An Isaac Newton Institute Workshop

Entanglement and Transfer of Quantum Information

The Fabrication of a Silicon Based Quantum Computer at the Atomic-scale

Authors: Michelle Y. Simmons (School of Physics, University of New South Wales, Sydney, NSW 2052, Australia), Johnson Goh (Centre for Quantum Computer Technology, University of New South Wales, Sydney NSW 2052 Australia), Frank Ruess (Centre for Quantum Computer Technology, University of New South Wales, Sydney NSW 2052 Australia), Toby Hallam (Centre for Quantum Computer Technology, University of New South Wales, Sydney NSW 2052 Australia), Lars Oberbeck (Centre for Quantum Computer Technology, University of New South Wales, Sydney NSW 2052 Australia), Neil Curson (Centre for Quantum Computer Technology, University of New South Wales, Sydney NSW 2052 Australia), Steven Schofield (Centre for Quantum Computer Technology, University of New South Wales, Sydney NSW 2052 Australia), Robert Clark (Centre for Quantum Computer Technology, University of New South Wales, Sydney NSW 2052 Australia)

Abstract

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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