Physica status solidi. C, Conferences and critical reviews/Physica status solidi. C, Current topics in solid state physics

Electron spin dynamics and hyperfine interaction in coupled quantum dots

Özgür Çakır, T. Takagahara

Published Dec 1, 2006• 2 citations

Publisher

Abstract

We have investigated the quantum dynamics of the electron-nuclei coupled system in a double quantum dot and discovered a couple of new phenomena related to the quantum nature of nuclear spin system. Especially, the bunching of results of the electron spin measurements and the revival in the conditional probabilities are salient features of quantum dynamics. The underlying mechanism is the squeezing of the nuclear spin state through the electron spin measurements. This squeezing is expected to lead to the elongation of the electron spin coherence time. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

DOI: 10.1002/pssc.200672857

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Physica status solidi. C, Conferences and critical reviews/Physica status solidi. C, Current topics in solid state physics

Electron spin dynamics and hyperfine interaction in coupled quantum dots

Özgür Çakır, T. Takagahara

Published Dec 1, 2006• 2 citations

Publisher

Abstract

DOI: 10.1002/pssc.200672857

Related papers

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Özgür Çakır, T. Takagahara

arXiv:cond-mat/0609217AIP conference proceedingsJan 1, 20071 citation

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{T}_{2}^{*}

by dynamically transferring the polarization from the electron spins to the nuclear spins. This polarization transfer is achieved by cycling the electron spins over the $S\ensuremath{-}{T}_{+}$ anticrossing. Here, we investigate, both quantitatively and qualitatively, how this hyperfine-mediated dynamical polarization transfer is influenced by the Rashba and Dresselhaus spin-orbit interaction. In addition to

{T}_{2}^{*}

, we determine the singlet return probability

{P}_{s}

, a quantity that can be measured in experiments. Our results suggest that the spin-orbit interaction establishes a mechanism that can polarize the nuclear spins in the direction opposite to that of hyperfine-mediated nuclear spin polarization. In materials with relatively strong spin-orbit coupling, this interplay of spin-orbit and hyperfine-mediated nuclear spin polarizations prevents any notable increase in the $S\ensuremath{-}{T}_{0}$ qubit decoherence time

{T}_{2}^{*}

We analyze nuclear-spin dynamics in quantum dots and defect centers with a bound electron under electron-mediated coupling between nuclear spins due to the hyperfine interaction (``

J

coupling'' in NMR). Our analysis shows that the Overhauser field generated by the nuclei at the position of the electron has short-time dynamics quadratic in time for an initial nuclear-spin state without transverse coherence. The quadratic short-time behavior allows for an extension of the Overhauser-field lifetime through a sequence of projective measurements (quantum Zeno effect). We analyze the requirements on the repetition rate of measurements and the measurement accuracy to achieve such an effect. Further, we calculate the long-time behavior of the Overhauser field for effective electron Zeeman splittings larger than the hyperfine coupling strength and find, both in a Dyson-series expansion and a generalized master-equation approach, that for a nuclear-spin system with a sufficiently smooth polarization the electron-mediated interaction alone leads only to a partial decay of the Overhauser field by an amount of the order of the inverse number of nuclear spins interacting with the electron.