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Trapping Atoms to Observe
Their Interactions
By Barbara Spector
When Michael W. Noel joined
the Bryn Mawr College faculty in fall 2000 as
an assistant professor of physics, his lab was
just an empty room.
As a new faculty member, Noel
needed to order and set up equipment quickly so
he could begin his atomic physics investigations.
He studies unusual properties of atoms in highly
excited (or very high-energy) states — known
as Rydberg atoms. "They’re very interesting
because they have exaggerated properties,"
Noel says. "They interact strongly with an
electromagnetic field and with each other."
His investigations involve exciting the atoms
to weakly bound states, observing their interactions,
and trying to control the ways in which they interact.
Building a Better Atom
Trap
Atoms generally move around
quickly and bounce off each other, making them
difficult to study. Researchers can keep them
still via a device called a magneto-optical trap,
which slows atoms down and holds them near a fixed
location in space using a combination of optical
and magnetic fields.
Building the atom trap involves
assembly and construction of many small instruments.
Noel was aided in this effort by an undergraduate
student, Katharine Claringbould ’01. While
Noel ordered the equipment and supervised set-up,
Claringbould unpacked the instruments and learned
about them as she worked. She assembled the external
cavity diode lasers, designed and built the laser
stabilization circuitry, and aligned the optical
systems. "By the end of the first semester,
she had successfully put together one of these
lasers," says Noel. "It wasn’t
an empty room anymore." By the end of the
second semester, Claringbould and Noel had trapped
atoms.
Mentoring Undergraduate
Researchers
"I
like having undergraduates in the lab," Noel
says. "At Bryn Mawr, the undergraduates are
very motivated. They want to learn the details
of the instrumentation as well as the physics
involved."
In 2001-02, Noel is mentoring
three students. Graduate student Tom Carroll’s
research project involves designing a titanium
sapphire amplifier for use in exciting the Rydberg
states. Undergraduates Anne Goodsell ’02
and Ellen Kruger ’02 are working on characterizing
a magneto-optical trap and constructing a high-power,
external-cavity diode laser, respectively.
"With
the experience the students are acquiring by learning
these techniques and building the apparatuses,"
says Peter Beckmann, chair and professor of physics,
"they could go on to industry — where
laser physics and engineering are in great demand
these days — or academia."
Designer Solids
Noel’s research is connected
to investigations in several other fields, including
low-temperature plasma physics and solid-state
physics. He studies the properties of "designer
solids," produced to have specific properties.
Although the atoms are spaced far apart in these
solids, the couplings are strong because of the
Rydberg atoms’ exaggerated properties.
Noel manipulates the energy
transfer in the "designer solid" by
controlling the atomic sample. "We have the
opportunity to control the nature of the interactions
between atoms as well as the structure of the
solid," he says. "We can make it look
like a glass in one configuration or a crystal
in another." Atoms in a glass are randomly
positioned in space; atoms in a crystal are ordered
in a regular, periodic array.
Cooling the atoms also enables
researchers to study quantum mechanical effects,
which are obscured at higher temperatures when
atoms are interacting. "The atom itself is
a quantum system," Noel explains. "If
we can control the way this quantum system interacts
with its neighbors, we can implement a powerful
type of computing."
Currently, his research is
being funded through start-up funding from the
College; funding agencies are reviewing his grant
proposals.
Noel earned his bachelor’s
degree at Whitworth College in Spokane, Wash.,
in 1988. He received his Ph.D. from the Institute
of Optics at the University of Rochester, where
he did his thesis work on atomic electron wave
packet interference and control. His postdoctoral
research was conducted at the University of Virginia
in the lab of Thomas F. Gallagher. At Virginia,
Noel, who had been working with highly excited
atoms since graduate school, first became exposed
to atom-trapping research. He saw that these studies
were opening up new opportunities.
Teaching and Research
Bryn Mawr combines the best
features of a small college — where faculty
can accommodate interested students who seek them
out — and a research university, Noel says.
He sought to establish his career at an institution
that offered an appropriate balance between teaching
and research. "Teaching at a small college
can be very rewarding," he says. "I
was looking for that type of environment. But
the research environment was also very important
to me."
Noel says his experiences
in the front of the classroom have an energizing
effect on his lab investigations — especially
in a small department, in which every professor
ultimately will teach virtually every course.
Such an environment ensures a fresh approach to
the subject matter, he notes: "I’ll
always be rethinking the material."
Beckmann says Noel’s
wide-ranging experience makes him a valued member
of the physics department. "He brings expertise
and academic maturity," he says. Because
Noel’s research spans several areas of physics,
he is prepared to teach a wide range of subjects
and revamp a number of experiments for undergraduates,
Beckmann notes.
Balancing teaching and research
is challenging, Noel acknowledges. "I pick
and choose on a daily basis to get it all done.
The expectations the College has for me, and the
expectations I have for myself, are very high."
About the Author
Barbara Spector writes on
science and technology as well as business topics.
She is the executive editor of Family Business
magazine and former editor of The Scientist.
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