Superconducting cavity qubit with tens of milliseconds single-photon coherence time

Abstract: Storing quantum information for an extended period of time is essential for running quantum algorithms with low errors. Currently, superconducting quantum memories have coherence times of a few milliseconds, and surpassing this performance has remained an outstanding challenge. In this work, we report a qubit encoded in a novel superconducting cavity with a coherence time of 34 ms, an improvement of over an order of magnitude compared to previous demonstrations. We use this long-lived quantum memory to store a Schr\"odinger cat state with a record size of 1024 photons, indicating the cavity's potential for bosonic quantum error correction.