Non-equilibrium dynamics of isolated quantum systems

Abstract

Abstract. The non-equilibrium dynamics of isolated quantum systems represent a theoretical and experimental challenge raising many fundamental questions with applications to different fields of modern physics. In these proceedings, we briefly review some of the recent findings on the subject, with particular emphasis to the existence of stationary expectation values of local observables and to their statistical mechanics description. It turns out that the appropriate statistical ensemble describing these asymptotic values depends on whether the Hamiltonian governing the time evolution is integrable or not.

Ballistic front dynamics after joining two semi-infinite quantum Ising chains

“…In fact, significant experimental advances have made it possible to finely control trapped ultra-cold atomic gases (see, for instance, Refs. [1][2][3][4][5]). These systems are so weakly coupled with the surrounding environment that they allow the observation of a unitary non-equilibrium time evolution, with the consequent remarkable phenomena which cannot be observed in standard condensed matter systems due to decoherence and dissipative transport.…”

Quantum dynamical response of ultracold few-boson ensembles in finite optical lattices to multiple interaction quenches

“…Here, the most frequently considered setting is a quantum quench (see Refs. [9][10][11] and references therein), where one explores the quantum evolution after a sudden change of an intrinsic system parameter such as the interaction strength [12][13][14][15]. A complicating feature of the non-equilibrium dynamics is the presence of interactions at a level that often precludes the use of a perturbative analysis and/or mean-field (MF) approximation.…”

Relaxation to a Phase-Locked Equilibrium State in a One-Dimensional Bosonic Josephson Junction

“…All quantum evolution is in principle unitary, and thus isolated quantum systems should never relax to a steady state. However, both theoretical and experimental works [1][2][3][4] show that non-integrable systems reach a relaxed state resembling a Gibbs ensemble [5,6]. In contrast, integrable systems generally relax to pre-thermal steady states, for which a description by a generalized Gibbs ensemble reflects the conserved quantities in the system.…”

“…We also check the influence of the tunnel coupling strength between J/h = 2(1) Hz and J/h = 32(3) Hz (fit result). The initial state is characterized by N = 3500(500) atoms, n 0 = −0.004 (13), φ 0 = −1.93(35) rad, C 0 = 0.53 (7) and R 0 = 0.94 (3). The fit results for the plasma frequency ω are displayed in the inset of Fig.…”

“…The barrier height is kept identical and the change of atom number has a negligible impact on the tunnel coupling which remains J/h = 7(2) Hz. The prepared phase is φ 0 = −1.48(98) rad, associated to a contrast C 0 = 0.55 (7) and a phasor R 0 = 0.81 (3). The typical initial imbalance for the largest atom number is n 0 = 0.006(47).…”