Kavli Affiliate: Giordano Scappucci
| First 5 Authors: Akito Noiri, Kenta Takeda, Takashi Nakajima, Takashi Kobayashi, Amir Sammak
| Summary:
Fault-tolerant quantum computers which can solve hard problems rely on
quantum error correction. One of the most promising error correction codes is
the surface code, which requires universal gate fidelities exceeding the error
correction threshold of 99 per cent. Among many qubit platforms, only
superconducting circuits, trapped ions, and nitrogen-vacancy centers in diamond
have delivered those requirements. Electron spin qubits in silicon are
particularly promising for a large-scale quantum computer due to their
nanofabrication capability, but the two-qubit gate fidelity has been limited to
98 per cent due to the slow operation.Here we demonstrate a two-qubit gate
fidelity of 99.5 per cent, along with single-qubit gate fidelities of 99.8 per
cent, in silicon spin qubits by fast electrical control using a
micromagnet-induced gradient field and a tunable two-qubit coupling. We
identify the condition of qubit rotation speed and coupling strength where we
robustly achieve high-fidelity gates. We realize Deutsch-Jozsa and Grover
search algorithms with high success rates using our universal gate set. Our
results demonstrate the universal gate fidelity beyond the fault-tolerance
threshold and pave the way for scalable silicon quantum computers.
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