Quantum entanglement is a phenomenon in quantum mechanics where two or more particles become interlinked such that the state of one particle directly influences the state of the other, no matter the distance between them. This interconnection persists even when the particles are separated by vast distances. When particles are entangled, their properties, such as spin, polarization, or position, are correlated in a way that the measurement of one particle’s state instantly determines the state of the other.

Entanglement challenges classical intuitions about locality and separability. According to classical physics, information cannot travel faster than the speed of light, yet entanglement implies an instantaneous connection. This paradox was famously highlighted in the Einstein-Podolsky-Rosen (EPR) paradox, leading Einstein to refer to entanglement as “spooky action at a distance.”

In practical terms, if two entangled particles are generated and one particle is measured, the outcome of the measurement determines the state of the other particle instantaneously, regardless of the spatial separation. This has been experimentally confirmed through numerous tests, demonstrating the non-local nature of quantum mechanics.

Entanglement is a cornerstone of quantum information science, underpinning technologies such as quantum computing and quantum cryptography, where it enables phenomena like superdense coding and quantum teleportation, which have no analogs in classical information theory.