Non-reciprocal microwave devices with a topological material*

Cryogenic circulators and isolators are nonreciprocal devices indispensable in shielding qubits against noise coming from the output measurement chain of superconducting quantum computing architectures and axion dark matter search experiments. However, conventional  nonreciprocal ferrite devices are several centimeters in size and, thereby, impose a space limitation when scaling superconducting quantum computing systems. Here, we explore how micron-sized devices made from topological materials exhibit non-reciprocity, thus, enabling the potential for on-chip devices orders-of-magnitude smaller than conventional ferrite devices. Our devices use quantized anomalous Hall materials [1] patterned with circuit structures to realize an isolation of more than 20 dB and a bandwidth of approximately 160 MHz. We will discuss important circuit parameters unique to the chiral topological materials that may shed light to future device design.

[1] A. C. Mahoney et al, Nat. Commun. 8, 1836 (2017).