arXiv subjects

I. E. Mazets

Publications and source records attributed to I. E. Mazets.

At least 19 recordsLinked to original sources

arXiv2018

Integer partition manifolds and phonon damping in one dimension

We develop a quantum model based on the correspondence between energy distribution between harmonic oscillators and the partition of an integer number. A proper choice of the interaction Hamiltonian acting within this manifold of states allows us to examine both the quantum typicality and the non-exponential relaxation in the same system. A quantitative agreement between the field-theoretical calculations and the exact diagonalization of the Hamiltonian is demonstrated.

cond-mat.quant-gas↗

arXiv2015

Many-body physics of slow light

We present a quantum theory of slow light beyond the weak probe pulse approximation. By reduction of the full Hamiltonian of the system to an effective Hamiltonian for a single quantum field we demonstrate that the concept of dark-state polaritons can be introduced even if the linearized approach is no longer valid. The developed approach allows us to study the evolution of non-classical quantum states of the polariton field.

quant-ph↗

arXiv2011

Dephasing in coherently-split quasicondensates

We numerically model the evolution of a pair of coherently split quasicondensates. A truly one-dimensional case is assumed, so that the loss of the (initially high) coherence between the two quasicondensates is due to dephasing only, but not due to the violation of integrability and subsequent thermalization (which are excluded from the present model). We confirm the subexponential time evolution of the coherence between two quasicondensates $\propto \exp [-(t/t_0)^{2/3}]$, experimentally observed by S. Hofferberth {\em et. al.}, Nature {\bf 449}, 324 (2007). The characteristic time $t_0$ is found to scale as the square of the ratio of the linear density of a quasicondensate to its temperature, and we analyze the full distribution function of the interference contrast and the decay of the phase correlation.

cond-mat.quant-gas↗

arXiv2011

Dynamics and kinetics of quasiparticle decay in a nearly-one-dimensional degenerate Bose gas

We consider decay of a quasiparticle in a nearly-one-dimensional quasicondensate of trapped atoms, where virtual excitations of transverse modes break down one-dimensionality and integrability, giving rise to effective three-body elastic collisions. We calculate the matrix element for the process that involves one incoming quasiparticle and three outgoing quasiparticles. Scattering that involves low-frequency modes with high thermal population results in a diffusive dynamics of a bunch of quasiparticles created in the system.

cond-mat.quant-gas↗

arXiv2010

Weakly interacting Bose gas in the one-dimensional limit

We prepare a chemically and thermally one-dimensional (1d) quantum degenerate Bose gas in a single microtrap. We introduce a new interferometric method to distinguish the quasicondensate fraction of the gas from the thermal cloud at finite temperature. We reach temperatures down to $kT\approx 0.5\hbarω_\perp$ (transverse oscillator eigenfrequency $ω_\perp$) when collisional thermalization slows down as expected in 1d. At the lowest temperatures the transverse momentum distribution exhibits a residual dependence on the line density $n_{1d}$, characteristic for 1d systems. For very low densities the approach to the transverse single particle ground state is linear in $n_{1d}$.

cond-mat.quant-gas↗

arXiv2010

Thermalization in a quasi-1D ultracold bosonic gas

We study the collisional processes that can lead to thermalization in one-dimensional systems. For two body collisions excitations of transverse modes are the prerequisite for energy exchange and thermalzation. At very low temperatures excitations of transverse modes are exponentially suppressed, thermalization by two body collisions stops and the system should become integrable. In quantum mechanics virtual excitations of higher radial modes are possible. These virtually excited radial modes give rise to effective three-body velocity-changing collisions which lead to thermalization. We show that these three-body elastic interactions are suppressed by pairwise quantum correlations when approaching the strongly correlated regime. If the relative momentum $k$ is small compared to the two-body coupling constant $c$ the three-particle scattering state is suppressed by a factor of $(k/c)^{12}$, which is proportional to $γ^{12}$, that is to the square of the three-body correlation function at zero distance in the limit of the Lieb-Liniger parameter $γ\gg 1$. This demonstrates that in one dimensional quantum systems it is not the freeze-out of two body collisions but the strong quantum correlations which ensures absence of thermalization on experimentally relevant time scales.

cond-mat.quant-gas↗

arXiv2010

Fluctuations and stochastic processes in one-dimensional many-body quantum systems

We study the fluctuation properties of a one-dimensional many-body quantum system composed of interacting bosons, and investigate the regimes where quantum noise or, respectively, thermal excitations are dominant. For the latter we develop a semiclassical description of the fluctuation properties based on the Ornstein-Uhlenbeck stochastic process. As an illustration, we analyze the phase correlation functions and the full statistical distributions of the interference between two one-dimensional systems, either independent or tunnel-coupled and compare with the Luttinger-liquid theory.

cond-mat.quant-gas↗

arXiv2010

Two-point density correlations of quasicondensates in free expansion

We measure the two-point density correlation function of freely expanding quasicondensates in the weakly interacting quasi-one-dimensional (1D) regime. While initially suppressed in the trap, density fluctuations emerge gradually during expansion as a result of initial phase fluctuations present in the trapped quasicondensate. Asymptotically, they are governed by the thermal coherence length of the system. Our measurements take place in an intermediate regime where density correlations are related to near-field diffraction effects and anomalous correlations play an important role. Comparison with a recent theoretical approach described by Imambekov et al. yields good agreement with our experimental results and shows that density correlations can be used for thermometry of quasicondensates.

cond-mat.quant-gas↗

arXiv2009

Density ripples in expanding low-dimensional gases as a probe of correlations

We investigate theoretically the evolution of the two-point density correlation function of a low-dimensional ultracold Bose gas after release from a tight transverse confinement. In the course of expansion thermal and quantum fluctuations present in the trapped systems transform into density fluctuations. For the case of free ballistic expansion relevant to current experiments, we present simple analytical relations between the spectrum of ``density ripples'' and the correlation functions of the original confined systems. We analyze several physical regimes, including weakly and strongly interacting one-dimensional (1D) Bose gases and two-dimensional (2D) Bose gases below the Berezinskii-Kosterlitz-Thouless (BKT) transition. For weakly interacting 1D Bose gases, we obtain an explicit analytical expression for the spectrum of density ripples which can be used for thermometry. For 2D Bose gases below the BKT transition, we show that for sufficiently long expansion times the spectrum of the density ripples has a self-similar shape controlled only by the exponent of the first-order correlation function. This exponent can be extracted by analyzing the evolution of the spectrum of density ripples as a function of the expansion time.

cond-mat.quant-gas↗

arXiv2009

Restoring integrability in one-dimensional quantum gases by two-particle correlations

We show that thermalization and the breakdown of integrability in the one dimensional Lieb-Liniger model caused by local three-body elastic interactions is suppressed by pairwise quantum correlations when approaching the strongly correlated regime. If the relative momentum $k$ is small compared to the two-body coupling constant $c$ the three-particle scattering state is suppressed by a factor of $(k/c)^{12}$. This demonstrates that in one dimensional quantum systems it is not the freeze-out of two body collisions but the strong quantum correlations which ensures integrability.

quant-ph↗

arXiv2008

Creation of macroscopic quantum superposition states by a measurement

We propose a novel protocol for the creation of macroscopic quantum superposition (MQS) states based on a measurement of a non-monotonous function of a quantum collective variable. The main advantage of this protocol is that it does not require switching on and off nonlinear interactions in the system. We predict this protocol to allow the creation of multiatom MQS by measuring the number of atoms coherently outcoupled from a two-component (spinor) Bose-Einstein condensate.

quant-ph↗

arXiv2008

Tunneling electro-conductance of atomic Bose condensates

We consider interaction of an electron with a Bose condensate of atoms having electron affinity. Though states of the electron attached to atoms form a continuous band, tunneling through this band is strongly suppressed by quantum fluctuations of the condensate density. We adapt standard field theory methods originally developed for description of a particle propagating trough a disordered potential and present an exactly soluble analytical model of the process. In contrast with the standard description, we take into account inelastic processes associated with quantum transitions in the condensate. Possibilities of the experimental observation of the phenomenon are discussed.

cond-mat.mes-hall↗

arXiv2008

Dephasing in two decoupled one-dimensional Bose-Einstein condensates and the subexponential decay of the interwell coherence

We provide a simple physical picture of the loss of coherence between two coherently split one-dimensional Bose-Einstein condensates. The source of the dephasing is identified with nonlinear corrections to the elementary excitation energies in either of the two independent condensates. We retrieve the result by Burkov, Lukin and Demler [Phys. Rev. Lett. 98, 200404 (2007)] on the subexponential decay of the cocherence for the large time, however, the scaling of the characteristic decoherence time differs.

cond-mat.stat-mech↗

arXiv2008

Breakdown of integrability in a quasi-one-dimensional ultracold bosonic gas

We demonstrate that virtual excitations of higher radial modes in an atomic Bose gas in a tightly confining waveguide result in effective three-body collisions that violate integrability in this quasi-one-dimensional quantum system and give rise to thermalization. The estimated thermalization rates are consistent with recent experimental results in quasi-1D dynamics of ultracold atoms.

cond-mat.other↗

arXiv2007

Multiatom cooperative emission following single-photon absorption: Dicke-state dynamics

We investigate conditions under which multiatom absorption of a single photon leads to cooperative decay. Our analysis reveals the symmetry properties of the multiatom Dicke states underlying the cooperative decay dynamics and their spatio-temporal manifestations, particularly, the forward-directed spontaneous emission investigated by Scully et al.

quant-ph↗

arXiv2006

Modification of scattering lengths via magnetic dipole-dipole interactions

We propose a new mechanism for tuning an atomic s-wave scattering length. The effect is caused by virtual transitions between different Zeeman sublevels via magnetic dipole-dipole interactions. These transitions give rise to an effective potential, which, in contrast to standard magnetic interactions, has an isotropic component and thus affects s-wave collisions. Our numerical analysis shows that for chromium-50 the scattering length can be modified up to 15 %.

cond-mat.stat-mech↗

arXiv2005

Multipartite transmission of quantum solitons

We analyze the preparation (launching) of a 1D-propagating multipartite quantum soliton, its scattering and disintegration by an external potential. The regimes of suppressed disintegration and atom-number-dependent transmission are identified.

cond-mat.other↗

arXiv2005

Entanglement and teleportation of macroscopic continuous variables by superconducting devices

A current-biased low-temperature superconducting Josephson junction (JJ) is dynamically describable by the quantized motion of a fictitious particle in a "washboard" potential. The long coherence time of tightly-bound states in the washboard potential of a JJ has prompted the effort to couple JJs and operate them as entangled qubits, capable of forming building blocks of a scalable quantum computer. Here we consider a hitherto unexplored quantum aspect of coupled JJs: the ability to produce Einstein-Podolsky-Rosen (EPR) entanglement of their continuous variables, namely, their magnetic fluxes and induced charges. Such entanglement, apart from its conceptual novelty, is the prerequisite for a far-reaching goal: teleportation of the flux and charge variables between JJs, implementing the transfer of an unknown quantum state along a network of such devices.

quant-ph↗