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A Chiral Maxwell Demon

Rosa Lopez

salle 208a, aîle sud LPS, bât 510

Maxwells demon is characterized by a hypothetical intelligence capable of sorting hot (fast) and cold (slow) atoms to left and right sub-cavities in a box by simply matchingly inserting and removing an impenetrable wall. This concept was suggested by J.C. Maxwell to highlight that thermodynamics is a macroscopic theory. Under ideal conditions, inserting and removing the wall would not require work and the apparent contradiction with the second law the entropy in the box would be reduced and after the sorting process, work could be extracted from the temperature difference between the sub-cavities has been a source of much debate ever since1. It is now generally believed that this paradox is overcome by the Landauer principle : Deleting the data required for the processing in the demons mind would at least generate entropy S = kBln2 or dissipate heat of at least Q = kBTln2 per bit of information, yielding a net production of entropy.
The demon measures on the system and conditioned on the measurement result it decides its action which is formally nothing but a closed-loop feed-back control scheme. Here, we replace the two sub-cavities of the box by the magnetic field polarity that determines the chirality of the conducting channels. The chiral conductors are coupled to a quasilocalized level state. Depeneding on its occupation dynamics a nearby quantum point contact (QPC) choose one or other field polarity. In this manner the tunneling rates to the conductors are modified depending on the quasibound state occupation.In this work we will address the entropy production, power production, and efficiency when a magnetic feedback is considered.


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