###### September 4, 2009

# Quantum Computer Chips The Size Of A Penny

A new silicon chip the size of a penny uses photons to run Shor's algorithm - a well-known quantum approach - to solve mathematic problems, BBC News reported.

Before the development, the algorithm required laboratory-sized optical computers to compute the two numbers that multiply together to form a given figure.

Researchers say such factoring is the basis for a wide variety of encryption schemes and the new chip could easily be scaled up to handle more complex computing.Quantum computing efforts have grown with the ability to handle Shor's algorithm and the factoring of large numbers, which are used to exploit the counterintuitive fact that photons or trapped atoms can exist in multiple states or "superpositions" at the same time.

Quantum indeterminacy gives quantum computers a significant edge for certain types of calculations.

Quantum computers can factor large numbers with ease, where traditional or "classical" computers take much longer to crack such problems.

Encryption methods based on factoring, such as the "RSA" method, are used to make transactions on the Internet more secure.

Some experts say the future of information processing lay in optical computing "“ which uses packets of light instead of electrons as the information carrier.

However, an optical computer can also be a quantum computer considering these packets, called photons, are also endowed with the indeterminate properties that make them quantum objects.

Such photon-based quantum factoring has been accomplished before, but experts say the ability to put the heart of the machine on a standard chip could revolutionize future applications of the idea.

Jeremy O'Brien, the University of Bristol researcher who led the work, said the way people used to make this kind of circuit consumed square meters of laboratory space and took graduate students many months to align.

He told BBC News that doubling the complexity of the circuit often turns it from being a difficult task to a practically impossible one, whereas for them to double the complexity it's really straightforward.

Waveguides, which are channels etched into the chips that provide a path for the photons around the chips like the minuscule wires in conventional electronics, are used for the new approach.

O'Brien said there is still a significant amount of work to do before such waveguides are the logical choice for future optical quantum computers, but he is confident they will soon become the logical choice.

He noted that since a useful computer needs to be probably a million times more complex, a full-scale useful factoring machine is still at least two decades away.

Meanwhile, he called his team's approach an "important step in that direction."

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