Ph.D. Thesis - Physics

allows us to upper-bound the amount of material deposited at one monolayer, as this amount
or more would electrically short the trap electrodes and radically alter the pseudopotential.
However, the stray fields created by ablation do seem to be on the same order of magnitude
as those from electron impact loading (although not at the extreme level seen above with
San Quentin). In principle, it should be possible to reduce the amount of charging caused
by ablation loading by using ion optics to remove the electrons from from the ablation
plume and focus the ions. Alternatively, the approach in Ref. [HGH + 07] could be followed,
requiring a photoionization laser.
6.6 Conclusions
In this chapter, we have presented the design and testing of printed circuit board ion traps,
loaded using both electron impact ionization and ablation loading. We have found that by
almost any measure (except cost) the ablation method is to be preferred. However, neither
is better for our specific purposes than photoionization loading, and thus we will return to
that method in the next chapter.
We also have seen that the stray fields near PCB ion traps can be quite large, up to
ten times larger than those that normally exist in 3-D linear ion traps. Fortunately, the
buffer gas technique enabled us to load and characterize the San Quentin trap even in
the presence of such fields. We found that the e-gun loading method renders the trap
particularly susceptible to the accumulation of stray charge.
The traps presented here were surface-electrode versions of linear ion traps, which have
application most especially to digital-type quantum simulations. Such traps could form a
basis for the CCD-style architectures, which were briefly discussed in Ch. 1. However, if ions
are meant to be kept in static positions, or interlinked by photons or electrical currents,
it is not strictly necessary for the trap to have this structure. For instance, the trap in
Ch. 5 was specifically designed to have a set of ions in a fixed configuration in space. A
surface-electrode analogue of the lattice trap of Ch. 5 could in fact be made from PCB
technology.
We conclude both that PCB ion traps are suitable for the rapid development of ion trap
designs, and that photoionization loading is preferable, as compared to electron impact
or ablation, for the investigation of trap designs for analog quantum simulation. These
conclusions may be applied to the design, construction, and evaluation of ion trap designs
for quantum simulation, a task that is described in Ch. 7.
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