Time-resolved statistics of nonclassical light in Josephson photonics

TL;DR

This paper investigates the time-dependent statistics of nonclassical light emitted from a Josephson photonics setup, revealing the transition from coherent to single-photon emission and analyzing the effects of nonlinearity on light states.

Contribution

It provides analytical and numerical analysis of photon statistics in Josephson photonics, highlighting nonclassical light states generated by tunneling Cooper pairs under weak and strong driving.

Findings

Demonstrates crossover from coherent to single-photon emission

Shows nonlinearity induces diverse nonclassical light states

Analyzes relations between $g^{(2)}( au)$ and $w( au)$

Abstract

The interplay of the tunneling transfer of charges and the emission and absorption of light can be investigated in a setup, where a voltage-biased Josephson junction is connected in series with a microwave cavity. We focus here on the emission processes of photons and analyze the underlying time-dependent statistics using the second-order correlation function $g^{(2)}(\tau)$ and the waiting-time distribution $w(\tau)$. Both observables highlight the crossover from a coherent light source to a single-photon source. Due to the nonlinearity of the Josephson junction, tunneling Cooper pairs can create a great variety of non-classical states of light even at weak driving. Analytical results for the weak driving as well as the classical regime are complemented by a numerical treatment for the full nonlinear case. We also address the question of possible relations between $g^{(2)}(\tau)$ and $w(\tau)$ as well as the specific information which is provided by each of them.