Harvard Physicists Make Light Dance

tetrikphimvin and others clued us to the latest work by Harvard's Lene Vestergaard Hau, being published today in the journal Nature. The NYTimes has a good layman's overview of how Hau's team encoded a light beam in a clump of atoms and later reconstituted it elsewhere. The Harvard Gazette offers additional details, a photo, and video links.

Comments

relativity

[cpearson]

If you slow light down wouldnt that also effect the rate of time that the photon experience.

Vista Help Forum

Re:relativity

[TexVex]

If I understand correctly, light travels more slowly through translucent substances because the photons are being absorbed and re-emitted by the electrons in them. The photons travel at c until they hit an atom's electron shell. The electron absorbs the photon, quantum leaps to a higher energy state, then immediately releases the absorbed energy as another photon and returns to its rest state. That whole process takes time, effectively slowing down a pulse of light. The light is still travelling at c between atoms.

In the experiment being discussed in the article, it sounds like they are stopping the process at the point where the photons have been absorbed by matter, and delaying their being re-emitted for quite a long time (relatively speaking). The light is being stopped, but not by causing photons to travel more slowly than c. It's being stopped by keeping the photons' energy bottled up inside the Bose-Einstein condensate.

Re:relativity

[Anonymous Coward]

Your explaination seemed wrong to me, since wavelengths too long to be absorbed by electrons also slow in a dense medium. From wikipedia:

It is sometimes claimed that light is slowed on its passage through a block of media by being absorbed and re-emitted by the atoms, only travelling at full speed through the vacuum between atoms. This explanation is incorrect and runs into problems if you try to use it to explain the details of refraction beyond the simple slowing of the signal. Classically, considering electromagnetic radiation to be like a wave, the charges of each atom (primarily the electrons) interfere with the electric and magnetic fields of the radiation, slowing its progress. The full quantum-mechanical explanation is essentially the same, but has to cope with the discrete particle nature (see Photons in matter): The E-field creates phonons in the media, and the photons mix with the phonons. The resulting mixture, called a polariton, travels with a speed different from light.

One Bad Joke

[Anonymous Coward]

Harvard Physicists Make Light Dance

Then they slowly loaded their six shooters while chewing on a half burnt cigar and make it dance again. They then told light to leave town or it would be pushing up roses. The Harvard townspeople danced joyously and there was much rejoicing.

So, if you walk next to stopped light...

[ScnGuy]

are you going faster than the speed of light? How does this jibe with relativity?

Re:So, if you walk next to stopped light...

[CaffeineAddict2001]

Relativity is concerned with the speed of light in a vacuum. Anytime light passes through a substance it is slowed down. It's not much different than walking past a cup of water.

Re:So, if you walk next to stopped light...

[exp(pi*sqrt(163))]

If you say "IANAP" in your post it gives you a license to say whatever you like about physics. Here's an example:

IANAP but I think that when virtual particles interact in a magnetic field then in the frame of reference of a photon the wavefunction collapse allows faster than light communication except when in violation of the second law of thermodynamics.

Re:So, if you walk next to stopped light...

[BitterOak]

That's absolutely correct. In fact, it is quite common for particles to travel through a medium faster than light travels through that medium. That is the principle behind how a Cherenkov detector works.

DDR Lights...

[__aaclcg7560]

Stop playing Dance Dance Revolution and get back to work! There's nothing in the research contract about getting physical on the job!

Meanwhile

[roguegramma]

Meanwhile, in Russia, light makes physicists dance.

acid

[chia_monkey]

It's called acid maaaaaan. The lights were dancing, the reds tasted soooo good. Purple had a funky smell to it though...

Re:acid

[spun]

Acid is for wimps. If you really want to see light dance, you want N,N-DMT or 5MeO-DMT. There is also no way to stop it from utterly demolishing your ego, so ego based people should NOT try it.

Re:No Parking on the Dance Floor

[spotlight2k3]

I think that they went a little far when saying that Light was Dancing. More closer would be that they stored a 4 centimeter stream of light and then played it back later. Finally we are gonna have a way to have data storage crystals like in all the scifi movies.

Credit to the Experimenter, Link to the article

[Dr J. keeps the nerd]

Though the Nature newsbrief doesn't mention her, the lead author and the main experimentalist was Naomi Ginsberg, a PhD student in Lene Hau's lab. You can read the article abstract on Nature's website: http://www.nature.com/doifinder/10.1038/nature0549 3 The AFP wire item also gives credit where credit is due: http://www.cosmosmagazine.com/node/1028

Frame of reference

[DAtkins]

Hee hee... that's funny, despite the fact that it's wrong.

Frame of reference is an idea that actually had it's beginnings in Einstein's work. The idea being, can a person determine the absolute velocity of [something]. For example, from the frame of reference of the earth, my car goes 65 miles per hour. From the frame of reference of the sun, my car goes 2.9 km/s (because the earth moves that fast around the sun.

Why is this important? Well, Einstein used this to question why the speed of light seemed constant despite your frame of reference. On a ball of rock orbiting the sun at 2.9 km/s, the speed of light is c. On the surface of the sun (which has no orbital velocity in comparison to the earth), the speed of light is still c. From the frame of reference of the center of the galaxy (where the sun has extremely high relative velocity - which I'm too lazy to look up) the speed of light is still c.

Which means that, either the speed of light somehow knows how fast you are going and adjusts itself (which is, of course, retarded) or there is something about spacetime that makes it seem that way. Hence the general theory of relativity was developed to explain it. (Which, in case you are curious, states that the ruler that you are using lenghtens or shortens depending on your "frame of reference")

So, it's actually quite important.

Re:Is this EPR?

[w33t]

Entaglement is featured in this experiment, but I do not think the photons are being entangled, per se.

The device being used for this experiment is a Magneto Optical Trap. This cool-ass device uses lasers and magnetism to suspend a cloud of ultra-cold atoms in a bonafide Bose-Einstein condensate. This is a state in which all the particles act together as though they were a single, very large, particle. I believe they are entagled - but of course, I Am Not A Physicist.

Apparently the ultra-cold environment of the condensate is the ideal place to slow some photons down, apparently to a stop. It's very cool (pun intended).

Re:relativity as light is just surfing the expandi

[pclminion]

There, fixed it for ya. You were too smug to notice that you put your words into his mouth, and then accused him of making a flawed definition.

If you can define the term "expansion" without referring to temporality, I'll concede.