Metastable quantum entrainment

TL;DR

This paper investigates quantum synchronization in driven-dissipative quantum oscillators, revealing metastability as a key factor in quantum entrainment and its limitations due to fluctuations between metastable phases.

Contribution

It establishes a connection between quantum entrainment and metastability, highlighting a regime with large separation of time scales and metastable states in open quantum systems.

Findings

Identification of a metastable regime with long-lived dynamical modes

Quantum entrainment involves incoherent switching between metastable phases

Fluctuations limit the coherence of quantum synchronization

Abstract

Quantum van der Pol oscillators are driven-dissipative systems displaying quantum synchronization phenomena. When forced by a squeezed drive, the frequency adjusts to half of the forcing displaying multiple preferred phases. Here we analyze the physical origin of this entrained response, establishing a connection with metastability in open quantum systems. We report a dynamical regime characterized by a huge separation of time scales, in which a dynamical mode displays a lifetime that can be orders of magnitude larger than the rest. In this regime, the long-time dynamics is captured by an incoherent process between two metastable states, which correspond to the preferred phases of the synchronized oscillator. In fact, we show that quantum entrainment is here characterized by fluctuations driving an incoherent process between two metastable phases, which ultimately limits its temporal coherence when moving into the quantum regime. Finally, we discuss connections with the phenomena of dissipative phase transitions and transient synchronization in open quantum systems.