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The fabrication of a silicon based quantum computer at the atomic-scale

Monday 27th September 2004 - 09:45 to 10:30
INI Seminar Room 1

Quantum computers have the potential to dramatically reduce computing time for problems such as factoring [1] and database searching [2]. In particular a silicon-based quantum computer [3] 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 [4]. 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 [5]; we have been able to minimise P segregation and diffusion during Si encapsulation [6] 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 [7] 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.

[1] P. W. Shor, Proc. of the 35th Annual Symposium on Foundations of Computer Science, Editor: S. Goldwasser (IEEE Computer Society Press, USA, 1994), p. 124. [2] L. K. Grover, Phys. Rev. Lett. 79, 325 (1997). [3] B. E. Kane, Nature 393, 133 (1998). [4] J. L. O’Brien et al., Phys. Rev. B 64, 161401(R) (2001). [5] S. R. Schofield et al., Phys. Rev. Lett. 91, 136104 (2003). [6] L. Oberbeck et al., accepted for publication in Appl. Phys. Lett. (2004). [7] F.J. Ruess et al., submitted to Nano Letters (2004).

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