Quantum Mechanics and a Test of Realism

16reality3684 Joshua Roebke in Seed:

In may of 2004 Markus Aspelmeyer met Anthony Leggett during a conference at the Outing Lodge in Minnesota. Leggett, who had won the Nobel Prize the year before, approached Aspelmeyer, who had recently become a research assistant to Zeilinger, about testing an idea he first had almost 30 years before.

In 1976 Leggett left Sussex on teaching exchange to the University of Science and Technology in Kumasi, the second largest city in Ghana. For the first time in many years, he had free time to really think, but the university’s library was woefully out of date. Leggett decided to work on an idea that didn’t require literature because few had thought about it since David Bohm: nonlocal hidden variables theories. He found a result, filed the paper in a drawer, and didn’t think about it again until the early 2000s.

Leggett doesn’t believe quantum mechanics is correct, and there are few places for a person of such disbelief to now turn. But Leggett decided to find out what believing in quantum mechanics might require. He worked out what would happen if one took the idea of nonlocality in quantum mechanics seriously, by allowing for just about any possible outside influences on a detector set to register polarizations of light. Any unknown event might change what is measured. The only assumption Leggett made was that a natural form of realism hold true; photons should have measurable polarizations that exist before they are measured. With this he laboriously derived a new set of hidden variables theorems and inequalities as Bell once had. But whereas Bell’s work could not distinguish between realism and locality, Leggett’s did. The two could be tested.