Janine Splettstösser is exploring the limits of precision in quantum heat engines, focusing on how fluctuations impact power production at small scales. Splettstösser’s recent results reveal that thermodynamic and kinetic constraints govern these fluctuations, a critical consideration for devices operating far from equilibrium. “In small-scale thermodynamic devices, fluctuations play an important role,” she notes, challenging conventional thermodynamics where fluctuations are typically negligible. This work addresses a key difficulty in applying established theories, developed for weakly coupled systems, to steady-state thermoelectric engines with strong coupling to their surroundings.

Thermodynamic and Kinetic Uncertainty Relations Constrain Quantum Engine Fluctuations

Fluctuation-dissipation theorems, tools for linking fluctuations to average output, become less accurate when applied to systems operating far from equilibrium; steady-state thermoelectric heat engines exemplify this limitation. Existing thermodynamic and kinetic uncertainty relations (TURs and KURs) were primarily developed for weakly coupled open quantum systems, creating a mismatch with the strong coupling characteristic of practical heat engine designs. Janine Splettstösser’s recent work addresses this challenge by investigating how thermodynamic properties inherently constrain fluctuations within these devices.

Splettstösser’s results demonstrate that fluctuations in small-scale thermodynamic devices are not unbounded, but rather governed by both thermodynamic and kinetic limitations, a departure from classical expectations. These constraints have direct implications for understanding power production using quantum systems subjected to temperature differences and potentially guiding future designs toward maximizing efficiency within inherent physical boundaries. Splettstösser presented these findings at the IFIMAColloquium, detailing the interplay between constraints and fluctuations in these complex systems.