Optimal engine performances can be accomplished by quantum effects. Here we explore two routes toward ideal engines, namely (1) quantum systems that operate as hybrid machines being able to perform more than one useful task and (2) the suppression of fluctuations in doing such tasks. For classical devices, the absence of fluctuations is conditioned by a high entropy production, as dictates the thermodynamic uncertainty relations. Here we generalize such relations for multiterminal conductors that operate as hybrid thermal machines. These relations are overcome in quantum conductors as we show for a double quantum dot contacted to normal metals and a reservoir being a generator of entangled Cooper pairs.

R.L. acknowledges the financial support by the Grants No. PDR2020/12 sponsored by the Comunitat Autonoma de les Illes Balears through the Direcció General de Política Universitaria i Recerca with funds from the Tourist Stay Tax Law ITS 2017‐006, and No. PID2020-117347GB-I00 funded by MCIN/AEI/10.13039/501100011033, and No. LINKB20072 from the CSIC i-link program 2021. K.W.K. acknowledges that this research was supported by the Chung-Ang University Research Grants in 2021 and Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (No. 2021R1F1A1055797).

Peer reviewed