VietNam 2013 

IXth Rencontres du Vietnam
Quy-Nhon, August 4-10, 2013


 Nanophysics: from fundamentals to applications

(the return)


Saturday 10
Closing session

› 10:30 - 11:00 (30min)
Coherent Coupling of a Superconducting Flux Qubit to an Electron Spin Ensemble in Diamond
Yasuhiro Tokura  1@  , Shiro Saito  2@  , Yuichiro Matsuzaki  2@  , William Munro  2@  , Kae Nemoto  3@  , Norikazu Mizuochi  4@  , Koichi Semba  3@  
1 : University of Tsukuba  (U. Tsukuba)
1-1-1 Tennodai, Tsukuba, Ibaraki 305-8571 -  Japan
2 : NTT Basic Research Laboratories  (NTT BRL)
3-1, Wakamiya, Morinosato, Atsugi -  Japan
3 : National Institute of Informatics  (NII)
2-1-2 Hitotsubashi, Chiyoda-ku, Tokyo -  Japan
4 : University of Osaka
1-3 Machikane-yama, Toyonaka, Osaka -  Japan

During the past decade, research on superconducting qubits based on Josephson junctions has made rapid progress and many foundational experiments have been performed. However, the experimentally reported coherence times are likely to be insufficient for future large-scale quantum computation. A natural solution to this problem is a dedicated quantum memory based on atomic and molecular systems. The question of whether coherent quantum coupling is possible between such natural systems and a single macroscopic artificial atom has attracted considerable attention. Here we report evidence of coherent strong coupling between a single macroscopic superconducting artificial atom (a flux qubit) and an ensemble of electron spins in the form of nitrogen–vacancy colour centres in diamond. Furthermore, we have observed coherent exchange of a single quantum of energy between a flux qubit and a macroscopic ensemble consisting of about 3x10^7 such colour centres. We report the memory time of 20 ns, which is limited by an effective T1 of the NV- spin ensemble. We have measured coherence time of the entangled state composed of two different macroscopic quantum system. The obtained result provides a foundation for future quantum memories and hybrid devices coupling microwave and optical systems.

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