Thermodynamic Uncertainty Relation in Hybrid Normal-Superconducting Systems: The Role of superconducting coherence

Abstract: We study the violation of thermodynamic uncertainty relations (TURs) in hybrid superconducting systems consisting of one superconducting and two normal leads coupled to a central region containing localized levels, focusing on the role of quantum coherence. We first study the simplest setup yielding TUR violations, where the central region is a single-level quantum dot and only one normal lead is connected. In addition to the {\it classical} TUR, we consider an alternative formulation recently derived for coherent conductors. We find even the latter TUR is violated (although by a smaller extent) as a result of the macroscopic coherence related to the superconducting condensate. To support this conclusion, we connect the second normal lead as a dephasing probe, demonstrating that the violation is directly correlated with the superconducting coherence, as measured by the dot's pair amplitude. When the central region is a Cooper-pair splitter, crossed Andreev processes introduce nonlocal superconducting correlations that further enhance the quantum-TUR violation.