A mechanical quantum memory for microwave photons

Long-lived mechanical oscillators are actively pursued as critical resources for quantum storage, sensing, and transduction. However, achieving deterministic quantum control while limiting mechanical dissipation remains a persistent challenge. Here, we demonstrate strong coupling between a transmon superconducting qubit and an ultra-long-lived nanomechanical oscillator $T₁ approx 25 ms$ at 5 GHz, $Q approx 0.8 times 10⁹$ by leveraging the low acoustic loss in silicon and phononic bandgap engineering. The qubit-oscillator system achieves large cooperativity $C_T1approx 1.5times10⁵$, $C_T2approx 150$, enabling the generation of non-classical states and the investigation of mechanisms underlying mechanical decoherence. We show that dynamical decouplingunicode{x2014}implemented through the qubitunicode{x2014}can mitigate decoherence, leading to a mechanical coherence time of T_2approx 1 ms. These findings extend the exceptional storage capabilities of mechanical oscillators to the quantum regime, putting them forward as compact bosonic elements for future applications in quantum computing and metrology.