Stabilizing a Bell state of two superconducting qubits by dissipation engineering

TL;DR

This paper presents a dissipation engineering method using microwave drives to prepare and sustain a maximally entangled Bell state of two superconducting qubits with high fidelity and violation of Bell's inequality.

Contribution

It introduces a robust scheme that does not require fine-tuning, enabling long-term preservation of entanglement in superconducting qubits.

Findings

Bell state fidelity above 94% with current coherence times

Long-term violation of Bell's inequality (CHSH > 2.6)

No fine-tuning of parameters needed for effective entanglement preservation

Abstract

We propose a dissipation engineering scheme that prepares and protects a maximally entangled state of a pair of superconducting qubits. This is done by off-resonantly coupling the two qubits to a low-Q cavity mode playing the role of a dissipative reservoir. We engineer this coupling by applying six continuous-wave microwave drives with appropriate frequencies. The two qubits need not be identical. We show that our approach does not require any fine-tuning of the parameters and requires only that certain ratios between them be large. With currently achievable coherence times, simulations indicate that a Bell state can be maintained over arbitrary long times with fidelities above 94%. Such performance leads to a significant violation of Bell's inequality (CHSH correlation larger than 2.6) for arbitrary long times.