High-Fidelity and Robust Two-Qubit Gates for Quantum-Dot Spin Qubits in Silicon
Chia-Hsien Huang1*, C. H. Yang2, Chien-Chang Chen1, A. S. Dzurak2, Hsi-Sheng Goan1
1Department of Physics, National Taiwan University, Taipei, Taiwan
2Centre for Quantum Computation and Communication Technology, The University of New South Wales, Sydney, Australia
* Presenter:Chia-Hsien Huang, email:d01222002@ntu.edu.tw
A two-qubit controlled-NOT (CNOT) gate, realized by a controlled-phase (C-phase) gate together with some single-qubit gates, has been experimentally implemented recently for quantum-dot spin qubits in isotopically purified silicon, a promising solid-state system for practical quantum computation. In the experiments, the single-qubit gates have been demonstrated with fault-tolerant control-fidelity, but the infidelity of the two-qubit C-phase gate is, primarily due to the electrical noise, still higher than the required error threshold for fault-tolerant quantum computation (FTQC). Here, by taking the realistic system parameters and the experimental constraints on the control pulses into account, we construct experimentally realizable high-fidelity CNOT gates robust against the electrical noise with the experimentally measured 1/f1.01 noise spectrum and against the uncertainty in the interdot tunnel coupling amplitude. Our optimal CNOT gate has about two orders of magnitude improvement in gate infidelity over the ideal C-phase gate. Furthermore, within the same control framework, high-fidelity and robust single-qubit gates can also be constructed, paving the way for large-scale FTQC.

Keywords: Quantum gates, High-fidelity, Robust, Qubit, Quantum-dot