Mathematical analysis of multiplexing techniques for SNSPD arrays

Superconducting single photon detectors (SNSPD) are distinguished by a very high sensitivity, a broad spectral range and a sparse dark count rate. Therefore, arrays of SNSPDs enable novel ultra sensitive imaging applications. The circuit complexity of superconducting detector arrays is supposed to achieve kilopixel range in near future. Hence, in order to improve detector systems there is the necessity to develop multiplexing techniques for flexible scaling of the number of pixels. They are required to keep the number of wires into the cryogenic environment as low as possible. We realized a readout circuit with rapid single flux quantum electronics. All detector output signals were merged to a single output channel. This leads to a loss of spatial resolution of the information that are provided by the single pixels. In order to overcome this effect this work describes a theoretical analysis of two different multiplexing techniques for arrays of SNSPDs and a comparison concerning their applicability in different cases. We developed rules for the usability of each multiplexing technique and verified the results with measurements of a 4-pixel SNSPD array.