Quantum· 2026Q1
Time symmetry in quantum theories and beyond
- 1citations
- Q1SCImago
- 2026year
Short summary
A new quantum process theory, QPhys, is introduced, treating classical systems as internal to quantum theory and offering three methods to incorporate time symmetry.
AI-generated from the title and abstract; the full text is not read.
Key points
- Introduces QPhys, a process theory for quantum physics that integrates classical systems.
- Presents three distinct methods for incorporating time symmetry into QPhys.
- Develops a toy model for particle physics using extended causality and retrocausality for particles and antiparticles.
- Proposes modifications to composition rules or processes in a supertheory to ensure physical predictions without causality constraints.
AI-generated from the title and abstract; the full text is not read.
Abstract
There exists a stark tension among different formulations of quantum theory as some are inherently time-symmetric while others are time-asymmetric. This tension is crisply captured when considering physical theories as theories of processes. We present the process theory of quantum physics, QPhys, which treats classical systems as internal to quantum theory. We provide three ways to incorporate time symmetry in QPhys. The first restricts the process theory of QPhys to one that satisfies an additional retrocausality constraint. The second is a novel approach, which extends the notions of causality and retrocausality to apply to systems along with processes. Utilizing this approach, we create a toy model for particle physics , where the causal and retrocausal systems correspond to particles and anti-particles respectively. The third approach extends QPhys to a supertheory that satisfies neither a causality nor a retrocausality constraint. To avoid unphysical predictions we modify either its composition rule or its processes.
The authors' abstract, as published at the source. Quantum, 2026 · DOI ↗
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Field: Atomic and Molecular Physics, and Optics
Atomic and Molecular Physics, and OpticsPhysics and Astronomy