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Self-consistent measurement and state tomography of an exchange-only spin qubit.

Authors
  • Medford, J
  • Beil, J
  • Taylor, J M
  • Bartlett, S D
  • Doherty, A C
  • Rashba, E I
  • DiVincenzo, D P
  • Lu, H
  • Gossard, A C
  • Marcus, C M
Type
Published Article
Journal
Nature Nanotechnology
Publisher
Springer Nature
Publication Date
Sep 01, 2013
Volume
8
Issue
9
Pages
654–659
Identifiers
DOI: 10.1038/nnano.2013.168
PMID: 23995458
Source
Medline
License
Unknown

Abstract

Quantum-dot spin qubits characteristically use oscillating magnetic or electric fields, or quasi-static Zeeman field gradients, to realize full qubit control. For the case of three confined electrons, exchange interaction between two pairs allows qubit rotation around two axes, hence full control, using only electrostatic gates. Here, we report initialization, full control, and single-shot readout of a three-electron exchange-driven spin qubit. Control via the exchange interaction is fast, yielding a demonstrated 75 qubit rotations in less than 2 ns. Measurement and state tomography are performed using a maximum-likelihood estimator method, allowing decoherence, leakage out of the qubit state space, and measurement fidelity to be quantified. The methods developed here are generally applicable to systems with state leakage, noisy measurements and non-orthogonal control axes.

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