RT Journal Article T1 Quantum evolution according to real clocks A1 Egusquiza, Iñigo L. A1 Garay Elizondo, Luis Javier A1 Raya, José M. AB We characterize good clocks, which are naturally subject to fluctuations, in statistical terms. We also obtain the master equation that governs the evolution of quantum systems according to these clacks and find its general solution. This master equation is diffusive and produces loss of coherence, Moreover, real clocks can he described in terms of effective interactions that are nonlocal in time. Alternatively, they can be modeled by an effective thermal bath coupled to the system. [S1050-2947(99)04905-7]. PB American Physical Society SN 1050-2947 YR 1999 FD 1999-05 LK https://hdl.handle.net/20.500.14352/59530 UL https://hdl.handle.net/20.500.14352/59530 LA eng NO © 1999 The American Physical Society.We thank C. Barceló, C. Cabrillo, P.F. González-Díaz, G.A. Mena Marugán, and M.A. alle Basagoiti for discussions. J.M.R. is also grateful to J.M. Quintana. We had support from the University of the Basque Country (Project No. UPV 063.310-EB225/95) from Junta de Andalucía, and from DGICYT (Spain) under Project Nos. PB94-0107 and PB93- 0139. NO University of the Basque Country NO Junta de Andalucía NO DGICYT (Spain) DS Docta Complutense RD 21 dic 2025