Apparent nonlinear damping triggered by quantum fluctuations

TL;DR

This paper demonstrates that quantum fluctuations can induce an apparent nonlinear damping effect in superconducting resonators, which may also occur in other systems with similar nonlinearities, affecting their performance in precision applications.

Contribution

The study reveals that quantum fluctuations combined with nonlinearity can produce a power-dependent damping effect, providing new insights into damping mechanisms in quantum and classical oscillators.

Findings

Quantum fluctuations cause a power-dependent response in superconducting resonators.

The phenomenon resembles nonlinear damping and can be visualized as dephasing in phase space.

The effect is expected to occur in other systems with similar nonlinearities, such as nano-mechanical oscillators.

Abstract

Nonlinear damping, the change in damping rate with the amplitude of oscillations plays an important role in many electrical, mechanical and even biological oscillators. In novel technologies such as carbon nanotubes, graphene membranes or superconducting resonators, the origin of nonlinear damping is sometimes unclear. This presents a problem, as the damping rate is a key figure of merit in the application of these systems to extremely precise sensors or quantum computers. Through measurements of a superconducting resonator, we show that from the interplay of quantum fluctuations and the nonlinearity of a Josephson junction emerges a power-dependence in the resonator response which closely resembles nonlinear damping. The phenomenon can be understood and visualized through the flow of quasi-probability in phase space where it reveals itself as dephasing. Crucially, the effect is not restricted to superconducting circuits: we expect that quantum fluctuations or other sources of noise give rise to apparent nonlinear damping in systems with a similar conservative nonlinearity, such as nano-mechanical oscillators or even macroscopic systems.