Researchers route single electrons through a Si/SiGe T-junction with 100% transfer fidelity
A 54-quantum-dot junction connects two conveyor lanes, demonstrating 2D electron pattern routing for spin qubits.
Physicists have demonstrated conveyor-mode routing of single electrons through a two-dimensional T-junction fabricated in a Si/SiGe heterostructure, according to a study published in Nature Communications 
doi.orgNature Communicationsdoi.orgOpen source ↗. The architecture connects two orthogonal one-dimensional conveyor shuttle lanes across an active footprint of 10 μm × 5 μm doi.orgNature Communicationsdoi.orgOpen source ↗. Operating at an instantaneous electron velocity of 270 mm s−1, the experimental prototype achieved an inter-lane charge transfer fidelity of 100.0000000% (+0%, −9 × 10−7%) doi.orgNature Communicationsdoi.orgOpen source ↗.
Junction architecture and electrostatic control
The T-junction device links two independent conveyor-belt lanes, designated as the x-shuttle and y-shuttle, joined at a 90° angle doi.orgNature Communicationsdoi.orgOpen source ↗. The structure contains 54 quantum dots in total, with single-electron transistors placed at the exterior-facing ends of the lanes to perform charge readout doi.orgNature Communicationsdoi.orgOpen source ↗. To overcome wiring bottlenecks without scaling up control lines, the electrostatic gates are grouped into coordinated sets driven by four channels per conveyor belt doi.orgNature Communicationsdoi.orgOpen source ↗. Overall operation and routing across the entire 54-dot system are managed using eleven voltage channels that deliver eight basic atomic pulse sequences doi.orgNature Communicationsdoi.orgOpen source ↗.
Charge transfer and electron pattern permutations
During routing, static gate bias was set to 330 mV for the active sets, while termination gates defining the lane ends were held at 0 V to create sharp potential boundaries doi.orgNature Communicationsdoi.orgOpen source ↗. The atomic pulses govern charge loading, shuttling, and inter-lane transfers without introducing supplementary gate terminals at the junction point doi.orgNature Communicationsdoi.orgOpen source ↗. Beyond transporting single electrons between orthogonal axes, researchers demonstrated the manipulation and permutation of filled quantum dots across the array doi.orgNature Communicationsdoi.orgOpen source ↗. These verified pattern swaps establish the baseline operation required for native spin-qubit SWAP gates in two-dimensional spin quantum computing architectures doi.orgNature Communicationsdoi.orgOpen source ↗.
