Absence of Charge Offset Drift in a Transmon Qubit
Abstract
Superconducting quantum circuits are sensitive to their electrostatic environment: uncontrolled charges accumulating on the electrodes of a Josephson junction shift the energy levels of a qubit, perturbing its operation and restricting their design. This effect is captured by a single parameter - the charge offset - whose slow, unpredictable drift has proven difficult to eliminate in practice. Here, we report a tantalum-based transmon qubit in which the charge offset remains pinned at zero over nearly three months of measurements, including two thermal cycles, with no observable compromise to the qubit lifetime. This exceptional stability disappears in later cooldowns, indicating a fragile mechanism at play. We attribute it to the inductance of a thin superconducting layer inadvertently formed in parallel with the Josephson junction during fabrication. X-ray surface spectroscopy suggests this layer arises from an incomplete wet-etch of tantalum on sapphire. Deliberately engineering such a layer offers a route to eliminating charge-offset drift in superconducting circuits more broadly.
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BibTeX
@misc{rospars2026absence,
title = {{Absence of Charge Offset Drift in a Transmon Qubit}},
author = {Adria Rospars and Hector Hutin and Yannick Seis and Cristóbal Lledó and Réouven Assouly and Romain Cazali and Rémy Dassonneville and Ambroise Peugeot and Alexandre Blais and Audrey Bienfait and Benjamin Huard},
howpublished = {HAL},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2603.12367},
eprint = {2603.12367},
archivePrefix = {arXiv},
url = {https://hal.science/hal-05800373v1},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Absence of Charge Offset Drift in a Transmon Qubit
AU - Adria Rospars
AU - Hector Hutin
AU - Yannick Seis
AU - Cristóbal Lledó
AU - Réouven Assouly
AU - Romain Cazali
AU - Rémy Dassonneville
AU - Ambroise Peugeot
AU - Alexandre Blais
AU - Audrey Bienfait
AU - Benjamin Huard
PY - 2026
DA - 2026/10/14
PB - HAL
DO - 10.48550/arxiv.2603.12367
UR - https://hal.science/hal-05800373v1
AB - Superconducting quantum circuits are sensitive to their electrostatic environment: uncontrolled charges accumulating on the electrodes of a Josephson junction shift the energy levels of a qubit, perturbing its operation and restricting their design. This effect is captured by a single parameter - the charge offset - whose slow, unpredictable drift has proven difficult to eliminate in practice. Here, we report a tantalum-based transmon qubit in which the charge offset remains pinned at zero over nearly three months of measurements, including two thermal cycles, with no observable compromise to the qubit lifetime. This exceptional stability disappears in later cooldowns, indicating a fragile mechanism at play. We attribute it to the inductance of a thin superconducting layer inadvertently formed in parallel with the Josephson junction during fabrication. X-ray surface spectroscopy suggests this layer arises from an incomplete wet-etch of tantalum on sapphire. Deliberately engineering such a layer offers a route to eliminating charge-offset drift in superconducting circuits more broadly.
ER -