Direct piezoelectric transduction to a silicon single-mode acoustic waveguide

Quantum computing and communication technologies require the development of long-lived quantum memory elements to accelerate progress. Recent results in quantum acoustics suggests that nanomechanics are an attractive platform for building quantum memories and interfacing with existing superconducting qubits to form scalable quantum architectures. In particular, acoustic waveguides can store many "flying" qubits in a compact footprint while also providing the necessary time-delayed feedback for measurement based quantum computing schemes. Additionally, phonons with ultralong coherence times have been demonstrated in silicon and strong coupling has been shown between superconducting qubits and lithium niobate (LN) nanomechanics. In this work, we design a lithium niobate transducer which is piezoelectrically coupled to microwaves and mechanically coupled to a single mode silicon acoustic waveguide. The devices are fabricated using electron beam lithography and a transfer print technique for heterogeneous integration of LN and Si. Measurements at 10mK allow us to extract the parameters of the coupled mode system as well as the energy relaxation and decoherence times of the silicon delay line modes. Future efforts toward integration with superconducting qubits will also be discussed.