A Step Towards Quantum Computing: 
Entangling 10 Billion Particles
by Patrick Morgan
Discover Magazine
January 19th, 2011 
http://blogs.discovermagazine.com/80beats/2011/01/19/a-step-towards-quantum-computing-entangling-10-billion-particles/ 

In life, most people try to avoid entanglement, be it
with unsavory characters or alarmingly large balls of
twine. In the quantum world, entanglement is a necessary
step for the super-fast quantum computers of the future.

According to a study published by Nature today,
physicists have successfully entangled 10 billion
quantum bits, otherwise known qubits. But the most
significant part of the research is where the
entanglement happened-in silicon-because, given that
most of modern-day computing is forged in the smithy of
silicon technology, this means that researchers may have
an easier time incorporating quantum computers into our
current gadgets.

Quantum entanglement occurs when the quantum state of
one particle is linked to the quantum state of another
particle, so that you can't measure one particle without
also influencing the other. With this particular study,
led by John Morton at the University of Oxford, UK, the
researchers aligned the spins of electrons and
phosphorus nuclei-that is, the particles were entangled.

"The key to generating entanglement was to first align
all the spins by using high magnetic fields and low
temperatures," said Oxford's Stephanie Simmons, who also
worked on the team.. "Once this has been achieved, the
spins can be made to interact with each other using
carefully timed microwave and radio frequency pulses in
order to create the entanglement, and then prove that it
has been made." [Reuters]

If the current entanglement experiment were a cooking
recipe, it would go something like this: First, embed a
silicon crystal with 10 billion phosphorous atoms, cool
it to close to absolute zero, and then apply a sequence
of radio and microwave pulses. These pulses essentially
toy with the spins of the phosphorus nuclei and their
electrons until the spin of each nucleus matched the
spin of one of its electrons. You end up with 10 billion
entangled pairs that form a two-qubit system. It's a
major breakthrough, but the researchers aren't stopping
there:

"Creating 10 billion entangled pairs in silicon with
high fidelity is an important step forward for us," said
John Morton of Britain's Oxford University, who led the
team.. We now need to deal with the challenge of
coupling these pairs together to build a scalable
quantum computer in silicon." [Reuters]

Spinning particles are all well and nice, but what do
they have to do with computing? How does a quantum
computer actually compute?

To turn this into a silicon quantum computer, the team
must create a "huge 2D grid of entanglement", in which
nuclei are entangled with other phosphorus nuclei, as
well as electrons, says Morton. To achieve this,
electrons will be shuttled through the structure,
stitching entangled states together like a thread, he
says. By measuring the electron spins in a certain
order, computations could be performed. [New Scientist]

Such a quantum computer would run silicon circles around
conventional ones. Unlike the device sitting on your
desk, quantum computers aren't limited by the 0's and
1's of binary bits. In the weird world of quantum
mechanics, particles can exist in more that one state at
a time-they can be placed in a "superposition" of
several possible states. That means that the qubits in a
quantum computer could hold several different values
simultaneously.

It has been shown theoretically that by running
calculations in parallel, using many quantum states in
superposition, a quantum computer could solve problems
that would take a classical computer an infinite amount
of time, for example, running Shor's algorithm, which
factors large numbers into primes and could be used, for
example, to crack the most powerful encryption
algorithms on the Internet. [Nature News]

In short, a quantum computer would generate a computing
power the likes of which the world has never seen,
capable of running-as well as cracking-evermore complex
algorithms.

While impressed by the quantum leaps made by this
research, scientists are already considering the next
hurdles in the quantum computing story.

"It's nice, impressive work," says Jeremy O'Brien, a
quantum-computing specialist at the University of
Bristol, UK. But what is really needed, he says, is the
ability to do the additional nanofabrication to put
electrodes on the silicon chip to address each
individual nucleus and electron pair, a technology that
will be needed to get more than two spins entangled
together in silicon. "That would be really impressive,"
he says. [Nature News]

Even though quantum computers have a ways to go before
they wind up in your living room and in your every-day
gadgets, thanks to successful silicon entanglement that
day is getting closer.

___________________________________________

Portside aims to provide material of interest to people
on the left that will help them to interpret the world
and to change it.

Submit via email: [log in to unmask]

Submit via the Web: http://portside.org/submittous3

Frequently asked questions: http://portside.org/faq

Sub/Unsub: http://portside.org/subscribe-and-unsubscribe

Search Portside archives: http://portside.org/archive

Contribute to Portside: https://portside.org/donate