Omnidirectional shuttling to avoid valley excitations in Si/SiGe quantum wells

Abstract

Conveyor-mode shuttling is a key approach for implementing intermediate-range coupling between electron-spin qubits in quantum dots. Initial implementations are encouraging; however, long shuttling trajectories are guaranteed to encounter regions of low conduction-band valley energy splittings, due to the presence of random-alloy disorder in Si/SiGe quantum wells. Here, we theoretically explore two schemes for avoiding valley-state excitations at these valley-splitting minima, by allowing the electrons to detour around them. A multichannel shuttling scheme allows electrons to tunnel between parallel channels, while a two-dimensional (2D) shuttler provides full omnidirectional control. Using simulations, we estimate shuttling fidelities in these two schemes, obtaining a clear preference for the 2D shuttler. Based on such encouraging results, we propose a modular qubit architecture based on 2D shuttling, which enables all-to-all connectivity within qubit plaquettes and high-fidelity communication between different plaquettes.

17 pages, 4 figures

References in corpus (11)

• Magnetic field dependence of valley splitting in realistic Si/SiGe quantum wells
• Spin dynamics in a strongly driven system: very slow Rabi oscillations
• Fast and robust spin manipulation in a quantum dot by electric fields
• 12-spin-qubit arrays fabricated on a 300 mm semiconductor manufacturing line
• Mapping of valley-splitting by conveyor-mode spin-coherent electron shuttling
• High-fidelity single-spin shuttling in silicon
• Strategies for enhancing spin-shuttling fidelities in Si/SiGe quantum wells with random-alloy disorder
• Counter-diabatic driving for fast spin control in a two-electron double quantum dot
• Coherent control of a triangular exchange-only spin qubit
• Valley Splitting Correlations Across a Silicon Quantum Well Containing Germanium
• Suppressing Si Valley Excitation and Valley-Induced Spin Dephasing for Long-Distance Shuttling