Neil Curson, Senior Research Fellow at the Centre for Quantum Computer Technology, at the University of New South Wales, Sydney, Australia, presented the following seminar from the Pacific Rim Conference in Nanoscience (7-11 September 2004). The seminar is available for viewing and discussion through the Internanotech Community at http://nanotech.colayer.net/
Atomic-Scale Fabrication of a Silicon-based Quantum Computer
Quantum computers have the potential to dramatically reduce computing time for problems such as factoring  and database searching . In particular a silicon-based quantum computer  shows promise for its potential to scale to a large number of qubits and for its compatibility with standard CMOS processing.
Our group has designed a fabrication strategy for the realisation of a scaleable quantum computer based in silicon using a combination of scanning probe microscopy for single qubit placement and silicon molecular beam epitaxy to encapsulate the qubit array . In order to achieve this goal we have demonstrated the following key steps: we have been able to incorporate single P atoms as the qubits in silicon with atomic precision ; we have been able to minimise P segregation and diffusion during Si encapsulation  and we have imaged the array of buried P atoms using scanning tunneling microscopy to prove that the array remains intact after the encapsulation stage. Recently we have been able to fabricate a robust electrical device in silicon using the scanning tunneling microscope to lithographically pattern the dopants  and have demonstrated that this device can be contacted and measured outside the ultra-high vacuum environment.
We highlight the importance of our results for the fabrication of a Si-based quantum computer and discuss the final stages of the fabrication process required to realize a functional device, including the formation of an electrical isolation barrier and the alignment of surface metal electrodes to the buried P atom array.
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