This manuscript presents a finite-dimensional Page–Wootters clock–system–environment construction in which entropy growth and long-lived saturation emerge from strictly unitary global dynamics under restricted access. The model provides an explicit relational-time benchmark illustrating entanglement-driven mixedness and equilibration in clock-conditioned reduced states. The work is situated within quantum foundations and relational approaches to time. Supplementary numerical implementations and scripts will be made available following journal publication.
Dednam et al. (Wed,) studied this question.