Parametric amplifier halves readout noise from superconducting sensors

Superconducting sensors are used to detect some of the faintest signals in astronomy, X-ray material analysis, and nuclear monitoring. These sensors are cooled to fractions of a degree above absolute zero and can resolve signals from individual photons. Outputs from the sensors are run through a microwave multiplexer and amplified, typically by a high-electron-mobility transistor (HEMT) amplifier. However, the amplifier introduces noise, limiting the amount of useful information obtainable through the detector.

Malnou et al. reduced the amplifier noise by adding a kinetic-inductance traveling-wave parametric amplifier (KITWPA) as the first amplifier before the HEMT. This halves the flux noise from the multiplexer and could lead to future, more powerful sensor systems.

“The KITWPA relies on parametric amplification, which can approach the so-called ‘quantum limit’ that imposes a lower bound on the noise added during the amplification process,” said author Maxime Malnou. “Compared to a HEMT, a parametric amplifier adds about a factor of 10 less power noise.”

The team developed this layout for use in transition-edge sensors, where the noise reduction would allow for more sensors to cover a given frequency band, reducing the readout cost. The KITWPA can also be used with magnetic metallic calorimeters, enabling them to be multiplexed for better sensitivity.

The authors hope to further improve the amplifier’s performance by integrating external microwave components onto the amplifier chip and implementing a tone-tracking algorithm as part of the electronics processing.

“The next big step is to show a successful readout of tens of sensors, with the KITWPA as the first amplifier,” said Malnou. “It would address new and interesting questions, such as the level of cross-talk between the sensors.”

Source: “Improved microwave SQUID multiplexer readout using a kinetic-inductance traveling-wave parametric amplifier,” by Maxime Malnou, John A. B. Mates, Michael Robert Vissers, Leila R. Vale, Daniel R. Schmidt, Douglas A. Bennett, Jiansong Gao, and Joel N. Ullom, Applied Physics Letters (2023). The article can be accessed at https://doi.org/10.1063/5.0149646 .