Silicon chips for optical quantum technologies

Generating and detecting single photons, by Carmel King, from the University of Bristol websiteDoes this have implications for solar physics? Some fascinating research from the University of Bristol: A team of physicists and engineers has demonstrated exquisite control of single particles of light – photons – on a silicon chip to make a major advance towards the long sought after goal of a super-powerful quantum computer.

Dr Jeremy O’Brien, his PhD student Alberto Politi, and their colleagues at Bristol University have demonstrated the world’s smallest optical controlled-NOT gate – the building block of a quantum computer. The team were able to fabricate their controlled-NOT gate from silica wave-guides on a silicon chip, resulting in a miniaturised device and high-performance operation. “This is a crucial step towards a future optical quantum computer, as well as other quantum technologies based on photons,” said Dr O’Brien. The team reports its results in the March 27 2008 Science Express – the advanced online publication of the journal Science.

Quantum technologies aim to exploit the unique properties of quantum mechanics, the physics theory that explains how the world works at very small scales. For example a quantum computer relies on the fact that quantum particles, such as photons, can exist in a “superposition” of two states at the same time – in stark contrast to the transistors in a PC which can only be in the state “0” or “1”.

Photons are an excellent choice for quantum technologies because they are relatively noise free; information can be moved around quickly – at the speed of light; and manipulating single photons is easy. Making two photons “talk” to each other to realise the all-important controlled-NOT gate is much harder, but Dr O’Brien and his colleagues at the University of Queensland demonstrated this back in 2003 [Nature 426, 264]. Photons must also “talk” to each other to realise the ultra-precise measurements that harness the laws of quantum mechanics – quantum metrology…

Generating and detecting single photons, by Carmel King, from the University of Bristol website

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