Quantum characterization of 6-dot exchange-only qubit arrays in the SLEDGE architecture

We discuss coherent characterization of multiple 6-dot qubit array devices based on the Single-Layer Etch-Defined Gate-Electrode (SLEDGE) architecture [1] implemented in isotopically enhanced Si/SiGe. Each 6-dot array comprises two exchange-only qubits encoded in triple-dot decoherence-free subsystems (DFS). These array-wide characterizations are enabled by yield enhancements offered by SLEDGE and include the singlet-triplet pairwise dephasing times (T2*), dominated by 73Ge [2];  Q-factors reflective of charge noise magnitude for all 5 adjacent exchange axes [3]; calibration of voltage throw to exchange rotation angle for all exchange axes [4]; and excited-state energy splittings using differential axis pulsed spectroscopy (DAPS) [5]. We use the resulting key device parameters to inform error models for predicting the fidelity of exchange-only gate operations and compare those to experimental single-qubit randomized benchmarking.

[1] W. Ha et al. arXiv:2107.10916

[2] J. Kerckhoff et al. PRX Quantum 2, 010347 (2021)

[3] M.D. Reed et al. Phys. Rev. Lett. 116, 110402 (2016)

[4] R.W. Andrews et al. Nat. Nanotechnol. 14, 747 (2019)

[5] Edward H. Chen et al. Phys. Rev. Applied 15, 044033 (2021)