M1L1g.txt

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Well, then let me add one last aspect
to my introductory example of optical lattices.
In a sort of fly over, I described
to you what is the physics we encounter when we have
an optical lattice switched on and the atoms move around
or they don't move around.
And both cases they are interesting.
But if you think you have explored everything, well,
then you think hard and say, hey, there's
another angle we can get out of it.
And this is we can take the optical lattice
and simply pulse it on, switch it on and off.
Well, what happens is-- and then it becomes a time
dependent problem.
It becomes something where we can shape and control
the wave function of atoms in a time dependent way.
Let me give you one example, if you start with very cold atoms.
It can be a Bose-Einstein condensate.
And then for a short time, we switch on the lattice.
Afterwards, we observe that we have
still some atoms at 0 momentum.
But now we have atoms, which have
a momentum transfer of plus minus 2h [? back here. ?]
You can understand that-- and this,
again, it simplifies that we want
to look at the physics from different angles.
This can be described that you have a 2 photon
transition from the ground state with 0 momentum
to the ground state with 2 photon recoil.
So you can understand it in the photon picture.
But you can also understand it by seeing
you have some meta waves, which are now exposed
to a periodic potential.
And you simply ask, what happens to waves
in a periodic potential?
Well, that's the same.
What happens to optical waves when they encounter a grating.
And that's the physics of deflection.
So in a nutshell this happens when
we-- this happens when we use a pulse on an optical potential.
And let me finish by telling you that, again, in this situation,
we discover the ambiguity or the two-sidedness
of a lot of things we do in atomic physics.
I mentioned to you that the same experiment, the same experiment
setup, called atoms in optical lattice,
you turn up the lattice.
And you have the world's best atomic clock, atoms
just isolating for each other.
You turn down the lattice, and you
have an interesting condensed metaphysics system.
Let me just show you that the same two-sidedness
of atomic physics precision and pristine control.
And interesting many body physics