Quantum Criticality and State Engineering in the Simulated Anisotropic Quantum Rabi Model

Promising applications of the anisotropic quantum Rabi model (AQRM) in broad parameter ranges are explored, which is realized with superconducting flux qubits simultaneously driven by two-tone time-dependent magnetic fields. Regarding the quantum phase transitions (QPTs), with assistance of fidelity susceptibility, we extract the scaling functions and the critical exponents, with which the universal scaling of the cumulant ratio is captured by rescaling the parameters related to the anisotropy. Moreover, a fixed point of the cumulant ratio is predicted at the critical point of the AQRM with finite anisotropy. In respect of quantum information tasks, the generation of the macroscopic Schrödinger cat states and quantum controlled phase gates are investigated in the degenerate case of the AQRM, whose performance is also investigated by numerical calculation with practical parameters. Therefore, our results pave the way to explore distinct features of the AQRM in circuit QED systems for QPTs, quantum simulations and quantum information processing. © 2018 The Author(s). Published by IOP Publishing Ltd on behalf of Deutsche Physikalische Gesellschaft.