COLUMBUS,
Ohio – Scientists at Ohio State University have taken
a step toward the development of powerful new computers
-- by making tiny holes that contain nothing at all.
The holes -- dark spots in an egg carton-shaped
surface of laser light -- could one day cradle atoms
for quantum
computing .
Worldwide, scientists are racing to develop computers
that exploit the quantum mechanical properties of
atoms, explained Greg
Lafyatis , associate professor of physics
at Ohio State . These so-called quantum computers
could enable much faster computing than is possible
today. One strategy for making quantum computers
involves packaging individual atoms on a chip so
that laser beams can read quantum data.
Lafyatis and doctoral student Katharina
Christandl recently designed a chip with a
top surface of laser light that functions as an
array of tiny traps, each of which could potentially
hold a single atom. The design could enable quantum
data to be read the same way CDs are read today.
They described their work in the journal Physical
Review A .
Other research teams have created similar arrays,
called optical lattices, but those designs present
problems that could make them hard to use in practice.
Other lattices lock atoms into a multi-layered cube
floating in free space. But manipulating atoms in
the center of the cube would be difficult.
The Ohio State lattice has a more practical design,
with a single layer of atoms grounded just above
a glass chip. Each atom could be manipulated directly
with a single laser beam.
The lattice forms where two sets of laser beams
cross inside a thin transparent coating on the chip.
The beams interfere with each other to create a grid
of peaks and valleys -- the egg carton-shaped pattern
of light.
The physicists expected to see that much when they
first modeled their lattice design on computer. But
to their surprise, the simulations showed that each
valley contained a dark spot, a tiny empty sphere
surrounded by electric fields that seemed ideally
suited for trapping single atoms and holding them
in place, Lafyatis said.
In the laboratory, he and Christandl were able to
create an optical lattice of light, though the traps
are too tiny to see with the naked eye. The next
step is to see if the traps actually work as the
model predicts.
“We're pretty sure we can trap atoms -- the first
step towards making a quantum memory chip,” Lafyatis
said. A working computer based on the design is many
years away, though, he cautioned.
In fact, Christandl suspects that they are at least
two years away from being able to isolate one atom
per trap -- the physical arrangement required for
a true quantum memory device.
“Right now, we're just trying to get atoms into
the traps, period,” she said.
So far, they've been able to form about a billion
gaseous rubidium atoms into a pea-sized cloud with
magnetic fields. Now they are working to move that
cloud into position above a chip supporting the optical
lattice.
Theoretically, if they release the atoms above the
chip in just the right way, the atoms will fall into
the traps. They hope to be able to perform that final
test before Christandl graduates in August.
Should they succeed, the payoff is potentially huge.
Both the government and industry are interested
in quantum computing because traditional chips are
expected to reach a kind of technological speed limit
in a decade or so. When that happens, faster, more
powerful computers will require a new kind of hardware.
A “bit” in
normal computer chips can only encode data as one
of two possibilities: either a one or a zero --
the numbers that make up binary code. But if quantum
theorists are correct, quantum bits, or qubits,
will enable more efficient problem solving because
a qubit can simultaneously encode both a zero and
a one. This allows the quantum computer to efficiently
carry out a large number of calculations simultaneously.
“In principle, quantum computers would need only
10,000 qubits to outperform today's state-of-the-art
computers with billions and billions of regular bits,” Lafyatis
said.
Scientists have speculated that qubits could enable
long-distance communication and code breaking. But
Christandl thinks that the technology could serve
an even larger purpose for science in general, by
powering computer simulations.
Quantum mechanics tries to explain how atoms and
molecules behave at a fundamental level, so simulations
of quantum systems could advance research in areas
as diverse as astrophysics, genetics, and materials
science.
“The quantum computer is the ideal tool for those
simulations, because it is a quantum system itself,” Christandl
said.
Coauthors on the paper included Jin-Fa
Lee , associate professor of electrical
engineering , and doctoral student Seung-Cheol
Lee of Ohio
State's ElectroScience Laboratory .
The Research Corporation funded
this work.
Contact: Greg Lafyatis, (614) 292-2286; Lafyatis.2@osu.edu
Katharina Christandl (614) 292-7448; Christandl.1@osu.edu
Written by Pam Frost Gorder, (614) 292-9475; Gorder.1@osu.edu
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