EPR Analysis in Superconducting Quantum Circuits

EPR / scQubits Tutorial

EPR means Energy Participation Ratio. It explains what percentage of total electromagnetic energy is stored in each circuit component. In QClang documentation, place EPR after HFSS and Q3D because EPR converts field simulation information into quantum parameters such as qubit frequency, anharmonicity, coupling strength, and Kerr effects.

Transmon qubit: capacitor plus Josephson junction structure.

Josephson junction: two superconductors separated by a thin insulating layer.

Field-energy visualization used before participation analysis.

Why EPR is needed	It predicts qubit behavior before fabrication and reduces trial-and-error design iterations.
Energy distribution	It shows how energy is shared between capacitor, Josephson junction, resonator, and other modes.
HFSS relationship	HFSS calculates fields; EPR converts field information into quantum circuit parameters.
Parameters obtained	Qubit frequency, anharmonicity, coupling strength, Kerr effects, and mode interactions.
Industry use	Used in superconducting qubit research, academic labs, circuit QED workflows, and scalable chip studies.
scQubits placement	Use scQubits-style analysis after EM simulation to display Hamiltonian, energy levels, coherence, participation, and interactions.