An Electronic Measurement of the Boltzmann Constant

TL;DR

This paper reports a highly precise electronic measurement of the Boltzmann constant using Johnson noise thermometry and a superconducting Josephson-junction reference, achieving unprecedented accuracy and reducing systematic errors.

Contribution

First measurement of the Boltzmann constant using an electronic noise thermometry technique with superconducting quantum voltage reference.

Findings

Measured value of k consistent with CODATA

Achieved a relative uncertainty of 13 parts in 10^6

Reduced statistical and systematic uncertainties significantly

Abstract

The Boltzmann constant was measured by comparing the Johnson noise of a resistor at the triple point of water with a quantum-based voltage reference signal generated with a superconducting Josephson-junction waveform synthesizer. The measured value of k = 1.380651(18) \times 10^-23 J/K is consistent with the current CODATA value and the combined uncertainties. This is our first measurement of k with this electronic technique, and the first noise thermometry measurement to achieve a relative combined uncertainty of 13 parts in 10^6. We describe the most recent improvements to our Johnson Noise Thermometer that enabled the statistical uncertainty contribution to be reduced to seven parts in 10^6, as well as the further reduction of spurious systematic errors and EMI effects. The uncertainty budget for this measurement is discussed in detail.