Dephasing dynamics of optically active electron and hole spin qubits in self-assembled quantum dots (Conference Presentation)

Kai Müller; Tobias Simmet; Fuxiang Li; Alexander Bechtold; Nikolai Sinitsyn; Jonathan J. Finley

doi:10.1117/12.2321201

18 September 2018 Dephasing dynamics of optically active electron and hole spin qubits in self-assembled quantum dots (Conference Presentation)

Kai Müller, Tobias Simmet, Fuxiang Li, Alexander Bechtold, Nikolai Sinitsyn, Jonathan J. Finley

Author Affiliations +

Proceedings Volume 10732, Spintronics XI; 107320Q (2018) https://doi.org/10.1117/12.2321201
Event: SPIE Nanoscience + Engineering, 2018, San Diego, California, United States

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

Conference Presentation

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Kai Müller, Tobias Simmet, Fuxiang Li, Alexander Bechtold, Nikolai Sinitsyn, and Jonathan J. Finley "Dephasing dynamics of optically active electron and hole spin qubits in self-assembled quantum dots (Conference Presentation)", Proc. SPIE 10732, Spintronics XI, 107320Q (18 September 2018); https://doi.org/10.1117/12.2321201

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KEYWORDS

Quantum communications

Quantum dots

Active optics

Magnetism

Physics

Quantum information processing

Solid state electronics

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