1. A NUCLEAR SPIN QUANTUM COMPUTER IN SILICON
Microanalytical Research Centre
M A R C
A NUCLEAR SPIN QUANTUM COMPUTER IN SILICON
National Nanofabrication Laboratory, School of Physics, University of New South Wales
Laser Physics Centre, Department of Physics, University of Queensland
Microanalytical Research Centre, School of Physics, University of Melbourne

2. MOTIVATION
Quantum Computers will be the world’s fastest computing devices, e.g. decryption (prime factors of a composite number) - Factor a 400 digit number 108 times faster
Spin-off technology development for conventional silicon processing at the sub-1000Å scale

4. QUANTUM MECHANICAL COMPUTATION

5. QUANTUM LOGIC
Any quantum computation can be reduced to a sequence of 1 and 2 qubit operations:
H |in> = H1 H2 H Hn |in>
Conventional operations: NOT, AND Quantum operations: NOT, CNOT

6. QUANTUM ALGORITHMS
Superposition and entanglement enables massive parallel processing
Shor’s prime factorization algorithm (1994) relevant to cryptography
Grover’s exhaustive search algorithm (1996) QC CC
Factoring
Quantum Physics Problems
Exhaustive Search
NP-Hard
Problems?
All Problems

7. EXPERIMENTAL QUANTUM COMPUTATION
Bulk spin resonance (Stanford, MIT): ? qubits
Trapped cooled ions (Los Alamos, Oxford): ? qubits
True quantum computer may require 106 qubits
“Solid state” (semiconductor) quantum computer architectures
Proposed using electron and nuclear spin to store qubits
Electrons: D. Loss and D. DiVincenzo, Phys. Rev. A 57, 120 (1998).
Nuclei: V. Privman, I. D. Vagner, and G. Kventsel, Phys. Lett. A in press, quant-ph/

8. In Si:P at Temperature (T)=1K:
electron relaxation time = 1 hour
nuclear relaxation time = hours

9. A Silicon-based nuclear spin quantum computer B. E
A Silicon-based nuclear spin quantum computer B. E. Kane, Nature, May 14, 1998
~200 Å

10. A & J GATES

11. Fabrication Pathways Fabrication strategies:
(1) Nano-scale lithography:
Atom-scale lithography using STM H-resist
MBE growth
EBL patterning of A, J-Gates
EBL patterning of SETs
(2) Direct 31P ion implantation
Spin measurement by SETs or magnetic resonance force microscopy
Major collaboration with Los Alamos National Laboratory, funded through US National Security Agency

12. (1) Nano-scale Lithography

13. SPIN READOUT

14. SINGLE ELECTRON TRANSISTORS
SPIN READOUT

15. ELECTRON BEAM LITHOGRAPHY
Sub-300Å AuPd gates on GaAs

16. UNSW 3-CHAMBER UHV: STM / AFM, MBE, ANALYSIS
25K K Variable T
3-Chamber UHV
Plus: Si-MBE, RHEED, LEED, Auger

17. SRC MANAGEMENT STRUCTURE

18. PROJECT TIMETABLE

19. SUMMARY Quantum Computers have enormous potential
Solid-state quantum computation is the best candidate for scalability
Offers integration with existing Si technology
UNSW strategy to use qubits stored on nuclear spins (concept by Kane)

20. The Melbourne Node Node Team Leader: Steven Prawer
Test structures created by single ion implantation
Atom Lithography and AFM measurement of test structures
Theory of Coherence and Decoherence

21. Key Personnel Students Academic Staff Geoff Leech* DeborahLouGreig
David Jamieson
Steven Prawer
Lloyd Hollenberg
Postdoctoral Fellows
Jeff McCallum
Paul Spizzirri
Igor Adrienko +2
Infrastructure
Alberto Cimmino
Roland Szymanski
William Belcher
Eliecer Para
Students
Paul Otsuka
MatthewNorman
Elizabeth Trajkov
Brett Johnson
Amelia Liu*
Leigh Morpheth
David Hoxley*
Andrew Bettiol
Deborah Beckman
Jacinta Den Besten
Kristie Kerr
Louie Kostidis
Poo Fun Lai
Jamie Laird
Kin Kiong Lee
Geoff Leech* DeborahLouGreig
Ming Sheng Liu
Glenn Moloney
Julius Orwa
Arthur Sakalleiou
Russell Walker
Cameron Wellard*

22. Single Ion Implantation Fabrication Strategy
Etch latent damage & metallise
Read-out state of “qubits”
MeV 31P implant
Resist layer
Si substrate

23. MeV ion etch pits in track detector
Scale bars: 1 mm intervals
Heavy ion etch pit
Light ion etch pits
Single MeV heavy ions are used to produce latent damage in plastic
Etching in NaOH develops this damage to produce pits
Light ions produce smaller pits
1. Irradiate
2. Latent damage
3. Etch
From: B.E. Fischer, Nucl. Instr. Meth. B54 (1991) 401.

24. Single ion tracks
Latent damage from single-ion irradiation of a crystal (Bi2Sr2CaCuOx)
Beam: 230 MeV Au
Lighter ions produce narrower tracks!
Depth
1 mm
3 mm
5 mm
7.5 mm
3 nm
From Huang and Sasaki, “Influence of ion velocity on damage efficiency in the single ion target irradiation system” Au-Bi2Sr2CaCu2Ox Phys Rev B 59, p3862

25. Project Management - A distributed system
Director Clark
Deputy Director Milburn
Readout
Theory/Modelling
Array fabrication
SET Dzurak
Magnetic Resonance (LANL)
Quantum Optics Rubeinstein-Dunlop
Single Ion Implantation
Jamieson
Atom Lithography
Prawer
Silicon MBE
Simmons