Informational arrow of time in an extended two-qubit Page-Wooters model

Shamsul Shaari, Jesni (2026) Informational arrow of time in an extended two-qubit Page-Wooters model. Physics Letters A, 577 (1). pp. 1-6. ISSN 0375-9601 E-ISSN 1873-2429

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Abstract

The Page-Wootters (PaW) mechanism explains time as a relational phenomenon within a globally stationary quantum state. In a seminal optical realization, Moreva et al. demonstrated that conditioning on a clock photon yields apparent dynamics, while an external perspective sees stasis. We extend this framework by introducing auxiliary quantum systems that model the observer’s incomplete access to the universe. In a two-qubit PaW toy model, global unitaries act on subsystems of the total state, and tracing out inaccessible degrees of freedom induces effective noise on the observed system. This transformation converts reversible correlations into irreversible entropy growth. We show that the von Neumann entropy of conditional system states increases monotonically across successive clock readings, thereby defining an informational arrow of time. Analysis of dephasing and depolarizing channels illustrates how limited access to the universe naturally yields temporal asymmetry, providing an information-theoretic route to time’s arrow in finite quantum systems.

Item Type:	Article (Letter)
Uncontrolled Keywords:	Page-Wootters mechanism; Quantum information theory; Entropy and decoherence; Informational arrow of time; Finite-dimensional quantum systems
Subjects:	Q Science > QC Physics
Kulliyyahs/Centres/Divisions/Institutes (Can select more than one option. Press CONTROL button):	Kulliyyah of Science Kulliyyah of Science > Department of Physics
Depositing User:	Dr. Jesni Shamsul Shaari
Date Deposited:	24 Feb 2026 09:30
Last Modified:	24 Feb 2026 11:46
Queue Number:	2026-02-Q2201
URI:	http://irep.iium.edu.my/id/eprint/127501

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