  Coherent transduction of quantum states from the microwave to the optical
domain can play a key role in quantum networking and distributed quantum
computing. We present the design of a piezo-optomechanical device formed in a
hybrid lithium niobate on silicon platform, that is suitable for
microwave-to-optical quantum transduction. Our design is based on acoustic
hybridization of an ultra-low mode volume piezoacoustic cavity with an
optomechanical crystal cavity. The strong piezoelectric nature of lithium
niobate allows us to mediate transduction via an acoustic mode which only
minimally interacts with the lithium niobate, and is predominantly
silicon-like, with very low electrical and acoustic loss. We estimate that this
transducer can realize an intrinsic conversion efficiency of up to 35% with
<0.5 added noise quanta when resonantly coupled to a superconducting transmon
qubit and operated in pulsed mode at 10 kHz repetition rate. The performance
improvement gained in such hybrid lithium niobate-silicon transducers make them
suitable for heralded entanglement of qubits between superconducting quantum
processors connected by optical fiber links.
