Sheding Light On More Quantum Weirdness ?

[Old_Geezer]

Changing the shape of a photon ?!?

What will they think of next ? Is nothing impossible ?

http://www.bbc.co.uk/news/uk-scotland-glasgow-west-30944584

When I first saw the story on teletext they emphasised scientists had slowed light down. I thought, Big deal. "That happens every time it leaves the vacuum. I'm sure they've slowed it to below human walking pace by sending it through some cold condensate or other", but it seems this is more permanent.

I had to check it wasn't April the 1st.

[jim360]

It's not a joke -- the paper was first released a couple of months ago, and can be read here.

http://arxiv.org/abs/1411.3987

Essentially what's happen is that they've managed to change the group velocity of a single photon; "group velocity" is always less than or equal to the "normal" speed of a wave, with equality only when the wave's "shape" is similar to a normal sheet of paper, for example.

Not an easy thing to put into words when explaining it, but a remarkable experimental achievement anyway.

[Old_Geezer]

Thanks. I shall endeavour to read more and hope it is explainable to the layman. At present the idea that a single thing can have a group velocity is a little mind blowing; but I'm sure it's just in the interpretation of meaning.

Next time I board a plane I'll pay more attention to my goodbye waves to the family ;-)

[Matheous-2]

I'm fairly sure I saw a similar experiment on video either in a TV documentary
or YouTube clip where the photon was brought to a standstill inside a vacuum tube.
Not quite as impressive as two being 'raced' with one patterned and slowed.