FQxI members Vlatko Vedral and Roger Penrose are among authors of an experiment that has made the first direct measurement of the quantum phase of a freely falling object. The team split ultracold rubidium atoms into two paths, held one still, let the other fall, finding that the phase matched the prediction of Einstein's equivalence principle.
"We have no consistent theory telling us why quantum physics should fail," says Vedral. The result doesn't test Penrose's idea that quantum mechanics breaks down for heavier objects, but the same group is now working on a nanodiamond experiment that could.
