Quantum fluctuation effects on the quench dynamics of thermal quasicondensates

Świsłocki, Tomasz; Deuar, P.

doi:10.1088/0953-4075/49/14/145303

Cited by 12 publications

(9 citation statements)

References 91 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We now briefly review how the dynamics can be tackled with the gauge-P distribution, by stochastically sampling the many-body state, rather than representing it exactly. For an in-depth explanation we refer to the extensive literature on the positive-P [2][3][4][5]7,10,12,13,30,32,[67][68][69][70][71] and gauge-P methods [8,9,11,21,23,31,34,[36][37][38][72][73][74].…”

Section: Gauge-p and Positive-p Descriptionsmentioning

confidence: 99%

Quantum dynamics of long-range interacting systems using the positive- P and gauge- P representations

et al. 2017

View full text Add to dashboard Cite

We provide the necessary framework for carrying out stochastic positive-P and gauge-P simulations of bosonic systems with long-range interactions. In these approaches, the quantum evolution is sampled by trajectories in phase space, allowing calculation of correlations without truncation of the Hilbert space or other approximations to the quantum state. The main drawback is that the simulation time is limited by noise arising from interactions. We show that the long-range character of these interactions does not further increase the limitations of these methods, in contrast to the situation for alternatives such as the density matrix renormalization group. Furthermore, stochastic gauge techniques can also successfully extend simulation times in the long-range-interaction case, by making using of parameters that affect the noise properties of trajectories, without affecting physical observables. We derive essential results that significantly aid the use of these methods: estimates of the available simulation time, optimized stochastic gauges, a general form of the characteristic stochastic variance, and adaptations for very large systems. Testing the performance of particular drift and diffusion gauges for nonlocal interactions, we find that, for small to medium systems, drift gauges are beneficial, whereas for sufficiently large systems, it is optimal to use only a diffusion gauge. The methods are illustrated with direct numerical simulations of interaction quenches in extended Bose-Hubbard lattice systems and the excitation of Rydberg states in a Bose-Einstein condensate, also without the need for the typical frozen gas approximation. We demonstrate that gauges can indeed lengthen the useful simulation time.

show abstract

Section: Gauge-p and Positive-p Descriptionsmentioning

confidence: 99%

Quantum dynamics of long-range interacting systems using the positive- P and gauge- P representations

et al. 2017

View full text Add to dashboard Cite

show abstract

“…It has been used for solving and simulating a multitude of problems in various physical fields: e.g. quantum optics [21,28,30,32,52,54,84,91,110], ultracold atoms [22,39,40,49,74,82,94,95,101,102,108,125,131,134,144], fermionic systems [6,7,27,29], spin systems [11,106,107], nuclear physics [137], dissipative systems in condensed matter [26,45,143], or cosmology [111]. The vast majority of such calculations so far have considered only equal time correlations and observables.…”

Section: Introductionmentioning

confidence: 99%

Multi-time correlations in the positive-P, Q, and doubled phase-space representations

Deuar

2021

Quantum

Self Cite

View full text Add to dashboard Cite

A number of physically intuitive results for the calculation of multi-time correlations in phase-space representations of quantum mechanics are obtained. They relate time-dependent stochastic samples to multi-time observables, and rely on the presence of derivative-free operator identities. In particular, expressions for time-ordered normal-ordered observables in the positive-P distribution are derived which replace Heisenberg operators with the bare time-dependent stochastic variables, confirming extension of earlier such results for the Glauber-Sudarshan P. Analogous expressions are found for the anti-normal-ordered case of the doubled phase-space Q representation, along with conversion rules among doubled phase-space s-ordered representations. The latter are then shown to be readily exploited to further calculate anti-normal and mixed-ordered multi-time observables in the positive-P, Wigner, and doubled-Wigner representations. Which mixed-order observables are amenable and which are not is indicated, and explicit tallies are given up to 4th order. Overall, the theory of quantum multi-time observables in phase-space representations is extended, allowing non-perturbative treatment of many cases. The accuracy, usability, and scalability of the results to large systems is demonstrated using stochastic simulations of the unconventional photon blockade system and a related Bose-Hubbard chain. In addition, a robust but simple algorithm for integration of stochastic equations for phase-space samples is provided.

show abstract

“…The cooling simulations start with thermal clouds of atoms in a 3d harmonic trap polarized in a single spin state, which is for for chromium and for sodium. Therefore a single-component stochastic Gross-Pitaevskii equation (SGPE) 28 , 36 provides a convenient route to directly obtain thermal ensembles at a chosen temperature and particle number N 35 , 37 . One evolves the complex field in technical time according to the equation until a stable fluctuation of observables in time around a mean is obtained—i.e.…”

Section: Modelmentioning

confidence: 99%

Spin distillation cooling of ultracold Bose gases

Świsłocki

Gajda

Brewczyk

et al. 2021

Sci Rep

Self Cite

View full text Add to dashboard Cite

We study the spin distillation of spinor gases of bosonic atoms and find two different mechanisms in $${}^{52}$$ 52 Cr and $$^{23}$$ 23 Na atoms, both of which can cool effectively. The first mechanism involves dipolar scattering into initially unoccupied spin states and cools only above a threshold magnetic field. The second proceeds via equilibrium relaxation of the thermal cloud into empty spin states, reducing its proportion in the initial component. It cools only below a threshold magnetic field. The technique was initially demonstrated experimentally for a chromium dipolar gas (Naylor et al. in Phys Rev Lett 115:243002, 2015), whereas here we develop the concept further and provide an in-depth understanding of the required physics and limitations involved. Through numerical simulations, we reveal the mechanisms involved and demonstrate that the spin distillation cycle can be repeated several times, each time resulting in a significant additional reduction of the thermal atom fraction. Threshold values of magnetic field and predictions for the achievable temperature are also identified.

show abstract

Quantum fluctuation effects on the quench dynamics of thermal quasicondensates

Cited by 12 publications

References 91 publications

Quantum dynamics of long-range interacting systems using the positive- P and gauge- P representations

Quantum dynamics of long-range interacting systems using the positive- P and gauge- P representations

Multi-time correlations in the positive-P, Q, and doubled phase-space representations

Spin distillation cooling of ultracold Bose gases

Contact Info

Product

Resources

About