Evanescent propagation modes of microwave photons across a dual-prism gap do not undergo phase shift and represent a case of quantum tunneling where the photons traverse the gap in zero time. Read the original paper here, and the article in New Scientist here.
Note: The author of the New Scientist article mis-transcribed the units from the original piece. Whilst reading the New Scientist article, substitute 'mm' where the author writes 'cm'.