The recent observation [A. Oosawa et al., J. Phys. Condens. Matter 11, 265 (1999)] of the field-induced Neel ordering in spin-gap magnetic compound TlCuCl3 is interpreted as a Bose-Einstein condensation magnons. A Hartree-Fock-type calculation based on this picture shown to describe temperature dependence magnetization well.

Abstract Variational quantum eigensolvers (VQEs) are garnering significant attention for their ability to estimate the ground-state energy of target Hamiltonians. In particular, digital-analog computation (DAQC) stands out as a crucial platform VQEs in noisy intermediate-scale (NISQ) era, leveraging single-qubit operations and natural time evolution governed by parameterized On other hand, variational quantum-neural hybrid eigensolver is also vital technique that enhances accuracy estimating...

A theoretical interpretation is given on the magnetization process of CsCuCl 3 showing a small jump for external field applied parallel to c -axis. It shown that quantum fluctuations are so important in this S =1/2 triangular antiferromagnet they can change ground-state spin structure. The observed successfully explained as flop caused by effect.

We derive coupled equations of motion for the condensate (superfluid) and noncondensate (normal fluid) degrees freedom in a trapped Bose gas at finite temperatures. Our results are based on Hartree-Fock-Popov approximation time-dependent wave function, thermodynamic local equilibrium atoms. In special case uniform weakly interacting gas, our hydrodynamic shown to be consistent with two-fluid Landau. The collective modes parabolically include analog out-of-phase second-sound mode superfluid...

We calculate the uniform magnetization of a spin-1/2 Heisenberg square lattice antiferromagnet at $T=0$ in magnetic fields up to saturation field framework spin-wave theory including quantum corrections second order $1/S$. External generally suppresses zero-point fluctuations, which leads an upward curvature curve low and logarithmic singularity close saturation.

The study of interaction between the particle and lattice degrees freedom is one central interests in quantum many-body systems. Z2 Bose-Hubbard model has been proposed to describe ultracold bosons a dynamical optical lattice. This introduces by placing half-spins on bonds neighboring sites. In this study, we investigate effect spin fluctuations ground state using density-matrix renormalization group method. By calculating structure factor compressibility, show that there phase transition...

We present the first spatially resolved images of spin waves in a gas. The complete longitudinal and transverse field as function time space is reconstructed. Frequencies damping rates for standing-wave mode are extracted compared with theory.

We extend our recent work on the two-fluid hydrodynamics of a Bose-condensed gas by including collisions involving both condensate and noncondensate atoms. These are essential for establishing state local thermodynamic equilibrium between noncondensate. Our theory is more general than usual Landau theory, to which it reduces in appropriate limit, that allows one describe situations complete two components has not been reached. The exchange atoms associated with new relaxational mode gas.

A Boltzmann machine is a powerful tool for modeling probability distributions that govern the training data. thermal equilibrium state typically used learning to obtain suitable distribution. The consists of calculating gradient loss function given in terms average, which most time-consuming procedure. Here, we propose method implement by using noisy intermediate-scale quantum devices. We prepare an initial pure contains all possible computational basis states with same amplitude, and apply...

The ground-state spin structures of hexagonal antiferromagnets such as CsCuCl 3 in a strong magnetic field are studied by mapping the problem onto an equivalent Bose-gas problem. system close to saturation is transformed low-density Bose gas which has two minima single-particle energy band. expansion applied and structure just below determined.

We present a kinetic theory for dilute noncondensed Bose gas of two-level atoms that predicts the transient spin segregation observed in recent experiment. The underlying mechanism driving currents is due to mean-field effect arising from quantum interference between direct and exchange scattering different states. numerically solve Boltzmann equation, using one-dimensional model, find excellent agreement with experimental data.

Quantum annealing (QA) is one of the methods to prepare a ground state problem Hamiltonian. In absence noise, QA can accurately estimate ground-state energy if adiabatic condition satisfied. However, in practice, systems are known suffer from decoherence. Meanwhile, considerable research effort has been devoted noisy intermediate-scale quantum (NISQ) computation. For practical NISQ computation, many error-mitigation (EM) have proposed mitigate effects noise. This paper proposes strategy...

At zero field CsCuCl 3 is known to form a helical spin structure along the c -axis and 120° in -plane. This paper discusses theoretically effect of magnetic applied perpendicular -axis, which breaks axial symmetry. First classical ground state studied. The transverse deforms causes continuous phase transition from (i.e. incommensurate) commensurate state, as increases. Detailed studies are made helix pitch nature incommensurate functions field. has nontrivial degeneracy, lifted by quantum...

We study surface modes of the condensate in presence a rotating thermal cloud an axisymmetric trap. By considering collisions that transfer atoms between and noncondensate, we find $m>0$ modes, which rotate same sense as cloud, damp less strongly than $m<0$ where $m$ is polarity excitation. show above critical angular rotation frequency, equivalent to Landau stability criterion, become dynamically unstable, leading possibility vortex nucleation. also generalize our analysis treat case...

We study single-particle excitations of a Bose gas in an optical lattice the Mott-insulator phase. The characteristic feature spectrum phase is existence energy gap between particle and hole excitations. show that excitation energies associated can be directly probed by output-coupling experiment. apply general expression for output current derived Luxat Griffin, which given terms Green's functions trapped gas, to using Bose-Hubbard model. momentum-resolved exhibits two peaks corresponding...

We study sound propagation in a uniform superfluid gas of Fermi atoms the unitary limit. The existence normal and components leads to appearance two modes collisional regime, referred as first second sound. is particular interest it clear signal component. Using Landau's two-fluid hydrodynamic theory, we calculate velocities these weights density response function. latter used sudden modification external potential generating pulse propagation. amplitude which proportional weight function,...

We investigate Landau damping of Bogoliubov excitations in a dilute Bose gas moving an optical lattice at finite temperatures. Using one-dimensional tight-binding model, we explicitly obtain the rate, sign which determines stability condensate. find that changes certain condensate velocity, is exactly same as critical velocity determined by criterion superfluidity. This coincidence velocities reveals microscopic mechanism instability. instability shows thermal cloud plays crucial role...

We study the Higgs amplitude mode in $s$-wave superfluid state on honeycomb lattice inspired by recent cold atom experiments. consider attractive Hubbard model and focus vicinity of a quantum phase transition between semimetal phases. On either side transition, we find collective excitations that are stable against decay into quasiparticle pairs. In phase, modes have ``Cooperon'' exciton character. These smoothly evolve across become Anderson-Bogoliubov phase. The accommodated within window...

We develop the moment method for Bose-Einstein condensates at finite temperatures that enable us to study collective sound modes from hydrodynamic collisionless regime. In particular, we investigate excitations in a weakly interacting dilute Bose gas by applying Zaremba-Nikuni-Griffin equation, which is coupled equation of Boltzmann with generalized Gross-Pitaevskii equation. Utilizing method, crossover regime between and regimes are investigated detail. regime, second mode loses weight...

Quantum search algorithms, such as Grover's algorithm, are expected to efficiently solve constrained combinatorial optimization problems. However, implementing a quantum algorithm for solving the traveling salesman problem (TSP) on circuit poses potential challenge because current algorithms TSP assume that an initial state of equal superposition feasible solution states satisfying constraint is already prepared priori. The time complexity brute-force preparation increases exponentially with...