Ultrasensitive Bolometry in Quantum Thermodynamics Experiments

Ultrasensitive Bolometry in Quantum Thermodynamics Experiments - Featured

Title: Ultrasensitive Bolometry in Quantum Thermodynamics Experiments
When: Thursday, June 27, 2024, 12:00
Place: Department of Theoretical Condensed Matter Physics, Faculty of Sciences, Module 5, Seminar Room (5th Floor)
Speaker: Bayan Karimi Pico group, QTF Centre of Excellence, Department of Applied Physics, Aalto University, 00076 Aalto, Finland.

In this talk, we present both experimentally and theoretically our work on phenomena and devices in quantum thermodynamics realized by superconducting and metal circuits on a chip at low millikelvin temperatures. In these modern superconducting circuits, which form open quantum systems, we couple them to engineered heat baths. Besides fundamental interest, this approach allows us to develop different types of quantum thermodynamic devices like quantum heat valves and rectifiers, refrigerators and heat engines, quantum thermometers, and ultrasensitive calorimeters [1,2,3]. In this talk we will describe our recent work in these directions. Importantly, we demonstrate detection of equilibrium fluctuations of temperature in a system of about 100 million electrons exchanging energy with phonon bath at a fixed temperature [4]. We show theoretically that this detector is capable of observing single microwave photons in a continuous manner [5]. We propose a cross-correlation measurement technique to enhance the sensitivity of the quantum detector [6]. We describe on-going experiments where we observe Josephson radiation by a single voltage biased junction by a bolometer. We design and build an engineered on-chip reservoir that acts as an efficient bolometer for detecting the Josephson radiation under non-equilibrium (biased) conditions. The bolometer converts ac Josephson current at microwave frequencies, up to about 100 GHz, into a measurable dc temperature rise. The present experiment demonstrates an efficient, wide-band, thermal detection scheme of microwave photons and provides a sensitive detector of Josephson dynamics beyond the standard conductance measurements [7]. At the end we present our experimental setup and preliminary results for qubit bolometry [8].


  1. Jukka P. Pekola and Bayan Karimi, Rev. Mod. Phys. 93, 041001 (2021).
  2. Alberto Ronzani et al., Nat. Phys. 14, 991 (2018).
  3. Jorden Senior et al., Commun. Phys. 3, 40 (2020).
  4. B. Karimi et al., Nat. Commun. 11, 367 (2020).
  5. B. Karimi and J. P. Pekola, Phys. Rev. Lett. 124, 170601 (2020).
  6. J. P. Pekola and B. Karimi, Phys. Rev. X 12, 011026 (2022).
  7. Bayan Karimi, Gorm Ole Steffensen, Andrew P. Higginbotham, Charles M. Marcus, Alfredo Levy Yeyati, Jukka P. Pekola, arXiv:2402.09314.
  8. B. Karimi, Ze-Yan Chen, Kuan-Hsun Chiang, et al. (in preparation).
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