Scheme for realizing quantum-information storage and retrieval from quantum memory based on nitrogen-vacancy centers

We demonstrate a scheme for realizing quantum-information storage (retrieval) into (from) a quantum memory using a hybrid quantum system, which consists of $N$ nitrogen-vacancy (N-$V$) centers (as memory), $N$ transmission line resonators (TLRs) (as data bus), and $N$ current-biased Josephson-junction (CBJJ) superconducting phase qubits (as heads of read and write). By virtually exciting the vibrational modes of the TLRs, this can produce an effective coupling between the N-$V$ centers and the CBJJs in the system. Because the operation time ($\ensuremath{\sim}{10}^{\ensuremath{-}8}$ s) is much shorter than the decoherence time of the CBJJ ($\ensuremath{\sim}{10}^{\ensuremath{-}5}$ s), the quantum information can be transferred between the N-$V$ centers and the CBJJs easily. Owing to the strong-coupling condition $[\ensuremath{\lambda}/2\ensuremath{\pi}\ensuremath{\gg}({\ensuremath{\gamma}}_{eg},\ensuremath{\Gamma},{\ensuremath{\gamma}}_{\ensuremath{\phi}})]$ and the long coherence time ($\ensuremath{\sim}{10}^{\ensuremath{-}3}$ s) of the N-$V$ centers, the quantum information can be stored in the memory steadily, and it can be retrieved with a high fidelity ($g96%$). This scheme provides a scalable way of exchanging quantum information between different quantum interfaces, and has the experimental feasibility with currently available experimental technology.