Uncertainty and non-locality combine to limit spooky action at a distance!


Big news in Quantum Physics today. Or at least it is to me. As I’ve pointed out here before, there’s a fundamental question that we can’t yet answer about how the Universe decides when to play Physics according to the classical or the quantum mechanical rule books. At small scales, it’s the quantum rules. At large scales, it’s the classical ones. But why? And what about the regions of transition?

A new paper published today in Science (which tells you this is a very important and carefully vetted idea) says that the solution comes by no longer seeing non-locality (which is what underlays the kookiness of entanglement) and uncertainty (which explains the fuzziness of reality) as being separate, discrete quantum phenomenon.

As the report of the breakthrough on Physics.org explains:

“One of the weird aspects of quantum theory is that it is impossible to know certain things, such as a particle’s momentum and position, simultaneously. Knowledge of one of these properties affects the accuracy with which you can learn the other. This is known as the ‘Heisenberg Uncertainty Principle’.

Another weird aspect is the quantum phenomenon of non-locality, which arises from the better-known phenomenon of entanglement. When two quantum particles are entangled, they can perform actions that look as if they are coordinated with each other in ways that defy classical intuition about physically separated particles.

Previously, researchers have treated non-locality and uncertainty as two separate phenomena. Now Wehner and Oppenheim have shown that they are intricately linked. What’s more, they show that this link is quantitative and have found an equation which shows that the ‘amount’ of non-locality is determined by the uncertainty principle.

‘It’s a surprising and perhaps ironic twist,’ said Oppenheim, a Royal Society University Research Fellow from the Department of Applied Mathematics & Theoretical Physics at the University of Cambridge. Einstein and his co-workers discovered non-locality while searching for a way to undermine the uncertainty principle. ‘Now the uncertainty principle appears to be biting back.'”

Read the full article here.

In otherwords, by linking non-locality to uncertainty, you automatically get a boundedness on the range of non-locality. Entanglement does work, but not at very large macroscopic distances – which protects the Universe from ansible style devices (and sub-space radios I guess).

According to the authors of the paper published today, this is only the first fruits of recognizing the need to fold both uncertainty and non-locality into one inter-related phenomenon and not too separate ones.

Plus, in hindsight, this is one of the great breakthroughs that makes you go “duh” when you read about it. It’s so obvious.

But science is like that.

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Episcopal bishop, dad, astronomer, erstwhile dancer...