Scaling properties of work fluctuations after quenches near quantum transitions

2018

Phys. Rev. A

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We study the decoherence properties of a two-level (qubit) system homogeneously coupled to an environmental many-body system at a quantum transition, considering both continuous and first-order quantum transitions. In particular, we consider a d-dimensional quantum Ising model as environment system. We study the dynamic of the qubit decoherence along the global quantum evolution starting from pure states of the qubit and the ground state of the environment system. This issue is discussed within dynamic finite-size scaling frameworks. We analyze the dynamic finite-size scaling of appropriate qubit-decoherence functions. At continuous quantum transitions, they develop power laws of the size of the environment system, with a substantial enhancement of the growth rate of the qubit decoherence with respect to the case the environment system is in normal noncritical conditions. The enhancement of the qubit decoherence growth rate appears much larger at first-order quantum transitions, leading to exponential laws when increasing the size of the environment system.

Section: The Decoherence Dynamics With a Critical Environmental supporting

confidence: 54%

Decoherence dynamics of qubits coupled to systems at quantum transitions

2018

Phys. Rev. A

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“…We also notice that the FSS frameworks have been extended to the off-equilibrium quantum dynamics, focusing on both time-dependent perturbations [49] and sudden quenches [50]. By defining scaling variables that are consistent with the procedure considered in this paper, and including further ones associated with the time and the dynamic variables, dynamic FSS behaviors have been shown to emerge even in other contexts, as for the decoherence properties [67] and the statistics of the work [68].…”

Section: Discussionmentioning

confidence: 93%

Ground-state fidelity at first-order quantum transitions

Rossini

2018

Phys. Rev. E

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We analyze the scaling behavior of the fidelity, and the corresponding susceptibility, emerging in finite-size many-body systems whenever a given control parameter λ is varied across a quantum phase transition. For this purpose we consider a finite-size scaling (FSS) framework. Our working hypothesis is based on a scaling assumption of the fidelity in terms of the FSS variables associated to λ and to its variation δλ. This framework entails the FSS predictions for continuous transitions, and meanwhile enables to extend them to first-order transitions, where the FSS becomes qualitatively different. The latter is supported by analytical and numerical analyses of the quantum Ising chain along its first-order quantum transition line, driven by an external longitudinal field. arXiv:1807.01674v2 [cond-mat.stat-mech] 30 Nov 2018

“…In this section we focus on the statistics of the work done on the Fermi gas, when this is driven out of equilibrium by suddenly switching the control parameter associated with the external potential. Several issues related to the definition and computation of the work statistics in quantum systems have been already discussed in a variety of physical implementations [30,31], including spin chains [32][33][34][35][36][37][38][39][40], fermionic and bosonic systems [40][41][42][43][44].…”

Section: A Quantum Work Distributionmentioning

confidence: 99%

Particle-number scaling of the quantum work statistics and Loschmidt echo in Fermi gases with time-dependent traps

2019

Phys. Rev. A

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We investigate the particle-number dependence of some features of the out-of-equilibrium dynamics of d-dimensional Fermi gases in the dilute regime. We consider protocols entailing the variation of the external potential which confines the particles within a limited spatial region, in particular sudden changes of the trap size. In order to characterize the dynamic behavior of the Fermi gas, we consider various global quantities such as the ground-state fidelity for different trap sizes, the quantum work statistics associated with the protocol considered, and the Loschmidt echo measuring the overlap of the out-of-equilibrium quantum states with the initial ground state. Their asymptotic particle-number dependences show power laws for noninteracting Fermi gases. We also discuss the effects of short-ranged interactions to the power laws of the average work and its square fluctuations, within the Hubbard model and its continuum limit, arguing that they do not generally change the particle-number power laws of the free Fermi gases, in any spatial dimensions.