title: Generation of a macroscopic entangled coherent state using quantum memories in circuit QED.
abstract: W-type entangled states can be used as quantum channels for, e.g., quantum teleportation, quantum dense coding, and quantum key distribution. In this work, we propose a way to generate a macroscopic W-type entangled coherent state using quantum memories in circuit QED. The memories considered here are nitrogen-vacancy center ensembles (NVEs), each located in a different cavity. This proposal does not require initially preparing each NVE in a coherent state instead of a ground state, which should significantly reduce its experimental difficulty. For most of the operation time, each cavity remains in a vacuum state, thus decoherence caused by the cavity decay and the unwanted inter-cavity crosstalk are greatly suppressed. Moreover, only one external-cavity coupler qubit is needed, which simplifies the circuit.
authors: Department of Physics, Hangzhou Normal University, Hangzhou, Zhejiang 310036, China.
authors: Tong
authors: T
authors: Liu
authors: Department of Physics, Hangzhou Normal University, Hangzhou, Zhejiang 310036, China.
authors: Qi-Ping
authors: QP
authors: Su
authors: Department of Physics, Hangzhou Normal University, Hangzhou, Zhejiang 310036, China.
authors: Shao-Jie
authors: SJ
authors: Xiong
authors: State Key Laboratory of Precision Spectroscopy, Department of Physics, East China Normal University, Shanghai 200062, China.
authors: Jin-Ming
authors: JM
authors: Liu
authors: Department of Physics, Hangzhou Normal University, Hangzhou, Zhejiang 310036, China.
authors: Chui-Ping
authors: CP
authors: Yang
authors: CEMS, RIKEN, Saitama 351-0198, Japan.|Department of Physics, The University of Michigan, Ann Arbor, Michigan 48109-1040, USA.
authors: Franco
authors: F
authors: Nori