title: Towards realizing a quantum memory for a superconducting qubit: storage and retrieval of quantum states.
abstract: We have built a hybrid system composed of a superconducting flux qubit (the processor) and an ensemble of nitrogen-vacancy centers in diamond (the memory) that can be directly coupled to one another, and demonstrated how information can be transferred from the flux qubit to the memory, stored, and subsequently retrieved. We have established the coherence properties of the memory and succeeded in creating an entangled state between the processor and memory, demonstrating how the entangled state's coherence is preserved. Our results are a significant step towards using an electron spin ensemble as a quantum memory for superconducting qubits.
authors.affiliation: NTT Basic Research Laboratories, NTT Corporation, 3-1, Morinosato-Wakamiya, Atsugi, Kanagawa 243-0198, Japan.
authors.forename: Shiro
authors.initials: S
authors.lastname: Saito
authors.affiliation: NTT Basic Research Laboratories, NTT Corporation, 3-1, Morinosato-Wakamiya, Atsugi, Kanagawa 243-0198, Japan.
authors.forename: Xiaobo
authors.initials: X
authors.lastname: Zhu
authors.affiliation: NTT Basic Research Laboratories, NTT Corporation, 3-1, Morinosato-Wakamiya, Atsugi, Kanagawa 243-0198, Japan and Vienna Center for Quantum Science and Technology, Atominstitut, TU Wien, 1020 Vienna, Austria.
authors.forename: Robert
authors.initials: R
authors.lastname: Amsüss
authors.affiliation: NTT Basic Research Laboratories, NTT Corporation, 3-1, Morinosato-Wakamiya, Atsugi, Kanagawa 243-0198, Japan.
authors.forename: Yuichiro
authors.initials: Y
authors.lastname: Matsuzaki
authors.affiliation: NTT Basic Research Laboratories, NTT Corporation, 3-1, Morinosato-Wakamiya, Atsugi, Kanagawa 243-0198, Japan.
authors.forename: Kosuke
authors.initials: K
authors.lastname: Kakuyanagi
authors.affiliation: Graduate School of Engineering Science, Osaka University, 1-3 Machikane-yama, Toyonaka, Osaka 560-8531, Japan.
authors.forename: Takaaki
authors.initials: T
authors.lastname: Shimo-Oka
authors.affiliation: Graduate School of Engineering Science, Osaka University, 1-3 Machikane-yama, Toyonaka, Osaka 560-8531, Japan.
authors.forename: Norikazu
authors.initials: N
authors.lastname: Mizuochi
authors.affiliation: National Institute of Informatics, 2-1-2 Hitotsubashi, Chiyoda-ku, Tokyo 101-8430, Japan.
authors.forename: Kae
authors.initials: K
authors.lastname: Nemoto
authors.affiliation: NTT Basic Research Laboratories, NTT Corporation, 3-1, Morinosato-Wakamiya, Atsugi, Kanagawa 243-0198, Japan.
authors.forename: William J
authors.initials: WJ
authors.lastname: Munro
authors.affiliation: NTT Basic Research Laboratories, NTT Corporation, 3-1, Morinosato-Wakamiya, Atsugi, Kanagawa 243-0198, Japan and National Institute of Informatics, 2-1-2 Hitotsubashi, Chiyoda-ku, Tokyo 101-8430, Japan.
authors.forename: Kouichi
authors.initials: K
authors.lastname: Semba