(Phys.org)—Quantum entanglement—which occurs when two or more particles are correlated in such a way that they can influence each other even across large distances—is not an all-or-nothing phenomenon,but occurs in various degrees. The more a quantum state is entangled with its partner, the better the states will perform in quantum information applications. Unfortunately, or quantifying entanglement is a difficult process involving complex optimization problems that give even physicists headaches.
Source: phys.org