talk outline
what is a Ryd atom?
interactions
mu = dipole moment operator for a given atom with other states
the muA*muB notation is really a tensor product of operators
A, B are atom labels
muA is the dipole moment operator between the state of atom A with another atomic state close by in energy
excitation blockade
interactions detune from resonance w laser
diagram labels: state of system, w 0, 1, or 2 collective Ryd excitations
obviously the interaction strength depends on separation distance, so that leads the effect that "you can't excite two Rydberg atoms right next to each other"
however, if they're sufficiently far away from each other, you can do it
bubbles
that idea is depicted here, with the blockaded region is represented by a "bubble"
bubble size: Reinhard2007 p7
interaction strength equals laser linewidth * hbar
useful for giving a hand-wavy interpretation of many blockade experiments
Experiments
so now I'm going to talk about some previous experiments which studied various aspects of the excitation blockade
commonalities: ...
Tong, ... , Gould (2004)
n=30 behaves as "isolated atom", due to relatively weak vdW interactions
can view it in terms of the "bubble" picture
given an interaction strength, there is a certain "bubble" volume
as you increase in laser power, the probability of an excitation within a given region increases
however, there is an upper limit: you can't have more excitations than the total volume of your excitation region divided by the "bubble" volume
at some point, then, you begin to have high enough probabilities that you near this number of excitations, and then marginal excitation is suppressed everywhere due to interactions
so then the plot of "number of excited Ryd atoms" vs "laser irradiance" rolls off.
Tip expt
big beam, focused beam
*mention that now the beam we used is focused down to 10um, to be comparable in size to the blockade radius
otherwise lots of thickness would project onto same plane and wash out our signal
Project Milestones
see ions -- saw those in prev slide, using PDL. now using CW blue.
Electrode wiring
this wiring of electrodes gives control of electric field independently in all three dimensions
each color gives control over an axis (except for red & green, at bottom, which are grounded)
Stark Maps
the differences between how these Stark maps look can be explained by:
geometry of the electrode package
geometry of guide walls
--somewhat interesting
X-map -- ions run into guide walls at large applied voltages
atomic phys
fine structure splitting -- initial splitting
then add Stark effect perturbation
quadratic, bc zero-field states have no intrinsic dipole moment
turnaround of uppermost D stark state
around here, perturbations of fine structure and Stark are ~ equal (I think)
then Stark effect takes over, and there is a linear Stark effect like what is predicted by the parabolic wavefn solution for H in E-field
Autocorrelation
a few methods of analyzing:
vertical integration:
easy, not great, but should sort-of work
beam diameter is approximately the blockade radius, so there shouldn't be any transverse structure that I'm washing out
should only be one Ryd atom in this dimension anyway
slice through the middle:
better, perhaps, but possibly more noisy bc less averaging
background subtraction -- done in last figure
background would be the central feature, plus the large slope that is due to beam geometry
one possibility: take average of pictures, and autocorrelation of that
avg of pics -- washes out internal picture structure, gives beam structure
autocorr of avg -- generates central peak feature
hand-tuned weighting factor for background subtraction
this method is still in the development stage
is what I'm working on now (as well as some other computer programs)