[HN Gopher] Laser pulse travels 300 times faster than light (2002)
       ___________________________________________________________________
        
       Laser pulse travels 300 times faster than light (2002)
        
       Author : nixass
       Score  : 13 points
       Date   : 2021-06-06 22:08 UTC (51 minutes ago)
        
 (HTM) web link (optics.org)
 (TXT) w3m dump (optics.org)
        
       | belter wrote:
       | Paper is 2000 Jul has an Erratum - Published: 21 June 2001
       | 
       | Correction: Gain-assisted superluminal light propagation
       | https://www.nature.com/articles/35082117
       | 
       | and a follow up where authors claim a more detailed explanation
       | of their experiment:
       | 
       | Published 12 April 2001:
       | https://journals.aps.org/pra/abstract/10.1103/PhysRevA.63.05...
        
       | karmakaze wrote:
       | > Einstein's Theory of Relativity still stands, however, because
       | it is still correct to say that information cannot be transmitted
       | faster than the vacuum speed of light," said Dr. Lijun Wang
        
         | ballarak wrote:
         | I feel as though I'm not understanding something. What would
         | stop one from transmitting information using the laser pulse?
        
       | hatsunearu wrote:
       | >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
        
         | layoutIfNeeded wrote:
         | Something was definitely lost in translation.
        
         | ISL wrote:
         | 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.
        
           | hatsunearu wrote:
           | 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...)
        
         | chovybizzass wrote:
         | the lazor arrived in da futures
        
       | whateveryoua381 wrote:
       | https://pubmed.ncbi.nlm.nih.gov/10917523/ The nature paper is
       | probably a better link thank optics.org, this is a few years
       | before the demonstration, however it has the same claim of 300x
       | speed of super-luminal (faster than light) group velocity.
        
       ___________________________________________________________________
       (page generated 2021-06-06 23:00 UTC)