This talk will describe Cleland Lab's efforts in quantum acoustics, where they are exploring the use of individual itinerant phonons for possible applications to quantum computing and quantum sensing. Using superconducting qubits as deterministic sources and detectors of individual microwave-frequency phonons, they can create individual phonons in a mechanical resonator; generate quantum entangled states between phonons in two physically separate mechanical resonators; transmit quantum states between superconducting qubits via phonons, and generate quantum entanglement by sharing “half-phonons” between two superconducting qubits.

By assembling a single-phonon interferometer, Cleland Lab has demonstrated the acoustic version of the Hong-Ou-Mandel effect from quantum optics, which in turn has allowed us to demonstrate coherent one- and two-phonon classically-controlled phase gates. These point to the possible development of a phonon-based architecture for quantum computing, in which phonons, generated as “throw-away” qubits, can in principle allow scaling to very large numbers of qubits at little additional expense. Andrew Cleland will also very briefly describe our recent efforts to use this new technology for quantum sensing.