# Question about harmonic poential trap

Hi there,
I am reading something about the bose-einstein condensate, in this material http://www.physics.ox.ac.uk/qubit/fetch.asp?url=groupwebsite/papers/paper103.pdf [Broken], it states something called harmonic trap. I read other introduction materials on bose-einstein condensate, it said that to create that condensate, applying the so-called magneto-optical trap and the a far-off resonant trap and evaporation. But after we get the condensate, all those trap are removed. So what is that harmonic trap actually? When is it applied and why we need that? Thanks.

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BruceW
Homework Helper
I am not so familiar with this kind of stuff. But I think that usually, you must keep the condensate in the trap. Otherwise, the condensate would interact with the environment, which would destroy the condensate.

Hi, I found some graphs on the last several pages of your link, which may provide some insight?
From what I know, a harmonic trap is basically a lattice of waves which are aligned and tuned to provide "nodes" between the waves for atoms to tend to settle into. I am not very familiar with this content yet, either, but I also remember this being used in conjunction with laser cooling if that helps.

Thanks all. Following some comments here, I am trying to search the related topic on the lattice of waves on bose-einstein condenstate, it seems that they use the standing wave to produce that lattice, is that why they call it harmonic? By the way, what confusing me is why they call it trap then? From some material I saw, the atom is freely moving in the lattice so I don't understand why it is trapped?

Harmonic I believe they use as refers to the frequency of the atoms in the configuration you would like to achieve, basically making little divots for what you want the arrangement to be, which isn't enough by itself. Then you get into laser cooling which is simply looking at the direction any of the atoms can go, if they are moving towards lasers from all direction the one ray it is moving towards is more likely to slow it down than any other could keep it going, because the opposite ray it is moving away from so has less energy doppler-wise.