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Probing quantum fluctuations of single electronic channels in model interacting systems

Periodic Reporting for period 4 - NSECPROBE (Probing quantum fluctuations of single electronic channels in model interacting systems)

Reporting period: 2019-11-01 to 2021-04-30

The issue adressed by this project is to understand out-of-equilibrium non-linear dynamics of complex interacting systems. In practice this investigation will be implemented experimentally using quantum transport tools.

This issue is important for society since many striking, and potentially usefull, properties of matter arise from many-body quantum interacting systems. Moreover it is also important to understand out-of-equilibrium dynamics since when we want to make use of a physical system to act upon another one, we usually drive out of equilibrium. Finally, the non-linear properties (arising from the interactions in play) are particularly usefull to act on physical signals (amplification, frequancy conversion, etc...). However it is very difficult to theoretically grasp such complex quantum interacting systems, for this reason we believe that providing an experimental platform enabling accurate out-of-equilibrium measurements on model interacting systems realised in quantum circuits will be able to help.

The overall objective is to test experimentally some general fluctuation-dissipation relations which should hold for a vast class of out-of-equilibrium system. In the way to achieve this goal, we will develop novel experimental methods to measure the finite frequency dynamics of non-linear conductors, implemented in 2D electron gases and having different underlying physics. This effort will help understanding the impact of Coulomb interaction in the electronic properties of matter confined in low dimensions.
We have tested and equipped a dilution fridge in order to be able to perform the measurements planned. Special requirements are low temperatures of about 15mK, high magnetic fields up 14T, and having a number of DC lines and RF lines.

We have designed and fabricated high impedance RF resonators made from planar coil, which will allow us to efficiently couple 50 Ohm transmission lines, where RF signals can be routed and detected, to 25 kiloOhm quantum conductors whose fast dynamics we want to probe.

We have developed a new theoretical approcah allowing us to understand some measurement backaction effects of the surrounding measurement circuit upon the properties of the quantum conductor. We have also developped new tools allowing us to understand what kind of information can be extracted from the radiation emitted from a quantum conductor.
We hope to provide a quantitative characterization of out-equilibriul dynamics of complex conductors. And a possible experimental validation of a theoretically predicted general property of driven dissipative systems.
A quantum conductor interacting with its detection circuit