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Single Atom Trapping |
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The purpose of this experiment is to trap and manipulate individual Rb87 atoms. Our first step was to make a single atom MOT, using a high magnetic field gradient (about 350 Gauss/cm) and extremely low Rb vapor pressure. We detected the atoms with an EMCCD camera, and were able to see discrete steps in the light radiated from the MOT, indicating the arrival and departure of single atoms.
Above: MOT flourescence versus time showing single atom jumps.
Below: Pictures of MOT with zero, one, two, three, and four atoms
respectively.
Next, we set up an optical lattice intersecting the MOT, and attempted
to transfer a single atom into the optical lattice. With some practice,
we were able to attain transfer efficiency above 75%. Around the same
time, we began attempting continuous observation of the atoms in the
lattice. That means we keep the MOT light shining on the atoms in the
lattice continually, so we can take a series of pictures. This requires
extremely well balanced MOT beams, such that the atoms are not knocked
out of the lattice, but it makes observation and measurement much
faster and easier. We have observed continuous observation lifetimes
higher than two minutes.
Atoms in an optical lattice.
One thing we discovered using continuous observation is that if we
simply load a whole cloud of atoms into the lattice and then wait a
while, eventually most of the atoms will escape, leaving discernable
single atoms. Furthermore, if we make a sufficiently weak MOT, we can
load individual atoms directly into the lattice on an observable time
scale (on the order of one atom per second).
Strings of single atoms in an optical lattice.
Most recently, we added a second lattice to our experiment, parallel to
the first one, with the two lattices separated by about 30 microns. We
see this as a first step toward two dimensional control of the atoms,
and also toward deterministic interactions between trapped atoms.
Strings of single atoms in a dual lattice.
Our current goals include lowering the noise in the system, greater
control over precisely where single atoms load into the lattice, and
possibly progress toward entangling two atoms.
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Michael Gibbons
gte093n -at- prism.gatech.edu
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Peyman Ahmadi
pahmadi3 -at- mail.gatech.edu
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