High-fidelity and robust two-qubit gates for quantum-dot spin qubits in silicon

TL;DR

This paper develops high-fidelity, noise-robust two-qubit CNOT gates for silicon quantum-dot spin qubits, significantly improving gate fidelity and robustness, which is crucial for scalable fault-tolerant quantum computing.

Contribution

It introduces an experimentally feasible method to implement high-fidelity, noise-resistant CNOT gates considering realistic noise spectra and system uncertainties.

Findings

Achieved two orders of magnitude reduction in gate infidelity.

Demonstrated robustness against electrical noise and parameter uncertainties.

Enabled construction of high-fidelity single-qubit gates within the same framework.

Abstract

A two-qubit controlled-NOT (CNOT) gate, realized by a controlled-phase (C-phase) gate combined with single-qubit gates, has been experimentally implemented recently for quantum-dot spin qubits in isotopically enriched 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 electrical noise with the experimentally measured $1/f^{1.01}$ noise spectrum and also 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 constructed without considering any noise effect. Furthermore, within the same control framework, high-fidelity and robust single-qubit gates can also be constructed, paving the way for large-scale FTQC.