Coherent Conveyor Mode Shuttling of Electrons and their Spin

One- and two-qubit manipulation fidelity has been increased to the point at which  quantum error correction is possible, if the qubit platform becomes scalable.

One missing key technology for this scale-up is a coherent medium-range coupling between two qubits at 1 to 10 µm distance. It would enable a sparse-qubit architecture and makes space for signal-line fan-out and cryogenic electronics tiles integrated on the qubit chip[1].

In this talk, we present a novel approach named conveyor-mode shuttling, which relies on physically transporting the electron by a propagating wave-potential with simple input signals across an electrostatically defined quantum-channel[2]. Previously, we demonstrated single electron shuttling across a distance of 420 nm using only four sinusoidal control signals[3]. Building up on this result, we will introduce high fidelity single electron shuttling at a velocity of v=4.2 m/s in the conveyor mode. For 1 µm shuttling, such velocity is required to reduce the shuttling time well below the typical spin-dephasing time of natural silicon. We show initialisation of the shuttle device on one end by two electron in a spin-singlet. Shuttling only one of these electrons, we generate a separated Einstein-Podolsky-Rosen spin-pair. Combining the electrons by shuttling again, we detect their spin-singlet fraction by Pauli-spin blockade and explore the spin-coherence of the shuttling process.

[1] Boter, J.M. et al. Spiderweb Array: A Sparse Spin-Qubit Array. Phys. Rev. Appl. 18, 024053 (2022)

[2] Langrock, V. et al. Blueprint of a scalable spin qubit shuttling device for coherent mid-range qubit transfere in disordered Si/SiGe/SiO₂. Preprint at https://arxiv.org/abs/2202.11793  (2022)

[3] Seidler et al. Conveyor-mode single-electron shuttling in Si/SiGe for a scalable quantum computing architecture. npj Quantum Inf. 8, 100 (2022)