TY  - JOUR
PB  - SciPost Foundation
DO  - 10.21468/SciPostPhys.19.5.127
TI  - Testing Kubo formula on a nonlinear quantum conductor driven far from equilibrium, via power exchanges
PY  - 2025/11/11
UR  - https://www.scipost.org/SciPostPhys.19.5.127
JF  - SciPost Physics
JA  - SciPost Phys.
VL  - 19
IS  - 5
SP  - 127
A1  - Iftikhar, Zubair
AU  - Müller, Jonas
AU  - Mukharsky, Yuri
AU  - Joyez, Philippe
AU  - Roche, Patrice
AU  - Altimiras, Carles
AB  - We present an experimental test of Kubo formula performed on a nonlinear quantum conductor, a Superconductor-Insulator-Superconductor tunnel junction, driven far from equilibrium by a DC voltage bias. We implement the proposal of Lesovik & Loosen [G. B. Lesovik and R. Loosen, J. Exp. Theor. Phys. Lett. 65, 295 (1997)] and demonstrate experimentally that it is possible to extract both the emission and absorption noise of the conductor by measuring the power it exchanges with a linear detection circuit whose occupation is tuned close to vacuum levels. We then compare their difference to the real part of the admittance which is independently measured by coherent reflectometry, finding that Kubo formula holds within experimental accuracy. Last, we show theoretically that the spectral density of power exchanged between a quantum conductor and its linear detection circuit follows a Lesovik & Loosen like formula, even in the presence of strong detection back-action. This result applies as long as the conductor acts as a current source for the detection circuit and the detection circuit is not singular.
ER  -

@Article{10.21468/SciPostPhys.19.5.127,
	title={{Testing Kubo formula on a nonlinear quantum conductor driven far from equilibrium, via power exchanges}},
	author={Zubair Iftikhar and Jonas Müller and Yuri Mukharsky and Philippe Joyez and Patrice Roche and Carles Altimiras},
	journal={SciPost Phys.},
	volume={19},
	pages={127},
	year={2025},
	publisher={SciPost},
	doi={10.21468/SciPostPhys.19.5.127},
	url={https://scipost.org/10.21468/SciPostPhys.19.5.127},
}