Pursuing high-fidelity control of spin qubits in natural Si/SiGe quantum dot

TL;DR

This paper demonstrates high-fidelity single- and two-qubit gates in natural silicon quantum dots, showing potential for fault-tolerant quantum computing despite low-frequency noise challenges.

Contribution

It reports the first high-fidelity two-qubit gates in natural silicon quantum dots, surpassing previous benchmarks and highlighting the platform's viability.

Findings

Single-qubit gate fidelity >99%

Two-qubit CZ gate fidelity of 91%

Bell state fidelity of 91%

Abstract

Electron spin qubits in silicon are a promising platform for fault-tolerant quantum computing. Low-frequency noise, including nuclear spin fluctuations and charge noise, is a primary factor limiting gate fidelities. Suppressing this noise is crucial for high-fidelity qubit operations. Here, we report on a two-qubit quantum device in natural silicon with universal qubit control, designed to investigate the upper limits of gate fidelities in a non-purified Si/SiGe quantum dot device. By employing advanced device structures, qubit manipulation techniques, and optimization methods, we have achieved single-qubit gate fidelities exceeding 99% and a two-qubit Controlled-Z (CZ) gate fidelity of 91%. Decoupled CZ gates are used to prepare Bell states with a fidelity of 91%, typically exceeding previously reported values in natural silicon devices. These results underscore that even natural silicon has the potential to achieve high-fidelity gate operations, particularly with further optimization methods to suppress low-frequency noise.