Long-lived and Efficient Optomechanical Memory for Light.

We demonstrate a memory for light based on optomechanically induced transparency. We achieve a long storage time by leveraging the ultralow dissipation of a soft-clamped mechanical membrane resonator, which oscillates at MHz frequencies. At room temperature, we demonstrate a lifetime T_{1}≈23  ms and a retrieval efficiency η≈40% for classical coherent pulses. We anticipate the storage of quantum light to be possible at moderate cryogenic conditions (T≈10  K). Such systems could find applications in emerging quantum networks, where they can serve as long-lived optical quantum memories by storing optical information in a phononic mode.