Quantum Synchronization in quadratically coupled quantum van der Pol oscillators

TL;DR

This paper explores quantum synchronization in coupled anharmonic van der Pol oscillators, revealing nonclassical effects like phonon blockade, multiple resonance locking, and phonon antibunching, with potential experimental implementations.

Contribution

It introduces nonlinear anharmonic interactions in coupled van der Pol oscillators to demonstrate high-order quantum synchronization and nonclassical phenomena not observed in classical systems.

Findings

Demonstrates phonon blockade due to anharmonicity in phase locking

Shows multiple resonance phase locking from nonlinear interactions

Identifies phonon antibunching and simultaneous bunching-antibunching effects

Abstract

We implement nonlinear anharmonic interaction in the coupled van der Pol oscillators to investigate the quantum synchronization behaviour of the systems. We study the quantum synchronization in two oscillator models, coupled quantum van der Pol oscillators and anharmonic self-oscillators. We demonstrate that the considered systems exhibit a high-order synchronization through coupling in both classical and quantum domains. We show that due to the anharmonicity of the nonlinear interaction between the oscillators the system exhibits phonon blockade in the phase locking regime which is a pure nonclassical effect and has not been observed in the classical domain. We also demonstrate that for coupled anharmonic oscillators the system shows a multiple resonance phase locking behaviour due to nonlinear interaction. We point out that the synchronization blockade arises due to strong anticorrelation between the oscillators which leads to phonon antibunching in the same parametric regime. In the anharmonic oscillator case we illustrate the simultaneous occurrence of bunching and antibunching effects as a consequence of simultaneous negative and positive correlation between the anharmonic oscillators. We examine the aforementioned characteristic features in the frequency entrainment of the oscillators using power spectrum where one can observe normal mode splitting and Mollow triplet in the strong coupling regime. Finally, we propose a possible experimental realization for the considered system in trapped ion and optomechanical setting.