Researchers from the Joint Quantum Institute (JQI) have conducted an experiment that has been able to speed single photons to what appear to be faster than light speeds. The experiment was conducted  to confirm predictions in quantum-physics that the transfer time of light though complex multilayer materials doesn't depend on the thickness of the material. The study is the first to be published observing a single photon.

The researchers created 80nm thick stacks of 30 dielectric layers. The layers were equivalent to about a quarter of the wavelength of light traveling through them. The individual layers in the stack alternated between high and low refractive index materials that cause light waves to bend by varying amounts. Single photons hitting the boundary of the high and low layers have a chance of passing through or being reflected.

The researchers observed that single photons that completely penetrated the stack passed through in about 12.84 femtoseconds. If the team added an additional single layer of low refractive index material to the stack at the end the photon took an additional 3.52 femtoseconds to pass through the stack.

However, if the team added a single high refractive index layer to the end of the stack the single photons were able to pass through the entire stack in 5.34 femtoseconds. With the photon passing through the stack in 5.34 femtoseconds the photon appears to travel at faster than light speeds.

The researcher warn that the perceived faster than light speed of the single photon is "something of an illusion" because only a small portion of the photons actually make it through the stack and if all the photons that initially hit the stack were recorded the distribution of times would be normal.