Multi-cavity strong coupling to an electron spin ensemble: spectral and dark-state signatures

arXiv:2608.05765

P. Oehrl, B. Pérez González, A. Dunaev, M. Althammer, T. S. Parvini, F. Piazza, M. Benito, H. Huebl

Spin ensembles are considered as potential candidates for quantum memory and quantum enhanced sensing applications. Here, we explore the controlled coupling of multiple superconducting microwave cavities to a spin ensemble, which shows signatures of strong coupling and, due to the multi-mode character, the formation of dark states. In particular, the latter are of interest, as they provide a potential pathway to enhance memory times and enable protected storage of non-classical states in spin ensembles due to the suppressed coupling to the circuit environment. We model the spin multi-cavity hybrid to reproduce the spectra and extract characteristic coupling strengths using the input-output formalism.