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

J. Medford; Johannes Beil; J.M. Taylor; S.D. Bartlett; A.C. Doherty; E.I. Rashba; D.P. DiVincenzo; H. Lu; A.C. Gossard; Charles M. Marcus

doi:10.1038/nnano.2013.168

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

J. Medford, Johannes Beil, J.M. Taylor, S.D. Bartlett, A.C. Doherty, E.I. Rashba, D.P. DiVincenzo, H. Lu, A.C. Gossard, Charles M. Marcus

Condensed Matter Physics

160 Citations (Scopus)

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.

Original language	English
Journal	Nature Nanotechnology
Volume	8
Issue number	9
Pages (from-to)	654-659
ISSN	1748-3387
DOIs	https://doi.org/10.1038/nnano.2013.168
Publication status	Published - 1 Sept 2013

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AU - Medford, J.

AU - Beil, Johannes

AU - Taylor, J.M.

AU - Bartlett, S.D.

AU - Doherty, A.C.

AU - Rashba, E.I.

AU - DiVincenzo, D.P.

AU - Lu, H.

AU - Gossard, A.C.

AU - Marcus, Charles M.

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N2 - 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.

AB - 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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DO - 10.1038/nnano.2013.168

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

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