Decay Rate of the l1 Norm Coherence in Single-Qubit Systems

Abstract

We examine to what extent the l1 norm of coherence through an open quantum system is affected by noise. To discuss the effect of the noise, we give a definition of the decay rate of the l1 norm of coherence, i.e., the value of the coherence of initial states divided by the coherence of final states. Then we use the measure of the decay of coherence to discuss to what extent several noisy channels affects the coherence. We find that the decay rate is independent of the initial state parameters but only related to parameters of the phase flip channels, the depolarizing channels, and the amplitude channels. However, the decay rate is related to the initial state parameters and parameters of the bit flip channels. Contrary to the view at first glance, we find that the bit flip channels even have cohering power.