[IP] Hewlett Cites Progress on Quantum Computer
July 1, 2005
Hewlett Cites Progress on Quantum Computer
By JOHN MARKOFF
SAN FRANCISCO, June 30 - Scientists at Hewlett-Packard said Thursday
that they had developed a new strategy for designing a quantum
computer composed of switches of light beams that could be vastly
more powerful than today's digital electronic computers, which are
constructed from transistors.
Quantum computers are machines based on the principles of quantum
mechanics, a branch of physics that describes the quirky world of
subatomic particles where both yes and no can simultaneously be true.
The potential of quantum computing is still controversial. To date,
researchers have built small demonstration systems, but most
scientists in the field believe that it will be more than a decade
before a large-scale quantum computer can be built, and there is
debate about the range of problems such a machine will be able to solve.
The transistors in today's digital computers hold information in
binary units - either 0 or 1. In quantum computing, units of
information called "qubits" can hold both 0 and 1 simultaneously.
That capacity is the heart of the vast potential power of quantum
computers.
For example, while an array of three conventional bits could hold
only one of eight possible values at a time, a similar quantum array
could contain all eight values at once. Moreover, computing capacity
based on multi-qubit computers scales up exponentially, a fact that
underlies the potential of quantum computers.
The new strategy for designing a quantum computer was outlined in an
article researchers at Hewlett-Packard published in the May issue of
The New Journal of Physics. On Thursday the company said it would
receive as much as $10 million from the Defense Advanced Research
Projects Agency of the Pentagon, known as Darpa, to design a
prototype of the technology described by the researchers. The company
said it planned to contribute about $7.5 million to the project.
The researchers said their idea was a potentially important advance
because it may make it possible to assemble a quantum computing
system out of very large numbers of light switches.
The Hewlett-Packard paper - written by Bill Munro and Tim Spiller of
Hewlett-Packard Laboratories in Bristol, England, with Prof. Kae
Nemoto of the National Institute of Informatics in Tokyo - explores
the idea of using laser pulses to force the interaction of photons,
which can contain quantum information.
Hewlett-Packard is assembling a research program at its laboratories
in Palo Alto, Calif., to build a working prototype based on the paper.
"To perform a demonstration once will not be difficult," said Ray
Beausoleil, a researcher at that lab. "To do it reliably and to do it
in a way that will allow us to do quantum information processing, you
have to be very careful."
Several quantum computing scientists said that the paper offered an
interesting theoretical proposal but that there were significant
obstacles to building a useful system.
"The paper is interesting, and is likely a real advance in terms of
quantum computing using photons," said Umesh Vazirani, the co-
director of the Berkeley Quantum Information Center at the University
of California, Berkeley. "That said, optical quantum computing
schemes are not regarded as the most practical alternatives."
Most researchers in the field say that the leading candidate among
the competing technologies for creating workable quantum computers is
based on trapped ions, which are charged atomic particles that can be
confined and suspended using electromagnetic fields.
The Hewlett-Packard researchers are also looking for applications for
quantum computers. For example, in the field of computer security,
quantum computing may make it possible to detect eavesdropping or
tampering with great certainty.
"We're trying to figure out the quantum computing equivalent of the
hearing aid," said Mr. Beausoleil, referring to one of the earliest
uses of the transistor, which brought that technology into the
mainstream.
According to Dr. Vazirani, last year Darpa had considered financing
an ambitious "moon shot" program for quantum computing research, but
scaled back that program after some researchers warned that there was
a high likelihood of failure.
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