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arXiv:1712.09725 · Annalen der Physik

The Symmetrical Foundation of Measure, Probability, and Quantum Theories

John Skilling, Kevin H. Knuth

Published Jun 13, 2018• 12 citations
arXivHTMLPDF

Abstract

Abstract Quantification starts with sum and product rules that express combination and partition. These rules rest on elementary symmetries that have wide applicability, which explains why arithmetical adding up and splitting into proportions are ubiquitous. Specifically, measure theory formalizes addition, and probability theory formalizes inference in terms of proportions. Quantum theory rests on the same simple symmetries, but is formalized in two dimensions, not just one, in order to track an object through its binary interactions with other objects. The symmetries still require sum and product rules (here known as the Feynman rules), but they apply to complex numbers instead of real scalars, with observable probabilities being modulus squared (known as the Born rule). The standard quantum formalism follows. There is no mystery or weirdness, just ordinary probabilistic inference.

DOI
10.1002/andp.201800057

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Abstract Quantification starts with sum and product rules that express combination and partition. These rules rest on elementary symmetries that have wide applicability, which explains why arithmetical adding up and splitting into proportions are ubiquitous. Specifically, measure theory formalizes addition, and probability theory formalizes inference in terms of proportions. Quantum theory rests on the same simple symmetries, but is formalized in two dimensions, not just one, in order to track an object through its binary interactions with other objects. The symmetries still require sum and product rules (here known as the Feynman rules), but they apply to complex numbers instead of real scalars, with observable probabilities being modulus squared (known as the Born rule). The standard quantum formalism follows. There is no mystery or weirdness, just ordinary probabilistic inference.
Abstract. Physics is real. Measurement produces real numbers. Yet quantum mechanics uses com-plex arithmetic, in which √−1 is necessary but mysteriously relates to nothing else. By applying the same sort of symmetry arguments that Cox [1, 2] used to justify probability calculus, we are now able to explain this puzzle. The dual device/object nature of observation requires us to describe the world in terms of pairs of real numbers about which we never have full knowledge. These pairs combine according to complex arithmetic, using Feynman’s rules.
We can use quantum theory to explain an enormous variety of phenomena by showing why they were to be expected and what they depend on. These explanations of probabilistic phenomena involve applications of the Born rule: to accept quantum theory is to let relevant Born probabilities guide one’s credences about presently inaccessible events. We use quantum theory to explain a probabilistic phenomenon by showing how its probabilities follow from a correct application of the Born rule, thereby exhibiting the phenomenon’s dependence on the quantum state to be assigned in circumstances of that type. This is not a causal explanation since a probabilistic phenomenon is not constituted by events that may manifest it: but each of those events does depend causally on events that actually occur in those circumstances. Born probabilities are objective and sui generis, but not all Born probabilities are chances.
First steps are taken toward a formulation of quantum mechanics which avoids the use of probability amplitudes and is expressed entirely in terms of observable probabilities. Quantum states are represented not by state vectors or density matrices but by “probability tables,” which contain only the probabilities of the outcomes of certain special measurements. The rule for computing transition probabilities, normally given by the squared modulus of the inner product of two state vectors, is re-expressed in terms of probability tables. The new version of the rule is surprisingly simple, especially when one considers that the notion of complex phases, so crucial in the evaluation of inner products, is entirely absent from the representation of states used here.
Complex numbers are an intrinsic part of the mathematical formalism of quantum theory and are perhaps its most characteristic feature. In this article, we show that the complex nature of the quantum formalism can be derived directly from the assumption that a pair of real numbers is associated with each sequence of measurement outcomes, with the probability of this sequence being a real-valued function of this number pair. By making use of elementary symmetry conditions, and without assuming that these real number pairs have any other algebraic structure, we show that these pairs must be manipulated according to the rules of complex arithmetic. We demonstrate that these complex numbers combine according to Feynman's sum and product rules, with the modulus-squared yielding the probability of a sequence of outcomes.
This book is devoted to aspects of the foundations of quantum mechanics in which probabilistic and statistical concepts play an essential role. The main part of the book concerns the quantitative statistical theory of quantum measurement, based on the notion of positive operator-valued measures. During the past years there has been substantial progress in this direction, stimulated to a great extent by new applications such as Quantum Optics, Quantum Communication and high-precision experiments. The questions of statistical interpretation, quantum symmetries, theory of canonical commutation re
This paper addresses the foundational question deferred by Paper VII: why does the multiplicity Omega of U-field microstates combine as the squared modulus of a complex amplitude? We argue that if the coarse-grained U-field microstate sum admits a path-integral representation over field configurations with phase weights exp(iS/hbar_eff), then a Complex Multiplicity Amplitude Z(Y) is associated with each outcome Y. Via a Constraint Surface Geometry argument, we show that the effective multiplicity must take the form Omega(Y) = |Z(Y)|^n by phase invariance and multiplicativity, and the empirically observed bilinear interference structure selects n=2, yielding Omega(Y) = |Z(Y)|^2. The Born rule P proportional to |psi|^2 then follows from the multiplicity principle P proportional to Omega together with the identification psi proportional to Z. Interference arises from linear addition of complex amplitudes before squaring; classical probability addition is recovered via decoherence. The outcome-selection rule (the Probabilistic Bias Functional B) is grounded in the ergodic/mixing dynamics of the Tier-1 lattice, conditional on mixing within the accessible phase-space sector. The construction of the path-integral measure from U-field microstate counting remains an open problem. This is the eighth paper in the 18-paper USSFT technical series; for the U-field Lagrangian foundations see Papers I-VI, for the quantum mechanics operator formalism see Paper VII (DOI: 10.5281/zenodo.19675374), and for spin structure and Bell correlations see Paper IX.