A Phononic Bus for Coherent Interfaces Between a Superconducting Quantum\n Processor, Spin Memory, and Photonic Quantum Networks

We introduce a method for high-fidelity quantum state transduction between a\nsuperconducting microwave qubit and the ground state spin system of a\nsolid-state artificial atom, mediated via an acoustic bus connected by\npiezoelectric transducers. Applied to present-day experimental parameters for\nsuperconducting circuit qubits and diamond silicon vacancy centers in an\noptimized phononic cavity, we estimate quantum state transduction with fidelity\nexceeding 99\\% at a MHz-scale bandwidth. By combining the complementary\nstrengths of superconducting circuit quantum computing and artificial atoms,\nthe hybrid architecture provides high-fidelity qubit gates with long-lived\nquantum memory, high-fidelity measurement, large qubit number, reconfigurable\nqubit connectivity, and high-fidelity state and gate teleportation through\noptical quantum networks.\n