Bell-state tomography in a silicon many-electron artificial molecule

Ross C. C. Leon (), Chih Hwan Yang, Jason C. C. Hwang, Julien Camirand Lemyre, Tuomo Tanttu, Wei Huang, Jonathan Y. Huang, Fay E. Hudson, Kohei M. Itoh, Arne Laucht, Michel Pioro-Ladrière, Andre Saraiva () and Andrew S. Dzurak ()
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Ross C. C. Leon: The University of New South Wales
Chih Hwan Yang: The University of New South Wales
Jason C. C. Hwang: The University of New South Wales
Julien Camirand Lemyre: Université de Sherbrooke
Tuomo Tanttu: The University of New South Wales
Wei Huang: The University of New South Wales
Jonathan Y. Huang: The University of New South Wales
Fay E. Hudson: The University of New South Wales
Kohei M. Itoh: Keio University
Arne Laucht: The University of New South Wales
Michel Pioro-Ladrière: Université de Sherbrooke
Andre Saraiva: The University of New South Wales
Andrew S. Dzurak: The University of New South Wales

Nature Communications, 2021, vol. 12, issue 1, 1-6

Abstract: Abstract An error-corrected quantum processor will require millions of qubits, accentuating the advantage of nanoscale devices with small footprints, such as silicon quantum dots. However, as for every device with nanoscale dimensions, disorder at the atomic level is detrimental to quantum dot uniformity. Here we investigate two spin qubits confined in a silicon double quantum dot artificial molecule. Each quantum dot has a robust shell structure and, when operated at an occupancy of 5 or 13 electrons, has single spin- $$\frac{1}{2}$$ 1 2 valence electron in its p- or d-orbital, respectively. These higher electron occupancies screen static electric fields arising from atomic-level disorder. The larger multielectron wavefunctions also enable significant overlap between neighbouring qubit electrons, while making space for an interstitial exchange-gate electrode. We implement a universal gate set using the magnetic field gradient of a micromagnet for electrically driven single qubit gates, and a gate-voltage-controlled inter-dot barrier to perform two-qubit gates by pulsed exchange coupling. We use this gate set to demonstrate a Bell state preparation between multielectron qubits with fidelity 90.3%, confirmed by two-qubit state tomography using spin parity measurements.

Date: 2021
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DOI: 10.1038/s41467-021-23437-w

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