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Phys Rev Lett. 2016 Mar 18;116(11):116801. doi: 10.1103/PhysRevLett.116.116801. Epub 2016 Mar 16.

Noise Suppression Using Symmetric Exchange Gates in Spin Qubits.

Author information

1
Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark.
2
Department of Physics, Virginia Tech, Blacksburg, Virginia 24061, USA.
3
Condensed Matter Theory Center and Joint Quantum Institute, Department of Physics, University of Maryland, College Park, Maryland 20742-4111, USA.
4
Department of Physics and Astronomy and Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, USA.
5
School of Materials Engineering and Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, USA.
6
School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907, USA.

Abstract

We demonstrate a substantial improvement in the spin-exchange gate using symmetric control instead of conventional detuning in GaAs spin qubits, up to a factor of six increase in the quality factor of the gate. For symmetric operation, nanosecond voltage pulses are applied to the barrier that controls the interdot potential between quantum dots, modulating the exchange interaction while maintaining symmetry between the dots. Excellent agreement is found with a model that separately includes electrical and nuclear noise sources for both detuning and symmetric gating schemes. Unlike exchange control via detuning, the decoherence of symmetric exchange rotations is dominated by rotation-axis fluctuations due to nuclear field noise rather than direct exchange noise.

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