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Quantum physics enables perfectly secure cloud computing

20 January 2012

Both the data and program are encrypted in 'blind quantum computing', such that fully secure quantum computation can be performed on a remote server

Image: Equinox Graphics
Computer data processing and storage are increasingly done in the 'cloud', connecting users over a network to a powerful server. A challenge is to ensure that users' data remains private.

Research carried out by Dr Joseph Fitzsimons at the Centre for Quantum Technologies (CQT) at NUS, together with scientists in Austria, Canada and the UK may offer a solution. The team has demonstrated a 'quantum computation' in which the input, processing and output remained unknown to the computer. Details are published in the 20 January issue of top-tier journal Science.

The technique works for advanced 'quantum computers' still under research that exploit the properties of quantum physics. Such computers are expected to play an important role in future information processing since scientists predict they can outperform classical computers at many tasks.

The new scheme would offer users a way to securely access quantum computers when they first become available as specialised facilities, like today's supercomputers, as well as promising security for any future quantum 'cloud'.

Quantum computers are designed to harness counter-intuitive quantum effects such as data bits being in indeterminate states – not a one, nor a zero, but somehow both at the same time.

Quantum effects also provide an uncrackable way of sending secret messages, known as quantum cryptography. It may sound esoteric, but companies today are selling devices to do it.

'Blind quantum computation' combines the power of quantum computing with the security of quantum cryptography. "Unless there is a fundamental mistake in the present understanding of physics, the 'blindness' is perfect," said Dr Fitzsimons. "There is no way to attack it."

Dr Fitzsimons and his theoretical colleagues first described the idea in a 2009 paper. They have now collaborated with an experimental group to perform a proof-of-principle demonstration. This used photons, the particles of light, for a computation with four quantum bits of data.

Other investigators in the study come from the Vienna Center for Quantum Science and Technology at the University of Vienna and the Institute for Quantum Optics and Quantum Information in Austria; The University of Edinburgh, UK; and the Institute for Quantum Computing and University of Waterloo in Canada.

An independent Perspective on the result is provided in Science by Dr Vlatko Vedral, who is jointly affiliated with the University of Oxford, UK, and CQT.

By Centre for Quantum Technologies

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