What is entanglement?

Quantum entanglement is a fundamental phenomenon in quantum mechanics where two particles are connected in such a way that their quantum states are interdependent, regardless of the distance between them. This connection implies that the state of one particle instantaneously affects the state of the other, even if they are light years apart. This phenomenon challenges classical notions of causality and locality, reflecting a non-classical correlation between quantum states.

In simpler terms, if you measure the state of one entangled particle, you instantly determine the state of the other, no matter how far apart they are. This feature of quantum mechanics does not have an analog in classical mechanics, where objects are considered separate and independent unless interacted with directly 1.

Sean Carroll further elucidates that in entanglement, if one particle is found in one location, the entangled partner’s behavior is simultaneously defined. This state of entanglement holds true across any distance, emphasizing that quantum fields, not particles, involve vibrations that can be entangled across vast spaces, thereby challenging our standard understanding of locality and communication in physics 1.