Cat qubit stabilization with a DC-biased Josephson junction

Quantum error correction is crucial for the advancement of scalable quantum computing, which will rely on fault-tolerant architectures. Cat qubits offer a hardware-efficient approach towards fault tolerance. Previous proposals and experimental demonstrations of cat codes rely on microwave pumps to engineer two-photon dissipation and two-photon drive of a quantum memory made of a superconducting resonator. The key parameter to maximize is the ratio between the two-photon dissipation rate and the residual single-photon loss rate.

We present a novel approach to stabilizing cat qubits by engineering dissipation in a resonator using a DC-biased Josephson junction. The required two-photon dissipation is achieved through inelastic Cooper-pair tunneling under a DC voltage bias. In contrast with established microwave-pumped schemes, which introduce unwanted nonlinearities, I will show that this technique should suppress most of them. This new approach should thus enable two-photon dissipation rates up to 100 times higher than state-of-the-art methods.

I will show experimental results demonstrating the feasibility of our approach. In particular, I will show the first demonstration of engineered dissipation of a quantum memory using a DC-biased Josephson junction. We observe tunable single-photon dissipation as well as two-photon dissipation of the quantum memory, where a cat qubit could be stored.