Physicists at the National
Institute of Standards and Technology (NIST) have built and tested a device
for trapping electrically charged atoms (ions) that potentially could process
dozens of ions at once with the most versatile control of any trap demonstrated
to date. The novel design is a first attempt to systematically scale up from
traps that hold a few ions in a few locations to large trap arrays that can
process many ions simultaneously, with the ultimate goal of building a practical
quantum computer.
Photograph of NIST racetrack ion trap under development as possible hardware for a future quantum computer. The 150 zones for storing, transporting and probing ions (electrically charged atoms) are located in the center ring structure and the six channels radiating out from its edges. Credit: J. Amini/NIST
If they can be built, quantum computers would rely on the curious rules of
quantum mechanics to solve certain currently intractable problems, such as breaking
today’s most widely used data encryption codes. The same NIST research
group has previously demonstrated various components and operations of a potential
quantum computer using ions as quantum bits (qubits). The trap structure is
only one component, analogous to the wiring in today’s computers. Lasers
are also needed to control and use the quantum data, as transistors do for classical
bits today.
Made of a quartz wafer coated with gold in an oval shape roughly 2 by 4 millimeters,
NIST’s “racetrack” ion trap features 150 work zones where
qubits—ions encoding 1s and 0s in their “spins”—could
be stored and transported using electric fields and manipulated with laser beams
for information processing. The trap theoretically could be scaled up to a much
larger number of zones and mass fabricated in a variety of materials. Preliminary
testing of the trap, including loading of 10 magnesium ions at once and transport
of an ion through a junction between channels, is described in a new paper.*
Geometry is a key feature of the new trap design. This is the first demonstration
of ion transport through a junction in a trap where all electrodes are located
on one flat surface, a more scalable design than the multilayer ion traps originally
developed. The various electrodes are used to position and move the ions. At
least three adjacent electrodes are needed to hold an ion in a dedicated energy
“well.” This well and the ion can then be moved around to different
locations by applying voltages to several other electrodes. The modular design
would allow the addition of extra rings, which could significantly increase
capabilities, according to Jason Amini, who designed the trap while a NIST postdoctoral
researcher and is now at the Georgia Tech Quantum Institute in Atlanta.
“The trap design demonstrates the use of a basic component library that
can be quickly assembled to form structures optimized for a particular experiment,”
Amini says. “We can imagine rapid development of traps tailored to individual
experiments.”
NIST scientists are continuing development of the racetrack ion trap as well
as other designs. The new work was funded in part by the Intelligence Advanced
Research Projects Activity and the Office of Naval Research. Four of the 10
authors of the new paper were postdoctoral or guest researchers at NIST at the
time of the research and are currently affiliated with the Georgia Tech Quantum
Institute, Atlanta, Ga.; Council for Scientific and Industrial Research, Pretoria,
South Africa; Centre for Quantum Technologies, National University of Singapore;
and Institut Neel-CNRS, Grenoble, France.
* J.M. Amini, H. Uys, J.H. Wesenberg, S. Seidelin, J. Britton, J.J. Bollinger,
D. Leibfried, C. Ospelkaus, A.P. VanDevender and D.J. Wineland. Toward scalable
ion traps for quantum information processing. New Journal of Physics. March
16, 2010.