Discrimination between pure states and mixed states
Chi Zhang, Guoming Wang, Mingsheng Ying · Physical Review A · 2007
In this paper, we discuss the problem of determining whether a quantum system is in a pure state, or in a mixed state. We apply two strategies to settle this problem: the unambiguous discrimination and the maximum confidence discrimination. We prove that the optimal versions of both strategies are equivalent. Furthermore, the scheme also provides a method to estimate the purity of quantum states, and the Schmidt number of composed systems.