We consider the Bose gas on a d-dimensional anisotropic lattice employing the imperfect (mean-field) gas as a prototype example. We study the dimensional crossover arising as a result of varying the dispersion relation at finite temperature T. We analyze in particular situations where one of the relevant effective dimensionalities is located at or below the lower critical dimension, so that the Bose-Einstein

Physical processes near threshold in strong field ionization are complex owing to the important role of many intermediate states. Two typical near-threshold processes in few-cycle laser pulses, generations of Rydberg electrons and Terahertz wave, are investigated using the Classical Trajectory Monte Carlo simulations. Mapping final energies of electrons to the tunneling coordinates, the two processes

A major motivation for building a quantum computer is that it provides a tool to efficiently simulate strongly correlated quantum systems. In this work, we present a detailed roadmap on how to simulate a two-dimensional electron gas—cooled to absolute zero and pierced by a strong transversal magnetic field—on a quantum computer. This system describes the setting of the Fractional Quantum Hall Effect

The question of how quantities, like entanglement and coherence, depend on the number of copies of a given state ρ is addressed. This is a hard problem, often involving optimizations over Hilbert spaces of large dimensions. Here, we propose a way to circumvent the direct evaluation of such quantities, provided that the employed measures satisfy a self-similarity property. We say that a quantity ${\cal

We study a system of strongly interacting one-dimensional (1D) bosons on a ring pierced by a synthetic magnetic flux tube. By the Fermi-Bose mapping, this system is related to the system of spin-polarized non-interacting electrons confined on a ring and pierced by a solenoid (magnetic flux tube). On the ring there is an external localized delta-function potential barrier V(ϕ)=gδ(ϕ−ϕ0). We study the

We investigate interactions between the proton spin, the deuteron spin, and the orbital angular momentum in the electronic ground state of the HD molecule. These interactions lead to hyperfine splittings of molecular energy levels. Our numerical results for the first rotational level agree well with the currently most accurate measurement performed by Ramsey {} in the 1950s. Knowledge of the hyperfine

Absolutely Maximally Entangled (AME) states are maximally entangled for every bipartition of the system. They are crucial resources for various quantum information protocols. We present techniques for verifying either two AME states are equivalent concerning Stochastic Local Operations and Classical Communication (SLOCC). The conjecture that for a given multipartite quantum system all AME states are

We develop a numerical linked cluster expansion (NLCE) method that can be applied directly to inhomogeneous systems, for example Hamiltonians with disorder and dynamics initiated from inhomogeneous initial states. We demonstrate the method by calculating dynamics for single-spin expectations and spin correlations in two-dimensional spin models on a square lattice, starting from a checkerboard state

Using electron spectroscopy technique we have measured the absolute double differential cross sections (DDCS) of electrons emitted in collisions of 200 keV protons on He, CH4 and O2 and 5.5 MeV/u bare C ions colliding on O2. The emitted electrons were measured in the energy range from 1 eV to 400 eV for He and CH4 targets and upto 600 eV for O2 to include the K-LL Auger line of oxygen. The electrons

We study the interaction between a topological insulator nanoparticle and a quantum dot subject to an applied electric field. The electromagnetic response of the topological insulator is derived from axion electrodynamics in the quasistatic approximation. Localized modes are quantized in terms of dipolar bosonic modes, which couples dipolarly to the quantum dot. Hence, we treat the hybrid as a two-level

X-ray production cross sections for M3, M4 and M5 subshells of Pt and Au by electron impact were experimentally determined at incident energies ranging between 2.8 and 28 keV. To this purpose, Pt and Au thick targets were irradiated by an electron beam in a field emission gun scanning electron microscope, and the x-ray emission spectra were recorded with an energy dispersive spectrometer. The x-ray

In the recent work [A.~Yamaguchi {}, Phys. Rev. Lett. 123 , 113201 (2019)] Cd has been identified as an excellent candidate for a lattice clock. Here, we carried out computations needed for further clock development and made an assessment of the higher-order corrections to the light shift of the 5s21S0 -, 5s5p3P0o clock transition. We carried out calculations of the magnetic dipole and electric quadrupole

A theoretical study of the rotational dynamics of a linear polar molecule in a two-color non-resonant cw laser field is presented. By systematically considering the interactions of this field with the electric dipole moment, polarizability and hyperpolarizability of the molecule, the implications that the symmetries of the Hamiltonian have on the rotational dynamics are explored in a regime where the

We study the magnetic phases of a non-equilibrium spin chain, where coherent interactions between neighboring lattice sites compete with alternating gain and loss processes. This competition between coherent and incoherent dynamics induces transitions between magnetically aligned and highly mixed phases, across which the system changes from a low- to an effective infinite-temperature state. We show

The simple single-channel static-exchange approximation completely ignores correlation between the continuum and molecular ion electrons. We present cross sections and molecular frame photoelectron angular distributions with both A grid-based variational method described here makes such single-channel calculations possible on larger systems without local-exchange approximations. \rrl{Illustrative calculations

DOI:https://doi.org/10.1103/PhysRevA.102.019901

We provide an efficient method for the calculation of high-gain, twin-beam generation in waveguides derived from a canonical treatment of Maxwell’s equations. Equations of motion are derived that naturally accommodate photon generation via spontaneous parametric down-conversion (SPDC) or spontaneous four-wave mixing (SFWM), and also include the effects of both self-phase modulation (SPM) of the pump

We report a previously unknown synchronization phenomenon, which is simulated with an optomechanical system driven by two equally strong fields with different frequencies. Once the frequencies of the driving fields are properly matched, the amplitude and phase of the mechanical oscillator coupled to the cavity field, together with its frequency spectrum, will be frozen on one of determined trajectories

The protocol proposed in the commented article can certify zero discord, however, it fails to non-zero discord for some states. Further, the protocol is less efficient than calculating discord via performing full quantum state tomography.

The authors of the preceding Comment [P.~Kumar and K.~Snizhko, preceding Comment, Phys. Rev. A , ] made two critical remarks regarding the protocol for detecting and quantifying quantumness of separable states presented in our paper [M.~A. Hunt et al, Phys. Rev. A 100, 022321 (2019)]. One is that our protocol is not `experiment friendly’ in comparison to full quantum state tomography. The other is

Quantum random number generator (QRNG) can theoretically generate unpredictable random numbers with perfect devices, which is an ideal and secure source of random numbers for cryptography. However, the practical implementations always contain imperfections, which will greatly influence the randomness of the final output and even open loophole to eavesdroppers. Recently, J. Thewes et.al. experimentally

We study a prototypical model of two coupled two-level systems, where the competition between coherent and dissipative coupling gives rise to a rich phenomenology. In particular, we analyze the case of asymmetric coupling, as well as the limiting case of chiral (or one-way) coupling. We investigate various quantum optical properties of the system, including its steady state populations, power spectrum

We determine the quantum Cramr-Rao bound for the precision with which the oscillator frequency and damping constant of a damped quantum harmonic oscillator in an arbitrary Gaussian state can be estimated. This goes beyond standard quantum parameter estimation of a single mode Gaussian state for which typically a mode of fixed frequency is assumed. We present a scheme through which the frequency estimation

DOI:https://doi.org/10.1103/PhysRevA.102.010001

We study the scattering of a single photon in the surface plasmon polariton mode propagating on a two-dimensional surface, by a two-level quantum system in the regime where the photon wavelength becomes comparable or smaller than the size of the electron wave function. In this interesting regime, the scattering spectral signature becomes highly dependent on the shape of the ground and excited state

In this study, the recurrent fluorescence of naphthalene ions was investigated using an electrostatic ion beam trap. The number of photons from the recurrent fluorescence on the D$_{2} $ D0 transition was measured as a function of time, after the production of naphthalene ions by electron impact. The emission of photons was observed over a time range of approximately 10 ms. The variation in the number

Open quantum walks (OQWs) describe a quantum walker on an underlying graph whose dynamics is purely driven by dissipation and decoherence. Mathematically, they are formulated as completely positive trace preserving (CPTP) maps on the space of density matrices for the walker on the graph. Any microscopically derived OQW must include the possibility of remaining on the same site on the graph when the

We have developed a novel experimental technique to study charge and energy flow processes in sub-electronvolt collisions between oppositely charged, internally cold, ions of atoms, molecules and clusters. Two ion beams are stored in separate rings of the cryogenic ion-beam storage facility DESIREE, and merged in a common straight section where a set of biased drift tubes is used to control the center-of-mass

We analyze the continuous operation of the nine-qubit error correcting Bacon-Shor code with all noncommuting gauge operators measured at the same time. The error syndromes are continuously monitored using cross-correlations of sets of three measurement signals. We calculate the logical error rates due to X, Y and Z errors in the physical qubits and compare the continuous implementation with the discrete

We present optimal schemes, based on photon number measurements, for Gaussian state tomography and for Gaussian process tomography. An n-mode Gaussian state is completely specified by 2n2+3n parameters. Our scheme requires exactly 2n2+3n distinct photon number measurements to tomograph the state and is therefore optimal. Further, we describe an optimal scheme to characterize Gaussian processes by using

Photoionization of an atom in the presence of a neighboring atom of different species is studied. The latter first undergoes resonant photoexcitation, leading to an autoionizing state of the diatomic system. Afterwards, the excitation energy is transferred radiationlessly via a two-center Auger process to the other atom, causing its ionization. Assuming a fixed internuclear distance, it has been predicted

We simulate the pump-probe experiments of lasing in molecular nitrogen ions with particular interest on the effects of rotational wave-packet dynamics. Our computations demonstrate that the coherent preparation of rotational wave packets in N2+ by an intense short non-resonant pulse results in a modulation of the subsequent emission from B2Σu+→X2Σg+ transitions induced by a resonant seed pulse. We

A new explicitly correlated functional form for expanding the wave function of an N-particle system with arbitrary angular momentum and parity is presented. We develop the projection-based approach, numerically exploited in our previous work [J. Chem. Phys. {149}, 184105 (2018)], to explicitly correlated Gausssians with one-axis shifted centers and derive the matrix elements for the Hamiltonian and

We devise a protocol to build 1D time-dependent quantum walks in 1D maximizing the spatial spread throughout the procedure. We allow only one of the physical parameters of the coin-tossing operator to vary, i.e. the angle θ, such that for θ=0 we have the σ̂z, while for θ=π/4 we obtain the Hadamard gate. The optimal θ sequences present non-trivial patterns, with mostly θ≈0 alternated with θ≈π/4 values

In this article we use time-dependent Josephson coupling to enhance unconventional photon blockade in a system of two coupled nonlinear bosonic modes which are initially loaded with weakly populated coherent states, so the evolution is restricted to the manifold of up to two field quanta. Using numerical optimal control, we find the optimal coupling which minimizes the two-photon occupation of one

We analyze the difference between ex ante and ex post equilibria in classical games played with the assistance of a nonlocal (quantum or no-signaling) resource. In physics, the playing of these games is known as performing bipartite Bell-type experiments. By analyzing the Clauser-Horn-Shimony-Holt game, we find a constructive procedure to find two-person Bayesian games with a nonlocal (i.e., no-signaling

We study the hardness of classically simulating boson sampling with superposition and Gaussian input states at nonzero photon indistinguishability. We find that, similar to regular boson sampling, distinguishability causes exponential attenuation of the many-photon interference terms in both these boson sampling variants. For superposition sampling, we find that it is not simulable with out method

Quantum error correction requires decoders that are both accurate and efficient. To this end, union-find decoding has emerged as a promising candidate for error correction on the surface code. In this work, we benchmark a weighted variant of the union-find decoder on the toric code under circuit-level depolarizing noise. This variant preserves the almost-linear time complexity of the original while