A SQUID multiplexer with superconducting-to-normalconducting switches

Abstract

We present a novel multiplexer scheme for time-division multiplexing in superconductingquantum interference device (SQUID) readout configurations. The channels of our SQUIDmultiplexer (SQMUX) are dc SQUID sensors which are connected in series to form acolumn. A superconducting-to-normalconducting switch (SN-switch) in parallel witheach channel is actuated in order to activate or deactivate an individual channelof the column. With a switch in the normalconducting state, its correspondingSQUID channel is active and sensitive to an input signal. When a switch is in thesuperconducting state its corresponding SQUID channel is short-circuited. It isthen insensitive to input signals and does not generate noise. The addressingsequence is chosen such that only one SQUID channel is active at a time. Wesuggest employing SN-switches which are based on dc SQUIDs themselves. Doing soenables the addressing signals of the SN-switches to be applied inductively, i.e.,galvanically isolated. The SQMUX operation is demonstrated in a configuration whereboth the SN-switches and the sensing SQUIDs are based on SQUID series arrays.