Quasiparticle Generation-Recombination Noise in the Limit of Low Detector Volume

• Published in: IEEE transactions on applied superconductivity Vol. 33; no. 5; pp. 1 - 5
• Main Authors: Li, J., Barry, P. S., Cecil, T., Chang, C. L., Dibert, K., Gualtieri, R., Lisovenko, M., Pan, Z., Yefremenko, V., Wang, G., Zhang, J.
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.08.2023; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Aluminum; Density; detector volume; Detectors; Elementary excitations; Fluctuations; Frequency measurement; Inductance; Inductors; Low temperature; mKIDs; Noise generation; Noise measurement; quasiparticle GR noise; residual quasiparticle density; Resonant frequency; Sensors; Temperature; Temperature measurement
• ISSN: 1051-8223; 1558-2515
• DOI: 10.1109/TASC.2023.3237645

We have measured the quasiparticle generation-recombination (GR) noise in aluminium lumped element kinetic inductors with a wide range of detector volumes at various temperatures. The basic detector consists of meandering inductor and interdigitated capacitor fingers. The inductor volume is varied from 2 to 153 <inline-formula><tex-math notation="LaTeX">\mu \mathrm{m}^{3}</tex-math></inline-formula> by changing the inductor width and length to maintain a constant inductance. We started with measuring the power spectrum density (PSD) of the detectors frequency noise which is a function of GR noise and we clearly observed the spectrum roll off at 10 kHz which corresponds to the quasiparticle lifetime. Using data from a temperature sweep of the resonator frequency we convert the frequency fluctuation to quasiparticle fluctuation and observe its strong dependence on detector volume: detectors with smaller volume display less quasiparticle noise amplitude. Meanwhile we observe a saturated quasiparticle density at low temperature from all detectors as the quasiparticle life time <inline-formula><tex-math notation="LaTeX">\boldsymbol{\tau _{qp}}</tex-math></inline-formula> approaches a constant value at low temperature.