Structured photons slow down in a vacuum

The claim has been made that scientists have figured out how to make photons in a vacuum travel a tiny little bit slower than the accepted speed of light in a vacuum…

The researchers created a source that emitted pairs of photons simultaneously. One of the photons went straight to a highly precise photon counter, while the other went via two liquid-crystal masks, which imparted their profile onto the passing particle of light.

Across a propagation distance of 1 m, the team found that the spatially structured photon lagged behind its partner by between 10 and 20 wavelengths. That equated to a drop in speed of about 0.001%…

As described, this sounds insufficient to me. I can see a number of reasons why they’d see a slight lag across a 1 meter gap, not least being that the photons simply rattled around a little bit in the apparatus before going on their way. The real test would be to test the lag time over *numerous* distances… 1 meter, 2 meters, five, ten. If the lag time is the same, then the speed of light is unchanged, there was just a slight delay at the beginning; if the lag time expands as the distance expands… then, yup, you’ve got yourself light that travels slower than light.

And that would be kinda… disturbing.