An argument by one of us is first reproduced, demonstrating that the bare negation of the consequences imposed by the completeness hypothesis, concerning the particular formal fact that a quantum-mechanical free wave packet can spread out indefinitely, leads necessarily to predictions on the presence probability distribution in interference states that diverge from the corresponding quantum-mechanical predictions. It follows that, contrary to what seemed to be almost generally accepted, it is erroneous to admit systematically that the completeness problems are essentially unconnected to observation. This result is similar to one previously established by Bell and seems to support a suggestion by Ballentine, that any hidden-variable theory might necessarily lead to predictive divergences from quantum mechanics, if internal "pathologies" are not admitted. The above-mentioned argument entails a first minimal definition of a nonorthodox significance of a state vector. In the continuation of this work this definition is tentatively developed in a constructive way. This development is realized by a modification of de Broglie's model of a microsystem. This modification, imposed by an examination of de Broglie's double-solution theory in the light of our conclusion demonstrated before, is in fact rather profound; in particular, it forces the abandonment of the central idea of two solutions with distinct physical meanings, of a unique evolution law. However, the theory called into consideration by this modification may be capable of leading to objective proofs of the specific descriptive power of the essence of de Broglie's conception on the structure of microsystems. Indeed, inside the general nonorthodox framework tentatively outlined, a detailed definition of the presence probability distribution is elaborated that coincides with the quantum-mechanical one outside interference states, but diverges from it in interference states, in an experimentally testable way. This is a verifiable constructive embodiment of the conclusion only critically obtained at the beginning of this work. A final verdict on the value of the specific basic conception of the outlined theory and of the new perspectives it brings forth can be obtained only by a further systematic theoretical elaboration and by the corresponding experimental tests.
An argument by one of us is first reproduced, demonstrating that the bare negation of the consequences imposed by the completeness hypothesis, concerning the particular formal fact that a quantum-mechanical free wave packet can spread out indefinitely, leads necessarily to predictions on the presence probability distribution in interference states that diverge from the corresponding quantum-mechanical predictions. It follows that, contrary to what seemed to be almost generally accepted, it is erroneous to admit systematically that the completeness problems are essentially unconnected to observation. This result is similar to one previously established by Bell and seems to support a suggestion by Ballentine, that any hidden-variable theory might necessarily lead to predictive divergences from quantum mechanics, if internal "pathologies" are not admitted. The above-mentioned argument entails a first minimal definition of a nonorthodox significance of a state vector. In the continuation of this work this definition is tentatively developed in a constructive way. This development is realized by a modification of de Broglie's model of a microsystem. This modification, imposed by an examination of de Broglie's double-solution theory in the light of our conclusion demonstrated before, is in fact rather profound; in particular, it forces the abandonment of the central idea of two solutions with distinct physical meanings, of a unique evolution law. However, the theory called into consideration by this modification may be capable of leading to objective proofs of the specific descriptive power of the essence of de Broglie's conception on the structure of microsystems. Indeed, inside the general nonorthodox framework tentatively outlined, a detailed definition of the presence probability distribution is elaborated that coincides with the quantum-mechanical one outside interference states, but diverges from it in interference states, in an experimentally testable way. This is a verifiable constructive embodiment of the conclusion only critically obtained at the beginning of this work. A final verdict on the value of the specific basic conception of the outlined theory and of the new perspectives it brings forth can be obtained only by a further systematic theoretical elaboration and by the corresponding experimental tests.
The dominance of the Copenhagen interpretation is the result of a historical accident (Cushing, 1994). At the Solvay conference in 1927, Louis de Broglie put forward the deterministic pilot wave theory, described later. Never slow to criticize, Pauli jumped up and demolished de Broglie’s proposal, and de Broglie was so discouraged by this that he did not develop his interpretation any further. The Copenhagen interpretation was then developed by Bohr, Heisenberg, Pauli and many others, as described in the previous chapter. It was strongly supported by von Neumann’s proof of the impossibility of hidden variables. Years later, in 1952, Bohm published a deterministic hidden variable theory, showing that there must be something wrong with von Neumann’s proof. The error was found by John Bell in 1966, as described in the last chapter, and he also showed how Pauli’s objections to de Broglie’s original idea can be answered. If this had been done at the conference in 1927, quantum mechanics could have been interpreted deterministically from the beginning. The essential mistake in the Copenhagen interpretation is to treat it as a complete account of the behaviour of each individual system. It is frequently claimed that it enables us to calculate, at least in principle, everything that can be measured. Thus Hooft (1997, p. 11) said that ‘The laws of quantum mechanics have been formulated very accurately. We know exactly how to compute anything we would like to know.’ Also Peierls (1997, p. 25) has said that quantum mechanics ‘had become a complete and consistent scheme capable of giving a unique answer to any questions relating to actual or possible observations’. Even if this were true, it would not imply that it is the final complete theory, for it is always possible that some new phenomenon might be found that cannot be calculated quantum-mechanically. However, it is not true: there are many phenomena such as the time of decay of a radioactive nucleus, or the direction a particle is scattered by a nucleus, that cannot be calculated, even in principle. Quantum mechanics is therefore an incomplete theory. We can only calculate the statistical properties of these systems, such as the half-life of a radioactive decay or the differential scattering cross-section that gives the probabilities that a particle is scattered through various angles. All measurements of quantum systems are of this statistical character. It might be thought that the possibility of making measurements on a single electron provides an exception to this. However, even in such cases the electron is continually bathed in a fluctuating background radiation from nearby atoms. Since this is variable, that electron is a member of an ensemble of electrons subject to different fluctuations. All these examples clearly demonstrate the statistical character of quantum mechanics. ‘I am rather firmly convinced’, Einstein (in Schilpp, 1949, pp. 666, 671) remarked, ‘that the essentially statistical character of contemporary quantum theory is solely to be ascribed to fact that this theory operates with an incomplete description of physical systems’. As a result, ‘the c-function is to be understood as the description not of a single system but of an ensemble of systems’. So, ‘if the statistical quantum theory does not pretend to describe the individual system completely, it appears unavoidable to look elsewhere for a complete description of the individual systems’. Thus ‘the difficulties of theoretical interpretation disappear, if one views the quantum-mechanical description as a description of an ensemble of systems’. If this is achieved, ‘the statistical theory would, within the framework of future physics, take an approximately analogous position to statistical mechanics within the framework of classical mechanics’. ‘Thus, essentially, nothing has changed since Galileo or Newton or Faraday concerning the status of the ‘‘observer’’ or our ‘‘consciousness’’ or of our ‘‘information’’ in physics’ (Popper, 1982, p. 46). Once this is accepted, the quantum paradoxes that plagued the Copenhagen interpretation are easily resolved, as described below. In any textbook of quantum mechanics problems such as the calculation of the energy levels of the hydrogen atom are solved as if that hydrogen atom is alone in the universe. As Feynman (1972) remarked, ‘when we solve a quantum-mechanical problem, what we really do is to divide the universe into two parts – the system in which we are interested and the rest of the universe. We then usually act as if the system in which we are interested comprised the whole universe.’ In fact, however, every hydrogen atom on which measurements are made is surrounded by other atoms and exposed to their radiations. Quantum mechanics somehow takes this into account and gives the average behaviour of an ensemble of hydrogen atoms. A more detailed theory takes these influences into account. One attempt to do this is stochastic electrodynamics, described in a later section.
The Question of the Completeness of Quantum Mechanics When a classical system is in a pure state, that is, when its preparation represents maximal information, the value of every physical quantity is uniquely predicted. In other words, classical pure states are dispersion-free, and classical mechanics is deterministic. Only in case the state is nonpure, thus representing nonmaximal information about the system, does probability enter into the theory. Things are different with quantum systems. Even in case the state of the system is pure, it is impossible to predict a definite value of every physical quantity: only the probability distributions of the physical quantities are given. Pure quantum states have dispersion (though, of course, they can be dispersion-free for particular physical quantities), and probability enters into quantum theory at a much more fundamental level. The basic idea of so-called hidden-variable theories is to reject the fundamental role of probability in quantum theory and to argue that probability arises because quantum states, even the pure ones, do not represent the ultimate information about the system. Accordingly, it is conjectured that there are certain hidden variables, not yet subject to experimental detection, which would complete the information carried by the quantum states, thus giving rise to so precise a knowledge of the system that probabilities would disappear and precise values of all physical quantities would be uniquely determined.
Paper 74 — No Quantum Superposition This paper argues, by reductio ad absurdum, that the physical realisation of superposition — simultaneous multi-location existence — is incompatible with seven independent and well-established physical principles: (1) the observational fact that no infinite physical quantity has ever been measured; (2) conservation of energy; (3) the mass-energy equivalence E = mc²; (4) the Bekenstein entropy bound; (5) the second law of thermodynamics; (6) the Heisenberg uncertainty principle; and (7) causality. The foundational identification is that information, energy, and mass stand in proportional existential relation (Bekenstein bound: I ∝ M; Landauer principle: ΔE ∝ ΔI; mass-energy equivalence: E = mc²). Complete superposition requires infinite information processing, and therefore infinite energy and infinite mass — quantities universally absent from the observational record of physics. Finite N-state superposition is excluded by a complementary argument: maintaining N states simultaneously requires N times the information-processing load of a single undetermined state, violating the principle that nature selects minimum-load configurations. The positive alternative proposed is the undetermined state: during matter-wave propagation, the matter wave is real and physically present, but matter has not yet appeared at any location. This is not a hidden-variable state but an ontological absence of localisation prior to the formation of a constructive interference maximum. Paper 75 — The Double-Slit Experiment Reinterpreted This paper applies the undetermined-state ontology to the paradigmatic demonstration of quantum mechanics. The de Broglie matter wave — a real physical wave — passes through both slits, while the particle remains in an undetermined state until a constructive interference maximum is formed at the detection screen. The disappearance of the interference pattern upon which-path measurement is explained without wavefunction collapse: the measurement interaction physically disrupts the matter wave's coherent two-slit propagation. Three experimentally testable predictions distinguish this framework: (1) weak-measurement trajectory reconstruction should reveal single-path trajectories inconsistent with simultaneous two-slit passage; (2) diffraction fringe spacing should depend on the mass density of the slit material, because denser slit edges generate a steeper refractive-index gradient; (3) the fringe pattern should exhibit a density-dependent phase shift measurable with current matter-wave interferometry technology. The Schrödinger equation and Born's rule are retained without modification. Paper 76 — Discriminating Experiments for the Constructive-Interference Account of Gravity This paper derives the specific numerical values predicted by Paper 29 — n(r) from the Schwarzschild metric, Δφ = k₀∫[n₁(r)−n₂(r)]dr from the medium-structure integral, and Δx_max = f(∇n, geometry, λ₀) from the interference structure — and assesses whether current experimental technology can measure the gap between Paper 29's predictions and standard QM's predictions. Three formal conditions for a discriminating experiment are established: structural absence of the variable from standard QM, signal exceeding current resolution, and impossibility of alternative explanation. Two experimental classes satisfy all three conditions with existing apparatus: COW path-geometry (predicted δ(Δφ) ~ 10⁻³ rad vs. resolution ~10⁻⁴ rad, path shape structurally absent from the standard COW formula) and slit-material density (predicted Δx_max ~ tens of nm vs. resolution 1–5 nm, material density structurally absent from Δy ≈ λL/a). Cumulative agreement across both systems constitutes genuine inductive support for the proposed mechanism. Paper 77 — From Electrons to Fullerenes This paper addresses three questions that Paper 76 does not: (1) why the slit-material density experiment has never been performed in the hundred years since matter-wave interferometry began — the answer being that standard QM contains no density variable in the slit formula, so experimenters had no reason to vary it, with the Copenhagen prohibition on mechanism questions as the deeper structural reason; (2) why confirmation in exactly two systems — electrons and fullerenes C₆₀ — is sufficient to establish the theoretical outline across six orders of magnitude in mass, because these systems are maximally independent in particle type, mass, apparatus, energy scale, and decoherence environment; (3) what confirmation across this mass range would establish for physics: the first experimentally supported identification of the physical mechanism of gravity, the first experimentally verifiable quantum-gravity connection at accessible energy scales, a physical grounding of Born's rule, and a mechanistic account of the measurement problem. A complete three-layer control protocol for excluding the slit-width confound is specified. Paper 78 — A Three-Dimensional Experimental Matrix This paper extends the experimental programme by introducing slit thickness as a third independent variable alongside matter-wave species and slit-material density. The wave-mechanical account predicts that phase shift scales linearly with slit thickness d: Δφ(ρ,d) = (2π/λ)·[n(ρ)−1]·d — a prediction structurally absent from standard QM, which assigns no physical role to slit thickness. The resulting 5×5×3 matrix of 75 independent measurements has a random coincidence probability of approximately 1/1,728,000, rendering chance agreement with theoretical prediction physically impossible. Three-layer control protocols for fabrication, TEM cross-section verification, and linearity testing are specified for the thickness dimension. Together, the five papers constitute a complete programme: ontological foundation (P74), phenomenological reinterpretation (P75), formal discriminating analysis (P76), strategic and historical argument (P77), and three-dimensional experimental design (P78).
Quantum mechanics has been enormously successful in explaining the behavior of microsystems such as molecules, atoms, and nuclei. We have seen that quantum mechanics describes a quantum system by the wave function ψ, which is the solution of the Schro¨dinger equation. The wave function determines the probability amplitudes (whose modulus squared gives the probability) for all possible outcomes of a measurement corresponding to an observable on the system. In general, the wave function does not uniquely predict the result of a measurement; it only provides a probability distribution for all possible results of the measurement on a quantum system. Only if the system happens to be in an eigenstate corresponding to the observable being measured, is the result of a measurement of this observable completely predictable. On the other hand, the results of measurements corresponding to a conjugate or non-commuting observable, on the same system in the same state, are indeterminate. Quantum mechanical description of physical systems raises profound questions: How are the wave function and the probabilities for different outcomes of a measurement to be interpreted? Does the wave function represent a single system or an ensemble of systems? Does the physical system actually have the attribute corresponding to the measurement in question or does the measurement itself create the attribute? These questions led to different interpretations of quantum mechanics, which were vigorously debated during the years of its discovery as also in the following decades. The new idea of indeterminacy was especially difficult to reconcile with the long-held view that a physical theory should aim at predicting accurately, and without ambiguity, the result of any measurement on any system, big or small. These debates not only gave us a deeper understanding of quantum mechanics but also changed profoundly the way we view the micro-world.
Chapter 1: On the existence of quantum representations for two dichotomic measurements. Under which conditions do outcome probabilities of measurements possess a quantum-mechanical model? This kind of problem is solved here for the case of two dichotomic von Neumann measurements which can be applied repeatedly to a quantum system with trivial dynamics. The solution uses methods from the theory of operator algebras and the theory of moment problems. The ensuing conditions reveal surprisingly simple relations between certain quantum-mechanical probabilities. It also shown that generally, none of these relations holds in general probabilistic models. This result might facilitate further experimental discrimination between quantum mechanics and other general probabilistic theories. Chapter 2: Possibilistic Physics. I try to outline a framework for fundamental physics where the concept of probability gets replaced by the concept of possibility. Whereas a probabilistic theory assigns a state-dependent probability value to each outcome of each measurement, a possibilistic theory merely assigns one of the state-dependent labels "possible to occur" or "impossible to occur" to each outcome of each measurement. It is argued that Spekkens' combinatorial toy theory of quantum mechanics is inconsistent in a probabilistic framework, but can be regarded as possibilistic. Then, I introduce the concept of possibilistic local hidden variable models and derive a class of possibilistic Bell inequalities which are violated for the possibilistic Popescu-Rohrlich boxes. The chapter ends with a philosophical discussion on possibilistic vs. probabilistic. It can be argued that, due to better falsifiability properties, a possibilistic theory has higher predictive power than a probabilistic one. Chapter 3: The quantum region for von Neumann measurements with postselection. It is determined under which conditions a probability distribution on a finite set can occur as the outcome distribution of a quantum-mechanical von Neumann measurement with hyphenation given that the scalar product between the initial and the final state is known as well as the success probability of the postselection. An intermediate von Neumann measurement can enhance transition probabilities between states such that the error probability shrinks by a factor of up to 2. Chapter 4: A presentation of the category of stochastic matrices. This chapter gives generators and relations for the strict monoidal category of probabilistic maps on finite cardinals (i.e., stochastic matrices). Chapter 5: Convex Spaces: Definition and Examples. We try to promote convex spaces as an abstract concept of convexity which was introduced by Stone as "barycentric calculus''. A convex space is a set where one can take convex combinations in a consistent way. By identifying the corresponding Lawvere theory as the category from chapter 4 and using the results obtained there, we give a different proof of a result of Swirszcz which shows that convex spaces can be identified with algebras of a finitary version of the Giry monad. After giving an extensive list of examples of convex sets as they appear throughout mathematics and theoretical physics, we note that there also exist convex spaces that cannot be embedded into a vector space: semilattices are a class of examples of purely combinatorial type. In an information-theoretic interpretation, convex subsets of vector spaces are probabilistic, while semilattices are possibilistic. Convex spaces unify these two concepts.
Some recent experiments claim to show that any model in which a quantum state represents mere information about an underlying physical reality of the system must make predictions which contradict those of quantum theory. The present work undertakes to investigate the issue of reality, treading a more fundamental route from the Hamilton-Jacobi equation of classical mechanics to the Schrodinger equation of quantum mechanics. Motivation for this is a similar approach from the eikonal equation in geometrical optics to the wave equation in electromagnetic theory. We rewrite the classical Hamilton-Jacobi equation as a wave equation and seek to generalise de Broglie's wave particle duality by demanding that both particle and light waves have the freedom of being described by any square-integrable function. This generalisation, which allows superposition also for matter wave functions, helps us to obtain the Schrodinger equation, whose solution can be seen to be as much objective as the classical mechanics wave function. Several other equations which one writes in quantum mechanics, including the eigenvalue equations for observables, series expansion of energy states in terms of eigenstates of observables other than energy, etc., can be written in the classical case too. Absence of any collapse of the wave function, entanglement, etc. in the classical realm have their origin in the nonlinearity of the classical wave equation. These considerations indicate that many of the puzzles in quantum mechanics are present also in classical mechanics in a dormant form, which fact shall help to demystify quantum mechanics to a great extent.