Development of Ring Resonators for Non-Reciprocal Devices

Circulators and isolators are vital for protecting quantum devices from undesired signals, but currently these devices are based on ferrite materials and the Faraday effect. The large magnetic fields required to achieve significant rotation necessitate a bulky independent housing and significant shielding. The bulky form factor and unavoidable insertion losses associated with the packaging limit the ultimate performance of ferrite isolators, as well as the quantity that can be housed in a dilution refrigerator. We propose another regime of potentially low insertion-loss, high directional-contrast nonmagnetic microwave isolator based on ring resonators and the use of temporal modulation to break the chiral symmetry of wave propagation. This technique was previously used to produce high-performance narrow-band optical isolators [1]. Here we present first steps toward a cryogenic microwave implementation, including the development of a compatible low-backscattering microwave ring resonator. This work will help take a crucial step towards developing practical low insertion loss, high directionality isolators possessing on-chip integrability with superconducting circuits for parametric amplifiers and other potential applications.



[1] D. B. Sohn, O. E. Örsel, and G. Bahl, Electrically Driven Optical Isolation through Phonon-Mediated Photonic Autler–Townes Splitting, Nat. Photonics 15, 822 (2021).