We report a three-dimensional lumped-element multimode microwave resonator that enables homogeneous collective manipulation and dispersive readout of a macroscopic spin ensemble. By exploiting geometric symmetry, two antisymmetric modes with strongly suppressed cross-talk are engineered to spatially overlap and couple to the same ensemble at distinct frequencies. Using negatively charged nitrogen-vacancy centers in diamond at 28 mK, we observe collective strong coupling with a coupling strength of 5.0 MHz and demonstrate non-destructive dispersive readout via a detuned mode. The compact design, tunable coupling, and high field homogeneity make this resonator a versatile device for hybrid spin-photon systems and multimode solid-state quantum technologies.
@article{arxiv.2601.05476,
title = {A three-dimensional multimode lumped-element resonator for collective spin manipulation and dispersive readout},
author = {Zhuo Chen and Wenhua Qin and Hanyu Ren and Ziyi Liu and Kae Nemoto and William John Munro and Yingqiu Mao and Johannes Majer},
journal= {arXiv preprint arXiv:2601.05476},
year = {2026}
}