Fabrication and characterization of multi-rail Si/SiGe exchange-only spin qubits in the SLEDGE architecture

Si/SiGe exchange-only spin qubits encoded in a decoherence-free subsystem (DFS) are a compelling platform for quantum computing because of their compatibility with advanced fabrication techniques and their exclusive use of baseband pulses for control. Using the Single-Layer Etch-Defined Gate-Electrode (SLEDGE) architecture [1], which implements a CMOS-like separation between active front-end gates and electrical routing layers, we recently demonstrated high-fidelity two-qubit DFS-encoded gates [2] in a single-rail device. Scaling to multi-rail geometries, where qubits are connected to more than two neighbors, is an essential step towards quantum fault tolerance because it improves robustness and connectivity. We report on the fabrication of a two-rail, six-dot device with three distinct back-end routing layers. We also discuss the electrostatic tune-up, the initial parametric characterization, and the single-qubit randomized benchmarking performance of this device.

[1] W. Ha et al., Nano Lett., 22, 1443 (2021)

[2] A. Weinstein et al., Nature 615, 817 (2023)