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1

Recoil Effects in Microwave Ramsey Spectroscopy  

Microsoft Academic Search

We present a theory of recoil effects in two zone Ramsey spectroscopy, particularly adapted to microwave frequency standards using laser cooled atoms. We describe the atoms by a statistical distribution of Gaussian wave packets which enables us to derive and quantify effects that are related to the coherence properties of the atomic source and that have not been considered previously.

Peter Wolf; Christian J. Borde

2004-01-01

2

A Microscopic Recoil Model for Light-Cone Fluctuations in Quantum Gravity  

E-print Network

We present a microscopic model for light-cone fluctuations ``in vacuo'', which incorporates a treatment of quantum-gravitational recoil effects induced by energetic particles. Treating defects in space-time as solitons in string theory, we derive an energy-dependent refractive index and a stochastic spread in the arrival times of mono-energetic photons due to quantum diffusion through space-time foam, as found previously using an effective Born-Infeld action. Distant astrophysical sources provide sensitive tests of these possible quantum-gravitational phenomena.

John Ellis; N. E. Mavromatos; D. V. Nanopoulos

1999-06-07

3

CHEMICAL EFFECTS IN FISSION RECOIL. IV. THE EFFICIENCY OF RECOILING ATOMS IN THE DECOMPOSITION OF POTASSIUM NITRATE  

Microsoft Academic Search

Previous experiments on the decomposition of potassium nitrate by ; fission fragments recoiling from uranium foils have been repeated using thin ; films of uranium oxide enriched in U²³⁵. Fragments recoiling from very ; thin layers are found to be about 2.7 times more efficient in causing ; decomposition than fragments recoiling from an effectively infinitely thick ; source. Measurements

D. Hall; G. N. Walton

1959-01-01

4

Remote recoil: a new wave mean interaction effect  

NASA Astrophysics Data System (ADS)

We present a theoretical study of a fundamentally new wave mean or wave vortex interaction effect able to force persistent, cumulative change in mean flows in the absence of wave breaking or other kinds of wave dissipation. It is associated with the refraction of non-dissipating waves by inhomogeneous mean (vortical) flows. The effect is studied in detail in the simplest relevant model, the two-dimensional compressible flow equations with a generic polytropic equation of state. This includes the usual shallow-water equations as a special case. The refraction of a narrow, slowly varying wavetrain of small-amplitude gravity or sound waves obliquely incident on a single weak (low Froude or Mach number) vortex is studied in detail. It is shown that, concomitant with the changes in the waves' pseudomomentum due to the refraction, there is an equal and opposite recoil force that is felt, in effect, by the vortex core. This effective force is called a remote recoil to stress that there is no need for the vortex core and wavetrain to overlap in physical space. There is an accompanying far-field recoil that is still more remote, as in classical vortex-impulse problems. The remote-recoil effects are studied perturbatively using the wave amplitude and vortex weakness as small parameters. The nature of the remote recoil is demonstrated in various set-ups with wavetrains of finite or infinite length. The effective recoil force {bm R}_V on the vortex core is given by an expression resembling the classical Magnus force felt by moving cylinders with circulation. In the case of wavetrains of infinite length, an explicit formula for the scattering angle theta_* of waves passing a vortex at a distance is derived correct to second order in Froude or Mach number. To this order {bm R}_V {~} theta_*. The formula is cross-checked against numerical integrations of the ray-tracing equations. This work is part of an ongoing study of internal-gravity-wave dynamics in the atmosphere and may be important for the development of future gravity-wave parametrization schemes in numerical models of the global atmospheric circulation. At present, all such schemes neglect remote-recoil effects caused by horizontally inhomogeneous mean flows. Taking these effects into account should make the parametrization schemes significantly more accurate.

Bhler, Oliver; McIntyre, Michael E.

2003-10-01

5

Bursts of Radiation and Recoil Effects in Electromagnetism and Gravitation  

E-print Network

The Maxwell field of a charge e which experiences an impulsive acceleration or deceleration is constructed explicitly by subdividing Minkowskian space-time into two halves bounded by a future null-cone and then glueing the halves back together with appropriate matching conditions. The resulting retarded radiation can be viewed as instantaneous electromagnetic bremsstrahlung. If we similarly consider a spherically symmetric, moving gravitating mass, to experience an impulsive deceleration, as viewed by a distant observer, then this is accompanied by the emission of a light-like shell whose total energy measured by this observer is the same as the kinetic energy of the source before it stops. This phenomenon is a recoil effect which may be thought of as a limiting case of a Kinnersley rocket.

C. Barrabs; P. A. Hogan

2000-12-06

6

CHEMICAL EFFECTS IN FISSION PRODUCT RECOIL. III. THE DECOMPOSTION OF POTASSIUM NITRATE  

Microsoft Academic Search

The effect of the recoil of fission products from uranium foils inio an ; adjacent layer of potassium nitrate was investigated. Under these conditions ; about 10.5 nitrite ions are formed per 100 ev of recoil energy absorbed. This is ; considerably greater than the values observed for other forms of radiation and ; the reasons for this are discussed.

D. Hall; G. N. Walton

1958-01-01

7

Is CHF triggered by the vapor recoil effect?  

E-print Network

This paper deals with the triggering mechanism of the boiling crisis, a transition from nucleate to film boiling. We observe the boiling crisis in pool saturated boiling experimentally at nearly critical pressure to take advantage of the slowness of the bubble growth and of the smallness of the Critical Heat Flux (CHF) that defines the transition point. Such experiments require the reduced gravity conditions. Close to the CHF, the slow growth of the individual dry spots and their subsequent fusion on the transparent heater are observed through the latter. As discussed in the paper, these observations are consistent with numerical results obtained with the vapor recoil model of the boiling crisis.

Nikolayev, Vadim S; Chatain, D

2007-01-01

8

Quantum effects in electron beam pumped GaAs  

SciTech Connect

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.

Yahia, M. E. [Faculty of Engineering, The British University in Egypt (BUE), El-Shorouk City, Cairo (Egypt) [Faculty of Engineering, The British University in Egypt (BUE), El-Shorouk City, Cairo (Egypt); National Institute of Laser Enhanced Sciences (NILES), Cairo University (Egypt); Azzouz, I. M. [National Institute of Laser Enhanced Sciences (NILES), Cairo University (Egypt)] [National Institute of Laser Enhanced Sciences (NILES), Cairo University (Egypt); Moslem, W. M. [Department of Physics, Faculty of Science, Port Said University, Port Said (Egypt)] [Department of Physics, Faculty of Science, Port Said University, Port Said (Egypt)

2013-08-19

9

Observation of the 'head-tail' effect in nuclear recoils of low-energy neutrons  

E-print Network

Directional detection of dark matter can provide unambiguous observation of dark matter interactions even in the presence of background. This article presents an experimental method to measure the direction tag ("head-tail") of the dark matter wind by detecting the scintillation light created by the elastic nuclear recoils in the scattering of dark matter particles with the detector material. The technique is demonstrated by tagging the direction of the nuclear recoils created in the scattering of low-energy neutrons with CF4 in a low-pressure time-projection chamber that is developed by the DMTPC collaboration. The measurement of the decreasing ionization rate along the recoil trajectory provides the direction tag of the incoming neutrons, and proves that the "head-tail" effect can be observed.

D. Dujmic; H. Tomita; M. Lewandowska; S. Ahlen; P. Fisher; S. Henderson; A. Kaboth; G. Kohse; R. Lanza; J. Monroe; A. Roccaro; G. Sciolla; N. Skvorodnev; R. Vanderspek; H. Wellenstein; R. Yamamoto

2007-08-17

10

Quantum Effects In Cosmology  

E-print Network

Contents: Introduction. The Present State of the Universe. What Can We Expect From a Complete Cosmological Theory? An Overview of Quantum Effects in Cosmology. Parametric (Superadiabatic) Amplification of Classical Waves. Graviton Creation in the Inflationary Universe. Quantum States of a Harmonic Oscillator. Squeezed Quantum States of Relic Gravitons and Primordial Density Perturbations. Quantum Cosmology, Minisuperspace Models and Inflation. From the Space of Classical Solutions to the Space of Wave Functions. On the Probability of Quantum Tunneling From "Nothing". Duration of Inflation

L. P. Grishchuk

1993-02-26

11

Improved measurement of the head-tail effect in nuclear recoils  

E-print Network

We present new results with a prototype detector that is being developed by the DMTPC collaboration for the measurement of the direction tag (head-tail) of dark matter wind. We use neutrons from a Cf-252 source to create low-momentum nuclear recoils in elastic scattering with the residual gas nuclei. The recoil track is imaged in low-pressure time-projection chamber with optical readout. We measure the ionization rate along the recoil trajectory, which allows us to determine the direction tag of the incoming neutrons.

D. Dujmic; S. Ahlen; P. Fisher; S. Henderson; A. Kaboth; G. Kohse; R. Lanza; M. Lewandowska; J. Monroe; A. Roccaro; G. Sciolla; N. Skvorodnev; H. Tomita; R. Vanderspek; H. Wellenstein; R. Yamamoto

2008-01-17

12

Effect of recoiled O on damage regrowth and electrical properties of through-oxide implanted Si  

SciTech Connect

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.

Sadana, D.K.; Wu, N.R.; Washburn, J.; Current, M.; Morgan, A.; Reed, D.; Maenpaa, M.

1982-10-01

13

Quantum Effects in Biology  

NASA Astrophysics Data System (ADS)

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, Aln Aspuru-Guzik, Jianshu Cao, Seth Lloyd and Robert Silbey; 3. Generalized Frster resonance energy transfer Seogjoo Jang, Hoda Hossein-Nejad and Gregory D. Scholes; 4. Multidimensional electronic spectroscopy Tom Man?al; 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, Aln 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, Drthe M. Eisele and K. Birgitta Whaley; 15. Coherent excitons in carbon nanotubes Leonas Valkunas and Darius Abramavicius; Glossary; References; Index.

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

2014-08-01

14

Effects of post-Newtonian Spin Alignment on the Distribution of Black-Hole Recoils  

E-print Network

Recent numerical relativity simulations have shown that the final black hole produced in a binary merger can recoil with a velocity as large as 5,000 km/s. Because of enhanced gravitational-wave emission in the so-called "hang-up" configurations, this maximum recoil occurs when the black-hole spins are partially aligned with the orbital angular momentum. We revisit our previous statistical analysis of post-Newtonian evolutions of black-hole binaries in the light of these new findings. We demonstrate that despite these new configurations with enhanced recoil velocities, spin alignment during the post-Newtonian stage of the inspiral will still significantly suppress (or enhance) kick magnitudes when the initial spin of the more massive black hole is more (or less) closely aligned with the orbital angular momentum than that of the smaller hole. We present a preliminary study of how this post-Newtonian spin alignment affects the ejection probabilities of supermassive black holes from their host galaxies with astrophysically motivated mass ratio and initial spin distributions. We find that spin alignment suppresses (enhances) ejection probabilities by ~ 40% (20%) for an observationally motivated mass-dependent galactic escape velocity, and by an even greater amount for a constant escape velocity of 1,000 km/s. Kick suppression is thus at least a factor two more efficient than enhancement.

Emanuele Berti; Michael Kesden; Ulrich Sperhake

2012-03-13

15

Recoil effects of a motional scatterer on single-photon scattering in one dimension  

PubMed Central

The scattering of a single photon with sufficiently high energy can cause a recoil of a motional scatterer. We study its backaction on the photon's coherent transport in one dimension by modeling the motional scatterer as a two-level system, which is trapped in a harmonic potential. While the reflection spectrum is of a single peak in the Lamb-Dicke limit, multi-peaks due to phonon excitations can be observed in the reflection spectrum as the trap becomes looser or the mass of the two-level system becomes smaller. PMID:24220217

Li, Qiong; Xu, D. Z.; Cai, C. Y.; Sun, C. P.

2013-01-01

16

Quantum Effects and Cluster Formation  

E-print Network

The causal interpretation of quantum mechanics is applied to the universe as a whole and the problem of cluster formation is studied in this framework. It is shown that the quantum effects be the source of the cluster formation.

Ali Shojai; Fatimah Shojai

2002-11-13

17

Quantum Effects in Biological Systems  

NASA Astrophysics Data System (ADS)

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.

Roy, Sisir

2014-07-01

18

Effective equations for the quantum pendulum from momentous quantum mechanics  

SciTech Connect

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.

Hernandez, Hector H.; Chacon-Acosta, Guillermo [Universidad Autonoma de Chihuahua, Facultad de Ingenieria, Nuevo Campus Universitario, Chihuahua 31125 (Mexico); Departamento de Matematicas Aplicadas y Sistemas, Universidad Autonoma Metropolitana-Cuajimalpa, Artificios 40, Mexico D. F. 01120 (Mexico)

2012-08-24

19

Spin-Orbit Coupling and Quantum Spin Hall Effect for Neutral Atoms without Spin Flips  

NASA Astrophysics Data System (ADS)

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.

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

2013-11-01

20

Classical and quantum effective theories  

NASA Astrophysics Data System (ADS)

A generalization of the action principle of classical mechanics, motivated by the closed time path scheme of quantum field theory, is presented to deal with initial condition problems and dissipative forces. The similarities of the classical and the quantum cases are underlined. In particular, effective interactions that describe classical dissipative forces represent the system-environment entanglement. The relation between the traditional effective theories and their closed time path extension is briefly discussed, and a few qualitative examples are mentioned.

Polonyi, Janos

2014-09-01

21

Classical and quantum effective theories  

E-print Network

A generalization of the action principle of classical mechanics, motivated by the Closed Time Path (CTP) scheme of quantum field theory, is presented to deal with initial condition problems and dissipative forces. The similarities of the classical and the quantum cases are underlined. In particular, effective interactions which describe classical dissipative forces represent the system-environment entanglement. The relation between the traditional effective theories and their CTP extension is briefly discussed and few qualitative examples are mentioned.

Polonyi, Janos

2014-01-01

22

Transport of Radioactive Material by Alpha Recoil  

SciTech Connect

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.

Icenhour, A.S.

2005-05-19

23

Activity disequilibrium of 230Th, 234U, and 238U in old stilbite: Effects of young U mobility and ?-recoil  

NASA Astrophysics Data System (ADS)

Stilbite from Malmberget and Svappavara is part of hydrothermal mineral assemblages occupying regionally occurring open Palaeoproterozoic fractures in northern Sweden. At these locations, stilbite is characterized by Pb rad excess relative to U and by activity ratios of [ 234U]/[ 238U] > 1 and [ 230Th]/[ 238U] > 1. The activity disequilibrium requires a disturbance of the U-Th systematics within the last one million years. Leaching and infiltration experiments on Malmberget stilbite demonstrate: (i) preferential leaching in the order Pb >U >Th and uptake in the order Pb > U, and (ii) isotopic fractionation of U by preferential mobilization of 238U and 235U relative to 234U. Stepwise-leaching further indicates that the bulk of U is hosted in the channel sites of stilbite. The Th-U disequilibrium systematics observed in untreated Malmberget and Svappavara stilbite can be explained by: (1) addition of U with [ 234U]/[ 238U] > 1 from a fluid, or alternatively (2) loss of U from a two-component system, consisting of a component that is "open" or accessible and a component that is "closed" or inaccessible to mobilization. U addition requires a multistage history involving multiple gain or loss of U and/or Pb. In contrast, U loss does not necessarily require multistage processes but can also be explained by preferential removal of 238U (and 235U) relative to recoiled daughter isotopes such as 234U, 230Th, and 206Pb (and 207Pb) during a single event. Such a behavior could be obtained if the recoiled daughter isotopes of channel-sited uranium are implanted into the crystal lattice and, in such a way, become less mobile than their parent isotopes. This case implies an open-system behavior for ions in the channel sites and a closed-system behavior for ions in the silicate framework of stilbite. Each ?-recoil directly or indirectly, i.e., through its recoil cascade, damages the silicate framework. Subsequent (continuous) low-temperature annealing of the damaged stilbite lattice could trap the recoiled daughter isotopes in the repaired crystal lattice or sealed-off channels. Such immobile recoiled material can, in part, represent the "closed" component of the system. This model can account for all observations regarding the Th-U-Pb systematics, including the Th-U disequilibrium systematics, the similarity in Th/U as deduced from Th-U disequilibrium and Pb isotope data, and the excess of radiogenic Pb ( 208Pb-parents also had been multiply recoiled). These two contrasting explanations involve either multistage or multicomponent systems. They do not permit the derivation of an accurate age.

Romer, Rolf L.; Rocholl, Alexander

2004-11-01

24

Inspiratory Maneuver Effects on Peak Expiratory Flow Role of Lung Elastic Recoil and Expiratory Pressure  

Microsoft Academic Search

We investigated the effects of two different inspiratory maneuvers (fast or slow) on the ability of nor- mal subjects to generate peak expiratory flows (PEF) and maximal dynamic expiratory pressures (Pexp) during the performance of a forced vital capacity maneuver. During the fast maneuver (F), the subject inspired rapidly to total lung capacity (TLC) and immediately performed a maximal expira-

GEORGE E. TZELEPIS; SPYROS ZAKYNTHINOS; THEODORE VASSILAKOPOULOS; STEPHANOS GEROULANOS; CHARIS ROUSSOS

25

Relativistic recoil effects for energy levels in a muonic atom within a Grotch-type approach. II. An application to the one-loop electronic vacuum polarization  

NASA Astrophysics Data System (ADS)

We continue our account of relativistic recoil effects in muonic atoms and present explicitly analytic results at first order in electron-vacuum-polarization effects. The results are obtained within a Grotch-type approach based on an effective Dirac equation. Some expressions are cumbersome and we investigate their asymptotic behavior. Previously, relativistic two-body effects due to the one-loop electron vacuum polarization were studied by several groups. Our results found here are consistent with the previous result derived within a Breit-type approach (including ours) and disagree with a recent attempt to apply a Grotch-type approach.

Ivanov, Vladimir G.; Korzinin, Evgeny Yu.; Karshenboim, Savely G.

2014-02-01

26

Quantum computing of quantum chaos and imperfection effects  

E-print Network

We study numerically the imperfection effects in the quantum computing of the kicked rotator model in the regime of quantum chaos. It is shown that there are two types of physical characteristics: for one of them the quantum computation errors grow exponentially with the number of qubits in the computer while for the other the growth is polynomial. Certain similarity between classical and quantum computing errors is also discussed.

Pil Hun Song; Dima L. Shepelyansky

2000-09-01

27

Electric Field effects on quantum correlations in semiconductor quantum dots  

E-print Network

We study the effect of external electric bias on the quantum correlations in the array of optically excited coupled semiconductor quantum dots. The correlations are characterized by the quantum discord and concurrence and are observed using excitonic qubits. We employ the lower bound of concurrence for thermal density matrix at different temperatures. The effect of the F\\"orster interaction on correlations will be studied. Our theoretical model detects nonvanishing quantum discord when the electric field is on while concurrence dies, ensuring the existence of nonclassical correlations as measured by the quantum discord.

S. Shojaei; M. Mahdian; R. Yousefjani

2012-04-18

28

High acceptance recoil polarimeter  

SciTech Connect

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.

The HARP Collaboration

1992-12-05

29

Comparison of quantum confinement effects between quantum wires and dots  

SciTech Connect

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

Li, Jingbo; Wang, Lin-Wang

2004-03-30

30

Quantum channels and memory effects  

E-print Network

Any physical process can be represented as a quantum channel mapping an initial state into a final state. Hence it can be characterized from the point of view of communication theory, i.e., in terms of its ability in transferring information. Quantum information provides the theoretical framework and the proper mathematical tools to accomplish this. In this context the notion of codes and communication capacities have been introduced by generalizing them from the classical Shannon theory of information transmission and error correction. The underlying assumption of this approach is to consider the channel not as acting on a single system, but on sequences of systems, which, when properly initialized allows one to overcome the noisy effects induced by the physical process under consideration. While most of the work produced so far have been focused on the case where a given channel transformation acts identically and independently on the various elements of the sequence (memoryless configuration in jargon), correlated error models appears to be a more realistic way to approach the problem. A slightly different, yet conceptually related, notion of correlated errors applies to a single quantum system which evolves continuously in time under the influence of an external disturbance which acts on it in a non-Markovian fashion. This leads to the study of memory effects in quantum channels: a fertile ground where interesting novel phenomena emerge at the intersection of quantum information theory with other branches of physics. We survey the field of quantum channels theory on a wide scenario that embraces also these specific and complex settings.

F. Caruso; V. Giovannetti; C. Lupo; S. Mancini

2012-07-23

31

Effects of Spin Quantum Force in Magnetized Quantum Plasma  

NASA Astrophysics Data System (ADS)

Starting from the governing equations for a quantum magnetoplasma including the electron spin -1/2 effects and quantum Bohm potential, we derive Korteweg-de Vries (KdV) equation of the system of quantum magnetohydrodynamics (QMHD). The amplitude and width of magnetosonic soliton with different parameters in the system are studied. It is found that the normalized Zeeman energy E plays a crucial role, for E >= 1 the amplitude rm? and the width w? of solitary wave all decrease as E increases. That is, the introduction of spin quantum force modifies the shape of solitary magnetosonic waves and makes them more narrower and shallower.

Yang, Xiu-Feng; Jiang, Hong; Qi, Xue-Hong; Duan, Wen-Shan

2011-10-01

32

Stochastic resonance effects in quantum channels  

E-print Network

We provide some examples of quantum channels where the addition of noise is able to enhance the information transmission rate. This may happen for both quantum and classical uses and realizes stochastic resonance effects.

Garry Bowen; Stefano Mancini

2005-12-13

33

Nuclear quantum effects in water  

E-print Network

In this work, a path integral Car-Parrinello molecular dynamics 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 methodology. It is shown that these results are in good agreement with neutron Compton scattering data for liquid water and ice.

Joseph A. Morrone; Roberto Car

2008-03-25

34

Quantum gravity effects on space-time  

E-print Network

General relativity promotes space-time to a physical, dynamical object subject to equations of motion. Quantum gravity, accordingly, must provide a quantum framework for space-time, applicable on the smallest distance scales. Just like generic states in quantum mechanics, quantum space-time structures may be highly counter-intuitive. But if low-energy effects can be extracted, they shed considerable light on the implications to be expected for a dynamical quantum space-time. Loop quantum gravity has provided several such effects, but even in the symmetry-reduced setting of loop quantum cosmology no complete picture of effective space-time geometries describing especially the regime near the big bang has been obtained. The overall situation regarding space-time structures and cosmology is reviewed here, with an emphasis on the role of dynamical states, effective equations, and general covariance.

Martin Bojowald

2010-02-12

35

Effects of quantum gravity on black holes  

E-print Network

In this review, we discuss effects of quantum gravity on black hole physics. After a brief review of the origin of the minimal observable length from various quantum gravity theories, we present the tunneling method. To incorporate quantum gravity effects, we modify the Klein-Gordon equation and Dirac equation by the modified fundamental commutation relations. Then we use the modified equations to discuss the tunneling radiation of scalar particles and fermions. The corrected Hawking temperatures are related to the quantum numbers of the emitted particles. Quantum gravity corrections slow down the increase of the temperatures. The remnants are observed as $M_{\\hbox{Res}}\\gtrsim \\frac{M_p}{\\sqrt{\\beta_0}}$. The mass is quantized by the modified Wheeler-DeWitt equation and is proportional to $n$ in quantum gravity regime. The thermodynamical property of the black hole is studied by the influence of quantum gravity effects.

Chen, Deyou; Yang, Haitang; Yang, Shuzheng

2014-01-01

36

The Effect of Dopant Dose Loss during Annealing on Heavily Doped Surface Layers Obtained by Recoil Implantation of Antimony in Silicon  

NASA Astrophysics Data System (ADS)

The aim of our investigation is focused on studying the effect of dopant dose loss during annealing treatments on heavily doped surface layers, obtained by recoil implantation of antimony in silicon. We are interested particularly by the increase of sheet resistance consequently to the shallow junctions obtained at the surface of substrate and the contribution of the dopant dose loss phenomenon following the high concentration of impurities at the surface. In this work, we report some quantitative data concerning the dopant loss at the surface of silicon implanted and its dependence with annealing treatments. Electrical measurements associated with Rutherford backscattering (RBS) technical analysis showed interesting values of sheet resistance compared with classical ion implantation and despite dopant dose loss phenomenon.

Mesli, M. N.; Benbahi, B.; Bouafia, H.; Belmekki, M.; Abidri, B.; Hiadsi, S.

2013-08-01

37

Interpreting Recoil for Undergraduate Students  

ERIC Educational Resources Information Center

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

Elsayed, Tarek A.

2012-01-01

38

Quantum Zeno Effect in the Measurement Problem  

NASA Technical Reports Server (NTRS)

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

Namiki, Mikio; Pasaczio, Saverio

1996-01-01

39

Relativistic Suppression of Black Hole Recoils  

E-print Network

Numerical-relativity simulations indicate that the black hole produced in a binary merger can recoil with a velocity up to v_max ~ 4,000 km/s 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 at their centers despite having escape velocities much less than v_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 Letter, we show that if the spin S_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_1 and L at large separations is 10 degrees while the second spin S_2 is isotropically distributed, the spin alignment discussed in this paper reduces the median recoil from 864 km/s to 273 km/s for maximally spinning black holes with a mass ratio of 9/11. This reduction will greatly increase the fraction of galaxies retaining their supermassive black holes.

Michael Kesden; Ulrich Sperhake; Emanuele Berti

2010-03-25

40

Interaction effects in the mesoscopic regime: A quantum Monte Carlo study of irregular quantum dots  

E-print Network

Interaction effects in the mesoscopic regime: A quantum Monte Carlo study of irregular quantum dots-state properties of isolated irregular quantum dots. Quantum Monte Carlo techniques are used to calculate- mation overpredicts the effects of interactions in quantum dots. DOI: 10.1103/PhysRevB.71.241306 PACS

Baranger, Harold U.

41

Quantum Thermoelectric Effects on the Nanoscale  

NASA Astrophysics Data System (ADS)

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.

Bergfield, Justin; Stafford, Charles

2011-03-01

42

Quantum pigeonhole effect, Cheshire cat and contextuality  

E-print Network

A kind of paradoxical effects has been demonstrated that the pigeonhole principle, i.e., if three pigeons are put in two pigeonholes then at least two pigeons must stay in the same hole, fails in certain quantum mechanical scenario. Here we shall show how to associate a proof of Kochen-Specker theorem with a quantum pigeonhole effect and vise versa, e.g., from state-independent proofs of Kochen-Specker theorem some kind of state-independent quantum pigeonhole effects can be demonstrated. In particular, a state-independent version of the quantum Cheshire cat, which can be rendered as a kind of quantum pigeonhole effect about the trouble of putting two pigeons in two or more pigeonholes, arises from Peres-Mermin's magic square proof of contextuality.

Sixia Yu; C. H. Oh

2014-08-11

43

Nonlocal Effects in Quantum Gravity  

E-print Network

It is shown explicitly that in the framework of Bohmian quantum gravity, the equations of motion of the space-time metric are Einstein's equations plus some quantum corrections. It is observed that these corrections are not covariant. So that in the framework of Bohmian quantum gravity the general covariance principle breaks down at the individual level. This principle is restored at the statistical level.

Ali Shojai; Fatimah Shojai; Mehdi Golshani

1999-03-13

44

How Black Holes Get Their Kicks: Gravitational Radiation Recoil Revisited  

NASA Astrophysics Data System (ADS)

Gravitational waves from the coalescence of binary black holes carry away linear momentum, causing center of mass recoil. This ``radiation rocket'' effect has important implications for systems with escape speeds of order the recoil velocity. We revisit this problem using black hole perturbation theory, treating the binary as a test mass spiraling into a spinning hole. For extreme mass ratios (q?m1/m2<<1), we compute the recoil for the slow in-spiral epoch of binary coalescence very accurately; these results can be extrapolated to q~0.4 with modest accuracy. Although the recoil from the final plunge contributes significantly to the final recoil, we are only able to make crude estimates of its magnitude. We find that the recoil can easily reach ~100-200 km s-1 but most likely does not exceed ~500 km s-1. Although much lower than previous estimates, this recoil is large enough to have important astrophysical consequences. These include the ejection of black holes from globular clusters, dwarf galaxies, and high-redshift dark matter halos.

Favata, Marc; Hughes, Scott A.; Holz, Daniel E.

2004-05-01

45

Integer Quantum Hall Effect at Finite Temperature  

Microsoft Academic Search

On the basis of the field theoretical model of the integer quantum Hall effect developed by Toyoda, Gudmundsson and Takahashi [Physica132A, 164 (1985)] we examine the temperature dependence of the Hall conductivity. The fundamental hypothesis in the theory is the existence of the electron reservoir, which has been experimentally confirmed recently. We discuss the continuous transition from the quantum regime

T. Toyoda; K. Kaneko; F. Suwa; T. Mitani; K. Ito; H. Koizumi

2006-01-01

46

Optimal tunneling enhances the quantum photovoltaic effect in double quantum dots  

E-print Network

We investigate the quantum photovoltaic effect in double quantum dots by applying the nonequilibrium quantum master equation. A drastic suppression of the photovoltaic current is observed near the open circuit voltage, ...

Wang, Chen

47

Recoil Based Fuel Breeding Fuel Structure  

SciTech Connect

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

Popa-Simil, Liviu [R and D, LAVM LLC., Los Alamos, NM, 87544 (United States)

2008-07-01

48

RECOILING SUPERMASSIVE BLACK HOLES IN SPIN-FLIP RADIO GALAXIES  

SciTech Connect

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.

Liu, F. K.; Wang Dong [Department of Astronomy, Peking University, 100871 Beijing (China); Chen Xian, E-mail: fkliu@pku.edu.cn [Kavli Institute for Astronomy and Astrophysics, Peking University, 100871 Beijing (China)

2012-02-20

49

Locality and universality of quantum memory effects  

NASA Astrophysics Data System (ADS)

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.

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

2014-09-01

50

Classification of macroscopic quantum effects  

E-print Network

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

Tristan Farrow; Vlatko Vedral

2014-06-03

51

Quantum Computing and Lie Theory Feynman's suggestion that the only effective way to model quantum phe-  

E-print Network

Quantum Computing and Lie Theory Feynman's suggestion that the only effective way to model quantum phe- nomena on a computer would be to build a computer that made use of quantum mechanics was one that a quantum computer could, in theory, factor large integers or do discrete logarithms in polynomial time

D'Agnolo, Andrea

52

Blue quantum electroabsorption modulators based on reversed quantum confined Stark effect with blueshift  

E-print Network

Blue quantum electroabsorption modulators based on reversed quantum confined Stark effect of blue quantum electroabsorption modulators that incorporate 5 nm thick In0.35Ga0.65N/GaN quantum cm-1 for 6 V bias swing around 424 nm, holding promise for blue optical clock generation

Demir, Hilmi Volkan

53

Casimir effect in a quantum space-time  

E-print Network

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

Gambini, Rodolfo; Pullin, Jorge

2014-01-01

54

Quantum metrology and detection of Unruh effect  

E-print Network

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

Jieci Wang; Zehua Tian; Jiliang Jing; Heng Fan

2014-05-08

55

The effects of nonextensivity on quantum dissipation  

PubMed Central

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

Choi, Jeong Ryeol

2014-01-01

56

Using the Quantum Zeno Effect for the Suppression of Decoherence  

E-print Network

Projective measurements are an essential element of quantum mechanics. In most cases, they cause an irreversible change of the quantum system on which they act. However, measurements can also be used to stabilize quantum states from decay processes, which is known as the Quantum Zeno Effect. Here, we demonstrate this effect for the case of superposition states of nuclear spin qubits, using an ancilla to perform the measurement. As a result, the quantum state of the qubit is protected against dephasing.

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

2014-06-27

57

Median recoil direction as a WIMP directional detection signal  

SciTech Connect

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.

Green, Anne M. [School of Physics and Astronomy, University of Nottingham, University Park, Nottingham, NG7 2RD (United Kingdom); Morgan, Ben [Department of Physics, University of Warwick, Coventry, CV4 7AL (United Kingdom)

2010-03-15

58

The Quantum Hall Effect File from a talk given at the International School "Quantum Metrology and  

E-print Network

The Quantum Hall Effect File from a talk given at the International School "Quantum Metrology&BJ, 1992 Von Klitzing, et al, PRL 1980 3 #12;Electron Focusing skipping orbit electron focusing van Houten

Paris-Sud 11, Université de

59

Quantum Effects in Black Hole Interiors  

E-print Network

The Weyl curvature inside a black hole formed in a generic collapse grows, classically without bound, near to the inner horizon, due to partial absorption and blueshifting of the radiative tail of the collapse. Using a spherical model, we examine how this growth is modified by quantum effects of conformally coupled massless fields.

Warren G. Anderson; Patrick R. Brady; Werner Israel; Sharon M. Morsink

1992-10-23

60

Thermal disequilibrium effects in quantum reflection  

SciTech Connect

We show that the quantum reflection coefficient of ultracold heavy atoms scattering off a dielectric surface can be tuned in a wide range by suitable choice of surface and environment temperatures. This effect results from a temperature-dependent repulsive part of the van der Waals-Casimir-Polder-Lifshitz atom-surface interaction potential.

Druzhinina, Viola; Mudrich, Marcel; Buchleitner, Andreas [Physikalisches Institut, Albert-Ludwigs Universitaet Freiburg, D-79104 Freiburg (Germany); Arnecke, Florian; Madronero, Javier [Physik Department, Technische Universitaet Muenchen, D-85747 Garching (Germany)

2010-09-15

61

22 years of quantum Hall effect metrology  

Microsoft Academic Search

Summary form only given. This talk will be a review of the history of quantum Hall effect metrology from a personal point of view since I had the chance to participate in this history from the beginning. At CPEM 80 von Klitzing introduced his discovery to the metrological community. The question arose, if there is a possible metrological application. Consequently

E. Braun

2002-01-01

62

The Quantum Hall Effect in Graphene  

E-print Network

We investigate the quantum Hall effect in graphene. We argue that in graphene in presence of an external magnetic field there is dynamical generation of mass by a rearrangement of the Dirac sea. We show that the mechanism breaks the lattice valley degeneracy only for the $n=0$ Landau levels and leads to the new observed $\

Paolo Cea

2011-01-29

63

Effective equilibrium theory of nonequilibrium quantum transport  

NASA Astrophysics Data System (ADS)

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.

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

2011-12-01

64

Protecting entanglement via the quantum Zeno effect  

E-print Network

We study the exact entanglement dynamics of two atoms in a lossy resonator. Besides discussing the steady-state entanglement, we show that in the strong coupling regime the system-reservoir correlations induce entanglement revivals and oscillations and propose a strategy to fight against the deterioration of the entanglement using the quantum Zeno effect.

Sabrina Maniscalco; Francesco Francica; Rosa L. Zaffino; Nicola Lo Gullo; Francesco Plastina

2007-10-21

65

Gravitation: global formulation and quantum effects  

NASA Astrophysics Data System (ADS)

A non-integrable phase-factor global approach to gravitation is developed by using the similarity of teleparallel gravity to electromagnetism. The phase shifts of both the COW and the gravitational Aharonov Bohm effects are obtained. It is then shown, by considering a simple slit experiment, that in the classical limit the global approach yields the same result as the gravitational Lorentz force equation of teleparallel gravity. It represents, therefore, the quantum mechanical version of the classical description provided by the gravitational Lorentz force equation. As teleparallel gravity can be formulated independently of the equivalence principle, it will consequently require no generalization of this principle at the quantum level.

Aldrovandi, R.; Pereira, J. G.; Vu, K. H.

2004-01-01

66

RECOIL LABELING OF ORGANIC COMPOUNDS  

Microsoft Academic Search

The results of C¹⁴-labeling under neutron irradiation of two ; groups of compounds are reported: (1) naphthalene, phenanthrene, and anthracene ; in an attempt to determine whether or not high energy C¹⁴ fragments formed ; by nuclear recoil would favor or discriminate against any particular position in ; product formations; (2) pseudoephedrine, 2-amino-pyrimidine, and 3,6-; dihydroxypyridazine as complex nitrogen-containing compounds.

S. Oae; M. Hamada; Y. Otsuji; N. Furukawa; E. Iwamoto

1963-01-01

67

Quantum Anomalous Hall Effect in Hg_1-yMn_yTe Quantum Wells  

SciTech Connect

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.

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

2010-03-19

68

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

69

Variety of Effects of Decoherence in Quantum Algorithms  

NASA Astrophysics Data System (ADS)

Quantum computations have so far proved to be more powerful than classical computations, but quantum computers still have not been put into practical use due to several technical issues. One of the most serious problems for realizing quantum computers is decoherence that occurs inevitably since our apparatus are surrounded with environment and open systems. In this paper, we give some surveys on a variety of effects of decoherence in quantum algorithms such as Grover's database search and quantum walks, and we show how quantum algorithms work under decoherence, how sensitive they are against decoherence, and how to implement a robust quantum circuit.

Hasegawa, Jun

70

Gravitational Wave Recoil and the Retention of Intermediate-Mass Black Holes  

Microsoft Academic Search

During the inspiral and merger of a binary black hole, gravitational radiation is emitted anisotropically due to asymmetries in the merger configuration. This anisotropic radiation leads to a gravitational wave kick, or recoil velocity, as large as ~4000 km s-1. We investigate the effect gravitational recoil has on the retention of intermediate-mass black holes (IMBHs) within the population of Galactic

Kelly Holley-Bockelmann; Kayhan Gltekin; Deirdre Shoemaker; Nicolas Yunes

2008-01-01

71

Enhancing the sensitivity of recoil-beta tagging  

NASA Astrophysics Data System (ADS)

Tagging with ?-particles at the focal plane of a recoil separator has been shown to be an effective technique for the study of exotic proton-rich nuclei. This article describes three new pieces of apparatus used to greatly improve the sensitivity of the recoil-beta tagging technique. These include a highly-pixelated double-sided silicon strip detector, a plastic phoswich detector for discriminating high-energy ?-particles, and a charged-particle veto box. The performance of these new detectors is described and characterised, and the resulting improvements are discussed.

Henderson, J.; Ruotsalainen, P.; Jenkins, D. G.; Scholey, C.; Auranen, K.; Davies, P. J.; Grahn, T.; Greenlees, P. T.; Henry, T. W.; Herz?, A.; Jakobsson, U.; Joshi, P.; Julin, R.; Juutinen, S.; Konki, J.; Leino, M.; Lotay, G.; Nichols, A. J.; Obertelli, A.; Pakarinen, J.; Partanen, J.; Peura, P.; Rahkila, P.; Sandzelius, M.; Sarn, J.; Sorri, J.; Stolze, S.; Uusitalo, J.; Wadsworth, R.

2013-04-01

72

Quantum fluid model of coherent stimulated radiation by a dense relativistic cold electron beam  

SciTech Connect

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}?{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}/?{sub c})?{sup 3/2}, with ?{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.

Monteiro, L. F.; Serbeto, A.; Tsui, K. H. [Instituto de Fsica, Universidade Federal Fluminense, Campus da Praia Vermelha, Niteri, RJ 24210-346 (Brazil)] [Instituto de Fsica, Universidade Federal Fluminense, Campus da Praia Vermelha, Niteri, RJ 24210-346 (Brazil); Mendona, J. T.; Galvo, R. M. O. [Instituto de Fsica, Universidade de So Paulo, So Paulo, SP 05508-090 (Brazil)] [Instituto de Fsica, Universidade de So Paulo, So Paulo, SP 05508-090 (Brazil)

2013-07-15

73

Grand unification and enhanced quantum gravitational effects.  

PubMed

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

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

2008-10-24

74

Mobilization of thorium, radium and radon radionuclides in ground water by successive alpha-recoils  

NASA Astrophysics Data System (ADS)

Alpha-recoil is an important way for the mobilization of ?-decay daughters in ground water. The processes of decay and recoil from 238U to 222Rn and from 232Th to 220Rn are successive. The release rates of successive recoils in this study are quantitatively estimated under two extreme conditions: complete absorption; and no adsorption of recoil elements by the porous medium. The recoil probability, recoil embedding and effective surface area are considered during the analysis. The result of this study shows that the recoil supply rates in the porous medium decrease down the decay chains. For the isotopes within the same decay chains, recoil emanation ratios of daugthers to parent are usually greater than 1 under both end-member conditions. This is consistent with the higher daughter to parent ratios observed in the field measurements. It is also found that the emanation ratios of Th, Ra and Rn show little change with the change of porosity in general. Radon emanation is most efficient at 15-20% porosity under the condition of complete adsorption. The calculated radioactivity ratios of daughters to parents from this study can provide a partial explanation for the disequilibrium of radioactivity of daughters relative to parents observed in natural water. Because of the low solubility of thorium, radium and radon, the emanation rates calculated under the condition of complete adsorption are closer to the natural conditions.

Sun, Hongbing; Semkow, Thomas M.

1998-02-01

75

Topological Quantum Computation by Manipulating Quantum Tunneling Effect of the Toric Codes  

E-print Network

Quantum computers are predicted to utilize quantum states to perform memory and to process tasks far faster than those of conventional classical computers. In this paper we show a new road towards building fault tolerance quantum computer by tuning quantum tunneling effect of the degenerate quantum states in topological order, instead of by braiding anyons. Using a designer Hamiltonian - the Wen-Plaquette model as an example, we study its quantum tunneling effect of the toric codes and show how to control the toric code to realize topological quantum computation (TQC). In particular, we give a proposal to the measurement of TQC. In the end the realization of the Wen-Plaquette model in cold atoms is discussed.

Su-Peng Kou

2008-05-18

76

Quantum Coherence Effects in Novel Quantum Optical Systems  

E-print Network

Optical response of an active medium can substantially be modified when coherent superpositions of states are excited, that is, when systems display quantum coherence and interference. This has led to fascinating applications in atomic and molecular...

Sete, Eyob Alebachew

2012-10-19

77

Memory Effects in Quantum Channel Discrimination Giulio Chiribella,1  

E-print Network

Memory Effects in Quantum Channel Discrimination Giulio Chiribella,1 Giacomo M. D'Ariano,1 quantum-memory assisted protocols for discriminating quantum channels. We show that for optimal discrimination of memory channels, memory assisted protocols are needed. This leads to a new notion of distance

D'Ariano, Giacomo Mauro

78

Elastic recoil changes in early emphysema  

Microsoft Academic Search

An attempt was made to determine if emphysema and static lung recoil were related in a group of 65 excised human lungs. We studied 23 normal lungs, 24 lungs with an emphysema score of 5 or less, and 18 lungs with an emphysema score greater than 5. A comparison of the percentage of predicted elastic recoil revealed that both emphysema

G W Silvers; T L Petty; R E Stanford

1980-01-01

79

Oscillatory quantum screening effects on the positronium (Ps) formation in quantum plasmas  

SciTech Connect

The oscillatory quantum screening effects on the positronium formation by the positron are investigated in quantum plasmas. It is found that the oscillatory screening effects suppress the positronium formation radius as well as the positronium formation cross section. It is also found that the positronium formation radius decreases with increasing quantum wave number. It is found that the peak position of the differential cross section is receded from the projectile with decreasing quantum wave number. In addition, the oscillatory screening effects on the positronium formation cross section are found to be decreased with an increase of the collision energy.

Kim, Chang-Geun [National Center for Standard Reference Data, Korea Research Institute of Standards and Science, Doryong-Dong, Yuseong-Gu, Daejeon 305-340 (Korea, Republic of); Jung, Young-Dae [Department of Applied Physics, Hanyang University, Ansan, Kyunggi-Do 426-791 (Korea, Republic of)

2011-11-07

80

Recoil-ion momentum spectroscopy: Ionization in ion-atom collisions  

NASA Astrophysics Data System (ADS)

The rapid development in the field of recoil-ion momentum spectroscopy now allows one to perform complete momentum experiments of all the reaction products for single target ionization. This experimental technique can address distinct features characterizing ionization processes in ion-atom collisions and can serve as a most stringent test for theory. The quantum mechanical models used most commonly in the description of ion-atom ionization will be discussed. In particular we will survey some new theoretical results which will illustrate the suitability of the continuum-distorted-wave (CDW) and continuum-distorted-wave eikonal-initial-state (CDW-EIS) models for both high and low Z projectiles in fast ion-atom collisions. The influence of the post collision interaction (PCI) effects in these collisions will also examined.

O'Rourke, S. F. C.; Schmitt, W.; Kendrick, J.; Khayyat, Kh; Moshammer, R.; Ullrich, J.; Drner, R.; Schmidt-Bcking, H.

1999-06-01

81

Enhanced light response of proton recoils and PSD effects in the detection of 14 MeV neutrons by organic liquid scintillators  

NASA Astrophysics Data System (ADS)

Monte Carlo (MC) calculations of the response function of NE213 organic liquid scintillators have been compared with measurements at 2.4 and 13.9 MeV neutron energy, with the purpose of tuning the calculation parameters of detection efficiency vs threshold in the neutron energy range from 1 to 14 MeV. A successful reproduction of the experimental response function has been achieved only enhancing the light yield of recoil protons with respect to the values accepted until now. The experimental depletion of the neutron response function at 13.9 MeV caused by neutron-?-ray pulse shape discrimination, instead, was not reproduced by MC calculations even after reasonable changes of the related input cross sections.

Pantaleo, A.; Fiore, L.; Guarino, G.; Paticchio, V.; D'Erasmo, G.; Fiore, E. M.; Colonna, N.

1990-06-01

82

Recoil resolution and particle stability under irradiation  

NASA Astrophysics Data System (ADS)

The stability of a dispersion of particles may be affected by resolution due to radiation recoil. Simple models of the diffusion of solute that recoils into the matrix allow an estimate of when this process will be important, leading either to the complete dissolution of the particles or to inverse coarsening in which small particles grow and large particles shrink. We first find the concentration profile for which solute diffuses back to a particle as fast as it is expelled by recoils. The transient concentration profiles in the matrix demonstrate the time required to approach steady state. The solution for a single particle is then used to calculate the rate of inverse coarsening by the diffusion of solute from the region near large particles to the region near small particles. The rate of growth or shrinkage depends directly on the recoil rate and the recoil distance cubed. It depends only weakly on the particle spacing and not at all on the diffusion coefficient.

Frost, H. J.; Russell, K. C.

83

An introduction to the quantum backflow effect  

NASA Astrophysics Data System (ADS)

We present an introduction to the backflow effect in quantum mechanics - the phenomenon in which a state consisting entirely of positive momenta may have negative current and the probability flows in the opposite direction to the momentum. We show that the effect is present even for simple states consisting of superpositions of gaussian wave packets, although the size of the effect is small. Inspired by the numerical results of Penz et al, we present a wave function whose current at any time may be computed analytically and which has periods of significant backflow, with a backwards flux equal to about 70 percent of the maximum possible backflow, a dimensionless number cbm ? 0.04, discovered by Bracken and Melloy. This number has the unusual property of being independent of hslash (and also of all other parameters of the model), despite corresponding to a quantum-mechanical effect, and we shed some light on this surprising property by considering the classical limit of backflow. We conclude by discussing a specific measurement model in which backflow may be identified in certain measurable probabilities.

Yearsley, J. M.; Halliwell, J. J.

2013-06-01

84

Simulation of recoil trajectories in gas-filled magnetic separators  

NASA Astrophysics Data System (ADS)

A computer code has been developed to simulate the production of heavy element compound nucleus recoils and their trajectories through gas-filled magnetic separators. The simulation is carried out in three steps: positions and trajectories of heavy element recoils in the target layer, propagation through remaining target material, and trajectories through the gas-filled separator. Separators with quite different magnetic configurations are modeled: the Berkeley gas-filled separator (BGS) and two magnetic configurations for the TransActinide separator and chemistry apparatus (TASCA). While computing trajectories through the gas-filled separator, special attention is paid to the charge exchange/equilibration and scattering in the gas. New features of these simulations include mixed He/H2/N2 gas operation and a gas density (pressure) effect. Numerical procedures used in the simulations are explained in detail. Results of the simulations are presented, showing the gas mixtures/pressures that result in the highest efficiency for collecting compound nucleus recoils at the focal plane of the gas-filled separator. Comparison between simulation and experimental results are presented for average recoil ion charge in various gases, focal plane image size, and magnetic rigidity dispersion.

Gregorich, K. E.

2013-05-01

85

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

NASA Astrophysics Data System (ADS)

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

SalmanOgli, A.; Rostami, R.

2013-10-01

86

The Collective Atomic Recoil Laser  

SciTech Connect

An ensemble of periodically ordered atoms coherently scatters the light of an incident laser beam. The scattered and the incident light may interfere and give rise to a light intensity modulation and thus to optical dipole forces which, in turn, emphasize the atomic ordering. This positive feedback is at the origin of the collective atomic recoil laser (CARL). We demonstrate this dynamics using ultracold atoms confined by dipole forces in a unidirectionally pumped far red-detuned high-finesse optical ring cavity. Under the influence of an additional dissipative force exerted by an optical molasses the atoms, starting from an unordered distribution, spontaneously form a density grating moving at constant velocity. Additionally, steady state lasing is observed in the reverse direction if the pump laser power exceeds a certain threshold. We compare the dynamics of the atomic trajectories to the behavior of globally coupled oscillators, which exhibit phase transitions from incoherent to coherent states if the coupling strength exceeds a critical value.

Courteille, Ph.W.; Cube, C. avon; Deh, B.; Kruse, D.; Ludewig, A.; Slama, S.; Zimmermann, C. [Physikalisches Institut, Eberhard-Karls-Universitaet Tuebingen, Auf der Morgenstelle 14, D-72076 Tuebingen (Germany)

2005-05-05

87

Optical evidence for Aharonov Bohm effect in quantum tubes  

NASA Astrophysics Data System (ADS)

We present an optical evidence for Aharonov-Bohm (AB) effect in InAs quantum tubes fabricated by a selective area-metal organic vapor phase epitaxy. The oscillations of the photoluminescence peak energies are observed in quantum tubes depending on the magnetic flux through the tube. These oscillations in energies are shown to be due to the AB effect of a charged exciton in a quantum tube by a theory based on the effective-mass approximation.

Nomura, S.; Tsumura, K.; Mohan, P.; Motohisa, J.; Fukui, T.

2008-03-01

88

Nuclear recoil correction to the g factor of boron-like argon  

E-print Network

The nuclear recoil effect to the g factor of boron-like ions is investigated. The one-photon-exchange correction to the nuclear recoil effect is calculated in the non-relativistic approximation for the nuclear recoil operator and in the Breit approximation for the interelectronic-interaction operator. The screening potential is employed to estimate the higher-order contributions. The updated g-factor values are presented for the ground 2P_1/2 and first excited 2P_3/2 states of B-like argon 40^Ar^13+, which are presently being measured by the ARTEMIS group at GSI.

Shchepetnov, Arseniy A; Volotka, Andrey V; Shabaev, Vladimir M; Tupitsyn, Ilya I; Plunien, Guenter

2014-01-01

89

Spacetime Symmetries of the Quantum Hall Effect  

E-print Network

We study the symmetries of non-relativistic systems with an emphasis on applications to the fractional quantum Hall effect. A source for the energy current of a Galilean system is introduced and the non-relativistic diffeomorphism invariance studied in previous work is enhanced to a full spacetime symmetry, allowing us to derive a number of Ward identities. These symmetries are smooth in the massless limit of the lowest Landau level. We develop a formalism for Newton-Cartan geometry with torsion to write these Ward identities in a covariant form. Previous results on the connection between Hall viscosity and Hall conductivity are reproduced.

Michael Geracie; Dam Thanh Son; Chaolun Wu; Shao-Feng Wu

2014-07-04

90

Spacetime Symmetries of the Quantum Hall Effect  

E-print Network

We study the symmetries of non-relativistic systems with an emphasis on applications to the fractional quantum Hall effect. A source for the energy current of a Galilean system is introduced and the non-relativistic diffeomorphism invariance studied in previous work is enhanced to a full spacetime symmetry, allowing us to derive a number of Ward identities. These symmetries are smooth in the massless limit of the lowest Landau level. We develop a formalism for Newton-Cartan geometry with torsion to write these Ward identities in a covariant form. Previous results on the connection between Hall viscosity and Hall conductivity are reproduced.

Geracie, Michael; Wu, Chaolun; Wu, Shao-Feng

2014-01-01

91

Quantum Rotational Effects in Nanomagnetic Systems  

NASA Astrophysics Data System (ADS)

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

O'Keeffe, Michael F.

92

Magnetic quantum ratchet effect in graphene  

NASA Astrophysics Data System (ADS)

A periodically driven system with spatial asymmetry can exhibit a directed motion facilitated by thermal or quantum fluctuations. This so-called ratchet effect has fascinating ramifications in engineering and natural sciences. Graphene is nominally a symmetric system. Driven by a periodic electric field, no directed electric current should flow. However, if the graphene has lost its spatial symmetry due to its substrate or adatoms, an electronic ratchet motion can arise. We report an experimental demonstration of such an electronic ratchet in graphene layers, proving the underlying spatial asymmetry. The orbital asymmetry of the Dirac fermions is induced by an in-plane magnetic field, whereas the periodic driving comes from terahertz radiation. The resulting magnetic quantum ratchet transforms the a.c. power into a d.c. current, extracting work from the out-of-equilibrium electrons driven by undirected periodic forces. The observation of ratchet transport in this purest possible two-dimensional system indicates that the orbital effects may appear and be substantial in other two-dimensional crystals such as boron nitride, molybdenum dichalcogenides and related heterostructures. The measurable orbital effects in the presence of an in-plane magnetic field provide strong evidence for the existence of structure inversion asymmetry in graphene.

Drexler, C.; Tarasenko, S. A.; Olbrich, P.; Karch, J.; Hirmer, M.; Mller, F.; Gmitra, M.; Fabian, J.; Yakimova, R.; Lara-Avila, S.; Kubatkin, S.; Wang, M.; Vajtai, R.; Ajayan, P. M.; Kono, J.; Ganichev, S. D.

2013-02-01

93

Quantum spring from the Casimir effect  

NASA Astrophysics Data System (ADS)

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

Feng, Chao-Jun; Li, Xin-Zhou

2010-07-01

94

Non-Markovian effect on the quantum discord  

SciTech Connect

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.

Wang Bo; Xu Zhenyu [Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071 (China); Graduate School of the Chinese Academy of Sciences, Beijing 100049 (China); Chen Zeqian; Feng Mang [Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071 (China)

2010-01-15

95

Study of correlations in fractional quantum Hall effect  

Microsoft Academic Search

Bulk two-dimensional electron systems in a strong perpendicular magnetic field exhibit the fascinating phenomenon of fractional quantum Hall effect. Composite fermion theory was developed in the process of understanding the fractional quantum Hall effect and was proven to work successfully for the FQHE and even beyond. In this dissertation, we explore the effect of the strong correlation between electrons in

Chuntai Shi

2009-01-01

96

Gas powered fluid gun with recoil mitigation  

DOEpatents

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.

Grubelich, Mark C; Yonas, Gerold

2013-11-12

97

Guiding effect of quantum wells in semiconductor lasers  

SciTech Connect

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)

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

98

Quantum Hall effect in a one-dimensional dynamical system  

SciTech Connect

We construct a periodically time-dependent Hamiltonian with a phase transition in the quantum Hall universality class. One spatial dimension can be eliminated by introducing a second incommensurate driving frequency, so that we can study the quantum Hall effect in a one-dimensional (1D) system. This reduction to 1D is very efficient computationally and would make it possible to perform experiments on the 2D quantum Hall effect using cold atoms in a 1D optical lattice.

Dahlhaus, J. P.; Edge, J. M.; Beenakker, C. W. J. [Instituut-Lorentz, Universiteit Leiden, P.O. Box 9506, NL-2300 RA Leiden (Netherlands); Tworzydlo, J. [Institute of Theoretical Physics, University of Warsaw, Hoza 69, PL-00-681 Warsaw (Poland)

2011-09-15

99

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

PubMed

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

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

100

Noise Effects in Quantum Magic Squares Game  

E-print Network

In the article we analyse how noisiness of quantum channels can influence the magic squares quantum pseudo-telepathy game. We show that the probability of success can be used to determine characteristics of quantum channels. Therefore the game deserves more careful study aiming at its implementation.

P. Gawron; J. A. Miszczak; J. Sladkowski

2008-01-31

101

Fractional Quantum Hall Effect in Optical Lattices  

E-print Network

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

Mohammad Hafezi; Anders S. Sorensen; Eugene Demler; Mikhail D. Lukin

2007-06-06

102

Effective Evolution Equations in Quantum Physics  

E-print Network

In these notes, we review some recent mathematical results concerning the derivation of effective evolution equations from many body quantum mechanics. In particular, we discuss the emergence of the Hartree equation in the so-called mean field regime (for example, for systems of gravitating bosons), and we show that the Gross-Pitaevskii equation approximates the dynamics of initially trapped Bose-Einstein condensates. We explain how effective evolution equations can be derived, on the one hand, by analyzing the so called BBGKY hierarchy, describing the time-evolution of reduced density matrices, and, on the other hand, by studying the dynamics of coherent initial states in a Fock-space representation of the many body system.

Benjamin Schlein

2011-11-29

103

Anomalous nuclear quantum effects in ice  

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

104

Tunable exciton Aharonov-Bohm effect in a quantum ring  

NASA Astrophysics Data System (ADS)

We studied the optical Aharonov-Bohm effect for an exciton in a semiconductor quantum ring. A perpendicular electric field applied to a quantum ring with large height, is able to tune the exciton ground state energy such that it exhibits a weak observable Aharonov-Bohm oscillations. This Aharonov-Bohm effect is tunable in strength and period.

Li, Bin; Magnus, W.; Peeters, F. M.

2010-02-01

105

Tunable exciton Aharonov-Bohm effect in a quantum ring  

Microsoft Academic Search

We studied the optical Aharonov-Bohm effect for an exciton in a semiconductor quantum ring. A perpendicular electric field applied to a quantum ring with large height, is able to tune the exciton ground state energy such that it exhibits a weak observable Aharonov-Bohm oscillations. This Aharonov-Bohm effect is tunable in strength and period.

Bin Li; W. Magnus; F. M. Peeters

2010-01-01

106

Quantum interference effects in degenerate systems. Spontaneous and stimulated radiation  

Microsoft Academic Search

We study the effect of quantum interference on the structure and properties of spontaneous and stimulated transitions in a degenerate V-type three-level atom with an arbitrary total momentum of each state. Explicit expressions for the factors in the terms of the relaxation operator and stimulated transition operator with account of quantum interference effects are obtained. It has been demonstrated that

A. A. Panteleev; Vl. K. Roerich

2004-01-01

107

Quantum optics of a quantum dot: Local-field effects G. Ya. Slepyan* and S. A. Maksimenko  

E-print Network

Quantum optics of a quantum dot: Local-field effects G. Ya. Slepyan* and S. A. Maksimenko Institute electrodynamics of isolated quantum dot QD has been analyzed. The system is modeled as a strongly confined properties of quantum dots QDs is currently an area of active investigation owing to promis- ing potential

Nabben, Reinhard

108

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

PubMed

The quantum anomalous Hall effect has recently been observed experimentally in thin films of Cr-doped (Bi,Sb)_{2}Te_{3} at a low temperature (?30??mK). In this work, we propose realizing the quantum anomalous Hall effect in more conventional diluted magnetic semiconductors with magnetically doped InAs/GaSb type-II quantum wells. Based on a four-band model, we find an enhancement of the Curie temperature of ferromagnetism due to band edge singularities in the inverted regime of InAs/GaSb quantum wells. Below the Curie temperature, the quantum anomalous Hall effect is confirmed by the direct calculation of Hall conductance. The parameter regime for the quantum anomalous Hall phase is identified based on the eight-band Kane model. The high sample quality and strong exchange coupling make magnetically doped InAs/GaSb quantum wells good candidates for realizing the quantum anomalous Hall insulator at a high temperature. PMID:25325653

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

2014-10-01

109

Scintillation Response of Liquid Xenon to Low Energy Nuclear Recoils  

E-print Network

Liquid Xenon (LXe) is expected to be an excellent target and detector medium to search for dark matter in the form of Weakly Interacting Massive Particles (WIMPs). Knowledge of LXe ionization and scintillation response to low energy nuclear recoils expected from the scattering of WIMPs by Xe nuclei is important for determining the sensitivity of LXe direct detection experiments. Here we report on new measurements of the scintillation yield of Xe recoils with kinetic energy as low as 10 keV. The dependence of the scintillation yield on applied electric field was also measured in the range of 0 to 4 kV/cm. Results are in good agreement with recent theoretical predictions that take into account the effect of biexcitonic collisions in addition to the nuclear quenching effect.

E. Aprile; K. L. Giboni; P. Majewski; K. Ni; M. Yamashita; R. Hasty; A. Manzur; D. N. McKinsey

2005-03-29

110

Macroscopic quantum effects for classical light  

NASA Astrophysics Data System (ADS)

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

Petrov, N. I.

2014-10-01

111

Quantum Numbers of Textured Hall Effect Quasiparticles  

SciTech Connect

We propose a class of variational wave functions with slow variation in spin and charge density and simple vortex structure at infinity, which properly generalize both the Laughlin quasiparticles and baby Skyrmions. We argue, on the basis of these wave functions and a spin-statistics relation in the relevant effective field theory, that the spin of the corresponding quasiparticle has a fractional part related in a universal fashion to the properties of the bulk state. We propose a direct experimental test of this claim. We show that certain spin-singlet quantum Hall states can be understood as arising from primary polarized states by Skyrmion condensation. {copyright} {ital 1996 The American Physical Society.}

Nayak, C. [Department of Physics, Joseph Henry Laboratories, Princeton University, Princeton, New Jersey 08544 (United States)] [Department of Physics, Joseph Henry Laboratories, Princeton University, Princeton, New Jersey 08544 (United States); Wilczek, F. [School of Natural Sciences, Institute for Advanced Study, Olden Lane, Princeton, New Jersey 08540 (United States)] [School of Natural Sciences, Institute for Advanced Study, Olden Lane, Princeton, New Jersey 08540 (United States)

1996-11-01

112

The effective field theory treatment of quantum gravity  

SciTech Connect

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.

Donoghue, John F. [Department of Physics, University of Massachusetts, Amherst, MA 01003 (United States)

2012-09-24

113

On Quantum Effects in a Theory of Biological Evolution  

PubMed Central

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

Martin-Delgado, M. A.

2012-01-01

114

Imperfection effects for multiple applications of the quantum wavelet transform.  

PubMed

We study analytically and numerically the effects of various imperfections in a quantum computation of a simple dynamical model based on the quantum wavelet transform. The results for fidelity time scales, obtained for a large range of error amplitudes and number of qubits, imply that for static imperfections the threshold for fault-tolerant quantum computation is decreased by a few orders of magnitude compared to the case of random errors. PMID:12857169

Terraneo, M; Shepelyansky, D L

2003-06-27

115

Imperfection effects for multiple applications of the quantum wavelet transform  

E-print Network

We study analytically and numerically the effects of various imperfections in a quantum computation of a simple dynamical model based on the Quantum Wavelet Transform (QWT). The results for fidelity timescales, obtained for a large range of error amplitudes and number of qubits, imply that for static imperfections the threshold for fault-tolerant quantum computation is decreased by a few orders of magnitude compared to the case of random errors.

Marcello Terraneo; Dima L. Shepelyansky

2003-03-09

116

Effective fault-tolerant quantum computation with slow measurements  

E-print Network

How important is fast measurement for fault-tolerant quantum computation? Using a combination of existing and new ideas, we argue that measurement times as long as even 1,000 gate times or more have a very minimal effect on the quantum accuracy threshold. This shows that slow measurement, which appears to be unavoidable in many implementations of quantum computing, poses no essential obstacle to scalability.

David P. DiVincenzo; Panos Aliferis

2006-07-06

117

Discrimination of nuclear recoils from alpha particles with superheated liquids  

NASA Astrophysics Data System (ADS)

The PICASSO collaboration observed for the first time a significant difference between the acoustic signals induced by neutrons and alpha particles in a detector based on superheated liquids. This new discovery offers the possibility of improved background suppression and could be especially useful for dark matter experiments. This new effect may be attributed to the formation of multiple bubbles on alpha tracks, compared to single nucleations created by neutron-induced recoils.

Aubin, F.; Auger, M.; Genest, M.-H.; Giroux, G.; Gornea, R.; Faust, R.; Leroy, C.; Lessard, L.; Martin, J.-P.; Morlat, T.; Piro, M.-C.; Starinski, N.; Zacek, V.; Beltran, B.; Krauss, C. B.; Behnke, E.; Levine, I.; Shepherd, T.; Nadeau, P.; Wichoski, U.; Pospisil, S.; Stekl, I.; Sodomka, J.; Clark, K.; Dai, X.; Davour, A.; Levy, C.; Noble, A. J.; Storey, C.

2008-10-01

118

Room-Temperature Quantum Hall Effect in Graphene  

NASA Astrophysics Data System (ADS)

The quantum Hall effect (QHE), one example of a quantum phenomenon that occurs on a truly macroscopic scale, has attracted intense interest since its discovery in 1980 and has helped elucidate many important aspects of quantum physics. It has also led to the establishment of a new metrological standard, the resistance quantum. Disappointingly, however, the QHE has been observed only at liquid-helium temperatures. We show that in graphene, in a single atomic layer of carbon, the QHE can reliably be measured even at room temperature, which makes possible QHE resistance standards becoming available to a broader community, outside a few national institutions.

Novoselov, K. S.; Jiang, Z.; Zhang, Y.; Morozov, S. V.; Stormer, H. L.; Zeitler, U.; Maan, J. C.; Boebinger, G. S.; Kim, , P.; Geim, A. K.

2007-03-01

119

Searching for WIMP Recoils in Ancient Mica  

NASA Astrophysics Data System (ADS)

We are exploring the possibility of using mica to set limits on weakly interacting massive particles (WIMPs). Mica is a solid state nuclear track detector capable of recording the keV/amu recoil atoms produced in WIMP-nucleus collisions. One way to apply this idea is to look for fossil tracks in mica as old as 1 billion years. The mica is used as a detector and as a target. To carry out this experiment we select mica which is very old and found very deep underground (to reduce background from muon induced recoils). Then we choose a target atom within the mica, typically Iron or heavier. Given the flux of WIMPs, their interaction cross section with the target nucleus, and a WIMP mass we can calculate the number of recoils produced inside the mica during its lifetime. The damage caused by the recoil is stored and can be revealed by placing the mica in a suitable etchant. The WIMP-recoil etch pits must be separated from a background of etch pits caused by the recoiling daughters of Uranium and Thorium after alpha decay which produce etch pits of comparable size. We believe this is possible using an atomic force microscope to measure the etch pit depths. By limiting the amount of WIMP-recoils we observe we can set limits on the WIMP masses and interaction cross sections. For reasonable values for the age of mica and target concentrations we can hope to set limits which are several orders of magnitude better than current limits. The status of this search will be reported.

Snowden-Ifft, D. P.; Price, P. B.

1993-05-01

120

Anatomy of the Binary Black Hole Recoil: A Multipolar Analysis  

NASA Technical Reports Server (NTRS)

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.

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

2007-01-01

121

Anatomy of the binary black hole recoil: A multipolar analysis  

E-print Network

We present a multipolar analysis of the gravitational recoil computed in recent numerical simulations of binary black hole (BH) coalescence, for both unequal masses and non-zero, non-precessing spins. We show that multipole moments up to and including l=4 are sufficient to accurately reproduce the final recoil velocity (within ~2%) and that only a few dominant modes contribute significantly to it (within ~5%). We describe how the relative amplitudes, and more importantly, the relative phases, of these few modes control the way in which the recoil builds up throughout the inspiral, merger, and ringdown phases. We also find that the numerical results can be reproduced by an ``effective Newtonian'' formula for the multipole moments obtained by replacing the radial separation in the Newtonian formulae 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 (QNMs). 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 help explain the remarkable difference between the amplitudes of planar and non-planar kicks for equal-mass spinning black holes.

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

2007-07-02

122

Recoiling from a Kick in the Head-On Case  

NASA Technical Reports Server (NTRS)

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.

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

2007-01-01

123

Recoil-ion and electron momentum spectroscopy: reaction-microscopes  

NASA Astrophysics Data System (ADS)

Recoil-ion and electron momentum spectroscopy is a rapidly developing technique that allows one to measure the vector momenta of several ions and electrons resulting from atomic or molecular fragmentation. In a unique combination, large solid angles close to 4pi and superior momentum resolutions around a few per cent of an atomic unit (a.u.) are typically reached in state-of-the art machines, so-called reaction-microscopes. Evolving from recoil-ion and cold target recoil-ion momentum spectroscopy (COLTRIMS), reaction-microscopesthe `bubble chambers of atomic physics'mark the decisive step forward to investigate many-particle quantum-dynamics occurring when atomic and molecular systems or even surfaces and solids are exposed to time-dependent external electromagnetic fields. This paper concentrates on just these latest technical developments and on at least four new classes of fragmentation experiments that have emerged within about the last five years. First, multi-dimensional images in momentum space brought unprecedented information on the dynamics of single-photon induced fragmentation of fixed-in-space molecules and on their structure. Second, a break-through in the investigation of high-intensity short-pulse laser induced fragmentation of atoms and molecules has been achieved by using reaction-microscopes. Third, for electron and ion-impact, the investigation of two-electron reactions has matured to a state such that the first fully differential cross sections (FDCSs) are reported. Fourth, comprehensive sets of FDCSs for single ionization of atoms by ion-impact, the most basic atomic fragmentation reaction, brought new insight, a couple of surprises and unexpected challenges to theory at keV to GeV collision energies. In addition, a brief summary on the kinematics is provided at the beginning. Finally, the rich future potential of the method is briefly envisaged.

Ullrich, J.; Moshammer, R.; Dorn, A.; Drner, R.; Schmidt, L. Ph H.; Schmidt-Bcking, H.

2003-09-01

124

Memory effects in quantum channel discrimination  

E-print Network

We consider quantum-memory assisted protocols for discriminating quantum channels. We show that for optimal discrimination of memory channels, memory assisted protocols are needed. This leads to a new notion of distance for channels with memory. For optimal discrimination and estimation of sets of unitary channels memory-assisted protocols are not required.

Giulio Chiribella; Giacomo M. D'Ariano; Paolo Perinotti

2008-03-21

125

Quantum radiation by electrons in lasers and the Unruh effect  

E-print Network

In addition to the Larmor radiation known from classical electrodynamics, electrons in a laser field may emit pairs of entangled photons -- which is a pure quantum effect. We investigate this quantum effect and discuss why it is suppressed in comparison with the classical Larmor radiation (which is just Thomson backscattering of the laser photons). Further, we provide an intuitive explanation of this process (in a simplified setting) in terms of the Unruh effect.

Ralf Schtzhold; Clovis Maia

2010-04-14

126

Quantum-Memory Effects in the Emission of Quantum-Dot Microcavities  

NASA Astrophysics Data System (ADS)

The experimentally measured input-output characteristics of optically pumped semiconductor microcavities exhibits unexpected oscillations modifying the fundamentally linear slope in the excitation power regime below lasing. A systematic microscopic analysis reproduces these oscillations, identifying them as a genuine quantum-memory effect, i.e., a photon-density correlation accumulated during the excitation. With the use of projected quantum measurements, it is shown that the input-output oscillations can be controlled and enhanced by an order of magnitude when the quantum fluctuations of the pump are adjusted.

Berger, C.; Huttner, U.; Mootz, M.; Kira, M.; Koch, S. W.; Tempel, J.-S.; Amann, M.; Bayer, M.; Mintairov, A. M.; Merz, J. L.

2014-08-01

127

Effects of alpha, gamma, and alpha-recoil radiation on borosilicate glass containing Savannah River Plant defense high-level nuclear waste. [Lead ions-250 keV; xenon ions-160 keV  

SciTech Connect

At the Savannah River Plant, the reference process for the immobilization of defense high-level waste (DHLW) for geologic storage is vitrification into borosilicate glass. During geologic storage for 10/sup 6/ y, the glass would be exposed to approx. 3 x 10/sup 10/ rad of ..beta.. radiation, approx. 10/sup 10/ rad of ..gamma.. radiation, and 10/sup 18/ particles/g glass for both ..cap alpha.. and ..cap alpha..-recoil radiation. This paper discusses tests of the effect of these radiations on the leachability and density of the glass. Even though the doses were large, no effect of the radiations was detected that reduced the effectiveness of the glass for long-term storage of DHLW even at doses corresponding to 10/sup 6/ years storage for the actual glass. For the tests, glass containing simulated DHLW was prepared from frit of the reference composition. Three methods were used to irradiate the glass: external irradiations with beams of approx. 200 keV Xe or Pb ions, internal irradiations with Cm-244 doped glass, and external irradiations with Co-60 ..gamma.. rays. Results with both Xe and Pb ions indicate that a dose of 3 x 10/sup 13/ ions/cm/sup 2/ (simulating > 10/sup 6/ years storage) does not significantly increase the leachability of the glass in deionized water. Tests with Cm-244 doped glass show no increase in leach rate in water or brine up to a dose of 10/sup 18/ ..cap alpha.. and ..cap alpha..-recoils/g glass. Results of larger doses are being examined. The density of the Cm-244 doped glass has decreased by 1% at a dose of 10/sup 18/ particles/g glass. With ..gamma..-radiation, the density has changed by < 0.05% at a dose of 8.5 x 10/sup 10/ rad. Results of leach tests in deionized water and brine indicated that this very large dose of ..gamma..-radiation increased the leach rate by only 20%. Also, the leach rates are lower in brine.

Bibler, N.E.

1981-01-01

128

Imaging transport resonances in the quantum Hall effect  

E-print Network

We image charge transport in the quantum Hall effect using a scanning charge accumulation microscope. Applying a DC bias voltage to the tip induces a highly resistive ring-shaped incompressible strip (IS) in a very high ...

Steele, Gary Alexander

2006-01-01

129

Two quantum effects in the theory of gravitation  

E-print Network

We will discuss two methods by which the formalism of quantum field theory can be included in calculating the physical effects of gravitation. In the first of these, the consequences of treating general relativity as an ...

Robinson, Sean Patrick, 1977-

2005-01-01

130

Fractional quantum Hall effect in the absence of Landau levels.  

PubMed

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. PMID:21750543

Sheng, D N; Gu, Zheng-Cheng; Sun, Kai; Sheng, L

2011-01-01

131

Quantum Computing Using Single Photons and the Zeno Effect  

E-print Network

We show that the quantum Zeno effect can be used to suppress the failure events that would otherwise occur in a linear optics approach to quantum computing. From a practical viewpoint, that would allow the implementation of deterministic logic gates without the need for ancilla photons or high-efficiency detectors. We also show that the photons can behave as if they were fermions instead of bosons in the presence of a strong Zeno effect, which leads to a new paradigm for quantum computation.

J. D. Franson; B. C. Jacobs; T. B. Pittman

2004-08-14

132

The quantum confined Stark effect in silicon nanocrystals.  

PubMed

The quantum confined Stark effect (QCSE) in Si nanocrystals embedded in a SiO(2) matrix is demonstrated by photoluminescence (PL) spectroscopy at room and cryogenic temperatures. It is shown that the PL peak position shifts to higher wavelengths with increasing applied electric field, which is expected from carrier polarization within the quantum dots. It is observed that the effect is more pronounced at lower temperatures due to the improved carrier localization at the lowest energy states of the quantum dots. Experimental results are shown to be in good agreement with phenomenological model developed for the QCSE model. PMID:21832777

Kulakci, Mustafa; Serincan, Ugur; Turan, Rasit; Finstad, Terje G

2008-11-12

133

Light Propagation on Quantum Curved Spacetime and Back reaction effects  

E-print Network

We study the electromagnetic field equations on an arbitrary quantum curved background in the semiclassical approximation of Loop Quantum Gravity. The effective interaction hamiltonian for the Maxwell and gravitational fields is obtained and the corresponding field equations, which can be expressed as a modified wave equation for the Maxwell potential, are derived. We use these results to analyze electromagnetic wave propagation on a quantum Robertson-Walker space time and show that Lorentz Invariance is not preserved. The formalism developed can be applied to the case where back reaction effects on the metric due to the electromagnetic field are taken into account, leading to non covariant field equations.

Carlos Kozameh; Florencia Parisi

2007-04-25

134

Optical evidence for AharonovBohm effect in quantum tubes  

Microsoft Academic Search

We present an optical evidence for AharonovBohm (AB) effect in InAs quantum tubes fabricated by a selective area-metal organic vapor phase epitaxy. The oscillations of the photoluminescence peak energies are observed in quantum tubes depending on the magnetic flux through the tube. These oscillations in energies are shown to be due to the AB effect of a charged exciton in

S. Nomura; K. Tsumura; P. Mohan; J. Motohisa; T. Fukui

2008-01-01

135

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

SciTech Connect

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

Lee, Gyeong Won [Department of Applied Physics, Hanyang University, Ansan, Kyunggi-Do 426-791 (Korea, Republic of)] [Department of Applied Physics, Hanyang University, Ansan, Kyunggi-Do 426-791 (Korea, Republic of); Jung, Young-Dae [Department of Applied Physics, Hanyang University, Ansan, Kyunggi-Do 426-791 (Korea, Republic of) [Department of Applied Physics, Hanyang University, Ansan, Kyunggi-Do 426-791 (Korea, Republic of); Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, 110 Eighth Street, Troy, New York 12180-3590 (United States)

2013-06-15

136

Manual of BlackMax, a black-hole event generator with rotation, recoil, split branes, and brane tension  

E-print Network

This is the users manual of the black-hole event generator BlackMax, which simulates the experimental signatures of microscopic and Planckian black-hole production and evolution at proton-proton, proton-antiproton and electron-positron colliders 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. It includes all of the black-hole gray-body factors known to date and incorporates the effects of black-hole rotation, splitting between the fermions, non-zero brane tension and black-hole recoil due to Hawking radiation (although not all simultaneously).

De-Chang Dai; Cigdem Issever; Eram Rizvi; Glenn Starkman; Dejan Stojkovic; Jeff Tseng

2009-02-20

137

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

E-print Network

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 graybody factors known to date and incorporates the effects of black-hole rotation, splitting between the fermions, non-zero brane tension and black-hole recoil due to Hawking radiation (although not all simultaneously). The generator can be interfaced with Herwig and Pythia.

Dai, De-Chang; Stojkovic, Dejan; Issever, Cigdem; Rizvi, Eram; Tseng, Jeff

2007-01-01

138

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

E-print Network

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 graybody factors known to date and incorporates the effects of black-hole rotation, splitting between the fermions, non-zero brane tension and black-hole recoil due to Hawking radiation (although not all simultaneously). The generator can be interfaced with Herwig and Pythia.

De-Chang Dai; Glenn Starkman; Dejan Stojkovic; Cigdem Issever; Eram Rizvi; Jeff Tseng

2007-11-19

139

Manual of BlackMax, a black-hole event generator with rotation, recoil, split branes, and brane tension  

E-print Network

This is the users manual of the black-hole event generator BlackMax, which simulates the experimental signatures of microscopic and Planckian black-hole production and evolution at proton-proton, proton-antiproton and electron-positron colliders 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. It includes all of the black-hole gray-body factors known to date and incorporates the effects of black-hole rotation, splitting between the fermions, non-zero brane tension and black-hole recoil due to Hawking radiation (although not all simultaneously).

Dai, De-Chang; Rizvi, Eram; Starkman, Glenn; Stojkovic, Dejan; Tseng, Jeff

2009-01-01

140

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

NASA Astrophysics Data System (ADS)

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/~issever/BlackMax/blackmax.html.

Dai, De-Chang; Starkman, Glenn; Stojkovic, Dejan; Issever, Cigdem; Rizvi, Eram; Tseng, Jeff

2008-04-01

141

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

SciTech Connect

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.

Dai Dechang; Starkman, Glenn [Case Western Reserve University, Cleveland, Ohio 44106-7079 (United States); Stojkovic, Dejan [Department of Physics, SUNY at Buffalo, Buffalo, New York 14260-1500 (United States); Issever, Cigdem; Tseng, Jeff [University of Oxford, Oxford (United Kingdom); Rizvi, Eram [Queen Mary, University of London, London (United Kingdom)

2008-04-01

142

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

SciTech Connect

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.

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

2010-03-19

143

Common physical mechanism for integer and fractional quantum Hall effects  

E-print Network

Integer and fractional quantum Hall effects were studied with different physics models and explained by different physical mechanisms. In this paper, the common physical mechanism for integer and fractional quantum Hall effects is studied, where a new unified formulation of integer and fractional quantum Hall effect is presented. Firstly, we introduce a 2-dimensional ideal electron gas model in the presence of strong magnetic field with symmetry gauge, and the transverse electric filed $\\varepsilon_2$ is also introduced to balance Lorentz force. Secondly, the Pauli equation is solved where the wave function and energy levels is given explicitly. Thirdly, after the calculation of the degeneracy density for 2-dimensional ideal electron gas system, the Hall resistance of the system is obtained, where the quantum Hall number $\

Jianhua wang; Kang Li; Shuming Long; Yi Yuan

2011-07-05

144

Local lattice damage at recoil atoms of heavy ion reactions  

Microsoft Academic Search

The radiation damage density in the microscopic vicinity of recoil implanted ions was measured at different implantation energies. The results demonstrate its independence from the recoil energy in the region of nuclear stopping above 10 keV.

M. Menningen; H. Haas; H. H. Bertschat; R. Butt; H. Grawe; R. Keitel; R. Sielemann; W.-D. Zeitz

1980-01-01

145

Quantum Boundary Effect in Nanomaterials: Undo the Quantum Size Effect by Surface Passivation of Silicon Nanofilms  

NASA Astrophysics Data System (ADS)

It is well known that when the size of a semiconductor is reduced, its band gap will increase due to the increased kinetic energy of the electrons and holes. However, first-principles calculations reveal that there should also be a quantum boundary effect (QBE), which can drastically change the band gap to the extent that the quantum size effect (QSE) is completely erased. It is found that, for Si(001) nanofilms, surface passivations could show such a strong QBE. While the films are passivated by hydrogen, they show a clear QSE with significant increase in band gap. When some of the hydrogen atoms are replaced by =NH ligands, however, the band gap recovers to that of bulk silicon even for film size as small as two nanometers. The concept of zero confinement state for semiconductors will be introduced. It elucidates why it is possible to remove the seemingly universal QSE. The finding here could be highly desirable for certain applications of nanostructured semiconductors where gap increasing due to QSE is detrimental.

Sun, Yiyang; Liu, Xin; Zhang, Shengbai

2011-03-01

146

Microscopic theory of quantum dot interactions with quantum light: local field effect G.Ya. Slepyan, A. Magyarov,  

E-print Network

Microscopic theory of quantum dot interactions with quantum light: local field effect G.Ya. Slepyan response of a single QD exposed to quantum light, accounting the depolarization induced local­field has qubit, coherent fields, vacuum state of electromagnetic field and light with arbitrary photonic state

Nabben, Reinhard

147

Franz-Keldysh effect in ZnO quantum wire  

NASA Astrophysics Data System (ADS)

Within the framework of the effective mass, the electric field effect on the optical absorption coefficient is investigated theoretically in cylindrical ZnO quantum wire (QWR). Numerical results show that the application of the electric field can decrease the strength and the threshold energy of the optical absorption coefficient in ZnO QWR. We find that there are additional oscillations in the absorption above the effective band gap, which are due to the Franz-Keldysh effect for the electric field parallel to the axis of the wire. In addition, quantum size effects on the optical absorption of ZnO QWR are also calculated.

Xia, Congxin; Wei, Shuyi; Spector, Harold N.

2010-06-01

148

Proton recoil proportional counter measurements in FTR  

Microsoft Academic Search

Neutron spectral measurements provide a cross check for passive dosimetry measurements. The emphasis is that the data provide a measure of the quality of unfolded passive sensor data at this location. This permits higher confidence in the uncertainty estimates for data obtained at locations where active measurements cannot be made, but passive measurements can. Proton recoil counters have been used

W. R. Sloan; R. S. McBeath; E. F. Bennett; T. J. Yule

1981-01-01

149

Proton recoil scintillator neutron rem meter  

DOEpatents

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.

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

2003-01-01

150

Quantum effects improve the energy efficiency of feedback control  

NASA Astrophysics Data System (ADS)

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.

Horowitz, Jordan M.; Jacobs, Kurt

2014-04-01

151

Quantum effects improve the energy efficiency of feedback control.  

PubMed

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

Horowitz, Jordan M; Jacobs, Kurt

2014-04-01

152

Non-adiabatic molecular dynamics with quantum solvent effects Oleg V. Prezhdo*, Craig Brooksby  

E-print Network

Non-adiabatic molecular dynamics with quantum solvent effects Oleg V. Prezhdo*, Craig Brooksby) molecular dynamics (MD) to include quantum effects of solvent environments are described. In a standard NA-MD to incorporate the following quantum effects of the solvent. (1) Branching, i.e. the ability of solvent quantum

153

Effective Hamiltonian for the hybrid double quantum dot qubit  

NASA Astrophysics Data System (ADS)

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.

Ferraro, E.; De Michielis, M.; Mazzeo, G.; Fanciulli, M.; Prati, E.

2014-05-01

154

Synergetics in multiple exciton generation effect in quantum dots  

NASA Astrophysics Data System (ADS)

We present detailed analysis of the non-Poissonian population of excitons produced by multiple exciton generation (MEG) effect in quantum dots on the base of statistic theory of MEG and synergetic approach for chemical reactions. From the analysis we can conclude that a non-Poissonian distribution of exciton population is evidence of nonlinear and nonequilibrium character of the process of multiple generation of excitons in quantum dots at a single photon absorption.

Turaeva, N. N.; Oksengendler, B. L.; Uralov, I.

2011-06-01

155

Zero field Quantum Hall Effect in QED3  

NASA Astrophysics Data System (ADS)

We study analytic structure of the fermion propagator in the Quantum Electrodynamics in 2+1 dimensions (QED3) in the Landau gauge, both in perturbation theory and nonperturbatively, by solving the corresponding Schwinger-Dyson equation in rainbow approximation. In the chiral limit, we found many nodal solutions, which could be interpreted as vacuum excitations. Armed with these solutions, we use the Kubo formula and calculate the filling factor for the zero field Quantum Hall Effect.

Raya, K.; Snchez-Madrigal, S.; Raya, A.

2013-11-01

156

Quantum Electrodynamics Effects in Heavy Ions and Atoms  

SciTech Connect

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.

Shabaev, V. M.; Andreev, O. V.; Bondarev, A. I.; Glazov, D. A.; Kozhedub, Y. S.; Maiorova, A. V.; Tupitsyn, I. I. [Department of Physics, St. Petersburg State University, Ulianovskaya 1, Petrodvorets, 198504 St. Petersburg (Russian Federation); Plunien, G. [Institut fuer Theoretische Physik, TU Dresden, Mommsenstrasse 13, D-01062 Dresden (Germany); Volotka, A. V. [Department of Physics, St. Petersburg State University, Ulianovskaya 1, Petrodvorets, 198504 St. Petersburg (Russian Federation); Institut fuer Theoretische Physik, TU Dresden, Mommsenstrasse 13, D-01062 Dresden (Germany)

2011-05-11

157

Spacetime effects on satellite-based quantum communications  

NASA Astrophysics Data System (ADS)

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.

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

2014-08-01

158

Ionization and scintillation of nuclear recoils in gaseous xenon  

E-print Network

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

Renner, J; Goldschmidt, A; Matis, H S; Miller, T; Nakajima, Y; Nygren, D; Oliveira, C A B; Shuman, D; lvarez, V; Borges, F I G; Crcel, S; Castel, J; Cebrin, S; Cervera, A; Conde, C A N; Dafni, T; Dias, T H V T; Daz, J; Esteve, R; Evtoukhovitch, P; Fernandes, L M P; Ferrario, P; Ferreira, A L; Freitas, E D C; Gil, A; Gmez, H; Gmez-Cadenas, J J; Gonzlez-Daz, D; Gutirrez, R M; Hauptman, J; Morata, J A Hernando; Herrera, D C; Iguaz, F J; Irastorza, I G; Jinete, M A; Labarga, L; Laing, A; Liubarsky, I; Lopes, J A M; Lorca, D; Losada, M; Luzn, G; Mar, A; Martn-Albo, J; Martnez, A; Moiseenko, A; Monrabal, F; Monserrate, M; Monteiro, C M B; Mora, F J; Moutinho, L M; Vidal, J Muoz; da Luz, H Natal; Navarro, G; Nebot-Guinot, M; Palma, R; Prez, J; Aparicio, J L Prez; Ripoll, L; Rodrguez, A; Rodrguez, J; Santos, F P; Santos, J M F dos; Segu, L; Serra, L; Simn, A; Sofka, C; Sorel, M; Toledo, J F; Toms, A; Torrent, J; Tsamalaidze, Z; Veloso, J F C A; Villar, J A; Webb, R C; White, J; Yahlali, N

2014-01-01

159

Ionization and scintillation of nuclear recoils in gaseous xenon  

E-print Network

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

J. Renner; V. M. Gehman; A. Goldschmidt; H. S. Matis; T. Miller; Y. Nakajima; D. Nygren; C. A. B. Oliveira; D. Shuman; V. lvarez; F. I. G. Borges; S. Crcel; J. Castel; S. Cebrin; A. Cervera; C. A. N. Conde; T. Dafni; T. H. V. T. Dias; J. Daz; R. Esteve; P. Evtoukhovitch; L. M. P. Fernandes; P. Ferrario; A. L. Ferreira; E. D. C. Freitas; A. Gil; H. Gmez; J. J. Gmez-Cadenas; D. Gonzlez-Daz; R. M. Gutirrez; J. Hauptman; J. A. Hernando Morata; D. C. Herrera; F. J. Iguaz; I. G. Irastorza; M. A. Jinete; L. Labarga; A. Laing; I. Liubarsky; J. A. M. Lopes; D. Lorca; M. Losada; G. Luzn; A. Mar; J. Martn-Albo; A. Martnez; A. Moiseenko; F. Monrabal; M. Monserrate; C. M. B. Monteiro; F. J. Mora; L. M. Moutinho; J. Muoz Vidal; H. Natal da Luz; G. Navarro; M. Nebot-Guinot; R. Palma; J. Prez; J. L. Prez Aparicio; L. Ripoll; A. Rodrguez; J. Rodrguez; F. P. Santos; J. M. F. dos Santos; L. Segu; L. Serra; A. Simn; C. Sofka; M. Sorel; J. F. Toledo; A. Toms; J. Torrent; Z. Tsamalaidze; J. F. C. A. Veloso; J. A. Villar; R. C. Webb; J. White; N. Yahlali

2014-09-09

160

A curved detection-slit to improve ERD (Elastic Recoil Detection) energy/depth resolution  

SciTech Connect

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.

Brice, D.K.; Doyle, B.L.

1989-01-01

161

Projectile focusing near the recoil-ion threshold  

NASA Astrophysics Data System (ADS)

The post-collisional interactions in ion-atom ionization collisions are studied around the electron capture to the continuum (ECC) process. For this purpose, a suitable double differential cross section is introduced, involving the longitudinal recoil-ion momentum and the projectile transverse momentum transfer. Using the fact that the ECC process is closely related to the threshold in the longitudinal momentum distribution, we study this distribution as a function of the projectile scattering angle. Using the CDW-EIS approximation we theoretically find a focusing (defocusing) effect as we get closer to the distribution threshold for proton (antiproton) impact on He atoms.

Rodrguez, V. D.; Macri, P. A.; Barrachina, R. O.

2007-03-01

162

Effective Physical Processes and Active Information in Quantum Computing  

E-print Network

The recent debate on hypercomputation has arisen new questions both on the computational abilities of quantum systems and the Church-Turing Thesis role in Physics. We propose here the idea of "effective physical process" as the essentially physical notion of computation. By using the Bohm and Hiley active information concept we analyze the differences between the standard form (quantum gates) and the non-standard one (adiabatic and morphogenetic) of Quantum Computing, and we point out how its Super-Turing potentialities derive from an incomputable information source in accordance with Bell's constraints. On condition that we give up the formal concept of "universality", the possibility to realize quantum oracles is reachable. In this way computation is led back to the logic of physical world.

Ignazio Licata

2007-05-08

163

Quantum dissipative Brownian motion and the Casimir effect.  

PubMed

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

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

2009-10-01

164

Atomic Quantum Zeno Effect for Ensembles and Single Systems  

E-print Network

The so-called quantum Zeno effect is essentially a consequence of the projection postulate for ideal measurements. To test the effect Itano et al. have performed an experiment on an ensemble of atoms where rapidly repeated level measurements were realized by means of short laser pulses. Using dynamical considerations we give an explanation why the projection postulate can be applied in good approximation to such measurements. Corrections to ideal measurements are determined explicitly. This is used to discuss in how far the experiment of Itano et al. can be considered as a test of the quantum Zeno effect. We also analyze a new possible experiment on a single atom where stochastic light and dark periods can be interpreted as manifestation of the quantum Zeno effect. We show that the measurement point of view gives a quick and intuitive understanding of experiments of the above type, although a finer analysis has to take the corrections into account.

Almut Beige; Gerhard C. Hegerfeldt; Dirk G. Sondermann

1996-10-02

165

A quantitative account of quantum effects in liquid water  

SciTech Connect

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

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

2006-10-14

166

High-Efficiency Quantum Interrogation Measurements via the Quantum Zeno Effect  

SciTech Connect

The phenomenon of quantum interrogation allows one to optically detect the presence of an absorbing object, without the measuring light interacting with it. In an application of the quantum Zeno effect, the object inhibits the otherwise coherent evolution of the light, such that the probability that an interrogating photon is absorbed can in principle be arbitrarily small. We have implemented this technique, achieving efficiencies of up to 73% , and consequently exceeding the 50% theoretical maximum of the original ''interaction-free'' measurement proposal. We have also predicted and experimentally verified a previously unsuspected dependence on loss. (c) 1999 The American Physical Society.

Kwiat, P. G. [Physics Division, P-23, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)] [Physics Division, P-23, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); White, A. G. [Physics Division, P-23, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)] [Physics Division, P-23, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Mitchell, J. R. [Physics Division, P-23, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)] [Physics Division, P-23, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Nairz, O. [Institute for Experimental Physics, University of Innsbruck, Innsbruck 6020, (Austria)] [Institute for Experimental Physics, University of Innsbruck, Innsbruck 6020, (Austria); Weihs, G. [Institute for Experimental Physics, University of Innsbruck, Innsbruck 6020, (Austria)] [Institute for Experimental Physics, University of Innsbruck, Innsbruck 6020, (Austria); Weinfurter, H. [Institute for Experimental Physics, University of Innsbruck, Innsbruck 6020, (Austria)] [Institute for Experimental Physics, University of Innsbruck, Innsbruck 6020, (Austria); Zeilinger, A. [Institute for Experimental Physics, University of Innsbruck, Innsbruck 6020, (Austria)] [Institute for Experimental Physics, University of Innsbruck, Innsbruck 6020, (Austria)

1999-12-06

167

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

SciTech Connect

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

Fu Xiaoqi [Department of Chemistry, City College of New York, New York, N.Y. 10031 (United States); Key Laboratory for Soft Chemistry and Functional Materials of Ministry Education, Nanjing University of Science and Technology, Nanjing 210094 (China); School of Chemistry and Chemical Engineering, Jiangsu University, Zhenjiang 212013 (China); Pan Yi; Lombardi, John R. [Department of Chemistry, City College of New York, New York, N.Y. 10031 (United States); Wang Xin [Key Laboratory for Soft Chemistry and Functional Materials of Ministry Education, Nanjing University of Science and Technology, Nanjing 210094 (China)

2011-01-14

168

Quantum trajectory method for the quantum Zeno and anti-Zeno effects  

SciTech Connect

We perform stochastic simulations of the quantum Zeno and anti-Zeno effects for a two-level system and for a decaying one. Instead of a simple projection postulate approach, a more realistic model of a detector interacting with the environment is used. The influence of the environment is taken into account using the quantum trajectory method. Simulation of the measurement for a single system exhibits probabilistic behavior showing the collapse of the wave packet. When a large ensemble is analyzed using the quantum trajectory method, the results are the same as those produced using the density matrix method. The results of numerical calculations are compared with the analytical expressions for the decay rate of the measured system, and good agreement is found. Since the analytical expressions depend on the duration of the measurement only, the agreement with the numerical calculations shows that other parameters of the model are not important.

Ruseckas, J.; Kaulakys, B. [Institute of Theoretical Physics and Astronomy of Vilnius University, A. Gostauto 12, LT-01108 Vilnius (Lithuania)

2006-05-15

169

``Interaction--free'' interaction: entangling evolution via quantum Zeno effect  

E-print Network

The effect of entangling evolution induced by frequently repeated quantum measurement is presented. The interesting possibility of conditional freezing the system in maximally entangled state out of Zeno effect regime is also revealed. The illustration of the phenomena in terms of dynamical version of ``interaction free'' measurement is presented. Some general conclusions are provided.

Pawe? Horodecki

1998-07-11

170

Physics and application of the quantum Hall effect  

Microsoft Academic Search

The High Magnetic Field Laboratory in Grenoble is the birthplace of the quantum Hall effect (QHE). In the morning of the 5th of February 1980 during a magnetotransport experiment on silicon field-effect transistors the idea came up to measure deviations of the Hall resistance relative to a quantized value which can be calculated on the basis of a

Klaus v. Klitzing

1995-01-01

171

Quantum effective field theory of strongly correlated electron systems  

Microsoft Academic Search

A new theory, namely quantum effective-field theory of Fermion systems is proposed and it is applied to the Hubbard model for studying phase transitions. The key idea is to introduce an apparently gauge-breaking effective field and to apply it to the boundary of a cluster. This makes possible the exchange or transfer of electrons or holes between the inside and

Masuo Suzuki

1995-01-01

172

Quantum origin of an anomalous isotope effect in ozone formation  

E-print Network

Quantum origin of an anomalous isotope effect in ozone formation D. Babikov *, B.K. Kendrick, R mechanical calculations of the ðJ ¼ 0? energies and lifetimes of the metastable states of ozone on a new effect in the reaction that forms ozone because of their role in the energy transfer mechanism, in which

Reid, Scott A.

173

Quantum vacuum effects from boundaries of designer potentials  

SciTech Connect

Vacuum energy in quantum field theory, being the sum of zero-point energies of all field modes, is formally infinite but yet, after regularization or renormalization, can give rise to finite observable effects. One way of understanding how these effects arise is to compute the vacuum energy in an idealized system such as a large cavity divided into disjoint regions by pistons. In this paper, this type of calculation is carried out for situations where the potential affecting a field is not the same in all regions of the cavity. It is shown that the observable parts of the vacuum energy in such potentials do not fall off to zero as the region where the potential is nontrivial becomes large. This unusual behavior might be interesting for tests involving quantum vacuum effects and for studies on the relation between vacuum energy in quantum field theory and geometry.

Konopka, Tomasz [ITP, Utrecht University, Utrecht 3584 CE (Netherlands)

2009-04-15

174

Quantum vacuum effects from boundaries of designer potentials  

E-print Network

Vacuum energy in quantum field theory, being the sum of zero-point energies of all field modes, is formally infinite but yet, after regularization or renormalization, can give rise to finite observable effects. One way of understanding how these effects arise is to compute the vacuum energy in an idealized system such as a large cavity divided into disjoint regions by pistons. In this paper, this type of calculation is carried out for situations where the potential affecting a field is not the same in all regions of the cavity. It is shown that the observable parts of the vacuum energy in such potentials do not fall off to zero as the region where the potential is nontrivial becomes large. This unusual behavior might be interesting for tests involving quantum vacuum effects and for studies on the relation between vacuum energy in quantum field theory and geometry.

Tomasz Konopka

2009-04-03

175

Quantum  

Microsoft Academic Search

All unitary representations of the quantum ``az+b'' group are found. It turns out that this quantum group is self dual i.e. all unitary representations are 'numbered' by elements of the same group. Moreover, the formula for all unitary representations involving the quantum exponential function is proven.

Malgorzata Rowicka

2001-01-01

176

Quantum \\  

Microsoft Academic Search

All unitary representations of the quantum ``az+b'' group are found. It turns\\u000aout that this quantum group is self dual i.e. all unitary representations are\\u000a'numbered' by elements of the same group. Moreover, the formula for all unitary\\u000arepresentations involving the quantum exponential function is proven.

Malgorzata Rowicka

2001-01-01

177

Focus on quantum effects and noise in biomolecules  

NASA Astrophysics Data System (ADS)

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 ) and timescales (sub picosecond) in noisy biological systems can uncover novel phenomena and concepts and hence present a fertile ground for truly multidisciplinary research.

Fleming, G. R.; Huelga, S. F.; Plenio, M. B.

2011-11-01

178

Dynamical quantum Hall effect in the parameter space  

PubMed Central

Geometric phases in quantum mechanics play an extraordinary role in broadening our understanding of fundamental significance of geometry in nature. One of the best known examples is the Berry phase [M.V. Berry (1984), Proc. Royal. Soc. London A, 392:45], which naturally emerges in quantum adiabatic evolution. So far the applicability and measurements of the Berry phase were mostly limited to systems of weakly interacting quasi-particles, where interference experiments are feasible. Here we show how one can go beyond this limitation and observe the Berry curvature, and hence the Berry phase, in generic systems as a nonadiabatic response of physical observables to the rate of change of an external parameter. These results can be interpreted as a dynamical quantum Hall effect in a parameter space. The conventional quantum Hall effect is a particular example of the general relation if one views the electric field as a rate of change of the vector potential. We illustrate our findings by analyzing the response of interacting spin chains to a rotating magnetic field. We observe the quantization of this response, which we term the rotational quantum Hall effect. PMID:22493228

Gritsev, V.; Polkovnikov, A.

2012-01-01

179

Quantum Logic Operations Using Single Photons and the Zeno Effect  

E-print Network

We show that the quantum Zeno effect can be used to implement several quantum logic gates for photonic qubits, including a gate that is similar to the square-root of SWAP operation. The operation of these devices depends on the fact that photons can behave as if they were non-interacting fermions instead of bosons in the presence of a strong Zeno effect. These results are discussed within the context of several no-go theorems for non-interacting fermions or bosons.

J. D. Franson; B. C. Jacobs; T. B. Pittman

2004-01-21

180

Effects of atomic interactions on Quantum Accelerator Modes  

E-print Network

We consider the influence of the inclusion of interatomic interactions on the delta-kicked accelerator model. Our analysis concerns in particular quantum accelerator modes, namely quantum ballistic transport near quantal resonances. The atomic interaction is modelled by a Gross-Pitaevskii cubic nonlinearity, and we address both attractive (focusing) and repulsive (defocusing) cases. The most remarkable effect is enhancement or damping of the accelerator modes, depending on the sign of the nonlinear parameter. We provide arguments showing that the effect persists beyond mean-field description, and lies within the experimentally accessible parameter range.

Laura Rebuzzini; Roberto Artuso; Shmuel Fishman; Italo Guarneri

2007-04-11

181

Fractional quantum Hall effect in AlAs quantum wells: Role of valley degree of freedom  

NASA Astrophysics Data System (ADS)

When interacting two-dimensional electrons are placed in a large perpendicular magnetic field, to minimize their energy, they capture an even number of flux quanta and create new particles called composite fermions (CFs). These complex electron-flux-bound states offer an elegant explanation for the fractional quantum Hall effect. Thanks to the flux attachment, the effective field vanishes at half-filled Landau levels (?= 1/2 and 3/2) and CFs exhibit Fermi-liquid-like properties, similar to their zero-field electron counterparts. Here, we study a two-dimensional electron system in AlAs quantum wells where the electrons occupy two conduction band valleys with anisotropic Fermi contours and strain-tunable occupation. We address a fundamental question whether the anisotropy of the electron effective mass and Fermi surface is transferred to the CFs formed around filling factors ?= 1/2 and 3/2. Similar to their electron counter parts, CFs also exhibit anisotropic transport, suggesting an anisotropy of CF effective mass and Fermi surface. We also study quantum Hall ferromagnetism for fractional quantum Hall states formed at ?= 1/3 and 5/3 as a function of valley splitting. Within the framework of the CF theory, electronic fractional filling factors ?= 1/3 and 5/3 are equivalent to the integer filling factor p= 1 of CFs. Reminiscent of the quantum Hall ferromagnetism observed at ?= 1, we report persistent fractional quantum Hall states at filling factors ?= 1/3 and 5/3 when the two valleys are degenerate. However, the comparison of the energy gaps measured at ?= 1/3 and 5/3 to the available theory developed for single-valley, two-spin systems reveals that the gaps and their rates of rise with strain are much smaller than predicted.[4pt] [1] ``Transference of Transport Anisotropy to Composite Fermions,'' T. Gokmen, M. Padmanabhan, and M. Shayegan, Nature Physics 6, 621-624 (2010).[4pt] [2] `Ferromagnetic Fractional Quantum Hall States in a Valley-Degenerate Two-Dimensional Electron System,'' M. Padmanabhan, T. Gokmen, and M. Shayegan, Phys. Rev. Lett. 104, 016805 (2010).

Gokmen, Tayfun

2013-03-01

182

Quantum Size Effects of Hydrogen Impurity at Off-Center Donor Atom in Spherical Quantum Dots  

NASA Astrophysics Data System (ADS)

We obtain the numerical solutions for a single electron energy level of a hydrogen impurity confined inside an off-center donor in a spherical quantum dot. The energy spectrum of single electron impurity for off-center donor atom subject to screened Coulomb's attractive potential barrier well is presented. Using B-spline finite element method, we generate a complete set of wavefunctions within the central unit cell, and through the perturbation theory, the whole energy spectrum of an impurity at low temperature can be explored. We find that the energy splitting and different related magnetic quantum number ml, i.e., (n, l, ml) varies with quantum dot size. This is due to the fact that quantum confinement effect lifts the degeneracy which comes from the Coulomb interaction. On the other hand, the phenomena of energy spectrum splitting under this model is an analogous case, considering that degeneracy of hydrogen energy levels in free space has been lifted by an external magnetic field (Zeeman effect).

Huang, Yung Sheng; Huang, Jung Sheng; Lee, Kuan Wei; Chang, Fang-Ling

183

Microscopic Properties of the Fractional Quantum Hall Effect  

NASA Astrophysics Data System (ADS)

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

Kou, Angela

184

Modeling Quantum Gravity Effects in Inflation  

E-print Network

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.

Emil J. Martinec; Wynton E. Moore

2014-01-29

185

Modeling quantum gravity effects in inflation  

NASA Astrophysics Data System (ADS)

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.

Martinec, Emil J.; Moore, Wynton E.

2014-07-01

186

Quantum gravity effects in Myers-Perry space-times  

NASA Astrophysics Data System (ADS)

We study quantum gravity effects for Myers-Perry black holes assuming that the leading contributions arise from the renormalization group evolution of Newton's coupling. Provided that gravity weakens following the asymptotic safety conjecture, we find that quantum effects lift a degeneracy of higher-dimensional black holes, and dominate over kinematical ones induced by rotation, particularly for small black hole mass, large angular momentum, and higher space-time dimensionality. Quantum-corrected space-times display inner and outer horizons, and show the existence of a black hole of smallest mass in any dimension. Ultra-spinning solutions no longer persist. Thermodynamic properties including temperature, specific heat, the Komar integrals, and aspects of black hole mechanics are studied as well. Observing a softening of the ring singularity, we also discuss the validity of classical energy conditions.

Litim, Daniel F.; Nikolakopoulos, Konstantinos

2014-04-01

187

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

NASA Astrophysics Data System (ADS)

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

Benatti, Fabio; Floreanini, Roberto; Scholes, Greg

2012-08-01

188

Deformed general relativity and effective actions in quantum gravity  

NASA Astrophysics Data System (ADS)

We will use canonical methods to construct effective actions from deformed covariance algebras, as implied by quantum-geometry corrections of loop quantum gravity. To this end, we extend classical constructions systematically to effective constraints of canonical quantum gravity and apply these constructions to model systems as well as general metrics, with the following conclusions: (i) Dispersion relations of matter and gravitational waves are deformed in related ways, ensuring a consistent realization of causality. (ii) Inverse-triad corrections modify the classical action in a way clearly distinguishable from curvature effects. In particular, these corrections can be significantly larger than often expected for standard quantum-gravity phenomena. (iii) Finally, holonomy corrections in high-curvature regimes do not signal the evolution from collapse to expansion in a "bounce," but rather the emergence of the universe from Euclidean space at high density. This new version of signature-change cosmology suggests a natural way of posing initial conditions, and a solution to the entropy problem. The aforementioned corrections of canonical quantum gravity modify spacetime structures, sometimes to the degree that no effective line elements exist to describe the geometry. An analysis of solutions, for instance in the context of black holes, then requires new insights. In this dissertation, standard definitions of horizons in spherical symmetry are first reformulated canonically, and then evaluated for solutions of equations and constraints modified by inverse-triad corrections of loop quantum gravity. For more general conclusions, canonical perturbation theory is developed to second order to include back-reaction from matter. The work described in this dissertation regarding deformed algebras and their implications for space-time, matter, the universe, and black holes is based on previous publications by the author and his collaborators, which may be consulted for further details and references.

Paily, George M.

189

Quantum mechanical effects on noise properties of nanoelectronic devices: application to Monte Carlo simulation  

Microsoft Academic Search

A discussion about the quantum mechanical effects on noise properties of ballistic (phase-coherent) nanoscale devices is presented. It is shown that quantum noise can be understood in terms of quantum trajectories. This interpretation provides a simple and intuitive explanation of the origin of quantum noise that can be very salutary for nanoelectronic engineers. In particular, an injection model is presented

Xavier Oriols

2003-01-01

190

Advanced theory of multiple exciton generation effect in quantum dots  

NASA Astrophysics Data System (ADS)

The theoretical aspects of the effect of multiple exciton generation (MEG) in quantum dots (QDs) have been analysed in this work. The statistical theory of MEG in QDs based on Fermi's approach is presented, taking into account the momentum conservation law. According to Fermi this approach should give the ultimate quantum efficiencies of multiple particle generation. The microscopic mechanism of this effect is based on the theory of electronic "shaking". According to this approach, the wave function of "shaking" electrons can be selected as Plato's functions with effective charges depending on the number of generated excitons. From the theory it is known increasing the number of excitons leads to enhancement of the Auger recombination of electrons which results in reduced quantum yields of excitons. The deviation of the averaged multiplicity of the MEG effect from the Poisson law of fluctuations has been investigated on the basis of synergetics approaches. In addition the role of interface electronic states of QDs and ligands has been considered by means of quantum mechanical approaches. The size optimisation of QDs has been performed to maximise the multiplicity of the MEG effect.

Oksengendler, B. L.; Turaeva, N. N.; Rashidova, S. S.

2012-06-01

191

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

NASA Astrophysics Data System (ADS)

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.

Ezawa, Motohiko

2013-12-01

192

Plasmonic effect on quantum coherence and interference in metallic photonic crystals doped with quantum dots  

SciTech Connect

We have studied the effect of plasma energy on the absorption coefficient of metallic photonic crystals doped with an ensemble of three-level quantum dots, which are interacting with each other via dipole-dipole interaction. The quantum dots are also interacting with coupled plasma-photon modes present in the system. A probe laser field is applied in order to study the absorption coefficient. We also consider the effect of quantum interference in our simulations, whereby two absorbed photons interfere with one another. Here the density matrix method has been used to calculate the steady-state and transient behavior of the absorption coefficient for the system. Two different field configurations are considered in our numerical simulations. In the first configuration, a probe field couples the ground state and two closely excited states. Absorption occurs due to transitions from the ground state to the two excited states. It is found that the position of the transparent peak moves when the plasma energy is changed. In other words, changing the plasma energy causes the system to switch between a transparent and an absorbing state. The strong coupling between plasmons and the quantum dots is responsible for this phenomenon. In the second configuration, the probe field couples with only one excited state, while a pump field couples to the other excited state. The transition between excited states is dipole forbidden. We observed that the peak in the absorption profile splits into two and also that the system exhibits gain with inversion due to the change in the plasma frequency, which is caused by quantum interference and coherence. These are interesting results and can be used make nanoscale plasma devices.

Hatef, Ali; Singh, Mahi R. [Department of Physics and Astronomy, The University of Western Ontario, 1151 Richmond Street, London, Ontario N6 A 3K7 (Canada)

2010-06-15

193

Photonic analogue of quantum spin Hall effect  

E-print Network

Symmetry-protected photonic topological insulator exhibiting robust pseudo-spin-dependent transportation, analogous to quantum spin Hall (QSH) phases and topological insulators, are of great importance in fundamental physics. Such transportation robustness is protected by time-reversal symmetry. Since electrons (fermion) and photons (boson) obey different statistics rules and associate with different time-reversal operators (i.e., Tf and Tb, respectively), whether photonic counterpart of Kramers degeneracy is topologically protected by bosonic Tb remains unidentified. Here, we construct the degenerate gapless edge states of two photonic pseudo-spins (left/right circular polarizations) in the band gap of a two-dimensional photonic crystal with strong magneto-electric coupling. We further demonstrated that the topological edge states are in fact protected by Tf rather than commonly believed Tb and their pseudo-spin dependent transportation is robust against Tf invariant impurities, discovering for the first tim...

He, Cheng; Liu, Xiao-ping; Lu, Ming-Hui; Chen, Yulin; Feng, Liang; Chen, Yan-Feng

2014-01-01

194

The Quantum Spin Hall Effect: Theory and Experiment  

SciTech Connect

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.

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

2010-03-19

195

Multiconfigurational nuclear-electronic orbital approach: Incorporation of nuclear quantum effects in electronic structure calculations  

E-print Network

Multiconfigurational nuclear-electronic orbital approach: Incorporation of nuclear quantum effects are that nuclear quantum effects are incorporated during the electronic structure calculation, the Born basis functions. They also enable the location and characterization of geometry stationary points

Hammes-Schiffer, Sharon

196

The Macroscopic Quantum Effect in Nonlinear Oscillating Systems: a Possible Bridge between Classical and Quantum Physics  

E-print Network

Einstein, De Broglie and others hoped that the schism between classical and quantum physics might one day be overcome by a theory taking into account the essential nonlinearity of elementary physical processes. However, neither their attempts, nor subsequent ones were able to supply a unifying principle that could serve as a starting-point for a coherent understanding of both microphysical and macroscopic phenomena. In the late 1960s the phenomenon of amplitude quantization, or Macroscopic Quantum Effect (MQE), was discovered in a class of nonlinear oscillating systems in which two or more subsystems are coupled to each other by interactions having a specific phase-dependent character -- so-called argumental interactions. Experimental and theoretical studies of the MQE, carried out up to the present time, suggest the possibility of a new conceptual framework for physics, which would provide a bridge between classical and quantum physics, replacing the Newtonian notion of "force" by a new conception of physical interaction. The present paper presents a brief introduction to the MQE and some ideas about its possible significance in the search for new approaches to the understanding of quantum phenomena.

Danil Doubochinski; Jonathan Tennenbaum

2007-11-30

197

Effects of Quantum Confinement on the Doping Limit of Semiconductor  

E-print Network

Effects of Quantum Confinement on the Doping Limit of Semiconductor Nanowires D. R. Khanal,, Joanne concentrations in semiconductor nanowires. Our calculations are based on the amphoteric defect model, which describes the thermodynamic doping limit in semiconductors in terms of the compensation of external dopants

Wu, Junqiao

198

Thermoelectric effects in Kondo-correlated quantum dots  

Microsoft Academic Search

In this letter we study thermoelectric effects in ultra-small quantum dots. We study the behaviour of the thermopower, Peltier coefficient and thermal conductance both in the sequential tunneling regime and in the regime where Kondo correlations develop. Both cases of linear response and non-equilibrium induced by strong temperature gradients are considered. The thermopower is a very sensitive tool to detect

Daniel Boese; Rosario Fazio

2001-01-01

199

Nuclear Quantum Vibrational Effects in Shock Hugoniot Temperatures  

SciTech Connect

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.

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

2009-07-23

200

Quantum plasmon effects in epsilon-near-zero metamaterials  

E-print Network

Dispersion properties of metals and propagation of quantum bulk plasmon in the high photon energy regime are studied. The nonlocal dielectric permittivity of a metal is determined by the quantum plasma effects and is calculated by applying the Wigner equation in the kinetic theory and taking into account the electron lattice collisions. The properties of epsilon near zero material are investigated in a thin gold film. The spectrum and the damping rate of the quantum bulk plasmon are obtained for a wide range of energies, and the electron wave function is analytically calculated in both classical and quantum limits. It is shown that the quantum bulk plasmons exist with a propagation length of 1 to 10nm, which strongly depends on the electron energy. The propagation length is found to be much larger than the propagation length in the classical regime which is comparable to the atomic radius and the average inter particle distance. It is found that the spatial localization of the electron wave function is extend...

Moaied, M; Ostrikov, K

2014-01-01

201

On the Convergence in Effective Loop Quantum Cosmology  

SciTech Connect

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.

Corichi, Alejandro [Instituto de Matematicas, Universidad Nacional Autonoma de Mexico, A. Postal 61-3, Morelia, Michoacan 58090 (Mexico); Center for Fundamental Theory, Institute for Gravitation and the Cosmos, Pennsylvania State University, University Park PA 16802 (United States); Vukasinac, Tatjana [Facultad de Ingenieria Civil, Universidad Michoacana de San Nicolas de Hidalgo Morelia, Michoacan 58000 (Mexico); Zapata, Jose Antonio [Instituto de Matematicas, Universidad Nacional Autonoma de Mexico, A. Postal 61-3, Morelia, Michoacan 58090 (Mexico)

2010-07-12

202

Strong quantum-confined Stark effect in germanium quantum-well structures on silicon  

NASA Astrophysics Data System (ADS)

Silicon is the dominant semiconductor for electronics, but there is now a growing need to integrate such components with optoelectronics for telecommunications and computer interconnections. Silicon-based optical modulators have recently been successfully demonstrated; but because the light modulation mechanisms in silicon are relatively weak, long (for example, several millimetres) devices or sophisticated high-quality-factor resonators have been necessary. Thin quantum-well structures made from III-V semiconductors such as GaAs, InP and their alloys exhibit the much stronger quantum-confined Stark effect (QCSE) mechanism, which allows modulator structures with only micrometres of optical path length. Such III-V materials are unfortunately difficult to integrate with silicon electronic devices. Germanium is routinely integrated with silicon in electronics, but previous silicon-germanium structures have also not shown strong modulation effects. Here we report the discovery of the QCSE, at room temperature, in thin germanium quantum-well structures grown on silicon. The QCSE here has strengths comparable to that in III-V materials. Its clarity and strength are particularly surprising because germanium is an indirect gap semiconductor; such semiconductors often display much weaker optical effects than direct gap materials (such as the III-V materials typically used for optoelectronics). This discovery is very promising for small, high-speed, low-power optical output devices fully compatible with silicon electronics manufacture.

Kuo, Yu-Hsuan; Lee, Yong Kyu; Ge, Yangsi; Ren, Shen; Roth, Jonathan E.; Kamins, Theodore I.; Miller, David A. B.; Harris, James S.

2005-10-01

203

Strong quantum-confined Stark effect in germanium quantum-well structures on silicon.  

PubMed

Silicon is the dominant semiconductor for electronics, but there is now a growing need to integrate such components with optoelectronics for telecommunications and computer interconnections. Silicon-based optical modulators have recently been successfully demonstrated; but because the light modulation mechanisms in silicon are relatively weak, long (for example, several millimetres) devices or sophisticated high-quality-factor resonators have been necessary. Thin quantum-well structures made from III-V semiconductors such as GaAs, InP and their alloys exhibit the much stronger quantum-confined Stark effect (QCSE) mechanism, which allows modulator structures with only micrometres of optical path length. Such III-V materials are unfortunately difficult to integrate with silicon electronic devices. Germanium is routinely integrated with silicon in electronics, but previous silicon-germanium structures have also not shown strong modulation effects. Here we report the discovery of the QCSE, at room temperature, in thin germanium quantum-well structures grown on silicon. The QCSE here has strengths comparable to that in III-V materials. Its clarity and strength are particularly surprising because germanium is an indirect gap semiconductor; such semiconductors often display much weaker optical effects than direct gap materials (such as the III-V materials typically used for optoelectronics). This discovery is very promising for small, high-speed, low-power optical output devices fully compatible with silicon electronics manufacture. PMID:16251959

Kuo, Yu-Hsuan; Lee, Yong Kyu; Ge, Yangsi; Ren, Shen; Roth, Jonathan E; Kamins, Theodore I; Miller, David A B; Harris, James S

2005-10-27

204

Characterization of control noise effects in optimal quantum unitary dynamics  

E-print Network

The control of quantum mechanical unitary transformations naturally calls for a degree of resilience to control field noise. While consideration of noise effects in quantum systems has been an area of active study, the relationship between optimal solutions and those that are both optimal and robust to noise is still not generally understood. This work defines measures for quantifying the effects of field noise upon targeted unitary transformations. Robustness to noise is assessed in the framework of the quantum control landscape, which is the mapping from the control to the unitary transformation performance measure. Within that framework, more robust optimal controls are associated with regions of low landscape curvature. The utility of this perspective when considering the effects of noise is demonstrated through numerical simulations of the overlap between directions of significant curvature on the landscape and noise correlation functions. These simulations demonstrate both the rich and varied nature of optimal and robust controls, as well as reveal distinct noise spectral regimes that support robust control solutions for a class of transformations considered in quantum information processing.

David Hocker; Constantin Brif; Matthew D. Grace; Ashley Donovan; Tak-San Ho; Katharine W. Moore Tibbetts; Rebing Wu; Herschel Rabitz

2014-05-23

205

Quantum mechanical effects of topological origin  

NASA Technical Reports Server (NTRS)

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

Duru, I. H.

1993-01-01

206

Hybrid approach for including electronic and nuclear quantum effects in molecular dynamics simulations of hydrogen transfer  

E-print Network

, as well as the dynamics of the complete enzyme and solvent. The nuclear quantum effects are incorporated and nuclear quantum effects, as well as the dynamics of the sol- vent and protein. The incorporationHybrid approach for including electronic and nuclear quantum effects in molecular dynamics

Hammes-Schiffer, Sharon

207

Thermal recoil force, telemetry, and the Pioneer anomaly  

SciTech Connect

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.

Toth, Viktor T.; Turyshev, Slava G. [Ottawa, Ontario K1N 9H5 (Canada); Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, California 91109-8099 (United States)

2009-02-15

208

Thermal recoil force, telemetry, and the Pioneer anomaly  

E-print Network

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.

Viktor T. Toth; Slava G. Turyshev

2009-01-29

209

Thermal recoil force, telemetry, and the Pioneer anomaly  

E-print Network

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.

Toth, Viktor T

2009-01-01

210

Effect of quantum therapy on pork quality  

PubMed Central

In this study the impact of quantum therapy on meat quality of slaughtered pigs was investigated. For this purpose the pigs were treated with different doses of magnet-infrared-laser (MIL) radiation. Animals were divided into four groups according to radiation doses (4096, 512, and 64 Hz, and control without application), which were applied in the lumbar area of musculus longissimus dorsi (loin) at various time intervals prior to the slaughter (14 d, 24 h, and 1 h). Animals were slaughtered and the meat quality was evaluated by determining of pH value (1, 3, and 24 h post slaughter), drip loss, colour, and lactic acid and phosphoric acid amounts. MIL therapy can be used in various fields of veterinary medicine as are surgery and orthopaedics, internal medicine, dentistry, pulmonology, gastroenterology, gynaecology, urology, nephrology, and dermatology. The results achieved showed that MIL radiation used in a short period before slaughter (1 h) can cause a change in the meat quality, as reflected by the non-standard development of pH values, increases in drip loss, and changes of meat colour. PMID:22042653

Bodnar, Martin; Nagy, Jozef; Popelka, Peter; Korenekova, Beata; Macanga, Jan; Nagyova, Alena

2011-01-01

211

Neutron electric form factor via recoil polarimetry  

SciTech Connect

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.

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

2003-05-01

212

Quantum corrections to spin effects in general relativity  

E-print Network

Quantum power corrections to the gravitational spin-orbit and spin-spin interactions, as well as to the Lense-Thirring effect, were found for particles of spin 1/2. These corrections arise from diagrams of second order in Newton gravitational constant G with two massless particles in the unitary cut in the t-channel. The corrections obtained differ from the previous calculation of the corrections to spin effects for rotating compound bodies with spinless constituents.

G. G. Kirilin

2005-07-16

213

Linear and nonlinear electrostatic modes in a strongly coupled quantum plasma  

NASA Astrophysics Data System (ADS)

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.

Ghosh, Samiran; Chakrabarti, Nikhil; Shukla, P. K.

2012-07-01

214

Quantum coherence rather than quantum correlations reflect the effects of a reservoir on a system's work capability  

NASA Astrophysics Data System (ADS)

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.

Li, Hai; Zou, Jian; Yu, Wen-Li; Xu, Bao-Ming; Li, Jun-Gang; Shao, Bin

2014-05-01

215

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

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

216

Nonadiabatic effect on the quantum heat flux control  

NASA Astrophysics Data System (ADS)

We provide a general formula of quantum transfer that includes the nonadiabatic effect under periodic environmental modulation by using full counting statistics in Hilbert-Schmidt space. Applying the formula to an anharmonic junction model that interacts with two bosonic environments within the Markovian approximation, we find that the quantum transfer is divided into the adiabatic (dynamical and geometrical phases) and nonadiabatic contributions. This extension shows the dependence of quantum transfer on the initial condition of the anharmonic junction just before the modulation, as well as the characteristic environmental parameters such as interaction strength and cut-off frequency of spectral density. We show that the nonadiabatic contribution represents the reminiscent effect of past modulation including the transition from the initial condition of the anharmonic junction to a steady state determined by the very beginning of the modulation. This enables us to tune the frequency range of modulation, whereby we can obtain the quantum flux corresponding to the geometrical phase by setting the initial condition of the anharmonic junction.

Uchiyama, Chikako

2014-05-01

217

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

SciTech Connect

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

Zhang, Li-Ping; Xue, Ju-Kui [College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou 730070 (China)] [College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou 730070 (China)

2013-08-15

218

Large size self-assembled quantum rings: quantum size effect and modulation on the surface diffusion  

PubMed Central

We demonstrate experimentally the submicron size self-assembled (SA) GaAs quantum rings (QRs) by quantum size effect (QSE). An ultrathin In0.1?Ga0.9As layer with different thickness is deposited on the GaAs to modulate the surface nucleus diffusion barrier, and then the SA QRs are grown. It is found that the density of QRs is affected significantly by the thickness of inserted In0.1?Ga0.9As, and the diffusion barrier modulation reflects mainly on the first five monolayer . The physical mechanism behind is discussed. The further analysis shows that about 160 meV decrease in diffusion barrier can be achieved, which allows the SA QRs with density of as low as one QR per 6 ?m2. Finally, the QRs with diameters of 438 nm and outer diameters of 736 nm are fabricated using QSE. PMID:23006618

2012-01-01

219

Running of Newton's Constant and Quantum Gravitational Effects  

E-print Network

Newton's gravitational constant is shown to be a running coupling constant, much like the familiar running gauge couplings of the Standard Model. This implies that, in models with appropriate particle content, the true Planck scale, i.e. the scale at which quantum gravity effects become important, can have a value different from 10^19 GeV, which would be expected from naive dimensional analysis. Then, two scenarios involving this running effect are presented. The first one is a model which employs huge particle content to realize quantum gravity at the TeV scale in 4 dimensions, thereby solving the hierarchy problem of the Standard Model. Secondly, effects of the running of Newton's constant in grand unified theories are examined and shown to introduce new significant uncertainties in their predictions, but possibly also to provide better gauge coupling unification results in some cases.

David Reeb

2009-01-20

220

Evanescent radiation, quantum mechanics and the Casimir effect  

NASA Technical Reports Server (NTRS)

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.

Schatten, Kenneth H.

1989-01-01

221

The Unruh effect interpreted as a quantum noise channel  

E-print Network

We derive the operator-sum representation for the noise channel that acts on a mode of a free Dirac field, as seen by a relativistically accelerated observer. A modal qubit thus appears as if subjected to quantum noise that degrades quantum information, as observed in the accelerated reference frame. We compare and contrast this noise channel, which arises from the Unruh effect, from a conventional noise due to environmental decoherence. We show that the Unruh channel produces an amplitude damping like effect, associated with zero temperature, even though the Unruh effect is associated with a non-zero temperature. Asymptotically, the Bloch sphere subjected to the channel does not converge to a point, as would be expected by fluctuation-dissipation arguments, but contracts by a finite factor. We note that turning off the drive that generates the acceleration corresponds to a non-completely-positive (NCP) map.

Omkar, S; Srikanth, R; Alok, Ashutosh Kumar

2014-01-01

222

The Unruh effect interpreted as a quantum noise channel  

E-print Network

We derive the operator-sum representation for the noise channel that acts on a mode of a free Dirac field, as seen by a relativistically accelerated observer. A modal qubit thus appears as if subjected to quantum noise that degrades quantum information, as observed in the accelerated reference frame. We compare and contrast this noise channel, which arises from the Unruh effect, from a conventional noise due to environmental decoherence. We show that the Unruh channel produces an amplitude damping like effect, associated with zero temperature, even though the Unruh effect is associated with a non-zero temperature. Asymptotically, the Bloch sphere subjected to the channel does not converge to a point, as would be expected by fluctuation-dissipation arguments, but contracts by a finite factor. We note that turning off the drive that generates the acceleration corresponds to a non-completely-positive (NCP) map.

S. Omkar; Subhashish Banerjee; R. Srikanth; Ashutosh Kumar Alok

2014-08-07

223

Memory effects in attenuation and amplification quantum processes  

SciTech Connect

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

Lupo, Cosmo [School of Science and Technology, University of Camerino, via Madonna delle Carceri 9, I-62032 Camerino (Italy); Giovannetti, Vittorio [NEST, Scuola Normale Superiore and Istituto Nanoscienze-CNR, Piazza dei Cavalieri 7, I-56126 Pisa (Italy); Mancini, Stefano [School of Science and Technology, University of Camerino, via Madonna delle Carceri 9, I-62032 Camerino (Italy); INFN-Sezione di Perugia, I-06123 Perugia (Italy)

2010-09-15

224

Simple computer model for the quantum Zeno effect  

E-print Network

This paper presents a simple model for repeated measurement of a quantum system: the evolution of a free particle, simulated by discretising the particle's position. This model is easily simulated by computer and provides a useful arena to investigate the effects of measurement upon dynamics, in particular the slowing of evolution due to measurement (the `quantum Zeno effect'). The results of this simulation are discussed for two rather different sorts of measurement process, both of which are (simplified forms of) measurements used in previous simulations of position measurement. A number of interesting results due to measurement are found, and the investigation casts some light on previous disagreements about the presence or absence of the Zeno effect.

David Wallace

2000-04-03

225

Quantum anti-Zeno effect without rotating wave approximation  

SciTech Connect

In this article, we systematically study the spontaneous decay phenomenon of a two-level system under the influences of both its environment and repetitive measurements. In order to clarify some well-established conclusions about the quantum Zeno effect (QZE) and the quantum anti-Zeno effect (QAZE), we do not use the rotating wave approximation (RWA) in obtaining an effective Hamiltonian. We examine various spectral distributions by making use of our present approach in comparison with other approaches. It is found that with respect to a bare excited state even without the RWA, the QAZE can still happen for some cases, for example, the interacting spectra of hydrogen. However, for a physical excited state, which is a renormalized dressed state of the atomic state, the QAZE disappears and only the QZE remains. These discoveries inevitably show a transition from the QZE to the QAZE as the measurement interval changes.

Ai Qing; Sun, C. P. [Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing 100190 (China); Li Yong [Department of Physics and Center of Theoretical and Computational Physics, University of Hong Kong, Pokfulam Road (Hong Kong); Zheng Hang [Department of Physics, Shanghai Jiao Tong University, Shanghai 200030 (China)

2010-04-15

226

Jet Extinction from Non-Perturbative Quantum Gravity Effects  

E-print Network

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

Can Kilic; Amitabh Lath; Keith Rose; Scott Thomas

2012-07-15

227

Quantum metrology and the detection of Unruh effect  

E-print Network

We study the quantum metrology for a pair of entangled Unruh-Dewitt detectors coupled to a massless scalar field when one of them is accelerated. Comparing with previous schemes, our model requires only local interaction and avoids the use of cavities in the probe state preparation process. We show that the accelerated motion and the interaction between the accelerated detector and the external field have significant effects on the value of quantum Fisher information, correspondingly pose variable ultimate limit of precision in the detection of Unruh effect. We find that the precision of the estimation can be improved by a larger effective coupling strength and a longer interaction time. In contrast, there are a range of accelerations and energy gaps of the detector that provide us with a better precision in the estimation. Thus we may adjust those parameters in the scheme of the detection.

Wang, Jieci; Jing, Jiliang; Fan, Heng

2014-01-01

228

Memory effects in attenuation and amplification quantum processes  

E-print Network

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

Cosmo Lupo; Vittorio Giovannetti; Stefano Mancini

2010-05-17

229

Neutron star recoils from anisotropic supernovae.  

NASA Astrophysics Data System (ADS)

Refering to recent hydrodynamical computations (Herant et al. 1992; Janka & Mueller 1993a) it is argued that neutron star kicks up to a few hundred km/s might be caused by a turbulent overturn of the matter between proto-neutron star and supernova shock during the early phase of the supernova explosion. These recoil speeds ("kick velocities") may be of the right size to explain the measured proper motions of most pulsars and do not require the presence of magnetic fields in the star. It is also possible that anisotropic neutrino emission associated with convective processes in the surface layers of the nascent neutron star (Burrows & Fryxell 1992; Janka & Mueller 1993b; Mueller 1993) provides an acceleration mechanism (Woosley 1987), although our estimates indicate that the maximum attainable velocities are around 200km/s. Yet, it turns out to be very unlikely that the considered stochastic asymmetries of supernova explosions are able to produce large enough recoils to account for pulsar velocities in excess of about 500km/s, which can be found in the samples of Harrison et al. (1993) and Taylor et al. (1993). It is concluded that other acceleration mechanisms have to be devised to explain the fast motion of PSR 2224+65 (transverse speed >=800km/s Cordes et al. 1993) and the high-velocities deduced from associations between supernova remnants and nearby young pulsars (e.g., Frail & Kulkarni 1991; Stewart et al. 1993; Caraveo 1993).

Janka, H.-T.; Mueller, E.

1994-10-01

230

Secular effects on inflation from one-loop quantum gravity  

E-print Network

In this paper we revisit and extend a previous analysis where the possible relevance of quantum gravity effects in a cosmological setup was studied. The object of interest are non-local (logarithmic) terms generated in the effective action of gravity due to the exchange in loops of massless modes (such as photons or the gravitons themselves). We correct one mistake existing in the previous work and discuss the issue in a more general setting in different cosmological scenarios. We obtain the one-loop quantum-corrected evolution equations for the cosmological scale factor up to a given order in a derivative expansion in two particular cases: a matter dominated universe with vanishing cosmological constant, and in a de Sitter universe. We show that the quantum corrections, albeit tiny, may have a secular effect that eventually modifies the expansion rate. For a de Sitter universe they tend to slow down the rate of the expansion, while the effect seems to have the opposite sign in a matter dominated universe. To partly understand these effects we provide a complementary newtonian analysis.

J. A. Cabrer; D. Espriu

2007-10-03

231

Transforming quantum operations: quantum supermaps  

E-print Network

We introduce the concept of quantum supermap, describing the most general transformation that maps an input quantum operation into an output quantum operation. Since quantum operations include as special cases quantum states, effects, and measurements, quantum supermaps describe all possible transformations between elementary quantum objects (quantum systems as well as quantum devices). After giving the axiomatic definition of supermap, we prove a realization theorem, which shows that any supermap can be physically implemented as a simple quantum circuit. Applications to quantum programming, cloning, discrimination, estimation, information-disturbance trade-off, and tomography of channels are outlined.

G. Chiribella; G. M. D'Ariano; P. Perinotti

2008-04-01

232

Efficient semiclassical quantum nuclear effects for shock compression studies  

NASA Astrophysics Data System (ADS)

A fast methodology is described for atomistic simulations of shock-compressed materials that incorporates quantum nuclear effects in a self-consistent fashion. We introduce a modification of the multiscale shock technique (MSST) that couples to a quantum thermal bath described by a colored noise Langevin thermostat. The new approach, which we call QB-MSST, is of comparable computational cost to MSST and self-consistently incorporates quantum heat capacities and Bose-Einstein harmonic vibrational distributions. As a first test, we study shock-compressed methane using the ReaxFF potential. The Hugoniot curves predicted from the new approach are found comparable with existing experimental data. We find that the self-consistent nature of the method results in the onset of chemistry at 40% lower pressure on the shock Hugoniot than observed with classical molecular dynamics. The temperature shift associated with quantum heat capacity is determined to be the primary factor in this shift.[4pt] In collaboration with Tingting Qi, Department of Materials Science and Engineering, Stanford University.

Reed, Evan

2013-03-01

233

Spin-Orbit Effects in Coupled Quantum Dots  

NASA Astrophysics Data System (ADS)

While in some materials, such as GaAs, the spin-orbit (SOE) effects are of relatively minor importance, it has been recently shown that they are very important for quantum dots in materials with narrow gap and small effective-mass electrons [1]. Then, spin and orbital enginnering could be more easily achieved with these materials. Coupled dots, due to the double-well confinement potential, are expected to show even stronger effects, which might be useful in the design of quantum computers and spintronic devices. Here we study SOE in pairs of coupled-dots. Competition between the terms derived from the confinement potential, magnetic field and their effects on the single- and two-particle spectra are analyzed. Circular quantum dots are considered and geometrics aspects of the confinement such as barrier height, separation between the dots, etc., are varied. The single-particle wave functions are determined for a given geometry using the finite-element method. Additional terms in the Hamiltonian are considered within a full-diagonalization scheme. and include different SOE, as well as Coulomb interactions in the case of multiple electrons. [1] See C.F. Destefani, et. al., cond-mat/0307027 and references therein.

Meza-Montes, Lilia; Ulloa, Sergio. E.

2004-03-01

234

Physics and application of the quantum Hall effect  

NASA Astrophysics Data System (ADS)

The High Magnetic Field Laboratory in Grenoble is the birthplace of the quantum Hall effect (QHE). In the morning of the 5th of February 1980 - during a magnetotransport experiment on silicon field-effect transistors - the idea came up to measure deviations of the Hall resistance relative to a quantized value which can be calculated on the basis of a simple one-electron picture. The analysis of the experimental data showed immediately that the deviations are unmeasurably small and today it is generally accepted that the quantized Hall resistance depends exclusively on fundamental constants. This result opened a new research field. In this paper only recent developments in the application of the QHE in metrology and the connection of the quantized Hall resistance with the quantization of the resistance of quantum point contacts, which was discovered in 1988, will be summarized.

v. Klitzing, Klaus

1995-02-01

235

Physics and application of the quantum Hall effect  

NASA Astrophysics Data System (ADS)

The High Magnetic Field Laboratory in Grenoble is the birthplace of the quantum Hall effect (QHE). In the morning of the 5th of February 1980 - during a magnetotransport experiment on silicon field-effect transistors - the idea came up to measure deviations of the Hall resistance relative to a quantized value which can be calculated on the basis of a simple one-electron picture. The analysis of the experimental data showed immediately that the deviations are unmeasurably small and today it is generally accepted that the quantized Hall resistance depends exclusively on fundamental constants. This result opened a new research field. In this paper only recent developments in the application of the QHE in metrology and the connection of the quantized Hall resistance with the quantization of the resistance of quantum point contacts, which was discovered in 1988, will be summarized.

Klitzing, Klaus v.

236

Charge Fractionalization in the Integer Quantum Hall Effect  

NASA Astrophysics Data System (ADS)

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.

Inoue, Hiroyuki; Grivnin, Anna; Ofek, Nissim; Neder, Izhar; Heiblum, Moty; Umansky, Vladimir; Mahalu, Diana

2014-04-01

237

Heat capacity of water: A signature of nuclear quantum effects  

NASA Astrophysics Data System (ADS)

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.

Vega, C.; Conde, M. M.; McBride, C.; Abascal, J. L. F.; Noya, E. G.; Ramirez, R.; Ses, L. M.

2010-01-01

238

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

PubMed

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 He? + H2 reaction. PMID:25188920

Posada, Edwin; Moncada, Flix; Reyes, Andrs

2014-10-01

239

Isotope Quantum Effects on the Water Proton Mean Kinetic Energy  

Microsoft Academic Search

A deep inelastic neutron scattering experiment, performed on D2O in the stable and metastable liquid phases, provides evidence for isotope quantum effects in the proton or deuteron single particle dynamics along the hydrogen bond. The deuteron mean kinetic energy extracted from the experimental data in the metastable supercooled phase (T=276.15K) exceeds the zero point energy and scales as 2 with

A. Giuliani; F. Bruni; M. A. Ricci; M. A. Adams

2011-01-01

240

Integer quantum Hall effect in isotropic 3D systems  

Microsoft Academic Search

We study whether the quantum Hall effect (QHE) predicted to occur in three-dimensional (3D) anisotropic systems by Koshino et al. [Phys. Rev. Lett. 86 (2001) 1062] can also exist in isotropic 3D crystals from two different limits. We show, in both the tight-binding model and the weak potential limit, that energy gaps, accompanied by the QHE, arise universally unless the

M. Koshino; H. Aoki

2004-01-01

241

Nonmagnetic impurity effects in a quantum Hall system  

NASA Astrophysics Data System (ADS)

Effects of nonmagnetic impurities on a quantum Hall system are studied. Numerical calculations at the filling factor ?=1 are carried out using formalism of second quantization. It is found that there is a critical number of impurities above which the property of the ground state is changed abruptly. As an evidence of this abrupt change, the charge density and the spin density for the ground state are explicitly shown in the cases of various numbers of impurities.

Chung, Myung-Hoon; You, Sang Koo; Yong, Dae-Young; Kim, Chul Koo; Nahm, Kyun; Ahn, Kang-Hun

2000-02-01

242

Quantum instanton evaluation of the kinetic isotope effects  

SciTech Connect

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%.

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

2005-04-19

243

Semiclassical states, effective dynamics, and classical emergence in loop quantum cosmology  

NASA Astrophysics Data System (ADS)

We construct physical semiclassical states annihilated by the Hamiltonian constraint operator in the framework of loop quantum cosmology as a method of systematically determining the regime and validity of the semiclassical limit of the quantum theory. Our results indicate that the evolution can be effectively described using continuous classical equations of motion with nonperturbative corrections down to near the Planck scale below which the Universe can only be described by the discrete quantum constraint. These results, for the first time, provide concrete evidence of the emergence of classicality in loop quantum cosmology and also clearly demarcate the domain of validity of different effective theories. We prove the validity of modified Friedmann dynamics incorporating discrete quantum geometry effects which can lead to various new phenomenological applications. Furthermore the understanding of semiclassical states allows for a framework for interpreting the quantum wave functions and understanding questions of a semiclassical nature within the quantum theory of loop quantum cosmology.

Singh, Parampreet; Vandersloot, Kevin

2005-10-01

244

On the Existence of Quantum Wave Function and Quantum Interference Effects in Mental States: An Experimental Confirmation during Perception and Cognition in Humans  

E-print Network

We introduce the quantum theoretical formulation to determine a posteriori, if existing, the quantum wave functions and to estimate the quantum interference effects of mental states. Such quantum features are actually found in the case of an experiment involving the perception and the cognition in humans. Also some specific psychological variables are introduced and it is obtained that they characterize in a stringent manner the quantum behaviour of mind during such performed experiment.

Elio Conte; Andrei Yuri Khrennikov; Orlando Todarello; Antonio Federici; Joseph P. Zbilut

2008-07-28

245

Effective particle kinematics from quantum gravity  

SciTech Connect

Particles propagating in de Sitter spacetime can be described by the topological BF SO(4,1) theory coupled to point charges. Gravitational interaction between them can be introduced by adding to the action a symmetry breaking term, which reduces the local gauge symmetry down to SO(3,1), and which can be treated as a perturbation. In this paper we focus solely on topological interactions which correspond to zeroth order in this perturbative expansion. We show that in this approximation the system is effectively described by the SO(4,1) Chern-Simons theory coupled to particles and living on the three-dimensional boundary of spacetime. Then, using Alekseev-Malkin construction we find the effective theory of particles kinematics. We show that the particles action contains standard kinetic terms and the deformation shows up in the presence of interaction terms. The strength of the interactions is proportional to deformation parameter, identified with Planck mass scale.

Kowalski-Glikman, Jerzy; Starodubtsev, Artem [Institute for Theoretical Physics, University of Wroclaw, Pl. Maxa Borna 9, Pl-50-204 Wroclaw (Poland); Centre de Physique Theorique de Luminy, F-13288 Marseille (France)

2008-10-15

246

Effective particle kinematics from Quantum Gravity  

E-print Network

Particles propagating in de Sitter spacetime can be described by the topological BF $\\SO(4,1)$ theory coupled to point charges. Gravitational interaction between them can be introduced by adding to the action a symmetry breaking term, which reduces the local gauge symmetry down to $\\SO(3,1)$, and which can be treated as a perturbation. In this paper we focus solely on topological interactions which corresponds to zeroth order in this perturbative expansion. We show that in this approximation the system is effectively described by the $\\SO(4,1)$ Chern-Simons theory coupled to particles and living on the 3 dimensional boundary of space-time. Then, using Alekseev--Malkin construction we find the effective theory of particles kinematics. We show that the particles action contains standard kinetic terms and the deformation shows up in the presence of interaction terms. The strength of the interactions is proportional to deformation parameter, identified with Planck mass scale.

Jerzy Kowalski-Glikman; Artem Starodubtsev

2008-08-19

247

Cancer proliferation and therapy: the Warburg effect and quantum metabolism  

PubMed Central

Background Most cancer cells, in contrast to normal differentiated cells, rely on aerobic glycolysis instead of oxidative phosphorylation to generate metabolic energy, a phenomenon called the Warburg effect. Model Quantum metabolism is an analytic theory of metabolic regulation which exploits the methodology of quantum mechanics to derive allometric rules relating cellular metabolic rate and cell size. This theory explains differences in the metabolic rates of cells utilizing OxPhos and cells utilizing glycolysis. This article appeals to an analytic relation between metabolic rate and evolutionary entropy - a demographic measure of Darwinian fitness - to: (a) provide an evolutionary rationale for the Warburg effect, and (b) propose methods based on entropic principles of natural selection for regulating the incidence of OxPhos and glycolysis in cancer cells. Conclusion The regulatory interventions proposed on the basis of quantum metabolism have applications in therapeutic strategies to combat cancer. These procedures, based on metabolic regulation, are non-invasive, and complement the standard therapeutic methods involving radiation and chemotherapy PMID:20085650

2010-01-01

248

Nuclear quantum effects and hydrogen bond fluctuations in water  

PubMed Central

The hydrogen bond (HB) is central to our understanding of the properties of water. However, despite intense theoretical and experimental study, it continues to hold some surprises. Here, we show from an analysis of ab initio simulations that take proper account of nuclear quantum effects that the hydrogen-bonded protons in liquid water experience significant excursions in the direction of the acceptor oxygen atoms. This generates a small but nonnegligible fraction of transient autoprotolysis events that are not seen in simulations with classical nuclei. These events are associated with major rearrangements of the electronic density, as revealed by an analysis of the computed Wannier centers and 1H chemical shifts. We also show that the quantum fluctuations exhibit significant correlations across neighboring HBs, consistent with an ephemeral shuttling of protons along water wires. We end by suggesting possible implications for our understanding of how perturbations (solvated ions, interfaces, and confinement) might affect the HB network in water. PMID:24014589

Ceriotti, Michele; Cuny, Jerome; Parrinello, Michele; Manolopoulos, David E.

2013-01-01

249

Effects of Quantum Error Correction on Entanglement Sudden Death  

E-print Network

We investigate the effects of error correction on non-local quantum coherence as a function of time, extending the study by Sainz and Bj\\"ork. We consider error correction of amplitude damping, pure phase damping and combinations of amplitude and phase damping as they affect both fidelity and quantum entanglement. Initial two-qubit entanglement is encoded in arbitrary real superpositions of both \\Phi-type and \\Psi-type Bell states. Our main focus is on the possibility of delay or prevention of ESD (early stage decoherence, or entanglement sudden death). We obtain the onset times for ESD as a function of the state-superposition mixing angle. Error correction affects entanglement and fidelity differently, and we exhibit initial entangled states for which error correction increases fidelity but decreases entanglement, and vice versa.

Muhammed Yna; J. H. Eberly

2012-11-24

250

Effective State Metamorphosis in Semi-Classical Loop Quantum Cosmology  

E-print Network

Modification to the behavior of geometrical density at short scales is a key result of loop quantum cosmology, responsible for an interesting phenomenology in the very early universe. We demonstrate the way matter with arbitrary scale factor dependence in Hamiltonian incorporates this change in its effective dynamics in the loop modified phase. For generic matter, the equation of state starts varying near a critical scale factor, becomes negative below it and violates strong energy condition. This opens a new avenue to generalize various phenomenological applications in loop quantum cosmology. We show that different ways to define energy density may yield radically different results, especially for the case corresponding to classical dust. We also discuss implications for frequency dispersion induced by modification to geometric density at small scales.

Parampreet Singh

2005-02-21

251

Decoherence effects on weak value measurements in double quantum dots  

NASA Astrophysics Data System (ADS)

We study the effect of decoherence on a weak value measurement in a paradigm system consisting of a double quantum dot continuously measured by a quantum point contact. Fluctuations of the parameters controlling the dot state induce decoherence. We find that, for measurements longer than the decoherence time, weak values are always reduced within the range of the eigenvalues of the measured observable. For measurements at shorter time scales, the measured weak value strongly depends on the interplay between the decoherence dynamics of the system and the detector backaction. In particular, depending on the postselected state and the strength of the decoherence, a more frequent classical readout of the detector might lead to an enhancement of weak values.

Thomas, Mark; Romito, Alessandro

2012-12-01

252

Separation of the alpha-emitting radioisotopes actinium-225 and bismuth-213 from thorium-229 using alpha recoil methods  

NASA Astrophysics Data System (ADS)

An innovative method has been demonstrated for separating alpha-emitting isotopes for medical radiotherapy applications. The method relies on recoil-ion separation rather than on conventional wet chemistry techniques to separate medical isotopes from their precursor sources. The isotopes 225Ac and 213Bi have been separated from electro-deposited sources of 229ThO 2. Separations of 225Ac were carried out by placing nickel recoil collector foils in firm contact with the 229ThO 2 sources. One-stage recoil-ion separations of 225Ac from 229Th have been performed as well as two-stage separations of 213Bi from previously recoil separated 225Ac. In addition, a direct recoil separation of 213Bi from 229Th has been demonstrated. The 213Bi from the one-stage direct separation has a high isotopic purity, but contains small amounts of long-lived 225Ac alpha activity. The two-stage separations of 213Bi produce high isotopic purity material (>99.9999%), but result in lower isotopic yields. Range-energy calculations have been carried out to determine the yields of recoil ions as a function of alpha-particle energy and ThO 2 thickness. The results of the calculations have been benchmarked with recoil separation measurements carried out using ThO 2 electro-deposits over a range of thickness. A computer code based on the generalized Bateman equations has been developed to allow calculations of the amounts of any isotope in the 229Th decay chain as a function of recoil separation exposure time and elapsed time after the separation. An excellent match has been obtained between the predictions of the Bateman calculations and the results of recoil separation measurements. The recoil separation method has proven to be a simple and effective way of separating medically useful isotopes such as 213Bi. In addition, the method has been shown to produce no chemical or radioactive wastes, in contrast to radiochemical separation methods, which generate mixed (chemical and radioactive) waste.

Ruddy, F. H.; Dulloo, A. R.; Seidel, J. G.; Petrovi?, B.

2004-01-01

253

Effects of loss and dispersion on fiber-based quantum key distribution system  

Microsoft Academic Search

Studied are the effects of fiber dispersion and loss and single-photon detector dark counts on key transmission rate and bit error rate of quantum key distribution system through theoretical analysis and computation. Research demonstrates that fiber loss is the main factor that influences quantum key transmission rate, while quantum bit error rate is related to fiber loss, dispersion, pulse width,

Shu Yang; Wei Liu; Yu-hong Han; Bo-jun Yang

2008-01-01

254

Effect of the (OH) Surface Capping on ZnO Quantum Dots  

E-print Network

Effect of the (OH) Surface Capping on ZnO Quantum Dots H. Zhou1 ) (a), H. Alves (a), D. M. Hofmann; S10.1 ZnO quantum dots were prepared by the reaction of Zn2+ with OH­­ in alcoholic solution transition of ZnO quantum dots is strongly correlated with the presence of the surface (OH) groups

Nabben, Reinhard

255

Effective State Metamorphosis in Semi-Classical Loop Quantum Cosmology  

E-print Network

Modification to the behavior of geometrical density at short scales is a key result of loop quantum cosmology, responsible for an interesting phenomenology in the very early universe. We demonstrate the way a perfect fluid with arbitrary equation of state incorporates this change in its effective dynamics in the loop modified phase. We show that irrespective of the choice of matter component, stress-energy conservation law generically implies that classical equation of state metamorphoses itself to an effective negative equation of state below a critical scale determined by the theory.

Singh, P

2005-01-01

256

Quantum-Enhanced Thermoelectric Effects in Polycyclic Molecular Junctions  

NASA Astrophysics Data System (ADS)

We calculate the thermoelectric response of a polycyclic molecular junction including electron-electron interactions. To do this, the molecular Green's function is determined via a Lanczos-based technique and ?-electron effective field theory is used to model the degrees of freedom most relevant to transport. In these junctions we find that the presence of multiple rings leads to higher order quantum interference features giving rise to dramatic enhancements of molecular thermoelectric effects, consistent with previous predictions based on Hueckel theory, which neglected electron correlations.

Barr, Joshua; Stafford, Charles

2012-02-01

257

Novel quantum interference effects in transport through molecular radicals  

NASA Astrophysics Data System (ADS)

In molecules with an unpaired electron (radicals), we predict a correlation-induced `Mott-node' in the transmission spectrum arising from destructive interference between transport contributions from different charge states of the molecule. This class of quantum interference effect has no single-particle analog and cannot be described by effective single-particle theories. Large errors in the thermoelectric properties and nonlinear current-voltage response of molecular radical junctions are introduced when the complementary wave and particle aspects of the electron are not properly treated. A method to accurately calculate the low-energy transport through a radical-based junction using an Anderson model is given.

Bergfield, Justin; Solomon, Gemma; Stafford, Charles; Ratner, Mark

2012-02-01

258

Quantification of Left Ventricular Torsion and Diastolic Recoil Using Cardiovascular Magnetic Resonance Myocardial Feature Tracking  

PubMed Central

Objectives Cardiovascular magnetic resonance feature tracking (CMR-FT) offers quantification of myocardial deformation from routine cine images. However, data using CMR-FT to quantify left ventricular (LV) torsion and diastolic recoil are not yet available. We therefore sought to evaluate the feasibility and reproducibility of CMR-FT to quantify LV torsion and peak recoil rate using an optimal anatomical approach. Methods Short-axis cine stacks were acquired at rest and during dobutamine stimulation (10 and 20 gkg?1min?1) in 10 healthy volunteers. Rotational displacement was analysed for all slices. A complete 3D-LV rotational model was developed using linear interpolation between adjacent slices. Torsion was defined as the difference between apical and basal rotation, divided by slice distance. Depending on the distance between the most apical (defined as 0% LV distance) and basal (defined as 100% LV distance) slices, four different models for the calculation of torsion were examined: Model-1 (2575%), Model-2 (0100%), Model-3 (25100%) and Model-4 (075%). Analysis included subendocardial, subepicardial and global torsion and recoil rate (mean of subendocardial and subepicardial values). Results Quantification of torsion and recoil rate was feasible in all subjects. There was no significant difference between the different models at rest. However, only Model-1 (2575%) discriminated between rest and stress (Global Torsion: 2.71.5cm?1, 3.62.0cm?1, 5.12.2cm?1, p<0.01; Global Recoil Rate: ?30.111.1cm?1s?1,?46.915.0cm?1s?1,?68.932.3cm?1s?1, p<0.01; for rest, 10 and 20 gkg?1min?1 of dobutamine, respectively). Reproducibility was sufficient for all parameters as determined by Bland-Altman analysis, intraclass correlation coefficients and coefficient of variation. Conclusions CMR-FT based derivation of myocardial torsion and recoil rate is feasible and reproducible at rest and with dobutamine stress. Using an optimal anatomical approach measuring rotation at 25% and 75% apical and basal LV locations allows effective quantification of torsion and recoil dynamics. Application of these new measures of deformation by CMR-FT should next be explored in disease states. PMID:25285656

Hussain, Shazia T.; Kutty, Shelby; Steinmetz, Michael; Sohns, Jan M.; Fasshauer, Martin; Staab, Wieland; Unterberg-Buchwald, Christina; Bigalke, Boris; Lotz, Joachim; Hasenfuss, Gerd; Schuster, Andreas

2014-01-01

259

A time-asymmetric delta-kicked model for the quantum ratchet effect  

NASA Astrophysics Data System (ADS)

We investigate a time-asymmetric delta-kicked model for the quantum ratchet effect, in which a flashing potential acts on a particle at unequal time intervals. Ratchet currents emerge when quantum resonances are excited. The currents in time-asymmetric models may be stronger than those found in the previous time-symmetric model. Our work expands upon the quantum delta-kicked model and may contribute to experimental investigation of the quantum transport of cold atoms.

Chen, Lei; Xiong, Chao; Xiao, Jin; Yuan, Hong-Chun

2014-12-01

260

Quantum Hall effect on the Grassmannians Gr2(CN)  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

261

Possible Astrophysical Observables of Quantum Gravity Effects near Black Holes  

E-print Network

Recent implications of results from quantum information theory applied to black holes has led to the confusing conclusions that requires either abandoning the equivalence principle (e.g. the firewall picture), or the no-hair theorem (e.g. the fuzzball picture), 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. Pulsar radiation is 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 spacetime 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 BHC.

Ue-Li Pen

2013-12-14

262

Possible astrophysical observables of quantum gravity effects near black holes  

NASA Astrophysics Data System (ADS)

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.

Pen, Ue-Li; Broderick, Avery E.

2014-12-01

263

Possible quantum gravity effects on the gravitational deflection of light  

E-print Network

We investigate possible quantum gravity (QG) effects on the gravitational deflection of light. Two forms of deformation of the Schwarzschild spacetime are proposed. The first ansatz is a given Finslerian line element, it could be regarded as a weak QG effect on the Schwarzschild spacetime. Starting from this ansatz, we deduce the deflection angle of the light ray which passes a weak gravitational source. The second ansatz could be regarded as a strong QG effect on the Schwarzschild spacetime. The deflection angle of the light ray which passes a weak gravitational source is deduced in this Riemannian spacetime. This QG effect may distinguish the mixed light rays in the absence of gravitational source by a "spectroscope" (the gravitational source). The solutions of gravitational field equation in this Riemannian spacetime indicate that the QG effect could be regarded as the vacuum energy and the energy density of vacuum is related to the spacetime deformation parameter.

Xin Li; Zhe Chang

2010-07-02

264

Effects of intersubband interaction on multisubband electron transport in single and double quantum wells  

NASA Astrophysics Data System (ADS)

The multisubband electron transport properties are studied for doped single quantum well and gated double asymmetric quantum well structures. The effects due to intersubband interaction and screening of the ionized impurity scattering are also investigated. We show that intersubband coupling plays an essential role in describing the screening properties as well as the effect of ionized impurity scattering on the mobility in a doped single quantum well. For coupled double quantum well structures, negative transconductance is found theoretically which is due to resonant tunneling between the two quantum wells.

Hai, G.-Q.; Studart, N.; Marques, G. E.; Peeters, F. M.; Koenraad, P. M.

1998-07-01

265

Determining influence of four-wave mixing effect on quantum key distribution  

NASA Astrophysics Data System (ADS)

We consider the possibility of multiplexing the classical and quantum signals in a quantum cryptography system with optical fiber used as a transmission medium. If the quantum signal is located at a frequency close to the frequency of classical signals, a set of nonlinear effects such as FWM (four-wave mixing) and Raman scattering is observed. The impact of four-wave mixing (FWM) effect on error level is described and analyzed in this work in case of large frequency diversity between classical and quantum signals. It is shown that the influence of FWM is negligible for convenient quantum key distribution.

Vavulin, D. N.; Egorov, V. I.; Gleim, A. V.; Chivilikhin, S. A.

2014-10-01

266

Tunable interactions and the fractional quantum Hall effect  

NASA Astrophysics Data System (ADS)

We explore several realistic methods of tuning the interactions in two-dimensional electronic systems in high magnetic fields. We argue that these experimental probes can be useful in studying the interplay of topology, quantum geometry and symmetry breaking in the fractional quantum Hall effect (FQHE). In particular, we show that the mixing of subbands and Landau levels in GaAs wide quantum wells breaks the particle-hole symmetry between the Moore-Read Pfaffian state and its particle-hole conjugate, the anti-Pfaffian, in such a way that the latter is unambiguously favored and generically describes the ground state at 5/2 filling [1]. Furthermore, the tilting of the magnetic field, or more generally variation of the band mass tensor, probes the fluctuation of the intrinsic metric degree of freedom of the incompressible fluids, and ultimately induces the crossover to the broken-symmetry and nematic phases in higher Landau levels [2]. Some of these mechanisms also lead to an enhancement of the excitation gap of the non-Abelian states, as observed in recent experiments. Finally, we compare the tuning capabilities in conventional systems with that in multilayer graphene and related materials with Dirac-type carriers where tuning the band structure and dielectric environment provides a simple and direct method to engineer more robust FQHE states and to study quantum transitions between them [3]. [4pt] [1] Z. Papic, F. D. M. Haldane, and E. H. Rezayi, arXiv:1209.6606 (2012).[0pt] [2] Bo Yang, Z. Papic, E. H. Rezayi, R. N. Bhatt, F. D. M. Haldane, Phys. Rev. B 85, 165318 (2012).[0pt] [3] Z. Papic, R. Thomale, D. A. Abanin, Phys. Rev. Lett. 107, 176602 (2011); Z. Papic, D. A. Abanin, Y. Barlas, and R. N. Bhatt, Phys. Rev. B 84, 241306(R) (2011); D. A. Abanin, Z. Papic, Y. Barlas, and R. N. Bhatt, New J. Phys. 14, 025009 (2012).

Papic, Zlatko

2013-03-01

267

Scintillation of liquid helium for low-energy nuclear recoils  

NASA Astrophysics Data System (ADS)

The scintillation properties of liquid helium upon the recoil of a low-energy helium atom are discussed in the context of the possible use of this medium as a detector of dark matter. It is found that the prompt scintillation yield in the range of recoil energies from a few keV to 100 keV is somewhat higher than that obtained by a linear extrapolation from the measured yield for a 5-MeV ? particle. A comparison is made of both the scintillation yield and the charge separation by an electric field for nuclear recoils and for electrons stopped in helium.

Ito, T. M.; Seidel, G. M.

2013-08-01

268

Trapped-ion realization of Einstein's recoiling-slit experiment  

SciTech Connect

We analyze photon scattering by a harmonically trapped ion using two-port interferometry of the scattered photon and coherent-state measurement of the ion's external recoil motion. We examine how the coherent-state measurement could be used to mimick both momentum and position ion measurements and thus a modern realization of Wootters and Zurek's pioneering analysis of Einstein's historic recoiling-slit gedanken experiment. To quantify the photon-path which-port information cached in the recoiling ion and the underlying wave-particle duality, we evaluate the ion-state trace distance and distinguishability.

Utter, Robert S.; Feagin, James M. [Department of Physics, California State University-Fullerton, Fullerton, California 92834 (United States)

2007-06-15

269

On Quantum Coherence Effects in Photo and Solar Cells  

E-print Network

We show that quantum coherence can increase the quantum efficiency of various thermodynamic systems. For example, we can enhance the quantum efficiency for a quantum dot photocell, a laser based solar cell and the photo-Carnot quantum heat engine. Our results are fully consistent with the laws of thermodynamics contrary to comments found in the paper of A.P. Kirk, Phys. Rev. Lett. 106, 048703 (2011).

Kimberly Chapin; Konstantin Dorfman; Anatoly Svidzinsky; Marlan Scully

2010-12-23

270

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

SciTech Connect

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.

Rezende, Danilo Jimenez; Perez, Alejandro [Centre de Physique Theorique, Campus de Luminy, 13288 Marseille (France)

2008-10-15

271

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

NASA Astrophysics Data System (ADS)

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.

Zhang, Zi-Hui; Liu, Wei; Ju, Zhengang; Tiam Tan, Swee; Ji, Yun; Kyaw, Zabu; Zhang, Xueliang; Wang, Liancheng; Wei Sun, Xiao; Volkan Demir, Hilmi

2014-06-01

272

Effect of quantum nuclear motion on hydrogen bonding.  

PubMed

This work considers how the properties of hydrogen bonded complexes, X-H?Y, are modified by the quantum motion of the shared proton. Using a simple two-diabatic state model Hamiltonian, the analysis of the symmetric case, where the donor (X) and acceptor (Y) have the same proton affinity, is carried out. For quantitative comparisons, a parametrization specific to the O-H?O complexes is used. The vibrational energy levels of the one-dimensional ground state adiabatic potential of the model are used to make quantitative comparisons with a vast body of condensed phase data, spanning a donor-acceptor separation (R) range of about 2.4-3.0 , i.e., from strong to weak hydrogen bonds. The position of the proton (which determines the X-H bond length) and its longitudinal vibrational frequency, along with the isotope effects in both are described quantitatively. An analysis of the secondary geometric isotope effect, using a simple extension of the two-state model, yields an improved agreement of the predicted variation with R of frequency isotope effects. The role of bending modes is also considered: their quantum effects compete with those of the stretching mode for weak to moderate H-bond strengths. In spite of the economy in the parametrization of the model used, it offers key insights into the defining features of H-bonds, and semi-quantitatively captures several trends. PMID:24811647

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

2014-05-01

273

Effective interaction and condensation of dipolaritons in coupled quantum wells  

NASA Astrophysics Data System (ADS)

Dipolaritons are a three-way superposition of a photon, a direct exciton, and an indirect exciton that are formed in coupled quantum well microcavities. As is the case with exciton-polaritons, dipolaritons have a self-interaction due to direct and exchange effects of the underlying electrons and holes. Here we present a theoretical description of dipolaritons and derive simple formulas for their basic parameters. In particular, we derive the effective dipolariton-dipolariton interaction taking into account exchange effects between the excitons. We obtain a simple relation to describe the effective interaction at low densities. We find that dipolaritons should condense under suitable conditions, described by a dissipative Gross-Pitaevskii equation. While the parameters for condensation are promising, we find that the level of tunability of the interactions is limited.

Byrnes, Tim; Kolmakov, German V.; Kezerashvili, Roman Ya.; Yamamoto, Yoshihisa

2014-09-01

274

Toward realistic effective models of quantum-Hall edges  

NASA Astrophysics Data System (ADS)

We have investigated the dynamical properties of edge excitations in the (fractional) quantum-Hall regime for a sharp confining potential, emphasizing the effects resulting from the presence of long-range interaction. Our study uses chiral-Luttinger-liquid models that are motivated by the close analogy between the physics of edge excitations and that of plasmons in quasi-one-dimensional electron systems. We find that incorporating realistic long-range interaction is especially important for multi-branch edges. Results are presented for the tunneling-IV-curve power-law exponent and the two-terminal conductance.

Zlicke, U.; MacDonald, A. H.

1998-01-01

275

25 Years quantum Hall effect: how it all came about  

NASA Astrophysics Data System (ADS)

The quantum Hall effect (QHE) was discovered by Klaus von Klitzing in the spring of 1980. However, the plateaus in the Hall resistance of silicon metal oxide semiconductor devices which can be observed in high magnetic fields at low temperatures showed up several years earlier. The world wide research, which eventually culminated in the discovery, is briefly reviewed. The QHE was not predicted by theory, there were only approximate indications of quantization of the Hall resistance in whole fractions of h/ e2. The exceptional precision of the resistance values of the Hall plateau led very soon to a new resistance standard.

Landwehr, G.

2003-12-01

276

Scalar spin chirality and quantum hall effect on triangular lattices  

SciTech Connect

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

Martin, Ivar [Los Alamos National Laboratory; Batista, Cristian D [Los Alamos National Laboratory

2008-01-01

277

Role of Quantum Effects in the GlassTransition.  

SciTech Connect

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

Novikov, Vladimir [ORNL; Sokolov, Alexei P [ORNL

2013-01-01

278

Robustness of quantum spin Hall effect in an external magnetic field  

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

279

Quantum confinement in Si and Ge nanostructures: effect of crystallinity  

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

280

Hydride transfer catalyzed by xylose isomerase: mechanism and quantum effects.  

PubMed

We have applied molecular dynamics umbrella-sampling simulation and ensemble-averaged variational transition state theory with multidimensional tunneling (EA-VTST/MT) to calculate the reaction rate of xylose-to- xylulose isomerization catalyzed by xylose isomerase in the presence of two Mg2+ ions. The calculations include determination of the free energy of activation profile and ensemble averaging in the transmission coefficient. The potential energy function is approximated by a combined QM/MM/SVB method involving PM3 for the quantum mechanical (QM) subsystem, CHARMM22 and TIP3P for the molecular mechanical (MM) environment, and a simple valence bond (SVB) local function of two bond distances for the hydride transfer reaction. The simulation confirms the essential features of a mechanism postulated on the basis of kinetics and X-ray data by Whitlow et al. (Whitlow, M.; Howard, A. J.; Finzel, B. C.; Poulos, T. L.; Winborne, E.; Gilliland, G. L. Proteins 1991, 9, 153) and Ringe, Petsko, and coworkers (Labie, A.; Allen, K.-N.; Petsko, G. A.; Ringe, D. Biochemistry 1994, 33, 5469). This mechanism involves a rate-determining 1,2-hydride shift with prior and post proton transfers. Inclusion of quantum mechanical vibrational energy is important for computing the free energy of activation, and quantum mechanical tunneling effects are essential for computing kinetic isotope effects (KIEs). It is found that 85% of the reaction proceeds by tunneling and 15% by overbarrier events. The computed KIE for the ratio of hydride to deuteride transfer is in good agreement with the experimental results. The molecular dynamics simulations reveal that proton and hydride transfer reactions are assisted by breathing motions of the mobile Mg2+ ion in the active site, providing evidence for concerted motion of Mg2+ during the hydride transfer step. PMID:12497598

Garcia-Viloca, Mireia; Alhambra, Cristbal; Truhlar, Donald G; Gao, Jiali

2003-01-30

281

Observing the Quantum Spin Hall Effect with Ultracold Atoms  

NASA Astrophysics Data System (ADS)

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.

Vaishnav, J. Y.; Stanescu, Tudor D.; Clark, Charles W.; Galitski, Victor

2009-03-01

282

Semianalytical quantum model for graphene field-effect transistors  

NASA Astrophysics Data System (ADS)

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.

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

2014-09-01

283

The Casimir effect: from quantum to critical fluctuations  

E-print Network

The Casimir effect in quantum electrodynamics (QED) is perhaps the best-known example of fluctuation-induced long-ranged force acting on objects (conducting plates) immersed in a fluctuating medium (quantum electromagnetic field in vacuum). A similar effect emerges in statistical physics, where the force acting, e.g., on colloidal particles immersed in a binary liquid mixture is affected by the classical thermal fluctuations occurring in the surrounding medium. The resulting Casimir-like force acquires universal features upon approaching a critical point of the medium and becomes long-ranged at criticality. In turn, this universality allows one to investigate theoretically the temperature dependence of the force via representative models and to stringently test the corresponding predictions in experiments. In contrast to QED, the Casimir force resulting from critical fluctuations can be easily tuned with respect to strength and sign by surface treatments and temperature control. We present some recent advances in the theoretical study of the universal properties of the critical Casimir force arising in thin films. The corresponding predictions compare very well with the experimental results obtained for wetting layers of various fluids. We discuss how the Casimir force between a colloidal particle and a planar wall immersed in a binary liquid mixture has been measured with femto-Newton accuracy, comparing these experimental results with the corresponding theoretical predictions.

Andrea Gambassi

2008-12-04

284

Electron-recoil ion and recoil ion-projectile coincidence techniques applied to obtain absolute partial collision cross sections  

NASA Astrophysics Data System (ADS)

We present in detail an alternative experimental set-up and data analysis, based on the electron-recoil ion and recoil ion-projectile coincidence techniques, that enable the measurement of partial pure ionization and partial charge exchange cross sections for an effusive gas jet set-up, where the absolute target density and recoil ion efficiency cannot be measured directly. The method is applied to the ionization of helium atoms due to collision with partially stripped C3 + projectiles. In order to check the method, the results are compared to data available in the literature where the target density and recoil ion detection efficiency were measured directly. The pure ionization channel is compared to the electron capture channel.

Wolff, W.; de Souza, Ihani J.; Tavares, Andr C.; de Oliveira, G. F. S.; Luna, H.

2012-12-01

285

Gamma-ray free-electron lasers: Quantum fluid model  

E-print Network

A quantum fluid model is used to describe the interacion of a nondegenerate cold relativistic electron beam with an intense optical wiggler taking into account the beam space-charge potential and photon recoil effect. A nonlinear set of coupled equations are obtained and solved numerically. The numerical results shows that in the limit of plasma wave-breaking an ultra-high power radiation pulse are emitted at the$\\gamma$-ray wavelength range which can reach an output intensity near the Schwinger limit depending of the values of the FEL parameters such as detuning and input signal initial phase at the entrance of the interaction region.

Silva, H M

2014-01-01

286

Loop Quantum effects on Om-diagnostic and its Cosmological Implications  

E-print Network

In this paper we study the Loop quantum effects on the \\textit{Om} diagnostic and subsequently on the universe. We reconstruct the \\textit{Om} diagnostic in the background of Loop quantum gravity and then study the behaviour of various Chaplygin gas dark energy models using the modified diagnostic in a comparative scenario. The trajectories discriminate the various dark energy models from each other both in the Einstein gravity as well as Loop quantum gravity. The Loop quantum effects are also clearly noticeable from the trajectories in past, present and future universe. We see that the Loop quantum deviations are highly pronounced in the early universe, but alleviates as we tend towards the present universe and continue to decay in future. Thus it puts a big question on the effectiveness and consequently the suitability of loop quantum cosmology to explain the future universe.

Rudra, Prabir

2014-01-01

287

Quantum Effects in the Diffusion of Hydrogen on Ru(0001)  

PubMed Central

An understanding of hydrogen diffusion on metal surfaces is important not only for its role in heterogeneous catalysis and hydrogen fuel cell technology but also because it provides model systems where tunneling can be studied under well-defined conditions. Here we report helium spinecho measurements of the atomic-scale motion of hydrogen on the Ru(0001) surface between 75 and 250 K. Quantum effects are evident at temperatures as high as 200 K, while below 120 K we observe a tunneling-dominated temperature-independent jump rate of 1.9 109 s1, many orders of magnitude faster than previously seen. Quantum transition-state theory calculations based on ab initio path-integral simulations reproduce the temperature dependence of the rate at higher temperatures and predict a crossover to tunneling-dominated diffusion at low temperatures. However, the tunneling rate is underestimated, highlighting the need for future experimental and theoretical studies of hydrogen diffusion on this and other well-defined surfaces. PMID:24920996

2013-01-01

288

Quantum effects in the diffusion of hydrogen on Ru(0001)  

E-print Network

An understanding of hydrogen diffusion on metal surfaces is important, not just 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$\\times$10$^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, although the tunneling rate is under-estimated, highlighting the need for future experimental and theoretical studies of hydrogen diffusion on well-defined surfac...

McIntosh, Eliza M; Ellis, John; Michaelides, Angelos; Allison, William

2014-01-01

289

Band Collapse and the Quantum Hall Effect in Graphene  

SciTech Connect

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.

Bernevig, B.Andrei; Hughes, Taylor L.; Zhang, Shou-Cheng; /Stanford U., Phys. Dept.; Chen, Han-Dong; /Illinois U., Urbana; Wu, Congjun; /Santa Barbara, KITP

2010-03-16

290

Quantum cutting effect in KY3F10:Tm3+  

NASA Astrophysics Data System (ADS)

A cross-relaxation energy-transfer scheme using the 5d state of Tm3+ as the donor and the 4f13 states of Tm3+ as the acceptor is proposed. The scheme is tested in the host KY3F10 doped with several concentrations of Tm3+ as a potential vacuum ultraviolet (VUV) excited blue phosphor of quantum yield greater than unity. Emission and diffuse reflection spectra along with studies of the time evolution of the 5d and 4f populations of Tm3+ in KY3F10 crystals and powders under UV and VUV excitations are reported and analyzed. The results show that the proposed quantum cutting mechanism occurs but the I16 , D12 , and G14 acceptor levels cross relax rapidly to lower-lying levels by an additional cross-relaxation energy transfer and that this effectively quenches the blue emission. Based on the temperature dependence of the spectra, an interesting heat-assisted relaxation process involving intersystem crossing is observed above 300 K.

Beauzamy, Lna; Moine, Bernard; Meltzer, Richard S.; Zhou, Yi; Gredin, Patrick; Jouini, Anis; Kim, Kyoung Jin

2008-11-01

291

Quantum Stress Tensor Fluctuations and their Physical Effects  

E-print Network

We summarize several aspects of recent work on quantum stress tensor fluctuations and their role in driving fluctuations of the gravitational field. The role of correlations and anticorrelations is emphasized. We begin with a review of the properties of the stress tensor correlation function. We next consider some illuminating examples of non-gravitational effects of stress tensors fluctuations, specifically fluctuations of the Casimir force and radiation pressure fluctuations. We next discuss passive fluctuations of spacetime geometry and some of their operational signatures. These include luminosity fluctuations, line broadening, and angular blurring of a source viewed through a fluctuating gravitational field. Finally, we discuss the possible role of quantum stress tensor fluctuations in the early universe, especially in inflation. The fluctuations of the expansion of a congruence of comoving geodesics grows during the inflationary era, due to non-cancellation of anticorrelations that would have occurred in flat spacetime. This results in subsequent non-Gaussian density perturbations and allows one to infer an upper bound on the duration of inflation. This bound is consistent with adequate inflation to solve the horizon and flatness problems.

L. H. Ford; Chun-Hsien Wu

2007-10-19

292

A Predictive Theory for Elastic Scattering and Recoil of Protons from $^4$He  

E-print Network

Low-energy cross sections for elastic scattering and recoil of protons from $^4$He nuclei (also known as $\\alpha$ particles) are calculated directly by solving the Schr\\"odinger 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 concentrations and depth profiles of either hydrogen or helium. We compare our results to available experimental data and show that direct calculations with modern nuclear potentials can help to resolve remaining inconsistencies among different data sets and can be used to predict these cross sections when measurements are not available.

Guillaume Hupin; Sofia Quaglioni; Petr Navrtil

2014-09-02

293

A Predictive Theory for Elastic Scattering and Recoil of Protons from $^4$He  

E-print Network

Low-energy cross sections for elastic scattering and recoil of protons from $^4$He nuclei (also known as $\\alpha$ particles) are calculated directly by solving the Schr\\"odinger 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 concentrations and depth profiles of either hydrogen or helium. We compare our results to available experimental data and show that direct calculations with modern nuclear potentials can help to resolve remaining inconsistencies among different data sets and can be used to predict these cross sections when measurements are not available.

Hupin, Guillaume; Navrtil, Petr

2014-01-01

294

Classical Limit of the Quantum Zeno Effect by Environmental Decoherence  

E-print Network

We consider a point particle in one dimension initially confined to a finite spatial region whose state is frequently monitored by projection operators onto that region. In the limit of infinitely frequent monitoring, the state never escapes from the region -- this is the Zeno effect. The aim of this paper is to show how the Zeno effect disappears in the classical limit in this and similar examples. We give a general argument showing that the Zeno effect is suppressed in the presence of a decoherence mechanism which kills interference between histories. We show how this works explicitly by coupling to a decohering environment. Smoothed projectors are required to give the problem proper definition and this implies the existence of a momentum cutoff. We show that the escape rate from the region approaches the classically expected result, and hence the Zeno effect is suppressed, as long as the environmentally-induced fluctuations in momentum are sufficiently large and we establish the associated timescale. We link our results to earlier work on the hbar -->0 limit of the Zeno effect. We illustrate our results by plotting the probability flux lines for the density matrix (which are equivalent to Bohm trajectories in the pure state case). These illustrate both the Zeno and anti-Zeno effects very clearly, and their suppression. Our results are closely related to our earlier paper demonstrating the suppression of quantum-mechanical reflection by decoherence

D. J. Bedingham; J. J. Halliwell

2014-02-18

295

Quantum Anomalous Hall Effect and Tunable Topological States in 3d  

E-print Network

Quantum Anomalous Hall Effect and Tunable Topological States in 3d Transition Metals Doped Silicene decorated with certain 3d transition metals (Vanadium) can sustain a stable quantum anomalous Hall effect as half of TIs. Since TIs have been fabricated in materials ranging from 2D17 to 3D18 , engineering

Wang, Wei Hua

296

Experimental Studies of the Fractional Quantum Hall Effect: High Field-Low Temperature Studies  

E-print Network

Experimental Studies of the Fractional Quantum Hall Effect: High Field-Low Temperature Studies of Florida Measurements at very low electron temperatures of the fractional quantum Hall effect in high only in very high quality samples and requires extremely low temperatures (

Weston, Ken

297

Underscreened Kondo effect in S=1 magnetic quantum dots: Exchange, anisotropy, and temperature effects  

NASA Astrophysics Data System (ADS)

We present a theoretical analysis of the effects of uniaxial magnetic anisotropy and contact-induced exchange field on the underscreened Kondo effect in S=1 magnetic quantum dots coupled to ferromagnetic leads. First, by using the second-order perturbation theory we show that the coupling to spin-polarized electrode results in an effective exchange field Beff and an effective magnetic anisotropy Deff. Second, we confirm these findings by using the numerical renormalization group method, which is employed to study the dependence of the quantum-dot spectral functions, as well as quantum-dot spin, on various parameters of the system. We show that the underscreened Kondo effect is generally suppressed due to the presence of effective exchange field and can be restored by tuning the anisotropy constant, when |Deff|=|Beff|. The Kondo effect can also be restored by sweeping an external magnetic field, and the restoration occurs twice in a single sweep. From the distance between the restored Kondo resonances one can extract the information about both the exchange field and the effective anisotropy. Finally, we calculate the temperature dependence of linear conductance for the parameters where the Kondo effect is restored and show that the restored Kondo resonances display a universal scaling of S=1/2 Kondo effect.

Misiorny, Maciej; Weymann, Ireneusz; Barna?, Jzef

2012-12-01

298

Decoherence Effect on Quantum Correlation and Entanglement in a Two-qubit Spin Chain  

NASA Astrophysics Data System (ADS)

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.

Pourkarimi, Mohammad Reza; Rahnama, Majid; Rooholamini, Hossein

2014-08-01

299

Group velocity of extraordinary waves in superdense magnetized quantum plasma with spin-1/2 effects  

SciTech Connect

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.

Li Chunhua; Ren Haijun; Yang Weihong [Department of Modern Physics, University of Science and Technology of China, 230026 Hefei (China); Wu Zhengwei [Department of Modern Physics, University of Science and Technology of China, 230026 Hefei (China); Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon (Hong Kong); Chu, Paul K. [Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon (Hong Kong)

2012-12-15

300

Spin effects on the instability and propagation modes of electrostatic plasma waves in quantum plasmas  

SciTech Connect

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.

Ki, Dae-Han; Jung, Young-Dae [Department of Applied Physics, Hanyang University, Ansan, Kyunggi-Do 426-791 (Korea, Republic of)

2011-09-19

301

Decoherence effect on quantum correlation and entanglement in a two-qubit spin chain  

E-print Network

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.

Mohammad Reza Pourkarimi; Majid Rahnama; Hossein Rooholamini

2012-11-26

302

Performance of a two-state quantum engine improved by the superposition effect  

NASA Astrophysics Data System (ADS)

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.

Ou, CongJie; Huang, ZhiFu; Lin, BiHong; Chen, JinCan

2013-10-01

303

Quantum fluctuations and isotope effects in ab initio descriptions of water  

E-print Network

Nuclear quantum effects, such as zero-point energy and tunneling, cause significant changes to the structure and dynamics of hydrogen bonded systems such as liquid water. However, due to the current inability to simulate liquid water using an exact description of its electronic structure, the interplay between nuclear and electronic quantum effects remains unclear. Here we use simulations that incorporate the quantum mechanical nature of both the nuclei and electrons to provide a fully ab initio determination of the particle quantum kinetic energies, free energy change upon exchanging hydrogen for deuterium and the isotope fractionation ratio in water. These properties, which selectively probe the quantum nature of the nuclear degrees of freedom, allow us to make direct comparison to recent experiments and elucidate how electronic exchange and correlation and nuclear quantum fluctuations determine the structure of the hydrogen bond in water.

Lu Wang; Michele Ceriotti; Thomas E. Markland

2014-05-28

304

Fractional quantum Hall effect in a dilute magnetic semiconductor  

NASA Astrophysics Data System (ADS)

We report the observation of the fractional quantum Hall effect in the lowest Landau level of a two-dimensional electron system (2DES), residing in the diluted magnetic semiconductor Cd1-xMnxTe. The presence of magnetic impurities results in a giant Zeeman splitting leading to an unusual ordering of composite fermion Landau levels. In experiment, this results in an unconventional opening and closing of fractional gaps around the filling factor ? =3/2 as a function of an in-plane magnetic field, i.e., of the Zeeman energy. By including the s-d exchange energy into the composite Landau level spectrum the opening and closing of the gap at filling factor 5/3 can be modeled quantitatively. The widely tunable spin-splitting in a diluted magnetic 2DES provides a means to manipulate fractional states.

Betthausen, C.; Giudici, P.; Iankilevitch, A.; Preis, C.; Kolkovsky, V.; Wiater, M.; Karczewski, G.; Piot, B. A.; Kunc, J.; Potemski, M.; Wojtowicz, T.; Weiss, D.

2014-09-01

305

Admittance measurements in the quantum Hall effect regime  

NASA Astrophysics Data System (ADS)

In this work we present an admittance study of a two-dimensional electron gas (2DEG) in the quantum Hall effect (QHE) regime. We have studied several Hall bars in different contacts configurations in the frequency range 100 Hz-1 MHz. Our interpretation is based on the Landauer-Bttiker theory and takes into account both the capacitance and the topology of the coaxial cables which are connected to the sample holder. We show that we always observe losses through the capacitive impedance of the coaxial cables, except in the two contacts configuration in which the cable capacitance does not influence the admittance measurement of the sample. In this case, we measure the electrochemical capacitance of the 2DEG and show its dependence with the filling factor ?.

Hernndez, C.; Consejo, C.; Chaubet, C.

2014-11-01

306

Aharonov-Casher effect in quantum ring ensembles  

NASA Astrophysics Data System (ADS)

We study the transport of electrons through a single-mode quantum ring with electric-field induced Rashba spin-orbit interaction that is subject to an in-plane magnetic field and weakly coupled to electron reservoirs. Modeling a ring array by ensemble averaging over a Gaussian distribution of energy-level positions, we predict slow conductance oscillations as a function of the Rashba interaction and electron density due to spin-orbit interaction induced beating of the spacings between the levels crossed by the Fermi energy. Our results agree with experiments by Nitta c.s. [J. Nitta, J. Takagi, F. Nagasawa, and M. Kohda, J. Phys.: Conference Series1742-659610.1088/1742-6596/302/1/012002 302, 012002 (2011) and Nagasawa (unpublished)], thereby providing an interpretation that differs from the ordinary Aharonov-Casher effect in a single ring.

Joibari, Fateme K.; Blanter, Ya. M.; Bauer, Gerrit E. W.

2013-09-01

307

Magnetic quantum coherence effect in Ni4 molecular transistors.  

PubMed

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

Gonzlez, Gabriel; Leuenberger, Michael N

2014-07-01

308

Effective interactions and large-scale diagonalization for quantum dots  

E-print Network

The widely used large-scale diagonalization method using harmonic oscillator basis functions (an instance of the Rayleigh-Ritz method, also called a spectral method, configuration-interaction method, or ``exact diagonalization'' method) is systematically analyzed using results for the convergence of Hermite function series. We apply this theory to a Hamiltonian for a one-dimensional model of a quantum dot. The method is shown to converge slowly, and the non-smooth character of the interaction potential is identified as the main problem with the chosen basis, while on the other hand its important advantages are pointed out. An effective interaction obtained by a similarity transformation is proposed for improving the convergence of the diagonalization scheme, and numerical experiments are performed to demonstrate the improvement. Generalizations to more particles and dimensions are discussed.

Simen Kvaal; Morten Hjorth-Jensen; Halvor Moll Nilsen

2007-04-19

309

High-Current Breakdown of the Quantum Hall Effect  

NASA Astrophysics Data System (ADS)

We have recently developed a model for the high-current breakdown of the integer quantum Hall effect, as measured in contactless experiments using a highly-sensitive torsion balance magnetometer. The model predicted that, for low-mobility samples, the critical current for breakdown should decrease linearly with temperature. This prediction was verified experimentally with the addition of a low-temperature (? 300 mK) saturation of the critical current. This saturation is consistent with quasi-elastic inter-Landau-level scattering when the maximum electric field in the sample reaches a large enough value. In this paper we extend this model to nearly integer filling factors to show how the model may account for the shape of the magnetisation signal.

Matthews, A. J.; Kavokin, K. V.; Usher, A.; Portnoi, M. E.; Gething, J. D.; Zhu, M.; Ritchie, D. A.

2005-04-01

310

High-Current Breakdown of the Quantum Hall Effect  

NASA Astrophysics Data System (ADS)

We have recently developed a model for the high-current breakdown of the integer quantum Hall effect, as measured in contactless experiments using a highly-sensitive torsion balance magnetometer. The model predicted that, for low-mobility samples, the critical current for breakdown should decrease linearly with temperature. This prediction was verified experimentally with the addition of a low-temperature (? 300 mK) saturation of the critical current. This saturation is consistent with quasi-elastic inter-Landau-level scattering when the maximum electric field in the sample reaches a large enough value. In this paper we extend this model to nearly integer filling factors to show how the model may account for the shape of the magnetisation signal.

Matthews, A. J.; Kavokin, K. V.; Usher, A.; Portnoi, M. E.; Gething, J. D.; Zhu, M.; Ritchie, D. A.

311

High-Current Breakdown of the Quantum Hall Effect  

NASA Astrophysics Data System (ADS)

We have recently developed a model for the high-current breakdown of the integer quantum Hall effect, as measured in contactless experiments using a highly-sensitive torsion balance magnetometer. The model predicts that, for low-mobility samples, the critical current for breakdown should decrease linearly with temperature. This prediction is verified experimentally with the addition of a low-temperature (< 300 mK) saturation of the critical current. This saturation is consistent with quasi-elastic inter-Landau-level scattering when the maximum electric field in the sample reaches a large enough value. Here we extend this model to `nearly' integer filling factors to show how the model may account for the shape of the magnetisation signal.

Matthews, A. J.; Kavokin, K. V.; Usher, A.; Portnoi, M. E.; Gething, J. D.; Zhu, M.; Ritchie, D. A.

2005-06-01

312

Spin quantum Hall effects in featureless nonfractionalized spin-1 magnets  

NASA Astrophysics Data System (ADS)

The Affleck-Kennedy-Lieb-Tasaki state (or Haldane phase) in a spin-1 chain represents a large class of gapped topological paramagnets that host symmetry-protected gapless excitations on the boundary. In this work, we show how to realize this type of featureless spin-1 state on a generic two-dimensional lattice. These states have a gapped spectrum in the bulk, but they support gapless edge states protected by spin rotational symmetry along a certain direction, and they exhibit the spin quantum Hall effect. Using a fermion representation of integer spins, we show a concrete example of such spin-1 topological paramagnets on a kagome lattice, and we suggest a microscopic spin-1 Hamiltonian that may realize it.

Lu, Yuan-Ming; Lee, Dung-Hai

2014-05-01

313

Gate-induced carrier delocalization in quantum dot field effect transistors.  

PubMed

We study gate-controlled, low-temperature resistance and magnetotransport in indium-doped CdSe quantum dot field effect transistors. We show that using the gate to accumulate electrons in the quantum dot channel increases the "localization product" (localization length times dielectric constant) describing transport at the Fermi level, as expected for Fermi level changes near a mobility edge. Our measurements suggest that the localization length increases to significantly greater than the quantum dot diameter. PMID:25171186

Turk, Michael E; Choi, Ji-Hyuk; Oh, Soong Ju; Fafarman, Aaron T; Diroll, Benjamin T; Murray, Christopher B; Kagan, Cherie R; Kikkawa, James M

2014-10-01

314

Calculation of recoil implantation profiles using known range statistics  

NASA Technical Reports Server (NTRS)

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.

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

1985-01-01

315

SIMULATIONS OF RECOILING MASSIVE BLACK HOLES IN THE VIA LACTEA HALO  

SciTech Connect

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

Guedes, J.; Madau, P.; Diemand, J. [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Kuhlen, M. [Institute for Advanced Study, Einstein Drive, Princeton, NJ 08540 (United States); Zemp, M. [Astronomy Department, University of Michigan, Ann Arbor, MI 48109 (United States)

2009-09-10

316

Recoil polarization observables in the electroproduction of K mesons and ?'s from the proton  

NASA Astrophysics Data System (ADS)

A model developed previously to investigate the electromagnetic production of strangeness from the proton is used to investigate single and double recoil polarization observables in the reaction ep ?e'K+? in the relativistic impulse approximation. The formalism is based on a tree-level, effective Lagrangian model, which incorporates a variety of baryon resonances with spins up to 5/2 and the two kaon resonances, K(892) and K1(1270). The parameters of the model were fit to a large pool of photoproduction data from the CLAS, GRAAL, SAPHIR, and LEPS collaborations and to CLAS data for the virtual photoproduction structure functions ?U,?T,?L,?TT,?LT, and ?LT'. Using two different versions of this model, results are presented for three recoil polarization asymmetries that have been measured recently at CLAS. A new fit is then presented which incorporates the new polarization data in the fitted data set. Results obtained with this new fit are presented for six recoil polarization asymmetries and compared with results from one of the previous fits.

Maxwell, Oren V.

2014-09-01

317

Quenching Factor for Low Energy Nuclear Recoils in a Plastic Scintillator  

E-print Network

Plastic scintillators are widely used in industry, medicine and scientific research, including nuclear and particle physics. Although one of their most common applications is in neutron detection, experimental data on their response to low-energy nuclear recoils are scarce. Here, the relative scintillation efficiency for neutron-induced nuclear recoils in a polystyrene-based plastic scintillator (UPS-923A) is presented, exploring recoil energies between 125 keV and 850 keV. Monte Carlo simulations, incorporating light collection efficiency and energy resolution effects, are used to generate neutron scattering spectra which are matched to observed distributions of scintillation signals to parameterise the energy-dependent quenching factor. At energies above 300 keV the dependence is reasonably described using the semi-empirical formulation of Birks and a kB factor of (0.014+/-0.002) g/MeVcm^2 has been determined. Below that energy the measured quenching factor falls more steeply than predicted by the Birks formalism.

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

2011-11-09

318

Ground-state cooling of a trapped ion by quantum interference pathways  

NASA Astrophysics Data System (ADS)

We investigate the possibility of enhancement of cooling a trapped ion by combining the electromagnetically induced transparency (EIT) effect with the standing-wave coupling. Our study shows that the quantum destructive interference which is caused by the EIT effect and the standing-wave coupling can cancel all the dominant heating effects if appropriate parameters are chosen. The analytical predictions and numerical simulations show that the final temperature can be much lower than the recoil energy. In addition, this fast-cooling scheme is robust against fluctuations of the strength of the laser beams, which makes it more feasible for experimental realization.

Zhang, Shuo; Zhang, Jian-Qi; Duan, Qian-Heng; Guo, Chu; Wu, Chun-Wang; Wu, Wei; Chen, Ping-Xing

2014-10-01

319

Comment on "Non-monotonicity in the Quantum-Classical Transition: Chaos Induced by Quantum Effects"  

E-print Network

In a recent Letter [PRL 101, 074101 (2008)], Kapulkin and Pattanayak presented evidence that a quantum Duffing oscillator, sufficiently damped so that it is not classically chaotic, becomes chaotic in the transition region between quantum and classical motion. If true, this would be a striking result. However, Kapulkin and Pattanayak did not calculate the Lyapunov exponent for the system, usually regarded as the litmus-test of chaos. Here we perform this calculation, which throws considerable doubt upon their conclusions.

Justin Finn; Kurt Jacobs; Bala Sundaram

2009-03-19

320

Numerical simulations of a loop quantum cosmos: robustness of the quantum bounce and the validity of effective dynamics  

E-print Network

A key result of isotropic loop quantum cosmology is the existence of a quantum bounce which occurs when the energy density of the matter field approaches a universal maximum close to the Planck density. Though the bounce has been exhibited in various matter models, due to severe computational challenges some important questions have so far remained unaddressed. These include the demonstration of the bounce for widely spread states, its detailed properties for the states when matter field probes regions close to the Planck volume and the reliability of the continuum effective spacetime description in general. In this manuscript we rigorously answer these questions using the Chimera numerical scheme for the isotropic spatially flat model sourced with a massless scalar field. We show that as expected from an exactly solvable model, the quantum bounce is a generic feature of states even with a very wide spread, and for those which bounce much closer to the Planck volume. We perform a detailed analysis of the departures from the effective description and find some expected, and some surprising results. At a coarse level of description, the effective dynamics can be regarded as a good approximation to the underlying quantum dynamics unless the states correspond to small scalar field momenta, in which case they bounce closer to the Planck volume, or are very widely spread. Quantifying the amount of discrepancy between the quantum and the effective dynamics, we find that the departure between them depends in a subtle and non-monotonic way on the field momentum and different fluctuations. Interestingly, the departures are generically found to be such that the effective dynamics overestimates the spacetime curvature, and underestimates the volume at the bounce.

Peter Diener; Brajesh Gupt; Parampreet Singh

2014-02-26

321

Numerical simulations of a loop quantum cosmos: robustness of the quantum bounce and the validity of effective dynamics  

NASA Astrophysics Data System (ADS)

A key result of isotropic loop quantum cosmology is the existence of a quantum bounce which occurs when the energy density of the matter field approaches a universal maximum close to the Planck density. Though the bounce has been exhibited in various matter models, due to severe computational challenges, some important questions have so far remained unaddressed. These include the demonstration of the bounce for widely spread states, its detailed properties for the states when matter field probes regions close to the Planck volume and the reliability of the continuum effective spacetime description in general. In this manuscript we rigorously answer these questions using the Chimera numerical scheme for the isotropic spatially flat model sourced with a massless scalar field. We show that, as expected from an exactly solvable model, the quantum bounce is a generic feature of states even with a very wide spread, and for those which bounce much closer to the Planck volume. We perform a detailed analysis of the departures from the effective description and find some expected, and some surprising results. At a coarse level of description, the effective dynamics can be regarded as a good approximation to the underlying quantum dynamics unless the states correspond to small scalar field momenta, in which case they bounce closer to the Planck volume or are very widely spread. Quantifying the amount of discrepancy between the quantum and the effective dynamics, we find that the departure between them depends in a subtle and non-monotonic way on the field momentum and different fluctuations. Interestingly, the departures are generically found to be such that the effective dynamics overestimates the spacetime curvature, and underestimates the volume at the bounce.

Diener, Peter; Gupt, Brajesh; Singh, Parampreet

2014-05-01

322

Ab initio molecular dynamics simulations of overlapping recoil events in ThO2  

NASA Astrophysics Data System (ADS)

Ab initio molecular dynamics is used to study defect production and interactions from overlapping atomic recoil events in thoria. The pre-existing defects, charge redistribution, and structural distortion from an initial recoil event significantly affect the dynamics of defect production processes that occur from a subsequent overlapping recoil event. The final defect configurations and increase in system energy are dependent on the incident directions and sequence of the recoils. A linear relationship between system potential energy and charge transfer at the distance of closest approach between the recoil and atomic nuclei demonstrates the important role of charge transfer in the response of thoria to single and overlapping recoils.

Liu, B.; Xiao, H. Y.; Zhang, Y.; Weber, W. J.

2013-10-01

323

Non-abelian fractional quantum hall effect for fault-resistant topological quantum computation.  

SciTech Connect

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.

Pan, Wei; Thalakulam, Madhu; Shi, Xiaoyan; Crawford, Matthew; Nielsen, Erik; Cederberg, Jeffrey George

2013-10-01

324

Landau damping and the onset of particle trapping in quantum plasmas  

NASA Astrophysics Data System (ADS)

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 tB(k)=?m /eEk of a trapped electron and the quantum time scale tq(k)=2m /?k2 related to recoil effect, where E and k are the wave amplitude and wave vector. In the classical-like regime, tB(k) < tq(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, tB(k) > tq(k), particle trapping is hampered by the finite recoil imparted to resonant electrons in their interactions with plasmons.

Daligault, Jrme

2014-04-01

325

Quantum-dot gain without inversion: Effects of dark plasmon-exciton hybridization  

NASA Astrophysics Data System (ADS)

We propose an initial-state-dependent quantum-dot gain without population inversion in the vicinity of a resonant metallic nanoparticle. The gain originates from the hybridization of a dark plasmon-exciton and is accompanied by efficient energy transfer from the nanoparticle to the quantum dot. This hybridization of the dark plasmon-exciton, attached to the hybridization of the bright plasmon-exciton, strengthens nonlinear light-quantum emitter interactions at the nanoscale, thus the spectral overlap between the dark and the bright plasmons enhances the gain effect. This hybrid system has potential applications in ultracompact tunable quantum devices.

Zhao, Dongxing; Gu, Ying; Wu, Jiarui; Zhang, Junxiang; Zhang, Tiancai; Gerardot, Brian D.; Gong, Qihuang

2014-06-01

326

Non-equilibrium effects upon the non-Markovian Caldeira-Leggett quantum master equation  

SciTech Connect

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.

Bolivar, A.O., E-mail: bolivar@cbpf.br [Departamento de Fisica, Universidade Federal de Minas Gerais, Caixa Postal 702, 30123-970 Belo Horizonte, Minas Gerais (Brazil)

2011-05-15

327

Study of impurity position effect in pyramid and cone like quantum dots  

NASA Astrophysics Data System (ADS)

In the present work, we have studied the effect of impurity position on energy levels, the donor binding energy and third harmonic generation of a pyramid and a cone like quantum dot. For this goal, we have calculated the energy levels, wave functions and binding energy using finite element method for various impurity positions. Our results show that the impurity location plays an important and considerable role in the electronic and optical properties in a pyramid and a cone like quantum dot. We found that the third harmonic generation and binding energy of both quantum dots have a maximum value at a special impurity position. The special impurity location is different for the two quantum dots. Also, we have deduced that the third harmonic generation of a cone like quantum dot is larger than a pyramid quantum dot for same volumes and heights.

Khordad, Reza; Bahramiyan, Hossein

2014-08-01

328

Quantum Computer Games: Quantum Minesweeper  

ERIC Educational Resources Information Center

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

Gordon, Michal; Gordon, Goren

2010-01-01

329

Effect of quantum nuclear motion on hydrogen bonding  

E-print Network

This work considers how the properties of hydrogen bonded complexes, D-H....A, 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 (D) and acceptor (A) 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 A, i.e., from strong to weak bonds. The position of the proton and its longitudinal vibrational frequency, along with the isotope effects in both are discussed. An analysis of the secondary geometric isotope effects, 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 the b...

McKenzie, Ross H; Athokpam, Bijyalaxmi; Ramesh, Sai G

2014-01-01

330

Elementary framework for cold field emission: Incorporation of quantum-confinement effects  

SciTech Connect

Although the Fowler-Nordheim (FN) equation serves as the foundation of cold field emission theory, it may not be suitable for predicting the emitted current density (ECD) from emitters with a quantum-confined electron supply. This work presents an analytical framework for treating cold field emission from metals that includes the effects of a quantum-confined electron supply. Within the framework, quantum confinement in emitters is classified into transverse and normal quantum confinement based on the orientation of the confinement relative to the emission direction. The framework is used to generate equations predicting the ECD from rectangular and cylindrical emitter geometries comprised of electron supplies of reduced dimensionality. Transverse quantum confinement of the electron supply leads to a reduction in the total ECD as transverse emitter dimensions decrease and normal quantum confinement results in an oscillatory ECD as a function of the normal quantum well width. Incorporating a geometry-dependent field enhancement factor into the model reveals an optimal transverse well width for which quantum confinement of the electron supply and field enhancement equally affect the ECD and a maximum total ECD for the emitter geometry at a given applied field is obtained. As a result, the FN equation over-predicts the ECD from emitters with transverse dimensions under approximately 5?nm, and in those cases, geometry-specific ECD equations incorporating quantum-confinement effects should be employed instead.

Patterson, A. A., E-mail: apatters@mit.edu; Akinwande, A. I. [Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Microsystems Technology Laboratories, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

2013-12-21

331

Photonic realization of nonlocal memory effects and non-Markovian quantum probes  

PubMed Central

The study of open quantum systems is important for fundamental issues of quantum physics as well as for technological applications such as quantum information processing. Recent developments in this field have increased our basic understanding on how non-Markovian effects influence the dynamics of an open quantum system, paving the way to exploit memory effects for various quantum control tasks. Most often, the environment of an open system is thought to act as a sink for the system information. However, here we demonstrate experimentally that a photonic open system can exploit the information initially held by its environment. Correlations in the environmental degrees of freedom induce nonlocal memory effects where the bipartite open system displays, counterintuitively, local Markovian and global non-Markovian character. Our results also provide novel methods to protect and distribute entanglement, and to experimentally quantify correlations in photonic environments.

Liu, Bi-Heng; Cao, Dong-Yang; Huang, Yun-Feng; Li, Chuan-Feng; Guo, Guang-Can; Laine, Elsi-Mari; Breuer, Heinz-Peter; Piilo, Jyrki

2013-01-01

332

Ab initio statistical mechanics of surface adsorption and desorption. II. Nuclear quantum effects  

E-print Network

Ab initio statistical mechanics of surface adsorption and desorption. II. Nuclear quantum effects D-integral formulation of quantum statistical mechanics can be used to construct practical ab initio techniques statistical-mechanical approximations, apart from the treat- ment of the nuclei as classical particles

Alfè, Dario

333

Novel Atomic Coherence and Interference Effects in Quantum Optics and Atomic Physics  

E-print Network

It is well known that the optical properties of multi-level atomic and molecular system can be controlled and manipulated efficiently using quantum coherence and interference, which has led to many new effects in quantum optics for e.g. lasing...

Jha, Pankaj

2012-10-19

334

Magnetic field sensing beyond the standard quantum limit under the effect of decoherence  

Microsoft Academic Search

Entangled states can potentially be used to outperform the standard quantum limit by which every classical sensor is bounded. However, entangled states are very susceptible to decoherence, and so it is not clear whether one can really create a superior sensor to classical technology via a quantum strategy which is subject to the effect of realistic noise. This paper presents

Yuichiro Matsuzaki; Simon C. Benjamin; Joseph Fitzsimons

2011-01-01

335

Acceleration of positrons by a relativistic electron beam in the presence of quantum effects  

SciTech Connect

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.

Niknam, A. R. [Laser and Plasma Research Institute, Shahid Beheshti University, G.C., Tehran (Iran, Islamic Republic of)] [Laser and Plasma Research Institute, Shahid Beheshti University, G.C., Tehran (Iran, Islamic Republic of); Aki, H.; Khorashadizadeh, S. M. [Physics Department, Birjand University, Birjand (Iran, Islamic Republic of)] [Physics Department, Birjand University, Birjand (Iran, Islamic Republic of)

2013-09-15

336

Hydride Transfer in Liver Alcohol Dehydrogenase: Quantum Dynamics, Kinetic Isotope Effects, and Role of Enzyme Motion  

E-print Network

of the transferring hydrogen are incorporated with a mixed quantum/classical molecular dynamics method in which dynamical effects are determined by calculating the transmission coefficients with a reactive flux scheme based on real-time molecular dynamics with quantum transitions (MDQT) surface hopping trajectories

Hammes-Schiffer, Sharon

337

The Ramsauer-Townsend Effect and the de Broglie-Bohm Quantum Mechanics  

E-print Network

In this work we study the Ramsauer-Townsend effect.First, we use the Quantum Mechanical Formalism of Schrodinger. After, it is calculated with the Quantum Mechanical Formalism of de Broglie-Bohm. In this case, we use the Kostin equation, taking into account the energy dissipation of the electrons scattered by sharp edged potential wells.

Bassalo, J M F; Nassar, A; Cattani, M

2009-01-01

338

The Ramsauer-Townsend Effect and the de Broglie-Bohm Quantum Mechanics  

E-print Network

In this work we study the Ramsauer-Townsend effect.First, we use the Quantum Mechanical Formalism of Schrodinger. After, it is calculated with the Quantum Mechanical Formalism of de Broglie-Bohm. In this case, we use the Kostin equation, taking into account the energy dissipation of the electrons scattered by sharp edged potential wells.

J. M. F. Bassalo; P. T. S. Alencar; A. Nassar; M. Cattani

2009-04-07

339

Stark Effect of Interactive Electron-hole pairs in Spherical Semiconductor Quantum Dots  

E-print Network

. Abstract. We present a theoretical approach, based on the effective mass approximation model are found to be in good agreement with experimental data over a significant domain of quantum dot sizes,7]. The characteristic blue-shift observed in optical spectra of such strongly quantum-confined systems emerges

340

Elastic Recoil Detection Analysis of FeN thin films.  

PubMed

Thin films of transition metal nitrides are interesting materials due to their special features such as high hardness and chemical inertness. In our present work, we are reporting Elastic Recoil Detection Analysis of FeN/Si system using 100 MeV Au beam. Recoils ions were detected using ?E-E detector telescope. Diffraction pattern of pristine FeN thin films indicates amorphous nature of iron nitride thin film. MOKE results show irradiation can be used for controlling the magnetic properties such as coercivity. PMID:22871447

Dhunna, Renu; Jain, I P; Sahajwalla, Veena

2012-10-01

341

Electron-pair correlations seen by recoil-ion spectroscopy  

SciTech Connect

A fourth-order Wannier description of electron-pair escape has been extended to include non-zero total angular momentum. A key element of the description is the electron-pair center-of-mass momentum, which is fully represented by the momentum distribution of the recoiling ion. The authors have thus compared general and Wannier-theory predictions with recoil-ion measurements of electron-pair angular distributions following double-photoionization of helium. Their approach and recent experimental results down to 1 eV above threshold will be presented.

Feagin, J.M. [California State Univ., Fullerton, CA (United States); Doerner, R.; Cocke, C.L.

1996-05-01

342

On quantum effects on the surface of solid hydrogen  

SciTech Connect

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.

Marchenko, V. I. [Russian Academy of Sciences, Kapitza Institute for Physical Problems (Russian Federation)] [Russian Academy of Sciences, Kapitza Institute for Physical Problems (Russian Federation)

2013-10-15

343

Higher time derivatives in effective equations of canonical quantum systems  

NASA Astrophysics Data System (ADS)

Quantum-corrected equations of motion generically contain higher time derivatives, computed here in the setting of canonically quantized systems. The main example in which detailed derivations are presented is a general anharmonic oscillator, but conclusions can be drawn also for systems in quantum gravity and cosmology.

Bojowald, Martin; Brahma, Suddhasattwa; Nelson, Elliot

2012-11-01

344

Nuclear spin diffusion effects in optically pumped quantum wells  

NASA Astrophysics Data System (ADS)

We studied the influence of the nuclear spin diffusion on the dynamical nuclear polarization of low dimensional nanostructures subject to optical pumping. Our analysis shows that the induced nuclear spin polarization in semiconductor nanostructures will develop both a time and position dependence due to a nonuniform hyperfine interaction as a result of the geometrical confinement provided by the system. In particular, for the case of semiconductor quantum wells, nuclear spin diffusion is responsible for a nonzero nuclear spin polarization in the quantum well barriers. As an example we considered a 57 GaAs square quantum well and a 1000 AlxGa1-xAs parabolic quantum well both within 500 Al0.4Ga0.6As barriers. We found that the average nuclear spin polarization in the quantum well barriers depends on the strength of the geometrical confinement provided by the structure and is characterized by a saturation time of the order of few hundred seconds. Depending on the value of the nuclear spin diffusion constant, the average nuclear spin polarization in the quantum well barriers can get as high as 70% for the square quantum well and 40% for the parabolic quantum well. These results should be relevant for both time resolved Faraday rotation and optical nuclear magnetic resonance experimental techniques.

Henriksen, Daniel; Kim, Tom; ?ifrea, Ionel

2014-01-01

345

Microtubules: from classical properties to quantum effects in human cognition  

E-print Network

Theories describing information processing and signaling in microtubules 8 3.1 Cellular automata This seminar paper was motivated by the talk of Professor Dr. Sir Roger Penrose about the Orchestrated objective reduction theory and the potential role of quantum mechanics and quantum gravity in conscious

?umer, Slobodan

346

Motion and gravity effects in the precision of quantum clocks  

E-print Network

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.

Lindkvist, Joel; Johansson, Gran; Fuentes, Ivette

2014-01-01

347

Motion and gravity effects in the precision of quantum clocks  

E-print Network

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.

Joel Lindkvist; Carlos Sabn; Gran Johansson; Ivette Fuentes

2014-09-15

348

Laser Pulses as Measurements. Application to the Quantum Zeno Effect  

E-print Network

Short pulses of a probe laser have been used in the past to measure whether a two-level atom is in its ground or excited state. The probe pulse couples the ground state to a third, auxiliary, level of the atom. Occurrence or absence of resonance fluorescence were taken to mean that the atom was found in its ground or excited state, respectively. In this paper we investigate to what extent this procedure results in an effective measurement to which the projection postulate can be applied, at least approximately. We discuss in detail the complications arising from an additional time development of the two-level system proper during a probe pulse. We extend our previous results for weak probe pulses to the general case and show that one can model an ideal (projection-postulate) measurement much better with a strong than a weak probe pulse. In an application to the quantum Zeno effect we calculate the slow-down of the atomic time development under n repeated probe pulse measurements and determine the corrections compared to the case of n ideal measurements.

Almut Beige; Gerhard C. Hegerfeldt; Dirk G. Sondermann

1996-07-04

349

Orbital Kondo effect in a parallel double quantum dot.  

PubMed

We construct a theoretical model to study the orbital Kondo effect in a parallel double quantum dot (DQD). Recently, pseudospin-resolved transport spectroscopy of the orbital Kondo effect in a DQD has been experimentally reported. The experiment revealed that when interdot tunneling is ignored, two and one Kondo peaks exist in the conductance-bias curve for pseudospin-non-resolved and pseudospin-resolved cases, respectively. Our theoretical studies reproduce this experimental result. We also investigate the case of all lead voltages being non-equal (the complete pseudospin-resolved case) and found that there are at most four Kondo peaks in the curve of the conductance versus the pseudospin splitting energy. When interdot tunneling is introduced, some new Kondo peaks and dips can emerge. Furthermore, the pseudospin transport and the pseudospin flipping current are also studied in the DQD system. Since the pseudospin transport is much easier to control and measure than the real spin transport, it can be used to study the physical phenomenon related to the spin transport. PMID:25299453

Bao, Zhi-Qiang; Guo, Ai-Min; Sun, Qing-Feng

2014-10-29

350

Electrostatically Shielded Quantum Confined Stark Effect Inside Polar Nanostructures  

PubMed Central

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

2009-01-01

351

All-Optical Switching Using the Quantum Zeno Effect and Two-Photon Absorption  

E-print Network

We have previously shown that the quantum Zeno effect can be used to implement quantum logic gates for quantum computing applications, where the Zeno effect was produced using a strong two-photon absorbing medium. Here we show that the Zeno effect can also be used to implement classical logic gates whose inputs and outputs are high-intensity fields (coherent states). The operation of the devices can be understood using a quasi-static analysis, and their switching times are calculated using a dynamic approach. The two-photon absorption coefficient of rubidium vapor is shown to allow operation of these devices at relatively low power levels.

B. C. Jacobs; J. D. Franson

2009-05-08

352

All-Optical Switching Using the Quantum Zeno Effect and Two-Photon Absorption  

E-print Network

We have previously shown that the quantum Zeno effect can be used to implement quantum logic gates for quantum computing applications, where the Zeno effect was produced using a strong two-photon absorbing medium. Here we show that the Zeno effect can also be used to implement classical logic gates whose inputs and outputs are high-intensity fields (coherent states). The operation of the devices can be understood using a quasi-static analysis, and their switching times are calculated using a dynamic approach. The two-photon absorption coefficient of rubidium vapor is shown to allow operation of these devices at relatively low power levels.

Jacobs, B C

2009-01-01

353

Discreteness corrections and higher spatial derivatives in effective canonical quantum gravity  

NASA Astrophysics Data System (ADS)

Canonical quantum theories with discrete space may imply interesting effects. This paper presents a general effective description, paying due attention to the role of higher spatial derivatives in a local expansion and differences to higher time derivatives. In a concrete set of models, it is shown that spatial derivatives one order higher than the classical one are strongly restricted in spherically symmetric effective loop quantum gravity. Moreover, radial holonomy corrections alone cannot be anomaly free to this order.

Bojowald, Martin; Paily, George M.; Reyes, Juan D.

2014-07-01

354

Discreteness corrections and higher spatial derivatives in effective canonical quantum gravity  

E-print Network

Canonical quantum theories with discrete space may imply interesting effects. This article presents a general effective description, paying due attention to the role of higher spatial derivatives in a local expansion and differences to higher time derivatives. In a concrete set of models, it is shown that spatial derivatives one order higher than the classical one are strongly restricted in spherically symmetric effective loop quantum gravity. Moreover, radial holonomy corrections cannot be anomaly-free to this order.

Martin Bojowald; George M. Paily; Juan D. Reyes

2014-02-20

355

On the residual effective potential within Global 1D Quantum Gravity  

E-print Network

The conjecture on Global One-Dimensionality within Quantum General Relativity leads to the model of quantum gravity possessing nontrivial field theoretic content. This is a midisuperspatial model, which quantum mechanical part can be considered independently. The fragment, basing on the Dirac-Faddeev canonical primary quantization of Hamiltonian constraint, in fact constitutes minimal effective model within standard quantum geometrodynamics with potential different from the standard. It uses one-dimensional wave functions, where the (global) dimension is a volume form of a 3-embedding. In this paper some elements of the global 1D quantum mechanics are presented. We consider absence of matter fields. Generalized functional expansion in the global dimension of the effective potential is discussed. Finally, its residual approximation, the Newton-Coulomb type potential, realized by all embeddings being maximally symmetric 3-dimensional Einstein manifolds is studied.

Glinka, L A

2009-01-01

356

Quantum rod-sensitized solar cell: nanocrystal shape effect on the photovoltaic properties.  

PubMed

The effect of the shape of nanocrystal sensitizers in photoelectrochemical cells is reported. CdSe quantum rods of different dimensions were effectively deposited rapidly by electrophoresis onto mesoporous TiO(2) electrodes and compared with quantum dots. Photovoltaic efficiency values of up to 2.7% were measured for the QRSSC, notably high values for TiO(2) solar cells with ex situ synthesized nanoparticle sensitizers. The quantum rod-based solar cells exhibit a red shift of the electron injection onset and charge recombination is significantly suppressed compared to dot sensitizers. The improved photoelectrochemical characteristics of the quantum rods over the dots as sensitizers is assigned to the elongated shape, allowing the build-up of a dipole moment along the rod that leads to a downward shift of the TiO(2) energy bands relative to the quantum rods, leading to improved charge injection. PMID:22452287

Salant, Asaf; Shalom, Menny; Tachan, Zion; Buhbut, Sophia; Zaban, Arie; Banin, Uri

2012-04-11

357

Magnet field sensing beyond the standard quantum limit under the effect of decoherence  

E-print Network

Entangled states can potentially be used to outperform the standard quantum limit which every classical sensor is bounded by. However, entangled states are very susceptible to decoherence, and so it is not clear whether one can really create a superior sensor to classical technology via a quantum strategy which is subject to the effect of realistic noise. This paper presents an investigation of how a quantum sensor composed of many spins is affected by independent dephasing. We adopt general noise models including non-Markovian effects, and in these noise models the performance of the sensor depends crucially on the exposure time of the sensor to the field. We have found that, by choosing an appropriate exposure time within non-Markovian time region, an entangled sensor does actually beat the standard quantum limit. Since independent dephasing is one of the most typical sources of noise in many systems, our results suggest a practical and scalable approach to beating the standard quantum limit.

Matsuzaki, Yuichiro; Fitzsimons, Joseph

2011-01-01

358

Magnet field sensing beyond the standard quantum limit under the effect of decoherence  

E-print Network

Entangled states can potentially be used to outperform the standard quantum limit which every classical sensor is bounded by. However, entangled states are very susceptible to decoherence, and so it is not clear whether one can really create a superior sensor to classical technology via a quantum strategy which is subject to the effect of realistic noise. This paper presents an investigation of how a quantum sensor composed of many spins is affected by independent dephasing. We adopt general noise models including non-Markovian effects, and in these noise models the performance of the sensor depends crucially on the exposure time of the sensor to the field. We have found that, by choosing an appropriate exposure time within non-Markovian time region, an entangled sensor does actually beat the standard quantum limit. Since independent dephasing is one of the most typical sources of noise in many systems, our results suggest a practical and scalable approach to beating the standard quantum limit.

Yuichiro Matsuzaki; Simon C. Benjamin; Joseph Fitzsimons

2011-01-13

359

Mobilization of thorium, radium and radon radionuclides in ground water by successive alpha-recoils  

Microsoft Academic Search

Alpha-recoil is an important way for the mobilization of ?-decay daughters in ground water. The processes of decay and recoil from 238U to 222Rn and from 232Th to 220Rn are successive. The release rates of successive recoils in this study are quantitatively estimated under two extreme conditions: complete absorption; and no adsorption of recoil elements by the porous medium. The

Hongbing Sun; Thomas M. Semkow

1998-01-01

360

New efficient approach to calculations of exciton resonance position and width for quantum-confined Stark effect in shallow quantum wells  

Microsoft Academic Search

We develop a new computationally efficient approach to the quantum-confined Stark effect in shallow quantum wells that provides a deeper physical insight, significantly reduces required computational resources, and yields some analytical results for the case of shallow quantum wells. The approach is based on a combination of the self-consistent field approach and the complex-coordinate exterior-scaling procedure that allows one to

I. V. Ponomarev; Lev Deych; Alexander Lisyansky

2004-01-01

361

Proton recoil detector of fusion neutrons using natural diamond  

NASA Astrophysics Data System (ADS)

Diamond, with its high radiation damage resistance, is an attractive alternative to silicon for neutron measurements in next step fusion experiments. A 200-?m-thick type IIa natural diamond with Ti/Au contacts was tested at the LAMPF-WNR facility by time-of-flight neutron energy identification. The crystal, having a carrier lifetime of up to 1 ns, was arranged in a low-energy-resolution, high-sensitivity proton recoil telescope consisting of a polyethylene radiator and a low-energy-proton Teflon filter. This arrangement is similar to the triton burnup monitor of Croft et al. [Rev. Sci. Instrum. 64, 1418 (1993)], where a silicon photodiode was used as a recoil proton detector. The observed sensitivity for 14 MeV neutrons (DT) is (1.250.15)10-3 counts/neutron. However, a high contribution of neutron-induced events in the diamond, mainly carbon (A=12) recoils, was observed. A one-dimensional calculation for the detector response to carbon recoil and proton deposition is compared to the measurements. Poor energy resolution of the diamond detector precludes pulse height discrimination between direct 2.5 MeV neutrons events and proton events corresponding to 14 MeV neutrons. Therefore, an overall DT/DD neutron sensitivity ratio of only 6.5 is achieved. This value is much lower than the ratio of 540 reported by Croft et al. in their silicon (A=28) monitor.

Maqueda, R. J.; Barnes, Cris W.; Han, S. S.; Staples, P. A.; Wagner, R. S.

1997-01-01

362

Status and Prospects of the HERMES Recoil Detector  

E-print Network

/Scintillator sandwich Fiber Detector (SFT) 2 barrels with 4 layers of scintillating fibers 2 parallel and 2 stereo SFT Particle Identification 8HERMES Recoil Detector A. Mussgiller, SPIN 2008, 10/10/08 SSDV /c : SSD & SFT & PDp ~0.6 GeV /c #12; Particle Identification (p > 0

363

Dark Matter or Neutrino recoil? Interpretation of Recent Experimental Results  

E-print Network

The elastic nuclear recoil signal, being under intense scrutiny by multiple underground experiments, can be interpreted either as coming from the interaction of nuclei with WIMP dark matter or from the scattering of new species of MeV-energy neutrinos. The most promising model for the latter case is a neutrino $\

Maxim Pospelov; Josef Pradler

2013-11-22

364

Scintillation response of liquid xenon to low energy nuclear recoils  

NASA Astrophysics Data System (ADS)

Liquid Xenon (LXe) is expected to be an excellent target and detection medium to search for dark matter in the form of Weakly Interacting Massive Particles (WIMPs). We have measured the scintillation efficiency of nuclear recoils with kinetic energy between 10.4 and 56.5 keV relative to that of 122 keV gamma rays from C57o. The scintillation yield of 56.5 keV recoils was also measured as a function of applied electric field, and compared to that of gamma rays and alpha particles. The Xe recoils were produced by elastic scattering of 2.4 MeV neutrons in liquid xenon at a variety of scattering angles. The relative scintillation efficiency is 0.1300.024 and 0.2270.016 for the lowest and highest energy recoils, respectively. This is about 15% less than the value predicted by Lindhard, based on nuclear quenching. Our results are in good agreement with more recent theoretical predictions that consider the additional reduction of scintillation yield due to biexcitonic collisions in LXe.

Aprile, E.; Giboni, K. L.; Majewski, P.; Ni, K.; Yamashita, M.; Hasty, R.; Manzur, A.; McKinsey, D. N.

2005-10-01

365

A Candidate Recoiling Black Hole in a Nearby Dwarf Galaxy  

NASA Astrophysics Data System (ADS)

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

Koss, Michael

2014-10-01

366

Accurate Simulations of Pb Recoils in SuperCDMS  

NASA Astrophysics Data System (ADS)

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

Redl, P.

2014-09-01

367

Measurement of high momentum transfer reactions by recoil detection  

Microsoft Academic Search

A method is described for studying reactions at medium energies by measuring the magnetic rigidity, time of flight, and energy loss of the resulting recoil products. The method works best for reactions with two-body final states where one of the outgoing particles is relatively light. A magnetic spectrometer with a special focal plane detector has been used. The detector consists

J. Homolka; W. Schott; W. Wagner; W. Wilhelm; R. D. Bent; M. Fatyga; R. E. Pollock; M. Saber; R. E. Segel; P. Kienle; K. E. Rehm

1987-01-01

368

The quantum Hall effect at 5/2 filling factor  

NASA Astrophysics Data System (ADS)

Experimental discovery of a quantized Hall state at 5/2 filling factor presented an enigmatic finding in an established field of study that has remained an open issue for more than twenty years. In this review we first examine the experimental requirements for observing this state and outline the initial theoretical implications and predictions. We will then follow the chronology of experimental studies over the years and present the theoretical developments as they pertain to experiments, directed at sets of issues. These topics will include theoretical and experimental examination of the spin properties at 5/2; is the state spin polarized? What properties of the higher Landau levels promote development of the 5/2 state, what other correlation effects are observed there, and what are their interactions with the 5/2 state? The 5/2 state is not a robust example of the fractional quantum Hall effect: what experimental and material developments have allowed enhancement of the effect? Theoretical developments from initial pictures have promoted the possibility that 5/2 excitations are exceptional; do they obey non-abelian statistics? The proposed experiments to determine this and their executions in various forms will be presented: this is the heart of this review. Experimental examination of the 5/2 excitations through interference measurements will be reviewed in some detail, focusing on recent results that demonstrate consistency with the picture of non-abelian charges. The implications of this in the more general physics picture is that the 5/2 excitations, shown to be non-abelian, should exhibit the properties of Majorana operators. This will be the topic of the last review section.

Willett, R. L.

2013-07-01

369

Quantum wavepacket ab initio molecular dynamics: Simulating quantum nuclear effects in complex systems  

NASA Astrophysics Data System (ADS)

A methodology, Quantum Wavepacket Ab Initio Molecular Dynamics (QWAIMD), for the efficient, simultaneous dynamics of electrons and nuclei is presented. This approach allows for the quantum-dynamical treatment of a subset of nuclei in complex, molecular systems while treating the remaining nuclei and electrons within in the ab initio molecular dynamics (AIMD) paradigm. Developments of QWAIMD discussed within include: (a) a novel sampling algorithm dubbed Time-Dependent Deterministic Sampling (TDDS), which increases the computational efficiency by several orders of magnitude; (b) generalizations to hybrid QM/QM and QM/MM electronic structure methods via a combination of the ONIOM and empirical valence bond approaches, which may allow for the accurate simulation of large molecules; and (c) a novel velocity-flux autocorrelation function to calculate the vibrational density-of-states of quantum-classical systems. These techniques are benchmarked on calculations of small, hydrogen-bound clusters. Furthermore, since many chemical processes occur over time-scales inaccessible to computation, a scheme is discussed and benchmarked here which can bias both QWAIMD and classical-AIMD dynamics to sample these long time-scale events, like proton transfer in enzyme catalysis. Finally, hydrogen tunneling in an enzyme, soybean lipoxygenase-1 (SLO-1) is examined by calculating the orbitals (eigenstates) of the transferring proton along the reaction coordinate. This orbital analysis is then supplemented by using quantum measurement theory to reexamine the transfer.

Sumner, Isaiah

370

Quantum-electrodynamics corrections in pionic hydrogen  

SciTech Connect

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.

Schlesser, S.; Le Bigot, E.-O.; Indelicato, P. [Laboratoire Kastler Brossel, Ecole Normale Superieure, CNRS, Universite Pierre et Marie Curie-Paris 6, Case 74, 4 place Jussieu, F-75005 Paris (France); Pachucki, K. [Faculty of Physics, University of Warsaw, Hoza 69, PL-00-681 Warsaw (Poland)

2011-07-15

371

Effect of laser polarization on quantum electrodynamical cascading  

NASA Astrophysics Data System (ADS)

Development of quantum electrodynamical (QED) cascades in a standing electromagnetic wave for circular and linear polarizations is simulated numerically with a 3D PIC-MC code. It is demonstrated that for the same laser energy the number of particles produced in a circularly polarized field is greater than in a linearly polarized field, though the acquiring mean energy per particle is larger in the latter case. The qualitative model of laser-assisted QED cascades is extended by including the effect of polarization of the field. It turns out that cascade dynamics is notably more complicated in the case of linearly polarized field, where separation into the qualitatively different "electric" and "magnetic" regions (where the electric field is stronger than the magnetic field and vice versa) becomes essential. In the "magnetic" regions, acceleration is suppressed, and moreover the high-energy electrons are even getting cooled by photon emission. The volumes of the "electric" and "magnetic" regions evolve periodically in time and so does the cascade growth rate. In contrast to the linear polarization, the charged particles can be accelerated by circularly polarized wave even in "magnetic region." The "electric" and "magnetic" regions do not evolve in time, and cascade growth rate almost does not depend on time for circular polarization.

Bashmakov, V. F.; Nerush, E. N.; Kostyukov, I. Yu.; Fedotov, A. M.; Narozhny, N. B.

2014-01-01

372

Interaction effects and quantum phase transitions in topological insulators  

SciTech Connect

We study strong correlation effects in topological insulators via the Lanczos algorithm, which we utilize to calculate the exact many-particle ground-state wave function and its topological properties. We analyze the simple, noninteracting Haldane model on a honeycomb lattice with known topological properties and demonstrate that these properties are already evident in small clusters. Next, we consider interacting fermions by introducing repulsive nearest-neighbor interactions. A first-order quantum phase transition was discovered at finite interaction strength between the topological band insulator and a topologically trivial Mott insulating phase by use of the fidelity metric and the charge-density-wave structure factor. We construct the phase diagram at T=0 as a function of the interaction strength and the complex phase for the next-nearest-neighbor hoppings. Finally, we consider the Haldane model with interacting hard-core bosons, where no evidence for a topological phase is observed. An important general conclusion of our work is that despite the intrinsic nonlocality of topological phases their key topological properties manifest themselves already in small systems and therefore can be studied numerically via exact diagonalization and observed experimentally, e.g., with trapped ions and cold atoms in optical lattices.

Varney, Christopher N. [Department of Physics, Georgetown University, Washington, DC 20057 (United States); Joint Quantum Institute and Department of Physics, University of Maryland, College Park, Maryland 20742 (United States); Sun Kai; Galitski, Victor [Joint Quantum Institute and Department of Physics, University of Maryland, College Park, Maryland 20742 (United States); Condensed Matter Theory Center, Department of Physics, University of Maryland, College Park, Maryland 20742 (United States); Rigol, Marcos [Department of Physics, Georgetown University, Washington, DC 20057 (United States)

2010-09-15

373

Evidence of Quantum Size Effects in Synthetic Ge Nanocrystals  

NASA Astrophysics Data System (ADS)

Ge nanocrystals with diameters of 4-5 nm were chemically synthesized and incorporated into a hexane colloidal suspension. Optical characterization was performed, including photoluminescence (PL), PL excitation (PLE), PL lifetimes, and absorption spectroscopy. A broad distribution of sizes results in a broadband PL in the blue spectral region near 400 nm and a broader peak near 650 nm when excited at 300 nm. PLE spectroscopy for the blue and red peaks yields a broad peak extending from 290-410 nm indicating that both peaks arise from the same origin. Size-selective PL spectroscopy exhibits uniform spectral shifts as the excitation wavelength is changed. The spectral shifts of the blue peak range from 400-480 nm when excited between 300-400 nm. Our results show that the blue emission arises from quantum confinement effects while the red peak is due to traps. These results agree with previous work we have performed on Si nanocrystals. Work at LLNL performed under the auspices of the USDoE under contract number W-7405-ENG-48.

Delgado, Gildardo; Lee, Howard; Kauzlarich, Susan; Taylor, Boyd

1997-03-01

374

Brane classical and quantum cosmology from an effective action  

NASA Astrophysics Data System (ADS)

Motivated by the Randall-Sundrum braneworld scenario, we discuss the classical and quantum dynamics of a (d+1)-dimensional boundary wall between a pair of (d+2)-dimensional topological Schwarzschild-AdS black holes. We assume there are quite generalbut not completely arbitrarymatter fields living on the boundary brane universe, and that its geometry is that of a Friedmann-Lematre-Robertson-Walker (FLRW) model. The effective action governing the model in the minisuperspace approximation is derived. We find that the presence of black hole horizons in the bulk gives rise to a complex action for certain classically allowed brane configurations, but that the imaginary contribution plays no role in the equations of motion. Classical and instanton brane trajectories are examined in general and for special cases, and we find a subset of configuration space that is not allowed at the classical or semiclassical level; this subset corresponds to spacelike branes carrying tachyonic matter. The Hamiltonization and Dirac quantization of the model is then performed for the general case; the latter involves the manipulation of the Hamiltonian constraint before it is transformed into an operator that annihilates physical state vectors. The ensuing covariant Wheeler-DeWitt equation is examined at the semiclassical level, and we consider the possible localization of the brane universes wave function away from the cosmological singularity. This is easier to achieve for branes with low density and/or spherical spatial sections.

Seahra, Sanjeev S.; Sepangi, H. R.; Ponce de Leon, J.

2003-09-01

375

Theory of integer quantum Hall effect in insulating bilayer graphene  

NASA Astrophysics Data System (ADS)

A variational ground state for insulating bilayer graphene (BLG), subject to quantizing magnetic fields, is proposed. Due to the Zeeman coupling, the layer antiferromagnet (LAF) order parameter in fully gapped BLG gets projected onto the spin easy plane, and simultaneously a ferromagnet order, which can further be enhanced by exchange interaction, develops in the direction of the magnetic field. The activation gap for the ? =0 Hall state then displays a crossover from quadratic to linear scaling with the magnetic field, as it gets stronger, and I obtain excellent agreement with a number of recent experiments with realistic strengths for the ferromagnetic interaction. A component of the LAF order, parallel to the external magnetic field, gives birth to additional incompressible Hall states at filling ? =2, whereas the remote hopping in BLG yields ? =1 Hall states. Evolution of the LAF order in tilted magnetic fields, scaling of the gap at ? =2, the effect of external electric fields on various Hall plateaus, and different possible hierarchies of fractional quantum Hall states are highlighted.

Roy, Bitan

2014-05-01

376

H + D2 Reaction Dynamics in the Limit of Low Product Recoil Energy J. Aldegunde,  

E-print Network

H + D2 Reaction Dynamics in the Limit of Low Product Recoil Energy J. Aldegunde, D. Herraez increases and the corresponding energy available for product recoil decreases. This behavior was attributed, whose influence becomes more significant as the recoil energy of the products tends to zero, which

Zare, Richard N.

377

Effective action approach to quantum phase transitions in bosonic lattices  

E-print Network

In this thesis, I develop a new, field-theoretic method for describing the quantum phase transition between Mott insulating and superfluid states observed in bosonic optical lattices. I begin by adding to the Hamiltonian ...

Bradlyn, Barry J

2009-01-01

378

Effect of multimode entanglement on lossy optical quantum metrology  

NASA Astrophysics Data System (ADS)

In optical interferometry multimode entanglement is often assumed to be the driving force behind quantum enhanced measurements. Recent work has shown this assumption to be false: single-mode quantum states perform just as well as their multimode entangled counterparts. We go beyond this to show that when photon losses occur, an inevitability in any realistic system, multimode entanglement is actually detrimental to obtaining quantum enhanced measurements. We specifically apply this idea to a superposition of coherent states, demonstrating that these states show a robustness to loss that allows them to significantly outperform their competitors in realistic systems. A practically viable measurement scheme is then presented that allows measurements close to the theoretical bound, even with loss. These results promote an alternate way of approaching optical quantum metrology using single-mode states that we expect to have great implications for the future.

Knott, P. A.; Proctor, T. J.; Nemoto, Kae; Dunningham, J. A.; Munro, W. J.

2014-09-01

379

Effects of control error on an adiabatic quantum algorithm  

E-print Network

Noise in adiabatic quantum computation can be modelled as a perturbation of the problem Hamiltonian. For a type of noise called control error, the perturbation can be considered to have the same structure as the problem ...

Platt, Edward L

2006-01-01

380

The effect of finite Larmor radius corrections on Jeans instability of quantum plasma  

SciTech Connect

The influence of finite Larmor radius (FLR) effects on the Jeans instability of infinitely conducting homogeneous quantum plasma is investigated. The quantum magnetohydrodynamic (QMHD) model is used to formulate the problem. The contribution of FLR is incorporated to the QMHD set of equations in the present analysis. The general dispersion relation is obtained analytically using the normal mode analysis technique which is modified due to the contribution of FLR corrections. From general dispersion relation, the condition of instability is obtained and it is found that Jeans condition is modified due to quantum effect. The general dispersion relation is reduced for both transverse and longitudinal mode of propagations. The condition of gravitational instability is modified due to the presence of both FLR and quantum corrections in the transverse mode of propagation. In longitudinal case, it is found to be unaffected by the FLR effects but modified due to the quantum corrections. The growth rate of Jeans instability is discussed numerically for various values of quantum and FLR corrections of the medium. It is found that the quantum parameter and FLR effects have stabilizing influence on the growth rate of instability of the system.

Sharma, Prerana [Physics Department, Ujjain Engineering College, Ujjain, Madhya Pradesh 465010 (India)] [Physics Department, Ujjain Engineering College, Ujjain, Madhya Pradesh 465010 (India); Chhajlani, R. K. [School of Studies in Physics, Vikram University Ujjain, Madhya Pradesh 465010 (India)] [School of Studies in Physics, Vikram University Ujjain, Madhya Pradesh 465010 (India)

2013-09-15

381

Quantum-size effects on Tc in superconducting nanofilms  

Microsoft Academic Search

An essential property of a high-quality metallic nanofilm is the quantization of the electron spectrum due to dimensional confinement in one direction. Quantum confinement has a substantial impact on the superconducting characteristics and leads to quantum-size variations of the critical temperature Tc with film thickness. We demonstrate that the Bogoliubov-de Gennes equations are able to describe the thickness-dependent Tc in

A. A. Shanenko; M. D. Croitoru; F. M. Peeters

2006-01-01

382

Tunable optical Aharonov-Bohm effect in a semiconductor quantum ring  

NASA Astrophysics Data System (ADS)

By applying an electric field perpendicular to a semiconductor quantum ring we show that it is possible to modify the single particle wave function between quantum dot (QD)-like and ring-like. The constraints on the geometrical parameters of the quantum ring to realize such a transition are derived. With such a perpendicular electric field we are able to tune the Aharanov-Bohm (AB) effect for both the single particle and for excitons. The tunability is in both the strength of the AB effect as well as in its periodicity. We also investigate the strain induce potential inside the self-assembled quantum ring and the effect of the strain on the AB effect.

Li, Bin; Peeters, F. M.

2011-03-01

383

On the Compatibility Between Quantum and Relativistic Effects in an Electromagnetic Bridge Theory  

E-print Network

The Dipolar Electromagnetic Source (DEMS) model, based on the Poynting Vector Conjecture, conduces in Bridge Theory to a derivation of the Lorentz transformation connecting pairs of events. The results prove a full compatibility between quantum and relativistic effects.

Massimo Auci

2010-03-18

384

An analytical framework for field electron emission, incorporating quantum- confinement effects  

E-print Network

As field electron emitters shrink to nanoscale dimensions, the effects of quantum confinement of the electron supply and electric field enhancement at the emitter tip play a significant role in determining the emitted ...

Patterson. Alex A. (Alex Andrew)

2013-01-01

385

Quantum Hall effect and Landau-level crossing of Dirac fermions in trilayer graphene  

E-print Network

The physics of Dirac fermions in condensed-matter systems has received extraordinary attention following the discoveries of two new types of quantum Hall effect in single-layer and bilayer graphene1, 2, 3. The electronic ...

Taychatanapat, Thiti

386

Effects of competing orders and quantum criticality on the quasiparticle tunneling spectroscopy and vortex dynamics of  

E-print Network

1 Effects of competing orders and quantum criticality on the quasiparticle tunneling spectroscopy, and the characteristic field correlates well with the quasiparticle tunneling spectra, showing increasing spectral cuprates are examined by comparing theory with experimental data, and the physics implications

Yeh, Nai-Chang

387

FAST TRACK COMMUNICATION: An effective gravity model and singularity avoidance in quantum FRW cosmologies  

NASA Astrophysics Data System (ADS)

An effective formulation of gravity is discussed, which lies in between the Wheeler-DeWitt approach and that of classical cosmology. It has the virtue of naturally avoiding the singularity that appears in Friedman-Robertson-Walker cosmologies. The mechanism is made explicit in specific examples, where it is compared with the quantization provided by loop quantum cosmology. It is argued that it is the regularization of the classical Hamiltonian, performed in that theory, that avoids the singularity, rather than usually invoked quantum effects. However, a deeper study of the quantum nature of geometry in that framework should help to completely clarify the issue.

Haro, Jaume; Elizalde, Emilio

2009-05-01

388

Breakdown of the Quantum Hall Effects in Hole Systems at High Induced Currents  

NASA Astrophysics Data System (ADS)

The magnetisation of two dimensional hole systems in the quantum Hall regime has been studied using a highly-sensitive torsion balance magnetometer. In a time varying magnetic field eddy currents are induced which become large around integer and fractional filling factors where ?xx takes a very low value. The sweep rate and temperature dependence of these induced currents are shown to be in good agreement with the model of quantum Hall effect breakdown proposed recently by Matthews et al. This model also allows comparison between the energy gap at different filling factors and so provides a measurement of the fractional quantum Hall effect energy gap, ?1/3.

Gething, J. D.; Matthews, A. J.; Usher, A.; Portnoi, M. E.; Kavokin, K. V.; Henini, M.

2005-06-01

389

Quantum Hall effect in bilayer and multilayer graphene with finite Fermi energy  

NASA Astrophysics Data System (ADS)

We discuss the quantum Hall effect of bilayer graphene with finite gate voltage where the Fermi energy exceeds the interlayer hopping energy. We calculated magnetic susceptibility, and diagonal and off-diagonal conductivities in finite-magnetic-field formalism. We also observed crossover of integer quantum Hall effect from two independent monolayer type systems to a strongly coupled bilayer system by changing the ratio of interlayer hopping energy and the Fermi energy. We also discuss the case of multilayer systems with Bernal stacking.

Nakamura, Masaaki; Hirasawa, Lila; Imura, Ken-Ichiro

2008-07-01

390

Observation of an anomalous decoherence effect in a quantum bath at room temperature  

PubMed Central

The decoherence of quantum objects is a critical issue in quantum science and technology. It is generally believed that stronger noise causes faster decoherence. Strikingly, recent theoretical work suggests that under certain conditions, the opposite is true for spins in quantum baths. Here we report an experimental observation of an anomalous decoherence effect for the electron spin-1 of a nitrogen-vacancy centre in high-purity diamond at room temperature. We demonstrate that, under dynamical decoupling, the double-transition can have longer coherence time than the single-transition even though the former couples to the nuclear spin bath as twice strongly as the latter does. The excellent agreement between the experimental and theoretical results confirms the controllability of the weakly coupled nuclear spins in the bath, which is useful in quantum information processing and quantum metrology. PMID:22146389

Huang, Pu; Kong, Xi; Zhao, Nan; Shi, Fazhan; Wang, Pengfei; Rong, Xing; Liu, Ren-Bao; Du, Jiangfeng

2011-01-01

391

Competing quantum effects in the dynamics of a flexible water model  

E-print Network

Numerous studies have identified large quantum mechanical effects in the dynamics of liquid water. In this paper, we suggest that these effects may have been overestimated due to the use of rigid water models and flexible models in which the intramolecular interactions were described using simple harmonic functions. To demonstrate this, we introduce a new simple point charge model for liquid water, q-TIP4P/F, in which the O--H stretches are described by Morse-type functions. We have parameterized this model to give the correct liquid structure, diffusion coefficient, and infra-red absorption frequencies in quantum (path integral-based) simulations. By comparing classical and quantum simulations of the liquid, we find that quantum mechanical fluctuations increase the rates of translational diffusion and orientational relaxation in our model by a factor of around 1.15. This effect is much smaller than that observed in all previous simulations of simple empirical water models, which have found a quantum effect of at least 1.4 regardless of the quantum simulation method or the water model employed. The small quantum effect in our model is a result of two competing phenomena. Intermolecular zero point energy and tunneling effects destabilize the hydrogen bonding network, leading to a less viscous liquid with a larger diffusion coefficient. However this is offset by intramolecular zero point motion, which changes the average water monomer geometry resulting in a larger dipole moment, stronger intermolecular interactions, and slower diffusion. We end by suggesting, on the basis of simulations of other potential energy models, that the small quantum effect we find in the diffusion coefficient is associated with the ability of our model to produce a single broad O-H stretching band in the infra-red absorption spectrum.

Scott Habershon; Thomas E. Markland; David E. Manolopoulos

2010-11-04

392

Effect of Magnesium Diffusion Into the Active Region of LED Structures with InGaN/GaN Quantum Wells on Internal Quantum Efficiency  

NASA Astrophysics Data System (ADS)

The results of experimental studies of the dependence of an internal quantum efficiency of blue LED structures with multiple InGaN/GaN quantum wells on the growth temperature of a p-GaN layer are presented. The effect of the magnesium diffusion on the photoluminescence characteristics of LED structures is discussed.

Romanov, I. S.; Prudaev, I. A.; Marmalyuk, A. A.; Kureshov, V. A.; Sabitov, D. R.; Mazalov, A. V.

2014-08-01

393

Quantum-mechanical description of Lense-Thirring effect for relativistic scalar particles  

E-print Network

Exact expression for the Foldy-Wouthuysen Hamiltonian of scalar particles is used for a quantum-mechanical description of the relativistic Lense-Thirring effect. The exact evolution of the angular momentum operator in the Kerr field approximated by a spatially isotropic metric is found. The quantum-mechanical description of the full Lense-Thirring effect based on the Laplace-Runge-Lenz vector is given in the nonrelativistic and weak-field approximation. Relativistic quantum-mechanical equations for the velocity and acceleration operators are obtained. The equation for the acceleration defines the Coriolis-like and centrifugal-like accelerations and presents the quantum-mechanical description of the frame-dragging effect.

Alexander J. Silenko

2014-08-10

394

Quantum effect on modulational instability of laser radiation in a semiconductor plasma  

SciTech Connect

Modulational instability of a high power laser radiation in a homogeneous unmagnetized piezoelectric semiconductor plasma has been investigated analytically. The fluid equations of quantum hydrodynamics coupled with the Maxwell's equations have been employed to find the nonlinear response of electrons in the piezoelectric semiconductor. The analysis is carried out through the derivation of the nonlinear dispersion relation for the four-wave modulational instability. An expression for the growth rate of the instability including the quantum effect due to Bohm potential has been obtained from the nonlinear dispersion relation. The quantum effect is observed to play a vital role in the four-wave scattering process. For a particular set of parameters, the quantum effect enhances the growth rate of the modulational instability by 37% compared to the growth rate predicted by the classical theory.

Amin, M. R. [Department of Electronics and Communications Engineering, East West University, 43 Mohakhali, Dhaka 1212 (Bangladesh)

2010-01-15

395

arXiv:quant-ph/0407264v130Jul2004 Effects of decoherence and imperfections for quantum algorithms A.A. Pomeransky1  

E-print Network

, which modifies strongly the hardware properties of realistic quantum computer [4]. The effects of static allows to obtain a significant gain in the accuracy of quantum computations. Keywords: Imperfections, quantum chaos, random matrix theory, quantum error correction In realistic quantum computations [1

Shepelyansky, Dima

396

First-principle study of quantum confinement effect on small sized silicon quantum dots using density-functional theory  

NASA Astrophysics Data System (ADS)

Density functional theory (DFT), as a first-principle approach has successfully been implemented to study nanoscale material. Here, DFT by numerical basis-set was used to study the quantum confinement effect as well as electronic properties of silicon quantum dots (Si-QDs) in ground state condition. Selection of quantum dot models were studied intensively before choosing the right structure for simulation. Next, the computational result were used to examine and deduce the electronic properties and its density of state (DOS) for 14 spherical Si-QDs ranging in size up to 2 nm in diameter. The energy gap was also deduced from the HOMO-LUMO results. The atomistic model of each silicon QDs was constructed by repeating its crystal unit cell of face-centered cubic (FCC) structure, and reconstructed until the spherical shape obtained. The core structure shows tetrahedral (Td) symmetry structure. It was found that the model need to be passivated, and hence it was noticed that the confinement effect was more pronounced. The model was optimized using Quasi-Newton method for each size of Si-QDs to get relaxed structure before it was simulated. In this model the exchange-correlation potential (Vxc) of the electrons was treated by Local Density Approximation (LDA) functional and Perdew-Zunger (PZ) functional.

Anas, M. M.; Othman, A. P.; Gopir, G.

2014-09-01

397

Warm target recoil ion momentum spectroscopy for fragmentation of molecular hydrogen by ultrashort laser pulses.  

PubMed

We demonstrate warm target recoil ion momentum spectroscopy for the fragmentation dynamics of the warm hydrogen molecules at room temperature. The thermal movement effect of the warm molecule is removed by using a correction algorithm in the momentum space. Based on the reconstructed three-dimensional momentum vectors as well as the kinetic energy release spectra, different vibrational states of the H(2)(+) ground state are clearly visible and the internuclear separation for charge resonance enhanced ionization of the second electron is identified. The results show adequate accordance with the former experiments using other techniques. PMID:19654636

Liu, Jia; Wu, Jian; Czasch, Achim; Zeng, Heping

2009-07-20

398

Nuclear quantum effect and temperature dependency on the hydrogen-bonded structure of base pairs.  

PubMed

The structure of Watson-Crick-type adenine-thymine and guanine-cytosine pairs has been studied by hybrid Monte Carlo (HMC) and path integral hybrid Monte Carlo (PIHMC) simulations with the use of semiempirical PM6-DH+ method in the gas phase. We elucidated the nuclear quantum effect and temperature dependency on the hydrogen-bonded moiety of base pairs. It was shown that the contribution of nuclear quantum effect on the hydrogen-bonded structure is significant not only at low temperature 150 K but also at temperature as high as 450 K. The relative position of hydrogen-bonded proton between two heavy atoms and the nuclear quantum nature of the proton are also shown. Furthermore, we have applied principal component analysis to HMC and PIHMC simulations to analyze the nuclear quantum effect on intermolecular motions. We found that the ratio of Buckle mode (lowest vibrational mode from normal mode analysis) decreases due to the nuclear quantum effect, whereas that of Propeller mode (second lowest vibrational mode) increases. In addition, nonplanar structures of base pairs were found to become stable due to the nuclear quantum effect from two-dimensional free energy landscape along Buckle and Propeller modes. PMID:23913712

Daido, Masashi; Kawashima, Yukio; Tachikawa, Masanori

2013-10-30

399

Effective Field Theory for Quantum Liquid in Dwarf Stars  

E-print Network

An effective field theory approach is used to describe quantum matter at greater-than-atomic but less-than-nuclear densities which are encountered in white dwarf stars. We focus on the density and temperature regime for which charged spin-0 nuclei form an interacting charged Bose-Einstein condensate, while the neutralizing electrons form a degenerate fermi gas. After a brief introductory review, we summarize distinctive properties of the charged condensate, such as a mass gap in the bosonic sector as well as gapless fermionic excitations. Charged impurities placed in the condensate are screened with great efficiency, greater than in an equivalent uncondensed plasma. We discuss a generalization of the Friedel potential which takes into account bosonic collective excitations in addition to the fermionic excitations. We argue that the charged condensate could exist in helium-core white dwarf stars and discuss the evolution of these dwarfs. Condensation would lead to a significantly faster rate of cooling than that of carbon- or oxygen-core dwarfs with crystallized cores. This prediction can be tested observationally: signatures of charged condensation may have already been seen in the recently discovered sequence of helium-core dwarfs in the nearby globular cluster NGC 6397. Sufficiently strong magnetic fields can penetrate the condensate within Abrikosov-like vortices. We find approximate analytic vortex solutions and calculate the values of the lower and upper critical magnetic fields at which vortices are formed and destroyed respectively. The lower critical field is within the range of fields observed in white dwarfs, but tends toward the higher end of this interval. This suggests that for a significant fraction of helium-core dwarfs, magnetic fields are entirely expelled within the core.

Gregory Gabadadze; Rachel A. Rosen

2009-12-29

400

Tunable optical Kerr effects of DNAs coupled to quantum dots  

PubMed Central

The coupling between DNA molecules and quantum dots can result in impressive nonlinear optical properties. In this paper, we theoretically demonstrate the significant enhancement of Kerr coefficient of signal light using optical pump-probe technique when the pump-exciton detuning is zero, and the probe-exciton detuning is adjusted properly to the frequency of DNA vibration mode. The magnitude of optical Kerr coefficient can be tuned by modifying the intensity of the pump beam. It is shown clearly that this phenomenon cannot occur without the DNA-quantum dot coupling. The present research will lead us to know more about the anomalous nonlinear optical behaviors in the hybrid DNA-quantum dot systems, which may have potential applications in the fields such as DNA detection. PMID:23194282

2012-01-01

401

Photostimulated Radio Electrical Longitudinal Effect in a Parabolic Quantum Well  

NASA Astrophysics Data System (ADS)

The longitudinal radioelectrical efffect in a parabolic quantum well (PQW) has been studied, based on the quantum kinetic equation for electrons under the action of a linearly polarized electromagnetic wave (EMW) and an intense laser field. Analytic expressions for the density of the current associated with the drag of charge carriers for the case of electron optical phonon scattering is calculated. The dependence of the current density on the intensity F and the frequency O of the laser radiation field, the frequency ? of the linearly polarized EMW field, the frequency of the parabolic potential, the temperature T of the system are obtained. The analytic expressions are numerically evaluated and plotted for a specific quantum wells, GaAs/AlGaAs. All the results of PQW are compared with semiconductors builk and superlattice shows that the difference.

Hung, Bui Duc; Thi Thanh Nhan, Nguyen; Quang Bau, Nguyen; Nhan, Nguyen Vu

2014-09-01

402

Measurements of scintillation efficiency and pulse shape for low energy recoils in liquid xenon  

NASA Astrophysics Data System (ADS)

Results of observations of low energy nuclear and electron recoil events in liquid xenon scintillator detectors are given. The relative scintillation efficiency for nuclear recoils is /0.22+/-0.01 in the recoil energy range 40-70 keV. Under the assumption of a single dominant decay component to the scintillation pulse shape the log-normal mean parameter T0 of the maximum likelihood estimator of the decay time constant for 6 keV recoil events is equal to /21.0+/-0.5 ns. It is observed that for electron recoils T0 rises slowly with energy, having a value /~30 ns at Eee~15 keV. Electron and nuclear recoil pulse shapes are found to be well fitted by single exponential functions although some evidence is found for a double exponential form for the nuclear recoil pulse shape.

Akimov, D.; Bewick, A.; Davidge, D.; Dawson, J.; Howard, A. S.; Ivaniouchenkov, I.; Jones, W. G.; Joshi, J.; Kudryavtsev, V. A.; Lawson, T. B.; Lebedenko, V.; Lehner, M. J.; Lightfoot, P. K.; Liubarsky, I.; Lscher, R.; McMillan, J. E.; Peak, C. D.; Quenby, J. J.; Spooner, N. J. C.; Sumner, T. J.; Tovey, D. R.; Ward, C. K.

2002-01-01

403

Observation of the Kondo effect in a spin-3/2 hole quantum dot  

SciTech Connect

We report the observation of the Kondo effect in a spin-3/2 hole quantum dot formed near pinch-off in a GaAs quantum wire. We clearly observe two distinctive hallmarks of quantum dot Kondo physics. First, the zero-bias peak in the differential conductance splits an in-plane magnetic field and the splitting is independent of gate voltage. Second, the splitting rate is twice as large as that for the lowest one-dimensional subband. We show that the Zeeman splitting of the zero-bias peak is highly anisotropic and attribute this to the strong spin-orbit interaction for holes in GaAs.

Klochan, O.; Micolich, A. P.; Hamilton, A. R. [School of Physics, University of New South Wales, Sydney NSW 2052 (Australia); Trunov, K.; Reuter, D.; Wieck, A. D. [Angewandte Festkrperphysik, Ruhr-Universitt Bochum, D-44780 Bochum (Germany)

2013-12-04

404

Electric field engineering using quantum-size-effect-tuned heterojunctions  

NASA Astrophysics Data System (ADS)

A quantum junction solar cell architecture was recently reported that employs colloidal quantum dots (CQDs) on each side of the p-n junction. This architecture extends the range of design opportunities for CQD photovoltaics, since the bandgap can be tuned across the light-absorbing semiconductor layer via control over CQD size, employing solution-processed, room-temperature fabricated materials. We exploit this feature by designing and demonstrating a field-enhanced heterojunction architecture. We optimize the electric field profile within the solar cell through bandgap engineering, thereby improving carrier collection and achieving an increased open circuit voltage, resulting in a 12% improvement in power conversion efficiency.

Adinolfi, V.; Ning, Z.; Xu, J.; Masala, S.; Zhitomirsky, D.; Thon, S. M.; Sargent, E. H.

2013-07-01

405

Quantum-squeezing effects of strained multilayer graphene NEMS  

PubMed Central

Quantum squeezing can improve the ultimate measurement precision by squeezing one desired fluctuation of the two physical quantities in Heisenberg relation. We propose a scheme to obtain squeezed states through graphene nanoelectromechanical system (NEMS) taking advantage of their thin thickness in principle. Two key criteria of achieving squeezing states, zero-point displacement uncertainty and squeezing factor of strained multilayer graphene NEMS, are studied. Our research promotes the measured precision limit of graphene-based nano-transducers by reducing quantum noises through squeezed states. PMID:21711882

2011-01-01

406

Directed percolation effects emerging from superadditivity of quantum networks  

NASA Astrophysics Data System (ADS)

Entanglement-induced nonadditivity of classical communication capacity in networks consisting of quantum channels is considered. Communication lattices consisting of butterfly-type entanglement-breaking channels augmented, with some probability, by identity channels are analyzed. The capacity superadditivity in the network is manifested in directed correlated bond percolation which we consider in two flavors: simply directed and randomly oriented. The obtained percolation properties show that high-capacity information transfer sets in much faster in the regime of superadditive communication capacity than otherwise possible. As a by-product, this sheds light on a type of entanglement-based quantum capacity percolation phenomenon.

Czekaj, L.; Chhajlany, R. W.; Horodecki, P.

2012-03-01

407

Numerical simulations of a loop quantum cosmos: robustness of the quantum bounce and the validity of effective dynamics  

E-print Network

A key result of isotropic loop quantum cosmology is the existence of a quantum bounce which occurs when the energy density of the matter field approaches a universal maximum close to the Planck density. Though the bounce has been exhibited in various matter models, due to severe computational challenges some important questions have so far remained unaddressed. These include the demonstration of the bounce for widely spread states, its detailed properties for the states when matter field probes regions close to the Planck volume and the reliability of the continuum effective spacetime description in general. In this manuscript we rigorously answer these questions using the Chimera numerical scheme for the isotropic spatially flat model sourced with a massless scalar field. We show that as expected from an exactly solvable model, the quantum bounce is a generic feature of states even with a very wide spread, and for those which bounce much closer to the Planck volume. We perform a detailed analysis of the depa...

Diener, Peter; Singh, Parampreet

2014-01-01

408

Electron-pair correlations seen by recoil-ion spectroscopy  

NASA Astrophysics Data System (ADS)

A fourth-order Wannier description of electron-pair escape (J. M. Feagin, J. Phys. B28, 1495 (1995)). has been extended to include non-zero total angular momentum. A key element of the description is the electron-pair center-of-mass momentum, which is fully represented by the momentum distribution of the recoiling ion. We have thus compared general and Wannier-theory predictions with recoil-ion measurements of electron-pair angular distributions following double-photoionization of helium. (R. Doerner, C. L. Cocke and J. M. Feagin, in preparation) Our approach and recent experimental results down to 1 eV above threshold will be presented. ^** Alexander von Humboldt Feodor Lynen Fellow.

Feagin, J. M.; Doerner, R.; Cocke, C. L.

1996-05-01

409

Aharonov-Bohm interference in quantum ring exciton: effects of built-in electric fields  

Microsoft Academic Search

We report a comprehensive discussion of quantum interference effects due to\\u000athe finite structure of excitons in quantum rings and their first experimental\\u000acorroboration observed in the optical recombinations. Anomalous features that\\u000aappear in the experiments are analyzed according to theoretical models that\\u000adescribe the modulation of the interference pattern by temperature and built-in\\u000aelectric fields.

M. D. Teodoro; V. L. Campo Jr.; V. Lopez-Richard; E. Marega Jr.; G. E. Marques; Y. Galvao-Gobato; F. Iikawa; M. J. S. P. Brasil; Z. Y. AbuWaar; V. G. Dorogan; Yu. I. Mazur; M. Benamara; G. J. Salamo

2009-01-01

410

Quantum dynamics of a kicked system with position-dependent effective mass  

NASA Astrophysics Data System (ADS)

The quantum dynamics of a complexified position-dependent effective-mass system is considered within the framework of the ?-function kicking perturbation. The absorptive/dissipative dynamics of the system exhibits energy crossing subject to different parametrization of space deformation upon time evolution, which is reminiscent of chaotic behavior in quantum systems. It is also observed a cross-over from ballistic dissipation to dynamic localization for decreasing perturbation strengths.

Vubangsi, M.; Tchoffo, M.; Fai, L. C.

2014-06-01

411

Scaling in the quantum Hall effect regime in n-InGaAs/GaAs nanostructures  

SciTech Connect

The longitudinal {rho}{sub xx}(B) and Hall {rho}{sub xy}(B) magnetoresistances are investigated experimentally in the integer quantum Hall effect (QHE) regime in n-InGaAs/GaAs double quantum well nanostructures in the range of magnetic fields B = (0-16) T and temperatures T = (0.05-70) K before and after IR illumination. The results are evaluated within the scaling hypothesis with regard to electron-electron interaction.

Arapov, Yu. G.; Gudina, S. V.; Klepikova, A. S.; Neverov, V. N., E-mail: neverov@imp.uran.ru; Novokshonov, S. G.; Kharus, G. I.; Shelushinina, N. G.; Yakunin, M. V. [Russian Academy of Sciences, Institute of Metal Physics, Ural Branch (Russian Federation)] [Russian Academy of Sciences, Institute of Metal Physics, Ural Branch (Russian Federation)

2013-07-15

412

Bilayer oscillation of subband effective masses in Pb/Ge(111) thin-film quantum wells  

NASA Astrophysics Data System (ADS)

Subband dispersions of quantum-well states in Pb thin films on Ge(111) have been measured with angle-resolved photoemission spectroscopy. The effective masses at the surface zone center exhibit a bilayer oscillation with thickness, in both magnitude and sign. This behavior is attributed to a strong interaction between Pb quantum-well subbands and the Ge valence maximum near the Fermi level, which occurs about every two monolayers.

Tang, S.-J.; Lee, Chang-Yeh; Huang, Chien-Chung; Chang, Tay-Rong; Cheng, Cheng-Maw; Tsuei, Ku-Ding; Jeng, H.-T.

2010-03-01

413

Nonlocal effects: relevance for the spontaneous emission rates of quantum emitters coupled to plasmonic structures  

E-print Network

The spontaneous emission rate of dipole emitters close to plasmonic dimers are theoretically studied within a nonlocal hydrodynamic model. A nonlocal model has to be used since quantum emitters in the immediate environment of a metallic nanoparticle probe its electronic structure. Compared to local calculations, the emission rate is significantly reduced. The influence is mostly pronounced if the emitter is located close to sharp edges. We suggest to use quantum emitters to test nonlocal effects in experimentally feasible configurations.

Filter, Robert; Toscano, Giuseppe; Lederer, Falk; Rockstuhl, Carsten

2014-01-01

414

Hamiltonian theory of the fractional quantum Hall effect: Conserving approximation for incompressible fractions  

Microsoft Academic Search

A microscopic Hamiltonian theory of the fractional quantum Hall effect developed by Shankar and the present author based on the fermionic Chern-Simons approach has recently been quite successful in calculating gaps and finite-tempertature properties in fractional quantum Hall states. Initially proposed as a small-q theory, it was subsequently extended by Shankar to form an algebraically consistent theory for all q

Ganpathy Murthy

2001-01-01

415

Nonlocal effects: relevance for the spontaneous emission rates of quantum emitters coupled to plasmonic structures  

NASA Astrophysics Data System (ADS)

The spontaneous emission rate of dipole emitters close to plasmonic dimers are theoretically studied within a nonlocal hydrodynamic model. A nonlocal model has to be used since quantum emitters in the immediate environment of a metallic nanoparticle probe its electronic structure. Compared to local calculations, the emission rate is significantly reduced. The influence is mostly pronounced if the emitter is located close to sharp edges. We suggest to use quantum emitters to test nonlocal effects in experimentally feasible configurations.

Filter, Robert; Bsel, Christoph; Toscano, Giuseppe; Lederer, Falk; Rockstuhl, Carsten

2014-11-01

416

Magnet field sensing beyond the standard quantum limit under the effect of decoherence  

Microsoft Academic Search

Entangled states can potentially be used to outperform the standard quantum\\u000alimit which every classical sensor is bounded by. However, entangled states are\\u000avery susceptible to decoherence, and so it is not clear whether one can really\\u000acreate a superior sensor to classical technology via a quantum strategy which\\u000ais subject to the effect of realistic noise. This paper presents

Yuichiro Matsuzaki; Simon C. Benjamin; Joseph Fitzsimons

2011-01-01

417

Advanced Quantum Mechanical Calculation of Superheavy Ions: Energy Levels, Radiation and Finite Nuclear Size Effects  

NASA Astrophysics Data System (ADS)

Advanced quantum approach to calculation of spectra for superheavy ions with an account of relativistic, correlation, nuclear, radiative effects is developed and based on the gauge invariant quantum electrodynamics (QED) perturbation theory (PT). The Lamb shift polarization part is calculated in the Ueling approximation, self-energy part is defined within a new non-PT procedure of Ivanov-Ivanova. Calculation results for energy levels, hyperfine structure parameters of some heavy elements ions are presented.

Glushkov, Alexander V.; Gurnitskaya, E. P.; Loboda, A. V.

2005-10-01

418

Quasiparticles in the theory of the integral quantum Hall effect (I)  

Microsoft Academic Search

We present the details of the single instanton solution and quantum fluctuations in the U(m + n)\\/U(m) U(n) non-linear sigma model. Special emphasis is given to the application to the integral quantum Hall effect (IQHE) and the peculiarities of the relevant limit of zero number of field components (m = n = 0) are discussed in detail. The present

Adrianus M. M. Pruisken

1987-01-01

419

Nuclear spin-lattice relaxation: A microscopic local probe for systems exhibiting the quantum Hall effect  

Microsoft Academic Search

Theory of magnetic quantum oscillations in the nuclear spin-lattice relaxation rate-T-11, in quasi-two-dimensional conductors at low temperatures and under strong magnetic fields, is presented. We show a close similarity between the magnetic field dependence of T-11 and that of rhoxx in the quantum Hall effect. The shape and the amplitude of the oscillations in T-11 depend strongly on band anisotropy,

I. D. Vagner; Tsofar Maniv

1988-01-01

420

The Ramsauer-Townsend Effect and the de Broglie-Bohm Quantum Mechanics  

Microsoft Academic Search

In this work we study the Ramsauer-Townsend effect.First, we use the Quantum\\u000aMechanical Formalism of Schrodinger. After, it is calculated with the Quantum\\u000aMechanical Formalism of de Broglie-Bohm. In this case, we use the Kostin\\u000aequation, taking into account the energy dissipation of the electrons scattered\\u000aby sharp edged potential wells.

J. M. F. Bassalo; P. T. S. Alencar; A. Nassar; M. Cattani

2009-01-01

421

Transport properties in the integer quantum Hall effect  

Microsoft Academic Search

In this thesis, I study the transport physics near the integer Quantum Hall plateau transitions. The central part of this work is the development and the implementation of a large scale numerical transfer matrix algorithm for calculation of the conductance. Combined with the technique of finite size scaling, it enables the first study of mesoscopic transport behavior in systems large

Bozidar Jovanovic

1999-01-01

422

Room-Temperature Quantum Hall Effect in Graphene  

E-print Network

, has been attracting intense interest since its dis- covery in 1980 (1). The QHE, exclusive to two understanding of inter- acting systems. It has also led to the establish- ment of a new metrological standard metrology at room, or at least liquid-nitrogen, temperatures. More robust quantum states, im- plied

Kim, Philip

423

Quantum Metrology  

Microsoft Academic Search

We point out a general framework that encompasses most cases in which quantum effects enable an increase in precision when estimating a parameter (quantum metrology). The typical quantum precision enhancement is of the order of the square root of the number of times the system is sampled. We prove that this is optimal, and we point out the different strategies

Vittorio Giovannetti; Seth Lloyd; Lorenzo Maccone

2006-01-01

424

Recoiling Supermassive Black Holes: A Search in the Nearby Universe  

NASA Astrophysics Data System (ADS)

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 (lsim 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.

Lena, D.; Robinson, A.; Marconi, A.; Axon, D. J.; Capetti, A.; Merritt, D.; Batcheldor, D.

2014-11-01

425

Time-of-flight direct recoil ion scattering spectrometer  

DOEpatents

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.

Krauss, A.R.; Gruen, D.M.; Lamich, G.J.

1994-09-13

426

Time-of-flight direct recoil ion scattering spectrometer  

DOEpatents

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).

Krauss, Alan R. (Naperville, IL); Gruen, Dieter M. (Downers Grove, IL); Lamich, George J. (Orland Park, IL)

1994-01-01

427

Recoil-gated plunger lifetime measurements in 188Pb  

Microsoft Academic Search

Electromagnetic transition probabilities were measured using the recoil distance Doppler-shift technique and the 40Ca(152Sm,4n)188Pb reaction at a beam energy of 805 MeV to investigate shape coexistence in 188Pb. For the first time, a plunger was combined with Gammasphere and the Argonne Fragment Mass Analyzer. It was possible to measure the lifetimes of two states in the prolate band of 188Pb

A. Dewald; R. Peusquens; B. Saha; P. von Brentano; A. Fitzler; T. Klug; I. Wiedenhver; Carpenter M; A. Heinz; R. V. Janssens; F. G. Kondev; C. J. Lister; D. Seweryniak; K. Abu Saleem; R. Krcken; J. R. Cooper; C. J. Barton; K. Zyromski; C. W. Beausang; Z. Wang; P. Petkov; A. M. Oros-Peusquens; U. Garg; S. Zhu

2003-01-01

428

Recent results and status of the HRIBF recoil mass spectrometer  

Microsoft Academic Search

The newly commissioned Recoil Mass Spectrometer (RMS) at the Holifield Radioactive Ion Beam Facility combines a momentum separator with a mass spectrometer to provide good mass separation of reaction products with excellent beam rejection even when using inverse reactions. With large acceptances in solid angle (30x110 mrad^2), energy ( 10%), and mass-to-charge ratio (4.9%), the RMS can typically resolve masses

C. J. Gross

1997-01-01

429

Measurement of capture reactions with the recoil mass spectrometer DRAGON  

Microsoft Academic Search

DRAGON is a state-of-the-art recoil mass spectrometer located at the radioactive beam facility ISAC at TRIUMF in Vancouver\\/Canada. It is designed to measure proton and alpha-capture reactions of light nuclei in inverse kinematics. In the last few years several astrophysically important reactions have been successfully measured, among them ^21Na(p,gamma)^22Mg and ^26gAl(p,gamma)^27Si using the high intensity radioactive beams available at ISAC.

Christof Vockenhuber

2006-01-01

430

Recoil Polarization Measurements of the Proton Electromagnetic Form Factor Ratio to High Momentum Transfer  

SciTech Connect

The electromagnetic form factors of the nucleon characterize the effect of its internal structure on its response to an electromagnetic probe as studied in elastic electronnucleon scattering. These form factors are functions of the squared four-momentum transfer Q2 between the electron and the proton. The two main classes of observables of this reaction are the scattering cross section and polarization asymmetries, both of which are sensitive to the form factors in different ways. When considering large f momentum transfers, double-polarization observables offer superior sensitivity to the electric form factor. This thesis reports the results of a new measurement of the ratio of the electric and magnetic form factors of the proton at high momentum transfer using the recoil polarization technique. A polarized electron beam was scattered from a liquid hydrogen target, transferring polarization to the recoiling protons. These protons were detected in a magnetic spectrometer which was used to reconstruct their kinematics, including their scattering angles and momenta, and the position of the interaction vertex. A proton polarimeter measured the polarization of the recoiling protons by measuring the azimuthal asymmetry in the angular distribution of protons scattered in CH2 analyzers. The scattered electron was detected in a large acceptance electromagnetic calorimeter in order to suppress inelastic backgrounds. The measured ratio of the transverse and longitudinal polarization components of the scattered proton is directly proportional to the ratio of form factors GpE=GpM. The measurements reported in this thesis took place at Q2 =5.2, 6.7, and 8.5 GeV2, and represent the most accurate measurements of GpE in this Q2 region to date.

Andrew Puckett

2010-02-01

431

Impurity effects on the Aharonov-Bohm optical signatures of neutral quantum-ring magnetoexcitons  

E-print Network

Impurity effects on the Aharonov-Bohm optical signatures of neutral quantum-ring magnetoexcitons L to the long-studied Aharonov-Bohm effect (ABE).1 This effect is specially important if the particle with experimen- tally accessible characteristics. The optical manifestations of such excitonic Aharonov- Bohm

Dias, Luis Gregório

432

Applied quantum mechanics 1 Applied Quantum Mechanics  

E-print Network

Applied quantum mechanics 1 Applied Quantum Mechanics Chapter 5 problems LAST NAME FIRST NAME #12 with the effective electron mass at the band edges. #12;Applied quantum mechanics 3 (c) Write a computer program

Levi, Anthony F. J.

433

Applied quantum mechanics 1 Applied Quantum Mechanics  

E-print Network

Applied quantum mechanics 1 Applied Quantum Mechanics Chapter 8 problems LAST NAME FIRST NAME #12;Applied quantum mechanics 3 (b) If the electron is in a semiconductor and has an effective mass m * 0.07 m

Levi, Anthony F. J.

434

Measurement of the response of heat-and-ionization germanium detectors to nuclear recoils  

E-print Network

The heat quenching factor Q' (the ratio of the heat signals produced by nuclear and electron recoils of equal energy) of the heat-and-ionization germanium bolometers used by the EDELWEISS collaboration has been measured. It is explained how this factor affects the energy scale and the effective quenching factor observed in calibrations with neutron sources. This effective quenching effect is found to be equal to Q/Q', where Q is the quenching factor of the ionization yield. To measure Q', a precise EDELWEISS measurement of Q/Q' is combined with values of Q obtained from a review of all available measurements of this quantity in tagged neutron beam experiments. The systematic uncertainties associated with this method to evaluate Q' are discussed in detail. For recoil energies between 20 and 100 keV, the resulting heat quenching factor is Q' = 0.91+-0.03+-0.04, where the two errors are the contributions from the Q and Q/Q' measurements, respectively. The present compilation of Q values and evaluation of Q' represent one of the most precise determinations of the absolute energy scale for any detector used in direct searches for dark matter.

A. Benoit; L. Berge; J. Blumer; A. Broniatowski; B. Censier; A. Chantelauze; M. /Chapellier; G. Chardin; S. Collin; X. Defay; M. De Jesus; H. Deschamps; P. Di Stefano; Y. Dolgorouky; L. Dumoulin; K. Eitel; M. Fesquet; S. Fiorucci; J. Gascon; G. Gerbier; C. Goldbach; M. Gros; M. Horn; A. Juillard; R. Lemrani; A. de Lesquen; M. Luca; S. Marnieros; L. Mosca; X. -F. Navick; G. Nollez; E. Olivieri; P. Pari; V. Sanglard; L. Schoeffel; F. Schwamm; M. Stern

2006-07-21

435

Quantum optical effective-medium theory for loss-compensated metamaterials  

E-print Network

A central aim in metamaterial research is to engineer sub-wavelength unit cells that give rise to desired effective-medium properties and parameters, such as a negative refractive index. Ideally one can disregard the details of the unit cell and employ the effective description instead. A popular strategy to compensate for the inevitable losses in metallic components of metamaterials is to add optical gain material. Here we study the quantum optics of such loss-compensated metamaterials at frequencies for which effective parameters can be unambiguously determined. We demonstrate that the usual effective parameters are insufficient to describe the propagation of quantum states of light. Furthermore, we propose a quantum-optical effective-medium theory instead and show that it correctly predicts the properties of the light emerging from loss-compensated metamaterials.

Ehsan Amooghorban; N. Asger Mortensen; Martijn Wubs

2012-08-02

436

Nuclear recoil energy spectrum of finite-sized dark matter  

NASA Astrophysics Data System (ADS)

Research has shown that direct dark matter detection experiments can distinguish between pointlike and finite-sized dark-matter candidates, both of which are of theoretical interests. In particular, there is an additional form factor in the typical cross section of finite-sized dark matter, causing the nuclear recoil energy spectrum of finite-sized dark matter to decrease more rapidly with the recoil energy than that of pointlike dark matter. Since the spectrum of finite-sized dark matter peaks below 1 keV, which is the common experimental threshold, and falls off rapidly at higher energies, detector with sub-keV threshold is necessary. The current goal of TEXONO-CDEX research program, on the studies of low energy neutrino and dark matter physics at Kuo-Sheng Reactor Neutrino Laboratory and China Jin-Ping Underground Laboratory, is to open the sub-keV detector window with germanium detectors. This work derives a model-independent, theoretical prediction of the nuclear recoil energy spectrum of finite-sized dark matter and is working toward using the predicted spectrum to analyze the experimental data of TEXONO-CDEX, in hope to substantiate or rule out dark matter candidates.

Chen, Anffany

2012-10-01

437

The recoil proton polarization in. pi. p elastic scattering  

SciTech Connect

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.

Seftor, C.J.

1988-09-01

438

Quantum-mechanical aspects of free-electron lasers  

SciTech Connect

A 2-D quantum theory of the Free Electron Laser (FEL) has been developed based on the solutions of Dirac equation for the motion of electrons moving in various wiggler geometries, uniform, tapered and enhanced by an axial guide field. It is shown that these solutions can be written in terms of Mathieu functions of fractional order. Using these solutions a perturbational analysis is carried out to calculate the frequencies and the gain of the FEL in each magnet configuration. Finally, an optical model for the FEL interaction is developed to explain the saturation behavior and the short-pulse effects such as Laser Lethargy. The quantum-mechanical effects due to transverse momentum correction were {gamma} (Lorentz factor) times larger than the quantum recoil and spin effects, therefore important for short-wavelength FELs. These quantum-mechanical effects cause a broadening in the spontaneous emission line shape, a decrease in gain and an increase in the rate of harmonic frequency generation. In the presence of an axial field, gain is increased, harmonic frequency rate is reduced, and Dirac solutions exhibit instability. The optical model developed correctly predicts the oscillator rise time and uses a simpler algorithm to calculate the nonlinear saturation behavior.

Saritepe, S.

1988-01-01

439

Tunneling of the 3rd Kind: A Test of the Effective Non-locality of Quantum Field Theory  

E-print Network

Integrating out virtual quantum fluctuations in an originally local quantum field theory results in an effective theory which is non-local. In this Letter we argue that tunneling of the 3rd kind - where particles traverse a barrier by splitting into a pair of virtual particles which recombine only after a finite distance - provides a direct test of this non-locality. We sketch a quantum-optical setup to test this effect, and investigate observable effects in a simple toy model.

Simon A. Gardiner; Holger Gies; Joerg Jaeckel; Chris J. Wallace

2012-04-21

440

Effect of quantum dot position and background doping on the performance of quantum dot enhanced GaAs solar cells  

NASA Astrophysics Data System (ADS)

The effect of the position of InAs quantum dots (QD) within the intrinsic region of pin-GaAs solar cells is reported. Simulations suggest placing the QDs in regions of reduced recombination enables a recovery of open-circuit voltage (VOC). Devices with the QDs placed in the center and near the doped regions of a pin-GaAs solar cell were experimentally investigated. While the VOC of the emitter-shifted device was degraded, the center and base-shifted devices exhibited VOC comparable to the baseline structure. This asymmetry is attributed to background doping which modifies the recombination profile and must be considered when optimizing QD placement.

Driscoll, Kristina; Bennett, Mitchell F.; Polly, Stephen J.; Forbes, David V.; Hubbard, Seth M.

2014-01-01

441

The quantum percolation model of the scaling theory of the quantum Hall effect: a unifying model for plateau-to-plateau transitions  

NASA Astrophysics Data System (ADS)

We present a unifying model of plateau-to-plateau transitions in the quantum Hall effect based on results from high resolution frequency scaling experiments. We show that as the frequency or quantum coherence length of the two-dimensional electron system is varied, one observes a crossover between classical percolation and quantum percolation in the measured values of the critical scaling exponents of the plateau-to-plateau transitions. This crossover is dependent on the relationship between certain relevant length scales of a two-dimensional system and can be explained using a quantum percolation model. The model explains why quantum criticality can be observed in some systems, but is absent from others.

Dodoo-Amoo, N. A.; Saeed, K.; Li, L. H.; Linfield, E. H.; Davies, A. G.; Cunningham, J. E.

2013-08-01

442

Simulations of shocked methane including self-consistent semiclassical quantum nuclear effects.  

PubMed

A methodology is described for atomistic simulations of shock-compressed materials that incorporates quantum nuclear effects on the fly. We introduce a modification of the multiscale shock technique (MSST) that couples to a quantum thermal bath described by a colored noise Langevin thermostat. The new approach, which we call QB-MSST, is of comparable computational cost to MSST and self-consistently incorporates quantum heat capacities and Bose-Einstein harmonic vibrational distributions. As a first test, we study shock-compressed methane using the ReaxFF potential. The Hugoniot curves predicted from the new approach are found comparable with existing experimental data. We find that the self-consistent nature of the method results in the onset of chemistry at 40% lower pressure on the shock Hugoniot than observed with classical molecular dynamics. The temperature shift associated with quantum heat capacity is determined to be the primary factor in this shift. PMID:23013329

Qi, Tingting; Reed, Evan J

2012-10-25

443

Generalized decoding, effective channels, and simplified security proofs in quantum key distribution  

SciTech Connect

Prepare and measure quantum key distribution protocols can be decomposed into two basic steps: delivery of the signals over a quantum channel and distillation of a secret key from the signal and measurement records by classical processing and public communication. Here we formalize the distillation process for a general protocol in a purely quantum-mechanical framework and demonstrate that it can be viewed as creating an 'effective' quantum channel between the legitimate users Alice and Bob. The process of secret key generation can then be viewed as entanglement distribution using this channel, which enables application of entanglement-based security proofs to essentially any prepare and measure protocol. To ensure secrecy of the key, Alice and Bob must be able to estimate the channel noise from errors in the key, and we further show how symmetries of the distillation process simplify this task. Applying this method, we prove the security of several key distribution protocols based on equiangular spherical codes.

Renes, Joseph M. [IAKS Prof. Beth, Arbeitsgruppe Quantum Computing, Universitaet Karlsruhe, Am Fasanengarten 5, D-76131 Karlsruhe (Germany); Quantum Information Theory Group, Institut fuer Theoretische Physik I, and Max-Planck-Forschungsgruppe, Institut fuer Optik, Information und Photonik, Universitaet Erlangen-Nuernberg, Staudtstrasse 7, D-91058 Erlangen (Germany); Grassl, Markus [IAKS Prof. Beth, Arbeitsgruppe Quantum Computing, Universitaet Karlsruhe, Am Fasanengarten 5, D-76131 Karlsruhe (Germany)

2006-08-15

444

Effective Field Theory of Gravity: Leading Quantum Gravitational Corrections to Newtons and Coulombs Law  

E-print Network

In this paper we consider general relativity and its combination with scalar quantum electrodynamics (QED) as an effective quantum field theory at energies well below the Planck scale. This enables us to compute the one-loop quantum corrections to the Newton and Coulomb potential induced by the combination of graviton and photon fluctuations. We derive the relevant Feynman rules and compute the nonanalytical contributions to the one-loop scattering matrix for charged scalars in the nonrelativistic limit. In particular, we derive the post-Newtonian corrections of order $Gm/\\text c^2 r$ from general relativity and the genuine quantum corrections of order $G\\hbar/\\text c^3 r^2$.

Sven Faller

2007-08-13

445

Non-equilibrium effects upon the non-Markovian Caldeira-Leggett quantum master equation  

NASA Astrophysics Data System (ADS)

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.

Bolivar, A. O.

2011-05-01

446

Black hole fireworks: quantum-gravity effects outside the horizon spark black to white hole tunneling  

E-print Network

We show that there is a classical metric satisfying the Einstein equations outside a finite spacetime region where matter collapses into a black hole and then emerges from a white hole. We compute this metric explicitly. We show how quantum theory determines the (long) time for the process to happen. A black hole can thus quantum-tunnel into a white hole. For this to happen, quantum gravity should affect the metric also in a small region outside the horizon: we show that contrary to what is commonly assumed, this is not forbidden by causality or by the semiclassical approximation, because quantum effects can pile up over a long time. This scenario alters radically the discussion on the black hole information puzzle.

Hal M. Haggard; Carlo Rovelli

2014-07-03

447

External magnetic field on the thermoelectric and thermospin effect in a quantum dot  

NASA Astrophysics Data System (ADS)

The interactions of spin angular momentum and the external magnetic field in a quantum dot coupled to ferromagnetic lead have been considered here. The results show that the magnetic moment of spin precession caused by the direction of the external field changing could be used to adjust the coulomb gaps of quantum dots, and to control thermal-to-electron conversion efficiency or thermal-to-spin transformation efficiency. When the polarized directions of the ferromagnetic leads are opposite, it is possible to obtain a better thermal spin quality factor. So the system symmetry and Coulomb blockade effect limit the spin current of a quantum dot system. Our results are important to the design of quantum dot devices.

Liu, Jia; Cheng, Jie; Wang, Song