A quintet of quandaries: five no-go theorems for Relational Quantum Mechanics

Pienaar, Jacques L.

doi:10.48550/arxiv.2107.00670

Cited by 5 publications

(13 citation statements)

References 28 publications

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“…Pienaar's [1] presents arguments against two ideas: that (i) RQM preserves certain classical relativistic intuitions about relations and (ii) it preserves the idea that consistency can be established between different observers' accounts. Both conclusions are correct: (i) RQM does not preserve certain classical relativistic intuitions about relations: it extends them and makes them more radical ("facts are relative").…”

Section: Discussionmentioning

confidence: 99%

“…It is better to reserve the use of operational expressions such as "observer" and "measurement" to those specific situations where there is enough decoherence to underpin stability, for instance, when there is a scientist making observations, or a macroscopic system storing memory. 1 Terminology aside, the actual content of RQM:1 is that we assume something can happen relative to any system-not only measuring apparata or "observers" that are special in any sense.…”

Section: Rqm:4mentioning

confidence: 99%

“…Clarified this (subtle) point, there remains 4 in Pienaar's [1] an objection: this proliferation of disjoint universes is not motivated by observations, nor does it serve any explanatory purpose.…”

Section: Are Relative Facts Needed?mentioning

confidence: 99%

“…But it contains one misstep: a misrepresentation of the claims RQM:5 and RQM:6 (see below). This misrepresentation is common to both [2] and [1], and regards the meaning of the quantum state. In RQM, the quantum state is not a representation of reality: it is always a relative state and is only a mathematical tool used to predict probabilities of events relative to a given system.…”

Section: Introductionmentioning

confidence: 99%

“…Two recent papers, one by Jacques Pienaar [1] and one by Časlav Brukner [2], present insightful observations and objections on the Relational interpretation of Quantum Mechanics (RQM, also known as relational quantum mechanics) [3][4][5][6]. Here we discuss these papers in detail.…”

Section: Introductionmentioning

confidence: 99%

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Relational Quantum Mechanics is about Facts, not States: A reply to Pienaar and Brukner

Di Biagio,

Rovelli

2021

Preprint

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Section: Discussionmentioning

confidence: 99%

Section: Rqm:4mentioning

confidence: 99%

Section: Are Relative Facts Needed?mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Relational Quantum Mechanics is about Facts, not States: A reply to Pienaar and Brukner

Di Biagio,

Rovelli

2021

Preprint

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Perspectival Quantum Realism

Dieks

2022

Found Phys

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The theories of pre-quantum physics are standardly seen as representing physical systems and their properties. Quantum mechanics in its standard form is a more problematic case: here, interpretational problems have led to doubts about the tenability of realist views. Thus, QBists and Quantum Pragmatists maintain that quantum mechanics should not be thought of as representing physical systems, but rather as an agent-centered tool for updating beliefs about such systems. It is part and parcel of such views that different agents may have different beliefs and may assign different quantum states. What results is a collection of agent-centered perspectives rather than a unique representation of the physical world. In this paper we argue that the problems identified by QBism and Quantum Pragmatism do not necessitate abandoning the ideal of representing the physical world. We can avail ourselves of the same puzzle-solving strategies as employed by QBists and pragmatists by adopting a perspectival quantum realism. According to this perspectivalism (close to the relational interpretation of quantum mechanics) objects may possess different, but equally objective properties with respect to different physically defined perspectives. We discuss two options for such a perspectivalism, a local and a nonlocal one, and apply them to Wigner’s friend and EPR scenarios. Finally, we connect quantum perspectivalism to the recently proposed philosophical position of fragmentalism.

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On Relationalist Reconstructions of Quantum Theory

Stacey¹

2021

Preprint

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Why I'm not happy with how Relational Quantum Mechanics has addressed the reconstruction of quantum theory, and why you shouldn't be either.One appealing feature of Carlo Rovelli's proposal for "Relational Quantum Mechanics" [1] is that it offered a challenge for those who prefer technical work over slinging sentences: the reconstruction of quantum theory from information-theoretic principles. This appeal was witnessed by the means through which I first learned of RQM, a Wikipedia page written by a fan in 2006 [2] and since trimmed heavily on the grounds that it said many things not explicitly stated in the literature already. (As David Mermin once said, "Writing on Wikipedia is like writing on water.") Of course, the idea of rebuilding quantum theory on a better foundation long predates Rovelli. In some fashion, it is at least as old as Birkhoff and von Neumann's explorations. We could also mention Mackey's challenge and its answer by Gleason, and John Wheeler's suggested research project for his more promising undergraduates: "Derive quantum theory from an information theoretic principle!" [3]. But Rovelli's article, along with the 2000 Montreal workshop and Hardy's derivation not long after [4,5], served to mainstream the question for the current century.A few days after I posted a first version of these notes online (https://www.sunclipse. org/?p=3016), Muciño, Okon and Sudarsky independently filed a lengthy critique of RQM on the arXiv [6]. As will become clear over the following sections, I tend to agree with some of their criticisms. However, the overall tone here will be closer to that of Pienaar [7,8], who evaluates RQM from as sympathetic a position as possible, taking as given the legitimacy of "Copenhagen-ish" interpretations and seeing how RQM fares when evaluated in that context. Moreover, my emphasis will be different from that of all these criticisms, as I will focus upon the reconstruction side of Rovelli's proposal. Has it borne fruit? When later work claimed to find inspiration in it, how close was the relationship, and did RQM really hold up its end of the deal? I. ROVELLI'S RECONSTRUCTION POSTULATESRovelli's preliminary stab at reconstructing quantum theory from information-theoretic principles has some appealing features but also a few things going against it, which can be illustrated by quoting the first two postulates that Rovelli proposes. R1. "There is a maximum amount of relevant information that can be extracted from a system."R2. "It is always possible to acquire new information about a system."These have a little of the feel of Einstein's postulates for special relativity, in that they seemingly run the risk of contradicting each other [9]. However, in special relativity, resolving this dramatic tension required overhauling our notions of space and time, whereas it is possible to have R1 and R2 coexist in a much more mundane way. For example, the

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A quintet of quandaries: five no-go theorems for Relational Quantum Mechanics

Cited by 5 publications

References 28 publications

Relational Quantum Mechanics is about Facts, not States: A reply to Pienaar and Brukner

Relational Quantum Mechanics is about Facts, not States: A reply to Pienaar and Brukner

Perspectival Quantum Realism

On Relationalist Reconstructions of Quantum Theory

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