Response to “The measurement postulates of quantum mechanics are not redundant”
1London Centre for Nanotechnology and Department of Computer Science, University College London, United Kingdom
2Institute for Quantum Optics and Quantum Information, Austrian Academy of Sciences, Boltzmanngasse 3, A-1090 Vienna, Austria
3Perimeter Institute for Theoretical Physics, Waterloo, ON N2L 2Y5, Canada
| Published: | 2025-01-14, volume 9, page 1592 |
| Editor: | Alexander Wilce |
| Eprint: | arXiv:2309.01650v4 |
| Doi: | https://doi.org/10.22331/q-2025-01-14-1592 |
| Citation: | Quantum 9, 1592 (2025). |
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Abstract
Adrian Kent has recently presented a critique [1] of our paper [2] in which he claims to refute our main result: the measurement postulates of quantum mechanics can be derived from the rest of postulates, once we assume that the set of mixed states of a finite-dimensional Hilbert space is finite-dimensional. To construct his argument, Kent considers theories resulting from supplementing quantum mechanics with hypothetical ``post-quantum'' measurement devices. We prove that each of these theories contains pure states (i.e. states of maximal knowledge) which are not rays of the Hilbert space, in contradiction with the ``pure state postulate'' of quantum mechanics. We also prove that these alternatives violate the finite-dimensionality of mixed states. Each of these two facts separately invalidates the refutation. In this note we also clarify the assumptions used in [2] and discuss the notions of pure state, physical system, and the sensitivity of the structure of the state space under modifications of the measurements or the dynamics.
► BibTeX data
► References
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https://doi.org/10.48550/arXiv.2307.06191
arXiv:2307.06191
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Cited by
[1] Vincenzo Fiorentino and Stefan Weigert, "Beyond the projection postulate and back: Quantum theories with generalized state-update rules", Physical Review A 113 1, 012204 (2026).
[2] Adrian Kent, "The measurement postulates of quantum mechanics are not redundant", Quantum 9, 1749 (2025).
[3] Zachary P. Bradshaw, Jeffrey J. Dale, and Ethan N. Evans, "Introduction to quantum error correction with stabilizer codes", Annals of Physics 487, 170353 (2026).
[4] Samuel Fedida and Adrian Kent, "Thermodynamics of readout devices and semiclassical gravity", Physical Review A 113 1, 012214 (2026).
[5] Adrian Kent, "Fundamental physics, existential risks and human futures", Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 383 2296, 20230376 (2025).
[6] Alireza Tavanfar, Sahar Alipour, and Ali T. Rezakhani, "Does Quantum Mechanics Breed Larger, More Intricate Quantum Theories? The Case for Experience-Centric Quantum Theory and the Interactome of Quantum Theories", Universe 11 5, 162 (2025).
[7] Blake C. Stacey, "Contradictions or Curiosities? On Kent's Critique of the Masanes--Galley--Müller Derivation of the Quantum Measurement Postulates", arXiv:2405.17733, (2024).
The above citations are from Crossref's cited-by service (last updated successfully 2026-08-09 22:30:56) and SAO/NASA ADS (last updated successfully 2026-08-09 22:30:58). The list may be incomplete as not all publishers provide suitable and complete citation data.
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