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Originally posted by kleverone
A Simaliar experiment had beed suscessfully tested before.
Pretty cool stuff!
Originally posted by DragonsDemesne
Does anyone know how this tunneling experiment was different from other similar experiments? We've known about quantum tunneling for quite some time, and only now someone manages to tunnel something faster than light? Was there something special about this case, or was this the first time tunneling speed was measured, or what?
The paper in question has no data at all so; although it asserts that it has measured superluminal velocities, it offers nothing to back that up. It also has very little in the way of experimental detail, so we can't determine with certainty what they are measuring, making it very difficult to evaluate their claims. We'll take as close a look as we can, given these limitations.
So, how are these authors measuring an excessive speed of light? In practical terms, most experiments measure light in terms of what is called the group velocity, which is how fast a pulse propagates along an underlying carrier frequency. This can, in some circumstances, lead to the pulses traveling faster than the speed of light in the medium they're in, but not faster than light in vacuum. Although the setup in the new paper is not entirely clear, they were measuring the arrival time of pulses, which means we're talking about group velocity rather than the actual speed of light.