Stimulated Raman adiabatic passage in optomechanics

Stimulated Raman adiabatic passage (STIRAP) describes adiabatic population transfer between two states coherently coupled via a mediating state that remains unoccupied. This renders STIRAP robust against loss in the mediating state, leading to profound applications in atomic- and molecular-beam research, trapped-ion physics, superconducting circuits, other solid-state systems, optics, in entanglement generation and qubit operations. STIRAP in optomechanics has been considered for optical frequency conversion where a mechanical mode provides the mediating state. Given the advances of optomechanical devices with exceptionally high mechanical-quality factors, STIRAP between mechanical modes has the prospect of generating macroscopic quantum superposition and of supporting quantum information protocols. An optical cavity mode can mediate the coupling between mechanical modes, without detrimental effects of optical losses. We demonstrate STIRAP between two mechanical modes of a phononic membrane-in-the-middle system with an efficiency of 86% and immune against photon loss through the mediating optical cavity.