What does it mean to be ‘quantum’? A physicist explains the basics behind Einstein’s spooky actions at a distance

In quantum entanglement, you can learn something about one particle by observing the other in its pair, even across vast distances. koto_feja/E+ via Getty Images Imagine shining a flashlight across a dark room. You can predict exactly what the light will do: travel in a straight line from one point to another. That seems obvious, because in the world we see around us, light appears to follow a single, clear path. Quantum mechanics paints a far stranger picture. If you zoom in to the atomic…