Implementation of a microwave readout for scanning superconducting quantum interference devices (SQUIDs)*

In scanning superconducting quantum interference device (SQUID) microscopy a SQUID is rastered close to the surface of a sample to obtain images of the sample’s magnetic properties. In this talk we will discuss a microwave readout for scanning SQUIDs that incorporate an on-chip capacitor as reported in [1]. In this case, the SQUID acts as a flux-dependent inductor, that forms an LC resonant circuit with the on-chip capacitor. The phase and amplitude of microwaves reflected by this circuit encode changes in magnetic flux. We will present our progress towards implementing this microwave readout and characterizing the SQUID noise performance at mK temperatures. The microwave readout holds the promise to both increase our flux sensitivity to below 100nPhi_0/sqrt(Hz) and our measurement bandwidth to several hundreds of MHz [1].
[1] Foroughi et al., APL 112, 252601 (2018)