Bias-Preserving Entanglement of Kerr-Cat Qubits with an ATS Coupler
Abstract
Kerr-cat qubits offer a hardware-efficient route to fault-tolerant quantum computing by suppressing bit-flip errors exponentially, while phase-flip errors increase only linearly with the mean photon number. To maintain this protection, entangling operations must be bias-preserving, ensuring that phase-flip errors occurring during the gate do not propagate into bit-flip errors. In this paper, we propose an asymmetrically threaded SQUID (ATS) parametric coupler to implement high-fidelity, bias-preserving entangling gates between Kerr-cat qubits. By engineering a photon-number asymmetry between the control and target modes, we enable fast gate operations that suppress non-adiabatic leakage without complex pulse shaping. Through numerical simulations of the full circuit Hamiltonian, we demonstrate a bias-preserving CX gate achieving 99.69% fidelity in the absence of photon loss for a gate duration of 50 ns. Under a single-photon loss rate of 100 kHz, our protocol yields a noise bias of 9922, exceeding the noise bias of a naive non-bias-preserving CX implementation by approximately a factor of 570. These results support the ATS coupler as a valuable building block for concatenated cat-qubit architectures.
Related
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BibTeX
@misc{yurtseven2026biaspreserving,
title = {{Bias-Preserving Entanglement of Kerr-Cat Qubits with an ATS Coupler}},
author = {Kerem Yurtseven and Shantanu R. Jha and Apoorva Limaye and Risav Pokhrel and Maral Mahmoudi Kamelabad and Muhammad Waqar Amin},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.28749},
eprint = {2610.28749},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.28749},
}
RIS
TY - UNPB
TI - Bias-Preserving Entanglement of Kerr-Cat Qubits with an ATS Coupler
AU - Kerem Yurtseven
AU - Shantanu R. Jha
AU - Apoorva Limaye
AU - Risav Pokhrel
AU - Maral Mahmoudi Kamelabad
AU - Muhammad Waqar Amin
PY - 2026
DA - 2026/10/26
PB - arXiv
DO - 10.48550/arxiv.2610.28749
UR - https://arxiv.org/abs/2610.28749
AB - Kerr-cat qubits offer a hardware-efficient route to fault-tolerant quantum computing by suppressing bit-flip errors exponentially, while phase-flip errors increase only linearly with the mean photon number. To maintain this protection, entangling operations must be bias-preserving, ensuring that phase-flip errors occurring during the gate do not propagate into bit-flip errors. In this paper, we propose an asymmetrically threaded SQUID (ATS) parametric coupler to implement high-fidelity, bias-preserving entangling gates between Kerr-cat qubits. By engineering a photon-number asymmetry between the control and target modes, we enable fast gate operations that suppress non-adiabatic leakage without complex pulse shaping. Through numerical simulations of the full circuit Hamiltonian, we demonstrate a bias-preserving CX gate achieving 99.69% fidelity in the absence of photon loss for a gate duration of 50 ns. Under a single-photon loss rate of 100 kHz, our protocol yields a noise bias of 9922, exceeding the noise bias of a naive non-bias-preserving CX implementation by approximately a factor of 570. These results support the ATS coupler as a valuable building block for concatenated cat-qubit architectures.
ER -