Quantum Coherence Resonance

TL;DR

This paper demonstrates that quantum coherence resonance, where noise enhances regular oscillations, occurs in quantum dissipative systems like the quantum van der Pol oscillator, with novel effects observed under strong quantum fluctuations.

Contribution

It reveals the existence of quantum coherence resonance in quantum systems and uncovers a second resonance peak driven by strong quantum effects beyond semiclassical explanations.

Findings

Quantum coherence resonance occurs in quantum van der Pol systems.

Resonance persists under moderate quantum fluctuations.

A second resonance peak appears at strong quantum fluctuations.

Abstract

It is shown that coherence resonance, a phenomenon in which regularity of noise-induced oscillations in nonlinear excitable systems is maximized at a certain optimal noise intensity, can be observed in quantum dissipative systems. We analyze a quantum van der Pol system subjected to squeezing, which exhibits bistable excitability in the classical limit, by numerical simulations of the quantum master equation. We first demonstrate that quantum coherence resonance occurs in the semiclassical regime, namely, the regularity of the system's oscillatory response is maximized at an optimal intensity of quantum fluctuations, and interpret this phenomenon by analogy with classical noisy excitable systems using semiclassical stochastic differential equations. This resonance persists under moderately strong quantum fluctuations for which the semiclassical description is invalid. Moreover, we investigate even stronger quantum regimes and demonstrate that the regularity of the system's response can exhibit the second peak as the intensity of the quantum fluctuations is further increased. We show that this second peak of resonance is a strong quantum effect that cannot be interpreted by a semiclassical picture, in which only a few energy states participate in the system dynamics.