Hamiltonian phase error in resonantly driven CNOT gate above the fault-tolerant threshold

• Published in: npj quantum information Vol. 10; no. 1; pp. 8 - 9
• Main Authors: Wu, Yi-Hsien, Camenzind, Leon C., Noiri, Akito, Takeda, Kenta, Nakajima, Takashi, Kobayashi, Takashi, Chang, Chien-Yuan, Sammak, Amir, Scappucci, Giordano, Goan, Hsi-Sheng, Tarucha, Seigo
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 11-01-2024; Nature Publishing Group; Nature Portfolio
• Subjects: 639/766/483/2802; 639/766/483/481; Classical and Quantum Gravitation; Computers; Electrons; Energy; Error correction & detection; Fault tolerance; Magnetic fields; Physics; Physics and Astronomy; Quantum Computing; Quantum dots; Quantum Field Theories; Quantum Information Technology; Quantum Physics; Relativity Theory; Silicon; Spintronics; String Theory; Tomography
• ISSN: 2056-6387; 2056-6387
• DOI: 10.1038/s41534-023-00802-9

Because of their long coherence time and compatibility with industrial foundry processes, electron spin qubits are a promising platform for scalable quantum processors. A full-fledged quantum computer will need quantum error correction, which requires high-fidelity quantum gates. Analyzing and mitigating gate errors are useful to improve gate fidelity. Here, we demonstrate a simple yet reliable calibration procedure for a high-fidelity controlled-rotation gate in an exchange-always-on Silicon quantum processor, allowing operation above the fault-tolerance threshold of quantum error correction. We find that the fidelity of our uncalibrated controlled-rotation gate is limited by coherent errors in the form of controlled phases and present a method to measure and correct these phase errors. We then verify the improvement in our gate fidelities by randomized benchmark and gate-set tomography protocols. Finally, we use our phase correction protocol to implement a virtual, high-fidelity, controlled-phase gate.