The role played by irreversible processes, at the microscopic scale, in several examples of quantum measurements is studied within a "minimally realist" interpretation of the quantum formalism introduced in a recent publication. The analysis extends and confirms the basic results of the earlier work: separation of the collapse and amplification phases of the measurement, and decoherence and collapse happening already as a consequence of irreversible microscopic processes at the level of the "probe" itself (typically an atom in the examples considered). Additionally, the proposed interpretation of the formalism is shown to be consistent with previous interpretations, and a case for true irreversibility in physics is argued in some detail.
The role played by irreversible processes, at the microscopic scale, in several examples of quantum measurements is studied within a "minimally realist" interpretation of the quantum formalism introduced in a recent publication. The analysis extends and confirms the basic results of the earlier work: separation of the collapse and amplification phases of the measurement, and decoherence and collapse happening already as a consequence of irreversible microscopic processes at the level of the "probe" itself (typically an atom in the examples considered). Additionally, the proposed interpretation of the formalism is shown to be consistent with previous interpretations, and a case for true irreversibility in physics is argued in some detail.
## Abstract Textbook quantum mechanics defines measurement using ideas that are not themselves basic physics: "observer," "macroscopic apparatus," "irreversible record." We take this definition apart and find that it bundles two different things: the physical event of an interaction, and the statistical fact that the event's result becomes hard to erase. We separate them. A measurement, in its minimal form, is a causal link: when event A and event B interact, a fact is established between them — B's state relative to A. This happens at every interaction, at every scale, with no apparatus required. What laboratories call "a measurement" is the same kind of event, after its result has spread — fanned out — into so many further causal links that undoing it is no longer practical. This reading gives the quantum eraser a clean explanation: an outcome is erasable exactly as long as its causal fan-out stays narrow. It also clarifies what decoherence theory does and does not do: decoherence is the physics of fan-out, and it does that job well; the question it was criticized for not answering (why one outcome, with Born-rule probability) belongs to a different layer. Nothing in the existing formalism changes. What changes is the definition — and with it, the need for a separate "collapse mechanism" disappears. Because the basic unit here is a causal link, the whole picture can be built directly on discrete causal structures, which we identify as the natural next step. Keywords: measurement problem, decoherence, causal link, quantum eraser, relational quantum mechanics
Abstract This article presents a revised and conceptually refined formulation of a previously proposed Temporal Interpretation of quantum measurement, explicitly addressing the physical nature of wavefunction collapse. While the original proposal emphasised relativistic aspects of momentum superpositions, the present work clarifies the interpretation within the standard formalism of quantum mechanics, without introducing new dynamics or experimental predictions. Unitary evolution is read as a process of differentiated phase accumulation between branches of a quantum state. In relativistic contexts, phase differentials can be structurally related to effective proper-time differentials, allowing the introduction of a notion of temporal compatibility that provides a physically grounded account of decoherence. When such differentials exceed a characteristic scale, interference between branches becomes operationally inaccessible, while global unitarity is preserved. The observer is treated as a physical system endowed with an irreversible proper time associated with macroscopic, entropic dynamics. Within this framework, collapse is explained as an emergent physical phenomenon arising from the irreversibility of the observer’s proper time, which prevents the reconstruction of phase coherence after an interaction. Collapse is therefore neither a fundamental dynamical mechanism nor an objective event in space-time, but a necessary consequence of temporal irreversibility in physical observers. This formulation sharpens the distinction between decoherence and collapse, preserves full consistency with the Born rule, and positions the Temporal Interpretation as a competing interpretative framework that provides a concrete physical explanation for the quantum–classical transition, improving and clarifying the original proposal. This version clarifies the operational status of the interaction time, refines Sections 5.3 and 5.4, and standardises references and editorial structure. No changes to the formalism or conclusions.
Irreversibility, strengthened by the idea of strong mixing, has been discussed in the last two chapters. We reached the conclusion that, once such processes have been involved in a quantum measurement, it is in principle impossible to perform an interference experiment that would demonstrate the continued existence of a superposition. It is then ‘safe’ to assume that the system has ‘really’ collapsed into a state corresponding to one of the possible measurement outcomes. Does this mean that the measurement problem has been solved? Clearly it has for all practical purposes, as has been pointed out several times in earlier chapters. But it may still not be sufficient to provide a completely satisfactory solution in principle: in particular, we note that we have still not properly addressed the question of actualisation outlined at the end of the first section of Chapter 8. In the present chapter we discuss an interpretation of quantum physics that was developed during the last 15 or so years of the twentieth century and is based on the idea of describing quantum processes in terms of ‘consistent histories’. As we shall see, the resulting theory has much in common with the Copenhagen interpretation discussed in Chapter 4 and when applied to measurement it connects with the viewpoint, discussed in the last chapter, in which irreversible processes are to be taken as the primary reality.
This work proposes a threshold-based picture of decoherence in quantum measurement. Microscopic quantum dynamics remain fully continuous and unitary, but real detectors implement thresholded amplification and nonlinear gain boundaries that partition continuous microscopic inputs into discrete macroscopic outcomes. Within this framework, discreteness and irreversibility arise from scale asymmetry between a continuous microscopic energy distribution and a finite macroscopic threshold ΔE_threshold, without invoking fundamental collapse, branching, or uncontrolled environmental decoherence. The measurement apparatus effectively performs an analog-to-digital conversion: it maps a continuous input distribution ρ(E) to a binary output variable X_eff ∈ {0,1} according toP(event) = ∫_{ΔE_threshold}^{∞} ρ(E) dE,while the recording layer irreversibly erases phase information by structural codomain restriction. This threshold-based decoherence model preserves standard quantum mechanics, provides an operational bridge across major interpretations of quantum theory, and locates the origin of discrete outcomes in the architecture of measurement rather than in quantum ontology itself. In short, this paper views discrete measurement outcomes as emerging from threshold detector architecture rather than from any fundamental discreteness of the quantum substrate.
Irreversibility, strengthened by the idea of strong mixing, has been discussed in the last two chapters. We reached the conclusion that, once such processes have been involved in a quantum measurement, it is in practice impossible to perform an interference experiment that would demonstrate the continued existence of a superposition. It is then ‘safe’ to assume that the system has ‘really’ collapsed into a state corresponding to one of the possible measurement outcomes. Does this mean that the measurement problem has been solved? Clearly it has for all practical purposes, as has been pointed out several times in earlier chapters. But it may still not be sufficient to provide a completely satisfactory solution in principle: in particular, we note that we have still not properly addressed the question of actualisation outlined at the end of the first section of Chapter 8. In the present chapter we discuss an interpretation of quantum physics that was developed during the last 15 or so years of the twentieth century and is based on the idea of describing quantum processes in terms of ‘consistent histories’. As we shall see, the resulting theory has much in common with the Copenhagen interpretation discussed in Chapter 4 and when applied to measurement it connects with the viewpoint, discussed in the last chapter, in which irreversible processes are to be taken as the primary reality. We begin with a short discussion of the meaning and purpose of a scientific theory.
Some observations are presented starting with the well-known article by Vladimir Fock “Quantum Physics and Philosophical Problems”, published in 1971. In this article, which summarizes for Western readers a long and complicated reflection of the foundations of quantum mechanics (QM), Fock illustrates his “minimal” interpretation of this theory. By minimal, we mean that it only uses concepts related to the operational aspects of the measurement procedures, avoiding any mention of definite quantum ontologies (Bell’s beables). It is argued that, by taking into account the time reversal invariance of the microscopic processes and introducing the notion of irreversibility in an appropriate manner, Fock’s description becomes an anticipation of the “transaction” notion introduced by Cramer a decade later. So, the concept of “collapse” does retain the features of a QM “freak” postulate to become a new way to look at the elementary quantum processes.