New study paves the way for quantum-enhanced computation
The 'optical chip' developed by ORC researchers
20 December 2012
Despite the widespread research in quantum computers, no-one has built a machine that uses quantum-mechanics to solve
computational problems faster than a classical computer.
Quantum computers harness the power of atoms and molecules to perform memory and processing tasks and have the potential
to perform certain calculations significantly faster than any silicon-based computer.
Now scientists from the Universities of Southampton and Oxford have worked together to develop the first experimental
demonstration of the boson sampling model of computation, which could pave the way to larger devices that could offer
the first definitive quantum-enhanced computation. Boson sampling, by taking advantage of recent advances in photonics,
offers a promising route to building such a device in the not-distant future, providing convincing evidence for the computational
power of quantum mechanics.
Photons are absolutely identical at a fundamental level – formally they are bosons – which means that they
exhibit strong quantum level – ‘entanglement ’. This means that if two sufficiently identical photons come together
they behave in a connected way – almost as if they ‘clump’ together. When scaled up to multiple input photons these
‘entanglements’ cause the outputs of a boson-sampling circuit to ‘clump’ together in a characteristic way, predictable
by quantum mechanics, but difficult to calculate using conventional computers.
The University of Southampton team, led by Professor Peter Smith
and Dr James Gates
from the Optoelectronics Research Centre (ORC),
developed the photonic chip on which the experiment was performed. Dr Gates says: “The chip offers a scalable route,
perhaps the only scalable route, to build large linear systems required for larger boson sampling machines. If one is going to
eventually need to move ‘on chip’ with more complex boson sampling machines, there is obvious benefit in building the
proof-of-principle devices ‘on chip’ as well. The move to optical processing on a chip format can be likened to the shift to
integrated silicon chips in electronics.”
The work is part of a long term collaboration with Professor Ian Walmsley’s group at the Clarendon Lab, University of Oxford.
Supported by the Engineering and Physical Sciences Research Council (EPSRC), this latest output involved fabrication and optical
characterisation at the University of Southampton and the quantum measurements being made in Oxford. Lead author Justin Spring
from the University of Oxford describes the significance as:
“Boson sampling provides a model of quantum-enhanced computation that is experimentally feasible with existing photonic technology.
Future generations of boson sampling machines (BSMs) will beneﬁt from ongoing advances in integrated photonics.”
The research is published in the latest issue of Science.
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