I study an autonomous quantum Maxwell's demon based on two exchange-coupledquantum dots attached to the spin-polarized leads. The principle of operationof the demon is based on the coherent oscillations between the spin states ofthe system which act as a quantum iSWAP gate. Due to the operation of the iSWAPgate one of the dots acts as a feedback controller which blocks the transportwith the bias in the other dot, thus inducing the electron pumping against thebias; this leads to the locally negative entropy production. Operation of thedemon is associated with the information transfer between the dots, which isstudied quantitatively by mapping the analyzed setup onto the thermodynamicallyequivalent auxiliary system. The calculated entropy production in a singlesubsystem and information flow between the subsystems are shown to obey a localform of the second law of thermodynamics, similar to the one previously derivedfor classical bipartite systems.
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