On-demand generation of quantum photonic resource states using a phononic memory

Fusion-based linear optical quantum computing using dual-rail qubits typically relies on spontaneous parametric down-conversion sources, which act as probabilistic single photon sources. Although the probability of generation is low, a successful event can be heralded. Successfully generated photons pass through a complex network which multiplexes them into definite spatiotemporal slots for further processing. In this work, we propose a scheme for on-demand single photon generation through optomechanical readout of phononic resonator arrays which buffer single-phonon states. First, the opto-mechanical coupling is used to probabilistically generate and herald a single phonon. Due to the long phononic lifetime, the single quantum excitation can be stored in the phonon mode until needed, at which time it can be deterministically converted to an optical photon and integrated into a linear-optic network. Our proposal for linear-optic quantum computing based on phononic quantum memories greatly simplifies optical routing and resource requirements by displacing the redundancy necessary whenever using probabilistic state generation from space into time.