Quantum coherence is the essence of quantum entanglement

Quantum entanglement is an intriguing concept that is vital to quantum computing, quantum communication and teleportation. The numerous experiments called Bell tests act as evidence of quantum entanglement. However, the exact meaning of quantum entanglement is somewhat vague. One interpretation is the instant inner connection between totally separated entangled particles, or the ‘spooky action at a distance’ termed by Einstein. The paper has examined the Bell tests from different perspectives and discovered that although the Bell tests have disproved the local hidden variable hypothesis and proved nonlocal correlation, they do not automatically endorse any inner connection between totally separated entangled particles, such as superluminal communication and superposition over a large distance. The measurement on one entangled particle does not change the quantum state of its counterpart, so any inner connection is not necessary. The nonlocal correlation shown by Bell tests can be explained by coherence states of entangled particles and the common interaction between particles and measuring instruments. The paper concludes that the essence of quantum entanglement is the coherence of quantum states.