switch flips atoms
Technology Research News
Atoms and subatomic particles are like
microscopic tops that can spin in one of two directions, up or down. Spintronics
and quantum computing use these spin directions to represent the ones
and zeros of digital information. Today's electronics, in contrast, use
the presence or absence of electric charge to represent binary numbers.
A team of researchers from the Max Planck Institute and the Technical
University of Munich in Germany has used an electronic switch to transfer
the spin of a group of electrons to the nuclei of atoms in a semiconductor.
Information transfer between electrons and atoms is a key component of
spintronics and quantum computing. Atoms in semiconductor crystals are
better suited to preserving spin and thereby storing information than
electrons because they are fixed in position and they are better insulated
from the environment than electrons. Electrons, however, can flow in currents,
which makes them better suited to transmitting information.
Computers based on spintronics would be faster, use less electrical power
and store data more densely than electronic computers. Data would also
remain in memory after the power was turned off, allowing spintronics
computers to start instantly.
Quantum computers can use the interactions of individual particles to
solve certain problems, like cracking secret codes and searching large
databases, that are beyond the abilities of the fastest classical computer
The researchers' experiment proved that it is possible to transfer spin
between atoms and electrons, but a lot of work remains before the capability
can be put to practical use, said Jurgen Smet, a scientist at the Max
Planck Institute. The experiment "brings us one step closer, but we have
a large number of giant leaps to go to make something useful and practical,"
said Smet. "We have succeeded... in a very crude manner for a large ensemble
of nuclei, however under extreme conditions, like nearly absolute zero
temperature and... a large, stationery magnetic field."
Ordinarily, the spins of electrons and atoms in a semiconductor are isolated
from each other. The energy associated with electron spin is considerably
greater than the energy associated with atomic spin, and this energy mismatch
usually keeps the electrons from changing the atomic spin. But by using
a gate, or electronic switch, to control the density of electrons in the
semiconductor, the researchers found that at certain densities the interactions
between electrons affect the spins of the semiconductor's atoms.
Atomic spins can also be flipped using magnetic fields, which is how hard
disk drives in today's computers work. But disk drives are larger, slower
and require more energy than the integrated circuits on computer chips.
"One would like all-electronic nuclear solid-state devices so that one
can marry the benefits of the technology used in present-day electronics
with those of quantum computation or spintronics," said Smet.
The researchers' experiment shows that electronic control of atomic spin
in semiconductors is possible. However, their technique is unlikely to
lead directly to practical technology, said Smet. "The physics we exploit
to flip the nuclear spins actually also requires these low temperatures,
so there is at least no straightforward rule on how to scale this up,"
Still, the research shows that spintronics could be a viable successor
to today's electronics. "Atoms... are the smallest unit of which a semiconductor
crystal is composed. If you were to extrapolate Moore's Law... you'll
find that in the next decade or so we end up with a dimension on the order
of the atom," said Smet. Moore's Law, which has held true for the past
couple of decades, states that computer speeds double every 18 months
as manufacturers shrink computer circuits. "Clearly a paradigm shift has
to occur. That is one reason why long-term researchers fervently think
about ways to explore the spin degree of freedom of the nucleus of atoms,"
Controlling atomic spin could also be used in quantum computing. But to
do so, however, the researchers' technique would need to be applied to
individual atoms. "This kind of control is not something we will manage
to achieve within the next two decades," said Smet.
The researchers device serves as a miniature laboratory for probing the
fundamental interactions between electrons and nuclei and exploring the
basis for exchanging information between the two spin systems, said David
Awschalom, a professor of physics at the University of California at Santa
Barbara. "This is a beautiful experiment," he said. "Many people envision
that future quantum computing will use nuclear spins for information storage,
and thus it is important to explore these basic interactions."
Smet's research colleagues were Rainer Deutschmann, Frank Ertland and
Gerhard Abstreiter of the Technical University of Munich, Werner Wegscheider
of the Technical University of Munich and the University of Regensburg,
and Klaus von Klitzing of the Max Planck Institute. They published their
research in the January 17, 2002 issue of the journal Nature. The research
was funded by the German Ministry of Science and Education (BMBF) and
the German National Science Foundation (DFG).
Timeline: >20 years
TRN Categories: Materials Science and Engineering; Quantum
Story Type: News
Related Elements: Technical paper, "Gate-voltage control
of spin interactions between electrons and nuclei in a semiconductor,"
Nature, January 17, 2002
Tiny wires turn
chips inside out
share the load
Nanotubes take tiny
envisions DNA origami
Electric switch flips
Research News Roundup
Research Watch blog
View from the High Ground Q&A
How It Works
News | Blog
Buy an ad link