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SUMMARY:Electron and nuclear spin qubits based on donors in silicon (Prof.
  John J. L. Morton\, University College London) - Prof. John J. L. Morton\
 , Department of Electronic and Electrical Engineering\, University College
  London
DTSTART:20141028T150000Z
DTEND:20141028T160000Z
UID:TALK51619@talks.cam.ac.uk
CONTACT:Dr. Jonathan D. Mar
DESCRIPTION:Electron and nuclear spins of donors in silicon are promising 
 candidates for representing quantum bits\, with coherence times of up to 3
  seconds for the electron spin [1]\, up to 3 minutes for the neutral donor
  nuclear spin [2]\, and 3 hours for the ionized donor nuclear spin [3]. Fu
 rthermore\, single-shot readout of both the electron spin and nuclear spin
  have been demonstrated\, with measurement fidelities of up to 99.8% [4]. 
 In order to scale up to more complex quantum devices based on donors\, it 
 is necessary to find a way to coherently control individual spins (or at l
 east a defined subset of them) within a larger array. One approach is to a
 pply global microwave fields to coherently excite resonant spins\, combine
 d with (pulsed) DC electric fields to bring different spins in or out of r
 esonance with the control field\, using the Stark shift. We present Stark 
 shift data for all group-V donors in silicon (P\, As\, Sb and Bi)\, and sh
 ow how electric fields can be used for conditional control of nuclear spin
 s. An alternative method is to apply local AC electric fields\, which we s
 how theoretically can be used to drive spin transitions in certain regimes
  through modulation of the hyperfine coupling. Finally\, we discuss progre
 ss towards combining methods for optical excitation and electrical measure
 ment to achieve high-fidelity spin readout at lower magnetic fields and hi
 gher temperature.\n\n[1] G. Wolfowicz et al.\, Nature Nanotechnology 8 561
  (2013). [2] M. Steger et al.\, Science 336 6086 (2012). [3] K Saeedi et a
 l.\, Science 342 830 (2013). [4] J.J. Pla et al.\, Nature 489 541 (2012)\;
  Nature 496 334 (2013).
LOCATION:Small Lecture Theatre\, Bragg Building\, Cavendish Laboratory (Ph
 ysics Department)
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