Dissipative stabilization of a squeezed-like cat qubit

Dissipative cat-qubits are a promising architecture for assembling a quantum processor due to their built-in quantum error correction properties. Owing to the two-photon dissipation, their bit-flip error rate is exponentially suppressed by a factor exp(−γn) as the cat size n is increased, only at a linear cost in phase-flip rate. This results in a significant reduction of the number of qubits required for fault-tolerant quantum computation. A deformation of the basis states increasing their separation could result in a further reduction of the bit-flip error rate. In this work, we propose and implement a squeezing-like deformation of the cat qubit basis states, achieved with the same longitudinal interaction used to perform ancilla-free parity measurement. We demonstrate an unprecedented exponential suppression of the bit-flip error rate with a scaling factor up to γ = 4, at a limited cost in phase flip rate. We measure bit-flip times of 60s for a 1 µs phase flip time for a cat of size n = 5.Moreover, we demonstrate that squeezing also improves the qubit Rabi flopping performance, dividing the phase-flip rate by a factor two. This simple yet effective technique enhances cat qubit performances, and brings multi-cat architectures a step closer to the error correction threshold.