Optical quantum memories, which store and preserve the quantum state of photons, rely on a coherent mapping of the photonic state onto matter states that are optically accessible. Here we outline a new physical mechanism to map the state of photons onto the long-lived but optically inaccessible collective state of noble-gas spins. The mapping employs the coherent spin-exchange interaction arising from random collisions with alkali vapor. We analyze optimal strategies for high-efficiency storage and retrieval of non-classical light at various parameter regimes. Based on these strategies, we identify feasible experimental conditions for realizing efficient quantum memories with noble-gas spins having hours-long coherence times at room temperature and above

1 aKatz, Or1 aReches, Eran1 aShaham, Roy1 aGorshkov, Alexey, V.1 aFirstenberg, Ofer uhttps://arxiv.org/abs/2007.0877001230nas a2200157 4500008004100000245007400041210006900115260001400184520074400198100001300942700001600955700001700971700002500988700002201013856003701035 2020 eng d00aOptimal control of an optical quantum memory based on noble-gas spins0 aOptimal control of an optical quantum memory based on noblegas s c7/20/20203 aIn Ref. [Katz et al., arXiv:2007.08770 (2020)], we present a mechanism and optimal procedures for mapping the quantum state of photons onto an optically inaccessible macroscopic state of noble-gas spins, which functions as a quantum memory. Here we introduce and analyze a detailed model of the memory operation. We derive the equations of motion for storage and retrieval of non-classical light and design optimal control strategies. The detailed model accounts for quantum noise and for thermal atomic motion, including the effects of optical mode structure and imperfect anti-relaxation wall coating. We conclude with proposals of practical experimental configurations of the memory, with lifetimes ranging from seconds to hours.

1 aKatz, Or1 aShaham, Roy1 aReches, Eran1 aGorshkov, Alexey, V.1 aFirstenberg, Ofer uhttps://arxiv.org/abs/2007.10177