Evolution of Relative Entropy of Coherence for Two Qubits States

In this paper, we calculate relative entropy of coherence of the output state of two qubits X states with 5 parameters when one subsystem or two subsystems goes through the amplitude damping channel n times. We find that relative entropy of coherence of the output state decreases as the parameter g of the amplitude damping channel continuously changes from zero to one no matter how much n is. The curvature of relative entropy of coherence for the output state loosely increases gradually as n increases. Furthermore when n is larger, frozen coherence can appear as the parameter g of the amplitude damping channel increases.