# Quantum Dynamics of a Josephson Junction-Driven Cavity Mode System in the Presence of Voltage Bias Noise

## TL;DR

This paper analyzes how voltage bias noise affects photon statistics and squeezing in a Josephson junction-driven microwave cavity, revealing that noise degrades squeezing especially at high photon numbers and depends on the system's steady state regime.

## Contribution

It provides a semiclassical analysis of bias noise effects on photon number and squeezing in a JJ-cavity system, highlighting the dependence on steady state regimes.

## Key findings

- Bias noise degrades amplitude squeezing in the cavity.
- Sensitivity to bias noise varies with the classical steady state regime.
- Impact of noise is most significant at large photon numbers.

## Abstract

We give a semiclassical analysis of the average photon number as well as photon number variance (Fano factor $F$) for a Josephson-junction (JJ) embedded microwave cavity system, where the JJ is subject to a fluctuating (i.e. noisy) bias voltage with finite dc average. Through the ac Josephson effect, the dc voltage bias drives the effectively nonlinear microwave cavity mode into an amplitude squeezed state ($F<1$), as has been established previously [A. D. Armour, et al., Phys. Rev. Lett. 111, 247001 (2013)], but bias noise acts to degrade this squeezing. We find that the sensitivity of the Fano factor to bias voltage noise depends qualitatively on which stable fixed point regime the system is in for the corresponding classical nonlinear steady state dynamics. Furthermore, we show that the impact of voltage bias noise is most significant when the cavity is excited to states with large average photon number.