Thursday, May 21, 2015

What Is Really "Real" In Quantum Physics

This is an excellent article from this week's Nature. It gives you a summary of some of the outstanding issues in Quantum Physics that are actively being looked into. Many of these things are fundamental questions of the interpretation of quantum physics, and it is being done not simply via a philosophical discussion, but via experimental investigation. I do not know how long this article will be available to the public, so read it now quickly.

One of the best part about this article is that it clearly defines some of the philosophical terminologies in term of how they are perceived in physics. You get to understand the meanings of "psi-epistemic models" and "psi-ontic models", and the differences between them and how they can be distinguished in experiments.

But this is where the debate gets stuck. Which of quantum theory's many interpretations — if any — is correct? That is a tough question to answer experimentally, because the differences between the models are subtle: to be viable, they have to predict essentially the same quantum phenomena as the very successful Copenhagen interpretation. Andrew White, a physicist at the University of Queensland, says that for most of his 20-year career in quantum technologies “the problem was like a giant smooth mountain with no footholds, no way to attack it”.

That changed in 2011, with the publication of a theorem about quantum measurements that seemed to rule out the wavefunction-as-ignorance models. On closer inspection, however, the theorem turned out to leave enough wiggle room for them to survive. Nonetheless, it inspired physicists to think seriously about ways to settle the debate by actually testing the reality of the wavefunction. Maroney had already devised an experiment that should work in principle, and he and others soon found ways to make it work in practice. The experiment was carried out last year by Fedrizzi, White and others.
There is even a discussion on devising a test for Pilot wave model after the astounding demonstration of the concept using simple classical wave experiment.


No comments: