An impedance-modulated code-division microwave SQUID multiplexer

Abstract

Large arrays of cryogenic detectors, including transition-edge sensors (TESs) or magnetic micro-calorimeters (MMCs), are needed for future experiments across a wide range of applications. Complexities in integration and cryogenic wiring have driven efforts to develop cryogenic readout technologies with large multiplexing factors while maintaining minimal readout noise. One such example is the microwave SQUID multiplexer (µmux), which couples an incoming TES or magnetic calorimeter signal to a unique GHz-frequency resonance that is modulated in frequency. Here, we present a hybrid scheme combining the microwave SQUID multiplexer with code division multiplexing: the impedance-modulated code-division multiplexer (Z-CDM), which may enable an order of magnitude increase in multiplexing factor particularly for lowbandwidth signal applications.

A Review of X-ray Microcalorimeters Based on Superconducting Transition Edge Sensors for Astrophysics and Particle Physics

“…Much R&D is still needed towards the optimization of the practical implementation of the multiplexing schemes in the focal-plane design to accommodate the complex cryogenic electronics. It is likely that for multiplexing a 100,000-pixels array, a hybrid multiplexing configuration will be required [132].…”

Flux ramp modulation based hybrid microwave SQUID multiplexer

“…Existing SQUID multiplexers rely on time-division 6 , frequency-division using MHz 7,8 or GHz carriers [9][10][11] , code-division 12 or hybrid [13][14][15] multiplexing schemes. Among those, microwave SQUID multiplexers [9][10][11] (µMUXs) are the devices of choice when it comes to read out ultra-large scale detector arrays employing tens or hundreds of thousands of individual detectors.…”

“…Hybrid multiplexing techniques might allow to tackle resulting challenges and potentially even allow to use the channel capacity of the transmission line more efficiently. As an alternative to existing hybrid techniques [13][14][15] , we present a hybrid multiplexing technique combining conventional microwave SQUID multiplexing and flux ramp modulation based cryogenic SQUID multiplexing 8 .…”

Flux ramp modulation based MHz frequency-division dc-SQUID multiplexer

“…Existing SQUID-based multiplexing techniques include time-division multiplexing 3 , frequency-division multiplexing using MHz 4 and GHz 5 carriers, codedivision multiplexing 6 as well as hybrid multiplexing schemes 7,8 . But despite of the great success and their numerous advantages, they suffer from minor drawbacks a) sebastian.kempf@kit.edu that practically limit their application: State-of-the-art MHz frequency-division multiplexers, for example, employ large on-chip passive filter circuits limiting the overall channel count per given chip area.…”

“…We thus had to deal with voltage transients during the ramp resets deteriorating the phase determination and increasing the white noise level. To avoid this kind of complication for future devices, we plan to use a similar wiring strategy as presently used for code-division multiplexing 8 . In particular, we are going to build twodimensional M × N multiplexers for which the N modulation coils within a row and the M SQUIDs within a column are serially connected to each other.…”