title: Quantum memory for microwave photons in an inhomogeneously broadened spin ensemble.
abstract: We propose a multimode quantum memory protocol able to store the quantum state of the field in a microwave resonator into an ensemble of electronic spins. The stored information is protected against inhomogeneous broadening of the spin ensemble by spin-echo techniques resulting in memory times orders of magnitude longer than previously achieved. By calculating the evolution of the first and second moments of the spin-cavity system variables for current experimental parameters, we show that a memory based on nitrogen vacancy center spins in diamond can store a qubit encoded on the |0> and |1> Fock states of the field with 80% fidelity and outperform classical memory strategies for storage times ≤69  μs.
authors.affiliation: Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000 Aarhus C, Denmark. brianj@phys.au.dk
authors.forename: Brian
authors.initials: B
authors.lastname: Julsgaard
authors.forename: Cécile
authors.initials: C
authors.lastname: Grezes
authors.forename: Patrice
authors.initials: P
authors.lastname: Bertet
authors.forename: Klaus
authors.initials: K
authors.lastname: Mølmer