Benefits and perspective of conveyor-mode single electron shuttling in Si/SiGe*

Long-ranged coherent qubit coupling is a missing functional block for a scalable architecture of a spin-qubit based quantum computer. In a conveyor-mode shuttle, the spin-qubit is adiabatically transported while confined to a propagating sinusoidal potential in a gate-defined quantum channel [1]. Its key feature is the all-electrical operation by only few easily tunable input terminals and compatibility with industrial gate-fabrication. Spin-coherent conveyor-mode electron-shuttling could enable spin quantum-chips with scalable and sparse qubit-architecture hosting millions of spin-qubits [2].

 

I will summarize our progress on conveyor-mode single electron shuttling in Si/SiGe: In a 10 µm long shuttle device, we experimentally demonstrate a shuttle fidelity of 99.7±0.3% across the full device and back with a total distance of 19 μm [3]. By shuttling, we initialize and readout a register of 34 quantum dots with arbitrarily chosen patterns of zero and single-electrons [3] despite the presence of charge disorder [1] and lattice deformation [4]. In a 1 µm long shuttle device, we investigate the spin coherence during conveyor-mode shuttling by separation and rejoining an EPR spin-pair. We boost the shuttle velocity to 2.8 m/s and observe a rising spin-qubit dephasing time with the longer shuttle distances due to motional narrowing. We estimate the spin-shuttle infidelity due to dephasing to be 0.7 % for a total shuttle distance of at least 420 nm [5]. By spin-shuttling, we map material properties e.g., the valley splitting with unprecedented lateral resolution. Concerning a shuttle-based scalable quantum computing architecture, our device simulations for all relevant operations predict that operation fidelities exceeding 99.9 % are in reach [6].

 

[1] V. Langrock and J. A. Krzywda et al., PRX Quantum 4, 020305 (2023).

[2] J. M. Boter et al., Phys. Rev. Appl. 18, 024053 (2022).  

[3] R. Xue et al., arXiv:2306.16375 (2023).

[4] C. Corley-Wiciak et al., Phys. Rev. Appl. 20, 024056 (2023).

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

[6] M. Künne and A. Willmes et al., arXiv:2306.16348 (2023).