Entropic_Time_as_a_Relational_Parameter_in_Photonic_Open_Quantum_Systems

We present a mathematically well-defined and experimentally testable frameworkin which an effective notion of time emerges from the monotonic growth of entropy inopen quantum systems. Without postulating a fundamental time variable, we define arelational temporal parameter based on the von Neumann entropy of reduced states.The construction is formalized within completely positive trace-preserving (CPTP)dynamics and applied explicitly to photonic systems, where polarization–frequencycoupling induces controlled decoherence. We establish the conditions for existenceand breakdown of the entropic time parameter, show the rate-independent scaling ofobservable dynamics under entropic reparametrization, and outline a concrete photonicexperiment capable of falsifying the framework. The proposal is fully compatible withstandard quantum mechanics and does not modify its dynamical laws.