Quantum entanglement and quantum correlation are related concepts in quantum mechanics, but they have distinct meanings.
Quantum entanglement refers to a phenomenon where two or more particles become intrinsically connected in such a way that the state of one particle cannot be described independently of the others. When particles are entangled, their properties become correlated, and measuring the state of one particle can instantaneously affect the state of the other(s), regardless of the distance between them. This non-local connection is a unique characteristic of entangled systems in quantum mechanics.
On the other hand, quantum correlation is a broader term that encompasses various types of correlations that can arise in quantum systems. It refers to the statistical relationships or dependencies between different observables or properties of quantum particles. These correlations can exist even without entanglement.
Quantum correlation can arise in both entangled and separable (non-entangled) quantum states. For example, in separable states, particles may still exhibit statistical correlations, but these correlations can be explained by classical probability theory. However, entangled states exhibit correlations that violate classical probabilistic explanations, as exemplified by the violation of the Bell inequality.
In essence, quantum entanglement is a specific type of quantum correlation that involves a non-local connection between particles, while quantum correlation is a more general term that encompasses the statistical dependencies between observables in quantum systems, regardless of whether they are entangled or separable.