centre for quantum computer technology a nuclear spin quantum computer in silicon national...

CENTRE FOR QUANTUM COMPUTER TECHNOLOGY

A NUCLEAR SPINQUANTUM 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

Microanalytical Research CentreM A R C


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


Caltech-MRFM

LANL-MRFM-STM-Theory-Ion Trap QC-NMR QC

UNSW-STM -EBL-MBE -SETTs-Nanostructures

U Maryland-Single spin

detection

UQ

-Theory/Modelling-Quantum Optics

U Melbourne(ANU)

-STM-Ion Implantation ARC

$ $

$

$

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USNSA

USA COLLABORATIONS

CENTRE FOR QUANTUM COMPUTER TECHNOLOGYAUSTRALIA

LANL $


QUANTUM MECHANICAL COMPUTATION


NOT CONTROLLED NOT IN OUT IN OUT|0|1 |00|00|1|0 |01|01 |10|11 |11|10

+Phase shifts

QUANTUM LOGIC

• Any quantum computation can be reduced to a sequence of 1 and 2 qubit operations:

– H |in> = H1 H2 H3 .... Hn |in>

• Conventional operations: NOT, AND Quantum operations: NOT, CNOT


QC

CCFactoring

Quantum Physics Problems

Exhaustive SearchNP-HardProblems?

All Problems

QUANTUM ALGORITHMS

• Superposition and entanglement enables massive parallel processing

• Shor’s prime factorization algorithm (1994) relevant to cryptography

• Grover’s exhaustive search algorithm (1996)


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.


In Si:P at Temperature (T)=1K:

electron relaxation time = 1 hour

nuclear relaxation time = 1013 hours


~200 Å

A Silicon-based nuclear spin quantum computer

B. E. Kane, Nature, May 14, 1998


A & J GATES


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


(1) Nano-scale Lithography


SPIN READOUT


SINGLE ELECTRON TRANSISTORS

SPIN READOUT


Sub-300Å AuPd gates on GaAs

ELECTRON BEAM LITHOGRAPHY


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

• 25K - 1500K Variable T• 3-Chamber UHV• Plus: Si-MBE, RHEED, LEED, Auger


STEERING COMMITTEE

- Financial & Capital Management- Meets Quarterly

SRC EXECUTIVE

Director: Prof. ClarkDep. Dir: Prof. Milburn

INTERNATIONAL ADVISORY BOARD

- R&D, Commercial Strategy- Meets Half-yearly

AUSTRALIAN PROJECT MANAGEMENT - Meet Monthly (Teleconference) US PROJECT MANAGEMENT

Clark Dzurak Milburn / White Honsberg Prawer / Jamieson Simmons

Hammel (LANL) Kane (Maryland) Hughes (LANL) Roukes (Caltech)

Steering Committee Prof. C. Fell Deputy VC (Research), UNSW Prof. P. Greenfield Deputy VC (Research),

Univ. of Queensland Prof. F. Larkins Deputy VC (Research),

Univ. of Melbourne Prof. R. Clark Director SRC Prof. G. Milburn Deputy Director SRC A/Prof. S. Prawer Univ. of Melbourne Dr. P. Hammel LANL Representative Dr. P. Szczepanek NSA Representative

* or their delegated representatives

International Advisory Board Dr. B. Press* Deputy Director (S&T Programs), LANL, USA Dr. K. Miller* Quantum Computing Research Coordinator,

US National Security Agency Prof. C. Fell Deputy Vice Chancellor (Research), UNSW Prof. P. Greenfield Deputy Vice Chancellor (Research),

Univ. of Queensland Prof. F. Larkins Deputy Vice Chancellor (Research),

Univ. of Melbourne Dr. S. Williams Hewlett Packard, Palo Alto, USA Dr. D. Bolt Intel Australia Ltd. Dr. A. Ekert Clarendon Laboratory, Univ. of Oxford Prof. M. Pepper Univ. of Cambridge, UK &

Director, Toshiba Research Centre, UK Prof. M. Skeats CEO Australian Photonics CRC, &

Exec. Dir. of Australian Photonics P/L

SRC MANAGEMENT STRUCTURE


PROJECT TIMETABLE


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)


Test structures created by single ion implantation

Node Team Leader: Steven

Prawer

Atom Lithography and AFM

measurement of test structures

Theory of Coherence and Decoherence

The Melbourne Node


• 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

Key Personnel

• Academic Staff– David Jamieson– Steven Prawer– Lloyd Hollenberg

• Postdoctoral Fellows– Jeff McCallum – Paul Spizzirri– Igor Adrienko – +2

• Infrastructure– Alberto Cimmino– Roland Szymanski– William Belcher– Eliecer Para

– Geoff Leech* DeborahLouGreig

– Ming Sheng Liu– Glenn Moloney– Julius Orwa– Arthur Sakalleiou– Russell Walker

– Cameron Wellard*


Single Ion Implantation Fabrication Strategy

Resist layer

Si substrate

MeV 31P implant Etch latent damage&

metallise

Read-out state of “qubits”


MeV ion etch pits in track detector

• 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.

Scale bars: 1 m intervals

Heavy ion etch pit

Light ion etch pits


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

1 m

3 m

5 m

7.5 m

Depth

Single ion tracks

• Latent damage from single-ion irradiation of a crystal (Bi2Sr2CaCuOx)

• Beam: 230 MeV Au

• Lighter ions produce

narrower tracks!

3 nm


Project Management - A distributed system

Director Clark

Deputy Director Milburn

Theory/Modelling Array fabricationReadout

SET Dzurak

Magnetic Resonance

(LANL)

Quantum Optics

Rubeinstein-Dunlop

Single Ion Implantation

Jamieson

Atom Lithography

Prawer

Silicon MBE

Simmons

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