@article{oai:repo.qst.go.jp:00047736,
 author = {Angerer, Andreas and Astner, Thomas and Wirtitsch, Daniel and Sumiya, Hitoshi and Onoda, Shinobu and Isoya, Junichi and Putz, Stefan and Majer, Johannes and 小野田 忍},
 journal = {Applied Physics Letters},
 month = {Jul},
 note = {We design and implement 3D-lumped element microwave cavities that spatially focus on the magnetic fields to a small mode volume. They allow coherent and uniform coupling to electron spins hosted by nitrogen vacancy centers in diamond. We achieve large homogeneous single spin coupling rates, with an enhancement of more than one order of magnitude compared to standard 3D cavities with a fundamental resonance at 3GHz. Finite element simulations confirm that the magnetic field distribution is homogeneous throughout the entire sample volume, with a root mean square deviation of 1.54%. With a sample containing 1E17 nitrogen vacancy electron spins, we achieve a collective coupling strength of Omega=12MHz, a cooperativity factor C=27, and clearly enter the strong coupling regime. This allows to interface a macroscopic spin ensemble with microwave circuits, and the homogeneous Rabi frequency paves the way to manipulate the full ensemble population in a coherent way.},
 pages = {033508-1--033508-5},
 title = {Collective strong coupling with homogeneous Rabi frequencies using a 3D lumped element microwave resonator},
 volume = {109},
 year = {2016}
}