Universal quantum fluctuations of a cavity mode driven by a Josephson junction

TL;DR

This paper investigates the quantum behavior of a superconducting cavity driven by a Josephson junction, revealing universal quantum fluctuations and significant squeezing at resonances, with potential implications for quantum technologies.

Contribution

It introduces a detailed analysis of quantum fluctuations and squeezing in a cavity-Josephson system, identifying regimes with universal fluctuation values.

Findings

Resonances cause substantial squeezing of cavity quantum fluctuations.

Universal values of fluctuations are observed in certain regimes.

Quantum dynamics are strongly influenced by the Josephson junction coupling.

Abstract

We analyze the quantum dynamics of a superconducting cavity coupled to a voltage biased Josephson junction. The cavity is strongly excited at resonances where the voltage energy lost by a Cooper pair traversing the circuit is a multiple of the cavity photon energy. We find that the resonances are accompanied by substantial squeezing of the quantum fluctuations of the cavity over a broad range of parameters and are able to identify regimes where the fluctuations in the system take on universal values.