1. FABRICATION OF A NUCLEAR SPIN QUANTUM COMPUTER IN SILICON
Robert G. Clark
Professor of Experimental Physics
The University of New South Wales
Director
National Magnet Laboratory and
Semiconductor Naofabrication Facility

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 vs CONVENTIONAL COMPUTERS

6. 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

7. 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
All Problems
Factoring CC
Quantum Physics Problems
NP-Hard
Problems?
Exhaustive Search

8. 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/

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

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

11. A & J GATES

12. Fabrication strategy involves:
Atom-scale lithography using STM H-resist
MBE growth
EBL patterning of A, J-Gates
EBL patterning of SETs
Spin measurement by SETs or magnetic resonance force microscopy
Major collaboration with Los Alamos National Laboratory, funded through US National Security Agency

15. SPIN READOUT

16. SINGLE ELECTRON TRANSISTORS

17. SEMICONDUCTOR NANOFABRICATION FACILITY Established 1995
Consortium of major Universities in the Sydney area
Physics, Engineering Research Team
GaAs nanostructures  Si Quantum wire transistors
200 Å (0.02m) feature sizes

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

19. UNSW 3-CHAMBER UHV: STM / AFM, MBE, ANALYSIS

20. STM / AFM AT UNSW 25K - 1500K Variable T 3-Chamber UHV Plus: SiMBE
RHEED
LEED
Auger

21. SRC MANAGEMENT STRUCTURE

22. PROJECT TIMETABLE

23. 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)