Quantum computing is still out of reach for most mainstream
industries, but continuing research in the field is making the technology more
accessible. A team of engineers at the University at Buffalo have developed a
semiconductor that can trap, detect and manipulate the single spin of an
"The task of manipulating the spin of single electrons
is a hugely daunting technological challenge that has the potential, if
overcome, to open up new paradigms of nanoelectronics," said Jonathan P. Bird,
Ph.D., professor of electrical engineering in the UB School of Engineering and
Applied Sciences and principal investigator on the project.
paper (PDF) detailing the advancement is featured in this week’s Physical Review Letters. "In this
paper, we demonstrate a novel approach that allows us to easily trap,
manipulate and detect single-electron spins, in a scheme that has the potential
to be scaled up in the future into dense, integrated circuits," added
The system developed at UB steers the electrical current in
a semiconductor by applying voltage to nanoscale gaps on select metallic gates that
are fabricated on its surface.
"As we increase the charge on the gates, this begins to
close that gap," explained Bird, "allowing fewer and fewer electrons
to pass through until eventually they all stop going through. As we squeeze off
the channel, just before the gap closes completely, we can detect the trapping
of the last electron in the channel and its spin."
"It was recently predicted that it should be possible
to use these constrictions to trap single spins," added Bird. "In
this paper, we provide evidence that such trapping can, indeed, be achieved
with quantum point contacts and that it may also be manipulated
While prior efforts to trap a single spin using nanoscale
semiconductors were proven successful, they had to operate at extremely cold
temperatures – below 1 kelvin. According to UB researchers, cooling apparatus
required to lower the temperature to such levels is not easily attainable. On
the other hand, the device developed at UB is capable of performing at 20 kelvins – a temperature that the researchers believe makes their
technology a more viable alternative.
Other recent advancements in quantum computing include the discovery of a "hidden"
order in a quantum spin liquid, paving the way
for a large number of electron spins can be coupled together to yield a
quantum mechanical state with no classical analog. Scientists were also
able to use pulses
of light to accelerate quantum computers. Most recently, scientists at the NIST
have successfully transferred data from one qubit to another by means of a
microfabricated aluminum cable.
Such advancements are slowly but steadily leading up to the
commercialization of quantum computer technology. Canadian firm D-Wave Systems unveiled and
demonstrated earlier this year its own quantum computing technology that it
aims for the commercial market – though D-Wave’s claims were met with some scepticism
from the scientific community.
quote: by Goty on October 17, 2007 at 10:13 PMThis article is a little ambiguous in its use of the term "spin". "Spin", when referring to a subatomic particle is merely a word we have assigned to one of the quantum numbers that defines every particle in our universe. Particles (ans systems of particles) can have half integer or whole integer spins, and electrons are sometimes said to be "spin up" or "spin down".When you say you are able to capture "electron spins", I'm not entirely sure what you're trying to say. Electrons HAVE spin, but the way the article states it makes it seem like an electron spin is a tangible thing.