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

Abstract

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.

Geometry of quantum phase transitions

“…The simplest example of such a scenario would be the thermal state of a quantum system, and a natural generalisation of the above consideration would be to study phase transitions at finite temperature. As we will discuss the next few sections, the framework that we will introduce provides a way to analyse the even more general scenario of open system phase transitions, in which the properties of non-equilibrium dynamics yields mixed stable states [269][270][271][272][273][274][275][276][277]. To this end, we will need to bring in new tools, and we will start by introducing a mixed state generalisation of the geometric phase, i.e.…”

Neurohybrid Memristive CMOS-Integrated Systems for Biosensors and Neuroprosthetics

“…Noise plays a very significant and constructive role in memristive devices, and only recently new investigations on the positive role of noise have been started (Mikhaylov et al, 2016;Filatov et al, 2019). Nowadays, there are many known examples, where the interplay of non-linearity and fluctuations can change the properties of a stochastic system in a counter-intuitive way, in classical and quantum physics (Fiasconaro et al, 2004;Chichigina et al, 2005Chichigina et al, , 2011Valenti et al, 2008Valenti et al, , 2015Falci et al, 2013;Spagnolo et al, 2015Spagnolo et al, , 2016Spagnolo et al, , 2018a. Furthermore, internal and external noise can play a positive role in the switching dynamics of memristors, as in stochastic resonance phenomenon (La Barbera and Spagnolo, 2002;Valenti et al, 2004;Agudov et al, 2010).…”

Non-Equilibrium Phenomena in Quantum Systems, Criticality and Metastability

“…The scope of this research is to consider the dynamics of a dissipative bistable system, beyond the TLS approximation, in a temperature regime in which the presence of the second energy doublet cannot be neglected [20][21][22][23][24]. To this end, a nonperturbative generalized master equation with approximated kernels can be derived within the Feynman-Vernon influence functional approach [25,26].…”