Decoherence effects on the entangled states in a noisy quantum channel

Decoherence in a two-qubit system caused by interaction with its environment is an interesting problem to study for quantum communication. We present noise models for the two-qubit states by using Kraus operators for each noisy channel; especially bit flip, bit-phase flip, phase flip, phase damping, amplitude damping, and depolarizing channels. By analyzing the possible quantum information changes of the six noisy channels, we use quantum entropy to discuss variations of their fidelity and mixedness. In addition, in order to compare the degree of entanglement between the initial and the output, we investigate the concurrence.