We demonstrate rapid, high-fidelity state preparation and measurement in exchange-only Si/SiGe triple-quantum-dot qubits. Fast measurement integration (980 ns) and initialization (≈300 ns) operations are performed with all-electrical, baseband control. We emphasize a leakage-sensitive joint initialization and measurement metric, developed in the context of exchange-only qubits but applicable more broadly, and report an infidelity of 2.5±0.5×10−3. This result is enabled by a high-valley-splitting heterostructure, initialization at the 2-to-3 electron charge boundary, and careful assessment and mitigation of T1 during spin-to-charge conversion. The ultimate fidelity is limited by a number of comparably-important factors, and we identify clear paths towards further improved fidelity and speed. Along with an observed single-qubit randomized benchmarking error rate of 1.7×10−3, this work demonstrates initialization, control, and measurement of Si/SiGe triple-dot qubits at fidelities and durations which are promising for scalable quantum information processing.
@article{arxiv.2112.09801,
title = {Fast and high-fidelity state preparation and measurement in triple-quantum-dot spin qubits},
author = {Jacob Z. Blumoff and Andrew S. Pan and Tyler E. Keating and Reed W. Andrews and David W. Barnes and Teresa L. Brecht and Edward T. Croke and Larken E. Euliss and Jacob A. Fast and Clayton A. C. Jackson and Aaron M. Jones and Joseph Kerckhoff and Robert K. Lanza and Kate Raach and Bryan J. Thomas and Roland Velunta and Aaron J. Weinstein and Thaddeus D. Ladd and Kevin Eng and Matthew G. Borselli and Andrew T. Hunter and Matthew T. Rakher},
journal= {arXiv preprint arXiv:2112.09801},
year = {2023}
}