The record for the time a delicate quantum state can be maintained in silicon has been smashed in what could be a significant step towards an ultrafast quantum computer.
Scientists from Simon Fraser University, Oxford University, and Berlin have made a 'superposition' – the ability of an atom or quantum magnet (spin) to exist in two places at once – last up to three minutes and 12 seconds, over 100 times longer than the record of 1.75 seconds achieved in silicon by the same team in 2008.
A report of the research is published in this week’s Science.
A quantum computer works by storing the 0s and 1s of information in such quantum superposition states, and could solve problems that are impossible for even the fastest conventional supercomputers.
Quantum superpositions have been observed in the laboratory, for instance in large vacuum chambers, but these fragile states often only last fractions of a second, so that they do not provide a practical blueprint for building a fully-functional quantum computer. However, using the spins of atomic nuclei within an ultra-pure form of silicon, the research team were able to create a superposition state which lasted for more than three minutes (192 seconds).
'It’s by far a record in solid-state systems,' said Professor Mike Thewalt of Simon Fraser University, Canada, who led the team. 'If you’d asked people a few years ago if this was possible, they’d have said no. This opens new ways of using semiconductors such as silicon as a base for quantum computing. You can start to do things that people thought you could only do in a vacuum.'
The transformation from vacuum-based systems to solid state materials is one that conventional computing underwent decades ago when vacuum tubes were replaced with transistors.
'Silicon is the platform on which all of our current computing technology is based on,' said Dr John Morton of Oxford University’s Department of Materials. 'It's both remarkable and incredibly exciting that the same platform could host quantum computation, as it means the two approaches could be combined on the same chip to make hybrid processors: this work means you really can imagine a standard silicon chip having 'Quantum Inside'.'
A report of the research, entitled 'Quantum information storage for over 180 s using donor spins in a 28Si semiconductor vacuum', is published in Science on 8 June 2012.