Using probability current fluctuations to quantify dissipation: A case study

Biological systems consume ATP to maintain nonequilibrium structures that perform crucial functions such as molecular sensing and force generation. Like macroscopic machines, not all of the chemical fuel is converted into useful work. Some of the harvested free energy is lost due to dissipation, and this dissipation is accompanied by broken detailed balance in microscopic state transitions. Previous experiments have successfully detected probability currents in a variety of active biological systems that reflect broken detailed balance. Here, we use a bead-spring model to demonstrate how fluctuations in these probability currents can be utilized to indirectly quantify the dissipation rate. By leveraging the thermodynamic uncertainty relation, we can use statistical fluctuations in currents to bound the dissipation rate, even in high-dimensional systems operating outside a linear-response regime.