DEIXIS 2003 - 2004 THE DOE CSGF ANNUAL
A Calling Realized
By Jacob Berkowitz
In 1997, Mary Ann Leung sold her house,
quit her successful 16-year-long career
as a trainer and instructional designer
in the computer industry and, at age 38,
returned to college to become a physician.
Or so she thought. On her way to the
medical sciences she discovered a
long unrealized passion for math
and the computational sciences.
Now a Department of Energy
Computational Science Graduate
Fellow (DOE CSGF), she is using
high performance computing to
understand the role of quantum
mechanics in applications ranging from
nanoscale engineering to the emerging
field of quantum computing.
Leung found her groove during a
National Science Foundation-sponsored
undergraduate summer stint in the
lab of Dr. William (Bill) Reinhardt,
a University of Washington professor
of chemistry and adjunct professor
of physics.
“I fell in love with the work I
did,” says Leung, now a third-year
doctoral student in Dr. Reinhardt’s
lab at the University of Washington. Her
job that first summer was to develop a
computer program to visualize the
time propagation of solitons in the
Bose-Einstein Condensate (BEC).
While planning a slide presentation
of her work, she came across an
image of a BEC generated by one of
Dr. Reinhardt’s computer programs.
It was a moment of scientific and
personal epiphany.
“The image had a strong likeness to a
piece of artwork that I’d created 20 years
earlier. I decided at that point that I’d
been visualizing math much earlier in
life, but I just hadn’t realized it.
So, seeing this image made me feel like
I’d found my calling,” recalls
Leung.
Ironically, had she returned to school
several years earlier she would never
have seen her calling. In 1924, Albert
Einstein and Satyendra Nath Bose
hypothesized that noninteracting atoms
chilled to supercold temperatures
(about 190 nanoKelvin) would
condense into a new form of gaseous
matter, the BEC. What’s remarkable
about the BEC, they explained, is that
in this supercold state the atoms would
all go into the same quantum state:
They would behave as a single super
atom, a macroscopic quantum object
large enough to be visible to the
naked eye.
However, it wasn’t until 1995
that three independent research teams
were successful in creating the first
BEC by supercooling rubidium-87,
lithium-7, and sodium atoms. This
breakthrough has set off a global
wave of experimental work with BECs.
“They’re a wonderful place for people
to explore the fundamentals of quantum
mechanics because you can see the
quantum effects,” says Leung, noting
that BEC research has applications to
fields ranging from superconductivity
to nonlinear optics.
In the process of her doctoral
work, initially focused on developing
parallelized codes to understand and
visualize the dynamics of solitons and
vortices in BEC, Leung found her
own kind of quantum coherence –
a fellowship program that was just
right for her.
“When I found the DOE CSGF, I
thought: This is perfect for me. I love
all of these things,” recalls Leung.
The Fellowship requires participants
to take science, applied math, and
computer science courses, and
Leung was particularly inspired
by an algorithms course.
But it was the Fellowship practicum
that let her really test her mettle as
an emerging computational scientist.
During a workshop she attended on
the computational tools at DOE’s
Lawrence Berkeley National Lab,
Leung met Dr. Andrew Canning,
a staff scientist in Berkeley Lab’s
Computational Research Division. She
was intrigued by his work: Although
also exploring computational methods
for quantum systems, Dr. Canning
models solid state systems. It’s
a realm that offered a new challenge for
Leung, one that she readily took on when
offered the chance of a three-month
practicum with Dr. Canning.
Leung’s practicum research was part
of an ongoing collaboration between,
among others, Dr. Canning and
Dr. Z.Q. Qiu, a solid state
physicist who holds a joint appointment
with the Lab’s Materials Sciences
Division and the Physics Department of
the University of California at Berkeley.
Dr. Qiu’s group is a world leader in
the creation of very pure, nanoscale
metallic films. These thin metal films
(sometimes only several atoms thick)
are ideal for studying quantum
mechanical effects and are at
the frontier of a new realm of
materials engineering.
“In the past, people have designed
materials to have specific mechanical
properties, such as strength,” says
Dr. Canning. “Now, because we can
engineer at the atomic level, the
idea is to design materials in which
we can control the properties of
individual electrons.”
Using Berkeley Lab’s IBM SP
supercomputer, Leung modeled
Dr. Qiu’s experiments conducted
at the Lab’s Advanced Light Source,
to understand the effect of the
addition of a nanoscale nickel
monolayer on quantum well states
in copper. Quantum well states are
an energy state in which an electron
is sandwiched between two layers of
atoms so that its motion is confined
to a single dimension. They are
thought to be responsible for the
giant magneto resistance effect, the
basis for the creation of very high
density disk drives.
Leung and Canning’s simulations
have already provided a more
detailed physical understanding
of the nickel-copper quantum well
state experimental results, as well as
confirming some of the theoretical
models used by Dr. Qiu’s group.
Leung says that it was great to
work closely with Dr. Canning and
his post-doctoral students in “a
collaborative environment that was
really about pursuing interesting
science.” The experience provided
Leung with a clearer sense of
her potential.
“One of the important lessons that
I learned from that experience was that
you can apply yourself to a new field
and within a relatively short amount
of time, you can learn quite a lot and
make progress,” she says.
It a lesson she’s taken back to her
doctoral research at the University
of Washington. Along with her
supervisor Dr. Reinhardt, Leung is
exploring the potential of the BEC
and high performance computing
for the study of quantum computing.
Dr. Reinhardt stresses that the
work is currently at the very early
stages of creating an original and
challenging PhD research project.
“It’s an exciting, frustrating
and turbulent process,” he says.
But it’s one that Leung has
eagerly grasped.
“My vision is to create a computational
model that will simulate the behavior
of a quantum computer,” says Leung.
“So in my case, computational science
not only means the application of
high performance computing to a
scientific problem, it also includes the
investigation of new computational
techniques using high performance
computing.”
Amidst the enormous international
scientific buzz about quantum
computing, Dr. Reinhardt is
cautiously optimistic that BEC
research offers a unique approach.
“Because BECs are big and you can
control them with lasers, we’re trying
to figure out if we can use these very
special macroscopic properties to
make extra-stable pieces of quantum
computers,” he says, noting that
as a large quantum object the BEC
might be less prone to the quantum
decoherence that disturbs single
atom quantum computing systems.
At the same time as she is working
towards numerically modeling a
quantum computer, Leung is also
helping others push scientific
boundaries. She volunteers
with organizations dedicated to
encouraging girls to study science
and engineering.
“In hindsight, I realize that I
was always really good in math when I
was a kid,” says Leung. “But
I never really received any encouragement
to do anything with math. Quite the
contrary, I was discouraged: ‘That’s
not a girl thing to do’. Since I got
such a late start in science, I really
want to encourage young girls and
women to go into science; it’s a
fascinating field.”
The Krell Institute
http://www.krellinst.org