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SUMMARY:Single Atom Spin Qubits in Silicon - Professor Andrew Dzurak\, Uni
 versity of New South Wales\, Australia
DTSTART:20130925T131500Z
DTEND:20130925T141500Z
UID:TALK47232@talks.cam.ac.uk
CONTACT:Teri Bartlett
DESCRIPTION:Spin qubits in silicon are excellent candidates for scalable q
 uantum information processing (QIP) [1] due to their long coherence times 
 and the enormous investment in silicon MOS technology. I will discuss qubi
 ts based upon single phosphorus (P) dopant atoms in Si [2]. Projective rea
 dout of such qubits had proved challenging until single-shot measurement o
 f a single donor electron spin was demonstrated [3] using a silicon single
  electron transistor (Si-SET) and the process of spin-to-charge conversion
 . The measurement gave readout fidelities > 90% and spin lifetimes T1 > 6 
 seconds [3]\, opening the path to demonstration of electron and nuclear sp
 in qubits in silicon.\nIntegration of an on-chip microwave transmission li
 ne enables single-electron spin resonance (ESR) of the P donor electron. W
 e use this to demonstrate Rabi oscillations of the electron spin qubit\, w
 hile a Hahn echo sequence reveals electron spin coherence times T2 > 0.2 m
 s [4]. We also achieve single-shot readout of the 31P nuclear spin (with f
 idelity > 99.8%) by monitoring the two hyperfine-split ESR lines of the P 
 donor system. By applying (local) NMR pulses we can demonstrate coherent c
 ontrol of the nuclear spin qubit\, giving a coherence time T2 > 60 ms [5].
  Finally\, I will discuss very recent experiments on single-atom qubits in
  isotopically enriched 28Si devices\, in which the near elimination of the
  background 29Si nuclear spin bath allows for significantly longer spin co
 herence times\, of order 1 second.\n\n[1] D.D. Awschalom et al.\, Quantum 
 Spintronics\, Science 339\, 1174 (2013).\n[2] B.E. Kane\, A silicon-based 
 nuclear spin quantum computer\, Nature 393\, 133 (1998).\n[3] A. Morello e
 t al.\, Single-shot readout of an electron spin in silicon\, Nature 467\, 
 687 (2010).\n[4] J.J. Pla et al.\, A single-atom electron spin qubit in si
 licon\, Nature 489\, 541 (2012).\n[5] J.J. Pla et al.\, High-fidelity read
 out and control of a nuclear spin qubit in Si\, Nature 496\, 334 (2013).\n
LOCATION:Mott Seminar Room\, Cavendish Laboratory\, Department of Physics
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