Quantum Kinetic Uncertainty Relations in Mesoscopic Conductors at Strong Coupling

Abstract: Kinetic Uncertainty Relations (KURs) establish quantum transport precision limits by linking signal-to-noise ratio (SNR) to the system's dynamical activity, valid in the weak-coupling regime where particle-like transport dominates. At strong coupling, quantum coherence challenges the validity of KURs and questions the meaning of the concept of activity itself. Here, we introduce a generalized dynamical activity valid at arbitrary coupling and derive a steady-state quantum KUR (QKUR) expressed in terms of this generalized activity. Explicit expressions are obtained within Green's function and Landauer-B\"uttiker formalisms. This QKUR ensures that uncertainty relations are valid across all coupling strengths, offering a general framework for out-of-equilibrium quantum transport precision analysis. We illustrate these concepts for paradigmatic quantum-coherent mesoscopic devices: a single quantum channel pinched by a quantum point contact and open single- and double-quantum dot systems.