ZZ-Free bSWAP Gates under Strong Driving in Far-Detuned Fixed-Frequency Transmons
Abstract
Far-detuned frequency allocations in fixed-frequency superconducting processors mitigate spectral crowding but constrain cross-resonance interactions at practical drive amplitudes. Here, we demonstrate that a single strong drive induces a large XX−YY interaction in the far-detuned regime, while a weak second tone tunes the accompanying ZZ phase. The interaction realizes a 150-ns √(bSWAP) gate, which can directly prepare a maximally entangled state from the ground state. For the implementations on the same qubit pair at matched drive strengths, cross resonance gives a shorter CNOT operation, while √(bSWAP) gives a 33% shorter SWAP operation with a higher IRB fidelity. The multilevel theory further predicts a regime where stronger driving can yield a speed advantage for CNOT as well, a possibility absent in the two-level model. As an application of the XX−YY interaction, we also demonstrate two-spin squeezing beyond the standard quantum limit through two-axis countertwisting. The interaction realized here complements cross resonance and offers a route to efficient gate synthesis and quantum simulation of interacting spin systems.
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BibTeX
@misc{machino2026zzfree,
title = {{ZZ-Free bSWAP Gates under Strong Driving in Far-Detuned Fixed-Frequency Transmons}},
author = {Akinori Machino and Kazuhisa Ogawa and Yuto Ikegai and Takafumi Miyanaga and Koichiro Ban and Nilton F. G. Filho and Hidehisa Shiomi and Toshi Sumida and Shuhei Tamate and Yutaka Tabuchi and Yasunobu Nakamura and Makoto Negoro},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.21936},
eprint = {2610.21936},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.21936},
}
RIS
TY - UNPB
TI - ZZ-Free bSWAP Gates under Strong Driving in Far-Detuned Fixed-Frequency Transmons
AU - Akinori Machino
AU - Kazuhisa Ogawa
AU - Yuto Ikegai
AU - Takafumi Miyanaga
AU - Koichiro Ban
AU - Nilton F. G. Filho
AU - Hidehisa Shiomi
AU - Toshi Sumida
AU - Shuhei Tamate
AU - Yutaka Tabuchi
AU - Yasunobu Nakamura
AU - Makoto Negoro
PY - 2026
DA - 2026/10/15
PB - arXiv
DO - 10.48550/arxiv.2610.21936
UR - https://arxiv.org/abs/2610.21936
AB - Far-detuned frequency allocations in fixed-frequency superconducting processors mitigate spectral crowding but constrain cross-resonance interactions at practical drive amplitudes. Here, we demonstrate that a single strong drive induces a large XX−YY interaction in the far-detuned regime, while a weak second tone tunes the accompanying ZZ phase. The interaction realizes a 150-ns √(bSWAP) gate, which can directly prepare a maximally entangled state from the ground state. For the implementations on the same qubit pair at matched drive strengths, cross resonance gives a shorter CNOT operation, while √(bSWAP) gives a 33% shorter SWAP operation with a higher IRB fidelity. The multilevel theory further predicts a regime where stronger driving can yield a speed advantage for CNOT as well, a possibility absent in the two-level model. As an application of the XX−YY interaction, we also demonstrate two-spin squeezing beyond the standard quantum limit through two-axis countertwisting. The interaction realized here complements cross resonance and offers a route to efficient gate synthesis and quantum simulation of interacting spin systems.
ER -