FABRICATION OF A NUCLEAR SPIN

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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
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MOTIVATION

• Quantum Computers will be the worlds 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

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QUANTUM MECHANICAL COMPUTATION
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QUANTUM vs CONVENTIONAL COMPUTERS
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QUANTUM LOGIC Any quantum computation can be
reduced to a sequence of 1 and 2 qubit
operations H ingt H1 H2 H3 .... Hn
ingt Conventional operations NOT, AND
Quantum operations NOT, CNOT
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QUANTUM ALGORITHMS
Superposition and entanglement enables massive
parallel processing Shors 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
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EXPERIMENTAL QUANTUM COMPUTATION Bulk spin
resonance (Stanford, MIT) 1-10?
qubits Trapped cooled ions (Los Alamos,
Oxford) 1-100? 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/9707017.
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In SiP at Temperature (T)1K electron
relaxation time 1 hour nuclear relaxation time
1013 hours
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A Silicon-based nuclear spin quantum
computer B. E. Kane, Nature, May 14, 1998
200 Å
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A J GATES
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• 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

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SPIN READOUT
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SINGLE ELECTRON TRANSISTORS
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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

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ELECTRON BEAM LITHOGRAPHY
Sub-300Å AuPd gates on GaAs
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UNSW 3-CHAMBER UHV STM / AFM, MBE, ANALYSIS
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STM / AFM AT UNSW

• 25K - 1500K Variable T
• 3-Chamber UHV
• Plus
• SiMBE
• RHEED
• LEED
• Auger

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SRC MANAGEMENT STRUCTURE
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PROJECT TIMETABLE
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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)