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