Stabilizing a Bell state of two superconducting qubits by dissipation engineering

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. Entanglement is a fundamental, yet counter-intuitive concept in quantum mechanics. Maximally entangled two-qubit states, often called Bell states, violate classical correlation properties [1‐4] and are an essential building block for quantum communication and quantum information. Unfortunately, these states are also dicult to generate and sustain as interaction with the environment typically leads to rapid loss of their unique quantum properties. Therefore, stabilizing a Bell state is a sought after goal. Quantum state stabilization can be achieved by an active feedback loop in which the system is measured, and conditioned on the measurement of an error, a gate restores the system to the desired state [5, 6]. This approach suers from the latency of data acquisition and