arXiv subjects

Peter W. Evans

Publications and source records attributed to Peter W. Evans.

9 recordsLinked to original sources

arXiv2025

Is quantum mechanics merely a theory for us?

This paper develops an agent-centric account of measurement that treats the preferred-basis problem is fundamentally perspectival. On this view, the system--apparatus--environment decomposition and the observables that are apt to become classically robust are determined by the physical constitution and epistemic constraints of an embodied class of agents. Decoherence then stabilises those agent-specified observables, yielding facts that are stable for us without positing an absolute, observer-independent basis. On this picture, `measurements' are public not because they are metaphysically privileged, but because agents like us share the relevant sensorimotor and operational structure. I motivate this account through a discussion of two recent no-go results for relational quantum mechanics (RQM) (Brukner,2021;Pienaar,2021), and a subsequent response (DiBiagio and Rovelli, 2022): my aim is not to defend RQM per se, but to refine the relational insight with a principled account of basis selection rooted in embodiment. I provide a phenomenological gloss, drawing on body-schema considerations, to argue that quantum mechanics is best understood as an idiosyncratically human description of interactions with the physical world -- a structurally constrained, agent-indexed framework within which classicality emerges.

quant-ph↗

arXiv2023

How to engineer a quantum wavefunction

In a conventional experiment, scientists typically aim to learn about target systems by manipulating source systems of the same material type. In an analogue quantum simulation, by contrast, scientists typically aim to learn about target quantum systems of one material type via an experiment on a source quantum system of a different material type. In this paper, we argue that such inferences can be justified by reference to source and target quantum systems being of the same empirical type. We illustrate this novel experimental practice of wavefunction engineering with reference to the example of Bose-Hubbard systems.

quant-ph↗

arXiv2020

A sideways look at faithfulness for quantum correlations

Despite attempts to apply the lessons of causal modelling to the observed correlations typical of entangled bipartite quantum systems, Wood and Spekkens argue that any causal model purporting to explain these correlations must be fine tuned; that is, it must violate the assumption of faithfulness. The faithfulness assumption is a principle of parsimony, and the intuition behind it is basic and compelling: when no statistical correlation exists between the occurrences of a pair of events, we have no reason for supposing there to be a causal connection between them. This paper is an attempt to undermine the reasonableness of the assumption of faithfulness in the quantum context. Employing a symmetry relation between an entangled bipartite quantum system and a `sideways' quantum system consisting of a single photon passing sequentially through two polarisers, I argue that Wood and Spekkens' analysis applies equally to this sideways system. If this is correct, then the consequence endorsed by Wood and Spekkens for an ordinary entangled quantum system amounts to a rejection of a causal explanation in the sideways, single photon system, too. Unless rejecting this causal explanation can be sufficiently justified, then it looks as though the sideways system is fine tuned, and so a violation of faithfulness in the ordinary entangled system may be more tolerable than first thought. Thus extending the classical `no fine-tuning' principle of parsimony to the quantum realm may well be too hasty.

quant-ph↗

arXiv2020

What can bouncing oil droplets tell us about quantum mechanics?

A recent series of experiments have demonstrated that a classical fluid mechanical system, constituted by an oil droplet bouncing on a vibrating fluid surface, can be induced to display a number of behaviours previously considered to be distinctly quantum. To explain this correspondence it has been suggested that the fluid mechanical system provides a single-particle classical model of de Broglie's idiosyncratic 'double solution' pilot wave theory of quantum mechanics. In this paper we assess the epistemic function of the bouncing oil droplet experiments in relation to quantum mechanics. We find that the bouncing oil droplets are best conceived as an analogue illustration of quantum phenomena, rather than an analogue simulation, and, furthermore, that their epistemic value should be understood in terms of how-possibly explanation, rather than confirmation. Analogue illustration, unlike analogue simulation, is not a form of 'material surrogacy', in which source empirical phenomena in a system of one kind can be understood as 'standing in for' target phenomena in a system of another kind. Rather, analogue illustration leverages a correspondence between certain empirical phenomena displayed by a source system and aspects of the ontology of a target system. On the one hand, this limits the potential inferential power of analogue illustrations, but, on the other, it widens their potential inferential scope. In particular, through analogue illustration we can learn, in the sense of gaining how-possibly understanding, about the putative ontology of a target system via an experiment. As such, the potential scientific value of these extraordinary experiments is undoubtedly a significant one.

physics.hist-ph↗

arXiv2020

On the Limits of Experimental Knowledge

To demarcate the limits of experimental knowledge we probe the limits of what might be called an experiment. By appeal to examples of scientific practice from astrophysics and analogue gravity, we demonstrate that the reliability of knowledge regarding certain phenomena gained from an experiment is not circumscribed by the manipulability or accessibility of the target phenomena. Rather, the limits of experimental knowledge are set by the extent to which strategies for what we call `inductive triangulation' are available: that is, the validation of the mode of inductive reasoning involved in the source-target inference via appeal to one or more distinct and independent modes of inductive reasoning. When such strategies are able to partially mitigate reasonable doubt, we can take a theory regarding the phenomena to be well supported by experiment. When such strategies are able to fully mitigate reasonable doubt, we can take a theory regarding the phenomena to be established by experiment. There are good reasons to expect the next generation of analogue experiments to provide genuine knowledge of unmanipulable and inaccessible phenomena such that the relevant theories can be understood as well supported.

physics.hist-ph↗

arXiv2016

$Ψ$-Epistemic Quantum Cosmology?

This paper provides a prospectus for a new way of thinking about the wavefunction of the universe: a $Ψ$-epistemic quantum cosmology. We present a proposal that, if successfully implemented, would resolve the cosmological measurement problem and simultaneously allow us to think sensibly about probability and evolution in quantum cosmology. Our analysis draws upon recent work on the problem of time in quantum gravity, upon causally-symmetric local hidden variable theories, and upon a dynamical origin for the cosmological arrow of time. Our conclusion weighs the strengths and weaknesses of the approach and points towards paths for future development.

gr-qc↗

arXiv2015

Quantum causal models, faithfulness and retrocausality

Wood and Spekkens (2015) argue that any causal model explaining the EPRB correlations and satisfying no-signalling must also violate the assumption that the model faithfully reproduces the statistical dependences and independences---a so-called "fine-tuning" of the causal parameters; this includes, in particular, retrocausal explanations of the EPRB correlations. I consider this analysis with a view to enumerating the possible responses an advocate of retrocausal explanations might propose. I focus on the response of Näger (2015), who argues that the central ideas of causal explanations can be saved if one accepts the possibility of a stable fine-tuning of the causal parameters. I argue that, in light of this view, a violation of faithfulness does not necessarily rule out retrocausal explanations of the EPRB correlations, although it certainly constrains such explanations. I conclude by considering some possible consequences of this type of response for retrocausal explanations.

quant-ph↗

arXiv2012

Causal Symmetry and the Transactional Interpretation

Cramer's (1986) transactional interpretation of quantum mechanics posits retrocausal influences in quantum processes in an attempt to alleviate some of the interpretational difficulties of the Copenhagen interpretation. In response to Cramer's theory, Maudlin (2002) has levelled a significant objection against any retrocausal model of quantum mechanics. I present here an examination of the transactional interpretation of quantum mechanics and an analysis of Maudlin's critique. I claim that, although Maudlin correctly isolates the weaknesses of Cramer's theory, his justification for this weakness is off the mark. The cardinal vice of the transactional interpretation is its failure to provide a sufficient causal structure to constrain uniquely the behaviour of quantum systems and I contend that this is due to a lack of causal symmetry in the theory. In contrast, Maudlin attributes this shortcoming to retrocausality itself and emphasises an apparently fundamental incongruence between retrocausality and his own metaphysical picture of reality. I conclude by arguing that the problematic aspect of this incongruence is Maudlin's assumptions about what is appropriate for such a metaphysical picture.

quant-ph↗

arXiv2012

Relativistic Constraints for a Naturalistic Metaphysics of Time

The traditional metaphysical debate between static and dynamic views in the philosophy of time is examined in light of considerations concerning the nature of time in physical theory. Adapting the formalism of Rovelli (1995, 2004), I set out a precise framework in which to characterise the formal structure of time that we find in physical theory. This framework is used to provide a new perspective on the relationship between the metaphysics of time and the special theory of relativity by emphasising the dual representations of time that we find in special relativity. I extend this analysis to the general theory of relativity with a view to prescribing the constraints that must be heeded for a metaphysical theory of time to remain within the bounds of a naturalistic metaphysics.

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