[Coco] OT: That ten terabit device is already obsolete....

[Bootstrap Bill]

Just One Electron Spin Control Makes a Huge Step to Quantum Computing


July 21, 2004
Quantum computing, which holds the promise of nearly unlimited processing
power, secure communications and the ability to decode encrypted
conversations by terrorists and others, is a significant step closer to
becoming a reality today with new research published by a team of UCLA
scientists in the journal Nature.

The UCLA team succeeded in flipping a single electron spin upside down in an
ordinary commercial transistor chip, and detected that the current changes
when the electron flips. Their report of controlling and detecting a single
electron's spin is published in the July 22 issue of Nature.

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Scientists had manipulated millions of electron spins in a transistor before
"We have gone from millions to just one," said Hong Wen Jiang, a UCLA
professor of physics and member of the California NanoSystems Institute, in
whose laboratory the experiments were conducted.

"Our research demonstrates that an ordinary transistor, the kind used in a
desktop PC or cell phone, can be adapted for practical quantum computing,"
Jiang said. The research makes quantum computing closer and more practical,
he added.

A single electron spin represents a quantum bit, the fundamental building
block of a quantum computer.

Many scientists believe that an exotic new technology would be required for
quantum computing. However, Jiang said, "I would not be surprised one day to
see a quantum computer built, based almost entirely on silicon technology."

"We have measured a single electron spin in an ordinary transistor; this
means that conventional silicon technology is adaptable enough, and powerful
enough, to accommodate the future electronic requirements of new
technologies like quantum computing, which will depend on spin," said Eli
Yablonovitch, UCLA professor of electrical engineering, director of UCLA's
Center for Nanoscience Innovation for Defense, member of the California
NanoSystems Institute and co-author of the Nature paper.

"We've done this with a commercial silicon integrated circuit chip,
literally off a shelf," Yablonovitch said. "Silicon is the dominant
technology of our time, and will remain so for some time. For those who
think silicon has too many limitations, silicon technology is surprisingly
adaptable, enough so to meet the futuristic requirements of the 21st century
In the electronics of the 21st century, we will manipulate single electron
spins - not just the charge of the electron, but the spin of the electron."

When quantum computing becomes a reality, the government may be able to use
it to eavesdrop on terrorists and quickly break sophisticated secret codes,
Yablonovitch said. Quantum computing will use quantum physics to communicate
much more securely; if someone tries to intercept a quantum message, the
information would be destroyed, Jiang said. Perhaps future elections will be
held using secure quantum voting.

"We've manipulated one spin," Yablonovitch said. "A year from now,
manipulating a single spin might be all in a day's work, and in 10 years,
perhaps it will have a commercial role."

If manipulating a single electron's spin will soon seem routine, until now
it has been anything but. Jiang and his UCLA graduate student Ming Xiao
worked day and night to achieve this goal, and thought about quitting more
than once.

"There were so many unknowns," Jiang said, "but our initial theoretical
calculations were very favorable, and gave us confidence to persevere."

While flipping a single electron was difficult, detecting that they had
actually done so proved even harder.

"We couldn't tell whether it was flipping," Jiang said. "It was like looking
for a needle in a haystack."

Making the detection was like searching an enormous basket filled with
thousands of balls, all the same color, and trying to find the one that is
just slightly different in size. (The detected electron spin has a slightly
different frequency from the others.)

Jiang and Xiao succeeded in working with the transistor at low temperatures:
minus more than 400 degrees Fahrenheit. Jiang and Yablonovitch have ideas
for operating in the future at room temperature, which would be much more
practical commercially.

Jiang and Xiao's method for controlling the electron was to shine a
microwave radio frequency to flip the spin of the electron. The experiments
last but a fraction of a second, but required years of work to reach this
point.

Electrons rotate like spinning tops. The UCLA team can target a single
electron and control when it is right side up and when it is upside down by
changing the microwave frequency.

Two other research groups, one from IBM and one from the Netherlands, also
are reporting the detection of a single electron spin. The groups used
different methods to measure a single electron spin.

How powerful can quantum computing be?

"With 100 transistors, each containing one of these electrons, you could
have the implicit information storage that corresponds to all of the hard
disks made in the world this year, multiplied by the number of years the
universe has been around," Yablonovitch said. "And why stop with 100
transistors?"

A next step is to demonstrate the "entanglement" of two spins, where the
orientation of one electron determines the orientation of the other - a
puzzle identified by Albert Einstein.

The research, a combination of physics and engineering, was funded by the
United States Defense Advanced Research Projects Agency, the United States
Defense MicroElectronics Activity and the Center for Nanoscience Innovation
for Defense.

Ivar Martin, a theoretical physicist at Los Alamos National Laboratory, is a
co-author on the Nature paper.

In the late 1990s, Yablonovitch formed a team of physicists, engineers,
materials scientists and mathematicians to create an electronic device that
could some day be used for quantum information processing.

"The collaboration with Eli has been my best experience at UCLA," Jiang said
"This is an exciting time for nanoscience and technology."

Jiang often monitors experiments from home in the middle of the night.

"It's so exciting," he said, "I don't want to wait until morning to know the
outcome of the experiments."

Source: University of California - Los Angeles


-- 
Bill Cousert
bill at cousert.com
www.cousert.com


"It's easy enough to be pleasant, when life hums along like a song.
But the man worth while is the man who can smile when
everything goes dead wrong.".