First-principles simulation of an optomechanical memory for quantum entanglement

Optomechanical systems cooled to the quantum level provide a promising mechanism for a high-fidelity quantum memory that is faithful to a given temporal mode structure, and can be recovered synchronously. We carry out full, probabilistic quantum simulations of a quantum optomechanical memory, including nonlinear effects that are usually ignored. This is achieved using both the approximate truncated Wigner and the exact positive P phase space representations. Our simulations allow us to probe the regime where the linearization approximation fails to hold. We show evidence for large spectral overlap between the quantum signal and the transfer field in typical optomechanical quantum memory experiments. Methods for eliminating this overlap to accurately recover the quantum signal are discussed. Using these methods, a strategy for generating EPR entanglement between two separated optomechanical oscillators is analyzed, using entangled radiation produced from downconversion and stored in an initiating cavity. We show that the use of pulsed entanglement with optimally shaped temporal modes can efficiently transfer quantum entanglement into a large-scale macroscopic mechanical mode, then remove it after a fixed waiting time for measurement.