He and his coauthors have been publishing papers on this subject since 1992, which involve light beams, prisms, and mirrors.
1994 Nimtz and Horst Aichmann shown an experiment at the laboratories of Hewlett-Packard using microwaves through a straitened passage of a waveguide. Nimtz says that the Frequency modulated (FM) signals transports the 40th symphony of Wolfgang Amadeus Mozart 4.7 times faster than light due to the effect of quantum tunnelling.
In a 2007 paper described an experiment which sent a beam of microwaves towards a pair of prisms. The angle provided for total internal reflection and setting up an evanescent wave. Because the second prism was close to the first prism, some light leaked across that gap. The transmitted and reflected waves arrived at detectors at the same time, despite the transmitted light having also traversed the distance of the gap. This is the basis for the assertion of faster-than-c transmission of information.
However, Chris Lee has stated that there is no new physics involved here, and that the apparent faster-than-c transmission can be explained by carefully considering how the time of arrival is measured (whether the group velocity or some other measure). Unfortunately, Lee missed in his statements two items: (i) The authors did not claim to present a new experiment, but to present a new interpretation of known experiments; (ii) evanescent photons are to be identified with virtual photons which can move any way they please. The experiments thus confirmed theoretical QED-based predictions made 30 years ago. . A recent paper by Herbert Winful points out the errors in Nimtz' interpretation . The article goes on to show that, in reality, far from contradicting special relativity, Nimtz has rather provided a trivial experimental confirmation for it.
Aephraim M. Steinberg
of the University of Toronto
has also stated that Nimtz has not demonstrated causality violation (which would be implied by transmitting information faster than light). Steinberg also uses a classical argument ignoring like Lee the quantum mechanical character of evanescent photons.
The understanding of Nimtz and Stahlhoven is that tunneling is the one and only observed violation of special relativity but that is not a violation of causality: due to the temporal extent of every signal it is impossible to transport information into the past. They say that tunneling can be explained with virtual photons like Richard P. Feynman predicted.