Quantum entanglement is a physical phenomenon that occurs when a group of particles are generated, interact, or share spatial proximity in a way such that the quantum state of each particle of the group cannot be described independently of the state of the others, including when the particles are separated by a large ...

What causes entanglement?

Entanglement occurs when a pair of particles, such as photons, interact physically. A laser beam fired through a certain type of crystal can cause individual photons to be split into pairs of entangled photons. The photons can be separated by a large distance, hundreds of miles or even more.

Does quantum entanglement occur naturally?

Cakes don't count as quantum systems, of course, but entanglement between quantum systems arises naturally—for example, in the aftermath of particle collisions. ... There are many ways to create entangled states. One way is to make a measurement of your (composite) system that gives you partial information.