Superconducting nonlinear circuits are a promising candidate platform to build quantum machines capable of computations at a currently inaccessible level of complexity. Technological advances of the past decade have improved these systems’ coherence times and gate fidelities such that logistical questions about their scalability have become more pressing. Cabling, control electronics, and on-chip real estate are required for qubit state manipulation and measurement – these requirements become more and more daunting as the number of qubits grows. Current approaches, which use superconducting electromagnetic cavities as quantum memory elements and on-chip filters, work very well but suffer from large spatial requirements.
We can circumvent some of these obstacles by leveraging nanomechanical systems. The factor of 100,000x reduction in propagation velocity between acoustic and electromagnetic waves makes nanomechanical cavities and waveguides extremely compact compared to their electromagnetic counterparts at the same operating frequency. Moreover, nanomechanical cavities are capable of extraordinarily long coherence times (on the order of one second) which is several orders of magnitude beyond electromagnetic cavities. By taking advantage of the phononic degree of freedom, we can use nanomechanical devices to realize new, hardware-efficient architectures for quantum computation.