Degree of entanglement for two qubits
Ayman F. Abouraddy, Bahaa E. A. Saleh, Alexander V. Sergienko, Malvin Carl Teich · Physical Review A · 2001
We demonstrate that any pure bipartite state of two qubits may be decomposed into a superposition of a maximally entangled state and an orthogonal factorizable one. Although there are many such decompositions, the weights of the two superposed states are, remarkably, unique. We propose a measure of entanglement based on this decomposition. We also demonstrate that this measure is connected to three measures of entanglement previously set forth: maximal violation of Bell's inequality, concurrence, and two-particle visibility.