Collective strong coupling with homogeneous Rabi frequencies using a 3D lumped element microwave resonator

Abstract

We design and implement 3D lumped element microwave cavities for the coherent and uniform coupling to electron spins hosted by nitrogen vacancy centers in diamond.Our design spatially focuses the magnetic field to a small mode volume. We achieve large homogeneous single spin coupling rates, with an enhancement of the single spin Rabi frequency of more than one order of magnitude compared to standard 3D cavities with a fundamental resonance at 3 GHz. Finite element simulations confirm that the magnetic field component is homogeneous throughout the entire sample volume, with a RMS deviation of 1.54%. With a sample containing 10 17 nitrogen vacancy electron spins we achieve a collective coupling strength of Ω = 12 MHz, 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.

Optical Spin-Wave Storage in a Solid-State Hybridized Electron-Nuclear Spin Ensemble

“…Other Λ systems could reach higher Rabi frequencies using different polarization modes. To efficiently excite microwave transitions at > 1 GHz in these Λ systems, one can use lumped-element MW cavities [55,56]. The optical Rabi frequency can also be greatly increased by using laser-written waveguides [50,57] and would allow memory bandwidths in the range of 100 MHz to 1 GHz.…”

Design of a loop-gap resonator with bimodal uniform fields using finite element analysis

“…5 cuts through the midplane of the sample volume are shown. The maximum variation of the magnetic field component perpendicular to this plane is approximately 3% for each mode, which is comparable to single-mode 3D lumped-element resonators [9].…”

“…is also an important parameter for sensitivity in spectroscopy and entering the regime of strong coupling between the resonator and a spin ensemble [9]. As mentioned previously, cavity and transmission line resonators have mode volumes tied intrinsically to the resonant wavelength, and thus have quite low filling factors for typical mm-size samples in the regime of a few GHz, making them impractical for spectroscopy in this range.…”

“…The field uniformity within the sample volume is also important for uniform saturation of a spin ensemble [9]. In Fig.…”

Broadband loop gap resonator for nitrogen vacancy centers in diamond

“…As a three-dimensional cavity resonator, the LGR provides better axial field uniformity than planar-only geometries 50,52,53 . For example, for a 3.14 mm 3 cylindrical volume (1 mm radius disk with 1 mm thickness), simulations yield σ rms = 0.8%, σ pp = 3.7% and an average B 1 of 4.8 G (see Appendix B 3).…”