Journal of Applied Physics 119, 153901 (2016)
J.-M. Le Floch, N. Delhote, M. Aubourg, V. Madrangeas, D. Cros, S. Castelletto, and M. E. Tobar
1MOE Key Laboratory of Fundamental Physical Quantities Measurement, School of Physics,
Huazhong University of Science and Technology, Wuhan 430074, Hubei, China
2School of Physics, The University of Western Australia, Crawley, Western Australia 6009, Australia
3ARC Centre of Excellence for Engineered Quantum Systems, Crawley, Western Australia 6009, Australia
4XLIM, UMR CNRS 7252, Universite de Limoges, 123 av. A. Thomas, 87060 Limoges Cedex, France
5School of Aerospace, Mechanical and Manufacturing Engineering, RMIT University, Melbourne, Australia
(Received 7 December 2015; accepted 1 April 2016; published online 15 April 2016)
We investigate the microwave magnetic field confinement in several microwave three-dimensional (3D)-cavities, using a 3D finite-element analysis to determine the best design and achieve a strong coupling between microwave resonant cavity photons and solid state spins. Specifically, we design cavities for achieving strong coupling of electromagnetic modes with an ensemble of nitrogen vacancy (NV) defects in diamond. We report here a novel and practical cavity design with a magnetic filling factor of up to 4 times (2 times higher collective coupling) than previously achieved using one-dimensional superconducting cavities with a small mode volume. In addition, we show that by using a double-split resonator cavity, it is possible to achieve up to 200 times better cooperative factor than the currently demonstrated with NV in diamond. These designs open up further opportunities for studying strong and ultra-strong coupling effects on spins in solids using alternative systems with a wider range of design parameters. The strong coupling of paramagnetic spin defects with a photonic cavity is used in quantum computer architecture, to interface electrons spins with photons, facilitating their read-out and processing of quantum information. To achieve this, the combination of collective coupling of spins and cavity mode is more feasible and offers a promising method. This is a relevant milestone to develop advanced quantum technology and to test fundamental physics principles.
