A description of entanglement in terms of quantum phase

Luis L. Sanchez-Soto, Julian Delgado, Andrei B. Klimov, Gunnar Bjork

Published 2002-02-19, updated 2002-08-06Version 2

We explore the role played by the phase in an accurate description of the entanglement of bipartite systems. We first present an appropriate polar decomposition that leads to a truly Hermitian operator for the phase of a single qubit. We also examine the positive operator-valued measures that can describe the qubit phase properties. When dealing with two qubits, the relative phase seems to be a natural variable to understand entanglement. In this spirit, we propose a measure of entanglement based on this variable.