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January 21, 2011

Silicon Entanglement Revives Promise of Quantum Computing

Tiffany Trader

A team of researchers based at the University of Oxford have come a step closer to unraveling the puzzle of quantum computing after generating 10 billion bits of quantum entanglement in silicon for the first time.

Entanglement is a feature of quantum physics whereby it’s possible to link together two quantum particles so that a change in one is instantly reflected in the other, regardless of the distance between them. This spooky occurrence known as quantum entanglement lies at the heart of quantum mechanics, and harnessing this phenomenon is considered the key to creating future computational devices magnitudes more powerful than traditional machines.

The scientists — an international team from the UK, Japan, Canada and Germany — used high magnetic fields and low temperatures to produce entanglement between the electron and the nucleus of an atom of phosphorous that had been embedded in silicon crystal. The electron and nucleus behave like a tiny magnet creating a spin that represents a bit of quantum information. These spins can then be coaxed into an entangled state.

Stephanie Simmons of Oxford University’s Department of Materials, first author of the report, explains:

“The key to generating entanglement was to first align all the spins by using high magnetic fields and low temperatures. Once this has been achieved, the spins can be made to interact with each other using carefully timed microwave and radiofrequency pulses in order to create the entanglement, and then prove that it has been made.”

Co-author and team leader Dr. John Morton of Oxford University’s Department of Materials, comments:

“Creating 10 billion entangled pairs in silicon with high fidelity is an important step forward for us. We now need to deal with the challenge of coupling these pairs together to build a scalable quantum computer in silicon.”

The use of phosphorus-doped silicon in this experiment is significant as it is the dominant material in modern computing chips, although it’s important to note that the type of silicon used in the experiment was not standard commercial-grade, but rather a high-purity crystal.

A report of the research, entitled “Entanglement in a solid-state spin ensemble,” has been published online this week in the journal Nature.

Full story at University of Oxford