Quantum-correlated photons generated by nonlocal electron transport

TL;DR

This paper investigates how a double quantum dot device can generate quantum correlations and entanglement between two separated photon cavities through coherent single-electron transport, using advanced Green's function calculations.

Contribution

It introduces a novel theoretical analysis of entanglement generation in a double quantum dot system coupled to photon cavities, employing a diagrammatic perturbative approach.

Findings

Entanglement is demonstrated when dot energy levels are nearly degenerate.

Violation of the Cauchy-Schwarz inequality indicates quantum correlations.

Large detunings or single-dot setups do not produce entanglement.

Abstract

Since the realization of high-quality microwave cavities coupled to quantum dots, one can envisage the possibility to investigate the coherent interaction of light and matter in semiconductor quantum devices. Here we study a parallel double quantum dot device operating as single-electron splitter interferometer, with each dot coupled to a local photon cavity. We explore how quantum correlation and entanglement between the two separated cavities are generated by the coherent transport of a single electron passing simultaneously through the two different dots. We calculate the covariance of the cavity occupations by use of a diagrammatic perturbative expansion based on Keldysh Green's functions to the fourth order in the dot-cavity interaction strength, taking into account vertex diagrams. In this way, we demonstrate the creation of entanglement by showing that the classical Cauchy-Schwarz inequality is violated if the energy levels of the two dots are almost degenerate. For large level detunings or a single dot coupled to two cavities, we show that the inequality is not violated.