Department of Physics | Université de Sherbrooke

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INTRIQ : Andréa Morello, University of New South Wales, Australie
- 10:45
- D1-2165
- Title : Single-atom spin qubits in silicon
  
  A phosphorus donor in silicon is, almost literally, the equivalent of a hydrogen atom in vacuum. It possesses electron and nuclear spins 1/2 which act as natural qubits [1], and the host material can be isotopically purified to be almost perfectly free of other spin species, ensuring extraordinary coherence times (~180 s) [2].
  I will present the current state-of-the-art in silicon quantum information technologies, a progress that started with the single-shot readout of the spin state of an electron bound to a single P atom [3]. This method was subsequently integrated with a broadband, on-chip microwave transmission line [4] to deliver coherent electromagnetic pulses and perform arbitrary rotations of the electron spin, thereby demonstrating the first single-atom spin qubit in silicon [5].
  The 31P nuclear spin can also be read out electrically - in single-shot and with fidelity > 99.8% - from a measurement of electron spin resonance, and coherently manipulated with radiofrequency pulses [6]. This yields a nuclear spin qubit in solid state with operation and readout fidelities comparable with those of ion trap systems.
  Finally, I will discuss current efforts to couple multiple donor qubits through the exchange interaction and perform entangling quantum logic gates. The ability to control the state of the 31P nuclear spin greatly simplifies the implementation of CNOT and SWAP gates, and allows for high-fidelity two-qubit operations without the requirement of atomic-precision in the donor locations.
  
  [1] B. Kane, Nature 393, 133 (1998)
  [2] M. Steger et al., Science 336, 1280 (2012)
  [3] A. Morello et al., Nature 467, 687 (2010)
  [4] J. Dehollain et al., Nanotechnology 24, 015202 (2013)
  [5] J. Pla et al., Nature 489, 541 (2012)
  [6] J. Pla et al., Nature 496, 334 (2013)
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