Non-equilibrium correlations and entanglement in a semiconductor hybrid circuit-QED system

TL;DR

This paper theoretically investigates a hybrid circuit-QED system with two charge qubits in a microwave resonator, revealing photon-mediated entanglement and non-equilibrium correlations through electron transport analysis.

Contribution

It introduces a model of two spatially separated charge qubits coupled via a common resonator, demonstrating steady-state entanglement and transport signatures of qubit interactions.

Findings

Charge qubits become entangled in steady state.

Electron transport shows signatures of photon-mediated interactions.

Finite shot noise cross-correlations indicate nontrivial entanglement.

Abstract

We present a theoretical study of a hybrid circuit-QED system composed of two semiconducting charge-qubits confined in a microwave resonator. The qubits are defined in terms of the charge states of two spatially separated double quantum dots (DQDs) which are coupled to the same photon mode in the microwave resonator. We analyze a transport setup where each DQD is attached to electronic reservoirs and biased out-of-equilibrium by a large voltage, and study how electron transport across each DQD is modified by the coupling to the common resonator. In particular, we show that the inelastic current through each DQD reflects an indirect qubit-qubit interaction mediated by off-resonant photons in the microwave resonator. As a result of this interaction, both charge qubits stay entangled in the steady (dissipative) state. Finite shot noise cross-correlations between currents across distant DQDs are another manifestation of this nontrivial steady-state entanglement.