Effects of thermal reservoir on the qubit squeezing of artificial atomic qubits inside the cavity

Abstract

In the present paper, an analytical description of a superconducting charge qubit, coupled to a dissipative on-chip cavity in thermal bath, is found. We investigate the entropy squeezing and variance squeezing of the charge qubit under the parameters of the damping rate, thermal photons, the intensity of coherent state and qubit distribution angle. It is interesting to note that: (i) The charge qubit squeezing can be protected for a long time when both the damping rate and thermal photons effects are simultaneously considered. (ii) The appearance and disappearance of the squeezing phenomena depend on the coherence intensity and the qubit distribution angle. (iii) Entropy squeezing is more precise than variance squeezing as a measure of the squeezing. The entanglement and the coherence loss, by using the Bloch vector, of a superconducting qubit are investigated. It was found that the coupling to the thermal reservoirs leads to persistent purity loss and entanglement death, they remain nearly invariant regardless of the increase of time.