title: The classical correlation limits the ability of the measurement-induced average coherence.
abstract: Coherence is the most fundamental quantum feature in quantum mechanics. For a bipartite quantum state, if a measurement is performed on one party, the other party, based on the measurement outcomes, will collapse to a corresponding state with some probability and hence gain the average coherence. It is shown that the average coherence is not less than the coherence of its reduced density matrix. In particular, it is very surprising that the extra average coherence (and the maximal extra average coherence with all the possible measurements taken into account) is upper bounded by the classical correlation of the bipartite state instead of the quantum correlation. We also find the sufficient and necessary condition for the null maximal extra average coherence. Some examples demonstrate the relation and, moreover, show that quantum correlation is neither sufficient nor necessary for the nonzero extra average coherence within a given measurement. In addition, the similar conclusions are drawn for both the basis-dependent and the basis-free coherence measure.
authors.affiliation: College of Mathematics, Institute of Mathematics, Taiyuan University of Technology, Taiyuan 030024, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Zhang
authors.affiliation: School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024, China.
authors.forename: Si-Ren
authors.initials: SR
authors.lastname: Yang
authors.affiliation: School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024, China.
authors.forename: Yang
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024, China.
authors.forename: Chang-Shui
authors.initials: CS
authors.lastname: Yu