Deterministically cloning (copying) nonorthogonal states is forbidden in quantum mechanics, but deterministic pseudo-unitary cloning is possible in a nonunitary system. We prove and show that, for any two nonorthogonal qubit states, we can find a linear, invertible Hermitian (metric) operator to mak...

[Phys. Rev. A 101, 010302(R)] Published Fri Jan 17, 2020

]]>Precise measurements of the displacement of, and force acting on, a mechanical oscillator can be performed by coupling the oscillator to an optical cavity. Brownian thermal forces represent a fundamental limit to measurement sensitivity which impedes the ability to use precise force measurements as ...

[Phys. Rev. A 101, 011802(R)] Published Fri Jan 17, 2020

]]>In a previous paper tests for entanglement for two-mode systems involving identical massive bosons were obtained. In the present paper we consider sufficiency tests for Einstein-Podolsky-Rosen (EPR) steering in such systems. We find that spin squeezing in any spin component, a Bloch vector test, the...

[Phys. Rev. A 101, 012117] Published Fri Jan 17, 2020

]]>Clustering algorithms are a cornerstone of machine learning applications. Recently, a quantum algorithm for clustering based on the $k$-means algorithm has been proposed by Kerenidis, Landman, Luongo, and Prakash. Based on their work, we propose a quantum expectation-maximization algorithm for Gaussia...

[Phys. Rev. A 101, 012326] Published Fri Jan 17, 2020

]]>The real-time flux dynamics of up to three superconducting quantum interference devices (SQUIDs) are studied by numerically solving the time-dependent Schrödinger equation. The numerical results are used to scrutinize the mapping of the flux degrees of freedom onto two-level systems (the qubits) as ...

[Phys. Rev. A 101, 012327] Published Fri Jan 17, 2020

]]>The quantum open-system simulation is an important category of quantum simulation. By simulating the thermalization process at zero temperature, we can solve the ground-state problem of quantum systems. To realize the open-system evolution on the quantum computer, we need to encode the environment u...

[Phys. Rev. A 101, 012328] Published Fri Jan 17, 2020

]]>Entanglement can be considered as a special quantum correlation, but not the only kind. Even for a separable quantum system, nonclassical correlations are allowed to exist. Here we propose two dissipative schemes for generating a maximally correlated state of two qubits in the absence of quantum ent...

[Phys. Rev. A 101, 012329] Published Fri Jan 17, 2020

]]>We propose a scheme for the construction of the one-particle Green's function (GF) of an interacting electronic system via statistical sampling on a quantum computer. Although the nonunitarity of creation and annihilation operators for the electronic spin orbitals prevents us from preparing specific...

[Phys. Rev. A 101, 012330] Published Fri Jan 17, 2020

]]>Experimental validation and control of quantum traits for an open quantum system are important for any quantum information purpose. We consider a traveling atom qubit as a quantum memory with adjustable velocity inside a leaky cavity, adopting a quantum witness as a figure of merit for quantumness a...

[Phys. Rev. A 101, 012331] Published Fri Jan 17, 2020

]]>This paper presents rotational-state-selective field-ionization spectra of highly excited triplet $nd\phantom{\rule{4pt}{0ex}}{\text{H}}_{2}$ Rydberg states. A fast $6\phantom{\rule{4pt}{0ex}}\mathrm{keV}$ beam of metastable $c{\phantom{\rule{0.16em}{0ex}}}^{3}{\mathrm{\Pi}}_{u}^{-}\phantom{\rule{0.16em}{0ex}}2p\pi $ molecules is excited to $v=0,{N}^{+}=1$ Rydberg states ($n=17$ to 27) by a frequency-doubled tunable dye laser and ionized by static electric fields....

[Phys. Rev. A 101, 013425] Published Fri Jan 17, 2020

]]>We propose a technique for the accurate, flexible, and robust generation of arbitrary preselected coherent superpositions of two quantum states. It uses a sequence of two adiabatic pulses split by a phase jump serving as a control parameter. Each pulse has a chirped detuning, which induces a half cr...

[Phys. Rev. A 101, 013426] Published Fri Jan 17, 2020

]]>This article presents a computational study of the x-ray fluorescence induced by the irradiation of thin layered media by intense, short x-ray pulses. The treatment is based on a numerical solution of the Helmholtz wave equation both for the pump and for the fluorescence signal. Consistently with a ...

[Phys. Rev. A 101, 013818] Published Fri Jan 17, 2020

]]>Highly stable laser sources based on narrow atomic transitions provide a promising platform for direct generation of stable and accurate optical frequencies. Here we investigate a simple system operating in the high-temperature regime of cold atoms. The interaction between a thermal ensemble of ${}^{88}\mathrm{Sr}$...

[Phys. Rev. A 101, 013819] Published Fri Jan 17, 2020

]]>Here we present the results of a classical ghost imaging experiment accomplished at an XUV free-electron laser (FEL). To perform such experiment at an FEL source each x-ray pulse was transmitted through a moving diffuser, which created a noncorrelated speckled beam. This beam was then split in two i...

[Phys. Rev. A 101, 013820] Published Fri Jan 17, 2020

]]>A quantum system interacting with a dilute gas experiences irreversible dynamics. The corresponding master equation can be derived within two different approaches: The fully quantum description in the low-density limit and the semiclassical collision model, where the motion of gas particles is class...

[Phys. Rev. A 101, 012114] Published Thu Jan 16, 2020

]]>Thermodynamics is one of the fascinating branches of traditional physics which certifies the occurrence of many natural processes. On the other hand, quantum theory is the most acceptable description of the microscopic world. In the present paper, we have studied how the structure of quantum theory ...

[Phys. Rev. A 101, 012115] Published Thu Jan 16, 2020

]]>In this work we investigate the probability of violation of local realism under random measurements in parallel with the strength of these violations as described by resistance to white noise admixture. We address multisetting Bell scenarios involving up to seven qubits. As a result, in the first pa...

[Phys. Rev. A 101, 012116] Published Thu Jan 16, 2020

]]>To quantitatively analyze the control power of arbitrary $d$-dimensional controlled teleportation (CT), this paper investigates channels of entangled high-dimensional three-qudit standard Greenberger-Horne-Zeilinger (GHZ) and GHZ-type states. The upper bound on the controller's power is established in...

[Phys. Rev. A 101, 012323] Published Thu Jan 16, 2020

]]>We introduce two independent quantifications for three-mode and four-mode entanglement. We investigate the conversion of one type of nonclassicality, i.e., single-mode nonclassicality, into another type of nonclassicality, i.e., multimode entanglement, in beam splitters. We observe parallel behavior...

[Phys. Rev. A 101, 012324] Published Thu Jan 16, 2020

]]>Overcoming repeaterless bounds for the secret key rate capacity of quantum key distribution protocols is still a challenge with current technology. Luong *et al.* [Appl. Phys. B **122**, 96 (2016).] proposed a protocol to beat a repeaterless bound using one pair of quantum memories. However, the required ...

[Phys. Rev. A 101, 012325] Published Thu Jan 16, 2020

]]>We analyze the molecular electric dipole moments (PDMs) and static electric dipole polarizabilities of heteronuclear alkali dimers in their ground states by employing coupled-cluster theory, both in the nonrelativistic and four-component relativistic frameworks. The roles of electron correlations as...

[Phys. Rev. A 101, 012511] Published Thu Jan 16, 2020

]]>We present a simple method for determination of absolute vibrational numbering of isolated near dissociation levels in diatomic molecules, usually observed in cold-physics experiments. The method is based on the isotope shift and works even when energies of only two levels from one isotopologue and ...

[Phys. Rev. A 101, 012512] Published Thu Jan 16, 2020

]]>Atomic clocks based on an ${\mathrm{Al}}^{+}$ ion sympathetically cooled by a laser-cooled alkaline-earth-metal ion have achieved unprecedented accuracy. Here, we investigate theoretically interactions and charge-transfer dynamics of an ${\mathrm{Al}}^{+}$ ion immersed in an ultracold gas of Rb and Sr atoms. We calculate potential...

[Phys. Rev. A 101, 012705] Published Thu Jan 16, 2020

]]>We present a theoretical study of rotationally elastic and inelastic collisions between molecular nitrogen ions and Rb atoms in the sub-Kelvin temperature regime prevalent in ion-atom hybrid trapping experiments. The cross sections for rotational excitation and de-excitation collisions were calculat...

[Phys. Rev. A 101, 012706] Published Thu Jan 16, 2020

]]>We study spin-dipole oscillations of a binary fermionic mixture at nonzero temperatures. We apply the atomic-orbital method combined with a Monte Carlo technique based sampling to probe finite temperatures. Our results agree quantitatively with a recent experiment [G. Valtolina *et al.*, Nat. Phys. **13**...

[Phys. Rev. A 101, 013618] Published Thu Jan 16, 2020

]]>We investigate by statistical means a Bose-Einstein condensate held in a one-dimensional optical lattice whose phase undergoes a fast oscillation. The averaged potential experienced by the atoms yields a periodic potential having the same spatial period but with a renormalized depth. However, the at...

[Phys. Rev. A 101, 013619] Published Thu Jan 16, 2020

]]>The frequency-dependent shear and bulk viscosity spectral functions of an interacting Fermi gas at high temperature are computed using a systematic virial expansion of the stress tensor correlation function. The field-theoretical methods employed have interesting relations with many-body techniques, such as the Keldysh formalism and can be compared with numerical calculations.

[Phys. Rev. A 101, 013620] Published Thu Jan 16, 2020

]]>We present a *fermionic* description of nonequilibrium multilevel systems. Our approach uses the Keldysh path-integral formalism and allows us to take into account periodic drives, as well as dissipative channels. The technique is based on the Majorana fermion representation of spin-1/2 models which f...

[Phys. Rev. A 101, 013817] Published Thu Jan 16, 2020

]]>The electron affinity of the lanthanum atom was recently measured by slow-electron velocity map imaging in a photodetachment experiment [Y. Lu *et al.*, Phys. Rev. A **99**, 062507 (2019)]. Several detachment threshold energies have been measured, which correspond to different energy levels of the initia...

[Phys. Rev. A 101, 016501] Published Thu Jan 16, 2020

]]>In the context of closed quantum systems, when a system prepared in its ground state undergoes a sudden quench, the resulting Loschmidt echo can exhibit zeros, resembling the Fisher zeros in the theory of classical equilibrium phase transitions. These zeros lead to nonanalytical behavior of the corr...

[Phys. Rev. A 101, 012111] Published Wed Jan 15, 2020

]]>Localized solutions of the Dirac equation for an electron moving in free space and electromagnetic field lattices with periodic dependence on space-time coordinates (electromagnetic space-time crystals) are treated using the expansions in basis wave functions. The techniques for calculating these fu...

[Phys. Rev. A 101, 012112] Published Wed Jan 15, 2020

]]>We determine the characteristic of dissipative quantum transport in a coupled qubit network in the presence of on-site and off-diagonal external driving. The work is a generalization of the dephasing-assisted quantum transport where noise is beneficial to the transport efficiency. Using Floquet-Magn...

[Phys. Rev. A 101, 012113] Published Wed Jan 15, 2020

]]>We present a general procedure to implement a not gate by composite pulses robust against both offset uncertainties and control field variations. We define different degrees of robustness in this two-parameter space, namely, along one, two, or all directions. We show that the phases of the composite...

[Phys. Rev. A 101, 012321] Published Wed Jan 15, 2020

]]>In recent years there has been a great deal of focus on a globe-spanning quantum network, including linked satellites for applications ranging from quantum key distribution to distributed sensors and clocks. In many of these schemes, relativistic transformations may have deleterious effects on the p...

[Phys. Rev. A 101, 012322] Published Wed Jan 15, 2020

]]>Aiming to combine density functional theory (DFT) and wave-function theory, we study a mapping from the many-body interacting system to an effectively interacting Kohn-Sham system instead of a noninteracting Kohn-Sham system. Because a ground state of effectively interacting systems requires having ...

[Phys. Rev. A 101, 012510] Published Wed Jan 15, 2020

]]>The results of simulations of cooling based on sawtooth-wave adiabatic passage (SWAP) are presented, including the possibility of population leaking to states outside of the cycling transition. The amount of population leaking can be substantially suppressed compared to Doppler cooling, which could ...

[Phys. Rev. A 101, 013422] Published Wed Jan 15, 2020

]]>We analyze the control of the motion of a charged particle by means of an external electric field. The system is constrained to move along a given direction. The goal of the control is to change the speed of the particle in a fixed time with zero initial and final accelerations, while minimizing a c...

[Phys. Rev. A 101, 013423] Published Wed Jan 15, 2020

]]>The newly developed method of time-of-flight (TOF) momentum microscopy was used to analyze the cold electron emission from a Cs three-dimensional magneto-optical trap (MOT). Three-step resonant photoionization was implemented via two intermediate states ($6{P}_{3/2}$ pumped with an 852-nm laser and $7{S}_{1/2}$ w...

[Phys. Rev. A 101, 013424] Published Wed Jan 15, 2020

]]>We derive a computationally efficient expression of the photon-counting distribution for a uniformly illuminated array of single-photon detectors. The expression takes the number of single detectors, their quantum efficiency, and their dark count rate into account. Using this distribution we compute...

[Phys. Rev. A 101, 013815] Published Wed Jan 15, 2020

]]>We introduce the first-principle model describing frequency comb generation in a whispering-gallery-mode microresonator with the backscattering-induced coupling between the counterpropagating waves. The elaborated model provides deep insights and an accurate description of the complex dynamics of no...

[Phys. Rev. A 101, 013816] Published Wed Jan 15, 2020

]]>We analyze an autonomous thermoelectric engine composed of two superconducting qubits coupled to separate heat baths and connected by a Josephson junction. Work and heat are process quantities and not observables of the engine quantum system, but their rates can be derived from the steady-state expe...

[Phys. Rev. A 101, 010101(R)] Published Tue Jan 14, 2020

]]>The most common source of entangled photons is spontaneous parametric down-conversion (SPDC). The degree of energy and momentum entanglement in SPDC is determined by the nonlinear interaction volume. By reducing the length of a highly nonlinear material, we relax the longitudinal phase-matching cond...

[Phys. Rev. A 101, 011801(R)] Published Tue Jan 14, 2020

]]>Lipkin-Meshkov-Glick (LMG) models describe a set of $N$ qubits which are located at the corners of an $N$-dimensional simplex and embedded in an external magnetic field. Because of its high coordinate number, quantum correlations in the models are quite nontrivial. For instance, in the large-$N$ limit, tw...

[Phys. Rev. A 101, 012110] Published Tue Jan 14, 2020

]]>The quantum alternating operator ansatz (QAOA) is a promising gate-model metaheuristic for combinatorial optimization. Applying the algorithm to problems with constraints presents an implementation challenge for near-term quantum resources. This paper explores strategies for enforcing hard constrain...

[Phys. Rev. A 101, 012320] Published Tue Jan 14, 2020

]]>We report a precise determination of the lifetime of the $\left(4p\right){\phantom{\rule{0.16em}{0ex}}}^{2}{P}_{3/2}$ state of ${}^{40}\mathrm{Ca}^{+}$, ${\tau}_{{P}_{3/2}}=6.639\left(42\right)\phantom{\rule{0.16em}{0ex}}\mathrm{ns}$, using a combination of measurements of the induced light shift and scattering rate on a single trapped ion. Good agreement with the result of a recent high-level theoretical calculation, 6.69(6) ns ...

[Phys. Rev. A 101, 012509] Published Tue Jan 14, 2020

]]>We report on the realization of a magneto-optical trap (MOT) for metastable strontium operating on the 2.92-$\mu \mathrm{m}$ transition between the energy levels $5s5p{\phantom{\rule{0.16em}{0ex}}}^{3}{P}_{2}$ and $5s4d{\phantom{\rule{0.16em}{0ex}}}^{3}{D}_{3}$. The strontium atoms are initially captured in a MOT operating on the 461-nm transition between the energy levels $5{s}^{2}{\phantom{\rule{0.16em}{0ex}}}^{1}{S}_{0}$ and $5s5p{\phantom{\rule{0.16em}{0ex}}}^{1}{P}_{1}$...

[Phys. Rev. A 101, 013420] Published Tue Jan 14, 2020

]]>A comprehensive analysis of photon storage in a Rydberg state of ultracold ${}^{87}$Rb gas based on electromagnetically induced transparency is performed both experimentally and theoretically. The theoretical model shows that the retrieval efficiency is related to the decay of fringe visibility in Ramsey spectroscopy.

[Phys. Rev. A 101, 013421] Published Tue Jan 14, 2020

]]>The time-dependent response of a cold atom cloud illuminated by a laser beam after the light is switched on is investigated both experimentally and theoretically. A superradiant damping is discovered in the collective Rabi oscillations.

[Phys. Rev. A 101, 013617] Published Tue Jan 14, 2020

]]>In the past few decades, many works have been devoted to the study of exceptional points (EPs), i.e., exotic degeneracies of non-Hermitian systems. The usual approach in those studies involves the introduction of a phenomenological effective non-Hermitian Hamiltonian (NHH), where the gain and losses...

[Phys. Rev. A 101, 013812] Published Tue Jan 14, 2020

]]>We investigate the effect of the cumulative phase on the photon statistics of the three-mode state whose evolution is described by the trilinear Hamiltonian ${\widehat{H}}_{I}=i\hslash \kappa \left(\widehat{a}\widehat{b}{\widehat{c}}^{\u2020}-{\widehat{a}}^{\u2020}{\widehat{b}}^{\u2020}c\right)$, wherein the pump is taken to be quantized (and prepared in a coherent state) and the signal and idler modes are initial...

[Phys. Rev. A 101, 013813] Published Tue Jan 14, 2020

]]>Exceptional points, resulting from non-Hermitian degeneracies, have the potential to enhance the capabilities of quantum sensing. Thus, finding exceptional points in different quantum systems is vital for developing such future sensing devices. Taking advantage of the enhanced light-matter interacti...

[Phys. Rev. A 101, 013814] Published Tue Jan 14, 2020

]]>The dynamics of resonant tunneling via a spatially oscillating narrow well is investigated. The well generates a quasiresonance state, which can trap the incoming particles. Four spectral regimes are found: (1) the adiabatic regime, when the vibrations’ frequency is lower than the spectral width of ...

[Phys. Rev. A 101, 012109] Published Mon Jan 13, 2020

]]>We show theoretically how a correlation of multiple measurements on a qubit undergoing pure dephasing can be expressed as environmental noise filtering. The measurement of such correlations can be used for environmental noise spectroscopy, and the family of noise filters achievable in such a setting...

[Phys. Rev. A 101, 012314] Published Mon Jan 13, 2020

]]>The generation of genuine multipartite entangled states is challenging in practice. Here we explore an alternative route to this task, via autonomous entanglement engines which use only incoherent coupling to thermal baths and time-independent interactions. We present a general machine architecture,...

[Phys. Rev. A 101, 012315] Published Mon Jan 13, 2020

]]>The performance of the circuit-based surface-GKP bosonic quantum error correction code under noise due to finite squeezing of the GKP states and photon losses is investigated. The authors show under what conditions fault-tolerant quantum error correction is possible with the surface-GKP code.

[Phys. Rev. A 101, 012316] Published Mon Jan 13, 2020

]]>Entanglement is a central concept in quantum information and a key resource for many quantum protocols. In this work we propose and analyze a class of entanglement witnesses that detect the presence of entanglement in subsystems of experimental multiqubit stabilizer states. The witnesses we propose ...

[Phys. Rev. A 101, 012317] Published Mon Jan 13, 2020

]]>We present an efficient quantum algorithm for independent-set problems in graph theory, based on non-Abelian adiabatic mixing. We illustrate the performance of our algorithm with analysis and numerical calculations for two different types of graphs, with the number of edges proportional to the numbe...

[Phys. Rev. A 101, 012318] Published Mon Jan 13, 2020

]]>A “subspace” witness of entanglement, more robust than a typical state fidelity-based witness, is introduced and experimentally tested with a hybrid two-qubit system composed of electronic spins in diamond. Its straightforward implementation offers improved detection of specific genuine multipartite entangled states in noisy, intermediate-scale quantum processors.

[Phys. Rev. A 101, 012319] Published Mon Jan 13, 2020

]]>The quantum thermodynamical properties of (quasinormal) overdamped electromagnetic modes (eddy currents) are investigated in the context of the magnetic Casimir-Polder interaction. The role of the material response in terms of spatially local and nonlocal material models is discussed. In particular,...

[Phys. Rev. A 101, 012506] Published Mon Jan 13, 2020

]]>The complete Auger decay of ${\mathrm{Rb}}^{+}\left(3{d}^{-1}\right)$ including single and double processes is investigated using the distorted wave approximation. The direct double Auger decay was calculated by separating the knock-out and shake-off mechanisms. For single Auger decay of the $3{d}^{-1}$ hole state, it is generally believ...

[Phys. Rev. A 101, 012507] Published Mon Jan 13, 2020

]]>Electronic structure enhancement factors of simultaneous parity and time-reversal violation ($\mathcal{P},\mathcal{T}$ violation) caused by an electric dipole moment of the electron (eEDM) and scalar-pseudoscalar nucleon-electron current (SPNEC) interactions are reported for various metal monohydroxides, several of which...

[Phys. Rev. A 101, 012508] Published Mon Jan 13, 2020

]]>The dynamics of charge-state fractions of relativistic gold-ion beams stripped by foils from Be to Au is investigated in the 100 MeV/u to 10 GeV/u energy range. Calculations of the fractions as a function of foil thickness are performed using the recently developed breit code based on the analytical...

[Phys. Rev. A 101, 012704] Published Mon Jan 13, 2020

]]>We study the collective dynamics of a clean Floquet system of cold atoms, numerically simulating two realistic setups based on a regular chain of interacting Rydberg atoms driven by laser fields. In both cases, the population evolution and its Fourier spectrum display clear signatures of a discrete ...

[Phys. Rev. A 101, 013417] Published Mon Jan 13, 2020

]]>The interaction of matter with a quantized electromagnetic mode is considered. Representing a strong exciting field, the mode is assumed to contain a large number of photons. As a result, the material response is highly nonlinear: the completely quantized description results in generation of high ha...

[Phys. Rev. A 101, 013418] Published Mon Jan 13, 2020

]]>We theoretically investigate the spin-dipole oscillation of a strongly interacting Fermi gas confined by a harmonic trapping potential. By using a diagrammatic strong-coupling theory combined with a local density approximation and a sum rule approach, we study the temperature dependence of the spin-...

[Phys. Rev. A 101, 013610] Published Mon Jan 13, 2020

]]>Dipole oscillation is studied in a normal phase of a trapped Bose-Fermi-mixture gas composed of single-species bosons and single-species fermions. Applying the moment method to the linearized Boltzmann equation, we derive a closed set of equations of motion for the center-of-mass position and moment...

[Phys. Rev. A 101, 013611] Published Mon Jan 13, 2020

]]>We realize a double-path multimode matter wave interferometer with spinor Bose-Einstein condensate and observe clear spatial interference fringes as well as a periodic change of the visibility in the time domain, which we refer to as the time domain interference and which is different from the tradi...

[Phys. Rev. A 101, 013612] Published Mon Jan 13, 2020

]]>Two-dimensional spin-orbit-coupled Fermi gases subject to $s$-wave pairing can be driven into a topological phase by increasing the Zeeman spin splitting beyond a critical value. In the topological phase, the system exhibits the hallmarks of chiral $p$-wave superfluidity, including exotic Majorana excit...

[Phys. Rev. A 101, 013613] Published Mon Jan 13, 2020

]]>Cooper-pair formation in a system of imbalanced fermions leads to the well-studied Fulde-Ferrell or Larkin-Ovchinnikov superfluid state. In the former case the system forms spontaneous phase gradients while in the latter case it forms a stripelike or a crystal-like density gradient. We show that in ...

[Phys. Rev. A 101, 013614] Published Mon Jan 13, 2020

]]>We develop an effective field theory to describe the superfluid pairing in strongly interacting fermions with arbitrary short-range attractions by extending Kaplan's idea of coupling fermions to a fictitious boson state [presented in Nucl. Phys. B **494**, 471 (1997)]. This boson field is assigned with ...

[Phys. Rev. A 101, 013615] Published Mon Jan 13, 2020

]]>We use state-of-the-art density matrix renormalization group calculations in the canonical ensemble to determine the phase diagram of the dipolar Bose-Hubbard model on a finite cylinder. We consider several observables that are accessible in typical optical lattice setups and assess how well these q...

[Phys. Rev. A 101, 013616] Published Mon Jan 13, 2020

]]>Thermal states of light are widely used in quantum optics due to their correlation properties. As is well known, their correlation properties and the photon-number distribution as a whole are strongly dependent on the mode number selected by the detection scheme. The same changes can be caused by ph...

[Phys. Rev. A 101, 013811] Published Mon Jan 13, 2020

]]>We study protective quantum measurements in the presence of an environment and decoherence. We consider the model of a protectively measured qubit that also interacts with a spin environment during the measurement. We investigate how the coupling to the environment affects the two characteristic pro...

[Phys. Rev. A 101, 012108] Published Fri Jan 10, 2020

]]>Suppose a set of $m$-partite, $m\ge 3$, pure orthogonal fully separable states is given. We consider the task of distinguishing these states perfectly by local operations and classical communication (LOCC) in different $k$ partitions, $1<k<m$. Based on this task, it is possible to classify the sets of pr...

[Phys. Rev. A 101, 012311] Published Fri Jan 10, 2020

]]>The entanglement witness is an important and experimentally applicable tool for entanglement detection. In this paper, we provide a nonlinear improvement of any entanglement witness for $2\otimes d$ quantum systems. Compared with any existing entanglement witness, the improved separability criterion only nee...

[Phys. Rev. A 101, 012312] Published Fri Jan 10, 2020

]]>The remarkable phenomenon of catalyst tells us that adding a catalyst could help state transformation. In this paper, we consider the problem of catalyst-assisted probabilistic coherence distillation for mixed states under strictly incoherent operations. To this end, we first present the necessary a...

[Phys. Rev. A 101, 012313] Published Fri Jan 10, 2020

]]>Classical theories of radiation reaction predict that the electron motion is confined to the plane defined by the electron's instantaneous momentum and the force exerted by the external electromagnetic field. However, in the quantum radiation reaction regime, where the recoil exerted by individual q...

[Phys. Rev. A 101, 012505] Published Fri Jan 10, 2020

]]>Interspecies interaction strength between ${}^{7}$Li and ${}^{87}$Rb atoms through cross-dimensional relaxation of two-element gas mixtures is measured experimentally and calculated with Monte Carlo simulations. A disagreement between those two results provides an interesting challenge for interpretation and may stimulate further work.

[Phys. Rev. A 101, 012703] Published Fri Jan 10, 2020

]]>We demonstrate buffer-gas cooling, high-resolution spectroscopy, and cycling fluorescence of cold barium monofluoride (BaF) molecules. Our source produces an intense and internally cold molecular beam containing the different BaF isotopologues with a mean forward velocity of $190\phantom{\rule{0.16em}{0ex}}\mathrm{m}/\mathrm{s}$. For a well-colli...

[Phys. Rev. A 101, 013413] Published Fri Jan 10, 2020

]]>Two-electron wave packets found in driven planar helium follow a classical periodic orbit without spreading and are localized in nonlinear resonance islands of the classical phase space. The general mechanism that produces these nondispersive wave packets is the near-resonant coupling between highly...

[Phys. Rev. A 101, 013414] Published Fri Jan 10, 2020

]]>We develop a Hamiltonian formalism to study energy and position (momentum) correlations between a single Stokes photon and a single material excitation that are created as a pair in the spontaneous Raman scattering process. Our approach allows for intuitive separation of the effects of spectral line...

[Phys. Rev. A 101, 013415] Published Fri Jan 10, 2020

]]>We study the ultrafast dissociation of singly and doubly ionized ${\mathrm{N}}_{2}\mathrm{O}$ molecules using strong IR-laser pump and IR-laser probe techniques in combination with the three-body $({\mathrm{N}}^{+}+{\mathrm{N}}^{+}+{\mathrm{O}}^{+})$ coincidence measurement. Two time-dependent kinetic energy release bands are observed and assigned as ultrafast evolut...

[Phys. Rev. A 101, 013416] Published Fri Jan 10, 2020

]]>The ability to directly measure the momentum distribution of quantum gases is both unique to these systems and pivotal in extracting many other important observables. Here we use Raman transitions to measure the momentum distribution of a weakly interacting Fermi gas in a harmonic trap. For narrow a...

[Phys. Rev. A 101, 013609] Published Fri Jan 10, 2020

]]>We study the generation of single-photon pulses with the tailored temporal shape via nonlocal spectral filtering. A shaped photon is heralded from a time-energy entangled photon pair upon spectral filtering and time-resolved detection of its entangled counterpart. We show that the temporal shape of ...

[Phys. Rev. A 101, 013808] Published Fri Jan 10, 2020

]]>We study a dynamical phase transition in optical bistable systems subject to a time-periodic driving field. The phase transition occurs in the structure of a limit cycle as a function of the frequency of the driving field. In the thermodynamic limit, a single limit cycle is divided into two separate...

[Phys. Rev. A 101, 013809] Published Fri Jan 10, 2020

]]>Typically, optical microscopy uses the wavelike properties of light to image a scene. However, photon arrival times provide more information about emitter properties than the classical intensity alone. Here we show that the Hanbury Brown and Twiss experiment (second-order correlation function) measu...

[Phys. Rev. A 101, 013810] Published Fri Jan 10, 2020

]]>We present an extension of the Löwdin strategy to find arbitrary matrix elements of generic Slater determinants. Our method applies to an arbitrary number of fermionic operators, even in the case of a singular overlap matrix.

[Phys. Rev. A 101, 012105] Published Thu Jan 09, 2020

]]>According to the Copenhagen interpretation of quantum mechanics a measurement leads to the collapse of a quantum system. A unified description of a quantum system before and after measurement of the position ${\mathit{r}}_{1}^{a}$ and the spin ${s}_{1}^{a}$ of one of its electrons is proposed based on the conditional amplitude ...

[Phys. Rev. A 101, 012106] Published Thu Jan 09, 2020

]]>We demonstrate the quantum-enhanced supervised classification of vectors in a nitrogen-vacancy ($NV$)–center system using the algorithm of Lloyd, Mohseni, and Rebentrost (arXiv:1307.0411). A ${}^{13}\mathrm{C}$ nuclear spin is employed to encode the vectors with the spin-triplet state of the $NV$ center as an ancilla. ...

[Phys. Rev. A 101, 012307] Published Thu Jan 09, 2020

]]>Starting from explicitly constructing an entanglement witness for the mixture of a Dicke state with white noise (noisy Dicke state), we provide an entanglement criterion for any multiqubit state. The criterion is necessary and sufficient for noisy $W$ states of three, four, and five qubits. We demonst...

[Phys. Rev. A 101, 012308] Published Thu Jan 09, 2020

]]>We describe a method for creating small quantum processors in a crystal stoichiometric in an optically active rare-earth ion. The crystal is doped with another rare earth, creating an ensemble of identical clusters of surrounding ions, whose optical and hyperfine frequencies are uniquely determined ...

[Phys. Rev. A 101, 012309] Published Thu Jan 09, 2020

]]>We propose a two-qubit experiment for validating tunable antiferromagnetic XX interactions in quantum annealing. Such interactions allow the time-dependent Hamiltonian to be nonstoquastic, and the instantaneous ground state can have negative amplitudes in the computational basis. Our construction re...

[Phys. Rev. A 101, 012310] Published Thu Jan 09, 2020

]]>A recent realization of three-dimensional optical lattice clocks circumvents short-range collisional clock shifts which have been the bottle neck towards higher precision; the long-range electronic dipole-dipole interaction between the atoms becomes the primary source of clock shift due to interatom...

[Phys. Rev. A 101, 012504] Published Thu Jan 09, 2020

]]>Recent investigations by Fuchs *et al.* [Matthias Fuchs, Mariano Trigo, Jian Chen, Shambhu Ghimire, Sharon Shwartz, Michael Kozina, Mason Jiang, Thomas Henighan, Crystal Bray, Georges Ndabashimiye *et al.*, Anomalous nonlinear X-ray Compton scattering, Nat. Phys. **11**, 964 (2015)] revealed an anomalous fr...

[Phys. Rev. A 101, 013409] Published Thu Jan 09, 2020

]]>In quantum theory, the description of radiation by a system of charged particles in stationary and nonstationary cases requires different approaches. While radiative processes in stationary systems are covered in textbooks, the emission of radiation by nonstationary systems driven by an external tim...

[Phys. Rev. A 101, 013410] Published Thu Jan 09, 2020

]]>To solve the time-dependent Schrödinger equation in spatially inhomogeneous pulses of electromagnetic radiation, we propose an iterative semiclassical complex trajectory approach. In numerical applications, we validate this method against *ab initio* numerical solutions by scrutinizing (a) electronic ...

[Phys. Rev. A 101, 013411] Published Thu Jan 09, 2020

]]>The above-threshold ionization (ATI) of argon atoms in intense circularly polarized laser fields has been investigated by numerically solving the three-dimensional time-dependent Schrödinger equation and the classical Newton-Lorentz equation. There are obvious angular shifts of the photoelectron mom...

[Phys. Rev. A 101, 013412] Published Thu Jan 09, 2020

]]>We propose a practical protocol to generate and observe a non-Abelian geometric phase using a periodically driven Raman process in the hyperfine ground-state manifold of atoms in a dilute ultracold gas. Our analysis is based upon recent developments and application of Floquet theory to periodically ...

[Phys. Rev. A 101, 013606] Published Thu Jan 09, 2020

]]>It was recently found that, under the action of the spin-orbit coupling (SOC) and Zeeman splitting (ZS), binary BEC with intrinsic cubic nonlinearity supports families of gap solitons, provided that the kinetic energy is negligible in comparison with the SOC and ZS terms. We demonstrate that, also u...

[Phys. Rev. A 101, 013607] Published Thu Jan 09, 2020

]]>We consider a spin-imbalanced Fermi gas at zero temperature in the normal phase on the BCS side of the BCS-BEC crossover and around unitarity. We compute the critical polarization for pairing, the correlated occupation numbers, and the contact in an extension of particle-particle random-phase approx...

[Phys. Rev. A 101, 013608] Published Thu Jan 09, 2020

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