Entangling electrons and nuclei in a four-qubit, two-atom device in silicon
ORAL
Abstract
Ion-implanted 31P donors in silicon have demonstrated exceptionally long coherence times, and >99% gate fidelities, including >99% 2-qubit fidelity for nuclear spins coupled through a common electron at ~6 nm distance. Extending the spatial range of 2-qubit gates requires using the electron exchange interaction. Here we present a four-qubit system (two electrons, two 31P nuclei) consisting of two exchange-coupled phosphorus donor atoms in silicon, interacting over a distance of 18.5+-3.5 nm. We create and benchmark Bell states to show that this coupling can be used to entangle both the electrons and nuclei. The electron Bell state fidelity is 93 +- 9% [1]. Nuclear spins are entangled via a controlled-Z gate, created through conditional electron spin rotations. The nuclear Bell state fidelity seems severely limited by SPAM errors. Future efforts will incorporate the Maxwell’s demon initialization method [2] to reduce SPAM and achieve entanglement of all four qubits.
[1] H. Stemp et al. arXiv:2309.15463 (2023)
[2] M. Johnson et al., Phys. Rev. X 12, 041008 (2022)
*The research was funded by the Australian Research Council (grant no. CE170100012) and the US Army Research Office (contract no. W911NF-23-1-0113)
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Publication:Stemp, H. G., Asaad, S., van Blankenstein, M. R., Vaartjes, A., Johnson, M. A. I., Mądzik, M. T., Heskes, A. J. A., Firgau, H. R., Su, R. Y., Yang, C. H., Laucht, A., Ostrove, C. I., Rudinger, K. M., Young, K., Blume-Kohout, R., Hudson, F. E., Dzurak, A. S., Itoh, K. M., Jakob, A. M., … Morello, A. (2023). Tomography of entangling two-qubit logic operations in exchange-coupled donor electron spin qubits (arXiv:2309.15463). arXiv. http://arxiv.org/abs/2309.15463
