Ph.D. Thesis - Physics

[CBB + 05]. Surface-electrode traps are easier to fabricate than their 3-D counterparts, but
have a lower trap depth. Because there exist methods that are capable of loading traps
with depths on the order of 100 meV, which is considerably less than conventional macro-
scopic ion traps, we have chosen to exploit the simpler fabrication processes required for
surface-electrode traps.
Following Chiaverini’s proposal, a number of surface-electrode traps were demonstrated.
The first such trap came from the Wineland group in a paper by S. Seidelin et al. [SCR + 06].
This trap was made of gold electrodes patterned on quartz. They demonstrated confirma-
tion of the trapping potentials, ion crystallization, and a heating rate of 5000 quanta/s.
This is the world record low for electric field noise in a room-temperature ion trap (scaled
to ion-electrode distance and trap frequency). Heating rates as low as 5 quanta/s were
subsequently demonstrated by Labaziewicz et al. in traps that were cryogenically cooled to
6 K [LGA + 08]. This work built on a previous study from the Monroe group that showed
dramatic suppression of heating rates when trap electrodes were cooled to 150 K [DOS + 06].
Chronologically in between the Seidelin and Labaziewicz papers, our group pioneered
the use of printed circuit boards (PCB’s) for ion trapping. The first publication along these
lines came in 2006, when the Chuang group at M.I.T. (of which the author is a member)
used PCB traps to confine charged macroscopic particles and demonstrate all the basic ion
movement operations in surface-electrode ion traps [PLB + 06]. Although this was a useful
experiment for prototyping multiplexed surface-electrode traps, the experimental conditions
were very different from those for atomic ions. To reiterate a bit from Sec. 5.5, vacuum
is not required, and in fact an ambient air pressure actually increases the stability region
for stable trapping. Also, a stable laser source is not needed, as the laser light scatters
incoherently from the trapped particles.
Our group subsequently demonstrated the first use of PCB traps for trapping atomic
ions. Our work on PCB traps has focused on methods for loading the traps, as well as
confirming basic properties (e.g. motional frequencies) of the traps. With one trap, we
used traditional electron gun loading combined with a helium buffer gas to trap in a PCB
trap, then performed micromotion compensation on a fairly large sample of ions [BCL + 07].
In the second experiment, we used laser ablation to directly load a smaller PCB ion trap
[LCL + 07]. These experiments are the subject of the remainder of this chapter.
6.2 Design and construction of a planar PCB ion trap
The first PCB trap to be loaded with atomic ions, dubbed “San Quentin” by our group,
was designed to be a surface-electrode version of a linear ion trap. A diagram of the
trap electrodes is shown in Fig. 6-2. The trap follows a five-rod design, in which ions are
trapped above a grounded center electrode which has rf electrodes on either side of it that
are separated from it by a gap that is milled out of the PCB substrate. The side electrodes
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