Quantum Information Transfer Based on Frequency Modes in Circuit QED

We propose a scheme for implementing quantum information transfer based on frequency modes of microwave photons in a superconducting circuit. In our proposal, quantum information can be encoded on frequency modes of microwave photons, which act as a qubit in the resonator. Operations for the qubit, which is a process involving parametric frequency conversion, can be implemented by adjusting biased-dc superconducting quantum interference (SQUID). The coupling between two resonators can be controlled by tuning the frequency of the LC circuit inserted by a dc SQUID with two Josephson-junctions (2JJ-SQUID). Compared with previous ones, our work can avoid dephasing and decoherence resulting from atom decay. In addition, the resonator which includes multiple photons in two frequency modes can play a role of an identical atomic ensemble, which could lead to photon blockade.