Hole Spin Decoherence in Quantum Dots

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Hole Spin Decoherence in Quantum Dots
Denis Bulaev and Daniel Loss Department of
Physics University of Basel, Switzerland
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Motivation

• Quantum computing
• Qubit with long coherence time

Pros of heavy hole

• Weak hyperfine interactions with nuclei
  (p-symmetry)

Cons of heavy hole

• Strong spin-orbit interactions with light holes
• Difficulties in coherent spin manipulation
• ...

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Motivation

• Quantum computing
• Qubit with long coherence time

Pros of heavy hole

• Weak hyperfine interactions with nuclei
  (p-symmetry)
• Weak spin-orbit interactions with light holes in
  2D QDs

Cons of heavy hole

• Difficulties in coherent spin manipulation
• ...

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Motivation

• Quantum computing
• Qubit with long coherence time

Pros of heavy hole

• Weak hyperfine interactions with nuclei
  (p-symmetry)
• Weak spin-orbit interactions with light holes in
  2D QDs
• Possibilities for coherent spin manipulation via
  EDSR

Cons of heavy hole

• ...

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Effective Hamiltonian of Heavy Holes
R. Winkler, PRB 62, 4245 (2000)
DB D. Loss, PRL 95, 076805 (2006)
g(GaAs) 2.5, g(InAs) -2.2.
H.W. van Kestern, et al., PRB 41, 5283 (1990)
M.Bayer,et al., PRL 82, 1748 (1999)
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Spin Relaxation Rates
GaAs Quantum Dot (g 2.5)
InAs Quantum Dot (g -2.2)
DB D. Loss, PRL 95, 076805 (2006)
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B-field Dependence of Rates
Electrons
phonons
Hso
Heavy holes
Dresselhaus SO coupling
Rashba SO coupling
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Summary

• Anticrossing and spin mixing (GaAs QD)
• T2 2T1 at low temperatures
• Peaks on the spin relaxation decay curve (GaAs
  QD)
• Rashba Dresselhaus
• Spin relaxation time for heavy holes CAN BE
  longer than for electrons