Observation of quantum effects on radiation reaction in strong fields

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Los, E. E. and Gerstmayr, E. and Arran, C. and Streeter, M. J. V. and Colgan, C. and Cobo, C. C. and Kettle, B. and Blackburn, T. G. and Bourgeois, N. and Calvin, L. and Carderelli, J. and Cavanagh, N. and Dann, S.J.D. and Di Piazza, A. and Fitzgarrald, R. and Ilderton, A. and Keitel, C.H. and Marklund, M. and McKenna, P. and Murphy, C. D. and Najmudin, Z. and Parsons, P. and Pattathil, R. and Symes, D. R. and Tamburini, M. and Thomas, A. G. R. and Wood, J.  C. and Zepf, M. and Sarri, G. and Ridgers, C. P. and Mangles, S. P. D. (2026) Observation of quantum effects on radiation reaction in strong fields. Nature Communications, 17 (1). 1157. ISSN 2041-1723 (https://doi.org/10.1038/s41467-025-67918-8)

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Abstract

Radiation reaction, the force experienced by an accelerated charge due to radiation emission, has long been the subject of extensive theoretical and experimental research. Experimental verification of a quantum, strong-field description of radiation reaction is fundamentally important, and has wide-ranging implications for astrophysics, laser-driven particle acceleration, next-generation particle colliders and inverse-Compton photon sources for medical and industrial applications. However, the difficulty of accessing regimes where strong field and quantum effects dominate inhibited previous efforts to observe quantum radiation reaction in charged particle dynamics with high significance. We report a high significance ( > 5σ) observation of strong-field radiation reaction on electron spectra where quantum effects are substantial. We obtain quantitative, strong evidence favouring the quantum-continuous and quantum-stochastic models over the classical model; the quantum models perform comparably. The lower electron energy losses predicted by the quantum models account for their improved performance. Model comparison was performed using a novel Bayesian framework, which has widespread utility for laser-particle collision experiments, including those utilising conventional accelerators, where some collision parameters cannot be measured directly.

ORCID iDs

Los, E. E., Gerstmayr, E., Arran, C., Streeter, M. J. V., Colgan, C., Cobo, C. C., Kettle, B., Blackburn, T. G., Bourgeois, N., Calvin, L., Carderelli, J., Cavanagh, N., Dann, S.J.D., Di Piazza, A., Fitzgarrald, R., Ilderton, A., Keitel, C.H., Marklund, M., McKenna, P. ORCID logoORCID: https://orcid.org/0000-0001-8061-7091, Murphy, C. D., Najmudin, Z., Parsons, P., Pattathil, R., Symes, D. R., Tamburini, M., Thomas, A. G. R., Wood, J.  C., Zepf, M., Sarri, G., Ridgers, C. P. and Mangles, S. P. D.;
CORE (COnnecting REpositories)