Entropy measurements in mesoscopic circuits: opportunities and limitations

ORAL

Abstract

Recently, Hartman et al. demonstrated the capability to measure the entropy of a quantum dot (QD) containing only a few electrons[1] by detecting shifts in the charge state of the dot with temperature, dN/dT. While the measurement technique in Hartman et al. achieved a high level of accuracy, it lacked versatility because it required the system to be in a weakly coupled state that is thermally broadened, and therefore that charge transitions have the standard cosh2 line-shape of classic Coulomb blockade theory. Here, we show that integrating the dN/dT signal instead of fitting to a particular line-shape enables an entropy measurement of any transition[2], independent of the transition line-shape or even whether the entropy change occurs in the QD itself or another part of the system that is directly coupled to the dot. We demonstrate an entropy measurement for QDs throughout the range from weak to strong coupling to a reservoir. The QD is also sensitive to changes in entropy of other parts of the system, illustrating the potential for this method to be used to measure the entropy of more complex and interesting systems.

[1] Hartman, N. et al. (2018). Nature Physics, 14(11), pp.1083-1086.
[2] Sela, E. et al. (2019). PRL, 123(14).

*Microsoft, CFI, NSERC, SBQMI, and CIFAR.

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Presenters

  • Tim Child

    • Physics and Astronomy, University of British Columbia

Authors

  • Tim Child

    • Physics and Astronomy, University of British Columbia

  • Owen Sheekey

    • Physics and Astronomy, University of British Columbia

  • Nikolaus George Hartman

    • Station Q, Purdue University

  • Silvia Lüscher

    • Physics and Astronomy, University of British Columbia

  • Joshua Folk

    • Physics and Astronomy, University of British Columbia

  • Saeed Fallahi

    • Physics and Astronomy, Purdue University
    • Purdue University
    • Department of Physics and Astronomy, Microsoft Quantum Purdue, Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, USA
    • Physics, Purdue University

  • Geoffrey C. Gardner

    • Department of Physics and Astronomy and Station Q Purdue, Birck Nanotechnology Center, Purdue University
    • Microsoft Quantum at Station Q Purdue
    • Materials Engineering, Purdue University
    • Purdue University
    • Microsoft Quantum at Station Q Purdue, Purdue University

  • Michael Manfra

    • Physics and Astronomy, Purdue Univ
    • Department of Physics and Astronomy and Station Q Purdue, Birck Nanotechnology Center, School of Materials Engineering, School of Electrical and Computer Engineering, Purdue
    • Purdue Univ
    • Purdue University
    • Microsoft Quantum at Station Q Purdue
    • Department of Physics and Astronomy, Birck Nanotechnology Center, Microsoft Quantum Purdue, School og Materials Engineering & School of Electrical and Computer Engineering, P
    • Physics and Astronomy, Purdue University
    • Department of Physics and Astronomy and Station Q Purdue, Purdue University
    • Department of Physics and Astronomy and Microsoft Quantum Purdue, Purdue University, West Lafayette, Indiana 47907 USA
    • Department of Physics and Astronomy, PURDUE UNIVERSITY
    • Department of Physics and Astronomy, Microsoft Quantum Purdue, Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, USA
    • Physics, Purdue University