Quantum pure noise-induced transitions: A truly nonclassical limit cycle sensitive to number parity

TL;DR

This paper demonstrates a nonclassical, noise-induced quantum limit cycle in an open quantum system, characterized by Wigner negativity and number-parity sensitivity, highlighting fundamental differences between quantum and classical noise effects.

Contribution

It introduces a minimal quantum model showing pure noise-induced transitions to a nonclassical limit cycle, distinct from classical counterparts, with analytical tractability and unique quantum traits.

Findings

Quantum limit cycle exhibits Wigner negativity.

Limit cycle is sensitive to number parity.

System transitions to a nonclassical state due to noise.

Abstract

It is universally accepted that noise may bring order to complex nonequilibrium systems. Most strikingly, entirely new states not seen in the noiseless system can be induced purely by including multiplicative noise -- an effect known as pure noise-induced transitions. It was first observed in superfluids in the 1980s. Recent results in complex nonequilibrium systems have also shown how new collective states emerge from such pure noise-induced transitions, such as the foraging behavior of insect colonies, and schooling in fish. Here we report such effects of noise in a quantum-mechanical system without a classical limit. We use a minimal model of a nonlinearly damped oscillator in a fluctuating environment that is analytically tractable, and whose microscopic physics can be understood. When multiplicative environmental noise is included, the system is seen to transition to a limit-cycle state. The noise-induced quantum limit cycle also exhibits other genuinely nonclassical traits, such as Wigner negativity and number-parity sensitive circulation in phase space. Such quantum limit cycles are also conservative. These properties are in stark contrast to those of a widely used limit cycle in the literature, which is dissipative and loses all Wigner negativity. Our results establish the existence of a pure noise-induced transition that is nonclassical and unique to open quantum systems. They illustrate a fundamental difference between quantum and classical noise.