Microwave radiometry of a quantum-critical hybrid Josephson array Galvin, Kristen W Bubis, Anton Mikalsen, Melissa Schiela, William F. Elfeky, Bassel H. Strickland, William M. Phan, Duc T Shabani, Javad Higginbotham, Andrew P ; https://orcid.org/0000-0003-2607-2363 ddc:530 Arrays of Josephson junctions can be tuned through anomalous metallic, quantum-critical, and insulating regimes. We introduce an alternative experimental probe, capturing microwave radiation across all three regimes, using a two-dimensional array of superconductor-semiconductor hybrid Josephson junctions as a model system. Our approach allows calibration of the sample’s circuit parameters and provides isolation from measurement back-action effects. We measure the radiation temperature of the anomalous metal and find that it is hotter than both the quantum-critical and insulating regimes. We further show that the anomalous metallic regime is more susceptible to additional heating than other regimes, explaining its emergence in otherwise thermalized systems. Turning to the quantum-critical regime, we discover nonlinear scaling of radiative noise with applied bias, consistent with theoretical predictions of universal nonequilibrium behavior at quantum-critical points. American Physical Society 2026 info:eu-repo/semantics/article doc-type:article text http://purl.org/coar/resource_type/c_2df8fbb1 https://research-explorer.ista.ac.at/record/22323 https://research-explorer.ista.ac.at/download/22323/22350 Galvin KW, Bubis A, Mikalsen M, et al. Microwave radiometry of a quantum-critical hybrid Josephson array. <i>Physical Review Applied</i>. 2026;26. doi:<a href="https://doi.org/10.1103/75bl-mm3b">10.1103/75bl-mm3b</a> eng info:eu-repo/semantics/altIdentifier/doi/10.1103/75bl-mm3b info:eu-repo/semantics/altIdentifier/issn/2331-7019 info:eu-repo/semantics/altIdentifier/arxiv/2409.09835 https://creativecommons.org/licenses/by/4.0/ info:eu-repo/semantics/openAccess