On the Path to Building the World’s First Silicon-Based Quantum Computer: Control of Electron States on Single Phosphorus Atoms

ARC Centre of Excellence for Quantum Computer Technology
School of Physics, University of Melbourne

Friday, 21 September 2007, 3.30pm, EN101, Ground floor, Engineering Building, Hawthorn.

Recently, the first demonstration of time-resolved control and detection of single-electron transfers in a silicon device implanted with exactly two phosphorus donors was demonstrated by our Centre. At milli-Kelvin temperatures the device shows charge state relaxation by phonon emission with impressively long several millisecond relaxation times for single-donor charge states. This device has potential applications as the element of a solid-state quantum computer. The construction of a practical quantum computer has been identified as one of the major challenges for 21st Century nanotechnology. A large scale quantum computer will have many revolutionary applications. Quantum computers will be used for solving problems that are exceptionally time consuming, or impossible, on classical computers. These include the ability to accurately model molecular systems that are the basis of chemistry and physics at the most fundamental level and to form the nodes of a future quantum internet where information will be transmitted as highly secure streams of single photons in quantum states which cannot be intercepted. To construct our device, we extended conventional silicon device engineering with ion beam physics to allow precise placement and control of single phosphorus atoms in silicon. Our novel fabrication technique allows each device to self-assemble itself thanks to an on-chip ion impact detector. The chip is able to sense the implantation of a single low energy phosphorus atom which embeds just 20 nanometres below the device surface. Similar devices, fabricated in diamond, have shown potential for control of single nuclear spins. This suggests engineered quantum states in silicon and diamond will be viable for information processing in large scale applications.

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