Stimulated Rayleigh resonances and recoil-induced effects
Courtois, J.Y.; Grynberg, G.
1996-12-31
The organization of this paper is as follows. We present in Section II the basic ideas about stimulated Rayleigh scattering by considering more particularly the situation where it arises from a relaxation process going on in the material system, and we describe a few experimental observations made in atomic and molecular physics. We then consider the case of nonstationary two-level atoms, and we derive the shape and characteristics of the recoil-induced resonances (Section III). In particular, we show that these resonances can be interpreted either as originating from a stimulated Rayleigh effect or as a stimulated Raman phenomena between atomic energy-momentum states having different momenta. Finally, to make a clear distinction between the physical phenomena that pertain directly to recoil-induced processes (i.e., that actually permit the measurement of the photon recoil) and those for which the introduction of the recoil constitutes a mere physical convenience, we review in Section IV some indisputable manifestations of the photon recoil in atomic and molecular physics. 92 refs., 22 figs.
Accounting for Recoil Effects in Geochronometers: A New Model Approach
NASA Astrophysics Data System (ADS)
Lee, V. E.; Huber, C.
2012-12-01
A number of geologically important chronometers are affected by, or owe their utility to, the "recoil effect". This effect describes the physical displacement of a nuclide due to energetic nuclear processes such as radioactive alpha decay (as in the case of various parent-daughter pairs in the uranium-series decay chains, and Sm-Nd), as well as neutron irradiation (in the case of the methodology for the 40Ar/39Ar dating method). The broad range of affected geochronometers means that the recoil effect can impact a wide range of dating method applications in the geosciences, including but not limited to: Earth surface processes, paleoclimate, volcanic processes, and cosmochemistry and planetary evolution. In particular, the recoil effect can have a notable impact on the use of fine grains (silt- and clay-sized particles) for geochronometric dating purposes. This is because recoil-induced loss of a nuclide from the surfaces of a grain can create an isotopically-depleted outer rind, and for small grains, this depleted rind can be volumetrically significant. When this recoil loss is measurable and occurs in a known time-dependent fashion, it can usefully serve as the basis for chronometers (such as the U-series comminution age method); in other cases recoil loss from fine particles creates an unwanted deviation from expected isotope values (such as for the Ar-Ar method). To improve both the accuracy and precision of ages inferred from geochronometric systems that involve the recoil of a key nuclide from small domains, it is necessary to quantify the magnitude of the recoil loss of that particular nuclide. It is also necessary to quantitatively describe the effect of geological processes that can alter the outer surface of grains, and hence the isotopically-depleted rind. Here we present a new mathematical and numerical model that includes two main features that enable enhanced accuracy and precision of ages determined from geochronometers. Since the surface area of the
Dielectric barrier structure with hollow electrodes and its recoil effect
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.
Quantum effects in electron beam pumped GaAs
Yahia, M. E.; 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.
Black hole as a point radiator and recoil effect on the brane world.
Frolov, Valeri; Stojković, Dejan
2002-10-01
A small black hole attached to a brane in a higher-dimensional space emitting quanta into the bulk may leave the brane as a result of a recoil. We construct a field theory model in which such a black hole is described as a massive scalar particle with internal degrees of freedom. In this model, the probability of transition between the different internal levels is identical to the probability of thermal emission calculated for the Schwarzschild black hole. The discussed recoil effect implies that the thermal emission of the black holes, which might be created by interaction of high energy particles in colliders, could be terminated and the energy nonconservation can be observed in the brane experiments.
The alpha-recoil effects of uranium in the Oklo reactor
NASA Astrophysics Data System (ADS)
Sheng, Z. Z.; Kuroda, P. K.
1984-12-01
A series of acid-leaching experiments have been carried out on a sample of uranium ore from reactor zone number 10 of the Oklo mines in Gabon. Anomalously high U-234/U-238 ratios were observed accompanied by modestly increased U-235/U-238 ratios in uranium fractions. These results, which can be interpreted as being due to the alpha-recoil effects of U-238 and Pu-239, provide a convenient way of calculating the conversion factor (the fraction of uranium atoms converted to plutonium) of the natural reactors from radiochemical data, obviating the necessity for mass-spectrometric measurements.
Recoil effects due to electron shake-off following the beta decay of 6 He
NASA Astrophysics Data System (ADS)
Drake, Gordon W. F.; Schulhoff, Eva
2016-05-01
There are currently several experiments in progress to search for new physics beyond the Standard Model by high precision studies of angular correlations in the β decay of the helium isotope 6He to form 6Li +e- +νe. After the β decay process, the atomic electrons of 6 Li+ adjust to the sudden change of nuclear charge from 2 to 3. We calculate the probabilities for electron shake-up and shake-off, including recoil effects, by the use of a Stieltjes imaging representation of the final states. A variety of sum rules provides tight consistency checks on the accuracy of the results. Results obtained previously indicate that there is a 7 σ disagreement between theory and experiment for the additional nuclear recoil induced by the emission of atomic shake-off electrons. This disagreement will be further studied, and the results extended to the 1 s 2 p3 P and metastable 1 s 2 s3 S states as initial states of 6 He before β-decay. Research supported by the Natural Sciences and Engineering Research Council of Canada.
Jeans instability with exchange effects in quantum dusty magnetoplasmas
Jamil, M.; Rasheed, A.; Rozina, Ch.; Jung, Y.-D.; Salimullah, M.
2015-08-15
Jeans instability is examined in magnetized quantum dusty plasmas using the quantum hydrodynamic model. The quantum effects are considered via exchange-correlation potential, recoil effect, and Fermi degenerate pressure, in addition to thermal effects of plasma species. It is found that the electron exchange and correlation potential have significant effects over the threshold value of wave vector and Jeans instability. The presence of electron exchange and correlation effect shortens the time of dust sound that comparatively stabilizes the self gravitational collapse. The results at quantum scale are helpful in understanding the collapse of the self-gravitating dusty plasma systems.
Quantum radiation reaction effects in multiphoton Compton scattering.
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.
Quantum Radiation Reaction Effects in Multiphoton Compton Scattering
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.
alpha-Actin: disposition, quantities, and estimated effects on lung recoil and compliance.
Oldmixon, E H; Carlsson, K; Kuhn, C; Butler, J P; Hoppin, F G
2001-07-01
We have investigated the basis and implications of pneumoconstriction by measuring disposition and quantities of alpha-smooth muscle actin in rat and guinea pig lungs and modeling its effects on lung recoil and compliance. A robust marker of contractility, alpha-smooth muscle actin appears in smooth muscle or myofibroblast-like cells in pleura, airways, blood vessels, and alveolar ductal tissues. In each site, we measured its transected area by immunofluorescent staining and frequency-modulated scanning confocal microscopy. We incorporated these data in a model of the parenchyma consisting of an extensive elastic network with embedded contractile structures. We conclude that contraction at any one of these sites alone can decrease parenchymal compliance by 20-30% during tidal breathing. This is due mostly to the stiffness of activated contractile elements undergoing passive cycling; constant muscle tension would have little effect. The magnitude of the effect corresponds with known responses of the lung to hypocapnia, consistent with a homeostatic function in which gas exchange is defended by redistributing ventilation away from overventilated units. PMID:11408464
Effect of recoiled O on damage regrowth and electrical properties of through-oxide implanted Si
Sadana, D.K.; Wu, N.R.; Washburn, J.; Current, M.; Morgan, A.; Reed, D.; Maenpaa, M.
1982-10-01
High dose (4 to 7.5 x 10/sup 15/ cm/sup -2/) As implantations into p-type (100) Si have been carried out through a screen-oxide of thicknesses less than or equal to 775A and without screen oxide. The effect of recoiled O on damage annealing and electrical properties of the implanted layers has been investigated using a combination of the following techniques: TEM, RBS/MeV He/sup +/ channeling, SIMS and Hall measurements in conjunction with chemical stripping and sheet resistivity measurements. The TEM results show that there is a dramatically different annealing behavior of the implantation damage for the through oxide implants (Case I) as compared to implants into bare silicon (Case II). Comparison of the structural defect profiles with O distributions obtained by SIMS demonstrated that retardation in the secondary damage growth in Case I can be directly related with the presence of O. Weak-beam TEM showed that a high density of fine defect clusters (less than or equal to 50A) were present both in Case I and Case II. The electrical profiles showed only 30% of the total As to be electrically active. The structural and electrical results have been explained by a model that entails As-O, Si-O and As-As complex formation and their interaction with the dislocations.
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.
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 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.
Dynamical formation of horizons in recoiling D-branes
Ellis, John; Mavromatos, N. E.; Nanopoulos, D. V.
2000-10-15
A toy calculation of string or D-particle interactions within a world-sheet approach indicates that quantum recoil effects -- reflecting the gravitational back reaction on space-time foam due to the propagation of energetic particles -- induces the appearance of a microscopic event horizon, or ''bubble,'' inside which stable matter can exist. The scattering event causes this horizon to expand, but we expect quantum effects to cause it to contract again, in a ''bounce'' solution. Within such ''bubbles,'' massless matter propagates with an effective velocity that is less than the velocity of light in vacuo, which may lead to observable violations of Lorentz symmetry that may be tested experimentally. The conformal invariance conditions in the interior geometry of the bubbles select preferentially 3 for the number of the spatial dimensions, corresponding to a consistent formulation of the interaction of D3-branes with recoiling D particles, which are allowed to fluctuate independently only on the D3-brane hypersurface.
Dynamical formation of horizons in recoiling D-branes
NASA Astrophysics Data System (ADS)
Ellis, John; Mavromatos, N. E.; Nanopoulos, D. V.
2000-10-01
A toy calculation of string or D-particle interactions within a world-sheet approach indicates that quantum recoil effects-reflecting the gravitational back reaction on space-time foam due to the propagation of energetic particles-induces the appearance of a microscopic event horizon, or ``bubble,'' inside which stable matter can exist. The scattering event causes this horizon to expand, but we expect quantum effects to cause it to contract again, in a ``bounce'' solution. Within such ``bubbles,'' massless matter propagates with an effective velocity that is less than the velocity of light in vacuo, which may lead to observable violations of Lorentz symmetry that may be tested experimentally. The conformal invariance conditions in the interior geometry of the bubbles select preferentially 3 for the number of the spatial dimensions, corresponding to a consistent formulation of the interaction of D3-branes with recoiling D particles, which are allowed to fluctuate independently only on the D3-brane hypersurface.
Potential effects of alpha-recoil on uranium-series dating of calcrete
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 (1σ), 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 α-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
NASA Astrophysics Data System (ADS)
Petrosky, T.; Tasaki, S.; Prigogine, I.
1991-01-01
In 1977, Misra and Sudarshan showed, based on the quantum measurement theory, that an unstable particle will never be found to decay when it is continuously observed. They called it the quantum Zeno effect (or paradox). More generally the quantum Zeno effect is associated to the inhibition of transitions by frequent measurements. This possibility has attracted much interest over the last years. Recently, Itano, Heinzen, Bollinger and Wineland have reported that they succeeded in observing the quantum Zeno effect. This would indeed be an important step towards the understanding of the role of the observer in quantum mechanics. However, in the present paper, we will show that their results can be recovered through conventional quantum mechanics and do not involve a repeated reduction (or collapse) of the wave function.
Quantum Hall effect in quantum electrodynamics
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.
Force optimized recoil control system
NASA Astrophysics Data System (ADS)
Townsend, P. E.; Radkiewicz, R. J.; Gartner, R. F.
1982-05-01
Reduction of the recoil force of high rate of fire automatic guns was proven effective. This system will allow consideration of more powerful guns for use in both helicopter and armored personnel carrier applications. By substituting the large shock loads of firing guns with a nearly constant force, both vibration and fatigue problems that prevent mounting of powerful automatic guns is eliminated.
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.
Bernevig, B Andrei; Zhang, Shou-Cheng
2006-03-17
The quantum Hall liquid is a novel state of matter with profound emergent properties such as fractional charge and statistics. The existence of the quantum Hall effect requires breaking of the time reversal symmetry caused by an external magnetic field. In this work, we predict a quantized spin Hall effect in the absence of any magnetic field, where the intrinsic spin Hall conductance is quantized in units of 2(e/4pi). The degenerate quantum Landau levels are created by the spin-orbit coupling in conventional semiconductors in the presence of a strain gradient. This new state of matter has many profound correlated properties described by a topological field theory.
Bernevig, B.Andrei; Zhang, Shou-Cheng; /Stanford U., Phys. Dept.
2010-01-15
The quantum Hall liquid is a novel state of matter with profound emergent properties such as fractional charge and statistics. Existence of the quantum Hall effect requires breaking of the time reversal symmetry caused by an external magnetic field. In this work, we predict a quantized spin Hall effect in the absence of any magnetic field, where the intrinsic spin Hall conductance is quantized in units of 2 e/4{pi}. The degenerate quantum Landau levels are created by the spin-orbit coupling in conventional semiconductors in the presence of a strain gradient. This new state of matter has many profound correlated properties described by a topological field theory.
NASA Astrophysics Data System (ADS)
Grössing, G.; Fussy, S.; Mesa Pascasio, J.; Schwabl, H.
2015-07-01
We show that during stochastic beam attenuation in double slit experiments, there appear unexpected new effects for transmission factors below a ≤ 10-4, which can eventually be observed with the aid of weak measurement techniques. These are denoted as quantum sweeper effects, which are characterized by the bunching together of low counting rate particles within very narrow spatial domains. We employ a “superclassical” modeling procedure which we have previously shown to produce predictions identical with those of standard quantum theory. Thus it is demonstrated that in reaching down to ever weaker channel intensities, the nonlinear nature of the probability density currents becomes ever more important. We finally show that the resulting unexpected effects nevertheless implicitly also exist in standard quantum mechanics.
Photon Recoil Momentum in Dispersive Media
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.
Transport of Radioactive Material by Alpha Recoil
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.
NASA Astrophysics Data System (ADS)
Bik, W. M. A.; Habraken, F. H. P. M.
1993-07-01
In elastic recoil detection (ERD) one determines the yield and energy of particles ejected out of the surface region of samples under MeV ion bombardment. By application of this surface and thin film analysis technique one can obtain quantitative information concerning the depth distribution of light elements in a sample to be analysed. The quantitativity and the depth resolving power are based on knowledge of the recoil cross section and the stopping power of high-energy ions in matter. This paper reviews the fundamentals of this technique and the various experimental methods for recoil identification. Furthermore, important features for material analysis, such as detection limits, depth resolution and elemental range are discussed. Some emphasis is put on the conversion of the spectral contribution of the elements to atomic concentrations in the films for several representative cases. Throughout the review numerous examples are given to illustrate the features of ERD and to demonstrate empirically the accuracy of the quantification method.
High acceptance recoil polarimeter
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.
Recoil by Auger electrons: Theory and application
Demekhin, Ph. V.; Scheit, S.; Cederbaum, L. S.
2009-10-28
General equations accounting for the molecular dynamics induced by the recoil of a fast Auger electron are presented. The implications of the degree of localization of the molecular orbitals of diatomic molecules involved in the Auger decay are analyzed. It is shown that the direct and exchange terms of the Auger transition matrix element may give rise to opposite signs and hence to opposite directions of the recoil momenta transferred to the nuclear vibrational motion. Consequently, these terms have a different impact on the recoil-induced nuclear dynamics in the final Auger decay state. The developed theory is applied to study the influence of the recoil on the interatomic Coulombic decay (ICD) following the K-LL Auger decay of the Ne dimer. Our calculations illustrate a significant effect of the recoil of nuclei on the computed wave packets propagating on the potential energy curve populated by the Auger decay. The corresponding final states of the Auger process decay further by ICD. We show that the recoil momentum imparted onto the nuclei modifies the computed ICD spectra considerably.
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.
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.
NASA Astrophysics Data System (ADS)
Kaulakys, B.; Gontis, V.
1997-08-01
Prevention of a quantum system's time evolution by repetitive, frequent measurements of the system's state has been called the quantum Zeno effect (or paradox). Here we investigate theoretically and numerically the effect of repeated measurements on the quantum dynamics of multilevel systems that exhibit the quantum localization of classical chaos. The analysis is based on the wave function and Schrödinger equation, without introduction of the density matrix. We show how the quantum Zeno effect in simple few-level systems can be recovered and understood by formal modeling the effect of measurement on the dynamics by randomizing the phases of the measured states. This analysis is extended to investigate the dynamics of multilevel systems driven by an intense external force and affected by frequent measurements. We show that frequent measurements of such quantum systems results in delocalization of the quantum suppression of classical chaos. This result is the opposite of the quantum Zeno effect. The phenomenon of delocalization of the quantum suppression and restoration of quasi-classical time evolution of these systems, owing to repetitive frequent measurements, can therefore be called the quantum anti-Zeno effect. From this analysis we furthermore conclude that frequently or continuously observable quasiclassical systems evolve basically in a classical manner.
Spin-orbit coupling and quantum spin Hall effect for neutral atoms without spin flips.
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
Effective equations for the quantum pendulum from momentous quantum mechanics
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.
NASA Astrophysics Data System (ADS)
Saharian, A. A.
2016-09-01
We investigate the vacuum expectation value of the current density for a charged scalar field on a slice of anti-de Sitter (AdS) space with toroidally compact dimensions. Along the compact dimensions periodicity conditions are imposed on the field operator with general phases and the presence of a constant gauge field is assumed. The latter gives rise to Aharonov-Bohm-like effects on the vacuum currents. The current density along compact dimensions is a periodic function of the gauge field flux with the period equal to the flux quantum. It vanishes on the AdS boundary and, near the horizon, to the leading order, it is conformally related to the corresponding quantity in Minkowski bulk for a massless field. For large values of the length of the compact dimension compared with the AdS curvature radius, the vacuum current decays as power-law for both massless and massive fields. This behavior is essentially different from the corresponding one in Minkowski background, where the currents for a massive field are suppressed exponentially.
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…
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.
Quantum chaos and effective thermalization.
Altland, Alexander; Haake, Fritz
2012-02-17
We demonstrate effective equilibration for unitary quantum dynamics under conditions of classical chaos. Focusing on the paradigmatic example of the Dicke model, we show how a constructive description of the thermalization process is facilitated by the Glauber Q or Husimi function, for which the evolution equation turns out to be of Fokker-Planck type. The equation describes a competition of classical drift and quantum diffusion in contractive and expansive directions. By this mechanism the system follows a "quantum smoothened" approach to equilibrium, which avoids the notorious singularities inherent to classical chaotic flows.
NASA Astrophysics Data System (ADS)
Mateja, Piotr; Wojcik, Mariusz
2016-07-01
A computer simulation method is applied to study electron-ion recombination in tracks of low-energy nuclear recoils in nonpolar liquids in which the electron transport can be described as ideal diffusion. The electron escape probability is calculated as a function of applied electric field, both for the field parallel to the track and for the field perpendicular to the track. The dependence of escape probability on the field direction is the stronger, the longer the ionization track, with a significant effect being found already for tracks of ~100 nm length. The results are discussed in the context of possible applications of nonpolar molecular liquids as target media in directional dark matter detectors.
NASA Astrophysics Data System (ADS)
Hussain, S.; Akhtar, N.
2016-09-01
Ion acoustic shocks in the electron-hole-ion semiconductor plasmas have been studied. The quantum recoil effects, exchange-correlation effects and degenerate pressure of electrons and holes are included. The ion species are considered classical and their dissipation is taken into account via the dynamic viscosity. The Korteweg de Vries Burgers equation is derived by using reductive perturbation approach. The excitation of shock waves in different semiconductor plasmas is pointed out. For numerical analyses, the plasma parameters of different semiconductors are considered. The impact of variation of the plasma parameters on the strength of the shock wave in the semiconductor plasmas is discussed.
Difference between a Photon's Momentum and an Atom's Recoil
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.
Recoil Based Fuel Breeding Fuel Structure
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
Dissipative Effects on Quantum Sticking
NASA Astrophysics Data System (ADS)
Zhang, Yanting; Clougherty, Dennis
2011-03-01
Using variational mean-field theory, many-body dissipative effects on the threshold law for quantum sticking and reflection of neutral particles are examined. For the case of an ohmic bosonic bath, we study the effects of the infrared divergence on the probability of sticking and obtain an analytic expression for the rate of sticking as an asymptotic expansion in the incident energy E . The low-energy threshold law for quantum sticking is found to be robust with respect to many-body effects and remains a universal scaling law to leading order in E . Non-universal many-body effects alter the coefficient of the rate law and the exponent of a subdominant term. We gratefully acknowledge support from NSF under DMR-0814377.
RELATIVISTIC SUPPRESSION OF BLACK HOLE RECOILS
Kesden, Michael; Sperhake, Ulrich; Berti, Emanuele
2010-06-01
Numerical-relativity simulations indicate that the black hole produced in a binary merger can recoil with a velocity up to v {sub max} {approx_equal} 4000 km s{sup -1} with respect to the center of mass of the initial binary. This challenges the paradigm that most galaxies form through hierarchical mergers, yet retain supermassive black holes (SBHs) at their centers despite having escape velocities much less than v {sub max}. Interaction with a circumbinary disk can align the binary black hole spins with their orbital angular momentum, reducing the recoil velocity of the final black hole produced in the subsequent merger. However, the effectiveness of this alignment depends on highly uncertain accretion flows near the binary black holes. In this paper, we show that if the spin S {sub 1} of the more massive binary black hole is even partially aligned with the orbital angular momentum L, relativistic spin precession on sub-parsec scales can align the binary black hole spins with each other. This alignment significantly reduces the recoil velocity even in the absence of gas. For example, if the angle between S {sub 1} and L at large separations is 10{sup 0} while the second spin S {sub 2} is isotropically distributed, the spin alignment discussed in this paper reduces the median recoil from 864 km s{sup -1} to 273 km s{sup -1} for maximally spinning black holes with a mass ratio of 9/11. This reduction will greatly increase the fraction of galaxies retaining their SBHs.
3D quantum gravity and effective noncommutative quantum field theory.
Freidel, Laurent; Livine, Etera R
2006-06-01
We show that the effective dynamics of matter fields coupled to 3D quantum gravity is described after integration over the gravitational degrees of freedom by a braided noncommutative quantum field theory symmetric under a kappa deformation of the Poincaré group.
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.
RECOILING SUPERMASSIVE BLACK HOLES IN SPIN-FLIP RADIO GALAXIES
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.
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.
Quantum Size Effects in Nanostructures
NASA Astrophysics Data System (ADS)
Wei, Ching-Ming
2006-03-01
Quantum size effects in metal thin films and metallic clusters are studied using first-principles density functional theory. For metal thin films, Pb(111), Pb(100), Al(110), and Al(111) films up to 30 monolayers are calculated. Significant oscillatory quantum size effects are found on surface energy, work function, and surface relaxations. These oscillations are correlated with the thickness dependence of the energies of confined electrons, which can be properly modelled by an energy-dependent phase shift of the electronic wave function upon reflection at the interface. It is found that a quantitative description of these quantum size effects requires full consideration of the crystal band structure. For metallic clusters, the highly symmetric particles of sizes up 4 nm (Al923, Pb923, and Au309) in the icosahedral (ico), decahedral, and cubotohedral (fcc) structures are calculated. We propose a simple scheme to compare their relative stability and to identify the quantum size effect. In addition, the famous Mackay (fcc-to-ico) transition for metallic clusters is investigated by ab-initio elastic-band method. The transition path can in general be described by an angular variable s. The barriers of the Mackay transition for large Al, Pb, and Au clusters are found to be smaller than the thermal energy at room temperature. Finally CO oxidation on metallic clusters will be presented. A catalytic reaction path for CO oxidation on Au55, Ag55, and Au25Ag30 ico clusters is found with activation energies of less than 0.5 eV. The reaction consists of a peroxolike transition intermediate involving the OOCO configuration. A crucial factor to determine the reaction rate on these clusters is identified as the co-adsorption energy of CO and O2 on these clusters.
Hyperbolic supersymmetric quantum Hall effect
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.
Protection of Quantum Correlation Through the Quantum Erasing Effect
NASA Astrophysics Data System (ADS)
Xu, Hui-Yun; Yang, Guo-Hui
2016-05-01
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.
Dissipative effects on quantum sticking.
Zhang, Yanting; Clougherty, Dennis P
2012-04-27
Using variational mean-field theory, many-body dissipative effects on the threshold law for quantum sticking and reflection of neutral and charged particles are examined. For the case of an Ohmic bosonic bath, we study the effects of the infrared divergence on the probability of sticking and obtain a nonperturbative expression for the sticking rate. We find that for weak dissipative coupling α, the low-energy threshold laws for quantum sticking are modified by an infrared singularity in the bath. The sticking probability for a neutral particle with incident energy E→0 behaves asymptotically as s~E((1+α)/2(1-α)); for a charged particle, we obtain s~E(α/2(1-α)). Thus, "quantum mirrors"-surfaces that become perfectly reflective to particles with incident energies asymptotically approaching zero-can also exist for charged particles. We provide a numerical example of the effects for electrons sticking to porous silicon via the emission of a Rayleigh phonon. PMID:22680861
Dissipative Effects on Quantum Sticking
NASA Astrophysics Data System (ADS)
Zhang, Yanting; Clougherty, Dennis P.
2012-04-01
Using variational mean-field theory, many-body dissipative effects on the threshold law for quantum sticking and reflection of neutral and charged particles are examined. For the case of an Ohmic bosonic bath, we study the effects of the infrared divergence on the probability of sticking and obtain a nonperturbative expression for the sticking rate. We find that for weak dissipative coupling α, the low-energy threshold laws for quantum sticking are modified by an infrared singularity in the bath. The sticking probability for a neutral particle with incident energy E→0 behaves asymptotically as s˜E(1+α)/2(1-α); for a charged particle, we obtain s˜Eα/2(1-α). Thus, “quantum mirrors”—surfaces that become perfectly reflective to particles with incident energies asymptotically approaching zero—can also exist for charged particles. We provide a numerical example of the effects for electrons sticking to porous silicon via the emission of a Rayleigh phonon.
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.
Recoil Separators for Nuclear Astrophysics
NASA Astrophysics Data System (ADS)
Blackmon, J. C.
2004-10-01
Hydrogen and helium capture reactions are important in many astrophysical environments. Measurements in inverse kinematics using recoil separators have demonstrated a particularly sensitive technique for studying low-yield capture reactions.(M. S. Smith, C. E. Rolfs, and C. A. Barnes, Nucl. Instrum. Meth. Phys. Res. A306) (1991) 233. This approach allows a low background rate to be achieved with a high detection efficiency (about 50%) for the particles of interest using a device with only modest acceptance. Recoil separators using a variety of ion-optic configurations have been installed at numerous accelerator facilities in the past decade and have been used to measure, for example, alpha capture reactions using stable beams(D. Rogalla et al.), Eur. Phys. J. 6 (1999) 471. and proton capture reactions using radioactive ion beams.(S. Bishop et al.), Phys. Rev. Lett. 90 (2003) 162501. Measurements in inverse kinematics are the only viable means for studying reactions on short-lived nuclei that are crucial for understanding stellar explosions, and a recoil separator optimized for the measurement of capture reactions with radioactive ion beams figures prominently into the design of the low energy experimental area at the Rare Isotope Accelerator (RIA). The operational requirements for such a device will be outlined, and recoil separator designs and characteristics will be presented.
Recoil-induced subradiance in an ultracold atomic gas
Cola, M. M.; Bigerni, D.; Piovella, N.
2009-05-15
Subradiance, i.e., the cooperative inhibition of spontaneous emission by destructive interatomic interference, can be realized in a cold atomic sample confined in a ring cavity and lightened by a two-frequency laser. The atoms, scattering the photons of the two laser fields into the cavity mode, recoil and change their momentum. Under proper conditions the atomic initial momentum state and the first two momentum recoil states form a three-level degenerate cascade. A stationary subradiant state is obtained after the scattered photons have left the cavity, leaving the atoms in a coherent superposition of the three collective momentum states. Both a semiclassical description of the process and the quantum subradiant state with its Wigner function are given. Antibunching, quantum correlations, and entanglement between the atomic modes of the subradiant state are demonstrated.
Quantum Zeno effect and quantum Zeno paradox in atomic physics
NASA Astrophysics Data System (ADS)
Block, Ellen; Berman, P. R.
1991-08-01
Itano and co-workers [Wayne M. Itano, D. J. Heinzen, J. J. Bollinger, and D. J. Wineland, Phys. Rev. A 41, 2295 (1990)] have recently reported the experimental verification of the quantum Zeno effect, which is the inhibition of a quantum transition by frequent measurements. In this article, we offer an alternative interpretation of the quantum Zeno effect. We show that an analysis of the dynamics of the full three-level system gives the same result. There is no need to assume explicitly that the wave function has collapsed, nor even to assume that an ideal measurement has been made. In addition, we differentiate between what has been referred to as the quantum Zeno effect and what has been termed the quantum Zeno paradox. The former is the inhibition of induced transitions, and the latter is the, as yet experimentally unobserved, inhibition of spontaneous decay. Our interpretation, which emphasizes the ``measurement''-induced interruption of atomic-state coherences as the cause of inhibited quantum transitions, suggests a resolution to the quantum Zeno paradox. The theoretical limit of continuous observation is discussed.
Dynamical memory effects in correlated quantum channels
NASA Astrophysics Data System (ADS)
Addis, Carole; Karpat, Göktuǧ; Macchiavello, Chiara; Maniscalco, Sabrina
2016-09-01
Memory effects play a fundamental role in the study of the dynamics of open quantum systems. There exist two conceptually distinct notions of memory discussed for quantum channels in the literature. In quantum information theory quantum channels with memory are characterized by the existence of correlations between successive applications of the channel on a sequence of quantum systems. In open quantum systems theory memory effects arise dynamically during the time evolution of quantum systems and define non-Markovian dynamics. Here we relate and combine these two different concepts of memory. In particular, we study the interplay between correlations between multiple uses of quantum channels and non-Markovianity as nondivisibility of the t -parametrized family of channels defining the dynamical map.
Direct Measurement of Photon Recoil from a Levitated Nanoparticle
NASA Astrophysics Data System (ADS)
Jain, Vijay; Gieseler, Jan; Moritz, Clemens; Dellago, Christoph; Quidant, Romain; Novotny, Lukas
2016-06-01
The momentum transfer between a photon and an object defines a fundamental limit for the precision with which the object can be measured. If the object oscillates at a frequency Ω0 , this measurement backaction adds quanta ℏΩ0 to the oscillator's energy at a rate Γrecoil, a process called photon recoil heating, and sets bounds to coherence times in cavity optomechanical systems. Here, we use an optically levitated nanoparticle in ultrahigh vacuum to directly measure Γrecoil. By means of a phase-sensitive feedback scheme, we cool the harmonic motion of the nanoparticle from ambient to microkelvin temperatures and measure its reheating rate under the influence of the radiation field. The recoil heating rate is measured for different particle sizes and for different excitation powers, without the need for cavity optics or cryogenic environments. The measurements are in quantitative agreement with theoretical predictions and provide valuable guidance for the realization of quantum ground-state cooling protocols and the measurement of ultrasmall forces.
Direct Measurement of Photon Recoil from a Levitated Nanoparticle.
Jain, Vijay; Gieseler, Jan; Moritz, Clemens; Dellago, Christoph; Quidant, Romain; Novotny, Lukas
2016-06-17
The momentum transfer between a photon and an object defines a fundamental limit for the precision with which the object can be measured. If the object oscillates at a frequency Ω_{0}, this measurement backaction adds quanta ℏΩ_{0} to the oscillator's energy at a rate Γ_{recoil}, a process called photon recoil heating, and sets bounds to coherence times in cavity optomechanical systems. Here, we use an optically levitated nanoparticle in ultrahigh vacuum to directly measure Γ_{recoil}. By means of a phase-sensitive feedback scheme, we cool the harmonic motion of the nanoparticle from ambient to microkelvin temperatures and measure its reheating rate under the influence of the radiation field. The recoil heating rate is measured for different particle sizes and for different excitation powers, without the need for cavity optics or cryogenic environments. The measurements are in quantitative agreement with theoretical predictions and provide valuable guidance for the realization of quantum ground-state cooling protocols and the measurement of ultrasmall forces. PMID:27367388
Median recoil direction as a WIMP directional detection signal
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.
Thermal Effects on Quantum Sticking
NASA Astrophysics Data System (ADS)
Zhang, Yanting; Clougherty, Dennis
2012-02-01
Many-body effects on the threshold law of quantum sticking of a particle coupled to an ohmic bosonic bath are examined for finite temperature surfaces. Generalizing a variational mean-field methodootnotetextY. Zhang and D.P. Clougherty, arXiv:1012.4405 previously applied to zero temperature surfaces, we obtain an explicit expression for the sticking probability of a particle with incident energy E. We find that there is a critical particle energy below which the probability of its sticking to the surface discontinuously drops to zero. We show that this singularity, whose origin is rooted by analogy to the localization transition in the spin-boson model, is experimentally accessible for ultracold particles. We provide detailed numerical results for this effect.
Quantum effects in the understanding of consciousness.
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.
NASA Astrophysics Data System (ADS)
Henriksson, K. O. E.
2016-06-01
The number of point defects formed in spherical cementite and Cr23C6 inclusions embedded into ferrite (α-iron) has been studied and compared against cascades in pure versions of these materials (only ferrite, Fe3C, or Cr23C6 in a cell). Recoil energies between 100 eV and 3 keV and temperatures between 400 K and 1000 K were used. The overall tendency is that the number of point defects — such as antisites, vacancy and interstitials — increases with recoil energy and temperature. The radial distributions of defects indicate that the interface between inclusions and the host tend to amplify and restrict the defect formation to the inclusions themselves, when compared to cascades in pure ferrite and pure carbide cells.
Real measurements and the quantum Zeno effect
NASA Astrophysics Data System (ADS)
Ruseckas, Julius; Kaulakys, B.
2001-06-01
In 1977, Mishra and Sudarshan [J. Math. Phys. 18, 756 (1977)] showed that an unstable particle would never be found decayed while it was continuously observed. They called this effect the quantum Zeno effect (or paradox). Later it was realized that the frequent measurements could also accelerate the decay (quantum anti-Zeno effect). In this paper, we investigate the quantum Zeno effect using the definite model of the measurement. We take into account the finite duration and the finite accuracy of the measurement. A general equation for the jump probability during the measurement is derived. We find that the measurements can cause inhibition (quantum Zeno effect) or acceleration (quantum anti-Zeno effect) of the evolution, depending on the strength of the interaction with the measuring device and on the properties of the system. However, the evolution cannot be fully stopped.
Quantum Thermoelectric Effects on the Nanoscale
NASA Astrophysics Data System (ADS)
Bergfield, Justin; Stafford, Charles
2011-03-01
An exact expression for the heat current in a nanostructure coupled to multiple metallic electrodes is derived, including both electron-electron and electron-phonon interactions. We use this formalism to investigate quantum effects on the flow of charge and entropy, and find an enormous quantum enhancement of thermoelectric effects in the vicinity of higher-order interferences in the transmission spectrum of a nanoscale junction. A nonequilibrium quantum analysis of a single-molecule junction based on 3,3'-biphenyldithiol demonstrates a maximum operating efficiency of 27% of the Carnot limit. Nonlocal quantum corrections to thermoelectric transport coefficients in multiterminal geometries are predicted.
The quantum Hall effect helicity
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.
Deconvoluting nonaxial recoil in Coulomb explosion measurements of molecular axis alignment
NASA Astrophysics Data System (ADS)
Christensen, Lauge; Christiansen, Lars; Shepperson, Benjamin; Stapelfeldt, Henrik
2016-08-01
We report a quantitative study of the effect of nonaxial recoil during Coulomb explosion of laser-aligned molecules and introduce a method to remove the blurring caused by nonaxial recoil in the fragment-ion angular distributions. Simulations show that nonaxial recoil affects correlations between the emission directions of fragment ions differently from the effect caused by imperfect molecular alignment. The method, based on analysis of the correlation between the emission directions of the fragment ions from Coulomb explosion, is used to deconvolute the effect of nonaxial recoil from experimental fragment angular distributions. The deconvolution method is then applied to a number of experimental data sets to correct the degree of alignment for nonaxial recoil, to select optimal Coulomb explosion channels for probing molecular alignment, and to estimate the highest degree of alignment that can be observed from selected Coulomb explosion channels.
Maxwell-Garnett effective medium theory: Quantum nonlocal effects
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.
Effective scenario of loop quantum cosmology.
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.
The quantum Hall effects: Philosophical approach
NASA Astrophysics Data System (ADS)
Lederer, P.
2015-05-01
The Quantum Hall Effects offer a rich variety of theoretical and experimental advances. They provide interesting insights on such topics as gauge invariance, strong interactions in Condensed Matter physics, emergence of new paradigms. This paper focuses on some related philosophical questions. Various brands of positivism or agnosticism are confronted with the physics of the Quantum Hall Effects. Hacking's views on Scientific Realism, Chalmers' on Non-Figurative Realism are discussed. It is argued that the difficulties with those versions of realism may be resolved within a dialectical materialist approach. The latter is argued to provide a rational approach to the phenomena, theory and ontology of the Quantum Hall Effects.
A recoil separator for nuclear astrophysics SECAR
NASA Astrophysics Data System (ADS)
Berg, G. P. A.; Bardayan, D. W.; Blackmon, J. C.; Chipps, K. A.; Couder, M.; Greife, U.; Hager, U.; Montes, F.; Rehm, K. E.; Schatz, H.; Smith, M. S.; Wiescher, M.; Wrede, C.; Zeller, A.
2016-06-01
A recoil separator SECAR has been designed to study radiative capture reactions relevant for the astrophysical rp-process in inverse kinematics for the Facility for Rare Isotope Beams (FRIB). We describe the design, layout, and ion optics of the recoil separator and present the status of the project.
Missing Mass Recoiling Against the Charged D
Cain, Hillary
2003-09-05
This paper chronicles the investigation of a peak in the BaBar mass data set of mass recoiling against charged D*s. Our hypothesis is that the peak at 2620 MeV is a reflection of the D{sub s}* and {pi} system. Specifically, we explored the idea that the peak might be a reflection from the decay B {yields} D**{sup -} D*{sub s}{sup +} with the D**{sup -} {yields} D*{sup -} {pi}. Theoretically, when the D**{sup -} decays, the trajectory of the resulting {pi} will form an angle with the D*{sub s}{sup +}, and different angles impart difference masses to the system over a range of a GeV or so. If quantum mechanics dictates that their paths will form a particular angle more often than others, a peak would appear in the histogram of their collective mass. Using the Monte Carlo model of particle collision events, Anders Ryd's EVTGEN program, C++ code derived from GeneratorsQA, and PAW, we tested the hypothesis that the peak might be a reflection of the system, but found that this possible explanation could not account for the peak. No 2620 MeV peak appears in the histogram of the system mass. We therefore discount the hypothesis and conclude that some other reflection, statistical fluctuation, or particle is causing the peak.
NASA Astrophysics Data System (ADS)
Nakazato, Hiromichi; Namiki, Mikio; Pascazio, Saverio; Rauch, Helmut
1995-02-01
The limit of infinitely frequent measurements (continuous observation), yielding the quantum Zeno paradox, is critically analyzed and shown to be unphysical. A specific example involving neutron spin is considered and some practical estimates are given.
Quantum Hall effect in momentum space
NASA Astrophysics Data System (ADS)
Ozawa, Tomoki; Price, Hannah M.; Carusotto, Iacopo
2016-05-01
We theoretically discuss a momentum-space analog of the quantum Hall effect, which could be observed in topologically nontrivial lattice models subject to an external harmonic trapping potential. In our proposal, the Niu-Thouless-Wu formulation of the quantum Hall effect on a torus is realized in the toroidally shaped Brillouin zone. In this analogy, the position of the trap center in real space controls the magnetic fluxes that are inserted through the holes of the torus in momentum space. We illustrate the momentum-space quantum Hall effect with the noninteracting trapped Harper-Hofstadter model, for which we numerically demonstrate how this effect manifests itself in experimental observables. Extension to the interacting trapped Harper-Hofstadter model is also briefly considered. We finally discuss possible experimental platforms where our proposal for the momentum-space quantum Hall effect could be realized.
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.
Counterfactual Measurements and the Quantum Zeno Effect
NASA Astrophysics Data System (ADS)
Russo, Onofrio; Jiang, Liang
2014-03-01
The apparent paradoxical paradigm of an interaction free measurement (counterfactual measurement) of the presence of a classical or quantum object without any scattering or absorption of photons is considered in light of the quantum Zeno effect. From one perspective, the counterfactual measurement in principle is consistent with minimizing the interaction between the object and the photon. However, the quantum Zeno effect mandates that repeated interactions with photons (although weakly coupled) are required and necessary to inhibit the coherent evolution of the state of the system. We consider and appraise these seemingly conflicting concepts.
Epitaxial silicide formation on recoil-implanted substrates
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.
Quantum hall effect at low magnetic fields
Huckestein
2000-04-01
The temperature and scale dependence of resistivities in the standard scaling theory of the integer quantum Hall effect is discussed. It is shown that recent experiments, claiming to observe a discrepancy with the global phase diagram of the quantum Hall effect, are in fact in agreement with the standard theory. The apparent low-field transition observed in the experiments is identified as a crossover due to weak localization and a strong reduction of the conductivity when Landau quantization becomes dominant.
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.
Quantum Zeno effect in optical fibers
NASA Astrophysics Data System (ADS)
Yamane, K.; Ito, M.; Kitano, M.
2001-06-01
The quantum Zeno effect is a paradoxical phenomenon where the inhibition of transition or the guidance of system is realized with no losses in spite of the use of dissipative processes. It is universal and not limited to quantum systems. In this paper as a classical example we report the quantum Zeno effect in optical fibers. The fibers are spliced with transverse offset at fiber joints, and incident light transmits in the series of fibers. There are two kinds of light propagation modes in optical fibers - wave and ray modes. We find that the quantum Zeno effect appears only in the former mode and light is guided without power losses in the limit of the number of fiber joints N→∞ despite of the discontinuity at joints.
Locality and universality of quantum memory effects.
Liu, B-H; Wißmann, 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
Locality and universality of quantum memory effects
NASA Astrophysics Data System (ADS)
Liu, B.-H.; Wißmann, S.; Hu, X.-M.; Zhang, C.; Huang, Y.-F.; Li, C.-F.; Guo, G.-C.; Karlsson, A.; Piilo, J.; Breuer, H.-P.
2014-09-01
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.
Doppler- and recoil-free laser excitation of Rydberg states via three-photon transitions
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.
Gas powered fluid gun with recoil mitigation
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.
Gas powered fluid gun with recoil mitigation
Grubelich, Mark C.; Yonas, Gerold
2016-03-01
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.
Coherent quantum effects through dispersive bosonic media
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.
NASA Astrophysics Data System (ADS)
Trukhanova, M., Iv.
2013-11-01
In this paper, we explain a magneto quantum hydrodynamics (MQHD) method for the study of the quantum evolution of a system of spinning fermions in an external electromagnetic field. The fundamental equations of microscopic quantum hydrodynamics (the momentum balance equation and the magnetic moment density equation) are derived from the many-particle microscopic Schrödinger equation with a spin-spin and Coulomb modified Hamiltonian. Using the developed approach, an extended vorticity evolution equation for the quantum spinning plasma is derived. The effects of the new spin forces and spin-spin interaction contributions on the motion of fermions, the evolution of the magnetic moment density, and vorticity generation are predicted. The influence of the intrinsic spin of electrons on whistler mode turbulence is investigated. The results can be used for theoretical studies of spinning many-particle systems, especially dense quantum plasmas in compact astrophysical objects, plasmas in semiconductors, and micro-mechanical systems, in quantum X-ray free-electron lasers.
The Integer and Fractional Quantum Hall Effects.
NASA Astrophysics Data System (ADS)
Usher, Alan
Available from UMI in association with The British Library. Requires signed TDF. This thesis reports investigations of the electrical conductivity of two-dimensional electron systems in high magnetic fields. Studies of the activated longitudinal conductivity associated with the integer quantum Hall effect reveal a large enhancement of the electronic g-factor, caused by the electron-electron interaction. A similar enhancement is observed in the Landau level separation. The magnetic field dependences of both effects are influenced by sample disorder. The activation data are analysed using three models for the shape of the extended state regions of disorder -broadened Landau levels. Only a small fraction of the electrons are found to occupy extended states. Values of the minimum metallic conductivity of electrons in broadened Landau levels are sample- and electron concentration-dependent. The fractional quantum Hall effect is a property of electrons in an incompressible quantum fluid state. The highest quality samples with low electron concentrations exhibit the effect in the manner predicted by simple theories involving spinless electrons. However, the influence of spin becomes apparent at higher electron concentrations, and in tilted field experiments. The effects of disorder are evident in measurements of the quasiparticle energy gap associated with the fractional quantum Hall effect. The experimental gap energies reported in this thesis are considerably smaller than those of theoretical studies, and they tend to zero at a non-zero magnetic field threshold. Simple theories predict that the fractional quantum Hall effect occurs only at odd denominator fractional occupancies. This thesis reports the first observations of the even denominator fractional quantum Hall effect. Persistent photoconductivity is a useful tool for increasing the concentration of two-dimensional electrons in GaAs-AlGaAs heterojunctions. A new photodeexcitation effect is reported, and possible
Quantum fluid model of coherent stimulated radiation by a dense relativistic cold electron beam
Monteiro, L. F.; Serbeto, A.; Tsui, K. H.; Mendonça, J. T.; Galvão, R. M. O.
2013-07-15
Using a quantum fluid model, the linear dispersion relation for FEL pumped by a short wavelength laser wiggler is deduced. Subsequently, a new quantum corrected resonance condition is obtained. It is shown that, in the limit of low energy electron beam and low frequency pump, the quantum recoil effect can be neglected, recovering the classical FEL resonance condition, k{sub s}=4k{sub w}γ{sup 2}. On the other hand, for short wavelength and high energy electron beam, the quantum recoil effect becomes strong and the resonance condition turns into k{sub s}=2√(k{sub w}/λ{sub c})γ{sup 3/2}, with λ{sub c} being the reduced Compton wavelength. As a result, a set of nonlinear coupled equations, which describes the quantum FEL dynamics as a three-wave interaction, is obtained. Neglecting wave propagation effects, this set of equations is solved numerically and results are presented.
Retention studies of recoiling daughter nuclides of 225Ac in polymer vesicles.
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
Retention studies of recoiling daughter nuclides of 225Ac in polymer vesicles.
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.
Quantum Hall effect in semiconductor systems with quantum dots and antidots
Beltukov, Ya. M.; Greshnov, A. A.
2015-04-15
The integer quantum Hall effect in systems of semiconductor quantum dots and antidots is studied theoretically as a factor of temperature. It is established that the conditions for carrier localization in quantum-dot systems favor the observation of the quantum Hall effect at higher temperatures than in quantum-well systems. The obtained numerical results show that the fundamental plateau corresponding to the transition between the ground and first excited Landau levels can be retained up to a temperature of T ∼ 50 K, which is an order of magnitude higher than in the case of quantum wells. Implementation of the quantum Hall effect at such temperatures requires quantum-dot systems with controllable characteristics, including the optimal size and concentration and moderate geometrical and composition fluctuations. In addition, ordered arrangement is desirable, hence quantum antidots are preferable.
Hierarchical nature of the quantum Hall effects.
Bonderson, Parsa
2012-02-10
I demonstrate that the wave function for a ν=n+ν[over ˜] quantum Hall state with Landau levels 0,1,…,n-1 filled and a filling fraction ν[over ˜] quantum Hall state with 0<ν[over ˜]≤1 in the nth Landau level can be obtained hierarchically from the ν=n state by introducing quasielectrons which are then projected into the (conjugate of the) ν[over ˜] state. In particular, the ν[over ˜]=1 case produces the filled Landau level wave functions hierarchically, thus establishing the hierarchical nature of the integer quantum Hall states. It follows that the composite fermion description of fractional quantum Hall states fits within the hierarchy theory of the fractional quantum Hall effect. I also demonstrate this directly by generating the composite fermion ground-state wave functions via application of the hierarchy construction to fractional quantum Hall states, starting from the ν=1/m Laughlin states.
Berkeley Experiments on Superfluid Macroscopic Quantum Effects
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.
Spectral effects in quantum teleportation
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.
Spectral Effects in Quantum Teleportation
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.
The Compton effect: Transition to quantum mechanics
NASA Astrophysics Data System (ADS)
Stuewer, R. H.
2000-11-01
The discovery of the Compton effect at the end of 1922 was a decisive event in the transition to the new quantum mechanics of 1925-1926 because it stimulated physicists to examine anew the fundamental problem of the interaction between radiation and matter. I first discuss Albert Einstein's light-quantum hypothesis of 1905 and why physicists greeted it with extreme skepticism, despite Robert A. Millikan's confirmation of Einstein's equation of the photoelectric effect in 1915. I then follow in some detail the experimental and theoretical research program that Arthur Holly Compton pursued between 1916 and 1922 at the University of Minnesota, the Westinghouse Lamp Company, the Cavendish Laboratory, and Washington University that culminated in his discovery of the Compton effect. Surprisingly, Compton was not influenced directly by Einstein's light-quantum hypothesis, in contrast to Peter Debye and H.A. Kramers, who discovered the quantum theory of scattering independently. I close by discussing the most significant response to that discovery, the Bohr-Kramers-Slater theory of 1924, its experimental refutation, and its influence on the emerging new quantum mechanics.
Spreading and recoil of a surfactant-containing water drop on glass-supported alcohol films.
Chowdhury, Devasish; Sarkar, Surya Protim; Kalita, Dipankar; Sarma, Tridib Kumar; Paul, Anumita; Chattopadhyay, Arun
2004-02-17
In this paper we report the experimental observation of spreading and recoil of surfactant-containing water drops on various alcohol films supported on glass slides. The time evolution of spreading and recoil behavior was recorded by placing a web camera above the drop. We observed that the drop spread the fastest on CH3OH, followed by C2H5OH, and the slowest on i-PrOH. On the other hand, the recoil behavior was just the opposite. The drop recoiled the slowest on CH3OH and fastest on i-PrOH, while it recoiled in an intermediate time on C2H5OH. In addition, concentration of surfactant in the drop played a prominent role in the spreading and recoil time of the drop, with higher surfactant concentration making the drop spread and recoil faster. The time evolution of spreading velocity of the drop on different alcohol films at various surfactant concentrations occurred with a Gaussian distribution and the peak velocity was reached earliest on CH3OH followed by C2H5OH, while on i-PrOH it took the longest time. The recoil behavior was similar. The variation of velocity as a function of radius exhibited oscillatory behavior, indicating the existence of an interfacial phenomenon. We also report the observation that spreading of the drop occurred without observable fingering instability. Further, we observed by Fourier transform infrared (FTIR) spectroscopic measurements that the drop had mixed with the alcohol films as it spread. Miscibility of the alcohol in the film with the drop, alcohol evaporation cooling-induced temperature gradient, and Marangoni effect probably play important roles in the spreading and recoil behavior of the drop.
Gravitational Waves in Effective Quantum Gravity
NASA Astrophysics Data System (ADS)
Calmet, Xavier; Kuntz, Iberê; Mohapatra, Sonali
2016-08-01
In this short paper we investigate quantum gravitational effects on Einstein's equations using Effective Field Theory techniques. We consider the leading order quantum gravitational correction to the wave equation. Besides the usual massless mode, we find a pair of modes with complex masses. These massive particles have a width and could thus lead to a damping of gravitational waves if excited in violent astrophysical processes producing gravitational waves such as e.g. black hole mergers. We discuss the consequences for gravitational wave events such as GW 150914 recently observed by the Advanced LIGO collaboration.
The effects of nonextensivity on quantum dissipation
Choi, Jeong Ryeol
2014-01-01
Nonextensive dynamics for a quantum dissipative system described by a Caldirola-Kanai (CK) Hamiltonian is investigated in SU(1,1) coherent states. To see the effects of nonextensivity, the system is generalized through a modification fulfilled by replacing the ordinary exponential function in the standard CK Hamiltonian with the q-exponential function. We confirmed that the time behavior of the system is somewhat different depending on the value of q which is the degree of nonextensivity. The effects of q on quantum energy dissipation and other parameters are illustrated and discussed in detail. PMID:24468727
Quantum Plasma Effects in the Classical Regime
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.
Developments in the quantum Hall effect.
von Klitzing, Klaus
2005-09-15
The most important applications of the quantum Hall effect (QHE) are in the field of metrology. The observed quantization of the resistance is primarily used for the reproduction of the SI unit ohm, but is also important for high precision measurements of both the fine structure constant and the Planck constant. Some current QHE research areas include the analysis of new electron-electron correlation phenomena and the development of a more complete microscopic picture of this quantum effect. Recently, scanning force microscopy (SFM) of the potential distribution in QHE devices has been used to enhance the microscopic understanding of current flow in quantum Hall systems. This confirms the importance of the theoretically predicted stripes of compressible and incompressible electronic states close to the boundary of the QHE devices.
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
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.
Spallation recoil and age of presolar grains in meteorites
NASA Astrophysics Data System (ADS)
Ott, U.; Begemann, F.
2000-01-01
We have determined the recoil losses from silicon carbide grain size fractions of spallation neon produced by irradiation with 1.6 GeV protons. During the irradiation the SiC grains were dispersed in paraffin wax in order to avoid re-implantation into neighboring grains. Analysis for spallogenic 21Ne of grain size separates in the size range 0.3 μm to 6 μm and comparison with the 22Na activity of the SiC+paraffin mixture indicates an effective recoil range of 2-3 μm with no apparent effect from acid treatments such as routinely used in the isolation of meteoritic SiC grains. Our results indicate that the majority of presolar SiC grains in primitive meteorites, which are ~μm-sized, will have lost essentially all spallogenic Ne produced by cosmic ray interaction in the interstellar medium. This argues against the validity of previously published presolar ages of Murchison SiC (~10 to ~130 Ma; increasing with grain size; Lewis et al., 1994), where recoil losses had been based on calculated recoil energies. It is argued that the observed variations in meteoritic SiC grain size fractions of 21Ne/22Ne ratios are more likely due to the effects of nucleosynthesis in the He burning shell of the parent AGB stars which imposes new boundary conditions on nuclear parameters and stellar models. It is suggested that spallation-Xe produced on the abundant Ba and REE in presolar SiC, rather than spallogenic Ne, may be a promising approach to the presolar age problem. There is a hint in the currently available Xe data (Lewis et al., 1994) that the large (>1 μm) grains may be younger than the smaller (<1 μm) ones.
Quantum Anomalous Hall Effect in Hg_1-yMn_yTe Quantum Wells
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.
Unconventional integer quantum Hall effect in graphene.
Gusynin, V P; Sharapov, S G
2005-09-30
Monolayer graphite films, or graphene, have quasiparticle excitations that can be described by (2+1)-dimensional Dirac theory. We demonstrate that this produces an unconventional form of the quantized Hall conductivity sigma(xy) = -(2e2/h)(2n+1) with n = 0, 1, ..., which notably distinguishes graphene from other materials where the integer quantum Hall effect was observed. This unconventional quantization is caused by the quantum anomaly of the n=0 Landau level and was discovered in recent experiments on ultrathin graphite films.
A programmable quantum current standard from the Josephson and the quantum Hall effects
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.
Significant Quantum Effects in Hydrogen Activation
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 H_{2} up to 190 K and for D_{2} up to 140 K. Kinetic Monte Carlo simulations indicate that the effective barrier to H_{2} dissociation is so low that hydrogen uptake on the surface is limited merely by thermodynamics, whereas the D_{2} 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.
Significant Quantum Effects in Hydrogen Activation
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
A Double Scattering Analytical Model For Elastic Recoil Detection Analysis
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.
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.
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.
Stochasticity effects in quantum radiation reaction.
Neitz, N; Di Piazza, A
2013-08-01
When an ultrarelativistic electron beam collides with a sufficiently intense laser pulse, radiation-reaction effects can strongly alter the beam dynamics. In the realm of classical electrodynamics, radiation reaction has a beneficial effect on the electron beam as it tends to reduce its energy spread. Here we show that when quantum effects become important, radiation reaction induces the opposite effect; i.e., the energy distribution of the electron beam spreads out after interacting with the laser pulse. We identify the physical origin of this opposite tendency in the intrinsic stochasticity of photon emission, which becomes substantial in the quantum regime. Our numerical simulations indicate that the predicted effects of the stochasticity can be measured already with presently available lasers and electron accelerators.
Effective equilibrium theory of nonequilibrium quantum transport
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.
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.
Quantum anomalous Hall effect with higher plateaus.
Wang, Jing; Lian, Biao; Zhang, Haijun; Xu, Yong; Zhang, Shou-Cheng
2013-09-27
The quantum anomalous Hall (QAH) effect in magnetic topological insulators is driven by the combination of spontaneous magnetic moments and spin-orbit coupling. Its recent experimental discovery raises the question if higher plateaus can also be realized. Here, we present a general theory for a QAH effect with higher Chern numbers and show by first-principles calculations that a thin film magnetic topological insulator of Cr-doped Bi2(Se,Te)3 is a candidate for the C=2 QAH insulator. Remarkably, whereas a higher magnetic field leads to lower Hall conductance plateaus in the integer quantum Hall effect, a higher magnetic moment leads to higher Hall conductance plateaus in the QAH effect.
Elastic recoil detection analysis for large recoil angles (LA-ERDA)
NASA Astrophysics Data System (ADS)
Bogdanović Radović, I.; Steinbauer, E.; Benka, O.
2000-09-01
In this paper, elastic recoil detection (ERD) measurements at recoil angle of 60° using ion-induced electron emission (IEE) for particle identification are presented. In our IEE system for particle identification, recoiled target atoms and scattered projectiles penetrate a set of thin carbon foils before their energy is analyzed in a solid state detector. Particle identification is based on the fact that the total number of electrons emitted from the foils depends on the particle nuclear charge. This method is characterized by its low minimum detectable energy, which stimulated us to study ERDA at 60°. Due to collision kinematics and due to the angular dependence of the scattering cross-sections, it is expected that the sensitivity can be significantly improved. In this work, the detection efficiency of the IEE particle identification system for H recoils at energies below 1 MeV was determined. LA-ERDA measurements were performed with 4He and 12C projectiles using two different types of samples with a well-known amount and depth distribution of H atoms near the surface. Sample 1 consisted of a 50 μg/cm 2 melamine layer evaporated on a flat Si substrate, sample 2 was a Si wafer with implanted H. Sensitivity and depth resolution were measured using LA-ERDA with a recoil angle of 60° and ERDA with recoil angles of 30° and 45°. The results for different recoil geometries and projectiles are discussed and compared with theoretical predictions.
Nonmonotonicity in the quantum-classical transition: chaos induced by quantum effects.
Kapulkin, Arie; Pattanayak, Arjendu K
2008-08-15
The classical-quantum transition for chaotic systems is understood to be accompanied by the suppression of chaotic effects as the relative variant Planck's over 2pi is increased. We show evidence to the contrary in the behavior of the quantum trajectory dynamics of a dissipative quantum chaotic system, the double-well Duffing oscillator. The classical limit in the case considered has regular behavior, but as the effective variant Planck's over 2pi is increased we see chaotic behavior. This chaos then disappears deeper into the quantum regime, which means that the quantum-classical transition in this case is nonmonotonic in variant Planck's over 2pi. PMID:18764537
Quantum gravity effects in the Kerr spacetime
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.
Recoil separator ERNA: ion beam specifications
NASA Astrophysics Data System (ADS)
Rogalla, D.; Aliotta, M.; Barnes, C. A.; Campajola, L.; D'Onofrio, A.; Fritz, E.; Gialanella, L.; Greife, U.; Imbriani, G.; Ordine, A.; Ossmann, J.; Roca, V.; Rolfs, C.; Romano, M.; Sabbarese, C.; Schürmann, D.; Schümann, F.; Strieder, F.; Theis, S.; Terrasi, F.; Trautvetter, H. P.
For improved measurements of the key astrophysical reaction 12C(α,γ)16O in inverted kinematics, a recoil separator ERNA is being developed at the 4 MV Dynamitron tandem accelerator in Bochum to detect directly the 16O recoils with about 50% efficiency. Calculations of the ion beam optics including all filtering and focusing elements of ERNA are presented. Since the 12C projectiles and the 16O recoils have essentially the same momentum, and since the 12C ion beam emerging from the accelerator passes through a momentum filter (analysing magnet), the 12C ion beam must be as free as possible from 16O contamination for ERNA to succeed. In the present work, the 16O contamination was reduced from a level of 1 × 10-11 to a level below 2 × 10-29 by the installation of Wien filters both before and after the analysing magnet. The measurement of these and other beam specifications involved other parts of the final ERNA layout - sequentially a Wien filter, a 60˚ dipole magnet, another Wien filter, and a ΔE-E telescope. The setup led to a measured suppression factor of 5 × 10-18 for the 12C ion beam. The experiments also indicate that an almost free choice of the charge state for the 16O recoils is possible in the separator.
Proton recoil scintillator neutron rem meter
Olsher, Richard H.; Seagraves, David T.
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.
Multipole expansion in the quantum hall effect
NASA Astrophysics Data System (ADS)
Cappelli, Andrea; Randellini, Enrico
2016-03-01
The effective action for low-energy excitations of Laughlin's states is obtained by systematic expansion in inverse powers of the magnetic field. It is based on the W- infinity symmetry of quantum incompressible fluids and the associated higher-spin fields. Besides reproducing the Wen and Wen-Zee actions and the Hall viscosity, this approach further indicates that the low-energy excitations are extended objects with dipolar and multipolar moments.
Effective Dynamics of Disordered Quantum Systems
NASA Astrophysics Data System (ADS)
Kropf, Chahan M.; Gneiting, Clemens; Buchleitner, Andreas
2016-07-01
We derive general evolution equations describing the ensemble-average quantum dynamics generated by disordered Hamiltonians. The disorder average affects the coherence of the evolution and can be accounted for by suitably tailored effective coupling agents and associated rates that encode the specific statistical properties of the Hamiltonian's eigenvectors and eigenvalues, respectively. Spectral disorder and isotropically disordered eigenvector distributions are considered as paradigmatic test cases.
Topological effects in quantum mechanics
Peshkin, M.; Lipkin, H.J. |
1995-08-01
We completed our analysis of experiments, some completed, some planned, and some only conceptual at present, that purport to demonstrate new kinds of non-local and topological effects in the interaction of a neutron with an external electromagnetic field. In the Aharonov-Casher effect (AC), the neutron interacts with an electric field and in the Scalar Aharonov-Bohm effect (SAB) the neutron interacts with a magnetic field. In both cases, the geometry can be arranged so that there is no force on the neutron but an interference experiment nevertheless finds a phase shift proportional to the applied field and to the neutron`s magnetic moment. Previously, we showed that the accepted interpretation of these phenomena as topological effects due to a non-local interaction between the neutron and the electromagnetic field is incorrect. Both AC and SAB follow from local torques on the neutron whose expectation values vanish at every instant but which have non-vanishing effect on the measurable spin-correlation variables S(t) = (1/2) [{sigma}{sub x}{sigma}{sub x}(t) + {sigma}{sub y}(0){sigma}{sub y}(t) + h.c.] and V(t) = [{sigma}{sub x}(0){sigma}{sub y}(t) - {sigma}{sub y}(0){sigma}{sub x}(t) + h.c.]. We have now completed this work by observing that a criterion often used for identifying a topological effect, energy independence of the phase shift between two arms of an interferometer, is only a necessary condition, and by describing a phase shifter which obeys the energy-independence condition but whose interaction with the neutron is neither topological nor even non-local.
Quantum nonlocal effects on optical properties of spherical nanoparticles
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.
Quantum Gravitational Effects and Grand Unification
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.
Nontrivial quantum and quantum-like effects in biosystems: Unsolved questions and paradoxes.
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
Nontrivial quantum and quantum-like effects in biosystems: Unsolved questions and paradoxes.
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.
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.
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.
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; 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.
Angular dependence of recoil proton polarization in high-energy \\gamma d \\to p n
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.
Casimir effect, quantum fluctuations and related topics
NASA Astrophysics Data System (ADS)
Hushwater, Velvel Shaia
Casimir forces are the very long-range (retarded) forces between electrically neutral systems. Such forces may be thought of as arising from the quantum fluctuations of the electromagnetic field. Contrary to popular opinion such forces need not be attractive. After giving a foundation of the method of the change in the 'zero-point energy' we show how other methods to compute Casimir forces follow from it. We consider the repulsion between electric and magnetic dipoles induced by vacuum fluctuations of electromagnetic field. The calculation are made by the use of the Heisenberg picture operators and by the stochastic electrodynamics approach. We present a purely geometrical proof of the image method, and use it to discuss the Casimir interaction between an atom and a plate. We study the Casimir repulsion between a perfectly conducting and an infinitely permeable plate with the radiation pressure approach. This example illustrates how a repulsive force arises as a consequence of the redistribution of vacuum-field modes corresponding to specific boundary conditions. We show that result is independent of a cutoff function. Discussing the connection with perturbation theory, we prove the negativity of the leading order shift in the ground state. The Casimir effect supports the reality of the 'zero- point energy.' To clarify this we present a novel approach to quantum theory, based on the principle of the quantization of the ensemble-averaged action variable. This quantization leads to the probabilistic description of coordinates and momentum as random variables, which satisfy the uncertainty relation. Using such variables we show that the 'quantum momentum function' must satisfy the Riccati differential equation, which can be converted to the Schrodinger equation for the Ψ function. We derive also the form of basic operators and the rule for probabilities in quantum mechanics. We show that the approach leads to a simple interpretation of gauge invariance, and discuss
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.
BlackMax: A black-hole event generator with rotation, recoil, split branes, and brane tension
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.
A curved detection-slit to improve ERD (Elastic Recoil Detection) energy/depth resolution
Brice, D.K.; Doyle, B.L.
1989-01-01
Recoil atoms detected in Elastic Recoil Detection (ERD) experiments emerge from an initial collision area along cones of constant energy due to the cylindrical symmetry of the elastic scattering cross section. The constant energy cones therefore intercept planar slit plates placed before the detectors in conic sections. For ease of fabrication slits are typically configured as long narrow rectangles, and as a result energy resolution is adversely affected. It has been shown that the kinematic broadening caused by using rectangular slits is minimized when L = 2 (W z tan/Theta//sub recoil/)/sup 1/2/ where W is the slit width, L is the slit length, z is the slit-target distance and /Theta//sub recoil/ is the lab-frame recoil angle. The improved energy resolution which results when rectangular slits are replaced by appropriate curved slits is examined here. Formulas are given for the conic sections associated with the curved slits as a function of experimental geometry. When slit dimensions are small compared with the full extent of the conic section slit geometry can be accurately approximated as the arc of a circle with radius R/sub c/ = z tan/Theta//sub recoil/. Energy loss effects on the resolution are also accounted for in our treatment. The use of curved slits with L = 4 (W z tan/Theta//sub recoil/)/sup 1/2/ is shown to improve kinematic broadening by /approximately/50% as compared to optimized rectangular slits of the same area. 2 refs., 5 figs.
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
Guterding, Daniel; Jeschke, Harald O; Valentí, Roser
2016-01-01
Electronic states with non-trivial topology host a number of novel phenomena with potential for revolutionizing information technology. The quantum anomalous Hall effect provides spin-polarized dissipation-free transport of electrons, while the quantum spin Hall effect in combination with superconductivity has been proposed as the basis for realizing decoherence-free quantum computing. We introduce a new strategy for realizing these effects, namely by hole and electron doping kagome lattice Mott insulators through, for instance, chemical substitution. As an example, we apply this new approach to the natural mineral herbertsmithite. We prove the feasibility of the proposed modifications by performing ab-initio density functional theory calculations and demonstrate the occurrence of the predicted effects using realistic models. Our results herald a new family of quantum anomalous Hall and quantum spin Hall insulators at affordable energy/temperature scales based on kagome lattices of transition metal ions. PMID:27185665
NASA Astrophysics Data System (ADS)
Guterding, Daniel; Jeschke, Harald O.; Valentí, Roser
2016-05-01
Electronic states with non-trivial topology host a number of novel phenomena with potential for revolutionizing information technology. The quantum anomalous Hall effect provides spin-polarized dissipation-free transport of electrons, while the quantum spin Hall effect in combination with superconductivity has been proposed as the basis for realizing decoherence-free quantum computing. We introduce a new strategy for realizing these effects, namely by hole and electron doping kagome lattice Mott insulators through, for instance, chemical substitution. As an example, we apply this new approach to the natural mineral herbertsmithite. We prove the feasibility of the proposed modifications by performing ab-initio density functional theory calculations and demonstrate the occurrence of the predicted effects using realistic models. Our results herald a new family of quantum anomalous Hall and quantum spin Hall insulators at affordable energy/temperature scales based on kagome lattices of transition metal ions.
Guterding, Daniel; Jeschke, Harald O.; Valentí, Roser
2016-01-01
Electronic states with non-trivial topology host a number of novel phenomena with potential for revolutionizing information technology. The quantum anomalous Hall effect provides spin-polarized dissipation-free transport of electrons, while the quantum spin Hall effect in combination with superconductivity has been proposed as the basis for realizing decoherence-free quantum computing. We introduce a new strategy for realizing these effects, namely by hole and electron doping kagome lattice Mott insulators through, for instance, chemical substitution. As an example, we apply this new approach to the natural mineral herbertsmithite. We prove the feasibility of the proposed modifications by performing ab-initio density functional theory calculations and demonstrate the occurrence of the predicted effects using realistic models. Our results herald a new family of quantum anomalous Hall and quantum spin Hall insulators at affordable energy/temperature scales based on kagome lattices of transition metal ions. PMID:27185665
Guterding, Daniel; Jeschke, Harald O; Valentí, Roser
2016-05-17
Electronic states with non-trivial topology host a number of novel phenomena with potential for revolutionizing information technology. The quantum anomalous Hall effect provides spin-polarized dissipation-free transport of electrons, while the quantum spin Hall effect in combination with superconductivity has been proposed as the basis for realizing decoherence-free quantum computing. We introduce a new strategy for realizing these effects, namely by hole and electron doping kagome lattice Mott insulators through, for instance, chemical substitution. As an example, we apply this new approach to the natural mineral herbertsmithite. We prove the feasibility of the proposed modifications by performing ab-initio density functional theory calculations and demonstrate the occurrence of the predicted effects using realistic models. Our results herald a new family of quantum anomalous Hall and quantum spin Hall insulators at affordable energy/temperature scales based on kagome lattices of transition metal ions.
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.
Non-Markovian effect on the quantum discord
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.
Approximate inclusion of quantum effects in transition path sampling
Antoniou, Dimitri; Schwartz, Steven D.
2009-01-01
We propose a method for incorporating nuclear quantum effects in transition path sampling studies of systems that consist of a few degrees of freedom that must be treated quantum mechanically, while the rest are classical-like. We used the normal mode centroid method to describe the quantum subsystem, which is a method that is not CPU intensive but still reasonably accurate. We applied this mixed centroid∕classical transition path sampling method to a model system that has nontrivial quantum behavior, and showed that it can capture the correct quantum dynamical features. PMID:20001028
Quantum revivals and magnetization tunneling in effective spin systems
NASA Astrophysics Data System (ADS)
Krizanac, M.; Altwein, D.; Vedmedenko, E. Y.; Wiesendanger, R.
2016-03-01
Quantum mechanical objects or nano-objects have been proposed as bits for information storage. While time-averaged properties of magnetic, quantum-mechanical particles have been extensively studied experimentally and theoretically, experimental investigations of the real time evolution of magnetization in the quantum regime were not possible until recent developments in pump-probe techniques. Here we investigate the quantum dynamics of effective spin systems by means of analytical and numerical treatments. Particular attention is paid to the quantum revival time and its relation to the magnetization tunneling. The quantum revival time has been initially defined as the recurrence time of a total wave-function. Here we show that the quantum revivals of wave-functions and expectation values in spin systems may be quite different which gives rise to a more sophisticated definition of the quantum revival within the realm of experimental research. Particularly, the revival times for integer spins coincide which is not the case for half-integer spins. Furthermore, the quantum revival is found to be shortest for integer ratios between the on-site anisotropy and an external magnetic field paving the way to novel methods of anisotropy measurements. We show that the quantum tunneling of magnetization at avoided level crossing is coherent to the quantum revival time of expectation values, leading to a connection between these two fundamental properties of quantum mechanical spins.
Quantum dissipative effect of one dimension coupled anharmonic oscillator
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.
On the Effect of Quantum Noise in a Quantum-Relativistic Prisoner's Dilemma Cellular Automaton
NASA Astrophysics Data System (ADS)
Alonso-Sanz, Ramón; Situ, Haozhen
2016-09-01
The disrupting effect of quantum noise on the dynamics of a spatial quantum relativistic formulation of the iterated prisoner's dilemma game with variable entangling is studied in this work. The game is played in the cellular automata manner, i.e., with local and synchronous interaction. The game is assessed in fair and unfair contests.
Medium modifications with recoil polarization
Brand, J.F.J. van den; Ent, R.
1994-04-01
The authors show that the virtual Compton scattering process allows for a precise study of the off-shell electron-nucleon vertex. In a separable model, they show the sensitivity to new unconstrained structure functions of the nucleon, beyond the usual Dirac and Pauli form factors. In addition, they show the sensitivity to bound nucleon form factors using the reaction 4He({rvec e},e{prime},{rvec p}){sup 3}H. A nucleon embedded in a nucleus represents a complex system. Firstly, the bound nucleon is necessarily off-shell and in principle a complete understanding of the dynamical structure of the nucleon is required in order to calculate its off-shell electromagnetic interaction. Secondly, one faces the possibility of genuine medium effects, such as for example quark-exchange contributions. Furthermore, the electromagnetic coupling to the bound nucleon is dependent on the nuclear dynamics through the self-energy of the nucleon in the nuclear medium.
Low frequency hybrid instability in quantum magneto semiconductor plasmas
NASA Astrophysics Data System (ADS)
Rasheed, A.; Jamil, M.; Areeb, F.; Siddique, M.; Salimullah, M.
2016-05-01
The excitation of electrostatic, comparatively low frequency, lower-hybrid waves (LHWs) induced by electron beam in semiconductor plasma is examined using a quantum hydrodynamic model. Various quantum effects are taken into account including the recoil effect, Fermi degenerate pressure, and exchange-correlation potential. The effects of different parameters like the electron-to-hole number density ratio, scaled electron beam temperature and streaming speed, propagation angle and cyclotron frequency over the growth, and phase speed of LHWs are investigated. It is noticed that an increase in the electron number density and streaming speed enhance the instability. Similar effects are observed on decreasing the propagation angle with magnetic field.
Guiding effect of quantum wells in semiconductor lasers
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)
Fractional quantum Hall effect in a tilted magnetic field
NASA Astrophysics Data System (ADS)
Papić, Z.
2013-06-01
We discuss the orbital effect of a tilted magnetic field on the quantum Hall effect in parabolic quantum wells. Many-body states realized at the fractional (1)/(3) and (1)/(2) filling of the second electronic subband are studied using finite-size exact diagonalization. In both cases, we obtain the phase diagram consisting of a fractional quantum Hall fluid phase that persists for moderate tilts, and eventually undergoes a direct transition to the stripe phase. It is shown that tilting of the field probes the geometrical degree of freedom of fractional quantum Hall fluids, and can be partly related to the effect of band-mass anisotropy.
Covariant effective action for loop quantum cosmology a la Palatini
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.
The Theory of the Quantum Hall Effect
NASA Astrophysics Data System (ADS)
Shrivastava, Keshav N.
2008-05-01
Laughlin's theory of fractional charges is worked out in detail for small charges from 1/3 till 1/101. There is a small deviation between computed values and those obtained from the closed form expression. The ground state energy crosses that of the charge-density waves. We develop a theory of fractional charges by using the quantum mechanics of angular momentum. We find that fractional charges can be expressed in terms of spin and the values of charges 0, 1, 1/3, 2/3, 2/5, 3/5, …, are produced. The angular momenta eigen values when subjected to flux quantization, yield plateaus of energies which are independent of the magnetic field. In this way we are able to predict that charges of ±2e, ±6e, ±10e, ±14e, …, are produced. The higher order term in the flux quantization also produces quasiparticles of charges of ±4e. These calculated values of the charges are the same as those found in the experimental data of quantum Hall effect in graphene, which is a mono-atomic layer of carbon. Since the charge of the quasiparticles appears in the resistivity and there is a strong need of the electron spin to predict these charges, spin-charge coupling occurs in a natural way.
Dynamical simulations of radiation damage induced by 10 keV energetic recoils in UO 2
NASA Astrophysics Data System (ADS)
Tian, X. F.; Gao, T.; Long, Chongsheng; Li, JiuKai; Jiang, Gang; Xiao, Hongxing
2011-08-01
We have performed classical molecular dynamics simulations to simulate the primary damage state induced by 10 keV energetic recoils in UO 2. The numbers versus time and the distance distributions for the displaced uranium and oxygen atoms were investigated with the energetic recoils accelerated along four different directions. The simulations suggest that the direction of the primary knock-on atom (PKA) has no effect on the final primary damage state. In addition, it was found that atomic displacement events consisted of replacement collision sequences in addition to the production of Frenkel pairs. The spatial distribution of defects introduced by 10 keV collision cascades was also presented and the results were similar to that of energetic recoils with lower energy.
Microwave quantum refrigeration based on the Josephson effect
NASA Astrophysics Data System (ADS)
Solinas, Paolo; Bosisio, Riccardo; Giazotto, Francesco
2016-06-01
We present a microwave quantum refrigeration principle based on the Josephson effect. When a superconducting quantum interference device (SQUID) is pierced by a time-dependent magnetic flux, it induces changes in the macroscopic quantum phase and an effective finite bias voltage appears across the SQUID. This voltage can be used to actively cool, well below the lattice temperature, one of the superconducting electrodes forming the interferometer. The achievable cooling performance combined with the simplicity and scalability intrinsic to the structure pave the way to a number of applications in quantum technology.
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.
Neutron electric form factor via recoil polarimetry
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.
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.
Boundary Effective Action for Quantum Hall States
NASA Astrophysics Data System (ADS)
Gromov, Andrey; Jensen, Kristan; Abanov, Alexander G.
2016-03-01
We consider quantum Hall states on a space with boundary, focusing on the aspects of the edge physics which are completely determined by the symmetries of the problem. There are four distinct terms of Chern-Simons type that appear in the low-energy effective action of the state. Two of these protect gapless edge modes. They describe Hall conductance and, with some provisions, thermal Hall conductance. The remaining two, including the Wen-Zee term, which contributes to the Hall viscosity, do not protect gapless edge modes but are instead related to the local boundary response fixed by symmetries. We highlight some basic features of this response. It follows that the coefficient of the Wen-Zee term can change across an interface without closing a gap or breaking a symmetry.
Continuous and Pulsed Quantum Zeno Effect
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}.
Boundary Effective Action for Quantum Hall States.
Gromov, Andrey; Jensen, Kristan; Abanov, Alexander G
2016-03-25
We consider quantum Hall states on a space with boundary, focusing on the aspects of the edge physics which are completely determined by the symmetries of the problem. There are four distinct terms of Chern-Simons type that appear in the low-energy effective action of the state. Two of these protect gapless edge modes. They describe Hall conductance and, with some provisions, thermal Hall conductance. The remaining two, including the Wen-Zee term, which contributes to the Hall viscosity, do not protect gapless edge modes but are instead related to the local boundary response fixed by symmetries. We highlight some basic features of this response. It follows that the coefficient of the Wen-Zee term can change across an interface without closing a gap or breaking a symmetry. PMID:27058090
Boundary Effective Action for Quantum Hall States.
Gromov, Andrey; Jensen, Kristan; Abanov, Alexander G
2016-03-25
We consider quantum Hall states on a space with boundary, focusing on the aspects of the edge physics which are completely determined by the symmetries of the problem. There are four distinct terms of Chern-Simons type that appear in the low-energy effective action of the state. Two of these protect gapless edge modes. They describe Hall conductance and, with some provisions, thermal Hall conductance. The remaining two, including the Wen-Zee term, which contributes to the Hall viscosity, do not protect gapless edge modes but are instead related to the local boundary response fixed by symmetries. We highlight some basic features of this response. It follows that the coefficient of the Wen-Zee term can change across an interface without closing a gap or breaking a symmetry.
On quantum effects in a theory of biological evolution.
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.
Recoil separator ERNA: gas target and beam suppression
NASA Astrophysics Data System (ADS)
Gialanella, L.; Schürmann, D.; Strieder, F.; Di Leva, A.; De Cesare, N.; D'Onofrio, A.; Imbriani, G.; Klug, J.; Lubritto, C.; Ordine, A.; Roca, V.; Röcken, H.; Rolfs, C.; Rogalla, D.; Romano, M.; Schümann, F.; Terrasi, F.; Trautvetter, H. P.
2004-04-01
For improved cross-section measurements of the reaction 12C(α,γ) 16O in inverted kinematics, a recoil separator ERNA is developed at the 4 MV Dynamitron tandem accelerator in Bochum to detect directly the 16O recoils with high efficiency. The 16O recoils are produced by the 12C projectiles in a windowless 4He gas target. We report on the pressure profile of the gas target, the beam suppression by the separator, and the first observation of the 16O recoils at selected energies.
Thermal recoil force, telemetry, and the Pioneer anomaly
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.
Quantum confinement effects across two-dimensional planes in MoS{sub 2} quantum dots
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.
The effective field theory treatment of quantum gravity
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.
Kondo effects in triangular triple quantum dots
NASA Astrophysics Data System (ADS)
Oguri, Akira; Numata, Takahide; Nisikawa, Yunori; Hewson, A. C.
2009-03-01
We study the conductance through a triangular triple quantum dot, which is connected to two noninteracting leads, using the numerical renormalization group (NRG). It is found that the system shows a variety of Kondo effects depending on the filling of the triangle. The SU(4) Kondo effect occurs at half-filling, and a sharp conductance dip due to a phase lapse appears in the gate-voltage dependence. Furthermore, when four electrons occupy the three sites on average, a local S=1 moment, which is caused by the Nagaoka mechanism, is induced along the triangle. The temperature dependence of the entropy and spin susceptibility of the triangle shows that this moment is screened by the conduction electrons via two separate stages at different temperatures. The two-terminal and four-terminal conductances show a clear difference at the gate voltages, where the SU(4) or the S=1 Kondo effects occur[1]. We will also discuss effects of deformations of the triangular configuration, caused by the inhomogeneity in the inter-dot couplings and in the gate voltages. [4pt] [1] T.Numata, Y.Nisikawa, A.Oguri, and A.C.Hewson: arXiv:0808.3496.
Quantum teleportation of nonclassical wave packets: An effective multimode theory
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.
Quantum chemistry of quantum dots: Effects of ligands and oxidation
NASA Astrophysics Data System (ADS)
Inerbaev, Talgat M.; Masunov, Artëm E.; Khondaker, Saiful I.; Dobrinescu, Alexandra; Plamadǎ, Andrei-Valentin; Kawazoe, Yoshiyuki
2009-07-01
We report Gaussian basis set density functional theory (DFT) calculations of the structure and spectra of several colloidal quantum dots (QDs) with a (CdSe)n core (n =6,15,17), that are either passivated by trimethylphosphine oxide ligands, or unpassivated and oxidized. From the ground state geometry optimization results we conclude that trimethylphosphine oxide ligands preserve the wurtzite structure of the QDs. Evaporation of the ligands may lead to surface reconstruction. We found that the number of two-coordinated atoms on the nanoparticle's surface is the critical parameter defining the optical absorption properties. For (CdSe)15 wurtzite-derived QD this number is maximal among all considered QDs and the optical absorption spectrum is strongly redshifted compared to QDs with threefold coordinated surface atoms. According to the time-dependent DFT results, surface reconstruction is accompanied by a significant decrease in the linear absorption. Oxidation of QDs destroys the perfection of the QD surface, increases the number of two-coordinated atoms and results in the appearance of an infrared absorption peak close to 700 nm. The vacant orbitals responsible for this near infrared transition have strong Se-O antibonding character. Conclusions of this study may be used in optimization of engineered nanoparticles for photodetectors and photovoltaic devices.
Quantum mechanical effects in plasmonic structures with subnanometre gaps
NASA Astrophysics Data System (ADS)
Zhu, Wenqi; Esteban, Ruben; Borisov, Andrei G.; Baumberg, Jeremy J.; Nordlander, Peter; Lezec, Henri J.; Aizpurua, Javier; Crozier, Kenneth B.
2016-06-01
Metallic structures with nanogap features have proven highly effective as building blocks for plasmonic systems, as they can provide a wide tuning range of operating frequencies and large near-field enhancements. Recent work has shown that quantum mechanical effects such as electron tunnelling and nonlocal screening become important as the gap distances approach the subnanometre length-scale. Such quantum effects challenge the classical picture of nanogap plasmons and have stimulated a number of theoretical and experimental studies. This review outlines the findings of many groups into quantum mechanical effects in nanogap plasmons, and discusses outstanding challenges and future directions.
Quantum mechanical effects in plasmonic structures with subnanometre gaps
Zhu, Wenqi; Esteban, Ruben; Borisov, Andrei G.; Baumberg, Jeremy J.; Nordlander, Peter; Lezec, Henri J.; Aizpurua, Javier; Crozier, Kenneth B.
2016-01-01
Metallic structures with nanogap features have proven highly effective as building blocks for plasmonic systems, as they can provide a wide tuning range of operating frequencies and large near-field enhancements. Recent work has shown that quantum mechanical effects such as electron tunnelling and nonlocal screening become important as the gap distances approach the subnanometre length-scale. Such quantum effects challenge the classical picture of nanogap plasmons and have stimulated a number of theoretical and experimental studies. This review outlines the findings of many groups into quantum mechanical effects in nanogap plasmons, and discusses outstanding challenges and future directions. PMID:27255556
Nuclear quantum effects and kinetic isotope effects in enzyme reactions.
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
Nuclear quantum effects and kinetic isotope effects in enzyme reactions.
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.
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.
Wang, Yunliang Lü, 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 Schrödinger 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.
NASA Astrophysics Data System (ADS)
Holovatsky, V.; Bernik, I.; Yakhnevych, M.
2016-09-01
The effect of magnetic field on electron energy spectrum, wave functions and probabilities of intraband quantum transitions in multilayered spherical quantum-dot-quantum-well (QDQW) CdSe/ZnS/CdSe/ZnS is studied. Computations are performed in the framework of the effective mass approximation and rectangular potential barriers model. The wave functions are expanded over the complete basis of functions obtained as exact solutions of the Schrodinger equation for the electron in QDQW without the magnetic field. It is shown that magnetic field takes off the spectrum degeneration with respect to the magnetic quantum number and changes the localization of electron in the nanostructure. The field stronger effects on the spherically-symmetric states, especially in the case of electron location in the outer potential well. The magnetic field changes more the radial distribution of probability of electron location in QDQW than the angular one. The oscillator strengths of intraband quantum transitions are calculated as functions of the magnetic field induction and their selection rules are established.
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.
Multidimensional quantum tunneling in the Schwinger effect
NASA Astrophysics Data System (ADS)
Dumlu, Cesim K.
2016-03-01
We study the Schwinger effect, in which the external field having a spatiotemporal profile creates electron-positron pairs via multidimensional quantum tunneling. Our treatment is based on the trace formula for the QED effective action, whose imaginary part is represented by a sum over complex worldline solutions. The worldlines are multiperiodic, and the periods of motion collectively depend on the strength of spatial and temporal inhomogeneity. We argue that the classical action that leads to the correct tunneling amplitude must take into account both the full period, T ˜ and the first fundamental period, T1. In view of this argument we investigate pair production in an exponentially damped sinusoidal field and find that the initial momenta for multiperiodic trajectories lie on parabolic curves, such that on each curve the ratio T ˜/T1 stays uniform. Evaluation of the tunneling amplitude using these trajectories shows that vacuum decay rate is reduced by an order of magnitude, with respect to the purely time-dependent case, due to the presence of magnetic field.
Integer quantum Hall effect and correlated disorder
Greshnov, A. A. Zegrya, G. G.
2007-11-15
The effect of the form of the random potential of impurities and defects on the longitudinal {sigma}{sub xx} and Hall {sigma}{sub xy} components of conductivity in the mode of the integer quantum Hall effect is theoretically investigated. It is shown that the width of the Hall conductivity plateau as well as the peak values of the longitudinal conductivity heavily depend on the ratio {lambda}/a{sub H} between the random potential correlation length and the magnetic length. For the first time, it is established that in the case of the short-wavelength potential {lambda} << a{sub H}, the peak values of {sigma}{sub xx}{sup (N)} are directly proportional to the Landau level number N {>=} 1, {sigma}{sub xx} = 0.5Ne{sup 2}/h, whereas the peak values of {sigma}{sub xx}{sup (N)} are independent of the Landau level number in the case of the long-wavelength potential {lambda} >> a{sub H}, and their magnitude is much lower than 0.5e{sup 2}/h. The obtained results are in good agreement with the available experimental data.
Quantum Spin Hall Effect in Ultrasonic Metamaterials
NASA Astrophysics Data System (ADS)
Mousavi, S. Hossein; Khanikaev, Alexander B.; Wang, Zheng
2015-03-01
The discovery of topological order without breaking time-reversal symmetry, such as that in Quantum Spin Hall (QSH) effect and Topological Insulators, is one of the most groundbreaking advancements of recent years in condensed matters physics. The approach to topological order without breaking time-reversal symmetry is particularly important in elastics because no natural elastic materials show linear nonreciprocal response. Here we illustrate the first elastic-wave system emulating QSH effect and demonstrate existence of topologically protected elastic edge states. The system represents an elastic metamaterial-based phononic crystal. In this crystal, we achieved degenerate linear dispersion for two sets of modes, classified by one of the system's symmetries. Then, by relaxing and removing that symmetry by deliberately engineering a gauge field emulating a strong spin-orbit coupling of QSH, we observe opening a complete topological bandgap. Finally, the hallmark of the topological order, namely the presence of one-way chiral edge waves insensitive to nonmagnetic defects and disorders, is demonstrated in such elastic metacrystals. We illustrate the unique property of these elastic edge waves to flow around sharp corners without back-reflection or localization.
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.
Integer quantum Hall effect for bosons.
Senthil, T; Levin, Michael
2013-01-25
A simple physical realization of an integer quantum Hall state of interacting two dimensional bosons is provided. This is an example of a symmetry-protected topological (SPT) phase which is a generalization of the concept of topological insulators to systems of interacting bosons or fermions. Universal physical properties of the boson integer quantum Hall state are described and shown to correspond with those expected from general classifications of SPT phases.
Magnetoresistance from quantum interference effects in ferromagnets
Manyala; Sidis; DiTusa; Aeppli; Young; Fisk
2000-04-01
The desire to maximize the sensitivity of read/write heads (and thus the information density) of magnetic storage devices has stimulated interest in the discovery and design of new magnetic materials exhibiting magnetoresistance. Recent discoveries include the 'colossal' magnetoresistance in the manganites and the enhanced magnetoresistance in low-carrier-density ferromagnets. An important feature of these systems is that the electrons involved in electrical conduction are different from those responsible for the magnetism. The latter are localized and act as scattering sites for the mobile electrons, and it is the field tuning of the scattering strength that ultimately gives rise to the observed magnetoresistance. Here we argue that magnetoresistance can arise by a different mechanism in certain ferromagnets--quantum interference effects rather than simple scattering. The ferromagnets in question are disordered, low-carrier-density magnets where the same electrons are responsible for both the magnetic properties and electrical conduction. The resulting magnetoresistance is positive (that is, the resistance increases in response to an applied magnetic field) and only weakly temperature-dependent below the Curie point.
Observing quantum trajectories: From Mott's problem to quantum Zeno effect and back
NASA Astrophysics Data System (ADS)
de Gosson, Maurice; Hiley, Basil; Cohen, Eliahu
2016-11-01
The experimental results of Kocsis et al., Mahler et al. and the proposed experiments of Morley et al. show that it is possible to construct "trajectories" in interference regions in a two-slit interferometer. These results call for a theoretical re-appraisal of the notion of a "quantum trajectory" first introduced by Dirac and in the present paper we re-examine this notion from the Bohm perspective based on Hamiltonian flows. In particular, we examine the short-time propagator and the role that the quantum potential plays in determining the form of these trajectories. These trajectories differ from those produced in a typical particle tracker and the key to this difference lies in the active suppression of the quantum potential necessary to produce Mott-type trajectories. We show, using a rigorous mathematical argument, how the active suppression of this potential arises. Finally we discuss in detail how this suppression also accounts for the quantum Zeno effect.
Quantum nondemolition photon detection in circuit QED and the quantum Zeno effect
Helmer, Ferdinand; Marquardt, Florian; Mariantoni, Matteo; Solano, Enrique
2009-05-15
We analyze the detection of itinerant photons using a quantum nondemolition measurement. An important example is the dispersive detection of microwave photons in circuit quantum electrodynamics, which can be realized via the nonlinear interaction between photons inside a superconducting transmission line resonator. We show that the back action due to the continuous measurement imposes a limit on the detector efficiency in such a scheme. We illustrate this using a setup where signal photons have to enter a cavity in order to be detected dispersively. In this approach, the measurement signal is the phase shift imparted to an intense beam passing through a second cavity mode. The restrictions on the fidelity are a consequence of the quantum Zeno effect, and we discuss both analytical results and quantum trajectory simulations of the measurement process.
Quantum effects for particles channeling in a bent crystal
NASA Astrophysics Data System (ADS)
Feranchuk, Ilya; San, Nguyen Quang
2016-09-01
Quantum mechanical theory for channeling of the relativistic charged particles in the bent crystals is considered in the paper. Quantum effects of under-barrier tunneling are essential when the radius of the curvature is closed to its critical value. In this case the wave functions of the quasi-stationary states corresponding to the particles captured in a channel are presented in the analytical form. The efficiency of channeling of the particles and their angular distribution at the exit crystal surface are calculated. Characteristic experimental parameters for observation the quantum effects are estimated.
Plasmon modes of metallic nanowires including quantum nonlocal effects
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.
Computational approach for calculating bound states in quantum field theory
NASA Astrophysics Data System (ADS)
Lv, Q. Z.; Norris, S.; Brennan, R.; Stefanovich, E.; Su, Q.; Grobe, R.
2016-09-01
We propose a nonperturbative approach to calculate bound-state energies and wave functions for quantum field theoretical models. It is based on the direct diagonalization of the corresponding quantum field theoretical Hamiltonian in an effectively discretized and truncated Hilbert space. We illustrate this approach for a Yukawa-like interaction between fermions and bosons in one spatial dimension and show where it agrees with the traditional method based on the potential picture and where it deviates due to recoil and radiative corrections. This method permits us also to obtain some insight into the spatial characteristics of the distribution of the fermions in the ground state, such as the bremsstrahlung-induced widening.
Enigmatic 12/5 fractional quantum Hall effect
NASA Astrophysics Data System (ADS)
Pakrouski, Kiryl; Troyer, Matthias; Wu, Yang-Le; Das Sarma, Sankar; Peterson, Michael R.
2016-08-01
We numerically study the fractional quantum Hall effect at filling factors ν =12 /5 and 13/5 (the particle-hole conjugate of 12/5) in high-quality two-dimensional GaAs heterostructures via exact diagonalization including finite well width and Landau-level mixing. We find that Landau-level mixing suppresses the ν =13 /5 fractional quantum Hall effect relative to ν =12 /5 . By contrast, we find both ν =2 /5 and (its particle-hole conjugate) ν =3 /5 fractional quantum Hall effects in the lowest Landau level to be robust under Landau-level mixing and finite well-width corrections. Our results provide a possible explanation for the experimental absence of the 13/5 fractional quantum Hall state as caused by Landau-level mixing effects.
Fractional quantum Hall effect in the absence of Landau levels.
Sheng, D N; Gu, Zheng-Cheng; Sun, Kai; Sheng, L
2011-01-01
It is well known that the topological phenomena with fractional excitations, the fractional quantum Hall effect, will emerge when electrons move in Landau levels. Here we show the theoretical discovery of the fractional quantum Hall effect in the absence of Landau levels in an interacting fermion model. The non-interacting part of our Hamiltonian is the recently proposed topologically non-trivial flat-band model on a checkerboard lattice. In the presence of nearest-neighbouring repulsion, we find that at 1/3 filling, the Fermi-liquid state is unstable towards the fractional quantum Hall effect. At 1/5 filling, however, a next-nearest-neighbouring repulsion is needed for the occurrence of the 1/5 fractional quantum Hall effect when nearest-neighbouring repulsion is not too strong. We demonstrate the characteristic features of these novel states and determine the corresponding phase diagram.
Intrinsic Spin Hall Effect Induced by Quantum Phase Transition in HgCdTe Quantum Wells
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.
Anomaly-free cosmological perturbations in effective canonical quantum gravity
Barrau, Aurelien; Calcagni, Gianluca; Grain, Julien E-mail: bojowald@gravity.psu.edu E-mail: julien.grain@ias.u-psud.fr
2015-05-01
This article lays out a complete framework for an effective theory of cosmological perturbations with corrections from canonical quantum gravity. Since several examples exist for quantum-gravity effects that change the structure of space-time, the classical perturbative treatment must be rethought carefully. The present discussion provides a unified picture of several previous works, together with new treatments of higher-order perturbations and the specification of initial states.
A gun recoil system employing a magnetorheological fluid damper
NASA Astrophysics Data System (ADS)
Li, Z. C.; Wang, J.
2012-10-01
This research aims to design and control a full scale gun recoil buffering system which works under real firing impact loading conditions. A conventional gun recoil absorber is replaced with a controllable magnetorheological (MR) fluid damper. Through dynamic analysis of the gun recoil system, a theoretical model for optimal design and control of the MR fluid damper for impact loadings is derived. The optimal displacement, velocity and optimal design rules are obtained. By applying the optimal design theory to protect against impact loadings, an MR fluid damper for a full scale gun recoil system is designed and manufactured. An experimental study is carried out on a firing test rig which consists of a 30 mm caliber, multi-action automatic gun with an MR damper mounted to the fixed base through a sliding guide. Experimental buffering results under passive control and optimal control are obtained. By comparison, optimal control is better than passive control, because it produces smaller variation in the recoil force while achieving less displacement of the recoil body. The optimal control strategy presented in this paper is open-loop with no feedback system needed. This means that the control process is sensor-free. This is a great benefit for a buffering system under impact loading, especially for a gun recoil system which usually works in a harsh environment.
Modeling the Observability of Recoiling Black Holes as Offset Quasars
NASA Astrophysics Data System (ADS)
Blecha, Laura; Torrey, Paul; Vogelsberger, Mark; Genel, Shy; Springel, Volker; Sijacki, Debora; Snyder, Gregory; Bird, Simeon; Nelson, Dylan; Xu, Dandan; Hernquist, Lars
2015-08-01
The merger of two supermassive black holes (SMBHs) imparts a gravitational-wave (GW) recoil kick to the remnant SMBH. In extreme cases these kicks may be thousands of km/s -- enough to easily eject them from their host galaxies. Moderate recoil kicks may also cause substantial displacements of the SMBH, however. An actively-accreting, recoiling SMBH may be observable as an offset quasar. Prior to the advent of a space-based GW observatory, detections of these offset quasars may offer the best chance for identifying recent SMBH mergers. Indeed, observational searches for recoiling quasars have already identified several promising candidates. However, systematic searches for recoils are currently hampered by large uncertainties regarding how often offset quasars should be observable, where they are most likely to be found, and whether BH spin alignment prior to merger is efficient at suppressing large recoils. Motivated by this, we have developed a model for the observable population of recoiling quasars in a cosmological framework, utilizing detailed information about the progenitor galaxies from state-of-the-art cosmological hydrodynamic simulations (the Illustris Project). The model for offset quasar lifetimes includes a physically-motivated, time-dependent model for accretion onto kicked SMBHs, and results are analyzed for a range of possible BH spin alignment models. We find that the observability of offset quasars depends strongly on the efficiency of pre-merger spin alignment, with promising indications that observations of recoils could distinguish between at least the extreme limits of spin alignment models. Our results also suggest that observable offset quasars should inhabit preferred types of host galaxies, where again these populations depend on the degree of pre-merger spin alignment. These findings will be valuable for planned and future dedicated searches for recoiling quasars, and they indicate that such objects might be used to place indirect
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.
Quantum effects improve the energy efficiency of feedback control.
Horowitz, Jordan M; Jacobs, Kurt
2014-04-01
The laws of thermodynamics apply equally well to quantum systems as to classical systems, and because of this, quantum effects do not change the fundamental thermodynamic efficiency of isothermal refrigerators or engines. We show that, despite this fact, quantum mechanics permits measurement-based feedback control protocols that are more thermodynamically efficient than their classical counterparts. As part of our analysis, we perform a detailed accounting of the thermodynamics of unitary feedback control and elucidate the sources of inefficiency in measurement-based and coherent feedback.
General relativistic effects in quantum interference of “clocks”
NASA Astrophysics Data System (ADS)
Zych, M.; Pikovski, I.; Costa, F.; Brukner, Č.
2016-06-01
Quantum mechanics and general relativity have been each successfully tested in numerous experiments. However, the regime where both theories are jointly required to explain physical phenomena remains untested by laboratory experiments, and is also not fully understood by theory. This contribution reviews recent ideas for a new type of experiments: quantum interference of “clocks”, which aim to test novel quantum effects that arise from time dilation. “Clock” interference experiments could be realised with atoms or photons in near future laboratory experiments.
Quantum effects improve the energy efficiency of feedback control.
Horowitz, Jordan M; Jacobs, Kurt
2014-04-01
The laws of thermodynamics apply equally well to quantum systems as to classical systems, and because of this, quantum effects do not change the fundamental thermodynamic efficiency of isothermal refrigerators or engines. We show that, despite this fact, quantum mechanics permits measurement-based feedback control protocols that are more thermodynamically efficient than their classical counterparts. As part of our analysis, we perform a detailed accounting of the thermodynamics of unitary feedback control and elucidate the sources of inefficiency in measurement-based and coherent feedback. PMID:24827219
Topological Effects on Quantum Phase Slips in Superfluid Spin Transport
NASA Astrophysics Data System (ADS)
Kim, Se Kwon; Tserkovnyak, Yaroslav
2016-03-01
We theoretically investigate effects of quantum fluctuations on superfluid spin transport through easy-plane quantum antiferromagnetic spin chains in the large-spin limit. Quantum fluctuations result in the decaying spin supercurrent by unwinding the magnetic order parameter within the easy plane, which is referred to as phase slips. We show that the topological term in the nonlinear sigma model for the spin chains qualitatively differentiates the decaying rate of the spin supercurrent between the integer versus half-odd-integer spin chains. An experimental setup for a magnetoelectric circuit is proposed, in which the dependence of the decaying rate on constituent spins can be verified by measuring the nonlocal magnetoresistance.
Hall effect in quantum critical charge-cluster glass
NASA Astrophysics Data System (ADS)
Wu, Jie; Bollinger, Anthony T.; Sun, Yujie
2016-04-01
Upon doping, cuprates undergo a quantum phase transition from an insulator to a d-wave superconductor. The nature of this transition and of the insulating state is vividly debated. Here, we study the Hall effect in La2-xSrxCuO4 (LSCO) samples doped near the quantum critical point at x ˜ 0.06. Dramatic fluctuations in the Hall resistance appear below TCG ˜ 1.5 K and increase as the sample is cooled down further, signaling quantum critical behavior. We explore the doping dependence of this effect in detail, by studying a combinatorial LSCO library in which the Sr content is varied in extremely fine steps, Δx ˜ 0.00008. We observe that quantum charge fluctuations wash out when superconductivity emerges but can be restored when the latter is suppressed by applying a magnetic field, showing that the two instabilities compete for the ground state.
Hall effect in quantum critical charge-cluster glass.
Wu, Jie; Bollinger, Anthony T; Sun, Yujie; Božović, Ivan
2016-04-19
Upon doping, cuprates undergo a quantum phase transition from an insulator to a d-wave superconductor. The nature of this transition and of the insulating state is vividly debated. Here, we study the Hall effect in La2-xSrxCuO4(LSCO) samples doped near the quantum critical point atx∼ 0.06. Dramatic fluctuations in the Hall resistance appear belowTCG∼ 1.5 K and increase as the sample is cooled down further, signaling quantum critical behavior. We explore the doping dependence of this effect in detail, by studying a combinatorial LSCO library in which the Sr content is varied in extremely fine steps,Δx∼ 0.00008. We observe that quantum charge fluctuations wash out when superconductivity emerges but can be restored when the latter is suppressed by applying a magnetic field, showing that the two instabilities compete for the ground state. PMID:27044081
Effective Hamiltonian for the hybrid double quantum dot qubit
NASA Astrophysics Data System (ADS)
Ferraro, E.; De Michielis, M.; Mazzeo, G.; Fanciulli, M.; Prati, E.
2014-05-01
Quantum dot hybrid qubits formed from three electrons in double quantum dots represent a promising compromise between high speed and simple fabrication for solid state implementations of single-qubit and two-qubits quantum logic ports. We derive the Schrieffer-Wolff effective Hamiltonian that describes in a simple and intuitive way the qubit by combining a Hubbard-like model with a projector operator method. As a result, the Hubbard-like Hamiltonian is transformed in an equivalent expression in terms of the exchange coupling interactions between pairs of electrons. The effective Hamiltonian is exploited to derive the dynamical behavior of the system and its eigenstates on the Bloch sphere to generate qubits operation for quantum logic ports. A realistic implementation in silicon and the coupling of the qubit with a detector are discussed.
Piezo-Phototronic Effect in a Quantum Well Structure.
Huang, Xin; Du, Chunhua; Zhou, Yongli; Jiang, Chunyan; Pu, Xiong; Liu, Wei; Hu, Weiguo; Chen, Hong; Wang, Zhong Lin
2016-05-24
With enhancements in the performance of optoelectronic devices, the field of piezo-phototronics has attracted much attention, and several theoretical works have been reported based on semiclassical models. At present, the feature size of optoelectronic devices are rapidly shrinking toward several tens of nanometers, which results in the quantum confinement effect. Starting from the basic piezoelectricity equation, Schrödinger equation, Poisson equation, and Fermi's golden rule, a self-consistent theoretical model is proposed to study the piezo-phototronic effect in the framework of perturbation theory in quantum mechanics. The validity and universality of this model are well-proven with photoluminescence measurements in a single GaN/InGaN quantum well and multiple GaN/InGaN quantum wells. This study provides important insight into the working principle of nanoscale piezo-phototronic devices as well as guidance for the future device design.
Hall effect in quantum critical charge-cluster glass
Wu, Jie; Bollinger, Anthony T.; Sun, Yujie; Božović, Ivan
2016-01-01
Upon doping, cuprates undergo a quantum phase transition from an insulator to a d-wave superconductor. The nature of this transition and of the insulating state is vividly debated. Here, we study the Hall effect in La2-xSrxCuO4 (LSCO) samples doped near the quantum critical point at x ∼ 0.06. Dramatic fluctuations in the Hall resistance appear below TCG ∼ 1.5 K and increase as the sample is cooled down further, signaling quantum critical behavior. We explore the doping dependence of this effect in detail, by studying a combinatorial LSCO library in which the Sr content is varied in extremely fine steps, Δx ∼ 0.00008. We observe that quantum charge fluctuations wash out when superconductivity emerges but can be restored when the latter is suppressed by applying a magnetic field, showing that the two instabilities compete for the ground state. PMID:27044081
Hall effect in quantum critical charge-cluster glass.
Wu, Jie; Bollinger, Anthony T; Sun, Yujie; Božović, Ivan
2016-04-19
Upon doping, cuprates undergo a quantum phase transition from an insulator to a d-wave superconductor. The nature of this transition and of the insulating state is vividly debated. Here, we study the Hall effect in La2-xSrxCuO4(LSCO) samples doped near the quantum critical point atx∼ 0.06. Dramatic fluctuations in the Hall resistance appear belowTCG∼ 1.5 K and increase as the sample is cooled down further, signaling quantum critical behavior. We explore the doping dependence of this effect in detail, by studying a combinatorial LSCO library in which the Sr content is varied in extremely fine steps,Δx∼ 0.00008. We observe that quantum charge fluctuations wash out when superconductivity emerges but can be restored when the latter is suppressed by applying a magnetic field, showing that the two instabilities compete for the ground state.
Gravitational Recoil of Inspiraling Black Hole Binaries to Second Post-Newtonian Order
NASA Astrophysics Data System (ADS)
Blanchet, Luc; Qusailah, Moh'd. S. S.; Will, Clifford M.
2005-12-01
The loss of linear momentum by gravitational radiation and the resulting gravitational recoil of black hole binary systems may play an important role in the growth of massive black holes in early galaxies. We calculate the gravitational recoil of nonspinning black hole binaries at the second post-Newtonian order (2 PN) beyond the dominant effect, obtaining, for the first time, the 1.5 PN correction term due to tails of waves and the next 2 PN term. We find that the maximum value of the net recoil experienced by the binary due to the inspiral phase up to the innermost stable circular orbit (ISCO) is of the order of 22 km s-1. We then estimate the kick velocity accumulated during the plunge from the ISCO up to the horizon by integrating the momentum flux using the 2 PN formula along a plunge geodesic of the Schwarzschild metric. We find that the contribution of the plunge dominates over that of the inspiral. For a mass ratio m2/m1=1/8, we estimate a total recoil velocity (due to both adiabatic and plunge phases) of 100+/-20 km s-1. For a ratio of 0.38, the recoil is maximum, and we estimate it to be 250+/-50 km s-1. In the limit of small mass ratio, we estimate V/c~0.043(+/-20%)(m2/m1)2. Our estimates are consistent with, but span a substantially narrower range than, those of Favata and coworkers.
Quantum Confinement Effects in Silicon Nanocrystals
NASA Astrophysics Data System (ADS)
Ogut, Serdar
1998-03-01
Quasiparticle gaps, self-energy corrections, exciton Coulomb energies, and optical gaps in Si quantum dots are calculated from first principles.(S. Öğ)üt, J. R. Chelikowsky, and S. G. Louie, Phys. Rev. Lett. 79, 1770 (1997). The calculations are performed on hydrogen-passivated spherical Si clusters with diameters up to 32 Å ( ~ 1200 Si and H atoms). Such a large ab initio quantum mechanical modeling can be accomplished efficiently using a real space higher-order finite difference pseudopotential method(J. R. Chelikowsky, N. Troullier, and Y. Saad, Phys. Rev. Lett. 72), 1240 (1994) on a massively parallel computational platform (T3E).(A. Stathopoulos, S. Öğ)üt, Y. Saad, J. R. Chelikowsky, and H. Kim, (submitted to IEEE Comput. Sci. Eng.) It is shown that (i) the size-dependent self-energy correction in quantum dots is enhanced substantially compared to bulk, and (ii) quantum confinement and reduced electronic screening result in appreciable excitonic Coulomb energies. Calculated optical gaps are in very good agreement with absorption data from Si nanocrystallites.
Macroscopic quantum effects in intrinsic Josephson junction stacks
NASA Astrophysics Data System (ADS)
Koyama, T.; Machida, M.
2008-09-01
A macroscopic quantum theory for the capacitively-coupled intrinsic Josephson junctions (IJJ’s) is constructed. We clarify the multi-junction effect for the macroscopic quantum tunneling (MQT) to the first resistive branch. It is shown that the escape rate is greatly enhanced by the capacitive coupling between junctions. We also discuss the origin of the N2-enhancement in the escape rate observed in the uniformly switching in Bi-2212 IJJ’s.
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.
Quantum Electrodynamics Effects in Heavy Ions and Atoms
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.
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.
Quantum Hall effect in bilayer system with array of antidots
NASA Astrophysics Data System (ADS)
Pagnossin, I. R.; Gusev, G. M.; Sotomayor, N. M.; Seabra, A. C.; Quivy, A. A.; Lamas, T. E.; Portal, J. C.
2007-04-01
We have studied the Quantum Hall effect in a bilayer system modulated by gate-controlled antidot lattice potential. The Hall resistance shows plateaus which are quantized to anomalous multiplies of h/e2. We suggest that this complex behavior is due to the nature of the edge-states in double quantum well (DQW) structures coupled to an array of antidots: these plateaus may be originated from the coexistence of normal and counter-rotating edge-states in different layers.
Effective quantum dynamics of interacting systems with inhomogeneous coupling
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.
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].
Ge/SiGe quantum well for photonic applications: modelling of the quantum confined Stark effect
NASA Astrophysics Data System (ADS)
Isella, Giovanni; Ballabio, Andrea; Frigerio, Jacopo
2016-05-01
Ge quantum wells are emerging as a relevant material system for enabling fast and power-efficient optical modulation in the framework of Si-photonics. The need for reliable designs of QW structures, matching given operating wavelengths and bias voltages, calls for the implementation of modelling tools capturing the optical properties of SiGe heterostructures. Here we report on the calculation of the quantum confined Stark effect based on an eight-band k×p model. The obtained spectra are analysed and compared with experimental data showing a good agreement between calculation and measurements.
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.
Recoil splitting of x-ray-induced optical fluorescence
Gavrilyuk, S.; Aagren, H.; Gel'mukhanov, F.; Sun, Y.-P.; Levin, S.
2010-03-15
We show that the anisotropy of the recoil velocity distribution of x-ray-ionized atoms or molecules leads to observable splittings in subsequent optical fluorescence or absorption when the polarization vector of the x rays is parallel to the momentum of the fluorescent photons. The order of the magnitude of the recoil-induced splitting is about 10 {mu}eV, which can be observed using Fourier or laser-absorption spectroscopic techniques.
Unconventional quantum Hall effect in Floquet topological insulators.
Tahir, M; Vasilopoulos, P; Schwingenschlögl, U
2016-09-28
We study an unconventional quantum Hall effect for the surface states of ultrathin Floquet topological insulators in a perpendicular magnetic field. The resulting band structure is modified by photon dressing and the topological property is governed by the low-energy dynamics of a single surface. An exchange of symmetric and antisymmetric surface states occurs by reversing the light's polarization. We find a novel quantum Hall state in which the zeroth Landau level undergoes a phase transition from a trivial insulator state, with Hall conductivity [Formula: see text] at zero Fermi energy, to a Hall insulator state with [Formula: see text]. These findings open new possibilities for experimentally realizing nontrivial quantum states and unusual quantum Hall plateaus at [Formula: see text].
Unconventional quantum Hall effect in Floquet topological insulators.
Tahir, M; Vasilopoulos, P; Schwingenschlögl, U
2016-09-28
We study an unconventional quantum Hall effect for the surface states of ultrathin Floquet topological insulators in a perpendicular magnetic field. The resulting band structure is modified by photon dressing and the topological property is governed by the low-energy dynamics of a single surface. An exchange of symmetric and antisymmetric surface states occurs by reversing the light's polarization. We find a novel quantum Hall state in which the zeroth Landau level undergoes a phase transition from a trivial insulator state, with Hall conductivity [Formula: see text] at zero Fermi energy, to a Hall insulator state with [Formula: see text]. These findings open new possibilities for experimentally realizing nontrivial quantum states and unusual quantum Hall plateaus at [Formula: see text]. PMID:27460419
Unconventional quantum Hall effect in Floquet topological insulators
NASA Astrophysics Data System (ADS)
Tahir, M.; Vasilopoulos, P.; Schwingenschlögl, U.
2016-09-01
We study an unconventional quantum Hall effect for the surface states of ultrathin Floquet topological insulators in a perpendicular magnetic field. The resulting band structure is modified by photon dressing and the topological property is governed by the low-energy dynamics of a single surface. An exchange of symmetric and antisymmetric surface states occurs by reversing the light’s polarization. We find a novel quantum Hall state in which the zeroth Landau level undergoes a phase transition from a trivial insulator state, with Hall conductivity {σyx}=0 at zero Fermi energy, to a Hall insulator state with {σyx}={{e}2}/2h . These findings open new possibilities for experimentally realizing nontrivial quantum states and unusual quantum Hall plateaus at (+/- 1/2,+/- 3/2,+/- 5/2,...){{e}2}/h .
OPTICS. Quantum spin Hall effect of light.
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
OPTICS. Quantum spin Hall effect of light.
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.
Quantum spin Hall effect of light
NASA Astrophysics Data System (ADS)
Bliokh, Konstantin Y.; Smirnova, Daria; Nori, Franco
2015-06-01
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.
Quantum electrodynamical effects in dusty plasmas
NASA Astrophysics Data System (ADS)
Marklund, M.; Stenflo, L.; Shukla, P. K.; Brodin, G.
2005-07-01
A new nonlinear electromagnetic wave mode in a magnetized dusty plasma is predicted. Its existence depends on the interaction of an intense circularly polarized electromagnetic wave with a dusty plasma, where quantum electrodynamical photon-photon scattering is taken into account. Specifically, we consider a dusty electron-positron-ion plasma and show that the propagation of the new mode is admitted. It could be of significance for the physics of supernova remnants and in neutron star formation.
Linear and nonlinear electrostatic modes in a strongly coupled quantum plasma
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.
Linear and nonlinear electrostatic modes in a strongly coupled quantum plasma
NASA Astrophysics Data System (ADS)
Ghosh, Samiran; Chakrabarti, Nikhil; Shukla, P. K.
2012-07-01
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.
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.
The microscopic nature of localization in the quantum Hall effect.
Ilani, S; Martin, J; Teitelbaum, E; Smet, J H; Mahalu, D; Umansky, V; Yacoby, A
2004-01-22
The quantum Hall effect arises from the interplay between localized and extended states that form when electrons, confined to two dimensions, are subject to a perpendicular magnetic field. The effect involves exact quantization of all the electronic transport properties owing to particle localization. In the conventional theory of the quantum Hall effect, strong-field localization is associated with a single-particle drift motion of electrons along contours of constant disorder potential. Transport experiments that probe the extended states in the transition regions between quantum Hall phases have been used to test both the theory and its implications for quantum Hall phase transitions. Although several experiments on highly disordered samples have affirmed the validity of the single-particle picture, other experiments and some recent theories have found deviations from the predicted universal behaviour. Here we use a scanning single-electron transistor to probe the individual localized states, which we find to be strikingly different from the predictions of single-particle theory. The states are mainly determined by Coulomb interactions, and appear only when quantization of kinetic energy limits the screening ability of electrons. We conclude that the quantum Hall effect has a greater diversity of regimes and phase transitions than predicted by the single-particle framework. Our experiments suggest a unified picture of localization in which the single-particle model is valid only in the limit of strong disorder.
Fano-Andreev effect in Quantum Dots in Kondo regime
NASA Astrophysics Data System (ADS)
Orellana, Pedro; Calle, Ana Maria; Pacheco, Monica; Apel, Victor
In the present work, we investigate the transport through a T-shaped double quantum dot system coupled to two normal leads and to a superconducting lead. We study the role of the superconducting lead in the quantum interferometric features of the double quantum dot and by means of a slave boson mean field approximation at low temperature regime. We inquire into the influence of intradot interactions in the electronic properties of the system as well. Our results show that Fano resonances due to Andreev bound states are exhibited in the transmission from normal to normal lead as a consequence of quantum interference and proximity effect. This Fano effect produced by Andreev bound states in a side quantum dot was called Fano-Andreev effect, which remains valid even if the electron-electron interaction are taken into account, that is, the Fano-Andreev effect is robust against e-e interactions even in Kondo regime. We acknowledge the financial support from FONDECYT program Grants No. 3140053 and 11400571.
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.
Quantum Effects on the Capacitance of Graphene-Based Electrodes
Zhan, Cheng; Neal, Justin; Wu, Jianzhong; Jiang, De-en
2015-09-08
We recently measured quantum capacitance for electric double layers (EDL) at electrolyte/graphene interfaces. However, the importance of quantum capacitance in realistic carbon electrodes is not clear. Toward understanding that from a theoretical perspective, here we studied the quantum capacitance and total capacitance of graphene electrodes as a function of the number of graphene layers. The quantum capacitance was obtained from electronic density functional theory based on fixed band approximation with an implicit solvation model, while the EDL capacitances were from classical density functional theory. We found that quantum capacitance plays a dominant role in total capacitance of the single-layer graphene both in aqueous and ionic-liquid electrolytes but the contribution decreases as the number of graphene layers increases. Moreover, the total integral capacitance roughly levels off and is dominated by the EDL capacitance beyond about four graphene layers. Finally, because many porous carbons have nanopores with stacked graphene layers at the surface, this research provides a good estimate of the effect of quantum capacitance on their electrochemical performance.
Quantum Effects on the Capacitance of Graphene-Based Electrodes
Zhan, Cheng; Neal, Justin; Wu, Jianzhong; Jiang, De-en
2015-09-08
We recently measured quantum capacitance for electric double layers (EDL) at electrolyte/graphene interfaces. However, the importance of quantum capacitance in realistic carbon electrodes is not clear. Toward understanding that from a theoretical perspective, here we studied the quantum capacitance and total capacitance of graphene electrodes as a function of the number of graphene layers. The quantum capacitance was obtained from electronic density functional theory based on fixed band approximation with an implicit solvation model, while the EDL capacitances were from classical density functional theory. We found that quantum capacitance plays a dominant role in total capacitance of the single-layer graphenemore » both in aqueous and ionic-liquid electrolytes but the contribution decreases as the number of graphene layers increases. Moreover, the total integral capacitance roughly levels off and is dominated by the EDL capacitance beyond about four graphene layers. Finally, because many porous carbons have nanopores with stacked graphene layers at the surface, this research provides a good estimate of the effect of quantum capacitance on their electrochemical performance.« less
Recoil-α-fission and recoil-α-α-fission events observed in the reaction 48Ca + 243Am
NASA Astrophysics Data System (ADS)
Forsberg, U.; Rudolph, D.; Andersson, L.-L.; Di Nitto, A.; Düllmann, Ch. E.; Fahlander, C.; Gates, J. M.; Golubev, P.; Gregorich, K. E.; Gross, C. J.; Herzberg, R.-D.; Heßberger, F. P.; Khuyagbaatar, J.; Kratz, J. V.; Rykaczewski, K.; Sarmiento, L. G.; Schädel, M.; Yakushev, A.; Åberg, S.; Ackermann, D.; Block, M.; Brand, H.; Carlsson, B. G.; Cox, D.; Derkx, X.; Dobaczewski, J.; Eberhardt, K.; Even, J.; Gerl, J.; Jäger, E.; Kindler, B.; Krier, J.; Kojouharov, I.; Kurz, N.; Lommel, B.; Mistry, A.; Mokry, C.; Nazarewicz, W.; Nitsche, H.; Omtvedt, J. P.; Papadakis, P.; Ragnarsson, I.; Runke, J.; Schaffner, H.; Schausten, B.; Shi, Yue; Thörle-Pospiech, P.; Torres, T.; Traut, T.; Trautmann, N.; Türler, A.; Ward, A.; Ward, D. E.; Wiehl, N.
2016-09-01
Products of the fusion-evaporation reaction 48Ca + 243Am were studied with the TASISpec set-up at the gas-filled separator TASCA at the GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt, Germany. Amongst the detected thirty correlated α-decay chains associated with the production of element Z = 115, two recoil-α-fission and five recoil- α- α-fission events were observed. The latter five chains are similar to four such events reported from experiments performed at the Dubna gas-filled separator, and three such events reported from an experiment at the Berkeley gas-filled separator. The four chains observed at the Dubna gas-filled separator were assigned to start from the 2n-evaporation channel 289115 due to the fact that these recoil- α- α-fission events were observed only at low excitation energies. Contrary to this interpretation, we suggest that some of these recoil- α- α-fission decay chains, as well as some of the recoil- α- α-fission and recoil-α-fission decay chains reported from Berkeley and in this article, start from the 3n-evaporation channel 288115.
Focus on quantum effects and noise in biomolecules
NASA Astrophysics Data System (ADS)
Fleming, G. R.; Huelga, S. F.; Plenio, M. B.
2011-11-01
The role of quantum mechanics in biological organisms has been a fundamental question of twentieth-century biology. It is only now, however, with modern experimental techniques, that it is possible to observe quantum mechanical effects in bio-molecular complexes directly. Indeed, recent experiments have provided evidence that quantum effects such as wave-like motion of excitonic energy flow, delocalization and entanglement can be seen even in complex and noisy biological environments (Engel et al 2007 Nature 446 782; Collini et al 2010 Nature 463 644; Panitchayangkoon et al 2010 Proc. Natl Acad. Sci. USA 107 12766). Motivated by these observations, theoretical work has highlighted the importance of an interplay between environmental noise and quantum coherence in such systems (Mohseni et al 2008 J. Chem. Phys. 129 174106; Plenio and Huelga 2008 New J. Phys. 10 113019; Olaya-Castro et al 2008 Phys. Rev. B 78 085115; Rebentrost et al 2009 New J. Phys. 11 033003; Caruso et al 2009 J. Chem. Phys. 131 105106; Ishizaki and Fleming 2009 J. Chem. Phys. 130 234111). All of this has led to a surge of interest in the exploration of quantum effects in biological systems in order to understand the possible relevance of non-trivial quantum features and to establish a potential link between quantum coherence and biological function. These studies include not only exciton transfer across light harvesting complexes, but also the avian compass (Ritz et al 2000 Biophys. J. 78 707), and the olfactory system (Turin 1996 Chem. Sens. 21 773; Chin et al 2010 New J. Phys. 12 065002). These examples show that the full understanding of the dynamics at bio-molecular length (10 Å) and timescales (sub picosecond) in noisy biological systems can uncover novel phenomena and concepts and hence present a fertile ground for truly multidisciplinary research.
Quantum effects in unimolecular reaction dynamics
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.
Nuclear recoil corrections to the Lamb shift of hydrogen and light hydrogenlike ions
NASA Astrophysics Data System (ADS)
Yerokhin, V. A.; Shabaev, V. M.
2016-06-01
Accurate calculations of the nuclear recoil effect on the Lamb shift of hydrogenlike atoms are presented. Numerical results are reported for the n s states with n ≤5 and for the 2 p1 /2 and 2 p3 /2 states. The calculations are performed to the first order in the electron-nucleus mass ratio and to all orders in the nuclear binding strength parameter Z α (where Z is the nuclear charge number and α is the fine structure constant). The obtained results provide accurate predictions for the higher-order remainder beyond the known Z α -expansion terms. In the case of hydrogen, the remainder was found to be much larger than anticipated. This result resolves the previously reported disagreement between the numerical all-order and the analytical Z α -expansion approaches for the nuclear recoil effect on the hydrogen Lamb shift.
Quantum effects and nonlocality in strongly coupled plasmonic nanowire dimers.
Teperik, Tatiana V; Nordlander, Peter; Aizpurua, Javier; Borisov, Andrei G
2013-11-01
Using a fully quantum mechanical approach we study the optical response of a strongly coupled metallic nanowire dimer for variable separation widths of the junction between the nanowires. The translational invariance of the system allows to apply the time-dependent density functional theory (TDDFT) for nanowires of diameters up to 10 nm which is the largest size considered so far in quantum modeling of plasmonic dimers. By performing a detailed analysis of the optical extinction, induced charge densities, and near fields, we reveal the major nonlocal quantum effects determining the plasmonic modes and field enhancement in the system. These effects consist mainly of electron tunneling between the nanowires at small junction widths and dynamical screening. The TDDFT results are compared with results from classical electromagnetic calculations based on the local Drude and non-local hydrodynamic descriptions of the nanowire permittivity, as well as with results from a recently developed quantum corrected model. The latter provides a way to include quantum mechanical effects such as electron tunneling in standard classical electromagnetic simulations. We show that the TDDFT results can be thus retrieved semi-quantitatively within a classical framework. We also discuss the shortcomings of classical non-local hydrodynamic approaches. Finally, the implications of the actual position of the screening charge density at the gap interfaces are discussed in connection with plasmon ruler applications at subnanometric distances.
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.).
Proton Conductivity in Phosphoric Acid: The Role of Quantum Effects
NASA Astrophysics Data System (ADS)
Heres, M.; Wang, Y.; Griffin, P. J.; Gainaru, C.; Sokolov, A. P.
2016-10-01
Phosphoric acid has one of the highest intrinsic proton conductivities of any known liquids, and the mechanism of this exceptional conductivity remains a puzzle. Our detailed experimental studies discovered a strong isotope effect in the conductivity of phosphoric acids caused by (i) a strong isotope shift of the glass transition temperature and (ii) a significant reduction of the energy barrier by zero-point quantum fluctuations. These results suggest that the high conductivity in phosphoric acids is caused by a very efficient proton transfer mechanism, which is strongly assisted by quantum effects.
Modeling quantum gravity effects in inflation
NASA Astrophysics Data System (ADS)
Martinec, Emil J.; Moore, Wynton E.
2014-07-01
Cosmological models in 1+1 dimensions are an ideal setting for investigating the quantum structure of inflationary dynamics — gravity is renormalizable, while there is room for spatial structure not present in the minisuperspace approximation. We use this fortuitous convergence to investigate the mechanism of slow-roll eternal inflation. A variant of 1+1 Liouville gravity coupled to matter is shown to model precisely the scalar sector of cosmological perturbations in 3+1 dimensions. A particular example of quintessence in 1+1d is argued on the one hand to exhibit slow-roll eternal inflation according to standard criteria; on the other hand, a field redefinition relates the model to pure de Sitter gravity coupled to a free scalar matter field with no potential. This and other examples show that the standard logic leading to slow-roll eternal inflation is not invariant under field redefinitions, thus raising concerns regarding its validity. Aspects of the quantization of Liouville gravity as a model of quantum de Sitter space are also discussed.
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.
Analysis of the quantum Zeno effect for quantum control and computation
NASA Astrophysics Data System (ADS)
Dominy, Jason M.; Paz-Silva, Gerardo A.; Rezakhani, A. T.; Lidar, D. A.
2013-02-01
Within quantum information, many methods have been proposed to avoid or correct the deleterious effects of the environment on a system of interest. In this work, expanding on our earlier paper (Paz-Silva et al 2012 Phys. Rev. Lett. 108 080501), we evaluate the applicability of the quantum Zeno effect as one such method. Using the algebraic structure of stabilizer quantum error correction codes as a unifying framework, two open-loop protocols are described which involve frequent non-projective (i.e. weak) measurement of either the full stabilizer group or a minimal generating set thereof. The effectiveness of the protocols is measured by the distance between the final state under the protocol and the final state of an idealized evolution in which system and environment do not interact. Rigorous bounds on this metric are derived which demonstrate that, under certain assumptions, a Zeno effect may be realized with arbitrarily weak measurements, and that this effect can protect an arbitrary, unknown encoded state against the environment arbitrarily well.
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
Effective quantum gravity observables and locally covariant QFT
NASA Astrophysics Data System (ADS)
Rejzner, Kasia
2016-03-01
Perturbative algebraic quantum field theory (pAQFT) is a mathematically rigorous framework that allows to construct models of quantum field theories (QFTs) on a general class of Lorentzian manifolds. Recently, this idea has been applied also to perturbative quantum gravity (QG), treated as an effective theory. The difficulty was to find the right notion of observables that would in an appropriate sense be diffeomorphism invariant. In this paper, I will outline a general framework that allows to quantize theories with local symmetries (this includes infinitesimal diffeomorphism transformations) with the use of the Batalin-Vilkovisky (BV) formalism. This approach has been successfully applied to effective QG in a recent paper by Brunetti, Fredenhagen and myself. In the same paper, we also proved perturbative background independence of the quantized theory, which is going to be discussed in the present work as well.
Pseudorelativistic effects on solitons in quantum semiconductor plasma
NASA Astrophysics Data System (ADS)
Wang, Yunliang; Wang, Xiaodan; Jiang, Xiangqian
2015-04-01
A theory for nonlinear excitations in quantum plasmas is presented for narrow-gap semiconductors by considering the combined effects of quantum and pseudorelativity. The system is governed by a coupled Klein-Gordon equation for the collective wave functions of the conduction electrons and Poisson's equation for the electrostatic potential. This gives a closed system, including the effects of charge separation, quantum tunneling, and pseudorelativity. By choosing the typical parameters of semiconductor InSb, the quasistationary soliton solution, which is a multipeaked dark soliton, is obtained numerically and shows depleted electron densities correlated with a localized potential. The dynamical simulation result shows that the dark soliton is stable and has a multipeaked profile, which is consistent with the quasistationary solution. The present model and results may be useful in understanding the nonlinear properties of semiconductor plasma on an ultrafast time scale.
Pseudorelativistic effects on solitons in quantum semiconductor plasma.
Wang, Yunliang; Wang, Xiaodan; Jiang, Xiangqian
2015-04-01
A theory for nonlinear excitations in quantum plasmas is presented for narrow-gap semiconductors by considering the combined effects of quantum and pseudorelativity. The system is governed by a coupled Klein-Gordon equation for the collective wave functions of the conduction electrons and Poisson's equation for the electrostatic potential. This gives a closed system, including the effects of charge separation, quantum tunneling, and pseudorelativity. By choosing the typical parameters of semiconductor InSb, the quasistationary soliton solution, which is a multipeaked dark soliton, is obtained numerically and shows depleted electron densities correlated with a localized potential. The dynamical simulation result shows that the dark soliton is stable and has a multipeaked profile, which is consistent with the quasistationary solution. The present model and results may be useful in understanding the nonlinear properties of semiconductor plasma on an ultrafast time scale.
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.
Quantum effects in ultrafast electron transfers within cryptochromes.
Firmino, Thiago; Mangaud, Etienne; Cailliez, Fabien; Devolder, Adrien; Mendive-Tapia, David; Gatti, Fabien; Meier, Christoph; Desouter-Lecomte, Michèle; de la Lande, Aurélien
2016-08-21
Cryptochromes and photolyases are flavoproteins that may undergo ultrafast charge separation upon electronic excitation of their flavin cofactors. Charge separation involves chains of three or four tryptophan residues depending on the protein of interest. The molecular mechanisms of these processes are not completely clear. In the present work we investigate the relevance of quantum effects like the occurrence of nuclear tunneling and of coherences upon charge transfer in Arabidopsis thaliana cryptochromes. The possible breakdown of the Condon approximation is also investigated. We have devised a simulation protocol based on the realization of molecular dynamics simulations on diabatic potential energy surfaces defined at the hybrid constrained density functional theory/molecular mechanics level. The outcomes of the simulations are analyzed through various dedicated kinetics schemes related to the Marcus theory that account for the aforementioned quantum effects. MD simulations also provide a basic material to define realistic model Hamiltonians for subsequent quantum dissipative dynamics. To carry out quantum simulations, we have implemented an algorithm based on the Hierarchical Equations of Motion. With this new tool in hand we have been able to model the electron transfer chain considering either two- or three-state models. Kinetic models and quantum simulations converge to the conclusion that quantum effects have a significant impact on the rate of charge separation. Nuclear tunneling involving atoms of the tryptophan redox cofactors as well as of the environment (protein atoms and water molecules) is significant. On the other hand non-Condon effects are negligible in most simulations. Taken together, the results of the present work provide new insights into the molecular mechanisms controlling charge separation in this family of flavoproteins. PMID:27427185
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.
A coherent understanding of low-energy nuclear recoils in liquid xenon
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.
A predictive theory for elastic scattering and recoil of protons from ^{4}He
Hupin, Guillaume; Quaglioni, Sofia; Navratil, Petr
2014-12-08
Low-energy cross sections for elastic scattering and recoil of protons from ^{4}He nuclei (also known as α particles) are calculated directly by solving the Schrodinger 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. Furthermore, 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.
A predictive theory for elastic scattering and recoil of protons from 4He
Hupin, Guillaume; Quaglioni, Sofia; Navratil, Petr
2014-12-08
Low-energy cross sections for elastic scattering and recoil of protons from 4He nuclei (also known as α particles) are calculated directly by solving the Schrodinger 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 ofmore » either hydrogen or helium. Furthermore, 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.« less
Recoil excitation of vibrational structure in the carbon 1s photoelectron spectrum of CF4.
Thomas, T Darrah; Kukk, Edwin; Sankari, Rami; Fukuzawa, Hironobu; Prümper, Georg; Ueda, Kiyoshi; Püttner, Ralph; Harries, James; Tamenori, Yusuke; Tanaka, Takahiro; Hoshino, Masamitsu; Tanaka, Hiroshi
2008-04-14
The carbon 1s photoelectron spectrum of CF4 measured at photon energies from 330 to 1500 eV shows significant contributions from nonsymmetric vibrational modes. These increase linearly as the photon energy increases. The excitation of these modes, which is not predicted in the usual Franck-Condon point of view, arises from the recoil momentum imparted to the carbon atom in the ionization process. A theory is presented for quantitative prediction of the recoil effect; the predictions of this theory are in agreement to the measurements. The experiments also yield the vibrational frequencies of the symmetric and asymmetric stretching modes in core-ionized CF4, the change in CF bond length upon ionization, -0.61 pm, and the Lorentzian linewidth of the carbon 1s hole, 67 meV.
A coherent understanding of low-energy nuclear recoils in liquid xenon
NASA Astrophysics Data System (ADS)
Sorensen, Peter
2010-09-01
Liquid xenon detectors such as XENON10 and XENON100 obtain a significant fraction of their sensitivity to light (lesssim10 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.
Quantum Einstein-de Haas effect
Ganzhorn, Marc; Klyatskaya, Svetlana; Ruben, Mario; Wernsdorfer, Wolfgang
2016-01-01
The classical Einstein-de Haas experiment demonstrates that a change of magnetization in a macroscopic magnetic object results in a mechanical rotation of this magnet. This experiment can therefore be considered as a macroscopic manifestation of the conservation of total angular momentum and energy of electronic spins. Since the conservation of angular momentum is a consequence of a system's rotational invariance, it is valid for an ensemble of spins in a macroscopic ferromaget as well as for single spins. Here we propose an experimental realization of an Einstein-de Haas experiment at the single-spin level based on a single-molecule magnet coupled to a nanomechanical resonator. We demonstrate that the spin associated with the single-molecule magnet is then subject to conservation of total angular momentum and energy, which results in a total suppression of the molecule's quantum tunnelling of magnetization. PMID:27126449
Quantum Einstein-de Haas effect.
Ganzhorn, Marc; Klyatskaya, Svetlana; Ruben, Mario; Wernsdorfer, Wolfgang
2016-01-01
The classical Einstein-de Haas experiment demonstrates that a change of magnetization in a macroscopic magnetic object results in a mechanical rotation of this magnet. This experiment can therefore be considered as a macroscopic manifestation of the conservation of total angular momentum and energy of electronic spins. Since the conservation of angular momentum is a consequence of a system's rotational invariance, it is valid for an ensemble of spins in a macroscopic ferromaget as well as for single spins. Here we propose an experimental realization of an Einstein-de Haas experiment at the single-spin level based on a single-molecule magnet coupled to a nanomechanical resonator. We demonstrate that the spin associated with the single-molecule magnet is then subject to conservation of total angular momentum and energy, which results in a total suppression of the molecule's quantum tunnelling of magnetization.
The Quantum Spin Hall Effect: Theory and Experiment
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.
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.
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.
Mesoscopic effects in quantum phases of ultracold quantum gases in optical lattices
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.
Quantum effects in the dynamics of deeply supercooled water
Agapov, Alexander L.; Kolesnikov, Alexander I.; Novikov, Vladimir N.; Richert, Ranko; Sokolov, Alexei P
2015-02-26
In spite of 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. In conclusion, these results have significant implications for our understanding of water dynamics.
Quantum effects in the dynamics of deeply supercooled water
Agapov, Alexander L.; Kolesnikov, Alexander I.; Novikov, Vladimir N.; Richert, Ranko; Sokolov, Alexei P
2015-02-26
In spite of 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 Tg~136K. We demonstrate that this anomalous behavior can be explained well by quantum effects. In conclusion, these results have significant implications for our understanding of water dynamics.
Effective photon mass and exact translating quantum relativistic structures
NASA Astrophysics Data System (ADS)
Haas, Fernando; Manrique, Marcos Antonio Albarracin
2016-04-01
Using a variation of the celebrated Volkov solution, the Klein-Gordon equation for a charged particle is reduced to a set of ordinary differential equations, exactly solvable in specific cases. The new quantum relativistic structures can reveal a localization in the radial direction perpendicular to the wave packet propagation, thanks to a non-vanishing scalar potential. The external electromagnetic field, the particle current density, and the charge density are determined. The stability analysis of the solutions is performed by means of numerical simulations. The results are useful for the description of a charged quantum test particle in the relativistic regime, provided spin effects are not decisive.
Analog model for quantum gravity effects: phonons in random fluids.
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.
Nuclear Quantum Vibrational Effects in Shock Hugoniot Temperatures
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.
Apparent quantum efficiency effects in CdTe solar cells
NASA Astrophysics Data System (ADS)
Gloeckler, M.; Sites, J. R.
2004-04-01
Quantum efficiency measurements of n-CdS/p-CdTe solar cells performed under nonstandard illumination, voltage bias, or both can be severely distorted by photogeneration and contact-barrier effects. In this work we will discuss the effects that are typically observed, the requirements needed to reproduce these effects with modeling tools, and the potential applications of apparent quantum efficiency analysis. Recently published experimental results are interpreted and reproduced using numerical simulation tools. The suggested model explains large negative apparent quantum efficiencies (≫100%) seen in the spectral range of 350-550 nm, modestly large negative apparent quantum efficiencies (>100%) in the spectral range of 800-850 nm, enhanced positive or negative response observed under red, blue, and white light bias, and photocurrent gain significantly different from unity. Some of these effects originate from the photogeneration in the highly compensated CdS window layer, some from photogeneration within the CdTe, and some are further modified by the height of the CdTe back-contact barrier.
Subvacuum effects in quantum critical theories from a holographic approach
NASA Astrophysics Data System (ADS)
Yeh, Chen-Pin; Lee, Da-Shin
2016-06-01
The subvacuum phenomena, induced by the squeezed vacuum of the strongly coupled quantum critical fields with a dynamical scaling z , are explored by a probe particle. The holographic description corresponds to a string moving in (4 +1 )-dimensional Lifshitz geometry with gravitational wave perturbations. The dynamics of the particle can be realized from the motion of the endpoint of the string at the boundary. We then examine the particle's velocity dispersion, influenced by the squeezed vacuum states of strongly coupled quantum critical fields. With appropriate choices of squeezing parameters, the velocity dispersion is found to be smaller than the value caused by the normal vacuum fluctuations of the fields. This leads to the subvacuum effect. We find that the large coupling constant of the quantum fields tends to counteract the effect in the reduction of velocity dispersion, though this phenomenon is in principle observable. The effect of the squeezed vacuum on the decoherence dynamics of a quantum particle is also investigated. Coherence loss can be shown to be less severe in certain squeezed vacuums than in normal vacuum. This recovery of coherence is understood as recoherence, another manifestation of the subvacuum phenomena. We make some estimates of the degree of recoherence and find that, contrary to the velocity dispersion case, the recoherence effect is enhanced by the large coupling constant. Finally we compare the findings in our earlier works when the particle is influenced by a weakly coupled relativistic field with the dynamical scaling z =1 .
High-order primordial perturbations with quantum gravitational effects
NASA Astrophysics Data System (ADS)
Zhu, Tao; Wang, Anzhong; Kirsten, Klaus; Cleaver, Gerald; Sheng, Qin
2016-06-01
In this paper, we provide a systematic investigation of high-order primordial perturbations with nonlinear dispersion relations due to quantum gravitational effects in the framework of uniform asymptotic approximations. Because of these effects, the equation of motion of the mode function in general has multiple turning points. After obtaining analytically approximated solutions to any order in different regions, associated with different types of turning points, we match them to the third one. To this order the errors are less than 0.15%. General expressions of the power spectra of the primordial tensor and scalar perturbations are derived explicitly. We also investigate effects of backreactions of the quantum gravitational corrections, and make sure that inflation lasts long enough in order to solve the underlying problems, such as flatness, horizon, and monopole. Then we study various features of the spectra that are observationally relevant. In particular, under a moderate assumption about the energy scale of the underlying theory of quantum gravity, we have shown that the quantum gravitational effects may alter significantly the ratio between the tensor and scalar power spectra, thereby providing a natural mechanism to alleviate the tension between observations and certain inflationary models, including the one with a quadratic potential.
On the Convergence in Effective Loop Quantum Cosmology
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.
Recoil separator ERNA: acceptances in angle and energy
NASA Astrophysics Data System (ADS)
Rogalla, D.; Schürmann, D.; Strieder, F.; Aliotta, M.; DeCesare, N.; DiLeva, A.; Lubritto, C.; D'Onofrio, A.; Gialanella, L.; Imbriani, G.; Kluge, J.; Ordine, A.; Roca, V.; Röcken, H.; Rolfs, C.; Romano, M.; Schümann, F.; Terrasi, F.; Trautvetter, H. P.
2003-11-01
For improved cross-section measurements of the reaction 12C(α,γ) 16O in inverted kinematics, a recoil separator ERNA is developed at the 4 MV Dynamitron tandem accelerator in Bochum to detect directly the 16O recoils with high efficiency. Due to the emission of the capture γ-rays, the kinematically forward directed 16O recoils are described by an angle and energy spread. Thus, the acceptances in angle and energy of ERNA must cover these spreads in order to extract reliable cross-section values. We report on such acceptance measurements over the energy range Ecm=0.7-5.0 MeV, using an 16O pilot beam.
Nuclear Recoil Calibration of DarkSide-50
NASA Astrophysics Data System (ADS)
Edkins, Erin; DarkSide Collaboration
2016-03-01
DarkSide-50 dark matter experiment is a liquid argon time projection chamber (TPC) surrounded by a liquid scintillator active neutron veto, designed for the direct detection of Weakly Interacting Massive Particles (WIMPs). The success of such an experiment is dependent upon a detailed understanding of both the expected signal and backgrounds, achieved using radioactive calibration sources of known energies. Nuclear recoils provide a measurement of both the expected signal and the most dangerous background, as nuclear recoils from neutrons cannot be distinguished from a dark matter signal on an event-by-event basis in the TPC. In this talk, I will present the DS-50 calibration system, and analysis of the results of the calibration of DarkSide-50 to nuclear recoils using radioactive neutron sources. See also the DS-50 presentations by X. Xiang and G. Koh.
Rupture and recoil of bent-core liquid crystal filaments.
Salili, S M; Ostapenko, T; Kress, O; Bailey, C; Weissflog, W; Harth, K; Eremin, A; Stannarius, R; Jákli, A
2016-05-25
The recoil process of free-standing liquid crystal filaments is investigated experimentally and theoretically. We focus on two aspects, the contraction speed of the filament and a spontaneously formed undulation instability. At the moment of rupture, the filaments buckle similarly to the classical Euler buckling of elastic rods. The tip velocity decays with decreasing filament length. The wavelength of buckling affinely decreases with the retracting filament tip. The energy gain related to the decrease of the total length and surface area of the filaments is mainly dissipated by layer rearrangements during thickening of the fibre. A flow back into the meniscus is relevant only in the final stage of the recoil process. We introduce a model for the quantitative description of the filament retraction speed. The dynamics of this recoil behaviour may find relevance as a model for biology-related filaments. PMID:27140824
Li, Hai; Zou, Jian; Yu, Wen-Li; Xu, Bao-Ming; Li, Jun-Gang; Shao, Bin
2014-05-01
We consider a model of an optical cavity with a nonequilibrium reservoir consisting of a beam of identical two-level atom pairs (TLAPs) in the general X state. We find that coherence of multiparticle nonequilibrium reservoir plays a central role on the potential work capability of the cavity. We show that no matter whether there are quantum correlations in each TLAP (including quantum entanglement and quantum discord) or not, the coherence of the TLAPs has an effect on the work capability of the cavity. Additionally, constructive and destructive interferences could be induced to influence the work capability of the cavity by adjusting only the relative phase, with which quantum correlations have nothing to do. In this paper, the coherence of the reservoir, rather than the quantum correlations, effectively reflecting the effects of the reservoir on the system's work capability is demonstrated clearly. PMID:25353764
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.
Accelerating quantum instanton calculations of the kinetic isotope effects
Karandashev, Konstantin; Vaníček, Jiří
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{sub α} + H{sub β}H{sub γ} → H{sub α}H{sub β} + ⋅ H{sub γ} reaction as an example, we apply the proposed method to obtain several kinetic isotope effects on CH{sub 4} + ⋅ H ⇌ ⋅ CH{sub 3} + H{sub 2} forward and backward reactions.
Possible observational windows for quantum effects from black holes
NASA Astrophysics Data System (ADS)
Giddings, Steven B.
2014-12-01
Quantum information transfer necessary to reconcile black hole evaporation with quantum mechanics, while approximately preserving regular near-horizon geometry, can be simply parametrized in terms of couplings of the black hole internal state to quantum fields of the black hole atmosphere. The necessity of transferring sufficient information for unitarization sets the strengths of these couplings. Such couplings via the stress tensor offer apparently significant advantages, and behave like quantum fluctuations of the effective metric near the horizon. At the requisite strength, these fluctuations, while soft (low energy/momentum), have significant magnitude, and so can deflect near-horizon geodesics that span distances of order the black hole radius. Thus, the presence of such couplings can result in effects that could be detected or constrained by observation: disruption of near-horizon accretion flows, scintillation of light passing close to the black hole, and alteration of gravitational wave emission from inspirals. These effects could in particular distort features of Sgr A* expected to be observed, e.g., by the Event Horizon Telescope, such as the black hole shadow and photon ring.
Photodynamic antibacterial effect of graphene quantum dots.
Ristic, Biljana Z; Milenkovic, Marina M; Dakic, Ivana R; Todorovic-Markovic, Biljana M; Milosavljevic, Momir S; Budimir, Milica D; Paunovic, Verica G; Dramicanin, Miroslav D; Markovic, Zoran M; Trajkovic, Vladimir S
2014-05-01
Synthesis of new antibacterial agents is becoming increasingly important in light of the emerging antibiotic resistance. In the present study we report that electrochemically produced graphene quantum dots (GQD), a new class of carbon nanoparticles, generate reactive oxygen species when photoexcited (470 nm, 1 W), and kill two strains of pathogenic bacteria, methicillin-resistant Staphylococcus aureus and Escherichia coli. Bacterial killing was demonstrated by the reduction in number of bacterial colonies in a standard plate count method, the increase in propidium iodide uptake confirming the cell membrane damage, as well as by morphological defects visualized by atomic force microscopy. The induction of oxidative stress in bacteria exposed to photoexcited GQD was confirmed by staining with a redox-sensitive fluorochrome dihydrorhodamine 123. Neither GQD nor light exposure alone were able to cause oxidative stress and reduce the viability of bacteria. Importantly, mouse spleen cells were markedly less sensitive in the same experimental conditions, thus indicating a fairly selective antibacterial photodynamic action of GQD.
Ir Wavelength Dependence Quantum Size Effects in Nb/SiO2 Quantum Wells
NASA Astrophysics Data System (ADS)
Villagómez, R.
This letter deals with the experimental observation of oscillations in the infrared reflectance from Nb ultra-thin films deposited on α-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 μm. Several Nb/SiO2 quantum wells were specially made by the RF sputtering technique. Tailored thicknesses run between 5.5 and 55 Å. 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.
Quantum simulation of conductivity plateaux and fractional quantum Hall effect using ultracold atoms
NASA Astrophysics Data System (ADS)
Barberán, Nuria; Dagnino, Daniel; García-March, Miguel Angel; Trombettoni, Andrea; Taron, Josep; Lewenstein, Maciej
2015-12-01
We analyze the role of impurities in the fractional quantum Hall effect using a highly controllable system of ultracold atoms. We investigate the mechanism responsible for the formation of plateaux in the resistivity/conductivity as a function of the applied magnetic field in the lowest Landau level regime. To this aim, we consider an impurity immersed in a small cloud of an ultracold quantum Bose gas subjected to an artificial magnetic field. We consider scenarios corresponding to experimentally realistic systems with gauge fields induced by rotation of the trapping parabolic potential. Systems of this kind are adequate to simulate quantum Hall effects in ultracold atom setups. We use exact diagonalization for few atoms and to emulate transport equations, we analyze the time evolution of the system under a periodic perturbation. We provide a theoretical proposal to detect the up-to-now elusive presence of strongly correlated states related to fractional filling factors in the context of ultracold atoms. We analyze the conditions under which these strongly correlated states are associated with the presence of the resistivity/conductivity plateaux. Our main result is the presence of a plateau in a region, where the transfer between localized and non-localized particles takes place, as a necessary condition to maintain a constant value of the resistivity/conductivity as the magnetic field increases.
Quantum well intermixing and radiation effects in InGaN/GaN multi quantum wells
NASA Astrophysics Data System (ADS)
Lorenz, K.; Redondo-Cubero, A.; Lourenço, M. B.; Sequeira, M. C.; Peres, M.; Freitas, A.; Alves, L. C.; Alves, E.; Leitão, M. P.; Rodrigues, J.; Ben Sedrine, N.; Correia, M. R.; Monteiro, T.
2016-02-01
Compositional grading of InGaN/GaN multi quantum wells (QWs) was proposed to mitigate polarization effects and Auger losses in InGaN-based light emitting diodes [K. P. O'Donnell et al., Phys. Status Solidi RRL 6 (2012) 49]. In this paper we are reviewing our recent attempts on achieving such gradient via quantum well intermixing. Annealing up to 1250 °C resulted in negligible interdiffusion of QWs and barriers revealing a surprising thermal stability well above the typical MOCVD growth temperatures. For annealing at 1400 °C results suggest a decomposition of the QWs in regions with high and low InN content. The defect formation upon nitrogen implantation was studied in detail. Despite strong dynamic annealing effects, which keep structural damage low, the created defects strongly quench the QW luminescence even for low implantation fluences. This degradation could not be reversed during thermal annealing and is hampering the use of implantation induced quantum well intermixing in InGaN/GaN structures.
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.
Quantum interference effect in electron tunneling through a quantum-dot-ring spin valve.
Ma, Jing-Min; Zhao, Jia; Zhang, Kai-Cheng; Peng, Ya-Jing; Chi, Feng
2011-01-01
Spin-dependent transport through a quantum-dot (QD) ring coupled to ferromagnetic leads with noncollinear magnetizations is studied theoretically. Tunneling current, current spin polarization and tunnel magnetoresistance (TMR) as functions of the bias voltage and the direct coupling strength between the two leads are analyzed by the nonequilibrium Green's function technique. It is shown that the magnitudes of these quantities are sensitive to the relative angle between the leads' magnetic moments and the quantum interference effect originated from the inter-lead coupling. We pay particular attention on the Coulomb blockade regime and find the relative current magnitudes of different magnetization angles can be reversed by tuning the inter-lead coupling strength, resulting in sign change of the TMR. For large enough inter-lead coupling strength, the current spin polarizations for parallel and antiparallel magnetic configurations will approach to unit and zero, respectively.PACS numbers: PMID:21711779
Recoil velocity at second post-Newtonian order for spinning black hole binaries
NASA Astrophysics Data System (ADS)
Racine, Étienne; Buonanno, Alessandra; Kidder, Larry
2009-08-01
We compute the flux of linear momentum carried by gravitational waves emitted from spinning binary black holes at second post-Newtonian (2PN) order for generic orbits. In particular we provide explicit expressions of three new types of terms, namely, next-to-leading order spin-orbit terms at 1.5 post-Newtonian (1.5PN) order, spin-orbit tail terms at 2PN order, and spin-spin terms at 2PN order. Restricting ourselves to quasicircular orbits, we integrate the linear-momentum flux over time to obtain the recoil velocity as function of orbital frequency. We find that in the so-called superkick configuration the higher-order spin corrections can increase the recoil velocity up to a factor ˜3 with respect to the leading-order PN prediction. Whereas the recoil velocity computed in PN theory within the adiabatic approximation can accurately describe the early inspiral phase, we find that its fast increase during the late inspiral and plunge, and the arbitrariness in determining until when it should be trusted, makes the PN predictions for the total recoil not very accurate and robust. Nevertheless, the linear-momentum flux at higher PN orders can be employed to build more reliable resummed expressions aimed at capturing the nonperturbative effects until merger. Furthermore, we provide expressions valid for generic orbits, and accurate at 2PN order, for the energy and angular momentum carried by gravitational waves emitted from spinning binary black holes. Specializing to quasicircular orbits we compute the spin-spin terms at 2PN order in the expression for the evolution of the orbital frequency and found agreement with Mikóczi, Vasúth, and Gergely. We also verified that in the limit of extreme mass ratio our expressions for the energy and angular momentum fluxes match the ones of Tagoshi, Shibata, Tanaka, and Sasaki obtained in the context of black hole perturbation theory.
NASA Astrophysics Data System (ADS)
Liu, Z. W.; Huang, Y. L.; Hu, S. L.; Zhong, X. C.; Y Yu, H.; Gao, X. X.
2014-06-01
Nanocrystalline NdFeB magnets were prepared by spark plasma sintering (SPS) and SPS followed by HD using melt spun ribbons as the starting materials. The microstructure of SPSed and HDed magnets were analyzed. The effects of process including temperature and compression ratio on the microstructure and properties were investigated. High magnetic properties were obtained in anisotropic HDed magnets. The combination of Zn and Dy additions was successfully employed to improve the coercivity and thermal stability of the SPSed magnets. Open recoil loops were found in these magnets with Nd-rich composition and without soft magnetic phase for the first time. The relationship between the recoil loops and microstructure for SPS and HD NdFeB magnets were investigated. The investigations showed that the magnetic properties of SPS+HDed magnets are related to the extent of the aggregation of Nd-rich phase, which was formed during HD due to existence of porosity in SPSed precursor. Large local demagnetization fields induced by the Nd-rich phase aggregation leads to the open loops and significantly reduced the coercivity. By reducing the recoil loop openness, the magnetic properties of HDed NdFeB magnets were successfully improved.
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.
Accurate hydrogen depth profiling by reflection elastic recoil detection analysis
Verda, R. D.; Tesmer, Joseph R.; Nastasi, Michael Anthony,; Bower, R. W.
2001-01-01
A technique to convert reflection elastic recoil detection analysis spectra to depth profiles, the channel-depth conversion, was introduced by Verda, et al [1]. But the channel-depth conversion does not correct for energy spread, the unwanted broadening in the energy of the spectra, which can lead to errors in depth profiling. A work in progress introduces a technique that corrects for energy spread in elastic recoil detection analysis spectra, the energy spread correction [2]. Together, the energy spread correction and the channel-depth conversion comprise an accurate and convenient hydrogen depth profiling method.
Vortices in superconducting films: Statistics and fractional quantum Hall effect
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.}
Quantum spin Hall effect in nanostructures based on cadmium fluoride
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.
Hall effect in quantum critical charge-cluster glass
Bozovic, Ivan; Wu, Jie; Bollinger, Anthony T.; Sun, Yujie
2016-04-04
Upon doping, cuprates undergo a quantum phase transition from an insulator to a d-wave superconductor. The nature of this transition and of the insulating state is vividly debated. Here, we study the Hall effect in La2-xSrxCuO4 (LSCO) samples doped near the quantum critical point at x ≈ 0.06. Dramatic fluctuations in the Hall resistance appear below TCG ≈ 1.5 K and increase as the sample is cooled down further, signaling quantum critical behavior. We explore the doping dependence of this effect in detail, by studying a combinatorial LSCO library in which the Sr content is varied in extremely fine steps,more » Δx ≈ 0.00008. Furthermore, we observe that quantum charge fluctuations wash out when superconductivity emerges but can be restored when the latter is suppressed by applying a magnetic field, showing that the two instabilities compete for the ground state.« less
Effective equations of cosmological models in (loop) quantum gravity
NASA Astrophysics Data System (ADS)
Simpson, David
This dissertation focuses on the properties of several differing models within quantum cosmology. Specifically, by using the method of effective equations, we explore: a linear discrete Schrodinger model, a non-linear discrete Schrodinger model, factor ordering ambiguities in the Hamiltonian constraint (with a focus on large-volume behavior), and the use of the electric vector potential as deparameterized time. In the linear and non-linear Schrodinger models, we arrive at a new possibility for studying inhomogeneous quantum cosmology (where the non-linearities are interpreted as non-local deviations from the spatial average) that allows for a variety of dynamics and raises a number of questions for future research. We then turn our focus to the general effects of factor ordering ambiguities and their possible role in large-volume collapse of a k = 0 isotropic quantum cosmology with a free, massless scalar field. With the additional inclusion of holonomy and inverse-triad corrections, the choice in factor ordering of the Hamiltonian constraint is quite relevant; however, with our assumptions, we do not see any significant departure from classical large-volume behavior. The final model discussed is formulated with the electric vector potential as the global internal time in a Wheeler-DeWitt setting sourced by radiation. While further analysis is required to make a definitive statement on the impact that the choice of deparameterization makes, we find that the specific form of quantum state can affect early-universe dynamics and even lead to new possibilities.
Electromagnetic quantum effects in higher-dimensional cosmological models
NASA Astrophysics Data System (ADS)
Kotanjyan, Anna; Sargsyan, Hayk; Simonyan, David; Saharian, Aram
2016-07-01
Among the most interesting directions in quantum field theory on curved spacetimes is the investigation of the influence of the gravitational field on the properties of the quantum vacuum. The corresponding problems are exactly solvable for highly symmetric background geometries only. In particular, the investigations of quantum effects in de Sitter (dS) and anti-de Sitter (AdS) spacetimes have attracted a great deal of attention. We consider electromagnetic quantum effects in higher-dimensional cosmological models. The two-point functions of the vector potential and of the field tensor for the electromagnetic field in background of dS and AdS spacetime are evaluated in arbitrary number of spatial dimensions. First we consider the two-point functions in the boundary-free geometry and then generalize the results in the presence of a reflecting boundary, for AdS spacetimes parallel to the AdS horizon. By using the expressions for the two-point functions of the field tensor, we investigate the vacuum expectation values of the electric field squared and of the energy-momentum tensor. Simple asymptotic expressions are provided for both cases, in particular for AdS geometry near the AdS boundary and horizon.
Cotunneling Drag Effect in Coulomb-Coupled Quantum Dots.
Keller, A J; Lim, J S; Sánchez, David; López, Rosa; Amasha, S; Katine, J A; Shtrikman, Hadas; Goldhaber-Gordon, D
2016-08-01
In Coulomb drag, a current flowing in one conductor can induce a voltage across an adjacent conductor via the Coulomb interaction. The mechanisms yielding drag effects are not always understood, even though drag effects are sufficiently general to be seen in many low-dimensional systems. In this Letter, we observe Coulomb drag in a Coulomb-coupled double quantum dot and, through both experimental and theoretical arguments, identify cotunneling as essential to obtaining a correct qualitative understanding of the drag behavior.
Cotunneling Drag Effect in Coulomb-Coupled Quantum Dots
NASA Astrophysics Data System (ADS)
Keller, A. J.; Lim, J. S.; Sánchez, David; López, Rosa; Amasha, S.; Katine, J. A.; Shtrikman, Hadas; Goldhaber-Gordon, D.
2016-08-01
In Coulomb drag, a current flowing in one conductor can induce a voltage across an adjacent conductor via the Coulomb interaction. The mechanisms yielding drag effects are not always understood, even though drag effects are sufficiently general to be seen in many low-dimensional systems. In this Letter, we observe Coulomb drag in a Coulomb-coupled double quantum dot and, through both experimental and theoretical arguments, identify cotunneling as essential to obtaining a correct qualitative understanding of the drag behavior.
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.
Super quantum measures on effect algebras with the Riesz decomposition properties
Xie, Yongjian Ren, Fang; Yang, Aili
2015-10-15
We give one basis of the space of super quantum measures on finite effect algebras with the Riesz decomposition properties (RDP for short). Then we prove that the super quantum measures and quantum interference functions on finite effect algebras with the RDP are determined each other. At last, we investigate the relationships between the super quantum measures and the diagonally positive signed measures on finite effect algebras with the RDP in detail.
Quantum electrodynamic effects in finite space
NASA Astrophysics Data System (ADS)
Dobiasch, P.; Walther, H.
The modifications of various quantum properties due to a discrete structure of the modes of the vacuum electromagnetic field are discussed. In contrast to the usual case of a continuous spectrum of the free space fluctuations, we consider physical systems in a resonator or in a wave guide. It is shown that the relaxation time of the system can be increased ot decreased, by increasing or decreasing the density of modes with respect to the case of unperturbed vacuum. On the other hand, we predict level shifts due to the reduced mass of the electron and deviations from the Lambshift for hydrogen in a wave guide, which can be detected with the presently feasible high resolution spectroscopy. We propose an experimental set-up. Nous discutons les modifications de diverses propriétés quantiques sous l'influence d'une structure de modes discrets du champ électromagnétique dans le vide. En comparaison du cas habituel d'un spectre continu des fluctuations du vide dans l'espace libre, nous considérons ici des systèmes physiques dans un résonateur ou un guide d'ondes. Il est démontré que le temps de relaxation du système peut être prolongé ou raccourci, ceci en augmentant ou diminuant la densité des modes par rapport à sa valeur dans le vide non-perturbé. D'autre part, nous prédisons des déplacements de niveau dus à la masse réduite de l'électron et des déviations du Lamb shift pour des atomes d'hydrogène dans un guide d'ondes, qui peuvent être détectées grâce à la haute résolution accessible actuellement en spectroscopie. Nous présentons un dispositif expérimental.
Experimental superradiance and slow-light effects for quantum memories
Walther, A.; Amari, A.; Kroell, S.; Kalachev, A.
2009-07-15
The effects of high optical depth phenomena, such as superradiance, are investigated in potential quantum memory materials. The results may have relevance for several schemes, including controlled reversible inhomogeneous broadening, atomic frequency combs, and quantum memories based on electromagnetically induced transparency, which are based on using ensembles as storage media. It is shown that strong superradiant effects manifested as decay rates larger than 1/T{sub 2}* are present even for moderate values of {alpha}L{<=}5 and increases as a function of {alpha}L. For even higher {alpha}L, effects such as off-resonant slow light is demonstrated and discussed and, finally, the efficiency of time-reversed optimized input pulses is tested. A maximum retrieval efficiency of {approx}20% is reached and agreement with the theoretically expected result is discussed.
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.
Quantum Hall effect in a system with an electron reservoir
NASA Astrophysics Data System (ADS)
Dorozhkin, S. I.
2016-04-01
Precise measurements of the magnetic-field and gate-voltage dependences of the capacitance of a field-effect transistor with an electron system in a wide GaAs quantum well have been carried out. It has been found that the capacitance minima caused by the gaps in the Landau spectrum of the electron system become anomalously wide when two size-quantization subbands are occupied. The effect is explained by retention of the chemical potential in the gap between the Landau levels of one of the subbands owing to redistribution of electrons between the subbands under a change in the magnetic field. The calculation taking into account this redistribution has been performed in a model of the electron system formed by two two-dimensional electron layers. The calculation results describe both the wide capacitance features and the observed disappearance of certain quantum Hall effect states.
Quantum gravity effects on charged microblack holes thermodynamics
NASA Astrophysics Data System (ADS)
Abbasvandi, Niloofar; Soleimani, M. J.; Radiman, Shahidan; Wan Abdullah, W. A. T.
2016-08-01
The charged black hole thermodynamics is corrected in terms of the quantum gravity effects. Most of the quantum gravity theories support the idea that near the Planck scale, the standard Heisenberg uncertainty principle should be reformulated by the so-called Generalized Uncertainty Principle (GUP) which provides a perturbation framework to perform required modifications of the black hole quantities. In this paper, we consider the effects of the minimal length and maximal momentum as GUP type I and the minimal length, minimal momentum and maximal momentum as GUP type II on thermo dynamics of the charged TeV-scale black holes. We also generalized our study to the universe with the extra dimensions based on the ADD model. In this framework, the effect of the electrical charge on thermodynamics of the black hole and existence of the charged black hole remnants as a potential candidate for the dark matter particles are discussed.
Quantum gravity effects on charged microblack holes thermodynamics
NASA Astrophysics Data System (ADS)
Abbasvandi, Niloofar; Soleimani, M. J.; Radiman, Shahidan; Wan Abdullah, W. A. T.
2016-08-01
The charged black hole thermodynamics is corrected in terms of the quantum gravity effects. Most of the quantum gravity theories support the idea that near the Planck scale, the standard Heisenberg uncertainty principle should be reformulated by the so-called Generalized Uncertainty Principle (GUP) which provides a perturbation framework to perform required modifications of the black hole quantities. In this paper, we consider the effects of the minimal length and maximal momentum as GUP type I and the minimal length, minimal momentum and maximal momentum as GUP type II on thermo dynamics of the charged TeV-scale black holes. We also generalized our study to the universe with the extra dimensions based on the ADD model. In this framework, the effect of the electrical charge on thermodynamics of the black hole and existence of the charged black hole remnants as a potential candidate for the dark matter particles are discussed.
Impurity effects on coupled quantum dot spin qubits in semiconductors
NASA Astrophysics Data System (ADS)
Nguyen, Nga; Das Sarma, Sankar
2011-03-01
Localized electron spins confined in semiconductor quantum dots are being studied by many groups as possible elementary qubits for solid-state quantum computation. We theoretically consider the effects of having unintentional charged impurities in laterally coupled two-dimensional double (GaAs) quantum dot systems, where each dot contains one or two electrons and a single charged impurity in the presence of an external magnetic field. We calculate the effect of the impurity on the 2-electron energy spectrum of each individual dot as well as on the spectrum of the coupled-double-dot 2-electron system. We find that the singlet-triplet exchange splitting between the two lowest energy states, both for the individual dots and the coupled dot system, depends sensitively on the location of the impurity and its coupling strength (i.e. the effective charge). We comment on the impurity effect in spin qubit operations in the double dot system based on our numerical results. This work is supported by LPS-CMTC and CNAM.
Covariant effective action for a Galilean invariant quantum Hall system
NASA Astrophysics Data System (ADS)
Geracie, Michael; Prabhu, Kartik; Roberts, Matthew M.
2016-09-01
We construct effective field theories for gapped quantum Hall systems coupled to background geometries with local Galilean invariance i.e. Bargmann spacetimes. Along with an electromagnetic field, these backgrounds include the effects of curved Galilean spacetimes, including torsion and a gravitational field, allowing us to study charge, energy, stress and mass currents within a unified framework. A shift symmetry specific to single constituent theories constraints the effective action to couple to an effective background gauge field and spin connection that is solved for by a self-consistent equation, providing a manifestly covariant extension of Hoyos and Son's improvement terms to arbitrary order in m.
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.
Heat capacity of water: A signature of nuclear quantum effects
NASA Astrophysics Data System (ADS)
Vega, C.; Conde, M. M.; McBride, C.; Abascal, J. L. F.; Noya, E. G.; Ramirez, R.; Sesé, L. M.
2010-01-01
In this note we present results for the heat capacity at constant pressure for the TIP4PQ/2005 model, as obtained from path-integral simulations. The model does a rather good job of describing both the heat capacity of ice Ih and of liquid water. Classical simulations using the TIP4P/2005, TIP3P, TIP4P, TIP4P-Ew, simple point charge/extended, and TIP5P models are unable to reproduce the heat capacity of water. Given that classical simulations do not satisfy the third law of thermodynamics, one would expect such a failure at low temperatures. However, it seems that for water, nuclear quantum effects influence the heat capacities all the way up to room temperature. The failure of classical simulations to reproduce Cp points to the necessity of incorporating nuclear quantum effects to describe this property accurately.
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)
Theory of the thermal Hall effect in quantum magnets.
Katsura, Hosho; Nagaosa, Naoto; Lee, Patrick A
2010-02-12
We present a theory of the thermal Hall effect in insulating quantum magnets, where the heat current is totally carried by charge-neutral objects such as magnons and spinons. Two distinct types of thermal Hall responses are identified. For ordered magnets, the intrinsic thermal Hall effect for magnons arises when certain conditions are satisfied for the lattice geometry and the underlying magnetic order. The other type is allowed in a spin liquid which is a novel quantum state since there is no order even at zero temperature. For this case, the deconfined spinons contribute to the thermal Hall response due to Lorentz force. These results offer a clear experimental method to prove the existence of the deconfined spinons via a thermal transport phenomenon.
Charge fractionalization in the integer quantum Hall effect.
Inoue, Hiroyuki; Grivnin, Anna; Ofek, Nissim; Neder, Izhar; Heiblum, Moty; Umansky, Vladimir; Mahalu, Diana
2014-04-25
We report an observation, via sensitive shot noise measurements, of charge fractionalization of chiral edge electrons in the integer quantum Hall effect regime. Such fractionalization results solely from interchannel Coulomb interaction, leading electrons to decompose to excitations carrying fractional charges. The experiment was performed by guiding a partitioned current carrying edge channel in proximity to another unbiased edge channel, leading to shot noise in the unbiased edge channel without net current, which exhibited an unconventional dependence on the partitioning. The determination of the fractional excitations, as well as the relative velocities of the two original (prior to the interaction) channels, relied on a recent theory pertaining to this measurement. Our result exemplifies the correlated nature of multiple chiral edge channels in the integer quantum Hall effect regime.
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 Schrödinger cat states during the observed evolution, closely connected to the high-order diffraction modes in Fabry-Pérot optical resonators.
NASA Astrophysics Data System (ADS)
Shi, Pengqin; Hu, Menghan; Ying, Yaofeng; Jin, Jinshuang
2016-09-01
Based on the time-nonlocal particle number-resolved master equation, we investigate the sequential electron transport through the interacting double quantum dots. Our calculations show that there exists the effect of energy renormalization in the dispersion of the bath interaction spectrum and it is sensitive to the the bandwidth of the bath. This effect would strongly affect the stationary current and its zero-frequency shot noise for weak inter-dot coherent coupling strength, but for strong inter-dot coupling regime, it is negligible due to the strong intrinsic Rabi coherent dynamics. Moreover, the possible observable effects of the energy renormalization in the noise spectrum are also investigated through the Rabi coherence signal. Finally, the non-Markovian effect is manifested in the finite-frequency noise spectrum with the appearance of quasisteps, and the magnitude of these quasisteps are modified by the dispersion function.
The mechanics of elastic loading and recoil in anuran jumping.
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
The mechanics of elastic loading and recoil in anuran jumping.
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.
Effects of a scalar scaling field on quantum mechanics
NASA Astrophysics Data System (ADS)
Benioff, Paul
2016-07-01
This paper describes the effects of a complex scalar scaling field on quantum mechanics. The field origin is an extension of the gauge freedom for basis choice in gauge theories to the underlying scalar field. The extension is based on the idea that the value of a number at one space time point does not determine the value at another point. This, combined with the description of mathematical systems as structures of different types, results in the presence of separate number fields and vector spaces as structures, at different space time locations. Complex number structures and vector spaces at each location are scaled by a complex space time dependent scaling factor. The effect of this scaling factor on several physical and geometric quantities has been described in other work. Here the emphasis is on quantum mechanics of one and two particles, their states and properties. Multiparticle states are also briefly described. The effect shows as a complex, nonunitary, scalar field connection on a fiber bundle description of nonrelativistic quantum mechanics. The lack of physical evidence for the presence of this field so far means that the coupling constant of this field to fermions is very small. It also means that the gradient of the field must be very small in a local region of cosmological space and time. Outside this region, there are no restrictions on the field gradient.
Topological superconductivity, topological confinement, and the vortex quantum Hall effect
Diamantini, M. Cristina; Trugenberger, Carlo A.
2011-09-01
Topological matter is characterized by the presence of a topological BF term in its long-distance effective action. Topological defects due to the compactness of the U(1) gauge fields induce quantum phase transitions between topological insulators, topological superconductors, and topological confinement. In conventional superconductivity, because of spontaneous symmetry breaking, the photon acquires a mass due to the Anderson-Higgs mechanism. In this paper we derive the corresponding effective actions for the electromagnetic field in topological superconductors and topological confinement phases. In topological superconductors magnetic flux is confined and the photon acquires a topological mass through the BF mechanism: no symmetry breaking is involved, the ground state has topological order, and the transition is induced by quantum fluctuations. In topological confinement, instead, electric charge is linearly confined and the photon becomes a massive antisymmetric tensor via the Stueckelberg mechanism. Oblique confinement phases arise when the string condensate carries both magnetic and electric flux (dyonic strings). Such phases are characterized by a vortex quantum Hall effect potentially relevant for the dissipationless transport of information stored on vortices.
Quantum instanton evaluation of the kinetic isotope effects
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%.
Effect of carrier dynamics and temperature on two-state lasing in semiconductor quantum dot lasers
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.
Origin of open recoil curves in L10-A1 FePt exchange coupled nanocomposite thin film
NASA Astrophysics Data System (ADS)
Goyal, Rajan; Kapoor, Akanksha; Lamba, S.; Annapoorni, S.
2016-11-01
Mixed phase FePt systems with intergranular coupling may be looked upon as natural exchange spring systems. The coupling strength between the soft and hard phase in these systems can be analyzed using recoil curves. However, the origin of open recoil curves depicting the breakdown of exchange coupling or anisotropy variation in hard phase is still an ambiguity and requires an in-depth analysis. In order to investigate this, an analysis of the recoil curves for L10-A1 FePt nanocomposite thin films of varying thickness have been performed. The switching field distribution reveals that the maximum of openness of recoil curve is directly proportional to the amount of uncoupled soft phase present in the system. The coupling between the hard and soft phase is also found to increase with the thickness of the film. Monte Carlo simulations on a model three dimensional array of interacting nanomagnetic grains provide further insight into the effect of inter granular exchange interactions between the soft and hard phases.
Quantum amplification effect in a horizon fluctuation
Ansari, Mohammad H.
2010-05-15
The appearance of a few unevenly spaced bright flashes of light on top of Hawking radiation is the sign of the amplification effect in black hole horizon fluctuations. Previous studies on this problem suffer from the lack of considering all emitted photons in the theoretical spectroscopy of these fluctuations. In this paper, we include all of the physical transition weights and present a consistent intensity formula. This modifies a black hole radiation pattern.
Kondo Effect at a Quantum Critical Point
NASA Astrophysics Data System (ADS)
Ramazashvili, Revaz; Coleman, Piers
1998-03-01
The Kondo effect in a metal on the verge of a zero-temperature magnetic instability provides a fascinating example of interference between local and long-range correlations. (A. I. Larkin and V. I. Mel'nikov, Sov. Phys. JETP 34, 656 (1972)) (P. Coleman and A. M. Tsvelik, cond-mat/9707003) (A. Sengupta, cond-mat/9707316) We discuss possible consequences of this interference, including the breakdown of the Fermi liquid state.
Thermopower enhancement in quantum wells with the Rashba effect
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.
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.
Noninertial effects on the quantum dynamics of scalar bosons
NASA Astrophysics Data System (ADS)
Castro, Luis B.
2016-02-01
The noninertial effect of rotating frames on the quantum dynamics of scalar bosons embedded in the background of a cosmic string is considered. In this work, scalar bosons are described by the Duffin-Kemmer-Petiau (DKP) formalism. Considering the DKP oscillator in this background the combined effects of a rotating frames and cosmic string on the equation of motion, energy spectrum, and DKP spinor are analyzed and discussed in detail. Additionally, the effect of rotating frames on the scalar bosons' localization is studied.
Negative muon chemistry: the quantum muon effect and the finite nuclear mass effect.
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.
Sumner, Isaiah; Iyengar, Srinivasan S
2007-10-18
We have introduced a computational methodology to study vibrational spectroscopy in clusters inclusive of critical nuclear quantum effects. This approach is based on the recently developed quantum wavepacket ab initio molecular dynamics method that combines quantum wavepacket dynamics with ab initio molecular dynamics. The computational efficiency of the dynamical procedure is drastically improved (by several orders of magnitude) through the utilization of wavelet-based techniques combined with the previously introduced time-dependent deterministic sampling procedure measure to achieve stable, picosecond length, quantum-classical dynamics of electrons and nuclei in clusters. The dynamical information is employed to construct a novel cumulative flux/velocity correlation function, where the wavepacket flux from the quantized particle is combined with classical nuclear velocities to obtain the vibrational density of states. The approach is demonstrated by computing the vibrational density of states of [Cl-H-Cl]-, inclusive of critical quantum nuclear effects, and our results are in good agreement with experiment. A general hierarchical procedure is also provided, based on electronic structure harmonic frequencies, classical ab initio molecular dynamics, computation of nuclear quantum-mechanical eigenstates, and employing quantum wavepacket ab initio dynamics to understand vibrational spectroscopy in hydrogen-bonded clusters that display large degrees of anharmonicities.
Quantum Hall effect in an InAs /AlSb double quantum well
NASA Astrophysics Data System (ADS)
Yakunin, M. V.; Podgornykh, S. M.; Sadofyev, Yu. G.
2009-01-01
Double quantum wells (DQWs) were first implemented in the InAs /AlSb heterosystem, which is characterized by a large Landé g factor ∣g∣=15 of the InAs layers forming the well, much larger than the bulk g factor ∣g∣=0.4 of the GaAs in conventional GaAs /AlGaAs DQWs. The quality of the samples is good enough to permit observation of a clear picture of the quantum Hall effect (QHE). Despite the small tunneling gap, which is due to the large barrier height (1.4eV), features with odd filling factors ν =3,5,7,… are present in the QHE, due to collectivized interlayer states of the DQW. When the field is rotated relative to the normal to the layers, the ν =3 state is suppressed, confirming the collectivized nature of that state and denying that it could owe its existence to a strong asymmetry of the DQW. Previously the destruction of the collectivized QHE states by a parallel field had been observed only for the ν =1 state. The observation of a similar effect for ν =3 in an InAs /AlSb DQW may be due to the large bulk g factor of InAs.
Lifetime measurement of the 41+ state of 58Ni with the recoil distance method
NASA Astrophysics Data System (ADS)
Loelius, C.; Iwasaki, H.; Brown, B. A.; Honma, M.; Bader, V. M.; Baugher, T.; Bazin, D.; Berryman, J. S.; Braunroth, T.; Campbell, C. M.; Dewald, A.; Gade, A.; Kobayashi, N.; Langer, C.; Lee, I. Y.; Lemasson, A.; Lunderberg, E.; Morse, C.; Recchia, F.; Smalley, D.; Stroberg, S. R.; Wadsworth, R.; Walz, C.; Weisshaar, D.; Westerberg, A.; Whitmore, K.; Wimmer, K.
2016-08-01
The quadrupole transition rate for the 41+→21+ transition of 58Ni was determined from an application of the recoil distance method with the Gamma-Ray Energy Tracking In-beam Nuclear Array (GRETINA). The present result of the B (E 2 ;41+→21+) was found to be 50-6+11e2fm4 , which is about three times smaller than the literature value, indicating substantially less collectivity than previously believed. Shell model calculations performed with the GXPF1A effective interaction agree with the present data and the validity of the standard effective charges in understanding collectivity in the nickel isotopes is discussed.
Scattering approach to quantum transport and many body effects
NASA Astrophysics Data System (ADS)
Pichard, Jean-Louis; Freyn, Axel
2010-12-01
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 td, coupled to leads by hopping terms tc. We show that the quantum conductance as a function of td is given by a universal function, independently of the values of U and tc, if one measures td in units of a characteristic scale τ(U,tc). Mapping the double dot system without spin onto a single dot Anderson model with spin and magnetic field, we show that τ(U,tc) = 2TK, where TK is the Kondo temperature of the Anderson model.
Anyons and the quantum Hall effect-A pedagogical review
Stern, Ady
2008-01-15
The dichotomy between fermions and bosons is at the root of many physical phenomena, from metallic conduction of electricity to super-fluidity, and from the periodic table to coherent propagation of light. The dichotomy originates from the symmetry of the quantum mechanical wave function to the interchange of two identical particles. In systems that are confined to two spatial dimensions particles that are neither fermions nor bosons, coined 'anyons', may exist. The fractional quantum Hall effect offers an experimental system where this possibility is realized. In this paper we present the concept of anyons, we explain why the observation of the fractional quantum Hall effect almost forces the notion of anyons upon us, and we review several possible ways for a direct observation of the physics of anyons. Furthermore, we devote a large part of the paper to non-abelian anyons, motivating their existence from the point of view of trial wave functions, giving a simple exposition of their relation to conformal field theories, and reviewing several proposals for their direct observation.
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.
Fractionally charged skyrmions in fractional quantum Hall effect.
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
Fractionally charged skyrmions in fractional quantum Hall effect
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
Quantum effects in the interference of photon number states
NASA Astrophysics Data System (ADS)
Hofmann, Holger F.; Hibino, Keito; Fujiwara, Kazuya; Wu, Jun-Yi
2016-10-01
Multiphoton interference results in modulations of output probabilities with phase shift periods that are much shorter than 2 π . Here, we investigate the physics behind these statistical patterns in the case of well-defined photon numbers in the input and output modes of a two-path interferometer. We show that the periodicity of the multiphoton interference is related to the weak value of the unobserved intensity difference between the two arms of the interferometer. This means that the operator relations between the photon number differences in input, path, and output can be used to determine the periodicity of the experimentally observed quantum interference, establishing an important link between the classical causality of random phase interference and quantum effects that depend on the superposition of classically distinct possibilities.
Matrix method analysis of quantum Hall effect device connections
NASA Astrophysics Data System (ADS)
Ortolano, M.; Callegaro, L.
2012-02-01
The modelling of electrical connections of single, or several, multiterminal quantum Hall effect (QHE) devices is relevant for electrical metrology: it is known, in fact, that certain particular connections allow (i) the realization of multiples or fractions of the quantized resistance, or (ii) the rejection of stray impedances, so that the configuration maintains the status of quantum standard. Ricketts-Kemeny and Delahaye equivalent circuits are known to be accurate models of the QHE: however, the numerical or analytical solution of electrical networks including these equivalent circuits can be difficult. In this paper, we introduce a method of analysis based on the representation of a QHE device by means of the indefinite admittance matrix: external connections are then represented with another matrix, easily written by inspection. Some examples, including the solution of double- and triple-series connections, are shown.
Interaction driven quantum Hall effect in artificially stacked graphene bilayers.
Iqbal, Muhammad Zahir; Iqbal, Muhammad Waqas; Siddique, Salma; Khan, Muhammad Farooq; Ramay, Shahid Mahmood; Nam, Jungtae; Kim, Keun Soo; Eom, Jonghwa
2016-01-01
The honeycomb lattice structure of graphene gives rise to its exceptional electronic properties of linear dispersion relation and its chiral nature of charge carriers. The exceptional electronic properties of graphene stem from linear dispersion relation and chiral nature of charge carries, originating from its honeycomb lattice structure. Here, we address the quantum Hall effect in artificially stacked graphene bilayers and single layer graphene grown by chemical vapor deposition. The quantum Hall plateaus started to appear more than 3 T and became clearer at higher magnetic fields up to 9 T. Shubnikov-de Hass oscillations were manifestly observed in graphene bilayers texture. These unusual plateaus may have been due to the layers interaction in artificially stacked graphene bilayers. Our study initiates the understanding of interactions between artificially stacked graphene layers. PMID:27098387
Fractionally charged skyrmions in fractional quantum Hall effect.
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.
Fractionally charged skyrmions in fractional quantum Hall effect
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.
Effects of quantum fluctuations of metric on the universe
NASA Astrophysics Data System (ADS)
Yang, Rongjia
2016-09-01
We consider a model of modified gravity from the nonperturbative quantization of a metric. We obtain the modified gravitational field equations and the modified conservational equations. We apply it to the FLRW spacetime and find that due to the quantum fluctuations a bounce universe can be obtained and a decelerated expansion can also possibly be obtained in a dark energy dominated epoch. We also discuss the effects of quantum fluctuations on inflation parameters (such as slow-roll parameters, spectral index, and the spectrum of the primordial curvature perturbation) and find values of parameters in the comparing the predictions of inflation can also work to drive the current epoch of acceleration. We obtain the constraints on the parameter of the theory from the observation of the big bang nucleosynthesis.
Interaction driven quantum Hall effect in artificially stacked graphene bilayers
Iqbal, Muhammad Zahir; Iqbal, Muhammad Waqas; Siddique, Salma; Khan, Muhammad Farooq; Ramay, Shahid Mahmood; Nam, Jungtae; Kim, Keun Soo; Eom, Jonghwa
2016-01-01
The honeycomb lattice structure of graphene gives rise to its exceptional electronic properties of linear dispersion relation and its chiral nature of charge carriers. The exceptional electronic properties of graphene stem from linear dispersion relation and chiral nature of charge carries, originating from its honeycomb lattice structure. Here, we address the quantum Hall effect in artificially stacked graphene bilayers and single layer graphene grown by chemical vapor deposition. The quantum Hall plateaus started to appear more than 3 T and became clearer at higher magnetic fields up to 9 T. Shubnikov-de Hass oscillations were manifestly observed in graphene bilayers texture. These unusual plateaus may have been due to the layers interaction in artificially stacked graphene bilayers. Our study initiates the understanding of interactions between artificially stacked graphene layers. PMID:27098387
Effective fermion kinematics from modified quantum gravity
NASA Astrophysics Data System (ADS)
Alexandre, J.; Leite, J.
2016-10-01
We consider a classical fermion and a classical scalar, propagating on two different kinds of four-dimensional diffeomorphism breaking gravity backgrounds, and we derive the one-loop effective dispersion relation for matter, after integrating out gravitons. One gravity model involves quadratic divergences at one-loop, as in Einstein gravity, and the other model is the z = 3 non-projectable Horava-Lifshitz gravity, which involves logarithmic divergences only. Although these two models behave differently in the ultraviolet, the IR phenomenology for matter fields is comparable: (i) for generic values for the parameters, both models identify 1010 GeV as the characteristic scale above which they are not consistent with current upper bounds on Lorentz symmetry violation; (ii) for both models, there is always a fine-tuning of parameters which allows the cancellation of the indicator for Lorentz symmetry violation.
Memory effects and mesoscopic quantum transport
NASA Astrophysics Data System (ADS)
Knezevic, Irena
The active region of a mesoscopic structure or a modern semiconductor device needs to be treated as a dynamically open many-body system, exchanging information and particles with the contacts. The feedback from the active region to the contacts cannot be neglected, especially during the transient regime, because, due to the small size, both the active region and the contacts contain a small number of electrons. In this work, a rigorous theoretical approach for treating mesoscopic electronic systems as open many-body systems is developed. It is based on the partial-trace-free (PTF) approach that has provided a new outlook on the evolution of the reduced density matrix of an open system, and enabled several lines of research, which are presented in this work. First, an effective, memory-containing interaction was recognized in the equations of motion for the representation submatrices of the evolution operator (these submatrices are written in a special basis, adapted for the PTF approach, in the Liouville space of the composite closed system). The memory dressing, a quantity that separates the effective from the physical interaction, was identified. It obeys a self-contained nonlinear equation of motion (the Riccati matrix equation), whose solution can be represented in a diagrammatic fashion and enables physical approximations beyond the weak coupling limit. On the other hand, a foundation for the generalization of nonequilibrium Green's functions to open systems was laid. Two-time correlation functions were generalized, and evolution in both the transient and the steady-state regime was discussed. Based on the PTF approach, a second-order master equation of motion was derived for the reduced density matrix of the active region of a real electronic system: a resonant-tunneling diode (RTD). This equation incorporates the exchange of information and particles between the active region and the contacts, while being computationally tractable. The master equation was
Yamaguchi, Makoto; Asano, Takashi; Noda, Susumu
2008-10-27
Solid-state cavity quantum-electrodynamics (QED) has great potential owing to advances such as coupled systems combining a nanocavity and a quantum dot (QD). These systems involve two photon-emission mechanisms: the Purcell effect in the weak coupling regime and vacuum Rabi-splitting in the strong coupling regime. In this paper, we describe a third emission mechanism based on the quantum anti-Zeno effect (AZE) induced by the pure-dephasing in a QD. This is significantly enhanced by the inherent characteristics of the nanocavity. This mechanism explains the origin of strong photon emission at a cavity mode largely detuned from a QD, previously considered a counterintuitive, prima facie non-energy-conserving, light-emission phenomenon. These findings could help in controlling the decay and emission characteristics of solid-state cavity QED, and developing solid-state quantum devices.
Quantum Zeno effect in the strong measurement regime of circuit quantum electrodynamics
NASA Astrophysics Data System (ADS)
Slichter, D. H.; Müller, C.; Vijay, R.; Weber, S. J.; Blais, A.; Siddiqi, I.
2016-05-01
We observe the quantum Zeno effect—where the act of measurement slows the rate of quantum state transitions—in a superconducting qubit using linear circuit quantum electrodynamics readout and a near-quantum-limited following amplifier. Under simultaneous strong measurement and qubit drive, the qubit undergoes a series of quantum jumps between states. These jumps are visible in the experimental measurement record and are analyzed using maximum likelihood estimation to determine qubit transition rates. The observed rates agree with both analytical predictions and numerical simulations. The analysis methods are suitable for processing general noisy random telegraph signals.
NASA Astrophysics Data System (ADS)
Rossi, R., Jr.; de Magalhães, A. R. Bosco; Nemes, M. C.
2008-01-01
We propose an experiment for the observation of the quantum Zeno effect (QZE) in a bipartite system. The setup involves two microwave cavities and a “tunneling” photon, which is observed by the passage of Rydberg atoms. Our proposal allows for the consideration of two types of measurements, namely, sequential observations of the atomic state and its inclusive measurement. In the present system the two processes are shown to lead to the same result in the ideal case. We consider realistic atom-field interaction times, cavity dissipation, and limited detection efficiency. Analytical expressions for the “tunneling” probability are obtained exhibiting a competition between the environment induced exponential decay and the characteristic t2 (for short times) dependence of the QZE. We show that for sufficiently small dissipation constants the effect can be observed with current experimental facilities.
Effective production of orbital quantum entanglement in chaotic quantum dots with nonideal contacts
NASA Astrophysics Data System (ADS)
Santos, E. H.; Almeida, F. A. G.
2016-09-01
We study orbital entanglement production in a chaotic quantum dot with two-channel leads by varying the opacity of the contacts in the unitary and orthogonal Wigner-Dyson ensembles. We computed the occurrence probability of entangled states (squared norm) and its concurrence (entanglement level). We also define an entanglement production factor to properly evaluate the entanglement behavior in the system considering effective aspects. The results are numerically obtained through (i) integrations over random matrix ensembles (exact results) for the scenario of one contact ideally fixed and (ii) random matrix simulations for arbitrary contact opacities (sampling). Those outcomes are in mutual agreement and indicate that the optimum effective production of orbital entanglement is achieved when both contacts are ideal and the time-reversal symmetry is broken.
Cotunneling Drag Effect in Coulomb-Coupled Quantum Dots.
Keller, A J; Lim, J S; Sánchez, David; López, Rosa; Amasha, S; Katine, J A; Shtrikman, Hadas; Goldhaber-Gordon, D
2016-08-01
In Coulomb drag, a current flowing in one conductor can induce a voltage across an adjacent conductor via the Coulomb interaction. The mechanisms yielding drag effects are not always understood, even though drag effects are sufficiently general to be seen in many low-dimensional systems. In this Letter, we observe Coulomb drag in a Coulomb-coupled double quantum dot and, through both experimental and theoretical arguments, identify cotunneling as essential to obtaining a correct qualitative understanding of the drag behavior. PMID:27541473
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
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.
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.
{theta} parameter in loop quantum gravity: Effects on quantum geometry and black hole entropy
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.
Possible astrophysical observables of quantum gravity effects near black holes
NASA Astrophysics Data System (ADS)
Pen, Ue-Li; Broderick, Avery E.
2014-12-01
Recent implications of results from quantum information theory applied to black holes have led to the confusing conclusions that require either abandoning the equivalence principle (e.g. the firewall picture), or locality, or even more unpalatable options. The recent discovery of a pulsar orbiting a black hole opens up new possibilities for tests of theories of gravity. We examine possible observational effects of semiclassical quantum gravity in the vicinity of black holes, as probed by pulsars and event horizon telescope imaging of flares. In some cases, pulsar radiation may be observable at wavelengths only two orders of magnitude shorter than the Hawking radiation, so precision interferometry of lensed pulsar images may shed light on the quantum gravitational processes and interaction of Hawking radiation with the space-time near the black hole. This paper discusses the impact on the pulsar radiation interference pattern, which is observable through the modulation index in the foreseeable future, and discusses a possible classical limit of non-locality.
Proximity Effects in Nb/InAs Quantum Well Structures
NASA Astrophysics Data System (ADS)
Eckhause, T. A.; Gwinn, E. G.; Thomas, M.; Kroemer, H.
1997-03-01
InAs has been widely used as a weak link in superconductor-semiconductor-superconductor junctions.(E. L. Yuh et al., Surf. Sci. 361/362), 315 (1996) Most theoretical treatments of such structures assume that proximity to InAs does not reduce the Nb gap. To test this assumption we have fabricated structures with an ultra-thin layer of Nb on the exposed surface of the InAs quantum well. After removing the cap layer from the μ = 210,000 cm/V\\cdot s, ns = 5.5 x 10^12cm-2 InAs quantum well, Nb films of ~ 100Åthickness are deposited simultaneously on the 150Åquantum well and on a semi-insulating GaAs substrate (both surfaces are sputter cleaned prior to deposition). We cap the Nb with a ~100ÅSi layer of to prevent oxidation.(S.I. Park and T.H. Geballe, Physica B 135), 108 (1985) After processing, the sheet resistances just above Tc are 23.5Ω and 67Ω in the Nb film and quantum well, respectively. We observed a ~ 0.2K lower critical temperature in the Nb/InAs sample. As the Nb films are otherwise nominally identical and the proximity effect is known to suppress the critical temperature of thin films, this suppression in Tc may be due to the reduction of the gap in Nb. Supported by NSF grant DMR-93-14899
Quantum anomalous Hall effect in magnetic topological insulators
Wang, Jing; Lian, Biao; Zhang, Shou -Cheng
2015-08-25
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 presentmore » 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. Furthermore, 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.« less
Quantum anomalous Hall effect in magnetic topological insulators
Wang, Jing; Lian, Biao; Zhang, Shou -Cheng
2015-08-25
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. Furthermore, 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.
Control of recoil losses in nanomechanical SiN membrane resonators
NASA Astrophysics Data System (ADS)
Borrielli, A.; Marconi, L.; Marin, F.; Marino, F.; Morana, B.; Pandraud, G.; Pontin, A.; Prodi, G. A.; Sarro, P. M.; Serra, E.; Bonaldi, M.
2016-09-01
In the context of a recoil damping analysis, we have designed and produced a membrane resonator equipped with a specific on-chip structure working as a "loss shield" for a circular membrane. In this device the vibrations of the membrane, with a quality factor of 107, reach the limit set by the intrinsic dissipation in silicon nitride, for all the modes and regardless of the modal shape, also at low frequency. Guided by our theoretical model of the loss shield, we describe the design rationale of the device, which can be used as effective replacement of commercial membrane resonators in advanced optomechanical setups, also at cryogenic temperatures.
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.
Ionization efficiency study for low energy nuclear recoils in germanium
NASA Astrophysics Data System (ADS)
Barker, D.; Wei, W.-Z.; Mei, D.-M.; Zhang, C.
2013-08-01
We used the internal conversion (E0 transition) of germanium-72 to indirectly measure the low energy nuclear recoils of germanium. Together with a reliable Monte Carlo package, in which we implement the internal conversion process, the data was compared to the Lindhard (k = 0.159) and Barker-Mei models. A shape analysis indicates that both models agree well with data in the region of interest within 4%. The most probable value (MPV) of the nuclear recoils obtained from the shape analysis is 17.5 ± 0.12 (sys) ±0.035 (stat) keV with an average path-length of 0.014 μm.
Characterization of the CRESST detectors by neutron induced nuclear recoils
NASA Astrophysics Data System (ADS)
Coppi, C.; Ciemniak, C.; von Feilitzsch, F.; Gütlein, A.; Hagn, H.; Isaila, C.; Jochum, J.; Kimmerle, M.; Lanfranchi, J.-C.; Pfister, S.; Potzel, W.; Rau, W.; Roth, S.; Rottler, K.; Sailer, C.; Scholl, S.; Usherov, I.; Westphal, W.
CRESST is an experiment for the direct detection of dark matter particles via nuclear recoils. The CRESST detectors, based on CaWO4 scintillating crystals, are able to discriminate γ and β background by simultaneously measuring the light and phonon signals produced by particle interactions. The discrimination of the background is possible because of the different light output (Quenching Factor, QF) for nuclear and electron recoils. In this article a measurement is shown, aimed at the determination of the QFs of the different nuclei (O, Ca, W) of the detector crystal at 40-60 mK using an 11 MeV neutron beam produced at the Maier-Leibnitz-Laboratorium in Garching (MLL).
Recoiling supermassive black holes: a search in the nearby universe
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.
Time-of-flight direct recoil ion scattering spectrometer
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.
Recoil Polarization for Neutral Pion Electroproduction near the Delta Resonance
Kelly, James J
2003-10-01
We have measured angular distributions for recoil polarization in the p(e,e'p)p0 reaction at Q2»1(GeV/c)2 with 1.16 |lte| W |lte|1.36 GeV across the D resonance. The data are compared with representative models and a truncated Legendre analysis is compared with a more general multipole analysis.
Time-of-flight direct recoil ion scattering spectrometer
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).
Landau damping and the onset of particle trapping in quantum plasmas
Daligault, Jérôme
2014-04-15
Using analytical theory and simulations, we assess the impact of quantum effects on non-linear wave-particle interactions in quantum plasmas. We more specifically focus on the resonant interaction between Langmuir waves and electrons, which, in classical plasmas, lead to particle trapping. Two regimes are identified depending on the difference between the time scale of oscillation t{sub B}(k)=√(m/eEk) of a trapped electron and the quantum time scale t{sub q}(k)=2m/ℏk{sup 2} related to recoil effect, where E and k are the wave amplitude and wave vector. In the classical-like regime, t{sub B}(k) < t{sub q}(k), resonant electrons are trapped in the wave troughs and greatly affect the evolution of the system long before the wave has had time to Landau damp by a large amount according to linear theory. In the quantum regime, t{sub B}(k) > t{sub q}(k), particle trapping is hampered by the finite recoil imparted to resonant electrons in their interactions with plasmons.
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.
The recoil proton polarization in. pi. p elastic scattering
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.
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 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.
Effect of quantum nuclear motion on hydrogen bonding.
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 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.
Quantum effects on compressional Alfven waves in compensated semiconductors
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 Schrödinger 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.
Effect of quantum nuclear motion on hydrogen bonding
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.
Nuclear quantum effects on the stability of cationic neon clusters
NASA Astrophysics Data System (ADS)
Calvo, F.; Naumkin, F. Y.; Wales, D. J.
2012-11-01
The stable structures of cationic neon clusters containing up to 57 atoms have been located using a diatomic-in-molecules potential energy surface and basin-hopping hierarchical optimization. The effects of vibrational delocalization were included either in the harmonic approximation, or by performing Langevin molecular dynamics simulations coupled to a quantum thermal bath at T=0. For most clusters, zero-point motion is sufficiently high to blur the picture of a single well-defined structure. However, structural diversity of the ground state wavefunction is found to be lower at sizes 14, 21, and 56, which correspond to special stabilities in experimental mass spectra.
Vortex equations governing the fractional quantum Hall effect
Medina, Luciano
2015-09-15
An existence theory is established for a coupled non-linear elliptic system, known as “vortex equations,” describing the fractional quantum Hall effect in 2-dimensional double-layered electron systems. Via variational methods, we prove the existence and uniqueness of multiple vortices over a doubly periodic domain and the full plane. In the doubly periodic situation, explicit sufficient and necessary conditions are obtained that relate the size of the domain and the vortex numbers. For the full plane case, existence is established for all finite-energy solutions and exponential decay estimates are proved. Quantization phenomena of the magnetic flux are found in both cases.
Quantum anomalous Hall effect in topological insulator memory
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.
Is the quantum Hall effect influenced by the gravitational field?
Hehl, Friedrich W; Obukhov, Yuri N; Rosenow, Bernd
2004-08-27
Most of the experiments on the quantum Hall effect (QHE) were made at approximately the same height above sea level. A future international comparison will determine whether the gravitational field g(x) influences the QHE. In the realm of (1+2)-dimensional phenomenological macroscopic electrodynamics, the Ohm-Hall law is metric independent ("topological"). This suggests that it does not couple to g(x). We corroborate this result by a microscopic calculation of the Hall conductance in the presence of a post-Newtonian gravitational field. PMID:15447125
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…
Khalil, Elias L
2013-06-01
Although the quantum probability (QP) can be useful to model the context effect, it is not relevant to the order effect, conjunction fallacy, and other related biases. Although the issue of potentiality, which is the intuition behind QP, is involved in the context effect, it is not involved in the other biases.
Effects of Shannon entropy and electric field on polaron in RbCl triangular quantum dot
NASA Astrophysics Data System (ADS)
M, Tiotsop; A, J. Fotue; S, C. Kenfack; N, Issofa; H, Fotsin; L, C. Fai
2016-04-01
In this paper, the time evolution of the quantum mechanical state of a polaron is examined using the Pekar type variational method on the condition of the electric-LO-phonon strong-coupling and polar angle in RbCl triangular quantum dot. We obtain the eigenenergies, and the eigenfunctions of the ground state, and the first excited state respectively. This system in a quantum dot can be treated as a two-level quantum system qubit and the numerical calculations are performed. The effects of Shannon entropy and electric field on the polaron in the RbCl triangular quantum dot are also studied.
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.
Electronic simulation of a multiterminal quantum Hall effect device
NASA Astrophysics Data System (ADS)
Sosso, A.; Capra, P. P.
1999-04-01
A circuit with only resistors and unity gain amplifiers can be proven to be equivalent to the Ricketts and Kemeny electrical model of multiterminal quantum Hall effect (QHE) devices. By means of the new equivalent circuit, commercial software for electronic circuit analysis can be used to study a QHE measurement system. Moreover, it can be easily implemented, and we were able to build a circuit that simulates the electrical behavior of a QHE device. Particular care was taken in the design to reduce the effect of parasitic capacitances, which act as loads connected to the device terminals. Bootstrap buffers have been adopted to significantly reduce the capacitance of input stage. The small residual loading effect can be calculated and eliminated, allowing simulation of a QHE device with good accuracy.
Semianalytical quantum model for graphene field-effect transistors
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.
Observing the Quantum Spin Hall Effect with Ultracold Atoms
NASA Astrophysics Data System (ADS)
Vaishnav, J. Y.; Stanescu, Tudor D.; Clark, Charles W.; Galitski, Victor
2009-03-01
The quantum spin Hall (QSH) state is a topologically nontrivial state of matter proposed to exist in certain 2-D systems with spin-orbit coupling. While the electronic states of a QSH insulator are gapped in the bulk, a QSH insulator is characterized by gapless edge states of different spins which counterpropagate at a given edge; the spin is correlated with the direction of propagation. Recent proposals ootnotetextT. D. Stanescu, C. Zhang, V. Galitski, Physical Review Letters 99, 110403 (2007), J. Y. Vaishnav, Charles W. Clark, Physical Review Letters 100, 153002 (2008). suggest that synthetic spin-orbit couplings can be created for cold atoms moving in spatially varying light fields. Here, we identify an optical lattice setup which generates an effective QSH effect for cold, multilevel atoms. We also discuss methods for experimental detection of the atomic QSH effect.
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.
Dynamical gauge effects in an open quantum network
NASA Astrophysics Data System (ADS)
Zhao, Jianshi; Price, Craig; Liu, Qi; Gemelke, Nathan
2016-05-01
We describe new experimental techniques for simulation of high-energy field theories based on an analogy between open thermodynamic systems and effective dynamical gauge-fields following SU(2) × U(1) Yang-Mills models. By coupling near-resonant laser-modes to atoms moving in a disordered optical environment, we create an open system which exhibits a non-equilibrium phase transition between two steady-state behaviors, exhibiting scale-invariant behavior near the transition. By measuring transport of atoms through the disordered network, we observe two distinct scaling behaviors, corresponding to the classical and quantum limits for the dynamical gauge field. This behavior is loosely analogous to dynamical gauge effects in quantum chromodynamics, and can mapped onto generalized open problems in theoretical understanding of quantized non-Abelian gauge theories. Additional, the scaling behavior can be understood from the geometric structure of the gauge potential and linked to the measure of information in the local disordered potential, reflecting an underlying holographic principle. We acknowledge support from NSF Award No.1068570, and the Charles E. Kaufman Foundation.
Mixing effects in the crystallization of supercooled quantum binary liquids
Kühnel, M.; Kalinin, A.; Fernández, J. M.; Tejeda, G.; Moreno, E.; Montero, S.; Tramonto, F.; Galli, D. E.; Nava, M.; Grisenti, R. E.
2015-08-14
By means of Raman spectroscopy of liquid microjets, we have investigated the crystallization process of supercooled quantum liquid mixtures composed of parahydrogen (pH{sub 2}) or orthodeuterium (oD{sub 2}) diluted with small amounts of neon. We show that the introduction of the Ne impurities affects the crystallization kinetics in terms of a significant reduction of the measured pH{sub 2} and oD{sub 2} crystal growth rates, similarly to what found in our previous work on supercooled pH{sub 2}-oD{sub 2} liquid mixtures [Kühnel et al., Phys. Rev. B 89, 180201(R) (2014)]. Our experimental results, in combination with path-integral simulations of the supercooled liquid mixtures, suggest in particular a correlation between the measured growth rates and the ratio of the effective particle sizes originating from quantum delocalization effects. We further show that the crystalline structure of the mixtures is also affected to a large extent by the presence of the Ne impurities, which likely initiate the freezing process through the formation of Ne-rich crystallites.
Scar and antiscar quantum effects in open chaotic systems.
Kaplan, L
1999-05-01
We predict and numerically observe strong periodic orbit effects in the properties of weakly open quantum systems with a chaotic classical limit. Antiscars lead to a large number of exponentially narrow isolated resonances when the single-channel (or tunneling) opening is located on a short unstable orbit of the closed system; the probability to remain in the system at long times is thus exponentially enhanced over the random matrix theory prediction. The distribution of resonance widths and the probability to remain are quantitatively given in terms of only the stability matrix of the orbit on which the opening is placed. The long-time remaining probability density is nontrivially distributed over the available phase space; it can be enhanced or suppressed near orbits other than the one on which the lead is located, depending on the periods and classical actions of these other orbits. These effects of the short periodic orbits on quantum decay rates have no classical counterpart, and first appear on times scales much larger than the Heisenberg time of the system. All the predictions are quantitatively compared with numerical data. PMID:11969492
Mixing effects in the crystallization of supercooled quantum binary liquids.
Kühnel, M; Fernández, J M; Tramonto, F; Tejeda, G; Moreno, E; Kalinin, A; Nava, M; Galli, D E; Montero, S; Grisenti, R E
2015-08-14
By means of Raman spectroscopy of liquid microjets, we have investigated the crystallization process of supercooled quantum liquid mixtures composed of parahydrogen (pH2) or orthodeuterium (oD2) diluted with small amounts of neon. We show that the introduction of the Ne impurities affects the crystallization kinetics in terms of a significant reduction of the measured pH2 and oD2 crystal growth rates, similarly to what found in our previous work on supercooled pH2-oD2 liquid mixtures [Kühnel et al., Phys. Rev. B 89, 180201(R) (2014)]. Our experimental results, in combination with path-integral simulations of the supercooled liquid mixtures, suggest in particular a correlation between the measured growth rates and the ratio of the effective particle sizes originating from quantum delocalization effects. We further show that the crystalline structure of the mixtures is also affected to a large extent by the presence of the Ne impurities, which likely initiate the freezing process through the formation of Ne-rich crystallites. PMID:26277142
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.
Quantum Anomalous Hall Effects and Topological Phase Transitions in Silicene
NASA Astrophysics Data System (ADS)
Ezawa, Motohiko
2013-03-01
Silicene is a monolayer of silicon atoms forming a two-dimensional honeycomb lattice, which is experimentally manufactured this year. The low energy theory is described by Dirac electrons, but they are massive due to a relatively large spin-orbit interaction. I will explain the following properties of silicene: 1) The band structure is controllable by applying an electric field. Silicene undergoes a phase transition from a topological insulator to a band insulator by applying external electric field. 2) The topological phase transition can be detected experimentally by way of diamagnetism. 3) There is a novel circular dichroism and spinvalley selection rules by way of photon absorption. 4) Silicene shows a quantum anomalous Hall effects when ferromagnet is attached onto silicone. 5) Silicene shows a photo-induced quantum Hall effects when we apply strong laser onto silicene. 6) Single Dirac cone state emerges when we apply photo-irradiation and electric field, where the gap is open at the K point and closed at the K' point.
Mixing effects in the crystallization of supercooled quantum binary liquids
NASA Astrophysics Data System (ADS)
Kühnel, M.; Fernández, J. M.; Tramonto, F.; Tejeda, G.; Moreno, E.; Kalinin, A.; Nava, M.; Galli, D. E.; Montero, S.; Grisenti, R. E.
2015-08-01
By means of Raman spectroscopy of liquid microjets, we have investigated the crystallization process of supercooled quantum liquid mixtures composed of parahydrogen (pH2) or orthodeuterium (oD2) diluted with small amounts of neon. We show that the introduction of the Ne impurities affects the crystallization kinetics in terms of a significant reduction of the measured pH2 and oD2 crystal growth rates, similarly to what found in our previous work on supercooled pH2-oD2 liquid mixtures [Kühnel et al., Phys. Rev. B 89, 180201(R) (2014)]. Our experimental results, in combination with path-integral simulations of the supercooled liquid mixtures, suggest in particular a correlation between the measured growth rates and the ratio of the effective particle sizes originating from quantum delocalization effects. We further show that the crystalline structure of the mixtures is also affected to a large extent by the presence of the Ne impurities, which likely initiate the freezing process through the formation of Ne-rich crystallites.
The Quantum Spin Hall Effect: Theory and Experiment
NASA Astrophysics Data System (ADS)
König, Markus; Buhmann, Hartmut; Molenkamp, Laurens W.; Hughes, Taylor; Liu, Chao-Xing; Qi, Xiao-Liang; Zhang, Shou-Cheng
2008-03-01
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 (QWs). By varying the thickness of the QW, the band structure changes from a normal to an “inverted” type at a critical thickness dc. 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 QWs. We review both the fabrication of the sample and the experimental setup. For thin QWs with well width dQW<6.3 nm, the insulating regime shows the conventional behavior of vanishingly small conductance at low temperature. However, for thicker QWs (dQW>6.3 nm), the nominally insulating regime shows a plateau of residual conductance close to 2e2/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, dc=6.3 nm, is also independently determined from the occurrence of a magnetic field induced insulator to metal transition.
Casimir effects for classical and quantum liquids in slab geometry: A brief review
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.
Proceedings of the International Workshop on Quantum Effect Physics, Electronics, and Applications
NASA Astrophysics Data System (ADS)
Smith, Henry
1992-12-01
Quantum Effects Physics, Electronics, and Applications contains contributions presented at an international workshop held in Luxor, Egypt on 6-10 Jan. 1992. Topics covered include: (1) competing concepts and technologies with quantum effects; (2) theoretical calculations and models of bandstructures, transport, fluctuations, and noise in confined geometries; (3) nanofabrication; (4) transport experiments; (5) optical prpoerties and spectroscopy results in vertical superlattices, wires, dots, and arrays of dots and antidots; (6) resonant tunnelling and Coulomb blockade; and (7) applications based on quantum phenomena.
Eides, M.I.; Karshenboim, S.G.; Shelyuto, V.A. )
1991-02-01
The detailed account of analytic calculation of radiative-recoil correction to muonium hyperfine splitting, induced by electron-line radiative insertions, is presented. The consideration is performed in the framework of the effective two-particle formalism. A good deal of attention is paid to the problem of the divergence cancellation and the selection of graphs, relevant to radiative-recoil corrections. The analysis is greatly facilitated by use of the Fried-Yennie gauge for radiative photons. The obtained set of graphs turns out to be gauge-invariant and actual calculations are performed in the Feynman gauge. The main technical tricks, with the help of which we have effectively utilized the existence in the problem of the small parameter-mass ratio and managed to perform all calculations in the analytic form are described. The main intermediate results, as well as the final answer, {delta}E{sub rr} = ({alpha}({Zeta}{alpha})/{pi}{sup 2})(m/M)E{sub F}(6{zeta}(3) + 3{pi}{sup 2} In 2 + {pi}{sup 2}/2 + 17/8), are also presented.
Barrier penetration effects on thermopower in semiconductor quantum wells
Vaidya, R. G.; 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.
The quantum anomalous Hall effect in kagomé lattices
NASA Astrophysics Data System (ADS)
Zhang, Zhi-Yong
2011-09-01
The quantum anomalous Hall (QAH) effect in kagomé lattices is investigated in the presence of both Rashba spin-orbit coupling and an exchange field. In addition to the gap at the Dirac points as found in graphene, a new topological energy gap is opened at the Γ point. With the Fermi energy lying in the first gap, the Chern number 𝒞 = 2 as in graphene, whereas with it lying in the second one, 𝒞 = 1. The distribution of Berry curvature is obtained to reveal the nontrivial topological properties in momentum space. For stripes with ‘armchair’ and ‘zigzag’ edges, the topological characteristics of gapless edge states on the genus g = 2 Riemann surface are studied. The obtained nonzero winding numbers also demonstrate the QAH effect.
Nonequilibrium phonon effects in midinfrared quantum cascade lasers
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.
Quantum Anomalous Hall Effect in Graphene-based Heterostructure.
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.
Anomalous spin Hall effects in Dresselhaus (110) quantum wells
NASA Astrophysics Data System (ADS)
Liu, Ming-Hao; Chang, Ching-Ray
2010-10-01
Anomalous spin Hall effects that belong to the intrinsic type in Dresselhaus (110) quantum wells are discussed. For the out-of-plane spin component, antisymmetric current-induced spin polarization induces opposite spin Hall accumulation, even though there is no spin-orbit force due to Dresselhaus (110) coupling. A surprising feature of this spin Hall induction is that the spin accumulation sign does not change upon bias reversal. Contribution to the spin Hall accumulation from the spin Hall induction and the spin deviation due to intrinsic spin-orbit force as well as extrinsic spin scattering can be straightforwardly distinguished simply by reversing the bias. For the in-plane component, inclusion of a weak Rashba coupling leads to a new type of Sy intrinsic spin Hall effect solely due to spin-orbit-force-driven spin separation.
Quantum Electrodynamics Effects in Rovibrational Spectra of Molecular Hydrogen.
Komasa, Jacek; Piszczatowski, Konrad; Łach, Grzegorz; Przybytek, Michał; Jeziorski, Bogumił; Pachucki, Krzysztof
2011-10-11
The dissociation energies from all rovibrational levels of H2 and D2 in the ground electronic state are calculated with high accuracy by including relativistic and quantum electrodynamics (QED) effects in the nonadiabatic treatment of the nuclear motion. For D2, the obtained energies have theoretical uncertainties of 0.001 cm(-1). For H2, similar uncertainties are for the lowest levels, while for the higher ones the uncertainty increases to 0.005 cm(-1). Very good agreement with recent high-resolution measurements of the rotational v = 0 levels of H2, including states with large angular momentum J, is achieved. This agreement would not have been possible without accurate evaluation of the relativistic and QED contributions and may be viewed as the first observation of the QED effects, mainly the electron self-energy, in a molecular spectrum. For several electric quadrupole transitions, we still observe certain disagreement with experimental results, which remains to be explained.
Role of electrical field in quantum Hall effect of graphene
NASA Astrophysics Data System (ADS)
Luo, Ji
2013-01-01
The ballistic motion of carriers of graphene in an orthogonal electromagnetic field is investigated to explain quantum Hall effect of graphene under experimental conditions. With the electrical field, all electronic eigen-states have the same expectation value of the velocity operator, or classically, all carriers move in cycloid-like curves with the same average velocity. This velocity is the origin of the Hall conductance and its magnitude is just appropriate so that the quantized Hall conductance is exactly independent of the external field. Electrical field changes each Landau level into a bundle of energies. Hall conductance plateaus occur in small fields as bundle gaps exist and are destroyed in intermediate fields as bundles overlap. As the electrical field tends to the critical point, all bundles have the same width, and bundle gaps increase to infinity rapidly. As a result, saturation of the Hall conductance may be observed. Electrical field thus demonstrates nonlinear effects on the Hall conductance.
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…
Application of the quantum Hall effect to resistance metrology
NASA Astrophysics Data System (ADS)
Poirier, Wilfrid; Schopfer, Félicien; Guignard, Jérémie; Thévenot, Olivier; Gournay, Pierre
2011-05-01
The quantum Hall effect (QHE) discovery has revolutionized metrology by providing with a representation of the unit of resistance, R, that can be reproduced within a relative uncertainty of one part in 10 9 and is theoretically only linked to Planck's constant h and the electron charge e. This breakthrough also results from the development of resistance comparison bridges using cryogenic current comparator (CCC). The QHE experimental know-how now allows the realization of perfectly quantized Quantum Hall Array Resistance Standards (QHARS) by combining a large number of single Hall bars. In the context of an evolution of the Système International (SI) of units by fixing some fundamental constants of physics, the determination of the von Klitzing constant R through the use of the so-called Thompson-Lampard calculable capacitor and the realization of refined universality tests of the QHE are of prime importance. Finally, the fascinating graphene material might be a new turning point in resistance metrology.
Quantum Effects in the Diffusion of Hydrogen on Ru(0001).
McIntosh, Eliza M; Wikfeldt, K Thor; Ellis, John; Michaelides, Angelos; Allison, William
2013-05-01
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 spin-echo 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 × 10(9) s(-1), 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
Fractionally charged skyrmions in fractional quantum Hall effect
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
Sagnac effect in a chain of mesoscopic quantum rings
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.
Band Collapse and the Quantum Hall Effect in Graphene
Bernevig, B.Andrei; Hughes, Taylor L.; Zhang, Shou-Cheng; Chen, Han-Dong; Wu, Congjun; /Santa Barbara, KITP
2010-03-16
The recent Quantum Hall experiments in graphene have confirmed the theoretically well-understood picture of the quantum Hall (QH) conductance in fermion systems with continuum Dirac spectrum. In this paper we take into account the lattice, and perform an exact diagonalization of the Landau problem on the hexagonal lattice. At very large magnetic fields the Dirac argument fails completely and the Hall conductance, given by the number of edge states present in the gaps of the spectrum, is dominated by lattice effects. As the field is lowered, the experimentally observed situation is recovered through a phenomenon which we call band collapse. As a corollary, for low magnetic field, graphene will exhibit two qualitatively different QHE's: at low filling, the QHE will be dominated by the 'relativistic' Dirac spectrum and the Hall conductance will be odd-integer; above a certain filling, the QHE will be dominated by a non-relativistic spectrum, and the Hall conductance will span all integers, even and odd.
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].
Quantum-electrodynamics corrections in pionic hydrogen
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.
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.
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.
Recoil ion charge state distribution following the beta(sup +) decay of {sup 21}Na
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.
Revealing compressed stops using high-momentum recoils
Macaluso, Sebastian; Park, Michael; Shih, David; Tweedie, Brock
2016-03-22
In this study, searches for supersymmetric top quarks at the LHC have been making great progress in pushing sensitivity out to higher mass, but are famously plagued by gaps in coverage around lower-mass regions where the decay phase space is closing off. Within the common stop-NLSP/neutralino-LSP simplified model, the line in the mass plane where there is just enough phase space to produce an on-shell top quark remains almost completely unconstrained. Here, we show that is possible to define searches capable of probing a large patch of this difficult region, with S/B ~ 1 and significances often well beyond 5σ.more » The basic strategy is to leverage the large energy gain of LHC Run 2, leading to a sizable population of stop pair events recoiling against a hard jet. The recoil not only re-establishes a ET, but also leads to a distinctive anti-correlation between the ET and the recoil jet transverse vectors when the stops decay all-hadronically. Accounting for jet combinatorics, backgrounds, and imperfections in ET measurements, we estimate that Run 2 will already start to close the gap in exclusion sensitivity with the first few 10s of fb–1. By 300 fb–1, exclusion sensitivity may extend from stop masses of 550 GeV on the high side down to below 200 GeV on the low side, approaching the “stealth” point at mt¯ = mt and potentially overlapping with limits from tt¯ cross section and spin correlation measurements.« less
Revealing compressed stops using high-momentum recoils
NASA Astrophysics Data System (ADS)
Macaluso, Sebastian; Park, Michael; Shih, David; Tweedie, Brock
2016-03-01
Searches for supersymmetric top quarks at the LHC have been making great progress in pushing sensitivity out to higher mass, but are famously plagued by gaps in coverage around lower-mass regions where the decay phase space is closing off. Within the common stop-NLSP/neutralino-LSP simplified model, the line in the mass plane where there is just enough phase space to produce an on-shell top quark remains almost completely unconstrained. Here, we show that is possible to define searches capable of probing a large patch of this difficult region, with S/B ˜ 1 and significances often well beyond 5 σ. The basic strategy is to leverage the large energy gain of LHC Run 2, leading to a sizable population of stop pair events recoiling against a hard jet. The recoil not only re-establishes a [InlineMediaObject not available: see fulltext.] signature, but also leads to a distinctive anti-correlation between the [InlineMediaObject not available: see fulltext.] and the recoil jet transverse vectors when the stops decay all-hadronically. Accounting for jet combinatorics, backgrounds, and imperfections in [InlineMediaObject not available: see fulltext.] measurements, we estimate that Run 2 will already start to close the gap in exclusion sensitivity with the first few 10s of fb-1. By 300 fb-1, exclusion sensitivity may extend from stop masses of 550 GeV on the high side down to below 200 GeV on the low side, approaching the "stealth" point at {m}_{overline{t}}={m}_t and potentially overlapping with limits from toverline{t} cross section and spin correlation measurements.
The exchange-correlation effects on surface plasmon oscillations in semi-bounded quantum plasma
Shahmansouri, Mehran
2015-09-15
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.
B -> D* l nu at zero recoil: an update
Bailey, Jon A.; Bazavov, A.; Bernard, C.; Bouchard, C.M.; DeTar, C.; El-Khadra, A.X.; Freeland, E.D.; Gamiz, E.; Gottlieb, Steven; Heller, U.M.; Hetrick, J.E.
2010-11-01
We present an update of our calculation of the form factor for {bar B} {yields} D*{ell}{bar {nu}} at zero recoil, with higher statistics and finer lattices. As before, we use the Fermilab action for b and c quarks, the asqtad staggered action for light valence quarks, and the MILC ensembles for gluons and light quarks (Luescher-Weisz married to 2+1 rooted staggered sea quarks). In this update, we have reduced the total uncertainty on F(1) from 2.6% to 1.7%.
Projectile paths corrected for recoil and air resistance
NASA Astrophysics Data System (ADS)
Kemp, H. R.
1986-01-01
The angle of projection of a bullet is not the same as the angle of the bore of the firearm just before firing. This is because recoil alters the direction of the barrel as the bullet moves along the barrel. Neither is the angle of projection of an arrow the same as the direction of the arrow just before it is projected. The difficulty in obtaining the angle of projection limits the value of the standard equation for trajectories relative to a horizontal plane. Furthermore, air resistance makes this equation unrealistic for all but short ranges.
Precision lifetime measurements using the recoil distance method
Kruecken, R.
2000-02-01
The recoil distance method (RDM) for the measurements of lifetimes of excited nuclear levels in the range from about 1 ps to 1,000 ps is reviewed. The New Yale Plunger Device for RDM experiments is introduced and the Differential Decay Curve Method for their analysis is reviewed. Results from recent RDM experiments on SD bands in the mass-190 region, shears bands in the neutron deficient lead isotopes, and ground state bands in the mass-130 region are presented. Perspectives for the use of RDM measurements in the study of neutron-rich nuclei are discussed.
The effect of dust size distribution on quantum dust acoustic wave
El-Labany, S. K.; El-Taibany, W. F.; Behery, E. E.; El-Siragy, N. M.
2009-09-15
Based on the quantum hydrodynamics theory, a proposed model for quantum dust acoustic waves (QDAWs) is presented including the dust size distribution (DSD) effect. A quantum version of Zakharov-Kuznetsov equation is derived adequate for describing QDAWs. Two different DSD functions are applied. The relevance of the wave velocity, amplitude, and width to the DSD is investigated numerically. The quantum effect changes only the soliton width. A brief conclusion is presented to the current findings and their relevance to astrophysics data is also discussed.
Group velocity of extraordinary waves in superdense magnetized quantum plasma with spin-1/2 effects
NASA Astrophysics Data System (ADS)
Li, Chunhua; Wu, Zhengwei; Ren, Haijun; Yang, Weihong; Chu, Paul K.
2012-12-01
Based on the one component plasma model, a new dispersion relation and group velocity of elliptically polarized extraordinary electromagnetic waves in a superdense quantum magnetoplasma are derived. The group velocity of the extraordinary wave is modified due to the quantum forces and magnetization effects within a certain range of wave numbers. It means that the quantum spin-1/2 effects can reduce the transport of energy in such quantum plasma systems. Our work should be of relevance for the dense astrophysical environments and the condensed matter physics.
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.
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.
Group velocity of extraordinary waves in superdense magnetized quantum plasma with spin-1/2 effects
Li Chunhua; Ren Haijun; Yang Weihong; Wu Zhengwei; Chu, Paul K.
2012-12-15
Based on the one component plasma model, a new dispersion relation and group velocity of elliptically polarized extraordinary electromagnetic waves in a superdense quantum magnetoplasma are derived. The group velocity of the extraordinary wave is modified due to the quantum forces and magnetization effects within a certain range of wave numbers. It means that the quantum spin-1/2 effects can reduce the transport of energy in such quantum plasma systems. Our work should be of relevance for the dense astrophysical environments and the condensed matter physics.
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.
Framing Anomaly in the Effective Theory of Fractional Quantum Hall Effect
NASA Astrophysics Data System (ADS)
Gromov, Andrey; Abanov, Alexander; Cho, Gil Young; You, Yizhi; Fradkin, Eduardo
2015-03-01
While the classical Chern-Simons theory is topological, it's quantum version is not as it depends on the metric of the base manifold through the path integral measure. This phenomenon is known as the framing anomaly. It is shown that accounting for the framing anomaly of the quantum Chern-Simons theory is essential to obtain the correct gravitational linear response functions of fractional quantum Hall systems (FQH). In the lowest order in gradients the effective action includes Chern-Simons, Wen-Zee and gravitational Chern-Simons terms. The latter term has a contribution from the framing anomaly which fixes the value of thermal Hall conductivity and generates a ``finite size correction'' to the Hall viscosity of the FQH states on a sphere. We also discuss the effects of the framing anomaly on linear responses of non-Abelian FQH states.
NASA Astrophysics Data System (ADS)
Schürmann, D.; Strieder, F.; Di Leva, A.; Gialanella, L.; De Cesare, N.; D'Onofrio, A.; Imbriani, G.; Klug, J.; Lubritto, C.; Ordine, A.; Roca, V.; Röcken, H.; Rolfs, C.; Rogalla, D.; Romano, M.; Schümann, F.; Terrasi, F.; Trautvetter, H. P.
2004-10-01
For improved cross section measurements of the reaction 12C(α,γ)16O in inverted kinematics, a recoil separator ERNA is developed at the 4 MV Dynamitron tandem accelerator in Bochum to detect directly the 16O recoils with high efficiency. The 16O recoils are produced by the 12C projectiles in a windowless 4He gas target. We report on the charge state distribution of the 16O recoils, the gas target density, the beam heating of the gas target, and the acceptance of the separator along the extended gas target.
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.
Performance of a two-state quantum engine improved by the superposition effect
NASA Astrophysics Data System (ADS)
Ou, CongJie; Huang, ZhiFu; Lin, BiHong; Chen, JinCan
2013-10-01
The performance of a two-state quantum engine under different conditions is analyzed. It is shown that the efficiency of the quantum engine can be enhanced by superposing the eigenstates at the beginning of the cycle. By employing the finite-time movement of the potential wall, the power output of the quantum engine as well as the efficiency at the maximum power output (EMP) can be obtained. A generalized potential is adopted to describe a class of two-level quantum engines in a unified way. The results obtained show clearly that the performances of these engines depend on the external potential, the geometric configuration of the quantum engines, and the superposition effect. Moreover, it is found that the superposition effect will enlarge the optimally operating region of quantum engines.
Non-abelian fractional quantum hall effect for fault-resistant topological quantum computation.
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.
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.
NASA Astrophysics Data System (ADS)
Ji, Wei-xiao; Zhang, Chang-wen; Ding, Meng; Zhang, Bao-min; Li, Ping; Li, Feng; Ren, Miao-juan; Wang, Pei-ji; Zhang, Run-wu; Hu, Shu-jun; Yan, Shi-shen
2016-08-01
Bismuth (Bi) has attracted a great deal of attention for its strongest spin–orbit coupling (SOC) strength among main group elements. Although quantum anomalous Hall (QAH) state is predicted in half-hydrogenated Bi honeycomb monolayers Bi2H, the experimental results are still missing. Halogen atoms (X = F, Cl and Br) were also frequently used as modifications, but Bi2X films show a frustrating metallic character that masks the QAH effects. Here, first-principle calculations are performed to predict the full-cyanided bismuthene (Bi2(CN)2) as 2D topological insulator supporting quantum spin Hall state with a record large gap up to 1.10 eV, and more importantly, half-cyanogen saturated bismuthene (Bi2(CN)) as a Chern insulator supporting a valley-polarized QAH state, with a Curie temperature to be 164 K, as well as a large gap reaching 0.348 eV which could be further tuned by bi-axial strain and SOC strength. Our findings provide an appropriate and flexible material family candidate for spintronic and valleytronic devices.
NASA Astrophysics Data System (ADS)
Ji, Wei-xiao; Zhang, Chang-wen; Ding, Meng; Zhang, Bao-min; Li, Ping; Li, Feng; Ren, Miao-juan; Wang, Pei-ji; Zhang, Run-wu; Hu, Shu-jun; Yan, Shi-shen
2016-08-01
Bismuth (Bi) has attracted a great deal of attention for its strongest spin-orbit coupling (SOC) strength among main group elements. Although quantum anomalous Hall (QAH) state is predicted in half-hydrogenated Bi honeycomb monolayers Bi2H, the experimental results are still missing. Halogen atoms (X = F, Cl and Br) were also frequently used as modifications, but Bi2X films show a frustrating metallic character that masks the QAH effects. Here, first-principle calculations are performed to predict the full-cyanided bismuthene (Bi2(CN)2) as 2D topological insulator supporting quantum spin Hall state with a record large gap up to 1.10 eV, and more importantly, half-cyanogen saturated bismuthene (Bi2(CN)) as a Chern insulator supporting a valley-polarized QAH state, with a Curie temperature to be 164 K, as well as a large gap reaching 0.348 eV which could be further tuned by bi-axial strain and SOC strength. Our findings provide an appropriate and flexible material family candidate for spintronic and valleytronic devices.
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.
Magnetoelectric transport and quantum interference effect in ultrathin manganite films
Wang, Cong; Jin, Kui-juan Gu, Lin; Lu, Hui-bin; Li, Shan-ming; Zhou, Wen-jia; Zhao, Rui-qiang; Guo, Hai-zhong; He, Meng; Yang, Guo-zhen
2014-04-21
The magnetoelectric transport behavior with respect to the thicknesses of ultrathin La{sub 0.9}Sr{sub 0.1}MnO{sub 3} films is investigated in detail. The metal-insulator phase transition, which has never been observed in bulk La{sub 0.9}Sr{sub 0.1}MnO{sub 3}, is found in ultrathin films with thicknesses larger than 6 unit cells. Low-temperature resistivity minima appeared in films with thicknesses less than 10 unit cells. This is attributed to the presence of quantum interference effects. These data suggest that the influence of the weak localization becomes much pronounced as the film thickness decreases from 16 to 8 unit cells.
Magnetic quantum coherence effect in Ni4 molecular transistors.
González, 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
Quantum spin Hall effect induced by electric field in silicene
NASA Astrophysics Data System (ADS)
An, Xing-Tao; Zhang, Yan-Yang; Liu, Jian-Jun; Li, Shu-Shen
2013-01-01
We investigate the transport properties in a zigzag silicene nanoribbon in the presence of an external electric field. The staggered sublattice potential and two kinds of Rashba spin-orbit couplings can be induced by the external electric field due to the buckled structure of the silicene. A bulk gap is opened by the staggered potential and gapless edge states appear in the gap by tuning the two kinds of Rashba spin-orbit couplings properly. Furthermore, the gapless edge states are spin-filtered and are insensitive to the non-magnetic disorder. These results prove that the quantum spin Hall effect can be induced by an external electric field in silicene, which may have certain practical significance in applications for future spintronics device.
Simulating Nuclear and Electronic Quantum Effects in Enzymes.
Wang, L; Isborn, C M; Markland, T E
2016-01-01
An accurate treatment of the structures and dynamics that lead to enhanced chemical reactivity in enzymes requires explicit treatment of both electronic and nuclear quantum effects. The former can be captured in ab initio molecular dynamics (AIMD) simulations, while the latter can be included by performing ab initio path integral molecular dynamics (AI-PIMD) simulations. Both AIMD and AI-PIMD simulations have traditionally been computationally prohibitive for large enzymatic systems. Recent developments in streaming computer architectures and new algorithms to accelerate path integral simulations now make these simulations practical for biological systems, allowing elucidation of enzymatic reactions in unprecedented detail. In this chapter, we summarize these recent developments and discuss practical considerations for applying AIMD and AI-PIMD simulations to enzymes. PMID:27498646
Magnetic quantum coherence effect in Ni4 molecular transistors.
González, 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.
Ballistic effects and intersubband excitations in multiple quantum well structures
NASA Astrophysics Data System (ADS)
Schneider, H.; Schönbein, C.; Schwarz, K.; Walther, M.
1998-07-01
We have studied the transport properties of electrons in asymmetric quantum well structures upon far-infrared optical excitation of carriers from the lowest subband into the continuum. Here the photocurrent consists of a coherent component originating from ballistic transport upon excitation, and of an incoherent part associated with asymmetric diffusion and relaxation processes, which occur after the coherence has been lost. The signature of the coherent contribution is provided by a sign reversal of the photocurrent upon changing the excitation energy. This sign reversal arises from the energy-dependent interference between continuum states, which have a twofold degeneracy characterized by positive and negative momenta. The interference effect also allows us to estimate the coherent mean free path ( >20 nm at 77K). In specifically designed device structures, we use both the coherent and incoherent components in order to achieve a pronounced photovoltaic infrared response for detector applications.
Quantum Monte Carlo calculations with chiral effective field theory interactions.
Gezerlis, A; Tews, I; Epelbaum, E; Gandolfi, S; Hebeler, K; Nogga, A; Schwenk, A
2013-07-19
We present the first quantum Monte Carlo (QMC) calculations with chiral effective field theory (EFT) interactions. To achieve this, we remove all sources of nonlocality, which hamper the inclusion in QMC calculations, in nuclear forces to next-to-next-to-leading order. We perform auxiliary-field diffusion Monte Carlo (AFDMC) calculations for the neutron matter energy up to saturation density based on local leading-order, next-to-leading order, and next-to-next-to-leading order nucleon-nucleon interactions. Our results exhibit a systematic order-by-order convergence in chiral EFT and provide nonperturbative benchmarks with theoretical uncertainties. For the softer interactions, perturbative calculations are in excellent agreement with the AFDMC results. This work paves the way for QMC calculations with systematic chiral EFT interactions for nuclei and nuclear matter, for testing the perturbativeness of different orders, and allows for matching to lattice QCD results by varying the pion mass.
Crossed Andreev effects in two-dimensional quantum Hall systems
NASA Astrophysics Data System (ADS)
Hou, Zhe; Xing, Yanxia; Guo, Ai-Min; Sun, Qing-Feng
2016-08-01
We study the crossed Andreev effects in two-dimensional conductor/superconductor hybrid systems under a perpendicular magnetic field. Both a graphene/superconductor hybrid system and an electron gas/superconductor one are considered. It is shown that an exclusive crossed Andreev reflection, with other Andreev reflections being completely suppressed, is obtained in a high magnetic field because of the chiral edge states in the quantum Hall regime. Importantly, the exclusive crossed Andreev reflection not only holds for a wide range of system parameters, e.g., the size of system, the width of central superconductor, and the quality of coupling between the graphene and the superconductor, but also is very robust against disorder. When the applied bias is within the superconductor gap, a robust Cooper-pair splitting process with high-efficiency can be realized in this system.
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.
Quantum finite-size effects in graphene plasmons.
Thongrattanasiri, Sukosin; Manjavacas, Alejandro; García de Abajo, F Javier
2012-02-28
Graphene plasmons are emerging as an alternative solution to noble metal plasmons, adding the advantages of tunability via electrostatic doping and long lifetimes. These excitations have been so far described using classical electrodynamics, with the carbon layer represented by a local conductivity. However, the question remains, how accurately is such a classical description representing graphene? What is the minimum size for which nonlocal and quantum finite-size effects can be ignored in the plasmons of small graphene structures? Here, we provide a clear answer to these questions by performing first-principles calculations of the optical response of doped nanostructured graphene obtained from a tight-binding model for the electronic structure and the random-phase approximation for the dielectric response. The resulting plasmon energies are in good agreement with classical local electromagnetic theory down to ∼10 nm sizes, below which plasmons split into several resonances that emphasize the molecular character of the carbon structures and the quantum nature of their optical excitations. Additionally, finite-size effects produce substantial plasmon broadening compared to homogeneous graphene up to sizes well above 20 nm in nanodisks and 10 nm in nanoribbons. The atomic structure of edge terminations is shown to be critical, with zigzag edges contributing to plasmon broadening significantly more than armchair edges. This study demonstrates the ability of graphene nanostructures to host well-defined plasmons down to sizes below 10 nm, and it delineates a roadmap for understanding their main characteristics, including the role of finite size and nonlocality, thus providing a solid background for the emerging field of graphene nanoplasmonics.
Dynamical Lamb effect versus dissipation in superconducting quantum circuits
NASA Astrophysics Data System (ADS)
Zhukov, A. A.; Shapiro, D. S.; Pogosov, W. V.; Lozovik, Yu. E.
2016-06-01
Superconducting circuits provide a new platform for study of nonstationary cavity QED phenomena. An example of such a phenomenon is the dynamical Lamb effect, which is the parametric excitation of an atom due to nonadiabatic modulation of its Lamb shift. This effect was initially introduced for a natural atom in a varying cavity, while we suggest its realization in a superconducting qubit-cavity system with dynamically tunable coupling. In the present paper, we study the interplay between the dynamical Lamb effect and the energy dissipation, which is unavoidable in realistic systems. We find that despite naive expectations, this interplay can lead to unexpected dynamical regimes. One of the most striking results is that photon generation from vacuum can be strongly enhanced due to qubit relaxation, which opens another channel for such a process. We also show that dissipation in the cavity can increase the qubit excited-state population. Our results can be used for experimental observation and investigation of the dynamical Lamb effect and accompanying quantum effects.
The Quantum Zeno Effect - a Matter of Dynamics, Information or Illusion?
NASA Astrophysics Data System (ADS)
Toschek, Peter E.
Reiterated or continuous measurement on a quantum system impedes the quantum object's evolution. This "quantum Zeno" effect (QZE), contemplated for decades, has been conventionally attributed to the reaction of the measuring device on the quantum object being measured, in the sense of the Heisenberg microscope. However, even reactionless "quantum non-demolition" measurements seem to qualify for that inhibition to take place and may constitute a "quantum Zeno paradox" (QZP). An experimental proof of QZE had been attempted in the past on clouds of ions confined in a Paul trap. In the meantime it has been shown, however, that the anticipated impediment of the quantum evolution by a sheer gain of information, i.e. by reactionless measurement cannot be, in principle, proven with an ensemble. Recently, experiments have been performed with the use of a single quantum system: an 172Yb+ ion, laser-driven on its E2 line S1/2 - D5/2, or an 171Yb+ ion, microwave-driven on its ground-state hyperfine resonance. The results of these experiments demonstrate that mere gain of information on the quantum system, while lacking dynamic action, modifies the system's evolution as it is predicted by quantum mechanics, based on the system's preparation. This seems plausible if we attribute reality to the results of the measurements. If, in contrast, reality is claimed for the prediction, two-fold discontinuity must be admitted: loss of coherence with potential measurements, and renormalization from the results of actual measurements.
Silicon shallow doping by erbium and oxygen recoils implantation
NASA Astrophysics Data System (ADS)
Feklistov, K. V.; Cherkov, A. G.; Popov, V. P.
2016-09-01
In order to get shallow high doping of Si with optically active complexes ErOn, Er followed by O recoils implantation was realized by means of subsequent Ar+ 250-290 keV implantation with doses 2×1015-1×1016 cm-2 through 50-nm deposited films of Er and then SiO2, accordingly. High Er concentration up to 5×1020 cm-3 to the depth of 10 nm was obtained after implantation. However, about a half of the Er implanted atoms become part of surface SiO2 during post-implantation annealing at 950 °C for 1 h in the N2 ambient under a SiO2 cap. The mechanism of Er segregation into the cap oxide following the moving amorphous-crystalline interface during recrystallization was rejected by the transmission electron microscopy (TEM) analysis. Instead, the other mechanism of immobile Er atoms and redistribution of recoil-implanted O atoms toward cap oxide was proposed. It explains the observed formation of two Er containing phases: Er-Si-O phase with a high O content adjacent to the cap oxide and deeper O depleted Er-Si phase. The correction of heat treatments is proposed in order to avoid the above-mentioned problems.
Decay data measurements on 213Bi using recoil atoms.
Marouli, M; Suliman, G; Pommé, S; Ammel, R Van; Jobbágy, V; Stroh, H; Dikmen, H; Paepen, J; Dirican, A; Bruchertseifer, F; Apostolidis, C; Morgenstern, A
2013-04-01
In this work, (213)Bi has been separated from an open (225)Ac source by collecting recoil atoms onto a glass plate in vacuum. The activity of such recoil sources has been measured as a function of time, using an ion-implanted planar Si detector in quasi-2π geometry. From these measurements, a new half-life value of T1/2((213)Bi)=45.62 (6)min was derived. Additionally, high-resolution alpha-spectrometry measurements were performed at a solid angle of 0.4% of 4πsr, to verify the energies and emission probabilities of the α-emissions from (213)Bi. Using (225)Ac, (221)Fr, (217)At and (213)Po peaks as reference peaks, the measured (213)Bi α-peak energies at Eα,0=5878 (4)keV and Eα,1=5560 (4)keV were about 10keV higher than validated data. The relative α-particle emission probabilities of (213)Bi, Pα,0=0.9155 (11) and Pα,1=0.0845 (11), and the (213)Bi alpha branching factor, Pα=1-Pβ=2.140 (10)%, are compatible with recommended values, but have a higher accuracy.
A Measurement of the Recoil Polarization of Electroproduced {Lambda}(1116)
Simeon McAleer
2002-01-01
The CEBAF Large Acceptance Spectrometer at the Thomas Jefferson National Laboratory was used to study the reaction e + p {yields} e{prime} + K{sup +} + {Lambda}(1116) for events where {Lambda}(1116) subsequently decayed via the channel {Lambda}(1116) {yields} p + {pi}{sup -}. Data were taken at incident electron beam energies of 2.5, 4.0, and 4.2 GeV during the 1999 E1C run period. They hyperon production spectra span the Q{sup 2} range from 0.5 to 2.8 GeV{sup 2} and nearly the entire range in the center of mass angles. The proton angular distribution in the {Lambda}(1116) rest frame is used to deduce the recoil polarization of the hyperon, and the W and cos {theta}{sub cm}{sup K+} dependence of the recoil polarization will be presented. The data show sizeable negative polarizations for the {Lambda}(1116) as a function of both cos {theta}{sub cm}{sup K+} and W.
Quantum theory of laser cooling: Statistical description of the process dynamics
NASA Astrophysics Data System (ADS)
Il'enkov, R. Ya.; Prudnikov, O. N.; Taichenachev, A. V.; Yudin, V. I.
2016-07-01
The setting time of the stationary distribution over translational degrees of freedom of two-level atoms in the field of a one-dimensional standing light wave is studied. The dependences of this time on the problem parameters such as the light wave intensity, frequency detuning, and atom mass are obtained. Calculations are performed on the basis of the quantum-mechanical equation for the atomic density matrix taking completely into account the recoil and spatial localization effects in an arbitrarily intense light field.
Clutter attenuation using the Doppler effect in standoff electromagnetic quantum sensing
NASA Astrophysics Data System (ADS)
Lanzagorta, Marco; Jitrik, Oliverio; Uhlmann, Jeffrey; Venegas, Salvador
2016-05-01
In the context of traditional radar systems, the Doppler effect is crucial to detect and track moving targets in the presence of clutter. In the quantum radar context, however, most theoretical performance analyses to date have assumed static targets. In this paper we consider the Doppler effect at the single photon level. In particular, we describe how the Doppler effect produced by clutter and moving targets modifies the quantum distinguishability and the quantum radar error detection probability equations. Furthermore, we show that Doppler-based delayline cancelers can reduce the effects of clutter in the context of quantum radar, but only in the low-brightness regime. Thus, quantum radar may prove to be an important technology if the electronic battlefield requires stealthy tracking and detection of moving targets in the presence of clutter.
First high-statistics and high-resolution recoil-ion data from the WITCH retardation spectrometer
NASA Astrophysics Data System (ADS)
Finlay, P.; Breitenfeldt, M.; Porobić, T.; Wursten, E.; Ban, G.; Beck, M.; Couratin, C.; Fabian, X.; Fléchard, X.; Friedag, P.; Glück, F.; Herlert, A.; Knecht, A.; Kozlov, V. Y.; Liénard, E.; Soti, G.; Tandecki, M.; Traykov, E.; Van Gorp, S.; Weinheimer, Ch.; Zákoucký, D.; Severijns, N.
2016-07-01
The first high-statistics and high-resolution data set for the integrated recoil-ion energy spectrum following the β^+ decay of 35Ar has been collected with the WITCH retardation spectrometer located at CERN-ISOLDE. Over 25 million recoil-ion events were recorded on a large-area multichannel plate (MCP) detector with a time-stamp precision of 2ns and position resolution of 0.1mm due to the newly upgraded data acquisition based on the LPC Caen FASTER protocol. The number of recoil ions was measured for more than 15 different settings of the retardation potential, complemented by dedicated background and half-life measurements. Previously unidentified systematic effects, including an energy-dependent efficiency of the main MCP and a radiation-induced time-dependent background, have been identified and incorporated into the analysis. However, further understanding and treatment of the radiation-induced background requires additional dedicated measurements and remains the current limiting factor in extracting a beta-neutrino angular correlation coefficient for 35Ar decay using the WITCH spectrometer.
Non-equilibrium effects upon the non-Markovian Caldeira-Leggett quantum master equation
Bolivar, A.O.
2011-05-15
Highlights: > Classical Brownian motion described by a non-Markovian Fokker-Planck equation. > Quantization process. > Quantum Brownian motion described by a non-Markovian Caldeira-Leggett equation. > A non-equilibrium quantum thermal force is predicted. - Abstract: We obtain a non-Markovian quantum master equation directly from the quantization of a non-Markovian Fokker-Planck equation describing the Brownian motion of a particle immersed in a generic environment (e.g. a non-thermal fluid). As far as the especial case of a heat bath comprising of quantum harmonic oscillators is concerned, we derive a non-Markovian Caldeira-Leggett master equation on the basis of which we work out the concept of non-equilibrium quantum thermal force exerted by the harmonic heat bath upon the Brownian motion of a free particle. The classical limit (or dequantization process) of this sort of non-equilibrium quantum effect is scrutinized, as well.
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.
Piezoelectric effect in InAs/InP quantum rod nanowires grown on silicon substrate
Anufriev, Roman; Chauvin, Nicolas Bru-Chevallier, Catherine; Khmissi, Hammadi; Naji, Khalid; Gendry, Michel; Patriarche, Gilles
2014-05-05
We report on the evidence of a strain-induced piezoelectric field in wurtzite InAs/InP quantum rod nanowires. This electric field, caused by the lattice mismatch between InAs and InP, results in the quantum confined Stark effect and, as a consequence, affects the optical properties of the nanowire heterostructure. It is shown that the piezoelectric field can be screened by photogenerated carriers or removed by increasing temperature. Moreover, a dependence of the piezoelectric field on the quantum rod diameter is observed in agreement with simulations of wurtzite InAs/InP quantum rod nanowire heterostructures.
Strain-controlled correlation effects in self-assembled quantum dot stacks
NASA Astrophysics Data System (ADS)
Kunert, R.; Schöll, E.
2006-10-01
The authors show that elastic interactions of an array of self-assembled quantum dots in a parent material matrix are markedly distinct from the elastic field created by a single point defect and can explain the observed abrupt correlation-anticorrelation transition in semiconductor quantum dot stacks. Finite volume effects of the quantum dots are shown to lead to sharper transitions. Their analysis also predicts the inclination angle under which the alignment in successive quantum dot layers occurs in dependence on the material anisotropy.
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.
Correlation effects in quantum spin-Hall insulators: a quantum Monte Carlo study.
Hohenadler, M; Lang, T C; Assaad, F F
2011-03-11
We consider the Kane-Mele model supplemented by a Hubbard U term. The phase diagram is mapped out using projective auxiliary field quantum Monte Carlo simulations. The quantum spin liquid of the Hubbard model is robust against weak spin-orbit interaction, and is not adiabatically connected to the spin-Hall insulating state. Beyond a critical value of U>U(c) both states are unstable toward magnetic ordering. In the quantum spin-Hall state we study the spin, charge, and single-particle dynamics of the helical Luttinger liquid by retaining the Hubbard interaction only on a ribbon edge. The Hubbard interaction greatly suppresses charge currents along the edge and promotes edge magnetism but leaves the single-particle signatures of the helical liquid intact.
On quantum effects on the surface of solid hydrogen
Marchenko, V. I.
2013-10-15
The low-frequency spectrum of hypothetical superfluidity on the free surface of a quantum crystal of hydrogen is determined. In the quantum-rough state of the surface, crystallization waves with a quadratic spectrum should propagate. In the atomically smooth state, the spectrum is linear. Crystallization waves propagating along elementary steps are also considered.
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 .
Effects of Landau level mixing on the fractional quantum Hall effect in monolayer graphene.
Peterson, Michael R; Nayak, Chetan
2014-08-22
We report results of exact diagonalization studies of the spin- and valley-polarized fractional quantum Hall effect in the N = 0 and N = 1 Landau levels in graphene. We use an effective model that incorporates Landau level mixing to lowest order in the parameter κ = ((e(2)/εℓ)/(ħv(F)/ℓ)) = (e(2)/εv(F)ħ), which is magnetic field independent and can only be varied through the choice of substrate. We find Landau level mixing effects are negligible in the N = 0 Landau level for κ ≲ 2. In fact, the lowest Landau level projected Coulomb Hamiltonian is a better approximation to the real Hamiltonian for graphene than it is for semiconductor based quantum wells. Consequently, the principal fractional quantum Hall states are expected in the N = 0 Landau level over this range of κ. In the N = 1 Landau level, fractional quantum Hall states are expected for a smaller range of κ and Landau level mixing strongly breaks particle-hole symmetry, producing qualitatively different results compared to the N = 0 Landau level. At half filling of the N = 1 Landau level, we predict the anti-Pfaffian state will occur for κ ∼ 0.25-0.75.
Motion and gravity effects in the precision of quantum clocks
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
Motion and gravity effects in the precision of quantum clocks.
Lindkvist, Joel; Sabín, Carlos; Johansson, Göran; Fuentes, Ivette
2015-05-19
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.
Quantum fluctuations and isotope effects in ab initio descriptions of water
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.
Fractional quantum Hall effect on the two-sphere: A matrix model proposal
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.
Acceleration of positrons by a relativistic electron beam in the presence of quantum effects
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.
Beam suppression of the DRAGON recoil separator for 3He(α,γ)7Be
NASA Astrophysics Data System (ADS)
Sjue, S. K. L.; Nara Singh, B. S.; Adsley, P.; Buchmann, L.; Carmona-Gallardo, M.; Davids, B.; Fallis, J.; Fulton, B. R.; Galinski, N.; Hager, U.; Hass, M.; Howell, D.; Hutcheon, D. A.; Laird, A. M.; Martin, L.; Ottewell, D.; Reeve, S.; Ruiz, C.; Ruprecht, G.; Triambak, S.
2013-02-01
Preliminary studies in preparation for an absolute cross-section measurement of the radiative capture reaction 3He(α,γ)7Be with the DRAGON recoil separator have demonstrated beam suppression >1014 at the 90% confidence level. A measurement of this cross section by observation of 7Be recoils at the focal plane of the separator should be virtually background free.
Eides, M.I.; Karshenboim, S.G.; Shelyuto, V.A. )
1991-02-01
Analytic expression for radiative-recoil corrections to muonium ground-state hyperfine splitting induced by muon-line radiative insertions is obtained. This result completes the program of analytic calculation of all radiative-recoil corrections. The perspectives of further muonium hyperfine splitting investigations are also discussed.
Optimal control of gun recoil in direct fire using magnetorheological absorbers
NASA Astrophysics Data System (ADS)
Singh, Harinder J.; Wereley, Norman M.
2014-05-01
Optimal control of a gun recoil absorber is investigated for minimizing recoil loads and maximizing rate of fire. A multi-objective optimization problem was formulated by considering the mechanical model of the recoil absorber employing a spring and a magnetorheological (MR) damper. The damper forces are predicted by evaluating pressure drops using a nonlinear Bingham-plastic model. The optimization methodology provides multiple optimal design configurations with a trade-off between recoil load minimization and increased rate of fire. The configurations with low or high recoil loads imply low or high rate of fire, respectively. The gun recoil absorber performance is also analyzed for perturbations in the firing forces. The adaptive control of the MR damper for varying gun firing forces provides a smooth operation by returning the recoil mass to its battery position (ready to reload and fire) without incurring an end-stop impact. Furthermore, constant load transmissions are observed with respect to the recoil stroke by implementing optimal control during the simulated firing events.
Kinney, J.H.
1981-07-20
The results of an accurate determination of the recoil spectrum from (n, ..gamma..) reactions in molybdenum are presented. The recoil spectrum has been calculated from nuclear level structure data and measured branching ratios. Angular correlations between successive gammas have been accounted for using the standard theoretical techniques of Racah algebra and the density matrix formalism.
Arapov, Yu. G.; Gudina, S. V.; Neverov, V. N.; Podgornykh, S. M.; Popov, M. R. Harus, G. I.; Shelushinina, N. G.; Yakunin, M. V.; Mikhailov, N. N.; Dvoretsky, S. A.
2015-12-15
The longitudinal and Hall magnetoresistances of HgTe/HgCdTe heterostructures with an inverted energy spectrum (the HgTe quantum well width is d = 20.3 nm) are measured in the quantum-Hall-effect regime at T = 2–50 K in magnetic fields up to B = 9 T. Analysis of the temperature dependences of conductivity in the transition region between the first and second plateaus of the quantum Hall effect shows the feasibility of the scaling regime for a plateau–plateau quantum phase transition in 2D-structures on the basis of mercury telluride.
The trouble with orbits: The Stark effect in the old and the new quantum theory
NASA Astrophysics Data System (ADS)
Duncan, Anthony; Janssen, Michel
2014-11-01
The old quantum theory and Schrödinger's wave mechanics (and other forms of quantum mechanics) give the same results for the line splittings in the first-order Stark effect in hydrogen, the leading terms in the splitting of the spectral lines emitted by a hydrogen atom in an external electric field. We examine the account of the effect in the old quantum theory, which was hailed as a major success of that theory, from the point of view of wave mechanics. First, we show how the new quantum mechanics solves a fundamental problem that one runs into in the old quantum theory with the Stark effect. It turns out that, even without an external field, it depends on the coordinates in which the quantum conditions are imposed which electron orbits are allowed in a hydrogen atom. The allowed energy levels and hence the line splittings are independent of the coordinates used but the size and eccentricity of the orbits are not. In the new quantum theory, this worrisome non-uniqueness of orbits turns into the perfectly innocuous non-uniqueness of bases in Hilbert space. Second, we review how the so-called WKB (Wentzel-Kramers-Brillouin) approximation method for solving the Schrödinger equation reproduces the quantum conditions of the old quantum theory amended by some additional half-integer terms. These extra terms remove the need for some arbitrary extra restrictions on the allowed orbits that the old quantum theory required over and above the basic quantum conditions.
The effect of a mechanical force on quantum reaction rate: quantum Bell formula.
Makarov, Dmitrii E
2011-11-21
The purpose of this note is to derive a quantum-mechanical analog of Bell's formula, which describes the sensitivity of a chemical reaction to a mechanical pulling force. According to this formula, the reaction rate depends exponentially on the force f, i.e., k(f) ~ exp(f/f(c)), where the force scale f(c) is estimated as the thermal energy k(B)T divided by a distance a between the reactant and transition states along the pulling coordinate. Here I use instanton theory to show that, at low temperatures where quantum tunneling is dominant, this force scale becomes f(c) ~ ℏω/a (in the limit where frictional damping is absent) or f(c) ~ ℏτ(-1)/a (in the strong damping limit). Here ω is a characteristic vibration frequency along the pulling coordinate and τ is a characteristic relaxation time in the reactant state. That is, unlike the classical case where f(c) is unaffected by dissipation, this force scale becomes friction dependent in the quantum limit. I further derive higher-order corrections in the force dependence of the rate, describe generalizations to many degrees of freedom, and discuss connection to other quantum rate theories. PMID:22112071
COSY Simulations to Guide Commissioning of the St. George Recoil Mass Separator
NASA Astrophysics Data System (ADS)
Schmitt, Jaclyn; Moran, Michael; Seymour, Christopher; Gilardy, Gwenaelle; Meisel, Zach; Couder, Manoel
2015-10-01
The goal of St. George (STrong Gradient Electromagnetic Online Recoil separator for capture Gamma ray Experiments) is to measure (α, γ) cross sections relevant to stellar helium burning. Recoil separators such as St. George are able to more closely approach the low astrophysical energies of interest because they collect reaction recoils rather than γ-rays, and thus are not limited by room background. In order to obtain an accurate cross section measurement, a recoil separator must be able to collect all recoils over their full range of expected energy and angular spread. The energy acceptance of St. George is currently being measured, and the angular acceptance will be measured soon. Here we present the results of COSY ion optics simulations and magnetic field analyses which were performed to help guide the commissioning measurements and diagnostic upgrades required to complete those measurements. National Science Foundation Research Experiences for Undergraduates program.
Öztekin, İlhan; Akdere, Hakan; Can, Nuray; Aktoz, Tevfik; Arda, Ersan; 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
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
Electrostatically Shielded Quantum Confined Stark Effect Inside Polar Nanostructures
2009-01-01
The effect of electrostatic shielding of the polarization fields in nanostructures at high carrier densities is studied. A simplified analytical model, employing screened, exponentially decaying polarization potentials, localized at the edges of a QW, is introduced for the ES-shielded quantum confined Stark effect (QCSE). Wave function trapping within the Debye-length edge-potential causes blue shifting of energy levels and gradual elimination of the QCSE red-shifting with increasing carrier density. The increase in the e−h wave function overlap and the decrease of the radiative emission time are, however, delayed until the “edge-localization” energy exceeds the peak-voltage of the charged layer. Then the wave function center shifts to the middle of the QW, and behavior becomes similar to that of an unbiased square QW. Our theoretical estimates of the radiative emission time show a complete elimination of the QCSE at doping densities ≥1020 cm−3, in quantitative agreement with experimental measurements. PMID:20596407
Modeling of graphene nanoscroll conductance with quantum capacitance effect
NASA Astrophysics Data System (ADS)
Khaledian, Mohsen; Ismail, Razali
2015-12-01
Graphene nanoscrolls (GNSs) as a new category of quasi one dimensional belong to the carbon-based nanomaterials, which have recently captivated the attention of researchers. The latest discoveries of exceptional structural and electronic properties of GNSs like, high mobility, controllable band gap and tunable core size has become a new stimuli for nanotechnology researchers. Fundamental descriptions about structure and electronic properties of GNSs have been investigated in order to apply them in nanoelectronic applications like nanotransistors and nanosensors as a new semiconducting material. By utilizing a novel approach, the analytical conductance model (G) of GNSs with the effect of Hall quantum is derived. This letter introduces a geometrydependent model to analyze the conductance of GNSs. The conductance modeling of GNS in parabolic part of the band structure which displays minimum conductance near the charge neutrality point is calculated. Subsequently, the effect of temperature and physical parameters on GNS conductivity is studied. This study emphasized that the GNS is a promising candidate for new generation of nanoelectronic devices.
Tuning The Properties of Quantum Dots Via The Effective Mass
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.
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.
Giant Kerr response of ultrathin gold films from quantum size effect
NASA Astrophysics Data System (ADS)
Qian, Haoliang; Xiao, Yuzhe; Liu, Zhaowei
2016-10-01
With the size of plasmonic devices entering into the nanoscale region, the impact of quantum physics needs to be considered. In the past, the quantum size effect on linear material properties has been studied extensively. However, the nonlinear aspects have not been explored much so far. On the other hand, much effort has been put into the field of integrated nonlinear optics and a medium with large nonlinearity is desirable. Here we study the optical nonlinear properties of a nanometre scale gold quantum well by using the z-scan method and nonlinear spectrum broadening technique. The quantum size effect results in a giant optical Kerr susceptibility, which is four orders of magnitude higher than the intrinsic value of bulk gold and several orders larger than traditional nonlinear media. Such high nonlinearity enables efficient nonlinear interaction within a microscopic footprint, making quantum metallic films a promising candidate for integrated nonlinear optical applications.
Giant Kerr response of ultrathin gold films from quantum size effect
Qian, Haoliang; Xiao, Yuzhe; Liu, Zhaowei
2016-01-01
With the size of plasmonic devices entering into the nanoscale region, the impact of quantum physics needs to be considered. In the past, the quantum size effect on linear material properties has been studied extensively. However, the nonlinear aspects have not been explored much so far. On the other hand, much effort has been put into the field of integrated nonlinear optics and a medium with large nonlinearity is desirable. Here we study the optical nonlinear properties of a nanometre scale gold quantum well by using the z-scan method and nonlinear spectrum broadening technique. The quantum size effect results in a giant optical Kerr susceptibility, which is four orders of magnitude higher than the intrinsic value of bulk gold and several orders larger than traditional nonlinear media. Such high nonlinearity enables efficient nonlinear interaction within a microscopic footprint, making quantum metallic films a promising candidate for integrated nonlinear optical applications. PMID:27721498
Effect of Successive Observation on Quantum Cellular Automaton
NASA Astrophysics Data System (ADS)
Inui, Norio; Nakamura, Kazuya; Ide, Yusuke; Konno, Norio
2007-08-01
A quantum cellular automaton, which is extended from a classical cellular automaton with Wolfram’s rule 150, is studied. In contrast to the classical cellular automaton, all possible configurations exist in a quantum superposition before measurement. We show that measuring the state of only one qubit significantly aeffects the time evolution in the quantum cellular automaton. In particular, we demonstrate that, occasionally, repeating the measurement enhances the appearance of the configurations found in the classical cellular automaton. The occurrence of this enhancement is primarily determined by the results of the measurement in the early time steps, and it is sustained by a feedback mechanism.
Hořava-Lifshitz gravity and effective theory of the fractional quantum Hall effect
NASA Astrophysics Data System (ADS)
Wu, Chaolun; Wu, Shao-Feng
2015-01-01
We show that Hořava-Lifshitz gravity theory can be employed as a covariant framework to build an effective field theory for the fractional quantum Hall effect that respects all the spacetime symmetries such as non-relativistic diffeomorphism invariance and anisotropic Weyl invariance as well as the gauge symmetry. The key to this formalism is a set of correspondence relations that maps all the field degrees of freedom in the Hořava-Lifshitz gravity theory to external background (source) fields among others in the effective action of the quantum Hall effect, according to their symmetry transformation properties. We originally derive the map as a holographic dictionary, but its form is independent of the existence of holographic duality. This paves the way for the application of Hořava-Lifshitz holography on fractional quantum Hall effect. Using the simplest holographic Chern-Simons model, we compute the low energy effective action at leading orders and show that it captures universal electromagnetic and geometric properties of quantum Hall states, including the Wen-Zee shift, Hall viscosity, angular momentum density and their relations. We identify the shift function in Hořava-Lifshitz gravity theory as minus of guiding center velocity and conjugate to guiding center momentum. This enables us to distinguish guiding center angular momentum density from the internal one, which is the sum of Landau orbit spin and intrinsic (topological) spin of the composite particles. Our effective action shows that Hall viscosity is minus half of the internal angular momentum density and proportional to Wen-Zee shift, and Hall bulk viscosity is half of the guiding center angular momentum density.
Pfeiffer, P.; Egusquiza, I. L.; Di Ventra, M.; Sanz, M.; Solano, E.
2016-01-01
Technology based on memristors, resistors with memory whose resistance depends on the history of the crossing charges, has lately enhanced the classical paradigm of computation with neuromorphic architectures. However, in contrast to the known quantized models of passive circuit elements, such as inductors, capacitors or resistors, the design and realization of a quantum memristor is still missing. Here, we introduce the concept of a quantum memristor as a quantum dissipative device, whose decoherence mechanism is controlled by a continuous-measurement feedback scheme, which accounts for the memory. Indeed, we provide numerical simulations showing that memory effects actually persist in the quantum regime. Our quantization method, specifically designed for superconducting circuits, may be extended to other quantum platforms, allowing for memristor-type constructions in different quantum technologies. The proposed quantum memristor is then a building block for neuromorphic quantum computation and quantum simulations of non-Markovian systems. PMID:27381511
Pfeiffer, P; Egusquiza, I L; Di Ventra, M; Sanz, M; Solano, E
2016-01-01
Technology based on memristors, resistors with memory whose resistance depends on the history of the crossing charges, has lately enhanced the classical paradigm of computation with neuromorphic architectures. However, in contrast to the known quantized models of passive circuit elements, such as inductors, capacitors or resistors, the design and realization of a quantum memristor is still missing. Here, we introduce the concept of a quantum memristor as a quantum dissipative device, whose decoherence mechanism is controlled by a continuous-measurement feedback scheme, which accounts for the memory. Indeed, we provide numerical simulations showing that memory effects actually persist in the quantum regime. Our quantization method, specifically designed for superconducting circuits, may be extended to other quantum platforms, allowing for memristor-type constructions in different quantum technologies. The proposed quantum memristor is then a building block for neuromorphic quantum computation and quantum simulations of non-Markovian systems. PMID:27381511
Pfeiffer, P; Egusquiza, I L; Di Ventra, M; Sanz, M; Solano, E
2016-07-06
Technology based on memristors, resistors with memory whose resistance depends on the history of the crossing charges, has lately enhanced the classical paradigm of computation with neuromorphic architectures. However, in contrast to the known quantized models of passive circuit elements, such as inductors, capacitors or resistors, the design and realization of a quantum memristor is still missing. Here, we introduce the concept of a quantum memristor as a quantum dissipative device, whose decoherence mechanism is controlled by a continuous-measurement feedback scheme, which accounts for the memory. Indeed, we provide numerical simulations showing that memory effects actually persist in the quantum regime. Our quantization method, specifically designed for superconducting circuits, may be extended to other quantum platforms, allowing for memristor-type constructions in different quantum technologies. The proposed quantum memristor is then a building block for neuromorphic quantum computation and quantum simulations of non-Markovian systems.
NASA Astrophysics Data System (ADS)
Pfeiffer, P.; Egusquiza, I. L.; di Ventra, M.; Sanz, M.; Solano, E.
2016-07-01
Technology based on memristors, resistors with memory whose resistance depends on the history of the crossing charges, has lately enhanced the classical paradigm of computation with neuromorphic architectures. However, in contrast to the known quantized models of passive circuit elements, such as inductors, capacitors or resistors, the design and realization of a quantum memristor is still missing. Here, we introduce the concept of a quantum memristor as a quantum dissipative device, whose decoherence mechanism is controlled by a continuous-measurement feedback scheme, which accounts for the memory. Indeed, we provide numerical simulations showing that memory effects actually persist in the quantum regime. Our quantization method, specifically designed for superconducting circuits, may be extended to other quantum platforms, allowing for memristor-type constructions in different quantum technologies. The proposed quantum memristor is then a building block for neuromorphic quantum computation and quantum simulations of non-Markovian systems.
Calibration of a compact magnetic proton recoil neutron spectrometer
NASA Astrophysics Data System (ADS)
Zhang, Jianfu; Ouyang, Xiaoping; Zhang, Xianpeng; Ruan, Jinlu; Zhang, Guoguang; Zhang, Xiaodong; Qiu, Suizheng; Chen, Liang; Liu, Jinliang; Song, Jiwen; Liu, Linyue; Yang, Shaohua
2016-04-01
Magnetic proton recoil (MPR) neutron spectrometer is considered as a powerful instrument to measure deuterium-tritium (DT) neutron spectrum, as it is currently used in inertial confinement fusion facilities and large Tokamak devices. The energy resolution (ER) and neutron detection efficiency (NDE) are the two most important parameters to characterize a neutron spectrometer. In this work, the ER calibration for the MPR spectrometer was performed by using the HI-13 tandem accelerator at China Institute of Atomic Energy (CIAE), and the NDE calibration was performed by using the neutron generator at CIAE. The specific calibration techniques used in this work and the associated accuracies were discussed in details in this paper. The calibration results were presented along with Monte Carlo simulation results.
Spectroscopy of {sup 144}Ho using recoil-isomer tagging
Mason, P. J. R; Cullen, D. M.; Scholey, C.; Greenlees, P. T.; Jakobsson, U.; Jones, P. M.; Julin, R.; Juutinen, S.; Ketelhut, S.; Leino, M.; Nyman, M.; Peura, P.; Puurunen, A.; Rahkila, P.; Ruotsalainen, P.; Sorri, J.; Saren, J.; Uusitalo, J.; Xu, F. R.
2010-02-15
Excited states in the proton-unbound odd-odd nucleus {sup 144}Ho have been populated using the {sup 92}Mo({sup 54}Fe,pn){sup 144}Ho reaction and studied using the recoil-isomer-tagging technique. The alignment properties and signature splitting of the rotational band above the I{sup p}i=(8{sup +}){sup 144m}Ho isomer have been analyzed and the isomer confirmed to have a pih{sub 11/2} x nuh{sub 11/2} two-quasiparticle configuration. The configuration-constrained blocking method has been used to calculate the shapes of the ground and isomeric states, which are both predicted to have triaxial nuclear shapes with |gamma|approx =24 deg.
Molecular Dynamics Simulation of Energetic Uranium Recoil Damage in Zircon
Devanathan, Ram; Corrales, Louis R.; Weber, William J.; Chartier, Alain; Meis, Constantin
2006-10-11
Defect production and amorphization due to energetic uranium recoils in zircon (ZrSiO4), which is a promising ceramic nuclear waste form, is studied using molecular dynamics simulations with a partial charge model. An algorithm that distinguishes between undamaged crystal, crystalline defects and amorphous regions is used to develop a fundamental understanding of the primary damage state. The amorphous cascade core is separated from the surrounding crystal by a defect-rich region. Small, chemically inhomogeneous amorphous clusters are also produced around the core. The amorphous regions consist of under-coordinated Zr and polymerized Si leading to amorphization and phase separation on a nanometer scale into Zr- and Si-rich regions. This separation could play an important role in the experimentally observed formation of nanoscale ZrO2 in ZrSiO4 irradiated at elevated temperatures.
Neutron absorbed dose determination by calculations of recoil energy.
Wrobel, F; Benabdesselam, M; Iacconi, P; Lapraz, D
2004-01-01
The aim of this work is to calculate the absorbed dose to matter due to neutrons in the 5-150 MeV energy range. Materials involved in the calculations are Al2O3, CaSO4 and CaS, which may be used as dosemeters and have already been studied for their luminescent properties. The absorbed dose is assumed to be mainly due to the energy deposited by the recoils. Elastic reactions are treated with the ECIS code while for the non-elastic ones, a Monte Carlo code has been developed and allowed to follow the nucleus decay and to determine its characteristics (nature and energy). Finally, the calculations show that the absorbed dose is mainly due to non-elastic process and that above 20 MeV this dose decreases slightly with the neutron energy. PMID:15353750
Recoil Polarization for Delta Excitation in Pion Electroproduction
J. J. Kelly; R. E. Roche; Z. Chai; M. K. Jones; O. Gayou; A. J. Sarty; S. Frullani; K. Aniol; E. J. Beise; F. Benmokhtar; W. Bertozzi; W. U. Boeglin; T. Botto; E. J. Brash; H. Breuer; E. Brown; E. Burtin; J. R. Calarco; C. Cavata; C. C. Chang; N. S. Chant; J.-P. Chen; M. Coman; D. Crovelli; R. De Leo; S. Dieterich; S. Escoffier; K. G. Fissum; V. Garde; F. Garibaldi; S. Georgakopoulus; S. Gilad; R. Gilman; C. Glashausser; J.-O. Hansen; D. W. Higinbotham; A. Hotta; G. M. Huber; H. Ibrahim; M. Iodice; C. W. de Jager; X. Jiang; A. Klimenko; A. Kozlov; G. Kumbartzki; M. Kuss; L. Lagamba; G. Laveissiere; J. J. LeRose; R. A. Lindgren; N. Liyanage; G. J. Lolos; R. W. Lourie; D. J. Margaziotis; F. Marie; P. Markowitz; S. McAleer; D. Meekins; R. Michaels; B. D. Milbrath; J. Mitchell; J. Nappa; D. Neyret; C. F. Perdrisat; M. Potokar; V. A. Punjabi; T. Pussieux; R. D. Ransome; P. G. Roos; M. Rvachev; A. Saha; S. Sirca; R. Suleiman; S. Strauch; J. A. Templon; L. Todor; P. E. Ulmer; G. M. Urciuoli; L. B. Weinstein; K. Wijesooriya; B. Wojtsekhowski; X. Zheng; and L. Zhu
2005-08-01
We measured angular distributions of recoil-polarization response functions for neutral pion electroproduction for W=1.23 GeV at Q{sup 2}=1.0 (GeV/c){sup 2}, obtaining 14 separated response functions plus 2 Rosenbluth combinations; of these, 12 have been observed for the first time. Dynamical models do not describe quantities governed by imaginary parts of interference products well, indicating the need for adjusting magnitudes and phases for nonresonant amplitudes. We performed a nearly model-independent multipole analysis and obtained values for Re(S1+/M1+)=-(6.84+/-0.15)% and Re(E1+/M1+)=-(2.91+/-0.19)% that are distinctly different from those from the traditional Legendre analysis based upon M1+ dominance and sp truncation.
Study of nuclear recoils in liquid argon with monoenergetic neutrons
NASA Astrophysics Data System (ADS)
Regenfus, C.; Allkofer, Y.; Amsler, C.; Creus, W.; Ferella, A.; Rochet, J.; Walter, M.
2012-07-01
In the framework of developments for liquid argon dark matter detectors we assembled a laboratory setup to scatter neutrons on a small liquid argon target. The neutrons are produced mono-energetically (Ekin = 2.45 MeV) by nuclear fusion in a deuterium plasma and are collimated onto a 3" liquid argon cell operating in single-phase mode (zero electric field). Organic liquid scintillators are used to tag scattered neutrons and to provide a time-of-flight measurement. The setup is designed to study light pulse shapes and scintillation yields from nuclear and electronic recoils as well as from alpha particles at working points relevant for dark matter searches. Liquid argon offers the possibility to scrutinise scintillation yields in noble liquids with respect to the population strength of the two fundamental excimer states. Here we present experimental methods and first results from recent data towards such studies.
B{yields}D* at zero recoil revisited
Gambino, Paolo; Mannel, Thomas; Uraltsev, Nikolai
2010-06-01
We examine the B{yields}D* form factor at zero recoil using a continuum QCD approach rooted in the heavy quark sum rules framework. A refined evaluation of the radiative corrections as well as the most recent estimates of higher-order power terms together with more careful continuum calculation are included. An upper bound on the form factor of F(1) < or approx. 0.93 is derived, based on just the positivity of inelastic contributions. A model-independent estimate of the inelastic contributions shows they are quite significant, lowering the form factor by about 6% or more. This results in an unbiased estimate F(1){approx_equal}0.86 with about 3% uncertainty in the central value.
Framing Anomaly in the Effective Theory of the Fractional Quantum Hall Effect
NASA Astrophysics Data System (ADS)
Gromov, Andrey; Cho, Gil Young; You, Yizhi; Abanov, Alexander G.; Fradkin, Eduardo
2015-01-01
We consider the geometric part of the effective action for the fractional quantum Hall effect (FQHE). It is shown that accounting for the framing anomaly of the quantum Chern-Simons theory is essential to obtain the correct gravitational linear response functions. In the lowest order in gradients, the linear response generating functional includes Chern-Simons, Wen-Zee, and gravitational Chern-Simons terms. The latter term has a contribution from the framing anomaly which fixes the value of thermal Hall conductivity and contributes to the Hall viscosity of the FQH states on a sphere. We also discuss the effects of the framing anomaly on linear responses for non-Abelian FQH states.
Framing anomaly in the effective theory of the fractional quantum Hall effect.
Gromov, Andrey; Cho, Gil Young; You, Yizhi; Abanov, Alexander G; Fradkin, Eduardo
2015-01-01
We consider the geometric part of the effective action for the fractional quantum Hall effect (FQHE). It is shown that accounting for the framing anomaly of the quantum Chern-Simons theory is essential to obtain the correct gravitational linear response functions. In the lowest order in gradients, the linear response generating functional includes Chern-Simons, Wen-Zee, and gravitational Chern-Simons terms. The latter term has a contribution from the framing anomaly which fixes the value of thermal Hall conductivity and contributes to the Hall viscosity of the FQH states on a sphere. We also discuss the effects of the framing anomaly on linear responses for non-Abelian FQH states.
Quantized anomalous Hall effect in two-dimensional ferromagnets: quantum Hall effect in metals.
Onoda, Masaru; Nagaosa, Naoto
2003-05-23
We study the effect of disorder on the anomalous Hall effect (AHE) in two-dimensional ferromagnets. The topological nature of the AHE leads to the integer quantum Hall effect from a metal, i.e., the quantization of sigma(xy) induced by the localization except for the few extended states carrying Chern numbers. Extensive numerical study on a model reveals that Pruisken's two-parameter scaling theory holds even when the system has no gap with the overlapping multibands and without the uniform magnetic field. Therefore, the condition for the quantized AHE is given only by the Hall conductivity sigma(xy) without the quantum correction, i.e., /sigma(xy)/>e(2)/(2h).
Sub-barrier reactions measured using a recoil mass separator
Betts, R.R.
1988-01-01
Few data exist in the sub-barrier region for reaction channels other than fusion. In particular, our experimental knowledge of quasi-elastic transfer reactions is sparse, despite the belief that this particular channel may be dominant in determining some features of the sub-barrier fusion enhancement. Transfer reactions are governed primarily by the closet approach of the colliding nuclei which, at low energies, results in a strong backward peaking of the angular distribution in the center-of-mass frame. For situations where the projectile has a significant fraction of the target mass, as is so in most cases of interest, the backscattered projectile-like fragment has such low energy that the usual techniques of measurement and identification become invalid. Here, we report on a solution to this problem which allows a systematic study of many aspects of transfer reactions in the energy regime of interest. We exploit the fact that associated with the low-energy backscattered projectile-like fragment is a complementary target-like fragment which recoils to forward angles with a large fraction of the incident beam energy. These target-like fragments were detected and identified using the Daresbury Recoil Mass Separator thus allowing the measurement of quasi-elastic transfer over hitherto inaccessible energy range from the vicinity of the barrier to several tens of MeV below. The experiments described here used VYNi beams of energies ranging from 180 to 260 MeV provided by the Daresbury Laboratory Nuclear Structure Facility tandem accelerator. Data on sub-barrier transfer for targets of /sup 116,118,120,122,124/Sn and /sup 144,148,150,152,154/Sm were obtained. 16 refs., 10 figs., 2 tabs.
Cao, Huajie
2014-11-01
Robust results of WIMP direct detection experiments depend on rm understandings of nuclear recoils in the detector media. This thesis documents the most comprehensive study to date on nuclear recoils in liquid argon - a strong candidate for the next generation multi-ton scale WIMP detectors. This study investigates both the energy partition from nuclear recoil energy to secondary modes (scintillation and ionization) and the pulse shape characteristics of scintillation from nuclear recoils.
A RUNAWAY BLACK HOLE IN COSMOS: GRAVITATIONAL WAVE OR SLINGSHOT RECOIL?
Civano, F.; Elvis, M.; Lanzuisi, G.; Hao, H.; Aldcroft, T.; Jahnke, K.; Zamorani, G.; Comastri, A.; Bolzonella, M.; Blecha, L.; Loeb, A.; Bongiorno, A.; Brusa, M.; Leauthaud, A.; Mainieri, V.; Piconcelli, E.; Salvato, M.; Scoville, N.; Trump, J.; Vignali, C.
2010-07-01
We present a detailed study of a peculiar source detected in the COSMOS survey at z = 0.359. Source CXOC J100043.1+020637, also known as CID-42, has two compact optical sources embedded in the same galaxy. The distance between the two, measured in the HST/ACS image, is 0.''495 {+-} 0.''005 that, at the redshift of the source, corresponds to a projected separation of 2.46 {+-} 0.02 kpc. A large ({approx}1200 km s{sup -1}) velocity offset between the narrow and broad components of H{beta} has been measured in three different optical spectra from the VLT/VIMOS and Magellan/IMACS instruments. CID-42 is also the only X-ray source in COSMOS, having in its X-ray spectra a strong redshifted broad absorption iron line and an iron emission line, drawing an inverted P-Cygni profile. The Chandra and XMM-Newton data show that the absorption line is variable in energy by {Delta}E = 500 eV over four years and that the absorber has to be highly ionized in order not to leave a signature in the soft X-ray spectrum. That these features-the morphology, the velocity offset, and the inverted P-Cygni profile-occur in the same source is unlikely to be a coincidence. We envisage two possible explanations, both exceptional, for this system: (1) a gravitational wave (GW) recoiling black hole (BH), caught 1-10 Myr after merging; or (2) a Type 1/Type 2 system in the same galaxy where the Type 1 is recoiling due to the slingshot effect produced by a triple BH system. The first possibility gives us a candidate GW recoiling BH with both spectroscopic and imaging signatures. In the second case, the X-ray absorption line can be explained as a BAL-like outflow from the foreground nucleus (a Type 2 AGN) at the rearer one (a Type 1 AGN), which illuminates the otherwise undetectable wind, giving us the first opportunity to show that fast winds are present in obscured active galactic nuclei (AGNs), and possibly universal in AGNs.
The role of localized recoil in the formation of Kikuchi patterns.
Winkelmann, Aimo; Vos, Maarten
2013-02-01
In electron scattering from crystals, diffraction spots are replaced by Kikuchi patterns at high momentum transfer. Kikuchi pattern formation is based on the concept of effective incoherent electron sources (or detectors) inside a crystal. The resulting incoherence is a consequence of energy transfer connected with the momentum transfer in large-angle scattering events. We identify atomic recoil as a key incoherent process giving rise to electron Kikuchi patterns in the scope of the "channeling-in and channeling-out" model of electron backscatter diffraction (EBSD) and electron channeling patterns (ECP) in the scanning electron microscope (SEM). Using model calculations, we explore the characteristic role of the localization of the incoherent scattering event at specific places within the unit cell. In this way, we explain why sometimes inelastic losses do cause Kikuchi-type contrast, and sometimes inelastic losses result in the disappearance of this contrast in the SEM.