Proposal for generating and detecting multi-qubit GHZ states in circuit QED

TL;DR

This paper proposes methods for generating and detecting multi-qubit GHZ states in circuit QED, demonstrating high-fidelity entanglement and Bell inequality violation using dispersive readout and nonlinear filtering techniques.

Contribution

It introduces a probabilistic approach for creating GHZ states via joint dispersive readout and shows how to verify entanglement without full detector tomography.

Findings

High-fidelity GHZ states can be probabilistically produced.

Bell-Mermin operator exceeds 2 under realistic conditions.

Dispersive readout can demonstrate violation of Mermin bound.

Abstract

We propose methods for the preparation and entanglement detection of multi-qubit GHZ states in circuit quantum electrodynamics. Using quantum trajectory simulations appropriate for the situation of a weak continuous measurement, we show that the joint dispersive readout of several qubits can be utilized for the probabilistic production of high-fidelity GHZ states. When employing a nonlinear filter on the recorded homodyne signal, the selected states are found to exhibit values of the Bell-Mermin operator exceeding 2 under realistic conditions. We discuss the potential of the dispersive readout to demonstrate a violation of the Mermin bound, and present a measurement scheme avoiding the necessity for full detector tomography.