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Prof. Lene Hau: Stopping light cold

November 10, 2019


the speed of light is basically is fast as you ever get What is it in American units, something like one hundred and eighty six thousand miles a second but on our account we can slow them down to 38 miles per hour- that’s what we did in our first experiment and then we actually slowed them down all
the way to to one mile an hour and then you can actually you can basically crawl faster than light what we do is we a bunch of atoms, and we use what I call sodium atoms, exactly what you have in table salt and then we cross-manipulate these atoms in very special ways with laserbeams and then we can cool these atoms down to a few billionths of a degree above absolute So, of course, that’s really cold.
It’s actually the coldest place in the universe. And then once we create a cloud of such really cold atoms we illuminate that cloud with one laser beam and then we send a light pulse into the cloud from the other side and we can now slow that light pulse down to the speed of a bicycle and it sort of chuffs along. And then, if we feel like it, we can actually completely stop that light pulse inside our atom cloud and then leave it there for a while, park it there, and then when we feel like it, cloud send the light pulse back on its way, revive it, regenerate it, and out it comes. what we are seeing here is actually the atom pool, really, because as I mentioned, we create these really cold atoms and we need laser beams to do that. And eventually these laser beams are really running around, criss cross on the optics table. And then they converge on the vacuum chamber where all the action is happening. And then up here, behind, we have a very special atom source- that’s where the sodium atoms are coming from. And they are hot to start- we actually have to heat them to create a gas of sodium atoms… And at the time when we
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started to go after cold atoms I did not have a clue that some years later I would start to look at slow light forces. And that’s really an example of, if you get your hands on an exciting new
system, you start to poke it and see what comes out And what you hope is that something totally unexpected, totally exciting will come out and and i think that’s
what happened in this case.

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