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CENTRE FOR QUANTUM COMPUTER TECHNOLOGY 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 Microanalytical Research Centre M A R C

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CENTRE FOR QUANTUM COMPUTER TECHNOLOGY 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

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CENTRE FOR QUANTUM COMPUTER TECHNOLOGY

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QUANTUM MECHANICAL COMPUTATION

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CENTRE FOR QUANTUM COMPUTER TECHNOLOGY 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

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CENTRE FOR QUANTUM COMPUTER TECHNOLOGY QC CC Factoring Quantum Physics Problems Exhaustive Search NP-Hard Problems? 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)

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CENTRE FOR QUANTUM COMPUTER TECHNOLOGY 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 10 6 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/

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CENTRE FOR QUANTUM COMPUTER TECHNOLOGY In Si:P at Temperature (T)=1K: electron relaxation time = 1 hour nuclear relaxation time = hours

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CENTRE FOR QUANTUM COMPUTER TECHNOLOGY ~200 Å A Silicon-based nuclear spin quantum computer B. E. Kane, Nature, May 14, 1998

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CENTRE FOR QUANTUM COMPUTER TECHNOLOGY A & J GATES

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CENTRE FOR QUANTUM COMPUTER TECHNOLOGY 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 31 P ion implantation 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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CENTRE FOR QUANTUM COMPUTER TECHNOLOGY (1) Nano-scale Lithography

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CENTRE FOR QUANTUM COMPUTER TECHNOLOGY SPIN READOUT

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CENTRE FOR QUANTUM COMPUTER TECHNOLOGY SINGLE ELECTRON TRANSISTORS SPIN READOUT

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CENTRE FOR QUANTUM COMPUTER TECHNOLOGY Sub-300Å AuPd gates on GaAs ELECTRON BEAM LITHOGRAPHY

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CENTRE FOR QUANTUM COMPUTER TECHNOLOGY UNSW 3-CHAMBER UHV: STM / AFM, MBE, ANALYSIS 25K K Variable T 3-Chamber UHV Plus: Si-MBE, RHEED, LEED, Auger

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CENTRE FOR QUANTUM COMPUTER TECHNOLOGY SRC MANAGEMENT STRUCTURE

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CENTRE FOR QUANTUM COMPUTER TECHNOLOGY PROJECT TIMETABLE

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CENTRE FOR QUANTUM COMPUTER TECHNOLOGY 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)

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CENTRE FOR QUANTUM COMPUTER TECHNOLOGY 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

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CENTRE FOR QUANTUM COMPUTER TECHNOLOGY 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 *

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CENTRE FOR QUANTUM COMPUTER TECHNOLOGY Single Ion Implantation Fabrication Strategy Resist layer Si substrate MeV 31 P implant Etch latent damage & metallise Read-out state of “qubits”

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CENTRE FOR QUANTUM COMPUTER TECHNOLOGY 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

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CENTRE FOR QUANTUM COMPUTER TECHNOLOGY From Huang and Sasaki, “Influence of ion velocity on damage efficiency in the single ion target irradiation system” Au-Bi2Sr2CaCu2Ox Phys Rev B 59, p m 3 m 5 m 7.5 m Depth Single ion tracks Latent damage from single-ion irradiation of a crystal (Bi 2 Sr 2 CaCuO x ) Beam: 230 MeV Au Lighter ions produce narrower tracks ! 3 nm

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CENTRE FOR QUANTUM COMPUTER TECHNOLOGY Project Management - A distributed system Director Clark Deputy Director Milburn Theory/ModellingArray fabricationReadout SET Dzurak Magnetic Resonance (LANL) Quantum Optics Rubeinstein- Dunlop Single Ion Implantation Jamieson Atom Lithography Prawer Silicon MBE Simmons

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