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Practical realisation of the kelvin by Johnson noise thermometry



Horst Rogalla, D Rod White, Jifeng Qu, Samuel P. Benz, Christof Gaiser, Weston L. Tew, Nathan Flowers-Jacobs, Kevin J. Coakley, Alessio Polarollo, Chiharu Urano


Johnson noise thermometry (JNT) is a purely electronic method of thermodynamic thermometry. In primary JNT, the temperature is inferred from a comparison of the Johnson noise voltage of a resistor at the unknown temperature with a pseudo-random noise synthesized by a quantum-based voltage-noise source (QVNS). The advantages of the method are that it relies entirely on electronic measurements, and it can be used over a wide range of temperatures due to the ability of the QVNS to generate programmable, scalable, and accurate reference signals. The disadvantages are the requirement of cryogenic operation of the QVNS, the need to match the frequency responses of the leads of the sense resistor and the QVNS, and long measurement times. This review collates advice on current best practice for a primary Johnson noise thermometer based on the switched correlator and QVNS. The method achieves an uncertainty of about 1 mK near 300 K and is suited to operation between 4 K and 700 K.


International System of Units, kelvin, Josephson effect, Mise en Pratique (MeP), Temperature, Temperature scale, Thermometry, Thermodynamic temperature, Voltage standard, Johnson noise


Rogalla, H. , White, D. , Qu, J. , Benz, S. , Gaiser, C. , Tew, W. , Flowers-Jacobs, N. , Coakley, K. , Polarollo, A. and Urano, C. (2024), Practical realisation of the kelvin by Johnson noise thermometry, Metrologia, [online],, (Accessed May 26, 2024)


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Created February 15, 2024, Updated May 9, 2024