Path towards 32-pixel SNSPD array read out with the Kinetic inductance Parametric UP-converter (KPUP)

This work discusses the progress made towards reading out 32 pixels of a Superconducting Nanowire Single Photon Detector (SNSPD) array using the Kinetic inductance Parametric UP-converter (KPUP). KPUPs can be used for frequency-domain readout and multiplexing of sensors commonly used in the astronomical community, such as the Transition Edge Sensor (TES), Metallic Magnetic Calorimeter (MMC), and the Superconducting Nanowire Single Photon Detector (SNSPD). SNSPDs that are multiplexed in the frequency domain can be used in the mid-infrared for direct dark matter detection and exoplanet science. The KPUP is a current-sensitive superconducting microwave resonator that shifts in resonant frequency when perturbed by a signal, and can be read out in a similar method as conventional MKIDs. It has an inverted microstrip geometry, in which the circuit is made using a low-T$_c$ niobium titanium nitride recipe, the dielectric is amorphous silicon, and the ground plane is made out of niobium. The SNSPD is made out of tungsten silicide. We use a superconducting bus to bias all resonators and detectors simultaneously with only a few bias lines going into the cryostat. We will show current response measurements of the KPUP used in the SNSPD readout project, in addition to the next steps involved towards reading out an SNSPD array.