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Comment by hatsunearu | Hacker News Reader

>The 3-microsecond long pulse of light would normally take only 0.2 nanoseconds to pass through the chamber in a vacuum. But when passed through the specially prepared chamber, light emerged 62 nanoseconds earlier than it would have had it passed through the chamber in a vacuum.

Am I stupid or does this not make sense to anyone else

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This explains anomalous dispersion a bit better: http://www.astro.ucla.edu/~wright/anomalous-dispersion.html

Nice explanation. But if "it is still correct to say that information cannot be transmitted faster than the vacuum speed of light" what are some possible use cases of this affect?

Maybe this helps. From the Nature article abstract:

"in practice, this means that a light pulse propagating through the atomic vapour cell appears at the exit side so much earlier than if it had propagated the same distance in a vacuum that the peak of the pulse appears to leave the cell before entering it. "

You have to admit though, it would be very impressive if it made it through the tube in -61.8 nanoseconds.

That’s actually what it did though!

Something was definitely lost in translation.

My guess is that for some definition of "emerged", the three microsecond-long (3000 ns-long) pulse emerged 62 ns early.

Most of the results like this involve some sort of anomalous dispersion and careful definition of the term "emerge". Relevant keywords you're looking for if you delve into the work are "group velocity" and "phase velocity".

TL;DR: Details. They'll matter in this case.

Like, is this just pulse compression due to nonlinear wave effects? If so, it's quite yawn (but it did win a Nobel prize recently so...)

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