Tuesday c
January 31, 2006
news@micbigandaily.com

SCIENCE

5

. . . ......... .

CLASSICAL CHIP

Quantum chip
* could revolutionize
information processing

GRAPHIC BY GERVIS MENZIES

University researchers have constructed a
microscopic chip with macroscopic potential

By Chad Brenner
For the Daily
One small step for computer designers, one micro-
scopic leap for computer design. University researchers
have developed a chip that uses quantum mechanics,
that can process information faster than classical com-
puters.
Physics Prof. Christopher Monroe and a team that
included physics graduate student Daniel Stick, pub-
lished a paper in Nature Physics demonstrating proof
of principle for the fabrication of advanced computers.
Monroe's research relies on manipulating properties of
the atom to enhance traditional computer chips. Quan-
tum chips, which are capable of processing informa-
tion faster than classical chips, could propel computer
design to the next level.
The researchers have found a way to augment micro-
scopic quantum computer chips - using a unique appli-
cation of existing fabrication techniques. Although
quantum computers are still far from our desktops, the
development may lead to more advances in quantum
physics.
In the past, Monroe and his colleagues have been
able to trap ions or isolate ions from the immediate
environment - making them "hover" - using indi-
vidually tuned and controlled electrodes to keep the
ion stable.
Prior to publication of this paper, no one had figured
out how to incorporate a large number of ion traps. into
a single chip or miniaturized electronic circuit. "Previ-
ous chips would have only four or five trap zones, but

over 1000 trap zones are needed for quan'tum applica-
tions," Stick said.
The group found a way to use an existing fabrication
technique called photo lithography to build chips with
these ion traps on board.
This finding is important because, "making one ion
trap in this fashion, implies with existing manufactur-
ing technologies, that the design can be scaled up to
include several more traps," Stick said.
Quantum computers, therefore will store informa-
tion in a unique way. Individual atoms can store quan-
tum bits of information called qubits. Each qubit can
hold the number 1 or 0, or even both I and 0 simultane-
ously, Stick said. Conventional computer chips store Is
and Os individually.
Why does it work this way?
"It's just a strange fact of quantum mechanics," Stick
said.
According to quantum theory, the orbit of an elec-
tron around a nucleus is based on the energy of the
electron. Changing orbits is a very specific process.
Imagine that you want to cross a river which has a
stone path across it. You must jump from one stone
to the next stone in order to cross the river. However,
jumping costs energy - spend too much energy and
you will jump past the next stone. Spend too little ener-
gy and you will fall short.
The quantum catch is that the distance between each
stone is increasing with a known rate. In order for an
electron to become excited, or jump from a low ener-
gy state to a high energy state, it must receive exactly
the right amount of energy, just like a person crossing

the river. If the electron receives the wrong amount
of energy, it will miss its jump and go back to its pre-
jump position.
Lasers emit light that is of energy equal to these spe-
cific quantum transitions - the jumps - can be used
to send signals to the ions.
Because each quantum transition occurs at a specific
energy, lasers can be tuned to target different transi-
tions, thus allowing multiple inputs. Similar quantum
properties can then be exploited to cause ions to emit
photons, which can then be recorded by a sensitive
camera.
Because the idea behind quantum computing is to
take an electrically active ion and physically isolate
it from the rest of the system, it is absolutely essential
that ions are trapped. Stick employed the ion-trapping
technique, which uses electromagnetic waves to sus-
pend a single ion in free space.
Monroe said that though it is simple in principle to add
more atoms, "it turns out to be terribly difficult to have
complete control of even just a few isolated atoms."
"Although we know exactly what to do to scale this
to a more interesting size, it will take a great deal of
technical firepower, mostly in the area of lasers, to
achieve this," he said.
In the process of photo lithography, the technique
used to construct the chips, patterns are etched into
a thin skin of semiconductor material called a wafer.
Usually, wafers are composed of silicon. However,
Stick said the ion trap chips use gallium arsenide - a
compound used for cell phones - because it is a more
efficient conductor than silicon.

Basically, gallium arsenide can function at 250 GHz,
a much faster rate than silicon. Traditionally, silicon
was preferred over the faster gallium arsenide because
silicon is cheaper and more versatile due to its higher
strength.
Although programming multiple inputs to work in
harmony may be difficult, Stick said scientists know
how to program a quantum computer composed of
trapped ions. Monroe was able to solve the problem of
trapping a single ion. The next step for scientists is to
trap multiple ions,
For now, the computer industry is staying away from
this type of research, at least "until they see a market
for it," Monroe said. Unfortunately, quantum comput-
ers are still decades away. Monroe said that someday it
may turn into an arms race, in which case, the quantum
field will benefit because it will be driven by indus-
try.
"Quantum mechanics is so bizarre that it will always
be a fascinating research topic," Monroe said.
"Quantum mechanics allows things like atoms and
molecules to be in two places at the same time. It
allows us to 'teleport' simple quantum particles from
one place to another without any physical contact. Now
that's cool."
Monroe added that the future for this research could
hold revolutionary results.
"Einstein never truly believed in quantum physics,
so maybe, someday we will find that he was right and
it breaks down at some level," Monroe said, "I wouldn't
count on it, but this could be much more interesting
than a quantum computer!"

Scientists develop
domestic robot

Researchers use website
to track spread of disease

New machine capable
of retrieving objects and
performing simple tasks
TOKYO (AP) - Though his move-
ment is a bit stiff, slow and voice monoto-
nous, he willingly turns on the television
with a chest-mounted remote control
and brings a can of drink for you. Within
years, a humanoid robot HRP-2 - cur-
rently under development by a Japanese
national technology institute - could be
a little domestic helper.
The robots - named Promet - are
being developed by the National Insti-
tute of Advanced Industrial Science
and Technology, and can run errands.
They are designed to respond to verbal
instructions and are capable of capturing

robotic voice saying, "What can I do
for you?" Asked to turn on the TV,
Promet repeats the instructions, "I
will turn on the TV" before he exe-
cutes the command.
When Hara asks for a bottle of juice,
the two demonstrate a more advanced
task, one relays the instruction to the
other, saying "Please take care of this."
The second robot huddles to a refrig-
erator, stands in front of it for a while,
saying "Confirming the location of the
refrigerator." Then he says "Searching for
the juice," slowly opens the door with a
right hand, grabs a bottle of drink with
his left hand, shuts the fridge, then walks
back to him, squats down at the table and'
carefully places it on the coffee table.
"Thank you!" Hara says.
Hara said the robots can make most

Popular website
"Where's George.com.
presents scientists with a
model for spread of disease
LOS ANGELES (AP) - By fol-
lowing the money, scientists are
hoping they might better predict
how diseases like a global flu epi-
demic could spread.
Using the popular "Where's
George?" website that tracks U.S. dol-
lars, researchers developed a math-
ematical tool that could help chart the
path of an infectious disease.
"We are optimistic that this will
drastically improve predictions about
the geographical spread of epidem-
ics," said Theo Geisel of the Max

to catch. But experts have warned
that if it ultimately begins spreading
among people, travelers are the most
likely way it will become a world-
wide threat.
Tracking travelers is difficult, so
researchers came up with the idea of
studying them indirectly by tracing how
money circulates through the economy.
In the study, scientists traced the
whereabouts of nearly half a million
dollar bills on www.wheresgeorge.
com bill-tracking site.
Users register their money and then
spend it. They can monitor the money's
movement online as it changes hands.
Researchers found that most of the
money (57 percent) traveled between
30 miles and 500 miles over about
nine months in the United States..
About a quarter of the bills moved

x x.x. ...... .::
c:.< a_