Operating two exchange-only qubits in parallel
Abstract
Semiconductors are among the most promising platforms to implement large-scale quantum computers, as advanced manufacturing techniques allow fabrication of large quantum dot arrays. Various qubit encodings can be used to store and manipulate quantum information on these quantum dot arrays. Regardless of qubit encoding, precise control over the exchange interaction between electrons confined in quantum dots in the array is critical. Furthermore, it is necessary to execute high-fidelity quantum operations concurrently to make full use of the limited coherence of individual qubits. Here, we demonstrate the parallel operation of two exchange-only qubits, consisting of six quantum dots in a linear arrangement. Using randomized benchmarking techniques, we show that issuing pulses on the five barrier gates to modulate exchange interactions in a maximally parallel way maintains the quality of qubit control relative to sequential operation. The techniques developed to perform parallel exchange pulses can be readily adapted to other quantum-dot based encodings. Moreover, we show the first experimental demonstrations of an iSWAP gate and of a charge-locking Pauli spin blockade readout method. The results are validated using cross-entropy benchmarking, a technique useful for performance characterization of larger quantum computing systems; here it is used for the first time on a quantum system based on semiconductor technology.
Cite
@article{arxiv.2504.01191,
title = {Operating two exchange-only qubits in parallel},
author = {Mateusz T. Mądzik and Florian Luthi and Gian Giacomo Guerreschi and Fahd A. Mohiyaddin and Felix Borjans and Jason D. Chadwick and Matthew J. Curry and Joshua Ziegler and Sarah Atanasov and Peter L. Bavdaz and Elliot J. Connors and J. Corrigan and H. Ekmel Ercan and Robert Flory and Hubert C. George and Benjamin Harpt and Eric Henry and Mohammad M. Islam and Nader Khammassi and Daniel Keith and Lester F. Lampert and Todor M. Mladenov and Randy W. Morris and Aditi Nethwewala and Samuel Neyens and René Otten and Linda P. Osuna Ibarra and Bishnu Patra and Ravi Pillarisetty and Shavindra Premaratne and Mick Ramsey and Andrew Risinger and John Rooney and Rostyslav Savytskyy and Thomas F. Watson and Otto K. Zietz and Anne Y. Matsuura and Stefano Pellerano and Nathaniel C. Bishop and Jeanette Roberts and James S. Clarke},
journal= {arXiv preprint arXiv:2504.01191},
year = {2025}
}