Skip to content
DraconiticResearch
Search Sources API
190,332 studies31 sourcesUpdated 20 min ago
Peer-reviewedCC BY 4.0Quantum

Time symmetry in quantum theories and beyond

  • John H. Selby1
  • Maria E. Stasinou2,3
  • Stefano Gogioso4,5
  • Bob Coecke6,7,8
8 affiliations
  1. 1International Centre for Theory of Quantum Technologies, University of Gdańsk, 80-308 Gdańsk, Poland
  2. 2Research Center `ATHENA', Patras, Greece
  3. 3Quantum Neural Technologies S.A.
  4. 4Spooqy Ltd, London, UK
  5. 5University of Oxford, Oxford, UK
  6. 6Relational Intelligence Ltd, Oxford, UK
  7. 7Wolfson College, University of Oxford, Oxford, UK
  8. 8Perimeter Institute, Waterloo, Ontario, Canada
Open at sourcePDFDOICite

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.

Related

  1. Theory of steady states for Lindblad equations beyond time-independence: Classification, uniqueness and symmetry
    Hironobu Yoshida, Ryusuke Hamazaki
    Physical Review XPeer-reviewedPublisher termsAtomic, molecular & optical physicsCrossref
  2. MORE Thermal Gauge Theories at Finite θ and μ from Real-Time Quantum Simulation
    Henry Lamm
    arXivPreprintCC BY 4.0Full textHigh-energy & particle physicsQuantum physics & quantum informationarXiv
  3. Boundary Quantum Knizhnik-Zamolodchikov Equations and Integrability of Quantum Field Theories with Time-Dependent Bulk and Boundary Coupling Strengths
    Parameshwar R. Pasnoori
    arXivPreprintCC BY 4.0Full textMathematical physicsCondensed matterarXiv
  4. Time-dependent integrable quantum field theories with dynamical boundaries
    Pradip Kattel
    arXivPreprintCC BY 4.0Full textMathematical physicsCondensed matterarXiv
  5. Type-II quantum spin Hall insulator without time-reversal symmetry
    Panjun Feng, Chaoyang Tan, Xun-Wang Yan +5
    Science China Physics Mechanics and AstronomyPeer-reviewedLicence not statedFull text8 citedAtomic, molecular & optical physicsCondensed matterOpenAlex

Cite

BibTeXRIS
BibTeX
@article{selby2026time,
  title = {{Time symmetry in quantum theories and beyond}},
  author = {John H. Selby and Maria E. Stasinou and Stefano Gogioso and Bob Coecke},
  journal = {Quantum},
  year = {2026},
  month = sep,
  doi = {10.22331/q-2026-09-30-2221},
  url = {https://quantum-journal.org/papers/q-2026-09-30-2221/},
  note = {CC BY 4.0},
}
RIS
TY  - JOUR
TI  - Time symmetry in quantum theories and beyond
AU  - John H. Selby
AU  - Maria E. Stasinou
AU  - Stefano Gogioso
AU  - Bob Coecke
PY  - 2026
DA  - 2026/09/30
JO  - Quantum
DO  - 10.22331/q-2026-09-30-2221
UR  - https://quantum-journal.org/papers/q-2026-09-30-2221/
AB  - 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.
SN  - 2521-327X
ER  -