We are developing X-ray microcalorimeters as a backup option for the baseline detectors in the X-IFU instrument on board the ATHENA space mission led by ESA and to be launched in the early 2030s. 5 × 5 mixed arrays with TiAu transition-edge sensor (TES), which have different high aspect ratios and thus high resistances, have been designed and fabricated to meet the energy resolution requirement of the X-IFU instrument. Such arrays can also be used to optimize the performance of the frequency domain multiplexing (FDM) readout and lead to the final steps for the fabrication of a large detector array. In this work, we present the experimental results from tens of the devices with an aspect ratio (length-to-width) ranging from 1-to-1 up to 6-to-1, measured in a single-pixel mode with a FDM readout system developed at SRON/VTT. We observed a nominal energy resolution of about 2.5 eV at 5.9 keV at bias frequencies ranging from 1 to 5 MHz. These detectors are proving to be the best TES microcalorimeters ever reported in Europe, intending to meet the requirements of the X-IFU instrument, but also those of other future challenging X-ray space missions, fundamental physics experiments, plasma characterization and material analysis.

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Cryogenic CMOS, or cryo-CMOS circuits and systems, are emerging in VLSI design for many applications, in primis quantum computing. Fault-tolerant quantum bits (qubits) in surface code configurations, one of the most accepted implementations in quantum computing, operate in deep sub-Kelvin regime and require scalable classical control circuits. In this paper we advocate the need for a new generation of deep-submicron CMOS circuits operating at deep-cryogenic temperatures to achieve the performance required in a fault-tolerant qubit system. We outline the challenges and limitations of operating CMOS in near-zero Kelvin regimes and we propose solutions. The paper concludes with several examples showing the suitability of integrating fault-tolerant.qubits with CMOS.@en

We propose a classical infrastructure for a quantum computer implemented in CMOS. The peculiarity of the approach is to operate the classical CMOS circuits and systems at deep-cryogenic temperatures (cryoCMOS), so as to ensure physical proximity to the quantum bits, thus reducing thermal gradients and increasing compactness. CryoCMOS technology leverages the CMOS fabrication infrastructure and exploits the continuous effort of miniaturization that has sustained Moore's Law for over 50 years. Such approach is believed to enable the growth of the number of qubits operating in a fault-tolerant fashion, paving the way to scalable quantum computing machines.@en