Entangled quantum currents in distant mesoscopic Josephson junctions

TL;DR

This paper investigates how entangled microwave photons influence the quantum tunneling currents in two distant mesoscopic Josephson junctions, revealing correlations that depend on the quantum state of the microwaves.

Contribution

It introduces a method to analyze the effect of quantum entanglement of microwaves on Josephson currents in separated rings, highlighting the role of quantum correlations.

Findings

Quantum entanglement affects Josephson current correlations.

Differences observed between classical and quantum microwave states.

Results demonstrated for number and coherent states.

Abstract

Two mesoscopic SQUID rings which are far from each other, are considered. A source of two-mode nonclassical microwaves irradiates the two rings with correlated photons. The Josephson currents are in this case quantum mechanical operators, and their expectation values with respect to the density matrix of the microwaves, yield the experimentally observed currents. Classically correlated (separable) and quantum mechanically correlated (entangled) microwaves are considered, and their effect on the Josephson currents is quantified. Results for two different examples that involve microwaves in number states and coherent states are derived. It is shown that the quantum statistics of the tunnelling electron pairs through the Josephson junctions in the two rings, are correlated.