Bistability of qubit chains coupled to a superconducting resonator

Hui Wang, Rui Wang, Daichi Sugiyama +5 more

O. Buisson, F. W. J. Hekking

Joel Strand

Sheng-li Ma, Zhen Li, Fuli Li +1 more

A dissipative scheme is proposed to generate single- or two-mode squeezed states in a hybrid quantum system consisting of superconducting resonators and nitrogen-vacancy-center ensembles (NVEs). For the single-mode squeezing generation, we consider an array of linearly coupled superconducting resonators, each of which is magnetically coupled to a NVE. In addition, one of the resonators is coupled to a gap-tunable qubit. It is shown that at steady state all the resonators and NVEs in the array can enter into single-mode squeezed states via dissipation of the qubit. For the two-mode squeezing realization, we consider a pair of superconducting resonator chains, which are coupled to two gap-tunable qubits. We find that at steady state all the resonator pairs in the up and down chains will be steered into two-mode squeezed states via dissipation of the qubits. The present scheme has a remarkable feature: only one or two gap-tunable dissipative qubits are locally involved, and no squeezing resource is required.

Lin Tian

Superconducting qubits connected in an array can form quantum many-body systems such as the quantum Ising model. By coupling the qubits to a superconducting resonator, the combined system forms a circuit QED system. Here, we study the nonlinear behavior in the many-body state of the qubit array using a semiclassical approach. We show that sudden switchings as well as a bistable regime between the ferromagnetic phase and the paramagnetic phase can be observed in the qubit array. A superconducting circuit to implement this system is presented with realistic parameters.

Giovanna Tancredi, Themis Mavrogordatos, Matthew Elliott +6 more