The objective of the consistent-amplitude approach to quantum theory has been to justify the mathematical formalism on the basis of three main assumptions: the first defines the subject matter, the second introduces amplitudes as the tools for quantitative reasoning, and the third is an interpretative rule that provides the link to the prediction of experimental outcomes. In this work we introduce a natural and compelling fourth assumption: if there is no reason to prefer one region of the configuration space over another then they should be ‘weighted ’ equally. This is the last ingredient necessary to introduce a unique inner product in the linear space of wave functions. Thus, a form of the principle of insufficient reason is implicit in the Hilbert inner product. Armed with the inner product we obtain two results. First, we elaborate on an earlier proof of the Born probability rule. The implicit appeal to insufficient reason shows that quantum probabilities are not more objective than classical probabilities. Previously we had argued that the consistent manipulation of amplitudes leads to a linear time evolution; our second result is that time evolution must also be unitary. The argument is straightforward and hinges on the conservation of entropy. The only subtlety consists of defining the correct entropy; it is the array entropy, not von Neumann’s. After unitary evolution has been established we proceed to introduce the useful notion of observables and we explore how von Neumann’s entropy can be linked to Shannon’s information theory. Finally, we discuss how various connections among the postulates of quantum theory are made explicit within this approach. 1
The objective of the consistent-amplitude approach to quantum theory has been to justify the mathematical formalism on the basis of three main assumptions: the first defines the subject matter, the second introduces amplitudes as the tools for quantitative reasoning, and the third is an interpretative rule that provides the link to the prediction of experimental outcomes. In this work we introduce a natural and compelling fourth assumption: if there is no reason to prefer one region of the configuration space over another then they should be ‘weighted ’ equally. This is the last ingredient necessary to introduce a unique inner product in the linear space of wave functions. Thus, a form of the principle of insufficient reason is implicit in the Hilbert inner product. Armed with the inner product we obtain two results. First, we elaborate on an earlier proof of the Born probability rule. The implicit appeal to insufficient reason shows that quantum probabilities are not more objective than classical probabilities. Previously we had argued that the consistent manipulation of amplitudes leads to a linear time evolution; our second result is that time evolution must also be unitary. The argument is straightforward and hinges on the conservation of entropy. The only subtlety consists of defining the correct entropy; it is the array entropy, not von Neumann’s. After unitary evolution has been established we proceed to introduce the useful notion of observables and we explore how von Neumann’s entropy can be linked to Shannon’s information theory. Finally, we discuss how various connections among the postulates of quantum theory are made explicit within this approach. 1
Quantum theory is formulated as the only consistent way to manipulate probability amplitudes. The crucial ingredient is a very natural consistency constraint: if there are two different ways to compute the amplitude for a given process, the two answers must agree. This constraint is expressed in the form of functional equations the solution of which leads to the usual sum and product rules for amplitudes. An immediate consequence is that the Schr\"odinger equation must be linear; i.e., nonlinear variants of quantum mechanics are inconsistent. The physical interpretation of the theory is given in terms of a single natural rule. This rule, which does not itself involve any probabilities, is used to obtain a proof of Born's statistical postulate: we show that the probability of a certain outcome in an experiment is given by the square of the modulus of the corresponding amplitude. Thus, consistency leads to indeterminism.
Quantum theory is the soul of contemporary physics. It was discovered in an adventurous way, under the urge to solve the puzzles posed by atomic spectra and blackbody radiation. But after its invention, it immediately became clear that it was not just a theory of specific physical systems: it was rather a new language of universal applicability. Already in 1928, the theory had received solid mathematical foundations by Hilbert, von Neumann, and Nordheim, and this work was brought to completion in the monumental work of von Neumann, in the form that we still study nowadays. The theory is extraordinarily successful, and its predictions have been confirmed to an astonishing level of precision in a large spectrum of experiments. However, almost 90 years after von Neumann's book, quantum theory remains mysterious. Its mathematical formulation – based on Hilbert spaces and self-adjoint operators – is far from having an intuitive interpretation. The association of physical systems to Hilbert spaces whose unit vectors represent pure states, the representation of transformations by unitary operators and of observables by self-adjoint operators – all such postulates look artificial and ad hoc . A slightly more operational approach is provided by the C * -algebraic formulation of quantum theory – still, this formulation relies on the assumption that observables form an algebra , where the physical meanings of the multiplication and the sum are far from clear. In short, the postulates of quantum theory impose mathematical structures without providing any simple reason for this choice: the mathematics of Hilbert spaces is adopted as a magic blackbox that “works well” at producing experimental predictions. However, in a satisfactory axiomatization of a physical theory the mathematical structures should emerge as a consequence of postulates that have a direct physical interpretation. By this we mean postulates referring, e.g., to primitive notions like physical system, measurement, or process, rather than notions like, e.g., Hilbert space, C * -algebra, unit vector, or selfadjoint operator. The crucial question thus remains unanswered: why quantum theory? Which are the principles at the basis of the theory? A case that is often invoked in contrast is that of Special Relativity theory, which directly follows from the simple understandable principle of relativity.
The notion of entropy originates historically in classical physics and is intertwined with thermodynamics. Shannon’s entropy: - Sum over i P(i) ln(P(i)), where P(i) is the probability for i, however, seems to apply to any probability, but in quantum mechanics appears to be particularly linked to spatial and momentum entropy (1) i.e. - Integral dx W*(x)W(x) ln[ W*(x)W(x)] and - Sum over p a*(p)a(p) ln[ a*(p)a(p) ] where W(x)= wavefunction = Sum over p a(p) exp(ipx). In this note we speculate that one may create an entropy from the real part of exp(ipx) i.e. cos(px) as this term is associated with probability within a wavelength even though the “center of mass” of the particle may be moving uniformly at v=x/t=constant and W*(x)W(x)=1 or a constant. The latter implies an entropy independent of p but there is uncertainty in a free particle due to its wavelength which is experimentally manifested. We argue there is no reason to limit entropy to x or p considerations. For a bound state, a pattern of crests and troughs of different lengths and heights may be produced and so again there is a pattern of unnormalized probability distributions with different weights. The absolute value may be taken so negative wavefunction values are not an issue. For both the free particle and the bound state two features emerge. First the shape of the distributions is linked to the curvature which in turn is associated with the kinetic energy. Thus the probability distributions which describe the quantum system are governed by kinetic energy. Secondly, a pattern of distributions, both negative and positive, ensures that exp(ipx) is perpendicular to other exp(ip1 x) functions and Wn(x) is perpendicular to other Wn1(x)’s. In other words energy identifies the statistical state which exists throughout space and one cannot confuse the identity of one state with another. Thus they are orthogonal throughout space and probability distributions (linked to entropy) seem to enforce this. The inner product of W*(x) and W(x) is like an inner product of a product probability of a state and its time reversed state. We suggest one should be able to define a Shannon’s entropy expression for both |cos(px)|/C1 from exp(ipx) over a half wavelength where C1 is a normalization factor and |W(x)|/C2 roughly over the length over which it has humps i.e. roughly the classical turning points for an oscillator for example. This entropy is not additive and does not map to classical entropy in the large n (energy level) limit. Furthermore it may not be linked to thermodynamics because it is not linked to x or p. Nevertheless, it might be used to describe uncertainty within the quantity system and equilibrium/stable scenarios which are observed in nature. For example, different Wn(x) states are statistically stable states, but one may knock out the particle and it will be in an exp(ipx) state which is also stable. Furthermore, a photon may excite Wn1(x) to Wn2(x), thus this new entropy seems to be linked to stable states allowed in nature. The “price to pay”, however, seems to be uncertainty in wavelength regions for a free particle and the crest/trough regions for a bound state. We also consider some properties of a similar entropy for bound states.
Why does a quantum measurement yield one definite outcome rather than another? Decoherence theory explains the disappearance of interference, yet it leaves the selection of a particular result unexplained—and says nothing about what role, if any, the observer plays. This paper confronts both gaps head-on. We construct an Extended Hilbert Space HTotal=HPhys⊗HHigher in which information-processing agents carry their own quantum degrees of freedom, coupled to the physical sector through an explicit interaction Hamiltonian. The resulting Intention Field Theory (IFT) draws on von Neumann’s two-process picture and Stapp’s arguments for mental causation, but goes further by deriving—rather than postulating—a Lindblad-form master equation from the coupling term. Four results follow: agent-dependent decoherence rates that scale with intentional coherence; observer-dependent corrections to Born-rule probabilities; preferred-basis selection fixed by the measurement interaction; and an entropic quantification theorem linking intentional coupling to entropy production, physical–higher mutual information, and a Landauer heat-dissipation bound per measurement event. We test these predictions against eleven landmark experiments—quantum Zeno, which-path, delayed-choice, Bell-inequality, and matter-wave platforms among them—and find per-event entropy increases spanning 10−14 to 10−1 bits, depending on coupling strength and interaction time. When the intentional coupling is switched off, every prediction collapses back to standard quantum mechanics, so the framework is conservative by construction. We compare IFT with nine major interpretations and several dynamical-collapse models, map out the theory’s current limitations, and design specific falsification protocols. The mathematical development is deductive: axioms first, then lemmas, propositions with full proofs, and finally testable corollaries whose numerical signatures differ from those of all existing frameworks.
This derivation block presents a conditional route to the Born probability rule within the EDC framework, based on two ingredients: the compactness of the extra-dimensional circle S^1_\xi and Gleason’s theorem on Hilbert-space probability measures. The note shows that L^2(S^1_\xi) is automatically a separable Hilbert space, with the standard Fourier basis e^{in\alpha}, and argues that, under the scanning hypothesis, the relevant observer-side amplitudes can be represented in that Hilbert space. Once this conditional step is accepted, Gleason’s theorem yields the Born rule P(n)=|c_n|^2 as the unique probability measure compatible with the Hilbert projection structure. The argument is therefore not a derivation from the full EDC action, but a conditional derivation whose single non-mathematical load-bearing link is the scanning hypothesis itself. A second contribution of the note is conceptual clarification. It explains why complex amplitudes arise naturally as the canonical Fourier language on the circle S^1_\xi, rather than as an independent postulate, and it carefully distinguishes between physical scanning readout with finite window functions and the exact Fourier-mode projection structure required by Gleason’s theorem. The document also sketches how the inner-product structure may be inherited into 4D sectors through Kaluza–Klein decomposition, while explicitly warning that the full physical reduction dictionary is not carried out here. In this way, the note is deliberately narrow in scope: it does not claim to derive the Schrödinger equation, entanglement, collapse, or the scanning hypothesis itself. The document is intended as a derivation note within the larger EDC observer-side quantum program. Its main result is epistemic rather than rhetorical: within the present dependency chain, the Born rule should be classified as [Dc] (derived conditionally) rather than as a conjecture. What remains open is equally explicit: deriving the scanning amplitude from SEDC, establishing the full time-evolution law, constructing a multi-particle tensor-product structure, explaining outcome selection, and making quaternionic exclusion rigorous.
The astute reader might have formed the impression that quantum in formation science is a rather qualitative discipline because we have not, as yet, explained how to quantify quantum information. There are three good reasons for leaving this important question until the final chapter. Firstly, quantum information theory is technically demanding and to treat it at an earlier stage might have suggested that our subject was more complicated than it is. Secondly, there is the fact that many of the ideas in the field, such as teleportation and quantum circuits, are unfamiliar and it was important to present these as simply as possible. Finally, and most importantly, the theory of quantum information is not yet fully developed. It has not yet reached, in particular, the level of completeness of its classical counterpart. For this reason we can answer only some of the many questions we would like a quantum theory of information to address. Having said this, we can say that however, there are beautiful and useful mathematical results and it seems certain that these will continue to form an important part of the theory as it develops. We noted in the introduction to Chapter 1 that ‘quantum mechanics is a probabilistic theory and so it was inevitable that a quantum information theory would be developed’. A presentation of at least the beginnings of a quantitative theory is the objective of this final chapter. The entropy or information derived from a given probability distribution is, as we have seen, a convenient measure of the uncertainty associated with the distribution. If many of the probabilities are large, so that many of the possible events are comparably likely, then the entropy will be large. If one probability is close to unity, however, then the entropy will be small. It is convenient to introduce entropy in quantum mechanics as a measure of the uncertainty, or lack of knowledge, of the form of the state vector. If we know that our system is in a particular pure state then the associated uncertainty or entropy should be zero. For mixed states, however, it will take a non-zero value.