Generating and stabilizing the GHZ state in circuit QED: Joint measurement, Zeno effect and feedback

TL;DR

This paper presents a method to generate and stabilize three-qubit GHZ states in circuit QED using joint measurement, the Zeno effect, and feedback, achieving high fidelity with efficient measurement and control.

Contribution

It extends previous two-qubit Bell state stabilization techniques to three-qubit GHZ states with a novel feedback and measurement scheme.

Findings

High-fidelity GHZ state stabilization demonstrated

Effective use of joint homodyne readout and feedback control

Fast recovery from environmental decoherence achieved

Abstract

In solid-state circuit QED system, we extend the previous study of generating and stabilizing two-qubit Bell state [Phys. Rev. A 82, 032335 (2010)], to three-qubit GHZ state. In dispersive regime, we employ the homodyne joint readout for multiple qubits to infer the state for further processing, and in particular use it to stabilize the state directly by means of an alternate-flip-interrupted Zeno (AFIZ) scheme. Moreover, the state-of-the-art feedback action based on the filtered current enables not only a deterministic generation of the pre-GHZ state in the initial stage, but also a fast recovery from the environment-caused degradation in the later stabilization process. We show that the proposed scheme can maintain the state with high fidelity if the efficient quantum measurement and rapid single-qubit rotations are available.