Numerical simulation of coherent spin-shuttling in a QuBus with dilute charge defects

The shuttling of a single electron in a QuBus is a key element for scalable spin-qubit architectures in Si/SiGe [1,2]. Electrostatic disorder within the shuttling channel can limit the coherence of a spin qubit during conveyor-mode shuttling [3]. Owing to this limitation, we numerically investigate the impact of very dilute charged defects on the spin-dephasing of a single electron spin-qubit passing the defect by conveyor-mode shuttling [2,3]. We use a finite-element model for a Si/SiGe heterostructure and simulate the conveyor-mode shuttling of an electron under the influence of dilute charge defects randomly placed near the shuttling channel. Our analysis considers different positions of a single charged point defect relative to the center of the shuttle channel, multiple orbital states of the electron with g-factor differences between orbital levels, phonon-assisted relaxation processes, different shuttling velocities, and different strengths of the confining potential. We solve the time-dependent quantum master equation describing the evolution of the shuttled electron and investigate the conditions under which the qubit accumulates a larger nondeterministic phase. Our study aims to better identify the critical charge defect density of the heterostructure for conveyor-mode spin-qubit shuttling devices and to quantify the impact of these defects on the shuttling fidelity.

[1] Struck et al., Nat. Commun. 15, 1325 (2024).

[2] Xue et al., Nat. Commun. 15, 2296 (2024).

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