dielectric resonator at cryogenic temperatures*

Microwave delivery to samples in a cryogenic environment can pose experimental challenges such as restricting optical access, space constraints and heat generation. Moreover, existing solutions that overcome various experimental restrictions do not necessarily provide a large, homogeneous oscillating magnetic field over macroscopic length-scales, which is required for control of spin ensembles or fast gate operations in scaled-up quantum computing implementations. Here we show [1] fast and coherent control of a negatively charged nitrogen vacancy spin ensemble by taking advantage of the high permittivity of a KTaO₃ dielectric resonator at cryogenic temperatures. We achieve Rabi frequencies of up to 48 MHz, with a total field-to-power conversion factor CP = 9.7 mT/√?? (191 MHzRabi/√??). We use the nitrogen vacancy center spin ensemble to probe the quality factor, the coherent enhancement, and the spatial distribution of the magnetic field inside the diamond sample. The key advantages of the dielectric resonator utilized in this work are: ease of assembly, in-situ tuneability, a high magnetic field conversion efficiency, a low volume footprint, and optical transparency. This makes KTaO₃ dielectric resonators a promising platform for the delivery of microwave fields for the control of spins in various materials at cryogenic temperatures.

[1] Vallabhapurapu, H. H. et al. Fast coherent control of an NV spin ensemble using a KTaO3 dielectric resonator at cryogenic temperatures. arXiv preprint arXiv:2105.06781 (2021).