A method for the numerical analysis of hybrid lumped-distributed superconducting quantum circuits

Fuente: arXiv
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Auteurs principaux: Zaccaria, Simona, Gnudi, Antonio
Format: Preprint
Publié: 2025
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author Zaccaria, Simona
Gnudi, Antonio
author_facet Zaccaria, Simona
Gnudi, Antonio
contents We present a method for the numerical analysis of superconducting quantum circuits combining lumped elements, either linear or non-linear (i.e.~Josephson junctions), and distributed coplanar waveguide (CPW) structures. CPW transmission lines and multiline couplers are directly modeled without discretizing them into lumped-element equivalents, and the circuit Hamiltonian parameters are extracted by using the energy participation ratio (EPR) method. This approach enables fast and accurate extraction of mode frequencies, anharmonicities, cross-Kerr interactions, and Purcell decay rates without relying on full electromagnetic simulations, while naturally accounting for higher-order modes of distributed components. We have implemented the proposed method in a Python framework, QuLTRA (Quantum hybrid Lumped and TRansmission lines circuits Analyzer), which we have used to validate the approach against full electromagnetic simulations (Ansys HFSS, pyEPR), existing circuit-analysis tools (QuCAT), and designs reported in the literature. The comparisons show excellent agreement with orders-of-magnitude reductions in computational time relative to full-wave solvers. We demonstrate applications including Purcell-protected readout, multimode ultra-strong coupling, and multiplexed qubit readout, illustrating how the method can support fast and reliable early-stage circuit design.
format Preprint
id arxiv_https___arxiv_org_abs_2509_03651
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle A method for the numerical analysis of hybrid lumped-distributed superconducting quantum circuits
Zaccaria, Simona
Gnudi, Antonio
Quantum Physics
We present a method for the numerical analysis of superconducting quantum circuits combining lumped elements, either linear or non-linear (i.e.~Josephson junctions), and distributed coplanar waveguide (CPW) structures. CPW transmission lines and multiline couplers are directly modeled without discretizing them into lumped-element equivalents, and the circuit Hamiltonian parameters are extracted by using the energy participation ratio (EPR) method. This approach enables fast and accurate extraction of mode frequencies, anharmonicities, cross-Kerr interactions, and Purcell decay rates without relying on full electromagnetic simulations, while naturally accounting for higher-order modes of distributed components. We have implemented the proposed method in a Python framework, QuLTRA (Quantum hybrid Lumped and TRansmission lines circuits Analyzer), which we have used to validate the approach against full electromagnetic simulations (Ansys HFSS, pyEPR), existing circuit-analysis tools (QuCAT), and designs reported in the literature. The comparisons show excellent agreement with orders-of-magnitude reductions in computational time relative to full-wave solvers. We demonstrate applications including Purcell-protected readout, multimode ultra-strong coupling, and multiplexed qubit readout, illustrating how the method can support fast and reliable early-stage circuit design.
title A method for the numerical analysis of hybrid lumped-distributed superconducting quantum circuits
topic Quantum Physics
url https://arxiv.org/abs/2509.03651