Non-classical light from superconducting resonators coupled to voltage-biased Josephson junctions

TL;DR

This paper explores how a voltage-biased Josephson junction coupled to a microwave cavity can generate non-classical light states, with detailed analysis of photon correlations, distributions, and nonlinearity effects.

Contribution

It introduces a theoretical framework for understanding non-classical light emission from superconducting resonators coupled to Josephson junctions, including explicit analytical expressions for photon correlations.

Findings

Generation of non-classical light states including bunched and anti-bunched photons.

Analytical expressions for photon correlation function g^{(2)}(0).

Observation of squeezing and non-Poissonian photon distributions.

Abstract

The interplay of the tunneling transfer of charges and the emission and absorption of light can be investigated in a set-up, where a voltage-biased Josephson junction is placed in series to a microwave cavity. Here, we concentrate on the emission process and show that due to the inherent nonlinearity of the Josephson junction tunneling Cooper-pairs can create a variety of non-classical states of light. Depending on experimental parameters and tuning the device can be described by effective Hamiltonians, indicating specific photon creation mechanisms which lead to strongly bunched or anti-bunched light emission. We derive explicit analytical expressions for the photon correlation function $g^{(2)}(\tau=0)$ for these different processes and investigate their full crossover numerically. Photon distribution functions show squeezing and other interesting non-Poissonian behavior.