Ph.D. Thesis - Physics

other techniques, including electron impact ionization and photoionization. We also probe
some other related practical questions, including how the loading efficiency depends upon
the composition of the material that is ablated and upon the ablation laser power, and how
the number of ions loaded depends upon the ablation laser power. We also qualitatively
discuss the buildup of stray electric charge, relative to other loading methods.
Although we present PCB’s here as a step towards development of 2-D arrays, our work
on them chronologically precedes the work on the lattice trap of the previous chapter. The
traps presented in this work are surface-electrode (purely two-dimensional) versions of the
well-known linear ion traps from quantum information research. All the experiments were
done in a room-temperature vacuum vessel, and the basic questions on which we focused
are how ions might be loaded into such a trap, and what effects the loading methods have
on the subsequent trapping potentials. Our work on buffer-gas loading with electron impact
ionization into a PCB ion trap was the first demonstration of a PCB ion trap for atomic ions,
and was presented in Ref. [BCL + 07]. Our work, following this, on laser ablation loading of
PCB ion traps, was published as Ref. [LCL + 07]. Following our work, the use of planar PCB
ion traps has spread around the world, with traps of our design being used in Innsbruck,
Austria, and Osaka, Japan. Additionally, work has been published on the construction of a
3-D segmented linear ion trap from PCB components [HDS + 08], with the goal of creating
an extremely accurate single-ion source.
The chapter is organized as follows: in Sec. 6.1, we discuss the various prior designs and
experiments in surface-electrode ion trapping; in Sec. 6.2, we present the design of our first
surface-electrode trap, along with the experimental setup used to study it; in Sec. 6.3, we
present the buffer gas loading and micromotion compensation techniques for this trap; in
Sec. 6.4, we present the second-generation PCB trap; in Sec. 6.5, we discuss past work in the
loading of ion traps using laser ablation, and then present our results using this technique;
in Sec. 6.6, we summarize and offer an evaluation of the loading methods presented in this
chapter.
6.1 Surface-electrode ion traps: history and theory
The “workhorse” of quantum information experiments with trapped ions has been, for the
past several years, the linear ion trap. As shown in Fig. 6-1, the trap consists of four long
electrodes, on two of which an rf voltage is applied, while the other two are grounded. In
this case, “long” means that the length of the electrodes is large compared to the spacing
between them. This configuration creates a quadrupole potential; near the center of the
trap, this leads to an approximately harmonic time-independent pseudopotential, as dis-
cussed in Ch. 4. Confinement along the trap axis, the ˆz direction, is created by a static
voltage applied to two endcap electrodes.
If the secular frequency in the ˆz direction is small compared to those along ˆx and ˆy,
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