Cavity Optomechanical atomic memory for photons with orbital angular momentum*

We propose a quantum memory based on an atomic Bose-Einstein condensate (BEC) in a toroidal ring trap inside an optical cavity, driven by laser carrying orbital angular momentum (OAM). The BEC's persistent currents, lasting up to a minute, make it a strong candidate for long-term storage. Under suitable approximations, the system maps to a standard optomechanical model, enabling optical signal storage and retrieval via a mechanical mode. Beyond extended storage time, this platform offers advantages over electromagnetically induced transparency (EIT)-based schemes, as it does not rely on specific atomic energy levels. It also supports strong single-photon–atom coupling, wavelength conversion, and storage and retrieval of OAM states of light.