Enhancing the dipolar coupling of a S-T0 qubit with a transverse sweet spot

• Published in: Nature communications Vol. 10; no. 1; p. 5641
• Main Authors: Abadillo-Uriel, J. C., Eriksson, M. A., Coppersmith, S. N., Friesen, Mark
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 10.12.2019
• Subjects: 639/301/119/1000/1017; 639/766/483/2802; Humanities and Social Sciences; multidisciplinary; Science; Science (multidisciplinary)
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-019-13548-w

A fundamental challenge for quantum dot spin qubits is to extend the strength and range of qubit interactions while suppressing their coupling to the environment, since both effects have electrical origins. Key tools include the ability to take advantage of physical resources in different regimes, and to access optimal working points, sweet spots, where dephasing is minimized. Here, we explore an important resource for singlet-triplet qubits: a transverse sweet spot (TSS) that enables transitions between qubit states, a strong dipolar coupling, and leading-order protection from electrical fluctuations. Of particular interest is the possibility of transitioning between the TSS and symmetric operating points while remaining continuously protected. This arrangement is ideal for coupling qubits to a microwave cavity, because it combines tunability of the coupling with noise insensitivity. We perform simulations with 1 ∕ f -type electrical noise, demonstrating that two-qubit gates mediated by a resonator can achieve fidelities >99% under realistic conditions. Semiconductor quantum dots are controlled by external fields that are tuned in order to optimise for information storage or inter-qubit interaction. Here the authors identify a working point for long-range interactions that can be reached with continuous protection from environmental noise.