The God Effect

The Strange World of Quantum Entanglement

Could entanglement prove to be the “Holy Grail” for merging scientific and mystical, religious thought?

Brian Clegg received a physics degree from Cambridge University and is the author of numerous books and articles on the history of science. His most recent book is The God Effect : Quantum Entanglement, Science's Strangest Phenomenon.

~~~~~~~~~~~~~~~

What you write in your book about entanglement is so startling, it’s hard to believe. Let’s start with a definition. What is quantum entanglement?

Entanglement is a strange feature of quantum physics, the science of the very small. It’s possible to link together two quantum particles – photons of light or atoms, for example – in a special way that makes them effectively two parts of the same entity. You can then separate them as far as you like, and a change in one is instantly reflected in the other. This odd, faster than light link, is a fundamental aspect of quantum science – Erwin Schrödinger, who came up with the name “entanglement” called it “the characteristic trait of quantum mechanics.” Entanglement is fascinating in its own right, but what makes it really special are dramatic practical applications that have become apparent in the last few years.

Is it possible that entangled particles are not actually in immediate communication, but are simply programmed in to behave the same way? Much like twins separated at birth who live eerily similar lives - assume the same professions, marry similar spouses, etc.

This is an obvious possibility. John Bell, who devised a lot of the theory for testing the existence of entanglement, covered it in a paper called “Bertlmann’s Socks and the Nature of Reality.” Reinhold Bertlmann, a colleague of
Bell

’s, always wore socks of different colors. Bell pointed out that, if you saw one of Bertlmann’s feet coming around the corner of a building and it had a pink sock on, you would instantly know the other sock wasn’t pink, even though you had never seen it. The color difference was programmed in when Bertlmann put his socks on.

But the quantum world is very different. If you take some property of a particle, the equivalent of color, say the spin of an electron, it doesn’t have the value pre-programmed. It has a range of probabilities as to what the answer might be, but until you actually measure it, there is no fixed value. What happens with a pair of entangled electrons is you measure the spin of one. Until that moment, neither of them had a spin with a fixed value. But the instant you take the measurement on one, the other immediately fixes its spin (say to the opposite value). These “quantum socks” were every possible color until you looked at one. Only then did it become pink, and the other instantly took on another color.

You write that Einstein among other scientists could not accept quantum entanglement. It seems to throw out the whole notion of cause and effect. How confident are physicists that quantum entanglement exists and what are the implications for science and the scientific method?