Unitarity as preservation of entropy and entanglement in quantum systems
  The logical structure of Quantum Mechanics (QM) and its relation to other fundamental principles of Nature has been for decades a subject of intensive research. In particular, the question whether the dynamical axiom of QM can be derived from other principles has been often considered. In this contribution, we show that unitary evolutions arise as a consequences of demanding preservation of entropy in the evolution of a single pure quantum system, and preservation of entanglement in the evolution of composite quantum systems. 
Florian Hulpke, Uffe V. Poulsen, Anna Sanpera, Aditi Sen De, Ujjwal   Sen, Maciej Lewenstein