Quantum inseparability is a term used in quantum mechanics to describe the phenomenon whereby two particles that have interacted become entangled such that they can no longer be considered as independent entities. This phenomenon has important implications for our understanding of the nature of reality at the subatomic level.
In classical physics, it is assumed that particles are independent and do not interact with each other. However, in quantum mechanics, particles do not always behave independently. When two particles interact, they become entangled and can no longer be considered as separate entities. This phenomenon was first described by Einstein, Podolsky and Rosen in 1935 cite{EPR35}. It has since been experimentally verified many times cite{bell64, Aspect1982}.
One of the most famous examples of quantum inseparability is the EPR paradox cite{EPR35}. In this thought experiment, two particles are created at the same location and then travel apart from each other. The key feature of this setup is that the two particles remain entangled such that their properties are correlated. For example, if one particle is measured to have spin up then the other particle must also have spin up (or spin down if the first particle had spin down). However, according to classical physics, there should be no way for one particle to know what state the other particle is in since they are spacelike separated. This contradiction between classical physics and quantum mechanics led Einstein to famously declare that “quantum mechanics is spooky action at a distance” cite{EPR35}.
Quantum entanglement has important implications for our understanding of reality. If two particles can remain correlated even when separated by large distances then it means that there must be some kind of underlying connection between them. This non-local connection violates one of the fundamental assumptions of classical physics which states that physical events happen locally i.e., they are only affected by things in their immediate vicinity cite{bell64}. Non-locality implies that there must be something beyond our everyday experience of reality which connects everything together. Some physicists have interpreted this as evidence for a hidden side to reality which we cannot directly observe cite{bell64}.
Experimental tests of quantum inseparability have shown that it really does exist and is not just a mathematical curiosity cite{Aspect1982}. These experiments help us to understand more about how reality works at its most fundamental level. Quantum inseparability provides strong evidence against local realism and suggests that there may be a hidden side to reality which we have yet to fully understand.