Photon cross-correlations emitted by a Josephson junction in two microwave cavities

TL;DR

This paper investigates the non-classical photon correlations emitted by a voltage-biased Josephson junction coupled to two microwave cavities, revealing violations of classical inequalities and analyzing the dynamics of the emitted radiation.

Contribution

It introduces a density and input-output approach to analyze photon correlations in a Josephson junction-cavity system, demonstrating non-classical emission and detailed correlation dynamics.

Findings

Emitted radiation violates Cauchy-Schwarz inequalities, indicating non-classicality.

Photon correlation linewidth narrows as emission rate approaches the threshold.

Non-classical correlations persist for finite and infinite detector bandwidths.

Abstract

We study a voltage biased Josephson junction coupled to two resonators of incommensurate frequencies. Using a density approach to analyze the cavity fields and an input-output description to analyze the emitted photonic fluxes and their correlation functions, we have shown, both for infinite and finite bandwidth detectors, that the emitted radiation is non-classical in the sense that the correlators violates Cauchy-Schwarz inequalities. We have also studied the time dependence of the photonic correlations and showed that their line-width becomes narrower with the increase of the emission rate approaching from below the threshold limit.