Photon generation in an electromagnetic cavity with a time-dependent boundary

TL;DR

This paper demonstrates photon generation in a microwave cavity with a time-varying boundary, showing spontaneous oscillations when modulated at twice the resonance frequency, consistent with theoretical predictions and related to the dynamical Casimir effect.

Contribution

First experimental observation of photon generation in a superconducting microwave cavity with a tunable boundary condition in the quantum regime.

Findings

Photon generation observed at twice the resonance frequency

Multiple stable dynamical states identified

Results align with theoretical models of the dynamical Casimir effect

Abstract

We report the observation of photon generation in a microwave cavity with a time-dependent boundary condition. Our system is a microfabricated quarter-wave coplanar waveguide cavity. The electrical length of the cavity is varied using the tunable inductance of a superconducting quantum interference device. It is measured in the quantum regime, where the temperature is significantly less than the resonance frequency (~ 5 GHz). When the length is modulated at approximately twice the static resonance frequency, spontaneous oscillations of the cavity field are observed. Time-resolved measurements of the dynamical state of the cavity show multiple stable states. The behavior is well described by theory. Connections to the dynamical Casimir effect are discussed.