Scalable broadband circulators

Lorentz reciprocity is the symmetry in an electrical network under exchange of source and detector. Devices that break reciprocity, such as circulators or isolators, are general measurement tools, especially in the field of superconducting circuits where they are ubiquitous. Ferrite-based circulators have broad (octave) bandwidths, but their scalability is hindered by large permanent magnets. Chip-based replacement technologies have recently been developed, which achieve scalability at the cost of reduced bandwidth. In this talk, we’ll describe a general-purpose prescription for breaking Lorentz reciprocity with a combination of frequency conversion and delay. This approach allows for on-chip devices with octave bandwidths and low insertion loss. Measurements of room-temperature prototypes and design considerations for a superconducting implementation will also be discussed.