The von Neumann entropy and unitary equivalence of quantum states

Abstract

K. He, J. Hou and M. Li have recently given a sufficient and necessary condition for unitary equivalence of quantum states. This condition is based on the von Neumann entropy. In this note, we first give a short proof of their result, and then we improve it.

Keywords:

• von Neumann entropy
• quantum states
• unitary equivalence

AMS Subject Classification:

• 15A15

Acknowledgements

The author was supported in part by the Slovenian Research Agency.