Preparation and non-classical characteristics of two-mode entangled coherent state

Abstract

We propose a scheme to generate two-mode entangled coherent states using a Λ-type rf-SQUID qubit to induce the interaction between two transmission line resonators (TLRs). The proposed scheme takes advantage of the easy integration of solid quantum circuit. Through investigating the dynamical evolution, we find the relationship between the initial quantum state of the superconducting qubit and the quantum entanglement of the field modes. We analyze as well the influence of decoherence effect on the non-classical characteristics of the optical field by means of the density operator, fidelity and Mandel Q. The investigation results indicate that one should first optimize the preparation of the initial quantum state of qubit so as to prepare two-mode entangled state with high entanglement degree and obvious non-classical characteristics. The qubit initially prepared in (|0〉+|1〉)/2 does not get entangled with the two modes of field. Inversely, the qubit can effectively improve the degree of entanglement between field modes and obviously promote the anti-bunching effect and squeezing effect if it is initially prepared in ground state |0〉.