Quantum entanglement is tough to dumb down, but this analogy can help detangle it

The term ‘quantum entanglement’ refers to quantum particles being interdependent even when separated, to put it in exceedingly simple terms. Because this behaviour was so at odds with his understanding of the laws of physics, Albert Einstein called the phenomenon ‘spooky action at a distance’. And because it is so hard to square with our own lived experience, it is often used as one of the foremost examples of ‘quantum weirdness’. In this expansion on a previous Royal Institution presentation, the UK science writer Philip Ball details a metaphor devised in the 1990s by Sandu Popescu, professor of physics at the University of Bristol, and Daniel Rohrlich, a physics researcher and lecturer at Ben-Gurion University of the Negev, to help bring our current best understanding of quantum entanglement into focus. In doing so, Ball also provides an enlightening window into physicists’ evolving understanding of the quantum world throughout the 20th century.