. We show that the quantum conductance as a function of t{sub d} is given by a universal function, independently of the values of U and t{sub c}, if one measures t{sub d} in units of a characteristic scale {tau}(U,t{sub c}). Mapping the double dot system without spin onto a single dot Anderson model with spin and magnetic field, we show that {tau}(U,t{sub c}) 2T{sub K}, where T{sub K} is the Kondo temperature of the Anderson model.

  8. Quantum confinement in Si and Ge nanostructures: effect of crystallinity

    NASA Astrophysics Data System (ADS)

    Barbagiovanni, Eric G.; Lockwood, David J.; Costa Filho, Raimundo N.; Goncharova, Lyudmila V.; Simpson, Peter J.

    2013-10-01

    We look at the relationship between the preparation method of Si and Ge nanostructures (NSs) and the structural, electronic, and optical properties in terms of quantum confinement (QC). QC in NSs causes a blue shift of the gap energy with decreasing NS dimension. Directly measuring the effect of QC is complicated by additional parameters, such as stress, interface and defect states. In addition, differences in NS preparation lead to differences in the relevant parameter set. A relatively simple model of QC, using a `particle-in-a-box'-type perturbation to the effective mass theory, was applied to Si and Ge quantum wells, wires and dots across a variety of preparation methods. The choice of the model was made in order to distinguish contributions that are solely due to the effects of QC, where the only varied experimental parameter was the crystallinity. It was found that the hole becomes de-localized in the case of amorphous materials, which leads to stronger confinement effects. The origin of this result was partly attributed to differences in the effective mass between the amorphous and crystalline NS as well as between the electron and hole. Corrections to our QC model take into account a position dependent effective mass. This term includes an inverse length scale dependent on the displacement from the origin. Thus, when the deBroglie wavelength or the Bohr radius of the carriers is on the order of the dimension of the NS the carriers `feel' the confinement potential altering their effective mass. Furthermore, it was found that certain interface states (Si-O-Si) act to pin the hole state, thus reducing the oscillator strength.

  9. Robustness of quantum spin Hall effect in an external magnetic field

    NASA Astrophysics Data System (ADS)

    Zhang, Song-Bo; Zhang, Yan-Yang; Shen, Shun-Qing

    2014-09-01

    The edge states in the quantum spin Hall effect are expected to be protected by time reversal symmetry. The experimental observation of the quantized conductance was reported in the InAs/GaSb quantum well (Du et al., arXiv:1306.1925), up to a large magnetic field, which raises a question on the robustness of the edge states in the quantum spin Hall effect under time reversal symmetry breaking. Here we present a theoretical calculation on topological invariants for the Benevig-Hughes-Zhang model in an external magnetic field, and find that the quantum spin Hall effect remains robust up to a large magnetic field. The critical value of the magnetic field breaking the quantum spin Hall effect is dominantly determined by the band gap at the ? point instead of the indirect band gap between the conduction and valence bands. This illustrates that the quantum spin Hall effect could persist even under time reversal symmetry breaking.

  10. Aspects of anisotropic fractional quantum Hall effect in phosphorene

    NASA Astrophysics Data System (ADS)

    Ghazaryan, Areg; Chakraborty, Tapash

    2015-10-01

    We have analyzed the effects of the anisotropic energy bands of phosphorene on magnetoroton branches for electrons and holes in the two Landau levels close to the band edges. We have found that the fractional quantum Hall effect gap in the lowest (highest) Landau level in the conduction (valence) band is slightly larger than that for conventional semiconductor systems and therefore the effect should be experimentally observable in phosphorene. We also found that the magnetoroton mode for both electrons and holes consists of two branches with two minima due to the anisotropy. Most importantly, in the long-wavelength limit a second mode with upward dispersion, well separated from the magnetoroton mode was found to appear, that is entirely a consequence of the anisotropy in the system. These novel features of the collective mode, unique to phosphorene, can be observed in resonant inelastic light-scattering experiments.

  11. Semianalytical quantum model for graphene field-effect transistors

    SciTech Connect

    Pugnaghi, Claudio; Grassi, Roberto Gnudi, Antonio; Di Lecce, Valerio; Gnani, Elena; Reggiani, Susanna; Baccarani, Giorgio

    2014-09-21

    We develop a semianalytical model for monolayer graphene field-effect transistors in the ballistic limit. Two types of devices are considered: in the first device, the source and drain regions are doped by charge transfer with Schottky contacts, while, in the second device, the source and drain regions are doped electrostatically by a back gate. The model captures two important effects that influence the operation of both devices: (i) the finite density of states in the source and drain regions, which limits the number of states available for transport and can be responsible for negative output differential resistance effects, and (ii) quantum tunneling across the potential steps at the source-channel and drain-channel interfaces. By comparison with a self-consistent non-equilibrium Green's function solver, we show that our model provides very accurate results for both types of devices, in the bias region of quasi-saturation as well as in that of negative differential resistance.

  12. Path integral and effective Hamiltonian in loop quantum cosmology

    NASA Astrophysics Data System (ADS)

    Qin, Li; Huang, Haiyun; Ma, Yongge

    2013-06-01

    We study the path integral formulation of Friedmann universe filled with a massless scalar field in loop quantum cosmology. All the isotropic models of k=0,+1,-1 are considered. To construct the path integrals in the timeless framework, a multiple group-averaging approach is proposed. Meanwhile, since the transition amplitude in the deparameterized framework can be expressed in terms of group-averaging, the path integrals can be formulated for both deparameterized and timeless frameworks. Their relation is clarified. It turns out that the effective Hamiltonian derived from the path integral in deparameterized framework is equivalent to the effective Hamiltonian constraint derived from the path integral in timeless framework, since they lead to same equations of motion. Moreover, the effective Hamiltonian constraints of above models derived in canonical theory are confirmed by the path integral formulation.

  13. Confined monopoles induced by quantum effects in dense QCD

    SciTech Connect

    Eto, Minoru; Nitta, Muneto; Yamamoto, Naoki

    2011-04-15

    We analytically show that mesonic bound states of confined monopoles appear inside a non-Abelian vortex string in massless three-flavor QCD at large quark chemical potential {mu}. The orientational modes CP{sup 2} in the internal space of a vortex is described by the low-energy effective world-sheet theory. Mesons of confined monopoles are dynamically generated as bound states of kinks by the quantum effects in the effective theory. The mass of monopoles is shown to be an exponentially soft scale M{approx}{Delta}exp[-c({mu}/{Delta}){sup 2}], with the color superconducting gap {Delta} and some constant c. A possible quark-monopole duality between the hadron phase and the color superconducting phase is also discussed.

  14. Effective Confining Potential of Quantum States in Disordered Media.

    PubMed

    Arnold, Douglas N; David, Guy; Jerison, David; Mayboroda, Svitlana; Filoche, Marcel

    2016-02-01

    The amplitude of localized quantum states in random or disordered media may exhibit long-range exponential decay. We present here a theory that unveils the existence of an effective potential which finely governs the confinement of these states. In this picture, the boundaries of the localization subregions for low energy eigenfunctions correspond to the barriers of this effective potential, and the long-range exponential decay characteristic of Anderson localization is explained as the consequence of multiple tunneling in the dense network of barriers created by this effective potential. Finally, we show that Weyl's formula based on this potential turns out to be a remarkable approximation of the density of states for a large variety of one-dimensional systems, periodic or random. PMID:26894725

  15. Zero-recoil sum rules for ?b ??c form factors

    NASA Astrophysics Data System (ADS)

    Mannel, Thomas; van Dyk, Danny

    2015-12-01

    We set up a zero recoil sum rule to constrain the form factors of the ?b ??c transition. Our results are compared with the recent lattice calculation for these transitions. We find the same situation as in the case for B ?D*: The lattice results practically saturate the sum rules, leaving basically no room for excited states.

  16. Accurate Simulations of Pb Recoils in SuperCDMS

    NASA Astrophysics Data System (ADS)

    Redl, P.

    2014-09-01

    SuperCDMS is a direct detection search for WIMPs, currently operating a 9 kg array of germanium detectors in the Soudan Underground Laboratory. The detectors, known as iZIPs, are cylindrical in shape and each flat surface is instrumented with both ionization and phonon sensors. Charge and phonon information is collected for each event, and comparing the energy collected in the phonon sensors to the charge sensors gives excellent discrimination power between nuclear recoil and electron recoil events. Furthermore, this technology provides excellent discrimination between surface and bulk events. In order to show the surface event rejection capability of these detectors, two Pb sources were installed facing two of the detectors currently operating in the Soudan experimental run. The Pb decays to Bi, which in turn decays to Po. The Po decays by alpha emission, yielding a recoiling Pb ion with 103 keV kinetic energy and an alpha particle with 5.4 MeV kinetic energy. We used the non-standard Screened Nuclear Recoil Physics List (Mendenhall and Weller, Nucl. Instrum. Methods Phys. Res. B 227:420-430, 2005) in Geant4 (Agostinelli et al., Nucl. Instrum. Methods Phys. Res. Sect. A 506:250-303, 2003) to simulate all of the above decays and achieve excellent agreement with experiment. The focus of this paper is the simulation of the Po decay.

  17. A Candidate Recoiling Black Hole in a Nearby Dwarf Galaxy

    NASA Astrophysics Data System (ADS)

    Koss, Michael

    2014-10-01

    We have discovered a BH recoil candidate offset by 800 pc from a nearby dwarf galaxy. The object, SDSS1133, shows offset broad lines and strong variability. While originally classified as a supernova because of its non-detection in 2005, we detect it in recent and past observations over 63 years. Using high-resolution adaptive optics observations, we constrain the source emission region to be <12 pc. Overall these properties are consistent with theoretical predictions for a runaway BH ejected from its host by gravitational-wave recoil following a merger. We propose a small, 4 orbit HST observation using the COS spectrograph in the FUV, to test for broad C IV emission and other high ionization emission lines which would decisively favor the recoiling BH interpretation. The unique UV spectroscopic capability of HST is critical to decide whether this is a recoiling black hole or an unprecedented 50 year outbursting LBV star (e.g. Eta Carina) followed by a unique long duration SN IIn with rebrightening. Either discovery would be extremely exciting. Finally, SDSS1133 has recently undergone a 1.3 mag rebrightening in PanSTARRS imaging suggesting that the coming year is a critical time to observe the source at maximum.

  18. Cross-sectional nanophotoluminescence studies of Stark effects in self-assembled quantum dots

    SciTech Connect

    Htoon, H.; Keto, J. W.; Baklenov, O.; Holmes, A. L. Jr.; Shih, C. K.

    2000-02-07

    By using a cross-sectional geometry, we show the capability to perform single-dot spectroscopy in self-assembled quantum dots using far-field optics. By using this method, we study the quantum-confined Stark effect in self-assembled quantum dots. For single-stack quantum dots (QDs), we find that the spectra are redshifted with an increase in electric field. For vertically coupled double-stack quantum dots, while most of the QDs are redshifted, some QDs show blueshifted spectra, which can be interpreted as an evidence of coupled QD molecules. (c) 2000 American Institute of Physics.

  19. Generation of quantum steering and interferometric power in the dynamical Casimir effect

    NASA Astrophysics Data System (ADS)

    Sabn, Carlos; Adesso, Gerardo

    2015-10-01

    We analyze the role of the dynamical Casimir effect as a resource for quantum technologies, such as quantum cryptography and quantum metrology. In particular, we consider the generation of Einstein-Podolsky-Rosen steering and Gaussian interferometric power, two useful forms of asymmetric quantum correlations, in superconducting waveguides modulated by superconducting quantum interferometric devices. We show that while a certain value of squeezing is required to overcome thermal noise and give rise to steering, any nonzero squeezing produces interferometric power which in fact increases with thermal noise.

  20. Multipeak Kondo effect in one- and two-electron quantum dots.

    PubMed

    Vidan, A; Stopa, M; Westervelt, R M; Hanson, M; Gossard, A C

    2006-04-21

    We have fabricated a few-electron quantum dot that can be tuned down to zero electrons while maintaining strong coupling to the leads. Using a nearby quantum point contact as a charge sensor, we can determine the absolute number of electrons in the quantum dot. We find several sharp peaks in the differential conductance, occurring at both zero and finite source-drain bias, for the one- and two-electron quantum dot. We attribute the peaks at finite bias to a Kondo effect through excited states of the quantum dot and investigate the magnetic field dependence of these Kondo resonances. PMID:16712183

  1. Quantum resonance effects in exchange, photodissociation, and recombination reactions

    SciTech Connect

    Pack, R.; Kendrick, B.; Kress, J.; Walker, R.; Hayes, E.; Lagana, A.; Parker, G.; Butcher, E.

    1996-04-01

    This is the final report of a three-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). This project studied quantum resonance effects on chemical reactions. The authors accurate reactive scattering calculations showed that quantum resonance phenomena dominate most chemical reactions and are essential to any real understanding of reactivity. It was found that, as long-lived metastable states of the colliding system, resonances can decay to reactants, products, or a mixture of both. Only the latter contribute to reaction. Conditions under which resonances can be neglected or treated statistically were studied. Important implications about the mechanism of recombination reactions were discovered, and some remarkable effects of geometric phases on the symmetries and energies of resonances were also discovered. Calculations were completed for the reaction H + O{sub 2} {yields} OH + O, which is the rate limiting step in the combustion of all hydrocarbons and the single most important reaction in all of combustion chemistry.

  2. An analytical solution for quantum size effects on Seebeck coefficient

    NASA Astrophysics Data System (ADS)

    Karabetoglu, S.; Sisman, A.; Ozturk, Z. F.

    2016-03-01

    There are numerous experimental and numerical studies about quantum size effects on Seebeck coefficient. In contrast, in this study, we obtain analytical expressions for Seebeck coefficient under quantum size effects. Seebeck coefficient of a Fermi gas confined in a rectangular domain is considered. Analytical expressions, which represent the size dependency of Seebeck coefficient explicitly, are derived in terms of confinement parameters. A fundamental form of Seebeck coefficient based on infinite summations is used under relaxation time approximation. To obtain analytical results, summations are calculated using the first two terms of Poisson summation formula. It is shown that they are in good agreement with the exact results based on direct calculation of summations as long as confinement parameters are less than unity. The analytical results are also in good agreement with experimental and numerical ones in literature. Maximum relative errors of analytical expressions are less than 3% and 4% for 2D and 1D cases, respectively. Dimensional transitions of Seebeck coefficient are also examined. Furthermore, a detailed physical explanation for the oscillations in Seebeck coefficient is proposed by considering the relative standard deviation of total variance of particle number in Fermi shell.

  3. Efficient Multi-Dimensional Simulation of Quantum Confinement Effects in Advanced MOS Devices

    NASA Technical Reports Server (NTRS)

    Biegel, Bryan A.; Ancona, Mario G.; Rafferty, Conor S.; Yu, Zhiping

    2000-01-01

    We investigate the density-gradient (DG) transport model for efficient multi-dimensional simulation of quantum confinement effects in advanced MOS devices. The formulation of the DG model is described as a quantum correction ot the classical drift-diffusion model. Quantum confinement effects are shown to be significant in sub-100nm MOSFETs. In thin-oxide MOS capacitors, quantum effects may reduce gate capacitance by 25% or more. As a result, the inclusion of quantum effects may reduce gate capacitance by 25% or more. As a result, the inclusion of quantum effects in simulations dramatically improves the match between C-V simulations and measurements for oxide thickness down to 2 nm. Significant quantum corrections also occur in the I-V characteristics of short-channel (30 to 100 nm) n-MOSFETs, with current drive reduced by up to 70%. This effect is shown to result from reduced inversion charge due to quantum confinement of electrons in the channel. Also, subthreshold slope is degraded by 15 to 20 mV/decade with the inclusion of quantum effects via the density-gradient model, and short channel effects (in particular, drain-induced barrier lowering) are noticeably increased.

  4. The mechanics of elastic loading and recoil in anuran jumping.

    PubMed

    Astley, Henry C; Roberts, Thomas J

    2014-12-15

    Many animals use catapult mechanisms to produce extremely rapid movements for escape or prey capture, resulting in power outputs far beyond the limits of muscle. In these catapults, muscle contraction loads elastic structures, which then recoil to release the stored energy extremely rapidly. Many arthropods employ anatomical 'catch mechanisms' to lock the joint in place during the loading period, which can then be released to allow joint motion via elastic recoil. Jumping vertebrates lack a clear anatomical catch, yet face the same requirement to load the elastic structure prior to movement. There are several potential mechanisms to allow loading of vertebrate elastic structures, including the gravitational load of the body, a variable mechanical advantage, and moments generated by the musculature of proximal joints. To test these hypothesized mechanisms, we collected simultaneous 3D kinematics via X-ray Reconstruction of Moving Morphology (XROMM) and single-foot forces during the jumps of three Rana pipiens. We calculated joint mechanical advantage, moment and power using inverse dynamics at the ankle, knee, hip and ilio-sacral joints. We found that the increasing proximal joint moments early in the jump allowed for high ankle muscle forces and elastic pre-loading, and the subsequent reduction in these moments allowed the ankle to extend using elastic recoil. Mechanical advantage also changed throughout the jump, with the muscle contracting against a poor mechanical advantage early in the jump during loading and a higher mechanical advantage late in the jump during recoil. These 'dynamic catch mechanisms' serve to resist joint motion during elastic loading, then allow it during elastic recoil, functioning as a catch mechanism based on the balance and orientation of forces throughout the limb rather than an anatomical catch. PMID:25520385

  5. Casimir effects for classical and quantum liquids in slab geometry: A brief review

    SciTech Connect

    Biswas, Shyamal

    2015-05-15

    We analytically explore Casimir effects for confinement of classical and quantum fluctuations in slab (film) geometry (i) for classical (critical) fluctuations over {sup 4}He liquid around the λ point, and (ii) for quantum (phonon) fluctuations of Bogoliubov excitations over an interacting Bose-Einstein condensate. We also briefly review Casimir effects for confinement of quantum vacuum fluctuations confined to two plates of different geometries.

  6. Phase diagram of the two-component fractional quantum Hall effect.

    PubMed

    Archer, Alexander C; Jain, Jainendra K

    2013-06-14

    We calculate the phase diagram of the two component fractional quantum Hall effect as a function of the spin or valley Zeeman energy and the filling factor, which reveals new phase transitions and phase boundaries spanning many fractional plateaus. This phase diagram is relevant to the fractional quantum Hall effect in graphene and in GaAs and AlAs quantum wells, when either the spin or valley degree of freedom is active. PMID:25165951

  7. Exact modeling of finite temperature and quantum delocalization effects on reliability of quantum-dot cellular automata

    NASA Astrophysics Data System (ADS)

    Tiihonen, Juha; Schramm, Andreas; Kylänpää, Ilkka; Rantala, Tapio T.

    2016-02-01

    A thorough simulation study is carried out on thermal and quantum delocalization effects on the feasibility of a quantum-dot cellular automata (QCA) cell. The occupation correlation of two electrons is modeled with a simple four-site array of harmonic quantum dots (QD). QD sizes range from 20 nm to 40 nm with site separations from 20 nm to 100 nm, relevant for state-of-the-art GaAs/InAs semiconductor technology. The choice of parameters introduces QD overlap, which is only simulated properly with exact treatment of strong Coulombic correlation and thermal equilibrium quantum statistics. These are taken into account with path integral Monte Carlo approach. Thus, we demonstrate novel joint effects of quantum delocalization and decoherence in QCA, but also highly sophisticated quantitative evidence supporting the traditional relations in pragmatic QCA design. Moreover, we show the effects of dimensionality and spin state, and point out the parameter space conditions, where the ‘classical’ treatment becomes invalid.

  8. Disorder effects in the quantum Hall effect of graphene p-n junctions

    NASA Astrophysics Data System (ADS)

    Li, Jian; Shen, Shun-Qing

    2008-11-01

    The quantum Hall effect in graphene p-n junctions is studied numerically with emphasis on the effect of disorder at the interface of two adjacent regions. Conductance plateaus are found to be attached to the intensity of the disorder and are accompanied by universal conductance fluctuations in the bipolar regime, which is in good agreement with theoretical predictions of the random matrix theory on quantum chaotic cavities. The calculated Fano factors can be used in an experimental identification of the underlying transport character.

  9. Thermoelectric effects in quantum Hall systems beyond linear response

    NASA Astrophysics Data System (ADS)

    Lpez, Rosa; Hwang, Sun-Yong; Snchez, David

    2014-12-01

    We consider a quantum Hall system with an antidot acting as a energy dependent scatterer. In the purely charge case, we find deviations from the Wiedemann-Franz law that take place in the nonlinear regime of transport. We also discuss Peltier effects beyond linear response and describe both effects using magnetic-field asymmetric transport coefficients. For the spin case such as that arising along the helical edge states of a two-dimensional topological insulator, we investigate the generation of spin currents as a result of applied voltage and temperature differences in samples attached to ferromagnetic leads. We find that in the parallel configuration the spin current can be tuned with the leads' polarization even in the linear regime of transport. In contrast, for antiparallel magnetizations the spin currents has a strict nonlinear dependence on the the applied fields.

  10. Quantum Anomalous Hall Effect in Graphene-based Heterostructure

    PubMed Central

    Zhang, Jiayong; Zhao, Bao; Yao, Yugui; Yang, Zhongqin

    2015-01-01

    Quantum anomalous Hall (QAH) effect, with potential applications in low-power-consumption electronics, is predicted in the heterostructure of graphene on the (001) surface of a real antiferromagnetic insulator RbMnCl3, based on density-functional theory and Wannier function methods. Due to the interactions from the substrate, a much large exchange field (about 280?meV) and an enhanced Rashba spin-orbit coupling are induced in graphene, leading to a topologically nontrivial QAH gap opened in the system. The avenues of enhancing the nontrivial gap are also proposed, from which nearly a gap one order large is achieved. Our work demonstrates that this graphene-based heterostructure is an appropriate candidate to be employed to experimentally observe the QAH effect and explore the promising applications. PMID:26024508

  11. Nonequilibrium phonon effects in midinfrared quantum cascade lasers

    SciTech Connect

    Shi, Y. B. Knezevic, I.

    2014-09-28

    We investigate the effects of nonequilibrium phonon dynamics on the operation of a GaAs-based midinfrared quantum cascade laser over a range of temperatures (77–300 K) via a coupled ensemble Monte Carlo simulation of electron and optical-phonon systems. Nonequilibrium phonon effects are shown to be important below 200 K. At low temperatures, nonequilibrium phonons enhance injection selectivity and efficiency by drastically increasing the rate of interstage electron scattering from the lowest injector state to the next-stage upper lasing level via optical-phonon absorption. As a result, the current density and modal gain at a given field are higher and the threshold current density lower and considerably closer to experiment than results obtained with thermal phonons. By amplifying phonon absorption, nonequilibrium phonons also hinder electron energy relaxation and lead to elevated electronic temperatures.

  12. Barrier penetration effects on thermopower in semiconductor quantum wells

    SciTech Connect

    Vaidya, R. G.; Department of Physics and C.E.I.E, Tumkur University, Tumkur, Karnataka, India – 573 102 ; Sankeshwar, N. S. Mulimani, B. G.

    2014-01-15

    Finite confinement effects, due to the penetration of the electron wavefunction into the barriers of a square well potential, on the low–temperature acoustic-phonon-limited thermopower (TP) of 2DEG are investigated. The 2DEG is considered to be scattered by acoustic phonons via screened deformation potential and piezoelectric couplings. Incorporating the barrier penetration effects, the dependences of diffusion TP and phonon drag TP on barrier height are studied. An expression for phonon drag TP is obtained. Numerical calculations of temperature dependences of mobility and TP for a 10 nm InN/In {sub x}Ga{sub 1−x}N quantum well for different values of x show that the magnitude and behavior of TP are altered. A decrease in the barrier height from 500 meV by a factor of 5, enhances the mobility by 34% and reduces the TP by 58% at 20 K. Results are compared with those of infinite barrier approximation.

  13. Anisotropic charge Kondo effect in a triple quantum dot.

    PubMed

    Yoo, Gwangsu; Park, Jinhong; Lee, S-S B; Sim, H-S

    2014-12-01

    We predict that an anisotropic charge Kondo effect appears in a triple quantum dot, when the system has twofold degenerate ground states of (1,1,0) and (0,0,1) charge configurations. Using bosonization and refermionization methods, we find that at low temperature the system has the two different phases of massive charge fluctuations between the two charge configurations and vanishing fluctuations, which are equivalent with the Kondo-screened and ferromagnetic phases of the anisotropic Kondo model, respectively. The phase transition is identifiable by electron conductance measurement, offering the possibility of experimentally exploring the anisotropic Kondo model. Our charge Kondo effect has a similar origin to that in a negative-U Anderson impurity. PMID:25526143

  14. Kondo effect in coupled quantum dots under magnetic fields

    SciTech Connect

    Aono, Tomosuke; Eto, Mikio

    2001-08-15

    The Kondo effect in coupled quantum dots is investigated theoretically under magnetic fields. We show that the magnetoconductance (MC) illustrates the peak structures of Kondo resonant spectra. When the dot-dot tunneling coupling V{sub C} is smaller than the dot-lead coupling {Delta} (level broadening), Kondo resonant levels appear at the Fermi level (E{sub F}). The Zeeman splitting of the levels weakens the Kondo effect, which results in a negative MC. When V{sub C} is larger than {Delta}, the Kondo resonances form bonding and antibonding levels, located below and above E{sub F}, respectively. We observe a positive MC since the Zeeman splitting increases the overlap between the levels at E{sub F}. In the presence of antiferromagnetic spin coupling between the dots, the sign of the MC can change as a function of the gate voltage.

  15. Anisotropic Charge Kondo Effect in a Triple Quantum Dot

    NASA Astrophysics Data System (ADS)

    Yoo, Gwangsu; Park, Jinhong; Lee, S.-S. B.; Sim, H.-S.

    2014-12-01

    We predict that an anisotropic charge Kondo effect appears in a triple quantum dot, when the system has twofold degenerate ground states of (1,1,0) and (0,0,1) charge configurations. Using bosonization and refermionization methods, we find that at low temperature the system has the two different phases of massive charge fluctuations between the two charge configurations and vanishing fluctuations, which are equivalent with the Kondo-screened and ferromagnetic phases of the anisotropic Kondo model, respectively. The phase transition is identifiable by electron conductance measurement, offering the possibility of experimentally exploring the anisotropic Kondo model. Our charge Kondo effect has a similar origin to that in a negative-U Anderson impurity.

  16. Sagnac effect in a chain of mesoscopic quantum rings

    SciTech Connect

    Search, Christopher P.; Toland, John R. E.; Zivkovic, Marko

    2009-05-15

    The ability to interferometrically detect inertial rotations via the Sagnac effect has been a strong stimulus for the development of atom interferometry because of the potential 10{sup 10} enhancement of the rotational phase shift in comparison to optical Sagnac gyroscopes. Here we analyze ballistic transport of matter waves in a one-dimensional chain of N coherently coupled quantum rings in the presence of a rotation of angular frequency {omega}. We show that the transmission probability, T, exhibits zero transmission stop gaps as a function of the rotation rate interspersed with regions of rapidly oscillating finite transmission. With increasing N, the transition from zero transmission to the oscillatory regime becomes an increasingly sharp function of {omega} with a slope {partial_derivative}T/{partial_derivative}{omega}{approx}N{sup 2}. The steepness of this slope dramatically enhances the response to rotations in comparison to conventional single ring interferometers such as the Mach-Zehnder interferometer and leads to a phase sensitivity well below the quantum shot-noise limit typical of atom interferometers.

  17. Nanoscale optimization of quantum dot media for effective photovoltaic conversion

    NASA Astrophysics Data System (ADS)

    Sablon, K. A.; Sergeev, A.; Little, J. W.; Vagidov, N.; Mitin, V.

    2014-06-01

    Nanoscale engineering of band profile and potential profile provide effective tools for the management of photoelectron processes in quantum dot (QD) photovoltaic devices. We investigate the QD devices with various 1-?m InAs /GaAs QD media placed in a 3-?m base GaAs p-n junction. We found that n-charging of quantum dots (QDs) create potential barriers around QDs. QD growth between ultrathin AlGaAs layers leads to the formation of AlGaAs "fence" barriers, and reduces the wetting layers (WLs). The barriers around QDs and reduction of the wetting layer substantially suppress recombination processes via QDs. The n-doping of interdot space in QD media enhances electron extraction from QDs. All of our QD devices show short-circuit current, JSC, higher than that of the reference cell, but smaller open-circuit voltage, VOC.. In the QD devices, the short circuit currents increase by ~0.1 mA/cm2 per dot layer. JSC reaches 28.4 mA/cm2 in the device with QD media that combines dot charging, fence barriers, and WL reduction.

  18. Fractionally charged skyrmions in fractional quantum Hall effect

    DOE PAGESBeta

    Balram, Ajit C.; Wurstbauer, U.; Wójs, A.; Pinczuk, A.; Jain, J. K.

    2015-11-26

    The fractional quantum Hall effect has inspired searches for exotic emergent topological particles, such as fractionally charged excitations, composite fermions, abelian and nonabelian anyons and Majorana fermions. Fractionally charged skyrmions, which support both topological charge and topological vortex-like spin structure, have also been predicted to occur in the vicinity of 1/3 filling of the lowest Landau level. The fractional skyrmions, however, are anticipated to be exceedingly fragile, suppressed by very small Zeeman energies. Here we show that, slightly away from 1/3 filling, the smallest manifestations of the fractional skyrmion exist in the excitation spectrum for a broad range of Zeemanmore » energies, and appear in resonant inelastic light scattering experiments as well-defined resonances slightly below the long wavelength spin wave mode. The spectroscopy of these exotic bound states serves as a sensitive tool for investigating the residual interaction between composite fermions, responsible for delicate new fractional quantum Hall states in this filling factor region.« less

  19. Quantum Effects in the Diffusion of Hydrogen on Ru(0001)

    PubMed Central

    2013-01-01

    An understanding of hydrogen diffusion on metal surfaces is important not only for its role in heterogeneous catalysis and hydrogen fuel cell technology but also because it provides model systems where tunneling can be studied under well-defined conditions. Here we report helium spinecho measurements of the atomic-scale motion of hydrogen on the Ru(0001) surface between 75 and 250 K. Quantum effects are evident at temperatures as high as 200 K, while below 120 K we observe a tunneling-dominated temperature-independent jump rate of 1.9 109 s1, many orders of magnitude faster than previously seen. Quantum transition-state theory calculations based on ab initio path-integral simulations reproduce the temperature dependence of the rate at higher temperatures and predict a crossover to tunneling-dominated diffusion at low temperatures. However, the tunneling rate is underestimated, highlighting the need for future experimental and theoretical studies of hydrogen diffusion on this and other well-defined surfaces. PMID:24920996

  20. Hall effect of triplons in a dimerized quantum magnet.

    PubMed

    Romhnyi, Judit; Penc, Karlo; Ganesh, R

    2015-01-01

    SrCu2(BO3)2 is the archetypal quantum magnet with a gapped dimer-singlet ground state and triplon excitations. It serves as an excellent realization of the Shastry-Sutherland model, up to small anisotropies arising from Dzyaloshinskii-Moriya interactions. Here we demonstrate that these anisotropies, in fact, give rise to topological character in the triplon band structure. The triplons form a new kind of Dirac cone with three bands touching at a single point, a spin-1 generalization of graphene. An applied magnetic field opens band gaps resulting in topological bands with Chern numbers 2. SrCu2(BO3)2 thus provides a magnetic analogue of the integer quantum Hall effect and supports topologically protected edge modes. At a threshold value of the magnetic field set by the Dzyaloshinskii-Moriya interactions, the three triplon bands touch once again in a spin-1 Dirac cone, and lose their topological character. We predict a strong thermal Hall signature in the topological regime. PMID:25865559

  1. Electron-Fluxon Approach to the Quantum Hall Effect

    NASA Astrophysics Data System (ADS)

    Fujita, Shigeji; Morabito, David; Godoy, Salvador

    2001-04-01

    Experimental data by Willett et al.(R. Willett et al.), Phys. Rev. Lett. 59, 1776 (1987). show that the Hall resistivity ?_xy at the extreme low temperatures has plateaus at fractional occupation ratios (2D electron density / fluxon density) ? with odd denominators, where the longitudinal resistivity ?_xx (nearly) vanishes. The plateau heights are quantized in units of h/e^2. Each plateau is material- and shape-independent and indicates the stability of the superconducting state. The same data show that ?_xy is linear in B at ?=1/2, where ?_xx has a small dip, indicating a Fermi-liquid-like state with a different kind of stability. We develop a microscopic theory of the quantum Hall effect in analogy with the theory of the high temperature superconductivity, regarding the fluxon as a quantum particle with half spin and zero mass. Each Landau level, E=(N+1/2)hbar ?_0, ?_0=eB/m, has a great degeneracy. Exchange of a longitudinal phonon can generate an attractive transition between the degenerate states. The same exchange can also pair-create electron-fluxon composites, bosonic and fermionic depending on the number of fluxons. The model accounts for the energy gap at each plateau, ensuring the stability of the superconducting state.

  2. The Quantum Hall Effect in Spin Quartets in Graphene

    NASA Astrophysics Data System (ADS)

    Shrivastava, Keshav

    2008-03-01

    Using the non-relativistic Schroedinger equation, we find that for (1/2)g=(1/2)s gives zero charge for negative sign and one charge for positive sign. This explains the conductivity at i = 0 and 1. For s=3/2, (1/2)g=2 for positive sign and hence g=4. The substitution in the series, -(5/2)(g?BH), -(3/2)(g?BH), -(1/2)( g?BH), +(1/2)( g?BH),+(3/2)( g?BH), +(5/2)( g?BH), , etc., g=4 gives, -10, -6, -2, +2, +6, +10, etc. This series is the same as observed in the experimental data of quantum Hall effect in graphene. When we take n=2 in the flux quantization, i.e., 2(hc/e), we generate the plateaus at 4. Thus the plateaus can occur at 0, 1, 4 and at 2, 6, 10, 14, , etc. Thus the quantum Hall effect in graphene is understood by means of non-relativistic theory. The fractions such as 1/3 or integers such as 0,1,4,, 2,6,10,14, multiply the charge and hence describe the ``effective charge'' of the quasiparticles. This means that there is ``spin-charge locking''. *K. N. Shrivastava, Phys. Lett. A 113, 435(1986); 115, 436(E)(1986); Phys. Lett. A, 326, 469(2004); AIP Conf. Proc. 909, 43(2007);909,50(2007. *Z.Jiang, et al, Phys. Rev. Lett. 98,197403(2007);Y.Zhang et al, Phys. Rev. Lett. 96, 136806(2006).

  3. The exchange-correlation effects on surface plasmon oscillations in semi-bounded quantum plasma

    NASA Astrophysics Data System (ADS)

    Shahmansouri, Mehran

    2015-09-01

    We studied the surface plasmon waves in a quantum plasma half-space by considering the effects of exchange and correlation for the electrons. We used a quantum hydrodynamic approach, including the full set of Maxwell equations and considering two new quantities (measuring the exchange and correlation effects) in addition to the Fermi electron temperature and the quantum Bohm potential, to derive the dispersion relation for the surface plasmon waves. It was found that the exchange-correlation effects significantly modified the behavior of surface plasmon waves. We showed that the frequency of surface plasmon wave was down-shifted by the exchange-correlation effects. On the other hand, the quantum effects (including of the exchange-correlation effects and the quantum Bohm potential) was seen to cause an increase in the phase speed of surface plasmon waves. Our results can help to understand the propagation properties of surface waves in intense laser produced solid density plasmas and metallic plasmas.

  4. Quantum Gravity Effects on the Tunneling Radiation of the Einstein-Maxwell-Dilaton-Axion Black Hole

    NASA Astrophysics Data System (ADS)

    Cheng, Tianhu; Ren, Ruyi; Chen, Deyou; Liu, Zixiang; Li, Guopin

    2016-03-01

    Taking into account effects of quantum gravity, we investigate the evaporation of an Einstein-Maxwell-Dilaton-Axion black hole. The corrected Hawking temperature is gotten respectively by the scalar particle's and the fermion's tunneling across the horizon. This temperature is lower than the original one derived by Hawking, which means quantum gravity effects slow down the rise of the temperature.

  5. Spin effects on the instability and propagation modes of electrostatic plasma waves in quantum plasmas

    SciTech Connect

    Ki, Dae-Han; Jung, Young-Dae

    2011-09-19

    The effects of the electron spin interaction on the pure instability and propagation modes of the quantum electrostatic waves are investigated in cold quantum electron plasmas. It is found that the influence of the electron spin interaction increases the group velocity of the propagation mode of the quantum electrostatic wave. In addition, it is shown that the electron spin interaction enhances the growth rate of the instability mode of the quantum electrostatic wave. It is also found that the effects of the electron spin interaction would be more important in the domain of small Fermi wave numbers.

  6. Decoherence Effect on Quantum Correlation and Entanglement in a Two-qubit Spin Chain

    NASA Astrophysics Data System (ADS)

    Pourkarimi, Mohammad Reza; Rahnama, Majid; Rooholamini, Hossein

    2015-04-01

    Assuming a two-qubit system in Werner state which evolves in Heisenberg XY model with Dzyaloshinskii-Moriya (DM) interaction under the effect of different environments. We evaluate and compare quantum entanglement, quantum and classical correlation measures. It is shown that in the absence of decoherence effects, there is a critical value of DM interaction for which entanglement may vanish while quantum and classical correlations do not. In the presence of environment the behavior of correlations depends on the kind of system-environment interaction. Correlations can be sustained by manipulating Hamiltonian anisotropic-parameter in a dissipative environment. Quantum and classical correlations are more stable than entanglement generally.

  7. Quantum entanglement formation by repeated spin blockade measurements in a spin field-effect transistor structure embedded with quantum dots

    NASA Astrophysics Data System (ADS)

    Yoh, Kanji; Yuasa, Kazuya; Nakazato, Hiromichi

    2005-11-01

    We propose a method of operating a quantum state machine made of stacked quantum dots buried in adjacent to the channel of a spin field-effect transistor (FET) [S. Datta, B. Das, Appl. Phys. Lett. 56 (1990) 665; K. Yoh, et al., Proceedings of the 23rd International Conference on Physics of Semiconductors (ICPS) 2004; H. Ohno, K. Yoh et al., Jpn. J. Appl. Phys. 42 (2003) L87; K. Yoh, J. Konda, S. Shiina, N. Nishiguchi, Jpn. J. Appl. Phys. 36 (1997) 4134]. In this method, a spin blockade measurement extracts the quantum state of a nearest quantum dot through Coulomb blockade [K. Yoh, J. Konda, S. Shiina, N. Nishiguchi, Jpn. J. Appl. Phys. 36 (1997) 4134; K. Yoh, H. Kazama, Physica E 7 (2000) 440] of the adjacent channel conductance. Repeated quantum Zeno-like (QZ) measurements [H. Nakazato, et al., Phys. Rev. Lett. 90 (2003) 060401] of the spin blockade is shown to purify the quantum dot states within several repetitions. The growth constraints of the stacked InAs quantum dots are shown to provide an exchange interaction energy in the range of 0.01-1 meV [S. Itoh, et al., Jpn. J. Appl. Phys. 38 (1999) L917; A. Tackeuchi, et al., Jpn. J. Appl. Phys. 42 (2003) 4278]. We have verified that one can reach the fidelity of 90% by repeating the measurement twice, and that of 99.9% by repeating only eleven QZ measurements. Entangled states with two and three vertically stacked dots are achieved with the sampling frequency of the order of 100 MHz.

  8. Scaling theory of the integer quantum Hall effect

    SciTech Connect

    Huckestein, B.

    1995-04-01

    The scaling theory of the transitions between plateaus of the Hall conductivity in the integer quantum Hall effect is reviewed. In the model of two-dimensional noninteracting electrons in strong magnetic fields, the transitions are disorder-induced localization-delocalization transitions. While experimental and analytical approaches are surveyed, the emphasis is on numerical studies, which successfully describe the experiments. The theoretical models for disordered systems are described in detail. An overview of the finite-size scaling theory and its relation to Anderson localiztion is given. The field-theoretical approach to the localization problem is outlined. Numerical methods for the calculation of scaling quantities, in particular the localization length, are detailed. The properties of local observables at the localization-delocalization transition are discussed in terms of multifractal measures. Finally, the results of extensive numerical investigations are compared with experimental findings.

  9. Symmetry criteria for quantum simulability of effective interactions

    NASA Astrophysics Data System (ADS)

    Zimbors, Zoltn; Zeier, Robert; Schulte-Herbrggen, Thomas; Burgarth, Daniel

    2015-10-01

    What can one do with a given tunable quantum device? We provide complete symmetry criteria deciding whether some effective target interaction(s) can be simulated by a set of given interactions. Symmetries lead to a better understanding of simulation and permit a reasoning beyond the limitations of the usual explicit Lie closure. Conserved quantities induced by symmetries pave the way to a resource theory for simulability. On a general level, one can now decide equality for any pair of compact Lie algebras just given by their generators without determining the algebras explicitly. Several physical examples are illustrated, including entanglement invariants, the relation to unitary gate membership problems, as well as the central-spin model.

  10. Fractional quantum Hall effect in a dilute magnetic semiconductor

    NASA Astrophysics Data System (ADS)

    Betthausen, C.; Giudici, P.; Iankilevitch, A.; Preis, C.; Kolkovsky, V.; Wiater, M.; Karczewski, G.; Piot, B. A.; Kunc, J.; Potemski, M.; Wojtowicz, T.; Weiss, D.

    2014-09-01

    We report the observation of the fractional quantum Hall effect in the lowest Landau level of a two-dimensional electron system (2DES), residing in the diluted magnetic semiconductor Cd1-xMnxTe. The presence of magnetic impurities results in a giant Zeeman splitting leading to an unusual ordering of composite fermion Landau levels. In experiment, this results in an unconventional opening and closing of fractional gaps around the filling factor ? =3/2 as a function of an in-plane magnetic field, i.e., of the Zeeman energy. By including the s-d exchange energy into the composite Landau level spectrum the opening and closing of the gap at filling factor 5/3 can be modeled quantitatively. The widely tunable spin-splitting in a diluted magnetic 2DES provides a means to manipulate fractional states.

  11. Topological insulator in junction with ferromagnets: Quantum Hall effects

    NASA Astrophysics Data System (ADS)

    Chudnovskiy, A. L.; Kagalovsky, V.

    2015-06-01

    The ferromagnet-topological insulator-ferromagnet (FM-TI-FM) junction exhibits thermal and electrical quantum Hall effects. The generated Hall voltage and transverse temperature gradient can be controlled by the directions of magnetizations in the FM leads, which inspires the use of FM-TI-FM junctions as electrical and as heat switches in spintronic devices. Thermal and electrical Hall coefficients are calculated as functions of the magnetization directions in ferromagnets and the spin-relaxation time in TI. Both the Hall voltage and the transverse temperature gradient decrease but are not completely suppressed even at very short spin-relaxation times. The Hall coefficients turn out to be independent of the spin-relaxation time for symmetric configuration of FM leads.

  12. Searching for the fractional quantum Hall effect in graphite.

    PubMed

    Kopelevich, Y; Raquet, B; Goiran, M; Escoffier, W; da Silva, R R; Pantoja, J C Medina; Luk'yanchuk, I A; Sinchenko, A; Monceau, P

    2009-09-11

    Measurements of basal plane longitudinal rho(b)(B) and Hall rho(H)(B) resistivities were performed on highly oriented pyrolytic graphite samples in a pulsed magnetic field up to B=50 T applied perpendicular to graphene planes, and temperatures 1.5 K30 T and for all studied samples, we observed a sign change in rho(H)(B) from electron- to holelike. For our best quality sample, the measurements revealed the enhancement in rho(b)(B) for B>34 T (T=1.8 K), presumably associated with the field-driven charge density wave or Wigner crystallization transition. In addition, well-defined plateaus in rho(H)(B) were detected in the ultraquantum limit revealing possible signatures of the fractional quantum Hall effect in graphite. PMID:19792390

  13. Ferromagnetic Kondo effect in a triple quantum dot system.

    PubMed

    Baruselli, P P; Requist, R; Fabrizio, M; Tosatti, E

    2013-07-26

    A simple device of three laterally coupled quantum dots, the central one contacted by metal leads, provides a realization of the ferromagnetic Kondo model, which is characterized by interesting properties like a nonanalytic inverted zero-bias anomaly and an extreme sensitivity to a magnetic field. Tuning the gate voltages of the lateral dots allows us to study the transition from a ferromagnetic to antiferromagnetic Kondo effect, a simple case of a Berezinskii-Kosterlitz-Thouless transition. We model the device by three coupled Anderson impurities that we study by numerical renormalization group. We calculate the single-particle spectral function of the central dot, which at zero frequency is proportional to the zero-bias conductance, across the transition, both in the absence and in the presence of a magnetic field. PMID:23931401

  14. Orbital Kondo effect in fractional quantum Hall systems

    NASA Astrophysics Data System (ADS)

    Komijani, Yashar; Simon, Pascal; Affleck, Ian

    2015-08-01

    We study the transport properties of a charge qubit coupling two chiral Luttinger liquids, realized by two antidots placed between the edges of an integer ? =1 or fractional ? =1 /3 quantum Hall bar. We show that in the limit of a large capacitive coupling between the antidots, their quasiparticle occupancy behaves as a pseudospin corresponding to an orbital Kondo impurity coupled to a chiral Luttinger liquid, while the interantidot tunneling acts as an impurity magnetic field. The latter tends to destabilize the Kondo fixed point for the ? =1 /3 fractional Hall state, producing an effective interedge tunneling. We relate the interedge conductance to the susceptibility of the Kondo impurity and calculate it analytically in various limits for both ? =1 and ? =1 /3 .

  15. Magnetic quantum coherence effect in Ni4 molecular transistors.

    TOXLINE Toxicology Bibliographic Information

    Gonzlez G; Leuenberger MN

    2014-07-09

    We present a theoretical study of electron transport in Ni4 molecular transistors in the presence of Zeeman spin splitting and magnetic quantum coherence (MQC). The Zeeman interaction is extended along the leads which produces gaps in the energy spectrum which allow electron transport with spin polarized along a certain direction. We show that the coherent states in resonance with the spin up or down states in the leads induces an effective coupling between localized spin states and continuum spin states in the single molecule magnet and leads, respectively. We investigate the conductance at zero temperature as a function of the applied bias and magnetic field by means of the Landauer formula, and show that the MQC is responsible for the appearence of resonances. Accordingly, we name them MQC resonances.

  16. Magnetic quantum coherence effect in Ni4 molecular transistors

    NASA Astrophysics Data System (ADS)

    Gonzlez, Gabriel; Leuenberger, Michael N.

    2014-07-01

    We present a theoretical study of electron transport in Ni4 molecular transistors in the presence of Zeeman spin splitting and magnetic quantum coherence (MQC). The Zeeman interaction is extended along the leads which produces gaps in the energy spectrum which allow electron transport with spin polarized along a certain direction. We show that the coherent states in resonance with the spin up or down states in the leads induces an effective coupling between localized spin states and continuum spin states in the single molecule magnet and leads, respectively. We investigate the conductance at zero temperature as a function of the applied bias and magnetic field by means of the Landauer formula, and show that the MQC is responsible for the appearence of resonances. Accordingly, we name them MQC resonances.

  17. Magnetic quantum coherence effect in Ni4 molecular transistors.

    PubMed

    Gonzlez, Gabriel; Leuenberger, Michael N

    2014-07-01

    We present a theoretical study of electron transport in Ni4 molecular transistors in the presence of Zeeman spin splitting and magnetic quantum coherence (MQC). The Zeeman interaction is extended along the leads which produces gaps in the energy spectrum which allow electron transport with spin polarized along a certain direction. We show that the coherent states in resonance with the spin up or down states in the leads induces an effective coupling between localized spin states and continuum spin states in the single molecule magnet and leads, respectively. We investigate the conductance at zero temperature as a function of the applied bias and magnetic field by means of the Landauer formula, and show that the MQC is responsible for the appearence of resonances. Accordingly, we name them MQC resonances. PMID:24918902

  18. The origins of cosmic rays and quantum effects on gravity

    NASA Technical Reports Server (NTRS)

    Tomozawa, Y.

    1985-01-01

    The energy spectrum of primary cosmic rays is explained by particles emitted during a thermal expansion of explosive objects inside and near the galaxy, remnants of which may be supernova and/or active talaxies, or even stars or galaxies that disappeared from our sight after the explosion. A power law energy spectrum for cosmic rays, E to the (-alpha -1, is obtained from an expansion rate T is proportional to R to the alpha. Using the solution of the Einstein equation, we obtain a spectrum which agrees very well with experimental data. The implication of an inflationary early universe on the cosmic ray spectrum is also discussed. It is also suggested that the conflict between this model and the singularity theorem in classical general relativity may be eliminated by quantum effects.

  19. Casimir effect between Topological Insulators: a proposal for quantum levitation

    NASA Astrophysics Data System (ADS)

    Rodriguez-Lopez, Pablo; Grushin, Adolfo; Cortijo, Alberto

    2013-03-01

    In this talk I will study the Casimir interaction between Topological Insulators (TIs). I will start with a brief description of the TIs, to explain what a TI is, and why they are interesting from a Casimir effect point of view. In particular, a three dimensional Topological Insulator is characterized by its topological magnetoelectric coupling ? ? 0. We will discuss the electromagnetic response of the TIs, how a magnetoelectric coupling between TE and TM modes appears in this material and its consequences. We will show how, by tuning the parameter ? of the TI, we will be able to change the behavior of the Casimir energy between Tis from attraction to repulsion for all distances, and even the appearance of an equilibrium distance in the system. Then TIs can be potentially used to obtain ``quantum levitation'' and to avoid the sticking phenomena in NEMS.

  20. Thermoelectric effects in molecular quantum dots with contacts

    NASA Astrophysics Data System (ADS)

    Koch, T.; Loos, J.; Fehske, H.

    2014-04-01

    We consider the steady-state thermoelectric transport through a vibrating molecular quantum dot that is contacted to macroscopic leads. For moderate electron-phonon interaction strength and comparable electronic and phononic timescales, we investigate the impact of the formation of a local polaron on the thermoelectric properties of the junction. We apply a variational Lang-Firsov transformation and solve the equations of motion in the Kadanoff-Baym formalism up to second order in the dot-lead coupling parameter. We calculate the thermoelectric current and voltage for finite temperature differences in the resonant and inelastic tunneling regimes. For a near resonant dot level, the formation of a local polaron can boost the thermoelectric effect because of the Franck-Condon blockade. The line shape of the thermoelectric voltage signal becomes asymmetrical due to the varying polaronic character of the dot state and in the nonlinear transport regime, vibrational signatures arise.

  1. Localizationlike effect in two-dimensional alternate quantum walks with periodic coin operations

    NASA Astrophysics Data System (ADS)

    Di Franco, Carlo; Paternostro, Mauro

    2015-01-01

    Exploiting multidimensional quantum walks as feasible platforms for quantum computation and quantum simulation attracts constantly growing attention from a broad experimental physics community. Here, we propose a two-dimensional quantum walk scheme with a single-qubit coin that presents, in the considered regimes, a strong localizationlike effect on the walker. The result could provide new possible directions for the implementation of quantum algorithms or from the point of view of quantum simulation. We characterize the localizationlike effect in terms of the parameters of a step-dependent qubit operation that acts on the coin space after any standard coin operation, showing that a proper choice can guarantee a nonnegligible probability of finding the walker in the origin even for large times. We finally discuss the robustness to imperfections, a qualitative relation with coherences behavior, and possible experimental realizations of this model with the current state-of-the-art settings.

  2. Warm target recoil ion momentum spectroscopy for fragmentation of molecular hydrogen by ultrashort laser pulses.

    PubMed

    Liu, Jia; Wu, Jian; Czasch, Achim; Zeng, Heping

    2009-07-20

    We demonstrate warm target recoil ion momentum spectroscopy for the fragmentation dynamics of the warm hydrogen molecules at room temperature. The thermal movement effect of the warm molecule is removed by using a correction algorithm in the momentum space. Based on the reconstructed three-dimensional momentum vectors as well as the kinetic energy release spectra, different vibrational states of the H(2)(+) ground state are clearly visible and the internuclear separation for charge resonance enhanced ionization of the second electron is identified. The results show adequate accordance with the former experiments using other techniques. PMID:19654636

  3. Recoil polarization measurements of the proton electromagnetic form factor ratio at high momentum transfer

    SciTech Connect

    Andrew Puckett

    2009-12-01

    Electromagnetic form factors are fundamental properties of the nucleon that describe the effect of its internal quark structure on the cross section and spin observables in elastic lepton-nucleon scattering. Double-polarization experiments have become the preferred technique to measure the proton and neutron electric form factors at high momentum transfers. The recently completed GEp-III experiment at the Thomas Jefferson National Accelerator Facility used the recoil polarization method to extend the knowledge of the proton electromagnetic form factor ratio GpE/GpM to Q2 = 8.5 GeV2. In this paper we present the preliminary results of the experiment.

  4. Efficient Multi-Dimensional Simulation of Quantum Confinement Effects in Advanced MOS Devices

    NASA Technical Reports Server (NTRS)

    Biegel, Bryan A.; Rafferty, Conor S.; Ancona, Mario G.; Yu, Zhi-Ping

    2000-01-01

    We investigate the density-gradient (DG) transport model for efficient multi-dimensional simulation of quantum confinement effects in advanced MOS devices. The formulation of the DG model is described as a quantum correction to the classical drift-diffusion model. Quantum confinement effects are shown to be significant in sub-100nm MOSFETs. In thin-oxide MOS capacitors, quantum effects may reduce gate capacitance by 25% or more. As a result, the inclusion or quantum effects in simulations dramatically improves the match between C-V simulations and measurements for oxide thickness down to 2 nm. Significant quantum corrections also occur in the I-V characteristics of short-channel (30 to 100 nm) n-MOSFETs, with current drive reduced by up to 70%. This effect is shown to result from reduced inversion charge due to quantum confinement of electrons in the channel. Also, subthreshold slope is degraded by 15 to 20 mV/decade with the inclusion of quantum effects via the density-gradient model, and short channel effects (in particular, drain-induced barrier lowering) are noticeably increased.

  5. Radiation Effects in Nanostructures: Comparison of Proton Irradiation Induced Changes on Quantum Dots and Quantum Wells

    NASA Technical Reports Server (NTRS)

    Leon, R.; Swift, G.; Magness, B.; Taylor, W.; Tang, Y.; Wang, K.; Dowd, P.; Zhang, Y.

    2000-01-01

    Successful implementation of technology using self-forming semiconductor Quantum Dots (QDs) has already demonstrated that temperature independent Dirac-delta density of states can be exploited in low current threshold QD lasers and QD infrared photodetectors.

  6. Localized States and Quantum Spin Hall Effect in Si-Doped InAs/GaSb Quantum Wells

    NASA Astrophysics Data System (ADS)

    Xu, Dong-Hui; Gao, Jin-Hua; Liu, Chao-Xing; Sun, Jin-Hua; Zhang, Fu-Chun; Zhou, Yi

    2014-03-01

    We study localized in-gap states and quantum spin Hall effect in Si-doped InAs/GaSb quantum wells. We propose a model describing donor and/or acceptor impurities to describe Si dopants. This model shows in-gap bound states and wide conductance plateau with the quantized value 2e2 / h in light dopant concentration, consistent with recent experiments by Du et al.[arXiv: 1306.1925] We predict a conductance dip structure due to backward scattering in the region where the localization length ? is comparable with the sample width Ly but much smaller than the sample length Lx.

  7. Quantum confinement and strain effects on the lateral mode stability of an unstable resonator semiconductor laser

    SciTech Connect

    Ru, P. ); Chow, W.W. ); Moloney, J.V. ); Koch, S.W. )

    1994-03-21

    The gain medium effects on the lateral mode stability of an unstable resonator semiconductor laser are investigated. A physical optics laser model based on a many-body semiclassical laser theory of the gain medium is used. The consistent treatment of bulk, quantum well, and strained quantum well structures shows that quantum confinement or strain can result in single lateral mode operation over significantly wider ranges of unstable resonator configurations and gain medium excitation.

  8. Anomalous quantum reflection as a quasidynamical damping effect

    SciTech Connect

    Jurisch, Alexander; Rost, Jan-Michael

    2010-04-15

    We develop a quasianalytical theory for the quantum reflection amplitude of Bose-Einstein condensates. We derive and calculate the decay width of a Bose-Einstein condensate (BEC). A general relation between the time-dependent decay law of the system and its quantum reflection amplitude allows us to explain the quantum reflection anomaly of Bose-Einstein condensates present in BEC-surface systems as a direct consequence of the repulsive particle interaction.

  9. Non-abelian fractional quantum hall effect for fault-resistant topological quantum computation.

    SciTech Connect

    Pan, Wei; Thalakulam, Madhu; Shi, Xiaoyan; Crawford, Matthew; Nielsen, Erik; Cederberg, Jeffrey George

    2013-10-01

    Topological quantum computation (TQC) has emerged as one of the most promising approaches to quantum computation. Under this approach, the topological properties of a non-Abelian quantum system, which are insensitive to local perturbations, are utilized to process and transport quantum information. The encoded information can be protected and rendered immune from nearly all environmental decoherence processes without additional error-correction. It is believed that the low energy excitations of the so-called =5/2 fractional quantum Hall (FQH) state may obey non-Abelian statistics. Our goal is to explore this novel FQH state and to understand and create a scientific foundation of this quantum matter state for the emerging TQC technology. We present in this report the results from a coherent study that focused on obtaining a knowledge base of the physics that underpins TQC. We first present the results of bulk transport properties, including the nature of disorder on the 5/2 state and spin transitions in the second Landau level. We then describe the development and application of edge tunneling techniques to quantify and understand the quasiparticle physics of the 5/2 state.

  10. Non-Markovian dynamics of correlations: The composite effect of two channels and robust quantum correlation preserving by detuning

    NASA Astrophysics Data System (ADS)

    Ji, Y. H.; Wan, X. D.

    2015-10-01

    We investigate the influence of the composite effect and information backflow effect in non-Markovian channel on the dynamics of quantum correlation including quantum entanglement and quantum discord. It is found that, the composite effect of independent channels is not only harmful to the maintenance of quantum correlation but also unfavorable for the maintenance of classic correlation. In a non-Markovian channel, by regulating the discord between qubit and the center frequency of cavity model, the time of quantum correlation and classical correlation of the system can be effectively prolonged. Thus, the quantum information processing can be achieved more easily under larger detuning.

  11. The new vacuum-mode recoil separator MARA at JYFL

    NASA Astrophysics Data System (ADS)

    Sarn, J.; Uusitalo, J.; Leino, M.; Greenlees, P. T.; Jakobsson, U.; Jones, P.; Julin, R.; Juutinen, S.; Ketelhut, S.; Nyman, M.; Peura, P.; Rahkila, P.; Scholey, C.; Sorri, J.

    2008-10-01

    A new vacuum-mode recoil separator MARA (Mass Analysing Recoil Apparatus) is under design and construction at the Department of Physics in the University of Jyvskyl. The separator is intended to separate reaction products from the primary beam in mass region below A = 150 . The ion-optical configuration of the separator will be QQQDEDM, where a magnetic quadrupole (Q) triplet is followed by an electrostatic deflector (DE) and a magnetic dipole (DM). The total length of MARA will be less than 7.0 m and the first order resolving power more than 250 for a beam spot size of 2 mm. In this contribution the main properties of MARA are given and results from simulations are shown.

  12. Time-of-flight direct recoil ion scattering spectrometer

    DOEpatents

    Krauss, Alan R.; Gruen, Dieter M.; Lamich, George J.

    1994-01-01

    A time of flight direct recoil and ion scattering spectrometer beam line (10). The beam line (10) includes an ion source (12) which injects ions into pulse deflection regions (14) and (16) separated by a drift space (18). A final optics stage includes an ion lens and deflection plate assembly (22). The ion pulse length and pulse interval are determined by computerized adjustment of the timing between the voltage pulses applied to the pulsed deflection regions (14) and (16).

  13. Time-of-flight direct recoil ion scattering spectrometer

    DOEpatents

    Krauss, A.R.; Gruen, D.M.; Lamich, G.J.

    1994-09-13

    A time-of-flight direct recoil and ion scattering spectrometer beam line is disclosed. The beam line includes an ion source which injects ions into pulse deflection regions and separated by a drift space. A final optics stage includes an ion lens and deflection plate assembly. The ion pulse length and pulse interval are determined by computerized adjustment of the timing between the voltage pulses applied to the pulsed deflection regions. 23 figs.

  14. Recoiling supermassive black holes: a search in the nearby universe

    SciTech Connect

    Lena, D.; Robinson, A.; Axon, D. J.; Merritt, D.; Marconi, A.; Capetti, A.; Batcheldor, D.

    2014-11-10

    The coalescence of a binary black hole can be accompanied by a large gravitational recoil due to anisotropic emission of gravitational waves. A recoiling supermassive black hole (SBH) can subsequently undergo long-lived oscillations in the potential well of its host galaxy, suggesting that offset SBHs may be common in the cores of massive ellipticals. We have analyzed Hubble Space Telescope archival images of 14 nearby core ellipticals, finding evidence for small (≲ 10 pc) displacements between the active galactic nucleus (AGN; the location of the SBH) and the center of the galaxy (the mean photocenter) in 10 of them. Excluding objects that may be affected by large-scale isophotal asymmetries, we consider six galaxies to have detected displacements, including M87, where a displacement was previously reported by Batcheldor et al. In individual objects, these displacements can be attributed to residual gravitational recoil oscillations following a major or minor merger within the last few gigayears. For plausible merger rates, however, there is a high probability of larger displacements than those observed, if SBH coalescence took place in these galaxies. Remarkably, the AGN-photocenter displacements are approximately aligned with the radio source axis in four of the six galaxies with displacements, including three of the four having relatively powerful kiloparsec-scale jets. This suggests intrinsic asymmetries in radio jet power as a possible displacement mechanism, although approximate alignments are also expected for gravitational recoil. Orbital motion in SBH binaries and interactions with massive perturbers can produce the observed displacement amplitudes but do not offer a ready explanation for the alignments.

  15. Magnetic Topological Insulators and Quantum Anomalous Hall Effect

    NASA Astrophysics Data System (ADS)

    Kou, Xufeng

    The engineering of topological surface states is a key to realize applicable devices based on topological insulators (TIs). Among various proposals, introducing magnetic impurities into TIs has been proven to be an effective way to open a surface gap and integrate additional ferromagnetism with the original topological order. In this Dissertation, we study both the intrinsic electrical and magnetic properties of the magnetic TI thin films grown by molecular beam epitaxy. By doping transition element Cr into the host tetradymite-type V-VI semiconductors, we achieve robust ferromagnetic order with a strong perpendicular magnetic anisotropy. With additional top-gating capability, we realize the electric-field-controlled ferromagnetism in the magnetic TI systems, and demonstrate such magneto-electric effects can be effectively manipulated, depending on the interplays between the band topology, magnetic exchange coupling, and structural engineering. Most significantly, we report the observation of quantum anomalous Hall effect (QAHE) in the Cr-doped (BiSb)2Te3 samples where dissipationless chiral edge conduction is realized in the macroscopic millimeter-size devices without the presence of any external magnetic field, and the stability of the quantized Hall conductance of e2/h is well-maintained as the film thickness varies across the 2D hybridization limit. With additional quantum confinement, we discover the metal-to-insulator switching between two opposite QAHE states, and reveal the universal QAHE phase diagram in the thin magnetic TI samples. In addition to the uniform magnetic TIs, we further investigate the TI/Cr-doped TI bilayer structures prepared by the modulation-doped growth method. By controlling the magnetic interaction profile, we observe the Dirac hole-mediated ferromagnetism and develop an effective way to manipulate its strength. Besides, the giant spin-orbit torque in such magnetic TI-based heterostructures enables us to demonstrate the current-induced magnetization switching with the critical current density much lower than other heavy metal/magnet systems. Our work on the magnetic TIs and their heterostructures thus unfolds new avenues for novel multifunctional nano-electronics and non-volatile spintronic applications.

  16. The recoil proton polarization in. pi. p elastic scattering

    SciTech Connect

    Seftor, C.J.

    1988-09-01

    The polarization of the recoil proton for ..pi../sup +/p and ..pi../sup -/p elastic scattering has been measured for various angles at 547 MeV/c and 625 MeV/c by a collaboration involving The George Washington University; the University of California, Los Angeles; and Abilene Christian University. The experiment was performed at the P/sup 3/ East experimental area of the Los Alamos Meson Physics Facility. Beam intensities varied from 0.4 to 1.0 x 10/sup 7/ ..pi../sup -/'s/sec and from 3.0 to 10.0 x 10/sup 7/ ..pi../sup +/'s/sec. The beam spot size at the target was 1 cm in the horizontal direction by 2.5 cm in the vertical direction. A liquid-hydrogen target was used in a flask 5.7 cm in diameter and 10 cm high. The scattered pion and recoil proton were detected in coincidence using the Large Acceptance Spectrometer (LAS) to detect and momentum analyze the pions and the JANUS recoil proton polarimeter to detect and measure the polarization of the protons. Results from this experiment are compared with previous measurements of the polarization, with analyzing power data previously taken by this group, and to partial-wave analysis predictions. 12 refs., 53 figs., 18 tabs.

  17. The velocity and recoil of DNA bands during gel electrophoresis

    NASA Astrophysics Data System (ADS)

    Keiner, Louis E.; Holzwarth, G.

    1992-09-01

    The velocity and recoil of bands of DNA containing 48.5 to 4800 kilobasepairs (kb) were measured during pulsed-field gel electrophoresis by a video imaging and analysis system. When a 10 V/cm electric field was first applied, the velocity showed an initial sharp peak after approximately 1 s whose amplitude depended on the molecular weight of the DNA and the rest time and polarity of the previous pulse. For example, G DNA (670 kb) exhibited an initial velocity peak of 13 μm/s. The velocity then oscillated through a shallow minimum and small maximum before reaching a 5.0 μm/s plateau. After the field was turned off, the bands moved backward (recoiled). The band position obeyed a stretched-exponential relation, x = x0 exp[ - (t/τ)β] with amplitude x0 equal to approximately 1/10th of the DNA contour length and β≊0.6; for S. pombe DNA, x0 was a remarkable 165 μm. Both the initial velocity spike and the recoil arise from the presence of a significant fraction of U-shaped molecules with low configurational entropy. The initial velocity spike is exploited in field-inversion gel electrophoresis to generate the ``antiresonance,'' which is the basis of size-dependent mobility. Recent computer simulations which include tube-length fluctuations and tube leakage are in excellent accord with the measured velocities.

  18. Recoil Experiments Using a Compressed Air Cannon

    ERIC Educational Resources Information Center

    Taylor, Brett

    2006-01-01

    Ping-Pong vacuum cannons, potato guns, and compressed air cannons are popular and dramatic demonstrations for lecture and lab. Students enjoy them for the spectacle, but they can also be used effectively to teach physics. Recently we have used a student-built compressed air cannon as a laboratory activity to investigate impulse, conservation of

  19. Quantum Computer Games: Quantum Minesweeper

    ERIC Educational Resources Information Center

    Gordon, Michal; Gordon, Goren

    2010-01-01

    The computer game of quantum minesweeper is introduced as a quantum extension of the well-known classical minesweeper. Its main objective is to teach the unique concepts of quantum mechanics in a fun way. Quantum minesweeper demonstrates the effects of superposition, entanglement and their non-local characteristics. While in the classical

  20. Quantum Computer Games: Quantum Minesweeper

    ERIC Educational Resources Information Center

    Gordon, Michal; Gordon, Goren

    2010-01-01

    The computer game of quantum minesweeper is introduced as a quantum extension of the well-known classical minesweeper. Its main objective is to teach the unique concepts of quantum mechanics in a fun way. Quantum minesweeper demonstrates the effects of superposition, entanglement and their non-local characteristics. While in the classical…

  1. Kondo effect in a topological insulator quantum dot

    NASA Astrophysics Data System (ADS)

    Xin, Xianhao; Zhou, Di

    2015-04-01

    We investigate theoretically the nonequilibrium transport properties of a topological insulator quantum dot (TIQD) in the Coulomb blockade and Kondo regime. An Anderson impurity model is applied to a TIQD system coupled to two external leads, and we show that the model realizes the spin-orbital Kondo effect at the Dirac point where the edge states are not split by a finite-size effect, leading to an additional S U (4 ) symmetry because of the presence of strong mixture among four internal degrees of freedom. In a more realistic situation where the degeneracy is lifted due to the finite-size effect, we demonstrate that there is a richer structure in transport measurements. We illustrate a continuous crossover from four (spin and orbital) Coulomb peaks with large interpair spacing and small intrapair spacing to a double-peak structure in the local density of states (LDOS) as increasing the hybridization strength ? within the Coulomb blockade regime. When temperature falls below the Kondo temperature TK, four Kondo peaks show up in the nonequilibrium LDOS. Two of them are located at the chemical potential of each lead, and the other two are shifted away from the chemical potential by an amount proportional to the TIQD's bare energy level, leading to a triple-peak structure in the differential conductance when a bias voltage is applied.

  2. Recoil Polarization Measurements of the Proton Electromagnetic Form Factor Ratio to High Momentum Transfer

    SciTech Connect

    Andrew Puckett

    2010-02-01

    The electromagnetic form factors of the nucleon characterize the effect of its internal structure on its response to an electromagnetic probe as studied in elastic electronnucleon scattering. These form factors are functions of the squared four-momentum transfer Q2 between the electron and the proton. The two main classes of observables of this reaction are the scattering cross section and polarization asymmetries, both of which are sensitive to the form factors in different ways. When considering large f momentum transfers, double-polarization observables offer superior sensitivity to the electric form factor. This thesis reports the results of a new measurement of the ratio of the electric and magnetic form factors of the proton at high momentum transfer using the recoil polarization technique. A polarized electron beam was scattered from a liquid hydrogen target, transferring polarization to the recoiling protons. These protons were detected in a magnetic spectrometer which was used to reconstruct their kinematics, including their scattering angles and momenta, and the position of the interaction vertex. A proton polarimeter measured the polarization of the recoiling protons by measuring the azimuthal asymmetry in the angular distribution of protons scattered in CH2 analyzers. The scattered electron was detected in a large acceptance electromagnetic calorimeter in order to suppress inelastic backgrounds. The measured ratio of the transverse and longitudinal polarization components of the scattered proton is directly proportional to the ratio of form factors GpE=GpM. The measurements reported in this thesis took place at Q2 =5.2, 6.7, and 8.5 GeV2, and represent the most accurate measurements of GpE in this Q2 region to date.

  3. Quantum random walks on congested lattices and the effect of dephasing

    PubMed Central

    Motes, Keith R.; Gilchrist, Alexei; Rohde, Peter P.

    2016-01-01

    We consider quantum random walks on congested lattices and contrast them to classical random walks. Congestion is modelled on lattices that contain static defects which reverse the walker’s direction. We implement a dephasing process after each step which allows us to smoothly interpolate between classical and quantum random walks as well as study the effect of dephasing on the quantum walk. Our key results show that a quantum walker escapes a finite boundary dramatically faster than a classical walker and that this advantage remains in the presence of heavily congested lattices. PMID:26812924

  4. Quantum random walks on congested lattices and the effect of dephasing.

    PubMed

    Motes, Keith R; Gilchrist, Alexei; Rohde, Peter P

    2016-01-01

    We consider quantum random walks on congested lattices and contrast them to classical random walks. Congestion is modelled on lattices that contain static defects which reverse the walker's direction. We implement a dephasing process after each step which allows us to smoothly interpolate between classical and quantum random walks as well as study the effect of dephasing on the quantum walk. Our key results show that a quantum walker escapes a finite boundary dramatically faster than a classical walker and that this advantage remains in the presence of heavily congested lattices. PMID:26812924

  5. Geometric phases and quantum correlations of superconducting two-qubit system with dissipative effect

    NASA Astrophysics Data System (ADS)

    Xue, Liyuan; Yu, Yanxia; Cai, Xiaoya; Pan, Hui; Wang, Zisheng

    2016-01-01

    We investigate time-dependent Pancharatnam phases and the relations between such geometric phases and quantum correlations, i.e., quantum discord and concurrence, of superconducting two-qubit coupling system in dissipative environment with the mixture effects of four different eigenstates of density matrix. We find that the time-dependent Pancharatnam phases not only keep the motion memory of such a two-qubit system, but also include the information of quantum correlations. We show that the sudden died and alive phenomena of quantum entanglement are intrinsic in the transition of Pancharatnam phase in the X-state and the complex oscillations of Pancharatnam phase in the Y-state. The faster the Pancharatnam phases change, the slower the quantum correlations decay. In particular, we find that a subspace of quantum entanglement can exist in the Y-state by choosing suitable coupling parameters between two-qubit system and its environment, or initial conditions.

  6. Classical limit of the quantum Zeno effect by environmental decoherence

    NASA Astrophysics Data System (ADS)

    Bedingham, D.; Halliwell, J. J.

    2014-04-01

    We consider a point particle in one dimension initially confined to a finite spatial region whose state is frequently monitored by projection operators onto that region. In the limit of infinitely frequent monitoring, the state never escapes from the regionthis is the Zeno effect. In the corresponding classical problem, by contrast, the state diffuses out of the region with the frequent monitoring simply removing probability. The aim of this paper is to show how the Zeno effect disappears in the classical limit in this and similar examples. We give a general argument showing that the Zeno effect is suppressed in the presence of a decoherence mechanism which suppresses interference between histories. We show how this works explicitly in two examples involving projections onto a one-dimensional subspace and identify the key time scales for the process. We extend this understanding to our main problem of interest, the case of a particle in a spatial region, by coupling it to a decohering environment. Smoothed projectors are required to give the problem proper definition and this implies the existence of a momentum cutoff and minimum length scale. We show that the escape rate from the region approaches the classically expected result, and hence the Zeno effect is suppressed, as long as the environmentally induced fluctuations in momentum are sufficiently large. We establish the time scale on which an arbitrary initial state develops sufficiently large fluctuations to satisfy this condition. We link our results to earlier work on the ? ?0 limit of the Zeno effect. We illustrate our results by plotting the probability flux lines for the density matrix (which are equivalent to Bohm trajectories in the pure-state case). These illustrate both the Zeno and anti-Zeno effects very clearly, and their suppression. Our results are closely related to our earlier paper [Phys. Rev. A 88, 022128 (2013), 10.1103/PhysRevA.88.022128], demonstrating the suppression of quantum-mechanical reflection by decoherence.

  7. Calendar effects in quantum mechanics in view of interactive holography

    NASA Astrophysics Data System (ADS)

    Berkovich, Simon

    2013-04-01

    Quantum mechanics in terms of interactive holography appears as `normal' science [1]. With the holography quantum behavior is determined by the interplay of material formations and their conjugate images. To begin with, this effortlessly elucidates the nonlocality in quantum entanglements. Then, it has been shown that Schr"odinger's dynamics for a single particle arises from Bi-Fragmental random walks of the particle itself and its holographic image. For many particles this picture blurs with fragments merging as bosons or fermions. In biomolecules, swapping of particles and their holographic placeholders leads to self-replication of the living matter. Because of broad interpretations of quantum formalism direct experiments attributing it to holography may not be very compelling. The holographic mechanism better reveals as an absolute frame of reference. A number of physical and biological events exhibit annual variations when Earth orbital position changes with respect to the universal holographic mechanism. The well established calendar variations of heart attacks can be regarded as a positive outcome of a generalization of the Michelson experiment, where holography is interferometry and ailing hearts are detectors of pathologically replicated proteins. Also, there have been already observed calendar changes in radioactive decay rates. The same could be expected for various fine quantum experiences, like, e.g., Josephson tunneling. In other words, Quantum Mechanics (February) Quantum Mechanics (August). [1] S. Berkovich, ``A comprehensive explanation of quantum mechanics,'' www.cs.gwu.edu/research/technical-report/170 .

  8. Elementary framework for cold field emission: Incorporation of quantum-confinement effects

    SciTech Connect

    Patterson, A. A. Akinwande, A. I.

    2013-12-21

    Although the Fowler-Nordheim (FN) equation serves as the foundation of cold field emission theory, it may not be suitable for predicting the emitted current density (ECD) from emitters with a quantum-confined electron supply. This work presents an analytical framework for treating cold field emission from metals that includes the effects of a quantum-confined electron supply. Within the framework, quantum confinement in emitters is classified into transverse and normal quantum confinement based on the orientation of the confinement relative to the emission direction. The framework is used to generate equations predicting the ECD from rectangular and cylindrical emitter geometries comprised of electron supplies of reduced dimensionality. Transverse quantum confinement of the electron supply leads to a reduction in the total ECD as transverse emitter dimensions decrease and normal quantum confinement results in an oscillatory ECD as a function of the normal quantum well width. Incorporating a geometry-dependent field enhancement factor into the model reveals an optimal transverse well width for which quantum confinement of the electron supply and field enhancement equally affect the ECD and a maximum total ECD for the emitter geometry at a given applied field is obtained. As a result, the FN equation over-predicts the ECD from emitters with transverse dimensions under approximately 5 nm, and in those cases, geometry-specific ECD equations incorporating quantum-confinement effects should be employed instead.

  9. Motion and gravity effects in the precision of quantum clocks

    PubMed Central

    Lindkvist, Joel; Sabín, Carlos; Johansson, Göran; Fuentes, Ivette

    2015-01-01

    We show that motion and gravity affect the precision of quantum clocks. We consider a localised quantum field as a fundamental model of a quantum clock moving in spacetime and show that its state is modified due to changes in acceleration. By computing the quantum Fisher information we determine how relativistic motion modifies the ultimate bound in the precision of the measurement of time. While in the absence of motion the squeezed vacuum is the ideal state for time estimation, we find that it is highly sensitive to the motion-induced degradation of the quantum Fisher information. We show that coherent states are generally more resilient to this degradation and that in the case of very low initial number of photons, the optimal precision can be even increased by motion. These results can be tested with current technology by using superconducting resonators with tunable boundary conditions. PMID:25988238

  10. Motion and gravity effects in the precision of quantum clocks.

    PubMed

    Lindkvist, Joel; Sabín, Carlos; Johansson, Göran; Fuentes, Ivette

    2015-01-01

    We show that motion and gravity affect the precision of quantum clocks. We consider a localised quantum field as a fundamental model of a quantum clock moving in spacetime and show that its state is modified due to changes in acceleration. By computing the quantum Fisher information we determine how relativistic motion modifies the ultimate bound in the precision of the measurement of time. While in the absence of motion the squeezed vacuum is the ideal state for time estimation, we find that it is highly sensitive to the motion-induced degradation of the quantum Fisher information. We show that coherent states are generally more resilient to this degradation and that in the case of very low initial number of photons, the optimal precision can be even increased by motion. These results can be tested with current technology by using superconducting resonators with tunable boundary conditions. PMID:25988238

  11. Quantum fluctuations and isotope effects in ab initio descriptions of water

    SciTech Connect

    Wang, Lu; Markland, Thomas E.; Ceriotti, Michele

    2014-09-14

    Isotope substitution is extensively used to investigate the microscopic behavior of hydrogen bonded systems such as liquid water. The changes in structure and stability of these systems upon isotope substitution arise entirely from the quantum mechanical nature of the nuclei. Here, we provide a fully ab initio determination of the isotope exchange free energy and fractionation ratio of hydrogen and deuterium in water treating exactly nuclear quantum effects and explicitly modeling the quantum nature of the electrons. This allows us to assess how quantum effects in water manifest as isotope effects, and unravel how the interplay between electronic exchange and correlation and nuclear quantum fluctuations determine the structure of the hydrogen bond in water.

  12. Observation of Resonant Quantum Magnetoelectric Effect in a Multiferroic Metal-Organic Framework.

    PubMed

    Tian, Ying; Shen, Shipeng; Cong, Junzhuang; Yan, Liqin; Wang, Shouguo; Sun, Young

    2016-01-27

    A resonant quantum magnetoelectric coupling effect has been demonstrated in the multiferroic metal-organic framework of [(CH3)2NH2]Fe(HCOO)3. This material shows a coexistence of a spin-canted antiferromagnetic order and ferroelectricity as well as clear magnetoelectric coupling below TN ≈ 19 K. In addition, a component of single-ion quantum magnets develops below ∼8 K because of an intrinsic magnetic phase separation. The stair-shaped magnetic hysteresis loop at 2 K signals resonant quantum tunneling of magnetization. Meanwhile, the magnetic field dependence of dielectric permittivity exhibits sharp peaks just at the critical tunneling fields, evidencing the occurrence of resonant quantum magnetoelectric coupling effect. This resonant effect enables a simple electrical detection of quantum tunneling of magnetization. PMID:26743039

  13. Fractional quantum Hall effect on the two-sphere: A matrix model proposal

    SciTech Connect

    Morariu, Bogdan; Polychronakos, Alexios P.

    2005-12-15

    We present a Chern-Simons matrix model describing the fractional quantum Hall effect on the two sphere. We demonstrate the equivalence of our proposal to particular restrictions of the Calogero-Sutherland model, reproduce the quantum states and filling fraction and show the compatibility of our result with the Haldane spherical wave functions.

  14. Acceleration of positrons by a relativistic electron beam in the presence of quantum effects

    SciTech Connect

    Niknam, A. R.; Aki, H.; Khorashadizadeh, S. M.

    2013-09-15

    Using the quantum magnetohydrodynamic model and obtaining the dispersion relation of the Cherenkov and cyclotron waves, the acceleration of positrons by a relativistic electron beam is investigated. The Cherenkov and cyclotron acceleration mechanisms of positrons are compared together. It is shown that growth rate and, therefore, the acceleration of positrons can be increased in the presence of quantum effects.

  15. Quantum-electrodynamics corrections in pionic hydrogen

    SciTech Connect

    Schlesser, S.; Le Bigot, E.-O.; Indelicato, P.; Pachucki, K.

    2011-07-15

    We investigate all pure quantum-electrodynamics corrections to the np{yields}1s, n=2-4 transition energies of pionic hydrogen larger than 1 meV, which requires an accurate evaluation of all relevant contributions up to order {alpha}{sup 5}. These values are needed to extract an accurate strong interaction shift from experiment. Many small effects, such as second-order and double vacuum polarization contribution, proton and pion self-energies, finite size and recoil effects are included with exact mass dependence. Our final value differs from previous calculations by up to {approx_equal}11 ppm for the 1s state, while a recent experiment aims at a 4 ppm accuracy.

  16. The effect of quantum confinement on tunneling field-effect transistors with high-? gate dielectric

    NASA Astrophysics Data System (ADS)

    Padilla, J. L.; Gmiz, F.; Godoy, A.

    2013-09-01

    In this letter, we study the impact of quantum confinement in double gate tunneling field-effect transistors with different body thicknesses in the presence of high-? gate dielectrics. Although better ON currents have been reported for these devices coming out from semiclassical simulations, the inclusion of quantum effects makes the formerly continuous conduction and valence bands become a discrete set of energy subbands, thus, increasing the effective bandgap, and consequently, reducing the current levels. If the high-? dielectric layer covers both the source and the drain, the band energy structure at the tunneling junction is modified (tunneling widths are increased), hence resulting in performance degradation. An optimal configuration seeking to improve ON currents would require low permittivity dielectrics over S/D regions along with high-? materials under the gates.

  17. Temperature effects and transport phenomena in terahertz quantum cascade lasers

    NASA Astrophysics Data System (ADS)

    Slingerland, Philip C.

    Quantum cascade lasers (QCL's) employ the mid- and far-infrared intersubband radiative transitions available in semiconductor heterostructures. Through the precise design and construction of these heterostructures the laser characteristics and output frequencies can be controlled. When fabricated, QCL's offer a lightweight and portable alternative to traditional laser systems which emit in this frequency range. The successful operation of these devices strongly depends on the effects of electron transport. Studies have been conducted on the mechanisms involved in electron transport and a computational model has been completed for QCL performance prediction and design optimization. The implemented approach utilized a three period model of the laser active region with periodic boundary conditions enforced. All of the wavefunctions within these periods were included in a self-consistent rate equation model. This model employed all relevant types of scattering mechanisms within three periods. Additionally, an energy balance equation was studied to determine the set of individual subband electron temperatures. This equation included the influence of both electron-LO phonon and electron-electron scattering. The effect of different modeling parameters within QCL electron temperature predictions are presented along with a description of the complete QCL computational model and comparisons with experimental results.

  18. Effective dynamics in Bianchi type II loop quantum cosmology

    NASA Astrophysics Data System (ADS)

    Corichi, Alejandro; Montoya, Edison

    2012-05-01

    We numerically investigate the solutions to the effective equations of the Bianchi II model within the improved loop quantum cosmology dynamics. The matter source is a massless scalar field. We perform a systematic study of the space of solutions, and focus on the behavior of several geometrical observables. We show that the big bang singularity is replaced by a bounce and the pointlike singularities do not saturate the energy density bound. There are up to three directional bounces in the scale factors, one global bounce in the expansion, the shear presents up to four local maxima and can be zero at the bounce. This allows for solutions with density larger than the maximal density for the isotropic and Bianchi I cases. The asymptotic behavior is shown to behave like that of a Bianchi I model, and the effective solutions connect anisotropic solutions even when the shear is zero at the bounce. All known facts of Bianchi I are reproduced. In the vacuum limit, solutions are such that almost all the dynamics is due to the anisotropies. Since Bianchi II plays an important role in the Bianchi IX model and the Belinskii, Khalatnikov, Lifshitz conjecture, our results can provide an intuitive understanding of the behavior in the vicinity of general spacelike singularities, when loop-geometric corrections are present.

  19. Tuning The Properties of Quantum Dots Via The Effective Mass

    NASA Astrophysics Data System (ADS)

    Singh, R. A.; Sinha, Abhinav; Pathak, Praveen

    2011-07-01

    In the present work we revisit effective mass theory (EMT) for a semiconductor quantum dot (QD) and employ the BenDaniel-Duke (BDD) boundary condition. In effective mass theory mass mi inside the dot of radius R is different from the mass mo outside the dot. That gives us a crucial factor in determining the electronic spectrum namely ? = mi/m0. We show both by numerical calculations and asymptotic analysis that the ground state energy and the surface charge density, ?(r) can be large. We also show that the dependence of the ground state energy on the radius of the well is infraquadratic. We demonstrate that the significance of BDD condition is pronounced at large R. We also study the dependence of excited state on the radius as well as the difference between energy states. Both exhibit an infra quadratic behavior with radius. The energy difference is important in study of absorption and emission spectra. We find that the BDD condition substantially alters the energy difference. Hence the interpretation of experimental result may need to be reexamined.

  20. Astrometric detection of gravitational effects of quantum vacuum

    NASA Astrophysics Data System (ADS)

    Vecchiato, Alberto; Gai, Mario; Hajdukovic, Dragan

    2015-08-01

    In a series of recent papers it was suggested that the pairs of virtual particles-antiparticles composing the Quantum Vacuum (QV) can behave like gravitational dipoles with both attractive and repulsive interaction. If verified, this hypothesis would give raise to a series of gravitational effects at different scale length not yet considered in current gravity theories, and it may support galactic and cosmological models alternative to those involving Dark Matter and Dark Energy.Within the boundaries of the Solar System, the most promising targets for testing the gravitational QV conjecture are the binary trans-neptunian objects (TNOs). The gravitational action of the QV, in fact, would manifest itself as an external force inducing an anomalous precession, i.e. an excess shift of the longitude of the pericenter in the orbit of the TNO satellite which, e.g., for the UX25 candidate and under reasonable working hypothesis, was estimated to be about 0.23 arcsec per orbit.In this work we analyze in some detail the feasibility of testing the gravitational QV hypothesis estimating the above effect with ground-based and spaceborne astrometric observations. Several observing scenarios are explored here, including those using conventional and adaptive optics telescopes from ground, some spaceborne telescopes, and by exploring a list of possible candidates.

  1. Many-Body Effects in Quantum-Well Intersubband Transitions

    NASA Technical Reports Server (NTRS)

    Li, Jian-Zhong; Ning, Cun-Zheng

    2003-01-01

    Intersubband polarization couples to collective excitations of the interacting electron gas confined in a semiconductor quantum well (Qw) structure. Such excitations include correlated pair excitations (repellons) and intersubband plasmons (ISPs). The oscillator strength of intersubband transitions (ISBTs) strongly varies with QW parameters and electron density because of this coupling. We have developed a set of kinetic equations, termed the intersubband semiconductor Bloch equations (ISBEs), from density matrix theory with the Hartree-Fock approximation, that enables a consistent description of these many-body effects. Using the ISBEs for a two-conduction-subband model, various many-body effects in intersubband transitions are studied in this work. We find interesting spectral changes of intersubband absorption coefficient due to interplay of the Fermi-edge singularity, subband renormalization, intersubband plasmon oscillation, and nonparabolicity of bandstructure. Our results uncover a new perspective for ISBTs and indicate the necessity of proper many-body theoretical treatment in order for modeling and prediction of ISBT line shape.

  2. Tuning The Properties of Quantum Dots Via The Effective Mass

    SciTech Connect

    Singh, R. A.; Sinha, Abhinav; Pathak, Praveen

    2011-07-15

    In the present work we revisit effective mass theory (EMT) for a semiconductor quantum dot (QD) and employ the BenDaniel-Duke (BDD) boundary condition. In effective mass theory mass m{sub i} inside the dot of radius R is different from the mass m{sub o} outside the dot. That gives us a crucial factor in determining the electronic spectrum namely {beta} = m{sub i}/m{sub 0}. We show both by numerical calculations and asymptotic analysis that the ground state energy and the surface charge density, {rho}(r) can be large. We also show that the dependence of the ground state energy on the radius of the well is infraquadratic. We demonstrate that the significance of BDD condition is pronounced at large R. We also study the dependence of excited state on the radius as well as the difference between energy states. Both exhibit an infra quadratic behavior with radius. The energy difference is important in study of absorption and emission spectra. We find that the BDD condition substantially alters the energy difference. Hence the interpretation of experimental result may need to be reexamined.

  3. Orbital Kondo effect in a parallel double quantum dot.

    PubMed

    Bao, Zhi-qiang; Guo, Ai-Min; Sun, Qing-feng

    2014-10-29

    We construct a theoretical model to study the orbital Kondo effect in a parallel double quantum dot (DQD). Recently, pseudospin-resolved transport spectroscopy of the orbital Kondo effect in a DQD has been experimentally reported. The experiment revealed that when interdot tunneling is ignored, two and one Kondo peaks exist in the conductance-bias curve for pseudospin-non-resolved and pseudospin-resolved cases, respectively. Our theoretical studies reproduce this experimental result. We also investigate the case of all lead voltages being non-equal (the complete pseudospin-resolved case) and found that there are at most four Kondo peaks in the curve of the conductance versus the pseudospin splitting energy. When interdot tunneling is introduced, some new Kondo peaks and dips can emerge. Furthermore, the pseudospin transport and the pseudospin flipping current are also studied in the DQD system. Since the pseudospin transport is much easier to control and measure than the real spin transport, it can be used to study the physical phenomenon related to the spin transport. PMID:25299453

  4. Orbital Kondo effect in a parallel double quantum dot

    NASA Astrophysics Data System (ADS)

    Bao, Zhi-qiang; Guo, Ai-Min; Sun, Qing-feng

    2014-10-01

    We construct a theoretical model to study the orbital Kondo effect in a parallel double quantum dot (DQD). Recently, pseudospin-resolved transport spectroscopy of the orbital Kondo effect in a DQD has been experimentally reported. The experiment revealed that when interdot tunneling is ignored, two and one Kondo peaks exist in the conductance-bias curve for pseudospin-non-resolved and pseudospin-resolved cases, respectively. Our theoretical studies reproduce this experimental result. We also investigate the case of all lead voltages being non-equal (the complete pseudospin-resolved case) and found that there are at most four Kondo peaks in the curve of the conductance versus the pseudospin splitting energy. When interdot tunneling is introduced, some new Kondo peaks and dips can emerge. Furthermore, the pseudospin transport and the pseudospin flipping current are also studied in the DQD system. Since the pseudospin transport is much easier to control and measure than the real spin transport, it can be used to study the physical phenomenon related to the spin transport.

  5. Induced spin-accumulation and spin-polarization in a quantum-dot ring by using magnetic quantum dots and Rashba spin-orbit effect

    SciTech Connect

    Eslami, L. Faizabadi, E.

    2014-05-28

    The effect of magnetic contacts on spin-dependent electron transport and spin-accumulation in a quantum ring, which is threaded by a magnetic flux, is studied. The quantum ring is made up of four quantum dots, where two of them possess magnetic structure and other ones are subjected to the Rashba spin-orbit coupling. The magnetic quantum dots, referred to as magnetic quantum contacts, are connected to two external leads. Two different configurations of magnetic moments of the quantum contacts are considered; the parallel and the anti-parallel ones. When the magnetic moments are parallel, the degeneracy between the transmission coefficients of spin-up and spin-down electrons is lifted and the system can be adjusted to operate as a spin-filter. In addition, the accumulation of spin-up and spin-down electrons in non-magnetic quantum dots are different in the case of parallel magnetic moments. When the intra-dot Coulomb interaction is taken into account, we find that the electron interactions participate in separation between the accumulations of electrons with different spin directions in non-magnetic quantum dots. Furthermore, the spin-accumulation in non-magnetic quantum dots can be tuned in the both parallel and anti-parallel magnetic moments by adjusting the Rashba spin-orbit strength and the magnetic flux. Thus, the quantum ring with magnetic quantum contacts could be utilized to create tunable local magnetic moments which can be used in designing optimized nanodevices.

  6. Quantum Anomalous Hall Effect in Hetero Magnetic Topological Insulator Structures

    NASA Astrophysics Data System (ADS)

    Wang, Kang

    2014-03-01

    The quantum anomalous Hall effect (QAHE), which has the quantized Hall conductance of h /e2 in the absence of external field, was expected to happen in a magnetic 3-D topological insulators (TIs) system. In this talk, we report recent progress of QAHE-related physics in the TRS-breaking field. In the first part, we show the generation of robust magnetism by doping magnetic ions (Cr) into the host (BixSb1-x)2 Te3 materials. With gate-controlled magneto-transport measurements, we demonstrate the presence of both the hole-mediated RKKY coupling and carrier-independent van Vleck magnetism. By adjusting the Cr doping concentration and Bi/Sb ratio, we establish an effective way to experimentally approach to the QAHE region. The second part of this talk discusses the manipulation of surface-related magnetism in the modulation-doped TI/Cr-doped TI heterostructures. We investigate the role of massive surface Dirac fermions in the bulk RKKY mediation process. Both our theoretical models and experimental results reveal that the topological surface-related magnetic order can be either enhanced or suppressed, depending on the magnetic interaction range between the surface states and Cr ions. Based on such TI heterostructures, we also demonstrate the magnetization switching via giant spin-orbit torque induced by the in-plane current. Finally, in order to make these effects observable at 300K, we describe the use of magnetic proximity effects to manipulate the surface magnetism of TI. These results not only demonstrate additional important steps to further explore fundamental properties of the TRS-breaking TI systems but also may help the realization of many functionalities of TI-based spintronics applications. The work was in part supported by DARPA under N66001-12-1-40 and N66001-11-1-4105.

  7. Therapeutic Effects of Oligonol, Acupuncture, and Quantum Light Therapy in Chronic Nonbacterial Prostatitis

    PubMed Central

    Öztekin, İlhan; Akdere, Hakan; Can, Nuray; Aktoz, Tevfik; Turan, Fatma Nesrin

    2015-01-01

    This research aimed to compare anti-inflammatory effects of oligonol, acupuncture, and quantum light therapy in rat models of estrogen-induced prostatitis. Adult male Wistar albino rats were grouped as follows: Group I, control (n = 10); Group II, chronic prostatitis (n = 10); Group III, oligonol (n = 10); Group IV, acupuncture (n = 10); Group V, quantum (n = 10); Group VI, oligonol plus quantum (n = 10); Group VII, acupuncture plus oligonol (n = 10); Group VIII, quantum plus acupuncture (n = 10); and Group IX, acupuncture plus quantum plus oligonol (n = 10). Chronic prostatitis (CP) was induced by the administration of 17-beta-estradiol (E2) and dihydrotestosterone (DHT). Oligonol was given for 6 weeks at a dose of 60 mg/day. Acupuncture needles were inserted at CV 3/4 and bilaterally B 32/35 points with 1-hour manual stimulation. Quantum therapy was administered in 5-minute sessions three times weekly for 6 weeks. Lateral lobes of prostates were dissected for histopathologic evaluation. Although all of the treatment modalities tested in this study showed anti-inflammatory effects in the treatment of CP in male rats, a synergistic effect was observed for oligonol plus quantum light combination. Monotherapy with oligonol showed a superior anti-inflammatory efficacy as compared to quantum light and acupuncture monotherapies. PMID:26064171

  8. Noise characteristics of the Fano effect and the Fano-Kondo effect in triple quantum dots.

    PubMed

    Tanamoto, T; Nishi, Y; Fujita, S

    2009-04-01

    We theoretically compare transport properties of the Fano-Kondo effect with those of the Fano effect, focusing on the effect of a two-level state in a triple quantum dot (QD) system. We analyze shot noise characteristics in the Fano-Kondo region at zero temperature, and discuss the effect of strong electronic correlation in QDs. We found that the modulation of the Fano dip is strongly affected by the on-site Coulomb interaction in QDs, and stronger Coulomb interaction (Fano-Kondo case) induces larger noise. PMID:21825341

  9. Projecting the Kondo effect: theory of the quantum mirage.

    PubMed

    Agam, O; Schiller, A

    2001-01-15

    A microscopic theory is developed for the projection (quantum mirage) of the Kondo resonance from one focus of an elliptic quantum corral to the other focus. The quantum mirage is shown to be independent of the size and the shape of the ellipse, and experiences lambdaF/4 oscillations ( lambdaF is the surface-band Fermi wavelength) with an increasing semimajor axis length. We predict an oscillatory behavior of the mirage as a function of a weak magnetic field applied perpendicular to the sample. PMID:11177861

  10. Fidelity Susceptibility Perspective on the Kondo Effect and Impurity Quantum Phase Transitions

    NASA Astrophysics Data System (ADS)

    Wang, Lei; Shinaoka, Hiroshi; Troyer, Matthias

    2015-12-01

    The Kondo effect is a ubiquitous phenomenon appearing at low temperature in quantum confined systems coupled to a continuous bath. Efforts in understanding and controlling it have triggered important developments across several disciplines of condensed matter physics. A recurring pattern in these studies is that the suppression of the Kondo effect often results in intriguing physical phenomena such as impurity quantum phase transitions or non-Fermi-liquid behavior. We show that the fidelity susceptibility is a sensitive indicator for such phenomena because it quantifies the sensitivity of the system's state with respect to its coupling to the bath. We demonstrate the power of the fidelity susceptibility approach by using it to identify the crossover and quantum phase transitions in the one and two impurity Anderson models. The feasibility of measuring fidelity susceptibility in condensed matter as well as ultracold quantum gases experiments opens exciting new routes to diagnose the Kondo problem and impurity quantum phase transitions.

  11. Fidelity Susceptibility Perspective on the Kondo Effect and Impurity Quantum Phase Transitions.

    PubMed

    Wang, Lei; Shinaoka, Hiroshi; Troyer, Matthias

    2015-12-01

    The Kondo effect is a ubiquitous phenomenon appearing at low temperature in quantum confined systems coupled to a continuous bath. Efforts in understanding and controlling it have triggered important developments across several disciplines of condensed matter physics. A recurring pattern in these studies is that the suppression of the Kondo effect often results in intriguing physical phenomena such as impurity quantum phase transitions or non-Fermi-liquid behavior. We show that the fidelity susceptibility is a sensitive indicator for such phenomena because it quantifies the sensitivity of the system's state with respect to its coupling to the bath. We demonstrate the power of the fidelity susceptibility approach by using it to identify the crossover and quantum phase transitions in the one and two impurity Anderson models. The feasibility of measuring fidelity susceptibility in condensed matter as well as ultracold quantum gases experiments opens exciting new routes to diagnose the Kondo problem and impurity quantum phase transitions. PMID:26684131

  12. Direct detection of classically undetectable dark matter through quantum decoherence

    NASA Astrophysics Data System (ADS)

    Riedel, C. Jess

    2013-12-01

    Although various pieces of indirect evidence about the nature of dark matter have been collected, its direct detection has eluded experimental searches despite extensive effort. If the mass of dark matter is below 1 MeV, it is essentially imperceptible to conventional detection methods because negligible energy is transferred to nuclei during collisions. Here I propose directly detecting dark matter through the quantum decoherence it causes rather than its classical effects, such as recoil or ionization. I show that quantum spatial superpositions are sensitive to low-mass dark matter that is inaccessible to classical techniques. This provides new independent motivation for matter interferometry with large masses, especially on spaceborne platforms. The apparent dark matter wind we experience as the Sun travels through the Milky Way ensures interferometers and related devices are directional detectors, and so are able to provide unmistakable evidence that decoherence has Galactic origins.

  13. Quantum site percolation on triangular lattice and the integer quantum Hall effect

    NASA Astrophysics Data System (ADS)

    Mkhitaryan, V. V.; Raikh, M. E.

    2009-03-01

    Generic classical electron motion in a strong perpendicular magnetic field and random potential reduces to the bond percolation on a square lattice. Here we point out that for certain smooth two-dimensional potentials with 120° rotational symmetry this problem reduces to the site percolation on a triangular lattice. We use this observation to develop an approximate analytical description of the integer quantum Hall transition. For this purpose we devise a quantum generalization of the real-space renormalization group (RG) treatment of the site percolation on the triangular lattice. In quantum case, the RG transformation describes the evolution of the distribution of the 3×3 scattering matrices at the sites. We find the fixed point of this distribution and use it to determine the critical exponent, ν , for which we find the value ν≈2.3÷2.76 . The RG step involves only a single Hikami box and thus can serve as a minimal RG description of the quantum Hall transition.

  14. Quantum Hall effect and insulating state near the charge neutrality point in an InAs/GaSb quantum well

    NASA Astrophysics Data System (ADS)

    Pal, Atindra Nath; Nichele, Fabrizio; Pietsch, Patrick; Ihn, Thomas; Ensslin, Klaus; Charpentier, Christophe; Wegscheider, Werner

    2014-03-01

    We present transport measurements in a gated InAs/GaSb double quantum well (QW) sandwiched between two AlSb barriers. In this system a QW for electrons in InAs and a QW for holes in GaSb coexist next to each other and a hybridization gap is expected to occur. We can tune the transport from electrons to the holes by applying a top gate voltage. In presence of a perpendicular magnetic field, we observe well defined quantum Hall plateaus in both sides. Interestingly, at the charge neutrality point a strong increase in the longitudinal resistivity is observed with increasing perpendicular magnetic field, accompanied by the onset of a non-local resistance of similar magnitude. The co-existence of these two effects is described by a model of counter-propagating and dissipative quantum Hall edge channels, shorted by a residual bulk conductivity. The authors wish to thank Swiss National Science Foundation for financial support via NCCR QSIT (Quantum Science and Technology).

  15. Measurement of Recoil Losses and Ranges for Spallation Products Produced in Proton Interactions with Al, Si, Mg at 200 and 500 MeV

    NASA Technical Reports Server (NTRS)

    Sisterson, J. M.

    2005-01-01

    Cosmic rays interact with extraterrestrial materials to produce a variety of spallation products. If these cosmogenic nuclides are produced within an inclusion in such material, then an important consideration is the loss of the product nuclei, which recoil out of the inclusion. Of course, at the same time, some atoms of the product nuclei under study may be knocked into the inclusion from the surrounding material, which is likely to have a different composition to that of the inclusion [1]. For example, Ne-21 would be produced in presolar grains, such as SiC, when irradiated in interstellar space. However, to calculate a presolar age, one needs to know how much 21Ne is retained in the grain. For small grains, the recoil losses might be large [2, 3] To study this effect under laboratory conditions, recoil measurements were made using protons with energies from 66 - 1600 MeV on Si, Al and Ba targets [3, 4, 5].

  16. The quantum Hall effect at 5/2 filling factor

    NASA Astrophysics Data System (ADS)

    Willett, R. L.

    2013-07-01

    Experimental discovery of a quantized Hall state at 5/2 filling factor presented an enigmatic finding in an established field of study that has remained an open issue for more than twenty years. In this review we first examine the experimental requirements for observing this state and outline the initial theoretical implications and predictions. We will then follow the chronology of experimental studies over the years and present the theoretical developments as they pertain to experiments, directed at sets of issues. These topics will include theoretical and experimental examination of the spin properties at 5/2; is the state spin polarized? What properties of the higher Landau levels promote development of the 5/2 state, what other correlation effects are observed there, and what are their interactions with the 5/2 state? The 5/2 state is not a robust example of the fractional quantum Hall effect: what experimental and material developments have allowed enhancement of the effect? Theoretical developments from initial pictures have promoted the possibility that 5/2 excitations are exceptional; do they obey non-abelian statistics? The proposed experiments to determine this and their executions in various forms will be presented: this is the heart of this review. Experimental examination of the 5/2 excitations through interference measurements will be reviewed in some detail, focusing on recent results that demonstrate consistency with the picture of non-abelian charges. The implications of this in the more general physics picture is that the 5/2 excitations, shown to be non-abelian, should exhibit the properties of Majorana operators. This will be the topic of the last review section.

  17. Dynamic Charge Carrier Trapping in Quantum Dot Field Effect Transistors.

    PubMed

    Zhang, Yingjie; Chen, Qian; Alivisatos, A Paul; Salmeron, Miquel

    2015-07-01

    Noncrystalline semiconductor materials often exhibit hysteresis in charge transport measurements whose mechanism is largely unknown. Here we study the dynamics of charge injection and transport in PbS quantum dot (QD) monolayers in a field effect transistor (FET). Using Kelvin probe force microscopy, we measured the temporal response of the QDs as the channel material in a FET following step function changes of gate bias. The measurements reveal an exponential decay of mobile carrier density with time constants of 3-5 s for holes and ?10 s for electrons. An Ohmic behavior, with uniform carrier density, was observed along the channel during the injection and transport processes. These slow, uniform carrier trapping processes are reversible, with time constants that depend critically on the gas environment. We propose that the underlying mechanism is some reversible electrochemical process involving dissociation and diffusion of water and/or oxygen related species. These trapping processes are dynamically activated by the injected charges, in contrast with static electronic traps whose presence is independent of the charge state. Understanding and controlling these processes is important for improving the performance of electronic, optoelectronic, and memory devices based on disordered semiconductors. PMID:26099508

  18. Quantum effects in many-body gravitating systems

    NASA Astrophysics Data System (ADS)

    Golovko, V. A.

    2005-07-01

    A hierarchy of equations for equilibrium reduced density matrices obtained earlier is used to consider systems of spinless bosons bound by forces of gravity alone. The systems are assumed to be at absolute zero of temperature under conditions of Bose condensation. In this case, a peculiar interplay of quantum effects and of very weak gravitational interaction between microparticles occurs. As a result, there can form spatially bounded equilibrium structures macroscopic in size, both immobile and rotating. The size of a structure is inversely related to the number of particles in the structure. When the number of particles is relatively small the size can be enormous, whereas if this number equals Avogadro's number the radius of the structure is about 30 cm in the case that the structure consists of hydrogen atoms. The rotating objects have the form of rings and exhibit superfluidity. An atmosphere that can be captured by tiny celestial bodies from the ambient medium is considered too. The thickness of the atmosphere decreases as its mass increases. If short-range intermolecular forces are taken into account, the results obtained hold for excited states whose lifetime can however be very long. The results of the paper can be utilized for explaining the first stage of formation of celestial bodies from interstellar and even intergalactic gases.

  19. Effect of laser polarization on quantum electrodynamical cascading

    SciTech Connect

    Bashmakov, V. F.; Nerush, E. N.; Kostyukov, I. Yu.; Fedotov, A. M.; Narozhny, N. B.

    2014-01-15

    Development of quantum electrodynamical (QED) cascades in a standing electromagnetic wave for circular and linear polarizations is simulated numerically with a 3D PIC-MC code. It is demonstrated that for the same laser energy the number of particles produced in a circularly polarized field is greater than in a linearly polarized field, though the acquiring mean energy per particle is larger in the latter case. The qualitative model of laser-assisted QED cascades is extended by including the effect of polarization of the field. It turns out that cascade dynamics is notably more complicated in the case of linearly polarized field, where separation into the qualitatively different “electric” and “magnetic” regions (where the electric field is stronger than the magnetic field and vice versa) becomes essential. In the “magnetic” regions, acceleration is suppressed, and moreover the high-energy electrons are even getting cooled by photon emission. The volumes of the “electric” and “magnetic” regions evolve periodically in time and so does the cascade growth rate. In contrast to the linear polarization, the charged particles can be accelerated by circularly polarized wave even in “magnetic region.” The “electric” and “magnetic” regions do not evolve in time, and cascade growth rate almost does not depend on time for circular polarization.

  20. Photooxidation and quantum confinement effects in exfoliated black phosphorus

    NASA Astrophysics Data System (ADS)

    Favron, Alexandre; Gaufrs, Etienne; Fossard, Frdric; Phaneuf-L'Heureux, Anne-Laurence; Tang, Nathalie Y.-W.; Lvesque, Pierre L.; Loiseau, Annick; Leonelli, Richard; Francoeur, Sbastien; Martel, Richard

    2015-08-01

    Thin layers of black phosphorus have recently raised interest owing to their two-dimensional (2D) semiconducting properties, such as tunable direct bandgap and high carrier mobilities. This lamellar crystal of phosphorus atoms can be exfoliated down to monolayer 2D-phosphane (also called phosphorene) using procedures similar to those used for graphene. Probing the properties has, however, been challenged by a fast degradation of the thinnest layers on exposure to ambient conditions. Herein, we investigate this chemistry using in situ Raman and transmission electron spectroscopies. The results highlight a thickness-dependent photoassisted oxidation reaction with oxygen dissolved in adsorbed water. The oxidation kinetics is consistent with a phenomenological model involving electron transfer and quantum confinement as key parameters. A procedure carried out in a glove box is used to prepare mono-, bi- and multilayer 2D-phosphane in their pristine states for further studies on the effect of layer thickness on the Raman modes. Controlled experiments in ambient conditions are shown to lower the Ag1/Ag2 intensity ratio for ultrathin layers, a signature of oxidation.

  1. Quantum waveguide theory of the Josephson effect in multiband superconductors

    NASA Astrophysics Data System (ADS)

    Nappi, C.; Romeo, F.; Sarnelli, E.; Citro, R.

    2015-12-01

    We formulate a quantum waveguide theory of the Josephson effect in multiband superconductors, with special emphasis on iron-based materials. By generalizing the boundary conditions of the scattering problem, we first determine the Andreev levels spectrum and then derive an explicit expression for the Josephson current which generalizes the formula of the single-band case. In deriving the results, we provide a second quantization field theory, allowing us to evaluate the current-phase relation and the Josephson current fluctuations in multiband systems. We present results for two different order parameter symmetries, namely s and s++, which are relevant in multiband systems. The obtained results show that the s symmetry can support ? states which are absent in the s++ case. We also argue that there is a certain fragility of the Josephson current against phase fluctuations in the s++ case. The temperature dependence of the Josephson critical current is also analyzed and we find, for both the order parameter symmetries, remarkable violations of the Ambegaokar-Baratoff relation. The results are relevant in view of possible experiments aimed at investigating the order parameter symmetry of multiband superconductors using mesoscopic Josephson junctions.

  2. Photooxidation and quantum confinement effects in exfoliated black phosphorus.

    PubMed

    Favron, Alexandre; Gaufrs, Etienne; Fossard, Frdric; Phaneuf-L'Heureux, Anne-Laurence; Tang, Nathalie Y-W; Lvesque, Pierre L; Loiseau, Annick; Leonelli, Richard; Francoeur, Sbastien; Martel, Richard

    2015-08-01

    Thin layers of black phosphorus have recently raised interest owing to their two-dimensional (2D) semiconducting properties, such as tunable direct bandgap and high carrier mobilities. This lamellar crystal of phosphorus atoms can be exfoliated down to monolayer 2D-phosphane (also called phosphorene) using procedures similar to those used for graphene. Probing the properties has, however, been challenged by a fast degradation of the thinnest layers on exposure to ambient conditions. Herein, we investigate this chemistry using in situ Raman and transmission electron spectroscopies. The results highlight a thickness-dependent photoassisted oxidation reaction with oxygen dissolved in adsorbed water. The oxidation kinetics is consistent with a phenomenological model involving electron transfer and quantum confinement as key parameters. A procedure carried out in a glove box is used to prepare mono-, bi- and multilayer 2D-phosphane in their pristine states for further studies on the effect of layer thickness on the Raman modes. Controlled experiments in ambient conditions are shown to lower the A(g)(1)/A(g)(2) intensity ratio for ultrathin layers, a signature of oxidation. PMID:26006004

  3. Energy spectrum and quantum Hall effect in twisted bilayer graphene

    NASA Astrophysics Data System (ADS)

    Moon, Pilkyung; Koshino, Mikito

    2012-05-01

    We investigate the electronic structure and the quantum Hall effect in twisted bilayer graphenes with various rotation angles in the presence of magnetic field. Using a low-energy approximation, which incorporates the rigorous interlayer interaction, we computed the energy spectrum and the quantized Hall conductivity in a wide range of magnetic field from the semiclassical regime to the fractal spectrum regime. In weak magnetic fields, the low-energy conduction band is quantized into electronlike and holelike Landau levels at energies below and above the van Hove singularity, respectively, and the Hall conductivity sharply drops from positive to negative when the Fermi energy goes through the transition point. In increasing magnetic field, the spectrum gradually evolves into a fractal band structure called Hofstadter's butterfly, where the Hall conductivity exhibits a nonmonotonic behavior as a function of Fermi energy. The typical electron density and magnetic field amplitude characterizing the spectrum monotonically decrease as the rotation angle is reduced, indicating that the rich electronic structure may be observed in a moderate condition.

  4. Quantum tunneling observed without its characteristic large kinetic isotope effects.

    PubMed

    Hama, Tetsuya; Ueta, Hirokazu; Kouchi, Akira; Watanabe, Naoki

    2015-06-16

    Classical transition-state theory is fundamental to describing chemical kinetics; however, quantum tunneling is also important in explaining the unexpectedly large reaction efficiencies observed in many chemical systems. Tunneling is often indicated by anomalously large kinetic isotope effects (KIEs), because a particle's ability to tunnel decreases significantly with its increasing mass. Here we experimentally demonstrate that cold hydrogen (H) and deuterium (D) atoms can add to solid benzene by tunneling; however, the observed H/D KIE was very small (1-1.5) despite the large intrinsic H/D KIE of tunneling (≳ 100). This strong reduction is due to the chemical kinetics being controlled not by tunneling but by the surface diffusion of the H/D atoms, a process not greatly affected by the isotope type. Because tunneling need not be accompanied by a large KIE in surface and interfacial chemical systems, it might be overlooked in other systems such as aerosols or enzymes. Our results suggest that surface tunneling reactions on interstellar dust may contribute to the deuteration of interstellar aromatic and aliphatic hydrocarbons, which could represent a major source of the deuterium enrichment observed in carbonaceous meteorites and interplanetary dust particles. These findings could improve our understanding of interstellar physicochemical processes, including those during the formation of the solar system. PMID:26034285

  5. Quantum tunneling observed without its characteristic large kinetic isotope effects

    PubMed Central

    Hama, Tetsuya; Ueta, Hirokazu; Kouchi, Akira; Watanabe, Naoki

    2015-01-01

    Classical transition-state theory is fundamental to describing chemical kinetics; however, quantum tunneling is also important in explaining the unexpectedly large reaction efficiencies observed in many chemical systems. Tunneling is often indicated by anomalously large kinetic isotope effects (KIEs), because a particle’s ability to tunnel decreases significantly with its increasing mass. Here we experimentally demonstrate that cold hydrogen (H) and deuterium (D) atoms can add to solid benzene by tunneling; however, the observed H/D KIE was very small (1–1.5) despite the large intrinsic H/D KIE of tunneling (≳100). This strong reduction is due to the chemical kinetics being controlled not by tunneling but by the surface diffusion of the H/D atoms, a process not greatly affected by the isotope type. Because tunneling need not be accompanied by a large KIE in surface and interfacial chemical systems, it might be overlooked in other systems such as aerosols or enzymes. Our results suggest that surface tunneling reactions on interstellar dust may contribute to the deuteration of interstellar aromatic and aliphatic hydrocarbons, which could represent a major source of the deuterium enrichment observed in carbonaceous meteorites and interplanetary dust particles. These findings could improve our understanding of interstellar physicochemical processes, including those during the formation of the solar system. PMID:26034285

  6. Quantum Hall effect and the topological number in graphene

    NASA Astrophysics Data System (ADS)

    Hasegawa, Yasumasa; Kohmoto, Mahito

    2006-10-01

    Recently, an unusual integer quantum Hall effect was observed in graphene in which the Hall conductivity is quantized as σxy=(±2,±6,±10,…)×e2/h , where e is the electron charge and h is the Planck constant. To explain this we consider the energy structure as a function of magnetic field (the Hofstadter butterfly diagram) on the honeycomb lattice and the Streda formula for Hall conductivity. The quantized Hall conductivities are identified as the topological TKNN integers [D. J. Thouless, M. Kohmoto, M. P. Nightingale, and M. den Nijs, Phys. Rev. Lett. 49, 405 (1982); M. Kohmoto, Ann. Phys. (N.Y.) 160, 343 (1985)]. They are odd integers ±1,±3,±5,…×2 (spin degrees of freedom) when a uniform magnetic field is as high as 30T for example. The gaps corresponding to even integers, ±2,±4,±6,… are too small to be observed, but when the system is anisotropic, which is described by the generalized honeycomb lattice, and/or in an extremely strong magnetic field, quantization in even integers takes place as well. We also compare the results with those for the square lattice in an extremely strong magnetic field.

  7. Undoing the effect of loss on quantum entanglement

    NASA Astrophysics Data System (ADS)

    Ulanov, Alexander E.; Fedorov, Ilya A.; Pushkina, Anastasia A.; Kurochkin, Yury V.; Ralph, Timothy C.; Lvovsky, A. I.

    2015-11-01

    Entanglement distillation, the purpose of which is to probabilistically increase the strength and purity of quantum entanglement, is a primary element of many quantum communication and computation protocols. It is particularly necessary in quantum repeaters in order to counter the degradation of entanglement that inevitably occurs due to losses in communication lines. Here, we distil the EinsteinPodolskyRosen state of light, the workhorse of continuous-variable entanglement, using noiseless amplification. The advantage of our technique is that it permits recovering a macroscopic level of entanglement, however low the initial entanglement or however high the loss may be. Experimentally, we recover the original entanglement level after one of the EinsteinPodolskyRosen modes has experienced a loss factor of 20. The level of entanglement in our distilled state is higher than that achievable by direct transmission of any state through a similar loss channel. This is a key step towards realizing practical continuous-variable quantum communication protocols.

  8. Condensed-matter physics: Quantum dots and the Kondo effect

    NASA Astrophysics Data System (ADS)

    Le Hur, Karyn

    2015-10-01

    Nanotechnology studies explore the extreme properties of strongly interacting electronic systems through conductance measurements, and probe quantum phase transitions close to absolute zero temperature. See Letters p.233 & p.237

  9. Structural properties and quantum effects in protonated helium clusters. II. Quantum Monte Carlo calculations for the smaller aggregates

    NASA Astrophysics Data System (ADS)

    Balta, B.; Gianturco, F. A.; Paesani, F.

    2000-04-01

    The computed interaction potential energy surface between an He atom and the ionic core unit (HHe 2) +, discussed in the preceding paper, is employed here to analyse the structures of the protonated, small clusters of He, and to evaluate the effects of quantum behaviour on the results reached in previous dynamical calculations carried out using ab initio classical dynamics. The method of the present analysis involves numerical solutions of diffusion Monte Carlo (DMC) equations via random walk techniques and allows us to extract global minimum energy configurations for the quantum ground-states of the smaller clusters. The values of the zero point energy, the effect of competitive growth dynamics between various configurations and the evidence for the presence of clear shell structures in the protonated clusters are among the features from the present DMC calculations, which we discuss in this work.

  10. Optimizing hierarchical equations of motion for quantum dissipation and quantifying quantum bath effects on quantum transfer mechanisms

    NASA Astrophysics Data System (ADS)

    Ding, Jin-Jin; Xu, Rui-Xue; Yan, YiJing

    2012-06-01

    We present an optimized hierarchical equations of motion theory for quantum dissipation in multiple Brownian oscillators bath environment, followed by a mechanistic study on a model donor-bridge-acceptor system. We show that the optimal hierarchy construction, via the memory-frequency decomposition for any specified Brownian oscillators bath, is generally achievable through a universal pre-screening search. The algorithm goes by identifying the candidates for the best be just some selected Pad spectrum decomposition based schemes, together with a priori accuracy control criterions on the sole approximation, the white-noise residue ansatz, involved in the hierarchical construction. Beside the universal screening search, we also analytically identify the best for the case of Drude dissipation and that for the Brownian oscillators environment without strongly underdamped bath vibrations. For the mechanistic study, we quantify the quantum nature of bath influence and further address the issue of localization versus delocalization. Proposed are a reduced system entropy measure and a state-resolved constructive versus destructive interference measure. Their performances on quantifying the correlated system-environment coherence are exemplified in conjunction with the optimized hierarchical equations of motion evaluation of the model system dynamics, at some representing bath parameters and temperatures. Analysis also reveals the localization to delocalization transition as temperature decreases.

  11. Effective-field-theory model for the fractional quantum Hall effect

    NASA Technical Reports Server (NTRS)

    Zhang, S. C.; Hansson, T. H.; Kivelson, S.

    1989-01-01

    Starting directly from the microscopic Hamiltonian, a field-theory model is derived for the fractional quantum Hall effect. By considering an approximate coarse-grained version of the same model, a Landau-Ginzburg theory similar to that of Girvin (1986) is constructed. The partition function of the model exhibits cusps as a function of density. It is shown that the collective density fluctuations are massive.

  12. Young Double Slit Interference Effects at Quantum Level

    NASA Astrophysics Data System (ADS)

    Ozer, Z. N.; Chaluvadi, H.; Ulu, M.; Dogan, M.; Aktas, B.; Madison, D.

    2014-04-01

    The currently accepted model for quantum interference resulting from the emission of electron waves from two scattering centers induced by either light or charged particle impact is analogous to Young's emission of two light waves from two slits. In this work we show that this simple classical wave model is incomplete and that there is a more complicated quantum interference pattern for low energy ionization caused by electron impact.

  13. Supersymmetric Quantum-Hall Effect on a Fuzzy Supersphere

    SciTech Connect

    Hasebe, Kazuki

    2005-05-27

    Supersymmetric quantum-Hall liquids are constructed on a supersphere in a supermonopole background. We derive a supersymmetric generalization of the Laughlin wave function, which is a ground state of a hard-core OSp(1 vertical bar 2) invariant Hamiltonian. We also present excited topological objects, which are fractionally charged deficits made by super Hall currents. Several relations between quantum-Hall systems and their supersymmetric extensions are discussed.

  14. Development of a Position Sensitive Beta and Recoil Ion Detectors for the 6He ? - ? Angular Correlation Measurement

    NASA Astrophysics Data System (ADS)

    Hong, Ran; Bagdasarova, Yelena; Garcia, Alejandro; Storm, Derek; Sternberg, Matthew; Swanson, Erik; Wauters, Frederik; Zumwalt, David; Bailey, Kevin; Leredde, Arnaud; Mueller, Peter; O'Connor, Thomas; Flchard, Xavier; Liennard, Etienne; Knecht, Andreas; Naviliat-Cuncic, Oscar

    2014-09-01

    In order to measure the ? - ? angular correlation coefficient a and put more stringent limits on exotic tensor type weak currents, we constructed a system which detects ? particles in coincidence with recoil ions from the ?-decay of laser trapped 6He atoms. The ? particles are detected by a scintillator and a multi-wire proportional chamber (MWPC) with a capacitive charge division anode. The recoil ions are detected by a microchannel plate (MCP) with delay-line anodes. The coefficient a is extracted by fitting the coincidence data to GEANT4 based Monte Carlo simulations, which are also used to study systematic uncertainties related to the detector system. A new method of calibrating the MWPC using a cathode focusing effect will be presented. This work is supported by DOE, Office of Nuclear Physics, under contract nos. DE-AC02-06CH11357 and DE-FG02-97ER41020.

  15. Effect of source tampering in the security of quantum cryptography

    NASA Astrophysics Data System (ADS)

    Sun, Shi-Hai; Xu, Feihu; Jiang, Mu-Sheng; Ma, Xiang-Chun; Lo, Hoi-Kwong; Liang, Lin-Mei

    2015-08-01

    The security of source has become an increasingly important issue in quantum cryptography. Based on the framework of measurement-device-independent quantum key distribution (MDI-QKD), the source becomes the only region exploitable by a potential eavesdropper (Eve). Phase randomization is a cornerstone assumption in most discrete-variable (DV) quantum communication protocols (e.g., QKD, quantum coin tossing, weak-coherent-state blind quantum computing, and so on), and the violation of such an assumption is thus fatal to the security of those protocols. In this paper, we show a simple quantum hacking strategy, with commercial and homemade pulsed lasers, by Eve that allows her to actively tamper with the source and violate such an assumption, without leaving a trace afterwards. Furthermore, our attack may also be valid for continuous-variable (CV) QKD, which is another main class of QKD protocol, since, excepting the phase random assumption, other parameters (e.g., intensity) could also be changed, which directly determine the security of CV-QKD.

  16. A Model of the Recoil Shadow Anisotropy Method for the YRAST Ball Array

    NASA Astrophysics Data System (ADS)

    Swanson, D.; Beausang, C. W.; Meyer, D. A.; Millman, E. A.; Ai, H.; Casten, R. F.; Heinz, A.; McCutchan, E. A.; Plettner, C.; Qian, J.; Thomas, N. J.; Williams, E.; Winkler, R.; Zamfir, N. V.; Grdal, G.

    2004-10-01

    A model of the Recoil Shadow Anisotropy Method (RSAM)^1, a technique for measuring isomeric half-lives of recoiling nuclei, has been developed for the YRAST Ball array. RSAM uses the shadowing effect of collimators on four-leaf clover detectors to determine anisotropies, or ratios of ?-ray decay intensities in different leaves, as a function of source position. For an isotropic stationary source, the anisotropy should depend only on the ratio of the solid angles of the leaves. Based on the geometry of YRAST Ball, a model was constructed to predict the anisotropy ratio as a function of source position and ?-ray energy for both stationary and moving sources. Theoretical predictions are being compared with calibration data obtained from a stationary ^152Eu source at various positions. Results will be presented. Work supported by US DOE under Grant Nos. DE-FG02-91ER-40609, DE-FG03-03NA-00081, and DE-FG02-88ER-40417. ^1 E. Gueorguieva et al., Nucl. Instr. and Meth. A 474 (2001) 132-142.

  17. Recoil ion charge state distribution following the beta(sup +) decay of {sup 21}Na

    SciTech Connect

    Scielzo, Nicholas D.; Freedman, Stuart J.; Fujikawa, Brian K.; Vetter, Paul A.

    2003-01-03

    The charge state distribution following the positron decay of 21Na has been measured, with a larger than expected fraction of the daughter 21Ne in positive charge states. No dependence on either the positron or recoil nucleus energy is observed. The data is compared to a simple model based on the sudden approximation. Calculations suggest a small but important contribution from recoil ionization has important consequences for precision beta decay correlation experiments detecting recoil ions.

  18. The effect of finite Larmor radius corrections on Jeans instability of quantum plasma

    SciTech Connect

    Sharma, Prerana; Chhajlani, R. K.

    2013-09-15

    The influence of finite Larmor radius (FLR) effects on the Jeans instability of infinitely conducting homogeneous quantum plasma is investigated. The quantum magnetohydrodynamic (QMHD) model is used to formulate the problem. The contribution of FLR is incorporated to the QMHD set of equations in the present analysis. The general dispersion relation is obtained analytically using the normal mode analysis technique which is modified due to the contribution of FLR corrections. From general dispersion relation, the condition of instability is obtained and it is found that Jeans condition is modified due to quantum effect. The general dispersion relation is reduced for both transverse and longitudinal mode of propagations. The condition of gravitational instability is modified due to the presence of both FLR and quantum corrections in the transverse mode of propagation. In longitudinal case, it is found to be unaffected by the FLR effects but modified due to the quantum corrections. The growth rate of Jeans instability is discussed numerically for various values of quantum and FLR corrections of the medium. It is found that the quantum parameter and FLR effects have stabilizing influence on the growth rate of instability of the system.

  19. The effect of finite Larmor radius corrections on Jeans instability of quantum plasma

    NASA Astrophysics Data System (ADS)

    Sharma, Prerana; Chhajlani, R. K.

    2013-09-01

    The influence of finite Larmor radius (FLR) effects on the Jeans instability of infinitely conducting homogeneous quantum plasma is investigated. The quantum magnetohydrodynamic (QMHD) model is used to formulate the problem. The contribution of FLR is incorporated to the QMHD set of equations in the present analysis. The general dispersion relation is obtained analytically using the normal mode analysis technique which is modified due to the contribution of FLR corrections. From general dispersion relation, the condition of instability is obtained and it is found that Jeans condition is modified due to quantum effect. The general dispersion relation is reduced for both transverse and longitudinal mode of propagations. The condition of gravitational instability is modified due to the presence of both FLR and quantum corrections in the transverse mode of propagation. In longitudinal case, it is found to be unaffected by the FLR effects but modified due to the quantum corrections. The growth rate of Jeans instability is discussed numerically for various values of quantum and FLR corrections of the medium. It is found that the quantum parameter and FLR effects have stabilizing influence on the growth rate of instability of the system.

  20. Exploring Nuclear Effects in the Dynamics of Nanomaterials with a Quantum Trajectory-Electronic Structure Approach

    NASA Astrophysics Data System (ADS)

    Garashchuk, Sophya

    2014-03-01

    A massively parallel, direct quantum molecular dynamics method is described. The method combines a quantum trajectory (QT) representation of the nuclear wavefunction discretized into an ensemble of trajectories with an electronic structure (ES) description of electrons, namely using the Density Functional Tight Binding (DFTB) theory. Quantum nuclear effects are included into the dynamics of the nuclei via quantum corrections to the classical forces. To reduce computational cost and increase numerical accuracy, the quantum corrections to dynamics resulting from localization of the nuclear wavefunction are computed approximately and included into selected degrees of freedom representing light particles where the quantum effects are expected to be the most pronounced. A massively parallel implementation, based on the Message Passing Interface allows for efficient simulations of ensembles of thousands of trajectories at once. The QTES-DFTB dynamics approach is employed to study the role of quantum nuclear effects on the interaction of hydrogen with a model graphene sheet, revealing that neglect of nuclear effects can lead to an overestimation of adsorption. Supported by the National Science Foundation and the Petroleum Research Fund of the American Chemical Society.