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Proceedings Paper

Dephasing dynamics of optically active electron and hole spin qubits in self-assembled quantum dots (Conference Presentation)
Author(s): Kai Müller; Tobias Simmet; Fuxiang Li; Alexander Bechtold; Nikolai Sinitsyn; Jonathan J. Finley
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Paper Abstract

Using solid-state spin qubits for quantum information processing requires a detailed understanding of the decoherence mechanisms. For electron spins in quantum dots (QDs), considerable progress has been achieved in strong external magnetic fields; however, decoherence at very low magnetic fields remains puzzling when the magnitude of the Zeeman energy becomes comparable with intrinsic couplings. Phenomenological models of decoherence currently recognize two types of spin relaxation; fast ensemble dephasing due to the coherent precession of spin qubits around nearly static but randomly distributed hyperfine fields (∼2ns) and a much slower process (>1μs) of irreversible relaxation of the spin polarization due to nuclear spin co-flips with the central spin. Here, we demonstrate that not only two but three distinct stages of decoherence can be identified in the relaxation. Measurements and simulations of the spin projection without an external field clearly reveal an additional decoherence stage at intermediate timescales (∼750ns) [1]. The additional stage corresponds to the effect of coherent dephasing processes that occur in the nuclear spin bath itself induced by quadrupolar coupling of nuclear spins to strain driven electric field gradients, leading to a relatively fast but incomplete non-monotonic relaxation of the central spin. For hole spins we observe a more than two-orders of magnitude slower dephasing due to the reduced hyperfine interaction of the p-like wavefunction. In addition, time domain measurements of T2* and T2 (via spin-echo) are discussed. [1] A. Bechtold et al., Nature Physics 11, 1005-1008 (2015) [2] T. Simmet et al., in preparation

Paper Details

Date Published: 18 September 2018
Proc. SPIE 10732, Spintronics XI, 107320Q (18 September 2018); doi: 10.1117/12.2321201
Show Author Affiliations
Kai Müller, Technische Univ. München (Germany)
Tobias Simmet, Technische Univ. München (Germany)
Fuxiang Li, Los Alamos National Lab. (United States)
Alexander Bechtold, Technische Univ. München (Germany)
Nikolai Sinitsyn, Los Alamos National Lab. (United States)
Jonathan J. Finley, Technische Univ. München (Germany)

Published in SPIE Proceedings Vol. 10732:
Spintronics XI
Henri-Jean Drouhin; Jean-Eric Wegrowe; Manijeh Razeghi; Henri Jaffrès, Editor(s)

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