TY - JOUR

T1 - Precision tomography of a three-qubit donor quantum processor in silicon

AU - Mądzik, Mateusz T.

AU - Asaad, Serwan

AU - Youssry, Akram

AU - Joecker, Benjamin

AU - Rudinger, Kenneth M.

AU - Nielsen, Erik

AU - Young, Kevin C.

AU - Proctor, Timothy J.

AU - Baczewski, Andrew D.

AU - Laucht, Arne

AU - Schmitt, Vivien

AU - Hudson, Fay E.

AU - Itoh, Kohei M.

AU - Jakob, Alexander M.

AU - Johnson, Brett C.

AU - Jamieson, David N.

AU - Dzurak, Andrew S.

AU - Ferrie, Christopher

AU - Blume-Kohout, Robin

AU - Morello, Andrea

N1 - Publisher Copyright: © 2022, The Author(s), under exclusive licence to Springer Nature Limited.

PY - 2022/1/20

Y1 - 2022/1/20

N2 - Nuclear spins were among the first physical platforms to be considered for quantum information processing1,2, because of their exceptional quantum coherence3 and atomic-scale footprint. However, their full potential for quantum computing has not yet been realized, owing to the lack of methods with which to link nuclear qubits within a scalable device combined with multi-qubit operations with sufficient fidelity to sustain fault-tolerant quantum computation. Here we demonstrate universal quantum logic operations using a pair of ion-implanted 31P donor nuclei in a silicon nanoelectronic device. A nuclear two-qubit controlled-Z gate is obtained by imparting a geometric phase to a shared electron spin4, and used to prepare entangled Bell states with fidelities up to 94.2(2.7)%. The quantum operations are precisely characterized using gate set tomography (GST)5, yielding one-qubit average gate fidelities up to 99.95(2)%, two-qubit average gate fidelity of 99.37(11)% and two-qubit preparation/measurement fidelities of 98.95(4)%. These three metrics indicate that nuclear spins in silicon are approaching the performance demanded in fault-tolerant quantum processors6. We then demonstrate entanglement between the two nuclei and the shared electron by producing a Greenberger–Horne–Zeilinger three-qubit state with 92.5(1.0)% fidelity. Because electron spin qubits in semiconductors can be further coupled to other electrons7–9 or physically shuttled across different locations10,11, these results establish a viable route for scalable quantum information processing using donor nuclear and electron spins.

AB - Nuclear spins were among the first physical platforms to be considered for quantum information processing1,2, because of their exceptional quantum coherence3 and atomic-scale footprint. However, their full potential for quantum computing has not yet been realized, owing to the lack of methods with which to link nuclear qubits within a scalable device combined with multi-qubit operations with sufficient fidelity to sustain fault-tolerant quantum computation. Here we demonstrate universal quantum logic operations using a pair of ion-implanted 31P donor nuclei in a silicon nanoelectronic device. A nuclear two-qubit controlled-Z gate is obtained by imparting a geometric phase to a shared electron spin4, and used to prepare entangled Bell states with fidelities up to 94.2(2.7)%. The quantum operations are precisely characterized using gate set tomography (GST)5, yielding one-qubit average gate fidelities up to 99.95(2)%, two-qubit average gate fidelity of 99.37(11)% and two-qubit preparation/measurement fidelities of 98.95(4)%. These three metrics indicate that nuclear spins in silicon are approaching the performance demanded in fault-tolerant quantum processors6. We then demonstrate entanglement between the two nuclei and the shared electron by producing a Greenberger–Horne–Zeilinger three-qubit state with 92.5(1.0)% fidelity. Because electron spin qubits in semiconductors can be further coupled to other electrons7–9 or physically shuttled across different locations10,11, these results establish a viable route for scalable quantum information processing using donor nuclear and electron spins.

U2 - 10.1038/s41586-021-04292-7

DO - 10.1038/s41586-021-04292-7

M3 - Journal article

C2 - 35046601

AN - SCOPUS:85123187169

VL - 601

SP - 348

EP - 353

JO - Nature

JF - Nature

SN - 0028-0836

IS - 7893

ER -