Published online by Cambridge University Press: 03 May 2018
We aim to characterise those transformations on the set of density operators (which are the mathematical representatives of the states in quantum information theory) that preserve a so-called generalised entropy of one fixed convex combination of operators. The characterisation strengthens a recent result of Karder and Petek where the preservation of the same quantity was assumed for all convex combinations.
This work was supported by the National Research, Development and Innovation Office NKFIH Reg. No. K-115383.