Quantifying the phase of quantum states.

Phase is a basic ingredient for quantum states since quantum mechanics uses complex numbers to describe quantum states. In this work, we introduce a rigorous framework to quantify the phase of quantum states. To do so, we regard phase as a quantum resource, and specify the free states and free operations. We determine the conditions a phase measure should satisfy and provide some phase measures. We also propose the notion of intrinsic phase for quantum states. • We introduce a rigorous framework to quantify the phase of quantum states. • We determine the conditions a phase measure should satisfy and provide some phase measures. • We propose the notion of intrinsic phase for quantum states. [ABSTRACT FROM AUTHOR]