title: Quantum phases in circuit QED with a superconducting qubit array.
abstract: Circuit QED on a chip has become a powerful platform for simulating complex many-body physics. In this report, we realize a Dicke-Ising model with an antiferromagnetic nearest-neighbor spin-spin interaction in circuit QED with a superconducting qubit array. We show that this system exhibits a competition between the collective spin-photon interaction and the antiferromagnetic nearest-neighbor spin-spin interaction, and then predict four quantum phases, including: a paramagnetic normal phase, an antiferromagnetic normal phase, a paramagnetic superradiant phase, and an antiferromagnetic superradiant phase. The antiferromagnetic normal phase and the antiferromagnetic superradiant phase are new phases in many-body quantum optics. In the antiferromagnetic superradiant phase, both the antiferromagnetic and superradiant orders can coexist, and thus the system possesses Z(z)₂ ⊗ Z₂ symmetry. Moreover, we find an unconventional photon signature in this phase. In future experiments, these predicted quantum phases could be distinguished by detecting both the mean-photon number and the magnetization.
authors: 1] Institute of Theoretical Physics, Shanxi University, Taiyuan 030006, P. R. China [2] State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Laser spectroscopy, Shanxi University, Taiyuan 030006, P. R. China.
authors: Yuanwei
authors: Y
authors: Zhang
authors: 1] State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Laser spectroscopy, Shanxi University, Taiyuan 030006, P. R. China [2] School of Physical Science and Technology, Soochow University, Suzhou, Jiangsu 215006, P. R. China.
authors: Lixian
authors: L
authors: Yu
authors: Institute of Theoretical Physics, Shanxi University, Taiyuan 030006, P. R. China.
authors: J-Q
authors: JQ
authors: Liang
authors: State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Laser spectroscopy, Shanxi University, Taiyuan 030006, P. R. China.
authors: Gang
authors: G
authors: Chen
authors: State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Laser spectroscopy, Shanxi University, Taiyuan 030006, P. R. China.
authors: Suotang
authors: S
authors: Jia
authors: 1] CEMS, RIKEN, Saitama 351-0198, Japan [2] Physics Department, The University of Michigan, Ann Arbor, Michigan 48109-1040, USA [3] Department of Physics, Korea University, Seoul 136-713, Korea.
authors: Franco
authors: F
authors: Nori