Enhancing the Coherence of a Spin Qubit by Operating it as a Feedback Loop That Controls its Nuclear Spin Bath

Hendrik Bluhm, Sandra Foletti, Diana Mahalu, Vladimir Umansky, and Amir Yacoby
Phys. Rev. Lett. 105, 216803 – Published 19 November 2010
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Abstract

In many realizations of electron spin qubits the dominant source of decoherence is the fluctuating nuclear spin bath of the host material. The slowness of this bath lends itself to a promising mitigation strategy where the nuclear spin bath is prepared in a narrowed state with suppressed fluctuations. Here, this approach is realized for a two-electron spin qubit in a GaAs double quantum dot and a nearly tenfold increase in the inhomogeneous dephasing time T2* is demonstrated. Between subsequent measurements, the bath is prepared by using the qubit as a feedback loop that first measures its nuclear environment by coherent precession, and then polarizes it depending on the final state. This procedure results in a stable fixed point at a nonzero polarization gradient between the two dots, which enables fast universal qubit control.

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  • Received 21 March 2010

DOI:https://doi.org/10.1103/PhysRevLett.105.216803

© 2010 The American Physical Society

Authors & Affiliations

Hendrik Bluhm1, Sandra Foletti1, Diana Mahalu2, Vladimir Umansky2, and Amir Yacoby1,*

  • 1Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
  • 2Braun Center for Submicron Research, Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot 76100, Israel

  • *yacoby@physics.harvard.edu.

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Issue

Vol. 105, Iss. 21 — 19 November 2010

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