Berlin 2018 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 49: Superconductivity: Superconducting Electronics I

TT 49.10: Vortrag

Mittwoch, 14. März 2018, 12:15–12:30, H 2053

Dc-SQUID readout with high dynamic range and intrinsic frequency-domain multiplexing capability — •Sebastian Kempf, Daniel Richter, Andreas Fleischmann, and Christian Enss — Kirchhoff-Institute for Physics, Heidelberg University, Im Neuenheimer Feld 227, 69120 Heidelberg, Germany.

As a consequence of their periodic flux-to-voltage characteristic direct-current superconducting quantum devices (dc-SQUIDs) are intrinsically non-linear devices. The linear flux range of a dc-SQUID is therefore rather small and in most cases a flux-locked loop (FLL) is used both to increase the dynamic range and to linearize the output signal of the SQUID system. However, for FLL operation the requirements on the digitizer sampling the SQUID signal as well as on the readout electronics are challenging. In addition, individual feedback wires have to be routed to the SQUID setting often a practical limit to the implementation of massive multi-channel SQUID systems.

Within this context we present a novel approach for reading out dc-SQUIDs that provides an easy solution for linearizing the SQUID output signal and for increasing the dynamic range. At the same time it intrinsically allows for implementing frequency-domain multiplexing. In relies on applying a periodic sawtooth-shaped magnetic flux signal to the SQUID. The signal amplitude and repetition rate are chosen such that the input signal is transduced into a phase shift of the related SQUID characteristic. We discuss the basics as well as a comprehensive suitability study of our approach and demonstrate the intrinsic multiplexing capability using a customized multiplexer device.