Alternative framework for quantifying coherence
  We propose an alternative framework for quantifying coherence. The framework is based on a natural property of coherence, the additivity of coherence for subspace-independent states, which is described by an operation-independent equality rather than operation-dependent inequalities and therefore applicable to various physical contexts. Our framework is compatible with all the known results on coherence measures but much more flexible and convenient for applications, and by using it many open questions can be resolved. 
Xiao-Dong Yu, Da-Jian Zhang, G. F. Xu, and D. M. Tong
quant-ph