Broadband Magnetless Isolation in a Flux-Pumped, Dispersion-Engineered Transmission Line

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Main Authors: Demarets, M., Vadiraj, A. M., Caloz, C., De Greve, K.
Format: Preprint
Published: 2025
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author Demarets, M.
Vadiraj, A. M.
Caloz, C.
De Greve, K.
author_facet Demarets, M.
Vadiraj, A. M.
Caloz, C.
De Greve, K.
contents Isolators are commonly found in the amplification chain of microwave setups to shield sensitive devices such as superconducting qubits from noise and back-scattered signals. Conventional ferrite-based isolators are bulky, lossy and rely on strong magnetic fields, which pose challenges for their co-integration in large-scale superconducting devices. Although several magnetless approaches based on parametric modulation have been explored to overcome these limitations, none has yet experimentally demonstrated wideband isolation on par with ferrite devices. Here, we propose a compact modulation-based isolator that achieves large isolation bandwidth using a dispersion-engineered transmission line. The engineered line forms an effective two-mode system that enables broadband isolation by supporting adiabatic mode conversion over a wide instantaneous bandwidth. Numerical simulations show that this architecture can provide more than 20 dB isolation across 4 - 8 GHz, matching the performance of ferrite-based isolators. Moreover, we propose an on-chip superconducting device implementation that shows promise against parameter variations and enables a scalable path for co-integration with future large-scale superconducting systems.
format Preprint
id arxiv_https___arxiv_org_abs_2509_24551
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Broadband Magnetless Isolation in a Flux-Pumped, Dispersion-Engineered Transmission Line
Demarets, M.
Vadiraj, A. M.
Caloz, C.
De Greve, K.
Quantum Physics
Instrumentation and Detectors
Isolators are commonly found in the amplification chain of microwave setups to shield sensitive devices such as superconducting qubits from noise and back-scattered signals. Conventional ferrite-based isolators are bulky, lossy and rely on strong magnetic fields, which pose challenges for their co-integration in large-scale superconducting devices. Although several magnetless approaches based on parametric modulation have been explored to overcome these limitations, none has yet experimentally demonstrated wideband isolation on par with ferrite devices. Here, we propose a compact modulation-based isolator that achieves large isolation bandwidth using a dispersion-engineered transmission line. The engineered line forms an effective two-mode system that enables broadband isolation by supporting adiabatic mode conversion over a wide instantaneous bandwidth. Numerical simulations show that this architecture can provide more than 20 dB isolation across 4 - 8 GHz, matching the performance of ferrite-based isolators. Moreover, we propose an on-chip superconducting device implementation that shows promise against parameter variations and enables a scalable path for co-integration with future large-scale superconducting systems.
title Broadband Magnetless Isolation in a Flux-Pumped, Dispersion-Engineered Transmission Line
topic Quantum Physics
Instrumentation and Detectors
url https://arxiv.org/abs/2509.24551