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Time in Quantum Mechanics

A special issue of Entropy (ISSN 1099-4300). This special issue belongs to the section "Time".

Deadline for manuscript submissions: 27 February 2026 | Viewed by 431

Special Issue Editor


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Guest Editor
Faculty of Engineering and the Institute of Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat Gan 5290002, Israel
Interests: quantum foundations; molecular electronics; nonequilibrium statistical mechanics
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

At the foundations of quantum theory, many unresolved puzzles concerning the basic nature of time exist. In particular, the 'problem of time’ refers to the apparent impossibility of reconciling time as a background parameter of the quantum state with the dynamical concept of time used in relativity theory. The arrow of time in quantum processes does not always appear to be directed towards the future, or in any unique direction whatsoever. These puzzles bear upon many fast-moving fields in physics, including the race for a theory of  quantum gravity, temporal correlations and the theory of measurement.

This Special Issue aims to bring together physicists and philosophers of physics to address all aspects of time in quantum mechanics, including, but not limited to, the following areas: The existence of a time operator in quantum theory, energy–time uncertainty relations, retrocausality, the quantum arrow of time, tunneling times, traversal times in quantum transport, quantum stochastic processes, quantum events, time in quantum gravity, multiple-time quantum mechanics, the two-state vector formalism, the transactional interpretation, timeless quantum theory and the Page–Wootters approach, quantum clocks, quantum reference frames, the persistence of quantum objects through time, presentism vs. eternalism in quantum mechanics, and determinism vs. objective chance.

Dr. Michael Ridley
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

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Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • quantum time
  • quantum gravity
  • time operator
  • retrocausality
  • quantum clocks

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Published Papers (1 paper)

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Research

12 pages, 275 KB  
Article
Relativistic Limits on the Discretization and Temporal Resolution of a Quantum Clock
by Tommaso Favalli
Entropy 2025, 27(10), 1068; https://doi.org/10.3390/e27101068 - 14 Oct 2025
Abstract
We provide a brief discussion regarding relativistic limits on the discretization and temporal resolution of time values in a quantum clock. Our clock is characterized by a time observable chosen to be the complement of a bounded and discrete Hamiltonian that can have [...] Read more.
We provide a brief discussion regarding relativistic limits on the discretization and temporal resolution of time values in a quantum clock. Our clock is characterized by a time observable chosen to be the complement of a bounded and discrete Hamiltonian that can have an equally spaced or a generic spectrum. In the first case, the time observable can be described by a Hermitian operator, and we find a limit in the discretization for the time eigenvalues. Nevertheless, in both cases, the time observable can be described by a POVM, and, by increasing the number of time states, we show how the bound on the minimum time quantum can be reduced and identify the conditions under which the clock values can be treated as continuous. Finally, we find a limit for the temporal resolution of our time observable when the clock is used (together with light signals) in a relativistic framework for the measurement of spacetime distances. Full article
(This article belongs to the Special Issue Time in Quantum Mechanics)
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