We present a criterion that determines whether a fermionic state is a convex combination of pure Gaussian states. This criterion is complete and characterizes the set of convex-Gaussian states from the inside. If a state passes a program it is a convex-Gaussian state and any convex-Gaussian state ca...

[Phys. Rev. A 90, 062329] Published Fri Dec 19, 2014

]]>We propose a two-step approach to realize a multiqubit phase gate in circuit QED beyond the rotating-wave approximation. The multiqubit gate can be implemented in a few nanoseconds, which is much faster than that under the rotating-wave approximation. Also the operation time of the gate is independe...

[Phys. Rev. A 90, 062330] Published Fri Dec 19, 2014

]]> We present spectra of ultracold ^{7}Li^{85}Rb molecules in their electronic ground state formed by spontaneous decay of weakly bound photoassociated molecules. Beginning with atoms in a dual-species magneto-optical trap, weakly bound molecules are formed in the 4(1) electronic state, which corresponds to ...

[Phys. Rev. A 90, 062513] Published Fri Dec 19, 2014

]]>Fully relativistic calculations are presented for the double K-shell photoionization cross section for several neutral medium-Z atoms, from magnesium (Z=10) up to silver (Z=47). The calculations take into account all multipoles of the absorbed photon as well as the retardation of the electron-electr...

[Phys. Rev. A 90, 063422] Published Fri Dec 19, 2014

]]>We investigate thermal relaxation of superfluid turbulence in a highly oblate Bose-Einstein condensate. We generate turbulent flow in the condensate by sweeping the center region of the condensate with a repulsive optical potential. The turbulent condensate shows a spatially disordered distribution ...

[Phys. Rev. A 90, 063627] Published Fri Dec 19, 2014

]]>We discuss singularities in the spectrum of driven many-body spin systems. In contrast to undriven models, the driving allows us to control the geometry of the quasienergy landscape. As a consequence, one can engineer singularities in the density of quasienergy states by tuning an external control. ...

[Phys. Rev. A 90, 063628] Published Fri Dec 19, 2014

]]>We investigate the mechanical instability toward density collapse and the transition temperature of Bose-Einstein condensation (BEC) in the weakly coupled boson-fermion many-body mixture of single-component boson and fermion gases, in the case of the repulsive boson-boson and attractive boson-fermio...

[Phys. Rev. A 90, 063629] Published Fri Dec 19, 2014

]]>The relativistic coupled-clusters method combined with the generalized relativistic effective core potential approach and nonvariational one-center restoration technique is applied to evaluation of parameters of the spin-rotational effective Hamiltonian in lead monofluoride to study the effects of v...

[Phys. Rev. A 90, 064501] Published Fri Dec 19, 2014

]]>We study a method of generating Bell inequalities by using group actions of single-generator Abelian groups. Two parties, Alice and Bob, each make one of M possible measurements on a system, with each measurement having K possible outcomes. The probabilities for the outcomes of these measurements ar...

[Phys. Rev. A 90, 062121] Published Thu Dec 18, 2014

]]>We analyze quantum states formed as superpositions of an initial pure product state and its image under local unitary evolution, using two measurement-based measures of superposition size: one based on the optimal quantum binary distinguishability of the branches of the superposition and another bas...

[Phys. Rev. A 90, 062122] Published Thu Dec 18, 2014

]]>We present an error analysis of various tomographic protocols based on the linear inversion for the reconstruction of an unknown two-qubit state. We solve the problem of finding a tomographic protocol which is the most robust against errors in terms of the lowest value (i.e., equal to 1) of a condit...

[Phys. Rev. A 90, 062123] Published Thu Dec 18, 2014

]]>We consider the quantum and local hidden variable (LHV) correlations obtained by measuring a pair of qubits by projections defined by randomly chosen axes separated by an angle θ. Local hidden variables predict binary colorings of the Bloch sphere with antipodal points oppositely colored. We prove B...

[Phys. Rev. A 90, 062124] Published Thu Dec 18, 2014

]]>Secure quantum key distribution with multimode Gaussian entangled states and multimode homodyne detectors is proposed. In general the multimode character of both the sources of entanglement and the homodyne detectors can cause a security break even for a perfect channel when trusted parties are unaw...

[Phys. Rev. A 90, 062326] Published Thu Dec 18, 2014

]]>Conditions to achieve an unusually strong Rydberg spin-exchange interaction are investigated and proposed as a means to generate pairwise entanglement and realize a swap-like quantum gate for neutral atoms. Ground-state entanglement is created by mapping entangled Rydberg states to ground states usi...

[Phys. Rev. A 90, 062327] Published Thu Dec 18, 2014

]]>In this paper, we propose feedback designs for manipulating a quantum state to a target state by performing sequential measurements. In light of Belavkin's quantum feedback control theory, for a given set of (projective or nonprojective) measurements and a given time horizon, we show that finding th...

[Phys. Rev. A 90, 062328] Published Thu Dec 18, 2014

]]>A combined basis of analytic Gaussian functions and grid-based finite element-discrete variable representation spherical harmonic expansion is specialized for the description of continuum electron dynamics in the presence of electrons held fixed in core molecular orbitals. The applicability of this ...

[Phys. Rev. A 90, 063421] Published Thu Dec 18, 2014

]]> We present a measurement of the branching fractions for decay from the long-lived 5D_{5/2} level in ^{138}Ba^{+}. The branching fraction for decay into the 6S_{1/2} ground state was found to be 0.846(25)_{stat}(4)_{sys}. We also report an improved measurement of the 5D_{5/2} lifetime, τ_{5D5/2}=31.2(0.9) s. Together these ...

[Phys. Rev. A 90, 060501] Published Wed Dec 17, 2014

]]>Anyonic systems are modeled by topologically protected Hilbert spaces which obey complex superselection rules restricting possible operations. These Hilbert spaces cannot be decomposed into tensor products of spatially localized subsystems, whereas the tensor product structure is a foundation of the...

[Phys. Rev. A 90, 062325] Published Wed Dec 17, 2014

]]>Relativistic calculations of the isotope shifts of energy levels in highly charged Li-like ions are performed. The nuclear recoil (mass shift) contributions are calculated by merging the perturbative and large-scale configuration-interaction Dirac-Fock-Sturm (CI-DFS) methods. The nuclear size (field...

[Phys. Rev. A 90, 062512] Published Wed Dec 17, 2014

]]> We investigate correlations between multiple ionization and fragmentation processes of the ethane molecule in collisions with 580-keV C^{+} ions under single-electron capture and loss conditions. Employing an electron counting technique, we directly obtain number distributions of ionized electrons, whi...

[Phys. Rev. A 90, 062711] Published Wed Dec 17, 2014

]]>The three-dimensional classical-trajectory Monte Carlo method is employed to investigate low-energy photoelectron spectra in above-threshold ionization by strong laser fields. By connecting the tunneling coordinates with the final momentum-energy spectra, we identify the effects of the Coulomb poten...

[Phys. Rev. A 90, 063420] Published Wed Dec 17, 2014

]]> Yin and Radzihovsky [X. Yin and L. Radzihovsky, Phys. Rev. A 88, 063611 (2013)PLRAAN10.1103/PhysRevA.88.063611] recently developed a self-consistent extension of a Bogoliubov theory, in which the condensate number density n_{c} is treated as a mean field that changes with time, in order to analyze a JI...

[Phys. Rev. A 90, 063626] Published Wed Dec 17, 2014

]]>We propose a direct readout of symmetry information in matter using nonlinear optics. From combinations of circularly and longitudinally polarized optical fields, we construct irreducible spherical field tensors for second- and third-order nonlinear processes. The coupling of these field tensors to ...

[Phys. Rev. A 90, 063827] Published Wed Dec 17, 2014

]]> We report the experimental observation of coherent population oscillation (CPO-) based light storage in an atomic vapor cell at room temperature. Using the ultranarrow CPO between the ground levels of a Λ system selected by polarization in metastable ^{4}He, such a light storage is experimentally shown...

[Phys. Rev. A 90, 061801] Published Tue Dec 16, 2014

]]>We consider the Landau-Zener problem for a two-level system (or qubit) when this system interacts with one harmonic oscillator mode that is initially set to a finite-temperature thermal equilibrium state. The oscillator could represent an external mode that is strongly coupled to the qubit, e.g., an...

[Phys. Rev. A 90, 062120] Published Tue Dec 16, 2014

]]>Photon antibunching is a quantum phenomenon typically observed in strongly nonlinear systems where photon blockade suppresses the probability of detecting two photons at the same time. Antibunching has also been reported with Gaussian states, where optimized amplitude squeezing yields classically fo...

[Phys. Rev. A 90, 063824] Published Tue Dec 16, 2014

]]>The possibility of the superradiant phase transition in polarizable materials described by the minimal-coupling Hamiltonian with the longitudinal dipole-dipole interaction is examined. We try to reduce the Hamiltonian into the Dicke one in the homogeneous and infinite case, and discuss the stability...

[Phys. Rev. A 90, 063825] Published Tue Dec 16, 2014

]]>We consider a system subject to a quantum optical master equation at finite temperature and study a class of conditional dynamics obtained by monitoring its totally or partially purified environment. More specifically, drawing from the notion that the thermal state of the environment may be regarded...

[Phys. Rev. A 90, 063826] Published Tue Dec 16, 2014

]]>Uncertainty relations provide fundamental limits on what can be said about the properties of quantum systems. For a quantum particle, the commutation relation of position and momentum observables entails Heisenberg's uncertainty relation. A third observable is presented which satisfies canonical com...

[Phys. Rev. A 90, 062118] Published Mon Dec 15, 2014

]]>We postulate the existence of a universal uncertainty relation between the quantum and classical mutual informations between pairs of quantum systems. Specifically, we propose that the sum of the classical mutual information, determined by two mutually unbiased pairs of observables, never exceeds th...

[Phys. Rev. A 90, 062119] Published Mon Dec 15, 2014

]]>In this paper we propose an expression for the entanglement entropy of several intervals in a stationary state of a free, translational invariant Hamiltonian in a fermionic chain. We check numerically the accuracy of our proposal and conjecture a formula for the asymptotic behavior of principal subm...

[Phys. Rev. A 90, 062321] Published Mon Dec 15, 2014

]]>In this paper we propose a scheme for the preparation of steady entanglements in bosonic dissipative networks. We describe its implementation in a system of coupled cavities interacting with an engineered reservoir built up of three-level atoms. Emblematic bipartite (Bell and NOON) and multipartite ...

[Phys. Rev. A 90, 062322] Published Mon Dec 15, 2014

]]>We prove that the projection on a completely entangled subspace S of maximum dimension obtained by Parthasarathy [K. R. Parthasarathy, Proc. Indian Acad. Sci. Math. Sci. 114, 365 (2004)PIAMDO10.1007/BF02829441] in a multipartite quantum system is not positive under partial transpose. We next show th...

[Phys. Rev. A 90, 062323] Published Mon Dec 15, 2014

]]>We consider measurement-based quantum computation that uses scalable continuous-variable cluster states with a one-dimensional topology. The physical resource, known here as the dual-rail quantum wire, can be generated using temporally multiplexed offline squeezing and linear optics or by using a si...

[Phys. Rev. A 90, 062324] Published Mon Dec 15, 2014

]]>We propose approximate kinetic energy (KE) functionals of the pair-density (PD)-functional theory on the basis of the rigorous expression with the coupling-constant integration (RECCI) that has been recently derived [Phys. Rev. A 85, 062508 (2012)PLRAAN10.1103/PhysRevA.85.062508]. These approximate ...

[Phys. Rev. A 90, 062511] Published Mon Dec 15, 2014

]]> We study the process of single ionization of Li in collisions with H^{+} and O^{8+} projectile ions at 6-MeV and 1.5-MeV/amu impact energies, respectively. Using the frameworks of the independent-electron model and the impact parameter picture, fully (FDCS) and doubly (DDCS) differential cross sections ar...

[Phys. Rev. A 90, 062710] Published Mon Dec 15, 2014

]]>Spin-orbit (SO) coupling can be introduced in a Bose-Einstein condensate (BEC) as a gauge potential acting only in a localized spatial domain. The effect of such a SO “defect” can be understood by transforming the system to the integrable vector model. The properties of the SO BEC change drastically...

[Phys. Rev. A 90, 063621] Published Mon Dec 15, 2014

]]>By applying complementary analytic and numerical methods, we investigate the dynamics of spin-1/2 XXZ models with variable-range interactions in arbitrary dimensions. The dynamics we consider is initiated from uncorrelated states that are easily prepared in experiments; it can be equivalently viewed...

[Phys. Rev. A 90, 063622] Published Mon Dec 15, 2014

]]>We investigate the thermodynamic properties of a superfluid Fermi gas subject to Rashba spin-orbit coupling and effective Zeeman field. We adopt a T-matrix scheme that takes beyond-mean-field effects, which are important for strongly interacting systems, into account. We focus on the calculation of ...

[Phys. Rev. A 90, 063623] Published Mon Dec 15, 2014

]]>We measure the collective excitation spectrum of a spin-orbit-coupled Bose-Einstein condensate using Bragg spectroscopy. The spin-orbit coupling is generated by Raman dressing of atomic hyperfine states. When the Raman detuning is reduced, mode softening at a finite momentum is revealed, which provi...

[Phys. Rev. A 90, 063624] Published Mon Dec 15, 2014

]]>A theoretical study of interacting bosons in a periodic optical lattice is presented. Instead of the commonly used tight-binding approach (applicable near the Mott-insulating regime of the phase diagram), the present work starts from the exact single-particle states of bosons in a cubic optical latt...

[Phys. Rev. A 90, 063625] Published Mon Dec 15, 2014

]]> We study the propagation of nanofiber-guided light through an array of atomic cesium, taking into account the transitions between the hyperfine levels 6S_{1/2}F=4 and 6P_{3/2}F^{′}=5 of the D_{2} line. We derive the coupled-mode propagation equation, the input-output equation, the scattering matrix, the transfe...

[Phys. Rev. A 90, 063816] Published Mon Dec 15, 2014

]]>Photoionization of a laser-cooled and compressed atomic beam from a high-flux thermal source can be used to create a high-brightness ion beam for use in focused-ion-beam instruments. Here we show using calculations and Doppler cooling simulations that an atomic rubidium beam with an equivalent brigh...

[Phys. Rev. A 90, 063817] Published Mon Dec 15, 2014

]]>A compact theoretical description for the dynamics of defect centers in crystals is provided in terms of a quantum optical master equation which includes spontaneous decay and a simplified vibronic interaction with lattice phonons.

[Phys. Rev. A 90, 063818] Published Mon Dec 15, 2014

]]>Here we demonstrate that photocurrent noise reduction below the standard quantum limit and modal anticorrelation can arise in a two-mode coupled vertical external cavity surface emitting laser system with a common pump. This effect occurs due to correlated loss of laser modes. It is possible to supp...

[Phys. Rev. A 90, 063819] Published Mon Dec 15, 2014

]]>We describe and quantify the emergence of coherence between quantum systems that are initially at thermal equilibrium. We show that the coherence can be induced by a conditional locking method based on a feasible joint detection of photons spontaneously emitted by the systems. The energy employed by...

[Phys. Rev. A 90, 063820] Published Mon Dec 15, 2014

]]> We present analytical solutions for the mean-field master equation of the driven-dissipative Bose-Hubbard model for cavity photons, in the limit of both weak pumping and weak dissipation. Instead of pure Mott-insulator states, we find statistical mixtures with the same second-order coherence g^{(2)}(0)...

[Phys. Rev. A 90, 063821] Published Mon Dec 15, 2014

]]>We study numerically the spectrum of the non-Hermitian effective Hamiltonian that describes the dipolar interaction of a gas of N≫1 atoms with the radiation field. We analyze the interplay between cooperative effects and disorder for both scalar and vectorial radiation fields. We show that for dense...

[Phys. Rev. A 90, 063822] Published Mon Dec 15, 2014

]]>We study the polarization properties of elliptical femtosecond-laser-written waveguide arrays. An analytical model is presented to explain the asymmetry of the spatial transverse profiles of linearly polarized modes in these waveguides. This asymmetry produces a polarization-dependent coupling coeff...

[Phys. Rev. A 90, 063823] Published Mon Dec 15, 2014

]]>The complementarity between time and energy, as well as between an angle and a component of angular momentum, is described at three different layers of understanding. The phenomena of super-resolution are readily apparent in the quantum phase representation which also reveals that entanglement is no...

[Phys. Rev. A 90, 062117] Published Fri Dec 12, 2014

]]>In this work we use the classical trajectory Monte Carlo method within an eight-electron scheme to theoretically study photonic spectra that follow charge-exchange processes between highly charged ions of charge states 10+, 17+, 18+, and 36+ with neutral argon. The energy range considered is 18 eV/a...

[Phys. Rev. A 90, 062708] Published Fri Dec 12, 2014

]]>Vortices are an inherent property of the velocity fields of complex, time-dependent, Schrödinger wave functions ψ occurring where both the real and the imaginary parts of ψ vanish. They have been known since the early work of Dirac on magnetic monopoles and have frequently been studied theoretically...

[Phys. Rev. A 90, 062709] Published Fri Dec 12, 2014

]]>[Phys. Rev. A 90, 060001] Published Thu Dec 11, 2014

]]>Kelvin probe force microscopy at normal pressure was performed by two different groups on the same Au-coated planar sample used to measure the Casimir interaction in a sphere-plane geometry. The obtained voltage distribution was used to calculate the separation dependence of the electrostatic pressu...

[Phys. Rev. A 90, 062115] Published Thu Dec 11, 2014

]]>The study of quantum systems evolving from initial states to distinguishable, orthogonal final states is important for information processing applications such as quantum computing and quantum metrology. However, for most unitary evolutions and initial states the system does not evolve to an orthogo...

[Phys. Rev. A 90, 062116] Published Thu Dec 11, 2014

]]>We propose a scheme that employs dissipation to deterministically generate entanglement in an ensemble of strongly interacting Rydberg atoms. With a combination of microwave driving between different Rydberg levels and a resonant laser coupling to a short-lived atomic state, the ensemble can be driv...

[Phys. Rev. A 90, 062319] Published Thu Dec 11, 2014

]]>Experimental implementation of the surface code will be a significant milestone for quantum computing. We develop a circuit and a decoder targeted for near-term implementation of a distance-3 surface code. We simulate the code under amplitude and phase damping and compare the threshold to a Pauli-tw...

[Phys. Rev. A 90, 062320] Published Thu Dec 11, 2014

]]>We consider nonadiabatic transitions in explicitly time-dependent systems with Hamiltonians of the form Ĥ(t)=Â+B̂t+Ĉ/t, where t is time and Â, B̂, Ĉ are Hermitian N×N matrices. We show that in any model of this type, scattering matrix elements satisfy nontrivial exact constraints that follow fr...

[Phys. Rev. A 90, 062509] Published Thu Dec 11, 2014

]]> Measurements of hyperfine polarization quantum beats are used to determine the magnetic dipole (A) and electric quadrupole (B) coupling constants in the excited atomic Cs 8p ^{2}P_{3/2} level. The experimental approach is a combination of pulsed optical pumping and time-delayed stimulated-emission probing...

[Phys. Rev. A 90, 062510] Published Thu Dec 11, 2014

]]> We demonstrate an efficient scheme for controlling the tunneling ionization of a H_{2}^{+} molecular ion. Our scheme is based on the idea that the tunneling ionization rate is highly dependent on the instantaneous magnitude of the electric field. By manipulating the relative phase of the synthesized 5-fs,...

[Phys. Rev. A 90, 063418] Published Thu Dec 11, 2014

]]> Near-threshold photodissociation of Br_{2} from a supersonic beam produces slow bromine atoms that are trapped in the magnetic-field minimum formed between two opposing permanent magnets. Here we quantify the dominant trap-loss rate due to collisions with two sources of residual gas: the background lim...

[Phys. Rev. A 90, 063419] Published Thu Dec 11, 2014

]]>We demonstrate that memory in an N-qubit system subjected to decoherence, is a potential resource for the slowdown of the entanglement decay. We show that this effect can be used to retain the sub-shot-noise sensitivity of the parameter estimation in quantum interferometry. We calculate quantum Fish...

[Phys. Rev. A 90, 063619] Published Thu Dec 11, 2014

]]>In this paper, we study an extended bosonic t-J model in an optical lattice, which describes two-component hard-core bosons with nearest-neighbor pseudospin interactions and, also, inter- and intraspecies dipole-dipole interactions. In particular, we focus on the case in which two-component hard-cor...

[Phys. Rev. A 90, 063620] Published Thu Dec 11, 2014

]]>We investigate how to model Markovian evolution of coupled harmonic oscillators, each of them interacting with a local environment. When the coupling between the oscillators is weak, dissipation may be modeled using local Lindblad terms for each of the oscillators in the master equation, as is commo...

[Phys. Rev. A 90, 063815] Published Thu Dec 11, 2014

]]>I investigate the extent to which the description of quantum systems by Gibbs states can be justified purely on the basis of tomographic data, without recourse to theoretical concepts such as infinite ensembles, environments, or information or to the systems' dynamics. I show that the use of Gibbs s...

[Phys. Rev. A 90, 062114] Published Wed Dec 10, 2014

]]>A quantum code is a subspace of a Hilbert space of a physical system chosen to be correctable against a given class of errors, where information can be encoded. Ideally, the quantum code lies within the ground space of the physical system. When the physical model is the Heisenberg ferromagnet in the...

[Phys. Rev. A 90, 062317] Published Wed Dec 10, 2014

]]>Spin-1 systems, in comparison to spin-1/2 systems, offer a better security for encoding and transferring quantum information, primarily due to their larger Hilbert spaces. Superconducting artificial atoms possess multiple energy levels, thereby being capable of emulating higher-spin systems. Here I ...

[Phys. Rev. A 90, 062318] Published Wed Dec 10, 2014

]]>It is possible to create and manipulate bound states in continuum in atom-atom cold collisions by lasers and a magnetic field, employing currently available techniques of photoaasociation and magnetic Feshbach resonance.

[Phys. Rev. A 90, 063417] Published Wed Dec 10, 2014

]]>A generalized formulation is presented for determining the saturation thresholds for optical processes excited by ultrafast pulses based on the pulse area of the excitation pulse. It is demonstrated that the threshold of driving-pulse intensity for absorption and fluorescence saturation in a two-lev...

[Phys. Rev. A 90, 063813] Published Wed Dec 10, 2014

]]>We propose a scheme for the remote preparation of entangled matter qubits in free space. For this purpose, a setup of two opposing parabolic mirrors is considered, each one with a single ion trapped at its focus. To get the required entanglement in this extreme multimode scenario, we take advantage ...

[Phys. Rev. A 90, 063814] Published Wed Dec 10, 2014

]]>We present a wave-function-based method to solve the time-dependent many-electron Schrödinger equation with special emphasis on strong-field ionization phenomena. The theory builds on the configuration-interaction (CI) approach supplemented by the generalized-active-space concept from quantum chemis...

[Phys. Rev. A 90, 062508] Published Tue Dec 09, 2014

]]>The spectral structure underlying excitonic energy transfer in ultracold Rydberg gases is studied numerically, in the framework of random matrix theory, and via self-consistent diagrammatic techniques. Rydberg gases are made up of randomly distributed, highly polarizable atoms that interact via stro...

[Phys. Rev. A 90, 063415] Published Tue Dec 09, 2014

]]>The tunneling ionization of an electron from a p state in a highly charged ion in the relativistic regime is investigated in a linearly polarized strong laser field. In contrast to the case of an s state, the tunneling ionization from the p state is spin asymmetric. We single out two reasons for the...

[Phys. Rev. A 90, 063416] Published Tue Dec 09, 2014

]]>A model of an atomic impurity immersed in a BEC trapped in a double-well potential is presented and the concept of fidelity susceptibility is used to calculate the critical exponents of the phase transition from a balanced to an imbalanced number of particles in either the left- or right-hand well.

[Phys. Rev. A 90, 063617] Published Tue Dec 09, 2014

]]>We investigate continuous-time quantum walks of two indistinguishable anyons in one-dimensional lattices with both on-site and nearest-neighbor interactions based on the fractional Jordan-Wigner transformation. It is shown that the two-body correlations in position space are symmetric about the init...

[Phys. Rev. A 90, 063618] Published Tue Dec 09, 2014

]]>We propose to use cavity optomechanical systems in the regime of optical bistability for the detection of weak harmonic forces. Due to the optomechanical coupling an external force on the mechanical oscillator modulates the resonance frequency of the cavity and consequently the switching rates betwe...

[Phys. Rev. A 90, 063810] Published Tue Dec 09, 2014

]]>To evidence multimode spatial entanglement of spontaneous down-conversion, detector arrays allow a full-field measurement, without any a priori selection of the paired photons. We show by comparing results of the recent literature that electron-multiplying CCD cameras allow, in the present state of ...

[Phys. Rev. A 90, 063811] Published Tue Dec 09, 2014

]]>Twin-beam coherence properties are analyzed in both spatial and spectral domains at high gain, including also the regime of pump depletion. We show an increase in the size of the intensity autocorrelation and cross-correlation areas at increasing pump power, replaced by a decrease in the pump deplet...

[Phys. Rev. A 90, 063812] Published Tue Dec 09, 2014

]]>In any realistic quantum metrology scenarios, the ultimate precision in the estimation of parameters is limited not only by the so-called Heisenberg scaling, but also the environmental noise encountered by the underlying system. In the context of quantum estimation theory, it is of great significanc...

[Phys. Rev. A 90, 062113] Published Mon Dec 08, 2014

]]>A continuous-time quantum theory for cross-phase modulation with differing group velocities has been presented and used to assess the feasibility of extending the fiber-switching technique to the single-photon regime for creating a CPHASE gate.

[Phys. Rev. A 90, 062314] Published Mon Dec 08, 2014

]]>In this paper, we present schemes on implementing the single-photon-added coherent source in quantum key distributions. We apply this source in either the standard BB84 protocol or the recently proposed measurement-device-independent quantum key distribution, comparing their performance with the cas...

[Phys. Rev. A 90, 062315] Published Mon Dec 08, 2014

]]>Higher transmission loss diminishes the performance of optical communication—be it the rate at which classical or quantum data can be sent reliably, or the secure key generation rate of quantum key distribution (QKD). Loss compounds with distance—exponentially in an optical fiber, and inverse square...

[Phys. Rev. A 90, 062316] Published Mon Dec 08, 2014

]]>Much discussion in relativistic atomic physics and quantum optics has related to the interaction of gauge and perturbation of the Hamiltonian or Dirac operator. It has been commented that Lorentz and gauge independence requires different forms of the perturbation operator in shifting from one gauge ...

[Phys. Rev. A 90, 062504] Published Mon Dec 08, 2014

]]>The photon energy dependence of relative photoionization cross sections in the valence ionization energy region of 5 to 45 eV for 4p and 4s orbitals of Rb and Br ions in RbBr vapors has been investigated. The behavior of state selective cross sections of molecular valence orbitals has been analyzed ...

[Phys. Rev. A 90, 062505] Published Mon Dec 08, 2014

]]> We carry out calculations on the van der Waals trimer ^{7}Li^{4}He_{2} using the mapping method within the frame of hyperspherical coordinates, which allows us to give accurate binding energies and wave functions for both the ground and excited state of the system. When the realistic two-body potentials are ...

[Phys. Rev. A 90, 062506] Published Mon Dec 08, 2014

]]> We analyze a transfer ionization (TI) reaction in the fast proton-helium collision H^{+}+He→H^{0}+He^{2+}+ e^{−} by solving a time-dependent Schrödinger equation (TDSE) under the classical projectile motion approximation in one-dimensional kinematics. In addition, we construct various time-independent analogs o...

[Phys. Rev. A 90, 062706] Published Mon Dec 08, 2014

]]>We have performed calculations of the fully differential cross sections for electron-impact ionization of magnesium atoms. Three theoretical approximations, the time-dependent close coupling, the three-body distorted wave, and the distorted wave Born approximation, are compared with experiment in th...

[Phys. Rev. A 90, 062707] Published Mon Dec 08, 2014

]]>A lattice-induced opacity is identified in the scattering process of a normally incident matter wave colliding with a two dimensional lattice of atoms. This system can be treated as an analog of a confinement-induced resonance. Specifically, by modifying the s-wave scattering length between atoms in...

[Phys. Rev. A 90, 063613] Published Mon Dec 08, 2014

]]>In this paper we study the interaction energy in a mixture of Bose and Fermi superfluids realized in recent cold atom experiments. On the Bose-Einstein-condensate (BEC) side of a Feshbach resonance between fermionic atoms, this interaction energy can be directly related to the scattering length betw...

[Phys. Rev. A 90, 063614] Published Mon Dec 08, 2014

]]> We study the shear viscosity of a dilute Fermi gas as a function of the scattering length in the vicinity of the unitarity limit. The calculation is based on kinetic theory, which provides a systematic approach to transport properties in the limit in which the fugacity z=nλ^{3}/2 is small. Here, n is t...

[Phys. Rev. A 90, 063615] Published Mon Dec 08, 2014

]]>We explore the manipulation in phase space of many-body wave functions that exhibit self-similar dynamics under the application of sudden force and/or in the presence of a constant acceleration field. For this purpose, we work out a common theoretical framework based on the Wigner function. We discu...

[Phys. Rev. A 90, 063616] Published Mon Dec 08, 2014

]]>We demonstrate squeezing of a strongly interacting optoelectromechanical system using a parametric drive. By employing real-time feedback on the phase of the pump at twice the resonance frequency the thermomechanical noise is squeezed beyond the 3 dB instability limit. Surprisingly, this method can ...

[Phys. Rev. A 90, 063809] Published Mon Dec 08, 2014

]]>The onset of unconventional vacuum properties in intense fields has long been an active field of research. In this paper the vacuum polarization effect is investigated via a pump probe scheme in which a probe light propagates in the vacuum excited by a standing wave composed of two counterpropagatin...

[Phys. Rev. A 90, 062111] Published Fri Dec 05, 2014

]]> Helicity amplitudes and the differential cross section of high-energy e^{+}e^{−} photoproduction accompanied by bremsstrahlung in the electric field of a heavy atom (i.e., the amplitudes of the process γ_{1}Z→e^{+}e^{−}γ_{2}Z) are derived. The results are exact in the nuclear charge number and are obtained in the lea...

[Phys. Rev. A 90, 062112] Published Fri Dec 05, 2014

]]>This paper unveils some features of a discrete-time quantum walk on the line whose coin depends on the temporal variable. After considering the most general form of the unitary coin operator, it focuses on the role played by the two phase factors that one can incorporate there, and shows how both te...

[Phys. Rev. A 90, 062312] Published Fri Dec 05, 2014

]]>We analyze the performance of a generalized Kitaev's phase-estimation algorithm where N phase gates, acting on M qubits prepared in a product state, may be distributed in an arbitrary way. Unlike the standard algorithm, where the mean square error scales as 1/N, the optimal generalizations offer the...

[Phys. Rev. A 90, 062313] Published Fri Dec 05, 2014

]]>We study the field-ionization threshold behavior when a Rydberg atom is ionized by a short single-cycle pulse field. Both hydrogen and sodium atoms are considered. The required threshold field amplitude is found to scale inversely with the binding energy when the pulse duration becomes shorter than ...

[Phys. Rev. A 90, 063413] Published Fri Dec 05, 2014

]]>High-order above-threshold ionization (ATI) is characterized by the rescattering of the ionized electron off the parent ion. The ATI amplitude can be calculated applying the saddle-point (SP) method and the uniform approximation to a five-dimensional integral over the ionization time, intermediate e...

[Phys. Rev. A 90, 063414] Published Fri Dec 05, 2014

]]>In the present work, we theoretically propose and numerically illustrate a mean-field analog of the Hong-Ou-Mandel experiment with bright solitons. More specifically, we scatter two solitons off of each other (in our setup, the bright solitons play the role of a classical analog to the quantum photo...

[Phys. Rev. A 90, 063612] Published Fri Dec 05, 2014

]]>We analyze the properties of electromagnetic waves inside materials with induced polarization and magnetization. We show that if the polarization and magnetization of the material are sufficiently large and appropriately phased, then the system supports the formation of left-handed waves. In some re...

[Phys. Rev. A 90, 063807] Published Fri Dec 05, 2014

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