QUROPE Quantum Information Processing and Communication in Europe

We show that trace distance measure of coherence is a strong monotone for all qubit and, so called, X states. An expression for the trace distance coherence for all pure states and a semidefinite program for arbitrary states is provided. We also explore the relation between l1-norm and relative entropy based measures of coherence, and give a sharp inequality connecting the two. In addition, it is shown that both lp-norm- and Schatten-p-norm–based measures violate the (strong) monotonicity for all p \in (1, \infty).