Overview#Entanglement within the Quantum realm, is when you have two Qbit that are Entanglement
In 1935 Albert Einstein, Boris Podolsky and Nathan Rosen in their EPR paradox theorised that quantum mechanics might not be a local theory, because a measurement made on one of a pair of separated but entangled particles causes a simultaneous effect, the collapse of the wave function, in the remote particle (i.e. an effect exceeding the speed of light). But because of the probabilistic nature of wave function collapse, this violation of locality cannot be used to transmit information faster than light.
In 1964 John Stewart Bell formulated the "Bell inequality", which, if violated in actual experiments, implies that quantum mechanics violates either locality or realism, another principle which relates to the value of unmeasured quantities. The two principles are commonly referred to as a single principle, local realism.
“spooky actions at a distance”#Another of the remarkable features of the microscopic world prescribed by quantum theory is the idea of nonlocality, what Albert Einstein rather dismissively called “spooky actions at a distance”.
Nonlocality describes the apparent ability of objects to instantaneously know about each other’s state, even when separated by large distances (potentially even billions of light years), almost as if the universe at large instantaneously arranges its particles in anticipation of future events.
The assumption is that the 'nonlocal' part of quantum nonlocality refers to the entanglement of properties across space. But what if entanglement also occurs across time? Is there such a thing as temporal nonlocality?
The answer, as it turns out, is yes.
Just when you thought quantum mechanics couldn't get any weirder, a team of physicists at the Hebrew University of Jerusalem reported in 2013 that they had successfully entangled photons that never coexisted.