Article abstract


Nature Physics 5, 903 - 908 (2009)
Published online: 11 October 2009 | Corrected online: 27 October 2009 | doi:10.1038/nphys1424

Subject Category: Electronics, photonics and device physics

Universal quantum control of two-electron spin quantum bits using dynamic nuclear polarization

Sandra Foletti1,3, Hendrik Bluhm1,3, Diana Mahalu2, Vladimir Umansky2 & Amir Yacoby1


One fundamental requirement for quantum computation is to carry out universal manipulations of quantum bits at rates much faster than the qubit’s rate of decoherence. Recently, fast gate operations have been demonstrated in logical spin qubits composed of two electron spins where the rapid exchange of the two electrons permits electrically controllable rotations around one axis of the qubit. However, universal control of the qubit requires arbitrary rotations around at least two axes. Here, we show that by subjecting each electron spin to a magnetic field of different magnitude, we achieve full quantum control of the two-electron logical spin qubit with nanosecond operation times. Using a single device, a magnetic-field gradient of several hundred millitesla is generated and sustained using dynamic nuclear polarization of the underlying Ga and As nuclei. Universal control of the two-electron qubit is then demonstrated using quantum state tomography. The presented technique provides the basis for single- and potentially multiple-qubit operations with gate times that approach the threshold required for quantum error correction.

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  1. Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
  2. Braun Center for Submicron Research, Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot 76100, Israel
  3. These authors contributed equally to this work

Correspondence to: Amir Yacoby1 e-mail: yacoby@physics.harvard.edu

* In the version of this Article originally published online, in the final paragraph, the value of the coherence time should have been 100 μs, and the final author name in reference 28 should have been Cywinski, L., Witzel, W. M. & Das Sharma, S. These changes have been made in all versions of the Article.

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