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Entropy 2018, 20(4), 226; https://doi.org/10.3390/e20040226

Enhancing Metastability by Dissipation and Driving in an Asymmetric Bistable Quantum System

1
Dipartimento di Fisica e Chimica, Group of Interdisciplinary Theoretical Physics, Università di Palermo and CNISM, Unità di Palermo, Viale delle Scienze, Edificio 18, I-90128 Palermo, Italy
2
Istituto Nazionale di Fisica Nucleare, Sezione di Catania, I-95100 Catania, Italy
3
Radiophysics Department, Lobachevsky State University of Nizhni Novgorod, 603000 Nizhni Novgorod, Russia
4
Istituto di Biomedicina ed Immunologia Molecolare (IBIM) “Alberto Monroy”, CNR, Via Ugo La Malfa 153, I-90146 Palermo, Italy
*
Author to whom correspondence should be addressed.
Received: 7 November 2017 / Revised: 1 March 2018 / Accepted: 23 March 2018 / Published: 26 March 2018
(This article belongs to the Special Issue Entropy and Information in the Foundation of Quantum Physics)
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Abstract

The stabilizing effect of quantum fluctuations on the escape process and the relaxation dynamics from a quantum metastable state are investigated. Specifically, the quantum dynamics of a multilevel bistable system coupled to a bosonic Ohmic thermal bath in strong dissipation regime is analyzed. The study is performed by a non-perturbative method based on the real-time path integral approach of the Feynman-Vernon influence functional. We consider a strongly asymmetric double well potential with and without a monochromatic external driving, and with an out-of-equilibrium initial condition. In the absence of driving we observe a nonmonotonic behavior of the escape time from the metastable region, as a function both of the system-bath coupling coefficient and the temperature. This indicates a stabilizing effect of the quantum fluctuations. In the presence of driving our findings indicate that, as the coupling coefficient γ increases, the escape time, initially controlled by the external driving, shows resonant peaks and dips, becoming frequency-independent for higher γ values. Moreover, the escape time from the metastable state displays a nonmonotonic behavior as a function of the temperature, the frequency of the driving, and the thermal-bath coupling, which indicates the presence of a quantum noise enhanced stability phenomenon. Finally, we investigate the role of different spectral densities, both in sub-Ohmic and super-Ohmic dissipation regime and for different cutoff frequencies, on the relaxation dynamics from the quantum metastable state. The results obtained indicate that, in the crossover dynamical regime characterized by damped intrawell oscillations and incoherent tunneling, the spectral properties of the thermal bath influence non-trivially the short time behavior and the time scales of the relaxation dynamics from the metastable state. View Full-Text
Keywords: Caldeira-Leggett model; metastable potential; discrete variable representation; noise enhanced stability; resonant activation; tunneling; quantum Zeno dynamics; quantum systems with finite Hilbert space; functional analytical methods; open systems; quantum statistical methods Caldeira-Leggett model; metastable potential; discrete variable representation; noise enhanced stability; resonant activation; tunneling; quantum Zeno dynamics; quantum systems with finite Hilbert space; functional analytical methods; open systems; quantum statistical methods
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Spagnolo, B.; Carollo, A.; Valenti, D. Enhancing Metastability by Dissipation and Driving in an Asymmetric Bistable Quantum System. Entropy 2018, 20, 226.

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