Albert Einstein's famous skepticism about quantum mechanics is encapsulated in his phrase "spooky action at a distance," which references phenomena like quantum entanglement. Quantum entanglement occurs when two particles become linked and instantaneously affect each other, regardless of the distance separating them. This rebellion against local realism posed by quantum entanglement caused Einstein to doubt the completeness of quantum mechanics.
Despite Einstein's reservations, numerous experiments, including those conducted over the past few decades, have successfully validated the reality of quantum entanglement. Bell's Theorem and related experimental validations, such as Aspect's experiments, have shown that no local hidden variable theories can reproduce the statistical predictions of quantum mechanics.
These experiments demonstrate that entangled particles exhibit correlations that cannot be explained by any classical means and assure that quantum mechanics complies with empirically verified predictions concerning these correlations. The implication is profound: the fundamental aspects of quantum mechanics defy classical intuition, confirming non-local interactions beyond the conceptual confines of classical physics. This aspect of reality necessitates a reevaluation of how information and causation operate at quantum scales, lending credibility to quantum mechanics as a complete theory to describe physical phenomena.