We show a general relationship between a superposition of macroscopically distinct states and sensitivity in quantum metrology. Generalized cat states are defined by using an index which extracts the coherence between macroscopically distinct states, and a wide variety of states, including a classic...

[Phys. Rev. A 100, 032318] Published Fri Sep 13, 2019

]]>Standard protocols for quantum key distribution (QKD) require that the sender be able to transmit in two or more mutually unbiased bases. Here, we analyze the extent to which the performance of QKD is degraded by diffraction effects that become relevant for long propagation distances and limited siz...

[Phys. Rev. A 100, 032319] Published Fri Sep 13, 2019

]]>Rydberg states of atoms and molecules are very sensitive to electric fields. This property makes them ideal electric-field sensors but is detrimental to applications of Rydberg states in quantum optics, quantum-information processing, and quantum simulation because of inhomogeneous Stark broadening ...

[Phys. Rev. A 100, 032512] Published Fri Sep 13, 2019

]]>The polarization of high-order harmonic generation in ${\mathrm{H}}_{2}{}^{+}$ driven by a counterrotating bichromatic $\omega /3\omega $ circularly polarized laser field is investigated theoretically. The elliptically polarized harmonics are characterized by ellipticity and rotation angle, where the latter is expanded to $[-\pi /2,\pi /2]$ ...

[Phys. Rev. A 100, 033410] Published Fri Sep 13, 2019

]]>Determination of enantiomeric excess is important and remains challenging. We propose theoretically a spectroscopic method for this issue based on the chirality-dependent ac Stark effects in cyclic three-level models under the three-photon resonance condition. The enantiomeric excess of the chiral m...

[Phys. Rev. A 100, 033411] Published Fri Sep 13, 2019

]]>Photon-pair sources from atomic ensembles are considered essential to the development of quantum science and technology based on atom-photon interfaces. The measurement of spectral-temporal biphoton wave forms is important for the characterization of frequency-time entangled photon pairs. Here, we d...

[Phys. Rev. A 100, 033818] Published Fri Sep 13, 2019

]]>Dissipative Kerr soliton frequency combs generated in high-Q microresonators may unlock novel perspectives in a variety of applications and crucially rely on quantitative models for systematic device design. Here, we present a global bifurcation study of the Lugiato-Lefever equation which describes ...

[Phys. Rev. A 100, 033819] Published Fri Sep 13, 2019

]]>In estimating an unknown parameter of a quantum state the quantum Fisher information (QFI) is a pivotal quantity, which depends on the state and its derivate with respect to the unknown parameter. We prove the continuity property for the QFI in the sense that two close states with close first deriva...

[Phys. Rev. A 100, 032317] Published Thu Sep 12, 2019

]]>It is usually assumed that the field isotope shift (FIS) is completely determined by the change of the averaged squared values of the nuclear charge radius $\langle {r}^{2}\rangle $. Relativistic corrections modify the expression for FIS, which is actually described by the change of $\langle {r}^{2\gamma}\rangle $, where $\gamma =\sqrt{1-{Z}^{2}{\alpha}^{2}}$. In the present...

[Phys. Rev. A 100, 032511] Published Thu Sep 12, 2019

]]>We study the inelastic scattering of two-dimensional massless Dirac fermions by an inhomogeneous time-dependent driving field. As a physical realization, we consider a monolayer graphene normally illuminated with a circularly polarized laser of frequency $\mathrm{\Omega}$ in a given region. The interaction Hamilton...

[Phys. Rev. A 100, 033409] Published Thu Sep 12, 2019

]]>We develop a method to extract the dissipation for a heavy moving impurity immersed in superfluid Fermi gases, which may serve as a theoretical model to explain relevant experiments. The drag force is derived analytically. As a reward, we are able to extract the density-density correlation function,...

[Phys. Rev. A 100, 033611] Published Thu Sep 12, 2019

]]>Photon antibunching based on a single two-level atom strongly coupled to a single-mode optical cavity has been demonstrated in experiments. Here, we put forward an improved version of such an antibunching by introducing a pump field and a microwave field in the coupled atom-cavity system to form bot...

[Phys. Rev. A 100, 033814] Published Thu Sep 12, 2019

]]>The dynamical Casimir effect (DCE) is the production of photons by the amplification of vacuum fluctuations. In this paper, we demonstrate resonance conditions in DCE that potentially allow the production of optical photons when the mechanical frequency is smaller than the lowest frequency of the ca...

[Phys. Rev. A 100, 033815] Published Thu Sep 12, 2019

]]>We outline the nonperturbative theory of multiple scattering of resonant, intense laser light off a dilute cloud of cold atoms. A combination of master equation and diagrammatic techniques allows a quantitative description of nonlinear diffusive transport as well as of coherent backscattering of the...

[Phys. Rev. A 100, 033816] Published Thu Sep 12, 2019

]]>We study the effect of polarization on optical micromanipulation in a hexagonal optical lattice formed by three equiamplitude plane waves that have their wave vectors lying equiangularly in a plane, taking into account the vectorial characteristic of the electromagnetic waves. It is demonstrated tha...

[Phys. Rev. A 100, 033817] Published Thu Sep 12, 2019

]]>We study the zero-temperature phase diagram of the Lechner-Hauke-Zoller model. An analytic expression for the free energy and critical coefficients for finite-size systems and in the thermodynamic limit are derived and numerically verified. With the aim to improve standard quantum annealing, we intr...

[Phys. Rev. A 100, 032110] Published Wed Sep 11, 2019

]]>Electronic stopping cross sections (SCSs) of nickel, silicon, and nickel-silicon alloys for protons and helium (He) ions are studied in the regime of medium- and low-energy ion scattering, i.e., for ion energies in the range from $500\phantom{\rule{4pt}{0ex}}\mathrm{eV}$ to $200\phantom{\rule{4pt}{0ex}}\mathrm{keV}$. For protons, at velocities below the Bohr velocity th...

[Phys. Rev. A 100, 032705] Published Wed Sep 11, 2019

]]>A method to engineer stroboscopically arbitrary one-dimensional optical potentials with subwavelength resolution is proposed. The engineering of both smooth and comblike periodic potentials for atoms in the dark state are demonstrated. Potential applications include creation of an optical lattice or superlattice with spacing much shorter than the optical wavelength.

[Phys. Rev. A 100, 033610] Published Wed Sep 11, 2019

]]>Polarization-dependent loss (PDL) is a serious problem that hinders the transfer of polarization qubits through quantum networks. Recently it has been shown that the detrimental effects of PDL on qubit fidelity can be compensated for with the introduction of an additional passive PDL element that re...

[Phys. Rev. A 100, 033811] Published Wed Sep 11, 2019

]]>It is usually difficult to generate mechanical squeezing in standard optomechanical systems when the decay rate of the cavity or the effective coupling strength of the system is too large. Here we investigate the mechanical squeezing beyond resolved sideband and weak-coupling limits in a standard op...

[Phys. Rev. A 100, 033812] Published Wed Sep 11, 2019

]]>A typical route to study the quantum-to-classical transition consists of probing systems with increased particle sizes. Here, a formalism is developed to investigate near-field interferometry beyond the Rayleigh limit, providing the expressions needed to describe coherent and incoherent effects in an optical grating.

[Phys. Rev. A 100, 033813] Published Wed Sep 11, 2019

]]>Coherence manipulation is fundamental in the study of the resource theory of quantum coherence. It is aimed at identifying when it is possible to convert a given coherent state to another using only incoherent operations. In this paper, it is shown that a finite number of measure conditions are not ...

[Phys. Rev. A 100, 032313] Published Tue Sep 10, 2019

]]>We introduce a protocol for authenticated teleportation, which can be proven secure even when the receiver does not trust his or her measurement devices, and which is experimentally accessible. We use the technique of self-testing from the device-independent approach to quantum information, where we...

[Phys. Rev. A 100, 032314] Published Tue Sep 10, 2019

]]>In a recent work [Pallister, Linden, and Montanaro, Phys. Rev. Lett. **120**, 170502 (2018)], Pallister *et al.* proposed an optimal strategy to verify nonmaximally entangled two-qubit pure states under the constraint that the accessible measurements are locally projective and nonadaptive. Their good resu...

[Phys. Rev. A 100, 032315] Published Tue Sep 10, 2019

]]>We propose practical and efficient protocols for verifying bipartite pure states for any finite dimension, which can also be applied to fidelity estimation. Our protocols are based on adaptive local projective measurements with either one-way or two-way communications, which are very easy to impleme...

[Phys. Rev. A 100, 032316] Published Tue Sep 10, 2019

]]>The direct variational determination of the two-electron reduced-density matrix (2-RDM) corresponding to an atomic or molecular system is usually carried out in a basis of real-valued atom-centered Gaussian basis functions, under the assumption that the 2-RDM is a real-valued quantity. However, for ...

[Phys. Rev. A 100, 032509] Published Tue Sep 10, 2019

]]>The scenario of a single-mode cavity with harmonically modulated frequency is revisited in the presence of strongly detuned qubit or cyclic qutrit. It is found that when the qubit frequency is close to $3\nu $ there is a peak in the photon generation rate via four-photon transitions for the modulation fr...

[Phys. Rev. A 100, 032510] Published Tue Sep 10, 2019

]]>We present interferometeric measurements of the $f=1$ to $f=2$ interhyperfine scattering lengths in a single-domain spinor Bose-Einstein condensate of ${}^{87}\mathrm{Rb}$. The interhyperfine interaction leads to a strong and state-dependent modification of the spin-mixing dynamics with respect to a noninteracting desc...

[Phys. Rev. A 100, 032704] Published Tue Sep 10, 2019

]]>Spin dynamics of a spin-3 dipolar Bose gas in an optical lattice is investigated experimentally and theoretically. Distinct behaviors in two regimes, at low and high lattice depths, are identified. The system naturally forms a quantum simulator for rich many-body physics.

[Phys. Rev. A 100, 033609] Published Tue Sep 10, 2019

]]>We approach the strong-coupling thermodynamic limit in the response of the open driven Jaynes-Cummings (JC) oscillator. We do so by highlighting the role of quantum fluctuations against the semiclassical response in three distinct regimes of operation. We begin by demonstrating the persistence of ph...

[Phys. Rev. A 100, 033810] Published Tue Sep 10, 2019

]]>Inspired by the power of abstraction in information theory, we consider quantum rebound protocols as a way of providing a unifying perspective to deal with several information-processing tasks related to and extending quantum channel discrimination to the Shannon-theoretic regime. Such protocols, de...

[Phys. Rev. A 100, 030302(R)] Published Mon Sep 09, 2019

]]>Given the initial state of the whole system and the spectral density function of the environment, the dynamics of a non-Markovian open system can be exactly determined. However, it has barely been studied how to obtain, in reverse, the spectral density function from the system dynamics. In this work...

[Phys. Rev. A 100, 032108] Published Mon Sep 09, 2019

]]>In analog gravity the recent experiment of Drori *et al.* [Phys. Rev. Lett. **122**, 010404 (2019)] is impressive, as it shows how the emission of two Hawking quanta emitted in opposite directions leads to measurable consequences in the medium's rest system in a straightforward way. This result raises, ho...

[Phys. Rev. A 100, 032109] Published Mon Sep 09, 2019

]]>Using the Lieb-Robinson inequality and the continuity property of the quantum capacities in terms of the diamond norm, we derive an upper bound on the values that these capacities can attain in spin-network communication i.i.d. models of arbitrary topology. Different from previous results we make no...

[Phys. Rev. A 100, 032311] Published Mon Sep 09, 2019

]]>We return to the problem of evaluation of the light-by-light contribution to the energy levels of the hydrogen atom. We find an additional contribution directly related to the Delbrück scattering amplitude. The new correction is larger than the previously included light-by-light terms at order ${\alpha}^{2}{(Z\alpha ...}^{}$

[Phys. Rev. A 100, 032507] Published Mon Sep 09, 2019

]]>A natural orbital functional for electronic systems with any value of the spin is proposed. This energy functional is based on an alternative reconstruction for the two-particle reduced density matrix (2RDM) of the multiplet, that is, of the mixed quantum state that allows all possible spin projecti...

[Phys. Rev. A 100, 032508] Published Mon Sep 09, 2019

]]>Angular and energy-dependent photon distributions emitted from $50\text{\u2212}\mathrm{keV}$ to $2.5\text{\u2212}\mathrm{MeV}$ electrons colliding with targets ranging from Cu to Pb are calculated using a consistent higher order analytical approach as well as the exact Dirac partial-wave theory. By comparison with exact numerical results for ne...

[Phys. Rev. A 100, 032703] Published Mon Sep 09, 2019

]]>We analytically and numerically investigate the emission of high-order harmonic radiation from model solids by intense few-cycle midinfrared laser pulses. In single-active-electron approximation, we expand the active electron's wave function in a basis of adiabatic Houston states and describe the so...

[Phys. Rev. A 100, 033405] Published Mon Sep 09, 2019

]]>Collisional heating of a cold-atom system subjected to time-periodic forces is investigated theoretically. A general description of the heating rate is proposed and the crossover between the quantum and semiclassical regimes is identified.

[Phys. Rev. A 100, 033406] Published Mon Sep 09, 2019

]]>Spin-polarization effects of an ultrarelativistic electron beam head-on colliding with an ultraintense two-color laser pulse are investigated comprehensively in the quantum radiation-dominated regime. We employ a Monte Carlo method, derived from the recent work of Li *et al.* [Phys. Rev. Lett. **122**, 15...

[Phys. Rev. A 100, 033407] Published Mon Sep 09, 2019

]]>We study optical gain in a gas of cold ${}^{39}\mathrm{K}$ atoms. The gain is observed during operation of a conventional magneto-optical trap without the need for additional fields. Measurements of transmission spectra from a weak probe show that the gain is due to stimulated Raman scattering between hyperfine gro...

[Phys. Rev. A 100, 033408] Published Mon Sep 09, 2019

]]>In the present work we examine the statics and dynamics of multiple parallel dark soliton stripes in a two-dimensional Bose-Einstein condensate. Our principal goal is to study the effect of the interaction between the stripes on the transverse instability of the individual stripes. The cases of two-...

[Phys. Rev. A 100, 033607] Published Mon Sep 09, 2019

]]>We study the ground-state phase diagrams of two-photon Dicke, one-dimensional Jaynes-Cummings-Hubbard (JCH), and Rabi-Hubbard (RH) models using mean-field, perturbation, quantum Monte Carlo (QMC), and density-matrix renormalization-group methods. We first compare mean-field predictions for the phase...

[Phys. Rev. A 100, 033608] Published Mon Sep 09, 2019

]]>We analyze the propagation of waves on the surface of the simplest Platonic solid, the regular tetrahedron. We find that the time evolution of a quantum particle confined to such a surface is equivalent to the diffraction pattern from a certain grating profile and can therefore be investigated in a ...

[Phys. Rev. A 100, 033806] Published Mon Sep 09, 2019

]]>The efficiency of the frequency conversion process at the heart of Raman heterodyne spectroscopy was improved by nearly four orders of magnitude by resonant enhancement of both the pump and signal optical fields. Our results using an erbium-doped ${\mathrm{Y}}_{2}{\mathrm{SiO}}_{5}$ crystal embedded in a microwave and an optical...

[Phys. Rev. A 100, 033807] Published Mon Sep 09, 2019

]]>We propose a scheme to study loss-induced localization in a nonlinear three-site system with a periodically driven field acting on the first site and a loss on the last site. We identify a significant feature; that is, system losses could be introduced to profoundly enhance localization. Our simulat...

[Phys. Rev. A 100, 033808] Published Mon Sep 09, 2019

]]>The canonical boundary-value problem for surface-plasmon-polariton (SPP) waves guided by the planar interface of a dielectric material and a plasmonic material was solved for cases wherein either partnering material could be a uniaxial material with optic axis lying in the interface plane. Numerical...

[Phys. Rev. A 100, 033809] Published Mon Sep 09, 2019

]]>Recently the quantum information science community devoted a lot of attention to the theoretical and practical aspects of generalized measurements, the formalism of all possible quantum operations leading to acquisition of classical information. On the other hand, due to imperfections present in qua...

[Phys. Rev. A 100, 030301(R)] Published Fri Sep 06, 2019

]]>Calculating the physical properties of quantum thermal states is a difficult problem for classical computers, rendering it intractable for most quantum many-body systems. A quantum computer, by contrast, would make many of these calculations feasible in principle, but it is still nontrivial to prepa...

[Phys. Rev. A 100, 032107] Published Fri Sep 06, 2019

]]>Quantum information scrambling has attracted much attention amid the effort to reconcile the conflict between quantum-mechanical unitarity and the thermalization irreversibility in many-body systems. Here we propose an unconventional mechanism to generate quantum information scrambling through a hig...

[Phys. Rev. A 100, 032309] Published Fri Sep 06, 2019

]]>Generating entanglement in a distributed scenario is a fundamental task for implementing the quantum network of the future. We here report a protocol that uses only linear optics for generating Greenberger-Horne-Zeilinger states with high fidelities in a nearby node configuration. Moreover, we analy...

[Phys. Rev. A 100, 032310] Published Fri Sep 06, 2019

]]>Two-color XUV plus near-IR multiphoton ionization of the helium ion by circularly polarized light is studied in the vicinity of the $3p$ resonance. Combining the analysis of results obtained by solving the time-dependent Schrödinger equation and that of the quasienergy spectrum of ${\mathrm{He}}^{+}$ reveals the phys...

[Phys. Rev. A 100, 033404] Published Fri Sep 06, 2019

]]>Fano resonance exhibiting an asymmetric spectral line shape is a universal phenomenon observed in diverse physical systems. Here we experimentally establish a direct link between the spectral asymmetry parameter $q$ and a physically realizable phase factor of interference between a continuum and a dis...

[Phys. Rev. A 100, 033805] Published Fri Sep 06, 2019

]]>Electro-optical sampling has been recently used to perform spectrally resolved measurements of electromagnetic vacuum fluctuations and it has been predicted it could be used to probe the population of virtual photons predicted to exist in the ground state of an ultrastrongly light-matter coupled sys...

[Phys. Rev. A 100, 031801(R)] Published Thu Sep 05, 2019

]]>An even number of fermions can behave in a bosonic way. The simplest scenario involves two fermions which can form a single boson, but four fermions can either behave as two bipartite bosons or further assemble into a single four-partite bosonic molecule. In general, for $2N$ fermions there are many p...

[Phys. Rev. A 100, 032105] Published Thu Sep 05, 2019

]]>Macroscopic realism is a classical worldview that a macroscopic system is always determinately in one of the two or more macroscopically distinguishable states available to it and so is never in a superposition of these states. The question of whether there is a fundamental limitation on the possibi...

[Phys. Rev. A 100, 032106] Published Thu Sep 05, 2019

]]>In a recent work [A. Aloy *et al.*, Phys. Rev. Lett. **123**, 100507 (2019)] we have considered the characterization of entanglement depth, from a device-independent perspective, in a quantum many-body system. We have shown that the inequalities introduced by J. Tura *et al.* [Science **344**, 1256 (2014)] can...

[Phys. Rev. A 100, 032307] Published Thu Sep 05, 2019

]]>Quantum algorithms are usually described as monolithic circuits, becoming large at modest input size. Near-term quantum architectures can only manage a small number of qubits. We develop an automated method to distribute quantum circuits over multiple agents, minimizing quantum communication between...

[Phys. Rev. A 100, 032308] Published Thu Sep 05, 2019

]]>We report on a systematic investigation of wavelength scaling strong-field double ionization of Mg in intense laser fields. A significant decrease of nonsequential double ionization (NSDI) yield with increasing wavelength from 800–2000 nm is observed. Our data is well reproduced by a three-dimension...

[Phys. Rev. A 100, 033403] Published Thu Sep 05, 2019

]]>We study theoretically the propagation of a guided atom laser across an Aharonov-Bohm ring which is exposed to a synthetic gauge field. The presence of disorder within the ring gives rise to Al'tshuler-Aronov-Spivak oscillations, seen in the disorder average of the transmission as a function of the ...

[Phys. Rev. A 100, 033606] Published Thu Sep 05, 2019

]]>[Phys. Rev. A 100, 039901] Published Thu Sep 05, 2019

]]>We demonstrate a hybrid method based on field ionization and state-selective deexcitation capable of measuring the lifetimes of high-lying Rydberg levels. For $nS$ Rydberg states of Rb atoms with principal quantum number $60\le n\le 88$, we measure both the lifetimes of single target states and those of the e...

[Phys. Rev. A 100, 030501(R)] Published Wed Sep 04, 2019

]]>Boson sampling is a well-defined scheme for demonstrating quantum supremacy with photons in the near term. However, relying only on multiphoton interference in nonadaptive linear-optical networks, the scheme is difficult to simulate classically. Here we study boson sampling using matrix product stat...

[Phys. Rev. A 100, 032305] Published Wed Sep 04, 2019

]]>We describe a quantum algorithm for preparing states that encode solutions of nonhomogeneous linear partial differential equations. The algorithm is a continuous-variable version of matrix inversion: it efficiently inverts differential operators that are polynomials in the variables and their partia...

[Phys. Rev. A 100, 032306] Published Wed Sep 04, 2019

]]>Benchmark calculations of the total and transition energies of the four lowest ${}^{1}S$ states of the beryllium atom are performed. The computational approach is based on variational calculations with finite mass of the nucleus. All-particle explicitly correlated Gaussian (ECG) functions are used to expan...

[Phys. Rev. A 100, 032504] Published Wed Sep 04, 2019

]]>The Schrödinger equation for the $2S$ state and $2P$ state of the lithiumlike ion ${\mathrm{O}}^{5+}$ is solved by using the Rayleigh-Ritz variational method in Hylleraas coordinates. The leading-order relativistic and QED corrections are calculated perturbatively and higher-order corrections are estimated approximatel...

[Phys. Rev. A 100, 032505] Published Wed Sep 04, 2019

]]>We report electron-atom Compton scattering experiments on the ${\mathrm{H}}_{2}$ and ${\mathrm{D}}_{2}$ molecules. Energy-loss spectra of electrons quasielastically backscattered at an angle of 135° are measured as a function of azimuthal angle at an incident electron energy of 2.0 keV. Momentum distributions of the H and D atoms ...

[Phys. Rev. A 100, 032506] Published Wed Sep 04, 2019

]]>Coherence among rotational ion channels during photoionization is exploited to control the anisotropy of the resulting photoelectron angular distributions at specific photoelectron energies. The strategy refers to a robust and single parameter control using two ultrashort light pulses delayed in tim...

[Phys. Rev. A 100, 033402] Published Wed Sep 04, 2019

]]>We describe a procedure for engineering beams of cold atoms by selectively draining particles from a trapped gas based on momenta. Atoms escape through a filter potential that only transmits atoms with the desired momenta. We outline an algorithm that outputs a filter potential that produces a presp...

[Phys. Rev. A 100, 033604] Published Wed Sep 04, 2019

]]>We theoretically demonstrate that an external magnetic field can be used to control quantum reflection of matter waves in graphene due to its extraordinary magneto-optical properties. We calculate the quantum reflection probabilities in graphene for three experimentally relevant atomic species (He, ...

[Phys. Rev. A 100, 033605] Published Wed Sep 04, 2019

]]>We present a proposal to prepare the macroscopic superposition states of a mechanical oscillator in an optomechanical system with quadratic coupling. By coherently driving the optomechanical cavity with an external field, a Kerr-type interaction among phonons is induced. The macroscopic mechanical s...

[Phys. Rev. A 100, 033803] Published Wed Sep 04, 2019

]]>We experimentally address emergent spectrospatial correlations in a one-dimensional amplifying system that sustains Anderson-localized lasing modes. The structure is based on a periodic-on-average random template, and hence follows the frequency behavior determined by passbands and band gaps of a ph...

[Phys. Rev. A 100, 033804] Published Wed Sep 04, 2019

]]>Over the last few years it was pointed out that certain observables of time-evolving quantum systems may have singularities at certain moments in time, mimicking the singularities physical systems have when undergoing phase transitions. These were given the name of dynamical phase transitions. They ...

[Phys. Rev. A 100, 031601(R)] Published Tue Sep 03, 2019

]]>We experimentally investigate the non-Markovianity problems in a quantum channel implemented by an all-optical setup. The quantum channel simulates the dynamics of a two-level (qubit) system surrounded by bosonic modes, with the system-environment interaction treated without applying the rotating-wa...

[Phys. Rev. A 100, 032101] Published Tue Sep 03, 2019

]]>A non-Hermitian topological insulator with a real spectrum is interesting in the theory of non-Hermitian extension of topological systems. We find an experimentally realizable example of a two-dimensional non-Hermitian topological insulator with a real spectrum. We consider the two-dimensional Su-Sc...

[Phys. Rev. A 100, 032102] Published Tue Sep 03, 2019

]]>Polarization of photons is the key physical quantity in measurements of quantum spin correlations. According to a variant of quantum and classical electrodynamics formulated by us on the grounds of a hypothesis of existence of a preferred frame of reference (PF) a modification of the Malus law is ex...

[Phys. Rev. A 100, 032103] Published Tue Sep 03, 2019

]]>We generalize the approach by Braunstein and Caves, [Phys. Rev. Lett. **72**, 3439 (1994)]. to quantum multiparameter estimation with general states. We derive a matrix bound of the classical Fisher information matrix due to each measurement operator. The saturation of all these bounds results in the sa...

[Phys. Rev. A 100, 032104] Published Tue Sep 03, 2019

]]>In this article we study lossless compression of strings of pure quantum states of indeterminate-length quantum codes which were introduced by Schumacher and Westmoreland. Past work has assumed that the strings of quantum data are prepared to be encoded in an independent and identically distributed ...

[Phys. Rev. A 100, 032301] Published Tue Sep 03, 2019

]]>We propose a theoretical scheme to investigate the dynamics of quantum correlation between two nitrogen-vacancy-center ensembles (NVEs) coupled to a common superconducting coplanar waveguide resonator, driven by a broadband microwave squeezed field working as a squeezed-vacuum reservoir. Based on th...

[Phys. Rev. A 100, 032302] Published Tue Sep 03, 2019

]]>The advantages of quantum information processing are in many cases obtained as consequences of quantum interactions, especially for computational tasks where two-qubit interactions are essential. In this work, we establish the framework of analyzing and quantifying loss or gain of information on a q...

[Phys. Rev. A 100, 032303] Published Tue Sep 03, 2019

]]>Randomized benchmarking (RB) is an efficient and robust method to characterize gate errors in quantum circuits. Averaging over random sequences of gates leads to estimates of gate errors in terms of the average fidelity. These estimates are isolated from the state preparation and measurement errors ...

[Phys. Rev. A 100, 032304] Published Tue Sep 03, 2019

]]>It is commonly thought that thermal photons with transverse electric polarization cannot exist in a planar metallic cavity whose size $a$ is smaller than the thermal wavelength ${\lambda}_{T}$, due to the absence of modes with $\lambda <2a$. Computations based on a realistic model of the mirrors contradict this expectat...

[Phys. Rev. A 100, 032501] Published Tue Sep 03, 2019

]]>The $4{f}^{6}\phantom{\rule{0.28em}{0ex}}{}^{7}{F}_{0}\to 4{f}^{6}{}^{5}{D}_{0}$ intraconfiguration transition in $\mathrm{Sm}:{\mathrm{SrF}}_{2}$ is forbidden for ${\mathrm{Sm}}^{2+}$ ions in the octahedrally symmetric substitution sites in ${\mathrm{SrF}}_{2}$. We report the direct observation of this transition using laser-induced fluorescence at cryogenic temperatures, and measurements of the excited-state lifeti...

[Phys. Rev. A 100, 032502] Published Tue Sep 03, 2019

]]>Measurement of the branching ratios for $6{P}_{1/2}$ decays to $6{S}_{1/2}$ and $5{D}_{3/2}$ in ${}^{138}\mathrm{Ba}^{+}$ are reported with the decay probability from $6{P}_{1/2}$ to $5{D}_{3/2}$ measured to be $p=0.268177\pm {\left(37\right)}_{\mathrm{stat}}\u2013{\left(20\right)}_{\mathrm{sys}}$. This result differs from a recent report by $12\sigma $. A detailed account of systematics is given, and the likely source...

[Phys. Rev. A 100, 032503] Published Tue Sep 03, 2019

]]>The confined variational method is applied to investigate the low-energy elastic scattering of orthopositronium from ${\text{H}}_{2}$ by first-principles quantum mechanics. Describing the correlations with explicitly correlated Gaussians, we obtain accurate $s$-wave phase shifts and pickoff annihilation parameters ...

[Phys. Rev. A 100, 032701] Published Tue Sep 03, 2019

]]>Electron-impact ionization of an atom or ion in the presence of a neighboring atom is studied. The latter is first collisionally excited by the incident electron, whose energy is assumed to be high but nonrelativistic. Afterwards, the excitation energy is transferred radiationlessly via a two-center...

[Phys. Rev. A 100, 032702] Published Tue Sep 03, 2019

]]>An ultrafast electro-optic effect of the zinc sulfide crystal is predicted employing a numerical pump-probe simulation. The numerical results indicate that the time dependence of the off-diagonal part of the dielectric function of ZnS exhibits a phase shift with respect to the pump laser field. The ...

[Phys. Rev. A 100, 033401] Published Tue Sep 03, 2019

]]>We investigate the low-energy dynamics of two coupled anisotropic Bose-Einstein condensates forming a long Josephson junction. The theoretical study is performed in the framework of the two-dimensional Gross-Pitaevskii equation and the Bogoliubov–de Gennes formalism. We analyze the excitation spectr...

[Phys. Rev. A 100, 033601] Published Tue Sep 03, 2019

]]>We propose a scheme for controlling the movement of dimers, trimers, and other multimers in optical lattices by modulating the lattice potential. In deep optical lattices the propagation of deeply bound atomic clusters is slowed by the high energy cost of virtual intermediate states. Adapting the we...

[Phys. Rev. A 100, 033602] Published Tue Sep 03, 2019

]]>We consider the phase-ordering dynamics of an isolated quasi-two-dimensional spin-1 Bose gas quenched into an easy-plane ferromagnetic phase. Preparing the initial system in an unmagnetized antiferromagnetic state the subsequent ordering involves both polar core and Mermin-Ho spin vortices, with the...

[Phys. Rev. A 100, 033603] Published Tue Sep 03, 2019

]]>Quantum memories are essential for large-scale quantum information networks. Along with high efficiency, storage lifetime, and optical bandwidth, it is critical that the memory adds negligible noise to the recalled signal. A common source of noise in optical quantum memories is spontaneous four-wave...

[Phys. Rev. A 100, 033801] Published Tue Sep 03, 2019

]]>Multiphoton emitters are a sought-after resource in quantum photonics. Nonlinear interactions between a multilevel atomic system and a coherent drive can lead to resonant two-photon emission, but harvesting light from this process has remained a challenge due to the small oscillator strengths involv...

[Phys. Rev. A 100, 033802] Published Tue Sep 03, 2019

]]>The nonrelativistic energy together with relativistic and quantum electrodynamic corrections for all the molecular hydrogen isotopologues (${\mathrm{D}}_{2}$, ${\mathrm{T}}_{2}$, HD, HT, DT) were evaluated without expansion in the electron-nucleus mass ratio. The obtained results significantly improve the uncertainty of theoretica...

[Phys. Rev. A 100, 020503(R)] Published Fri Aug 30, 2019

]]>Momentum diffusion is a possible mechanism for driving macroscopic quantum systems towards classical behavior. Experimental tests of this hypothesis rely on a precise estimation of the strength of this diffusion. We show that quantum-mechanical squeezing offers significant improvements, including wh...

[Phys. Rev. A 100, 022129] Published Fri Aug 30, 2019

]]>We design a series of quantum circuits that generate absolute maximally entangled (AME) states to benchmark a quantum computer. A relation between graph states and AME states can be exploited to optimize the structure of the circuits and minimize their depth. Furthermore, we find that most of the pr...

[Phys. Rev. A 100, 022342] Published Fri Aug 30, 2019

]]>We show theoretically that a network of superconducting loops and magnetic particles can be used to implement magnonic crystals with tunable magnonic band structures. In our approach, the loops mediate interactions between the particles and allow magnetic excitations to tunnel over long distances. A...

[Phys. Rev. A 100, 022343] Published Fri Aug 30, 2019

]]>A theoretical study of the interference pattern imprinted on the doubly differential momentum distribution of the photoelectron due to atomic ionization induced by a short laser pulse is developed from a semiclassical standpoint. We use the semiclassical two-step model of Shvetsov-Shilovski *et al.* [...

[Phys. Rev. A 100, 023419] Published Fri Aug 30, 2019

]]>We have studied collective recoil lasing by a cold atomic gas, scattering photons from an incident laser into many radiation modes in free space. The model consists of a system of classical equations for the atomic motion of $N$ atoms where the radiation field has been adiabatically eliminated. We per...

[Phys. Rev. A 100, 023630] Published Fri Aug 30, 2019

]]>An entangled photon experiment has been performed with a large variation of the temperature of the nonlinear crystal generating the entangled pair by spontaneous downconversion. The photon pairs are separated by a nonpolarizing beamsplitter, and the polarization modes are mixed by half-wave plates. ...

[Phys. Rev. A 100, 023850] Published Fri Aug 30, 2019

]]>It has been believed that statistical inequalities such as the Bell inequality should be modified once measurement independence (MI), the assumption that observers can freely choose measurement settings without changing the probability distribution of hidden variables, is relaxed. However, we show t...

[Phys. Rev. A 100, 022128] Published Thu Aug 29, 2019

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