Bristol University demonstrates world's-first optical quantum computer

Posted on 2 Sep 2009 at 15:43, by David Ludlow

The University of Bristol has created the world's first optical quantum computer capable of performing mathematical calculations.

performing mathematical calculations.

The computer used single particles of light (photons) passing through a silicon chip to work out the prime factors of the number 15 (three and five). The chip has four photons that carry the input for the calculations (in binary a four-digit input allows for all numbers between 0 and 15). The input is analysed using a quantum program, which calculates the prime factors.

"This task could be done much faster by any school kid," said PhD student, Alberto Politi, who performed the experiment; "but this is a really important proof-of-principle demonstration."

Prime factors are used in encryption algorithms, such as the ones that protect secure online transactions. Having a quantum computer that can deal with these quickly and efficiently, could well improve internet security.

The team at the University of Bristol's newly-established Centre for Nanoscience and Quantum Information have developed devices where photons propagate in silica waveguides (similar to fibre optics) on silicon chips.

"This approach results in miniature, high-performance and scalable devices," said Professor Jeremy O'Brien, director of the Centre for Quantum Photonics, who lead the research. "The realisation of a quantum algorithm on a chip is an extremely important step towards an all-optical quantum computer."

For the experiment the team coupled four photons in and out of the chip using fibre optic cables. On the chip the photons travelled through silica waveguides, which formed a sequence of quantum logic gates. The output was then determined by which waveguides the photons exited the chip in.

"The really exciting thing about this result is that it will enable the development of large scale quantum circuits for photons. This opens up all kinds of possibilities," said O'Brien.

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