Optimal electron trajectories improving the spin-shuttling fidelity beyond the adiabatic limit

Spin-qubit quantum computers are currently limited by a connectivity problem. A promising solution is the use of conveyor-mode shuttling architectures [1] where the qubit encoded in the spin of an electron is reliably transported by a moving quantum dot [2]. During this process the spin experiences decoherence from uncontrollable features of the device heterostructures such as interface roughness, valley degree of freedom and spin-orbit coupling [3]. In this work we compute the energy splitting of the valley with the help of an alloy-disorder model [4] and we focus on the dephasing interaction between spin and valley. Using quantum optimal control techniques we find electron trajectories that improve the spin-shuttling fidelity by reducing the valley excitation even at higher speeds than the adiabatic limit. The experimental adequacy of our results is inspected through statistical sampling of different devices and bandwidth limitation of the electron trajectories.

[1] Künne and Willmes et al., arXiv:2306.16348 (2023)

[2] Struck et al., arXiv:2307.04897 (2023)

[3] Langrock and Krzywda et al., PRX Quantum 4, 020305 (2023)

[4] Wuetz, et al., Nat. Comm. 13, 7730 (2022)