What Is the Maximum Density of Microwave Control Lines in a Superconducting Quantum Computer?

Authors

Nikolas Klemola Tango, Mar Francis De Guzman, Slawomir Simbierowicz, Yuri Henriqson Accordi, Ville Nuutinen, Massimo Borrelli, Russell E Lake

Published in

Physical review letters. Volume 137. Issue 11. Pages 110202. Sep 11, 2026.

Abstract

Scaling up superconducting quantum computers requires denser control wiring, introducing microwave crosstalk along the entire cryogenic signal path rather than only near the chip. Here, we introduce a framework that combines microwave transmission-line theory with a quantum Hamiltonian description to quantify the wiring-induced microwave crosstalk and the resulting gate infidelity for an all-microwave universal gate set. Using this approach, we determine the equal-level far-end crosstalk (ELFEXT) required to operate fixed-frequency transmons at arbitrary target fidelities and find that achieving 99.99% fidelity requires ELFEXT levels of approximately -43  dB for the R_{X} gate and -73  dB for the cross-resonance gate. Finally, we use these results to bound the number of physical qubits on a chip.

PMID:
42789875
Bibliographic data and abstract were imported from PubMed on 26 Sep 2026.

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