Quantum Memory for Microwave Photons in an Inhomogeneously Broadened Spin Ensemble

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 broken vertical bar 1 > Fock states of the field with 80% fidelity and outperform classical memory strategies for storage times <= 69 mu s.