Wavefunction collapse is usually seen as a discontinuous violation of the unitary evolution of a quantum system, caused by the observation. Moreover, the collapse appears to be nonlocal in a sense which seems at odds with general relativity. In this article the possibility that the wavefunction evolves continuously and hopefully unitarily during the measurement process is analyzed. It is argued that such a solution has to be formulated using a time symmetric replacement of the initial value problem in quantum mechanics. Major difficulties in apparent conflict with unitary evolution are identified, but eventually its possibility is not completely ruled out. This interpretation is in a weakened sense both local and realistic, without contradicting Bell's theorem. Moreover, if it is true, it makes general relativity consistent with quantum mechanics in the semiclassical framework. Quanta 2016; 5: 19–33.
Wavefunction collapse is usually seen as a discontinuous violation of the unitary evolution of a quantum system, caused by the observation. Moreover, the collapse appears to be nonlocal in a sense which seems at odds with general relativity. In this article the possibility that the wavefunction evolves continuously and hopefully unitarily during the measurement process is analyzed. It is argued that such a solution has to be formulated using a time symmetric replacement of the initial value problem in quantum mechanics. Major difficulties in apparent conflict with unitary evolution are identified, but eventually its possibility is not completely ruled out. This interpretation is in a weakened sense both local and realistic, without contradicting Bell's theorem. Moreover, if it is true, it makes general relativity consistent with quantum mechanics in the semiclassical framework. Quanta 2016; 5: 19–33.
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.
Wave function collapse has long been regarded as a fundamental element of the quantum measurement process, providing a mechanism by which a superposed quantum state yields a single observed outcome. Despite its widespread use, the physical meaning of collapse remains conceptually controversial. In particular, it is often assumed that the quantities associated with a quantum state before measurement and the values obtained after measurement belong to the same conceptual category. This assumption leads naturally to the image of a discontinuous transition in which one value is selected from a superposition of possibilities. In the present work, we reexamine the concept of quantum collapse from the perspective of observability. We argue that pre-measurement quantities do not constitute observable values in the ordinary operational sense. Rather, they represent a structure of potential observability associated with possible measurement outcomes. By contrast, post-measurement outcomes correspond to operationally realized observability, in which a specific result becomes accessible through measurement. From this viewpoint, the apparent collapse does not represent a physical jump of an already existing value, but a transition from potential observability to operationally realized observability. Based on this distinction, we propose that many conceptual difficulties traditionally associated with wave function collapse arise from treating these two fundamentally different forms of observability as if they were physically equivalent. The apparent discontinuity of collapse may therefore originate not from a discontinuous change in reality itself, but from a conceptual conflation of potential observability and operationally realized observability. Within the Intrinsic Observability Framework (IOF), this interpretation naturally leads to the concept of accessibility transition, in which the emergence of a definite outcome is understood as a change in accessible structure rather than as a fundamental non-unitary state reduction. The present analysis suggests that wave function collapse may not be a fundamental physical phenomenon, but instead a consequence of the transition from potential observability to operationally realized observability. This perspective provides a conceptual reorganization of the measurement problem and clarifies the role of observability in the emergence of definite quantum outcomes.
The Quantum Mechanics is interpreted, in this article, in a simple and direct way. By combining the unitary evolution with the quantum condition that observations require the state vector to be an eigenstate of the observable, a discontinuity in evolution (the state vector reduction) seems to be mandatory. Thus, for each such discontinuity, new initial conditions for the time evolution state vector are needed, and they are obtained by measurements. Delayed-choice experiments suggest that these new initial conditions are specified after the discontinuity takes place. Consequently, because it needs initial conditions that can be specified with a delay, the time evolving state vector is semi-realistic (in the sense that it is not completely specified until the measurement is performed), and not entirely realistic. The collapse of the wave function, especially when it is combined with the entanglement, seems to be a non-local phenomenon. In fact, the non-locality is present only as a consistency requirement for the initial conditions needed to select a solution of the evolution equation. The Direct Interpretation is intended to provide to our intuition a physical background, for helping us thinking about quantum phenomena. It identifies the main counterintuitive parts of the Quantum Mechanics in the discontinuity and the delayed initial conditions. Because it makes minimal assumptions, it is compatible with the main interpretations of Quantum Mechanics. Two principal unclear points of Quantum Mechanics are identified in the discontinuities, and the measurement problem. Both problems will be approached in subsequent articles.
A new approach to wavefunction collapse is proposed. The so-called Dynamical Spacetime approach enhances semiclassical gravity and enables it for an explanation of wavefunction collapse by postulating that the spacetime region on which quantum fields exist and on which the wavefunction's evolution can be regarded is bounded towards the future by a spacelike hypersurface, which is dynamically expanding towards the future. Collapse is displayed in the way that the wavefunction's evolution becomes unstable at certain critical expansions of spacetime, at which it reconfigures via a self-reinforcing mechanism quasi-abruptly to an evolution resembling a classical trajectory. Thereby, spacetime geometry changes in favour of the winning state, which causes the path of the other state to vanish by destructive interference. This mechanism for collapse can explain the quantum correlations in EPR experiments without coming into conflict with relativity and the Free Will theorem. The Dynamical Spacetime approach is mathematically formulated on basis of the Einstein-Hilbert action and predicts for the Newtonian limit the same lifetimes of superpositions as the gravity-based approaches of Diosi and Penrose. A second important feature of the Dynamical Spacetime approach is its capability to forecast reduction probabilities. It can explain why all experiments performed so-far confirm Born's rule, and predict deviations from it, when solids evolve into three-state superpositions. The basics needed for the derivations in this paper are developed in Part 1 by an analysis of semiclassical gravity.
I argue that there is a straightforward way to understand the occurrence of wavefunction collapses or 'quantum events' in relational approaches to quantum mechanics: we necessarily encounter a discontinuity in our description when a system interacts with the reference relative to which we are describing it, since the reference system cannot be described relative to itself. This makes it clear how recent concerns around quantum events in relational quantum mechanics should be resolved. However, the solution requires accepting that quantum mechanics is not a complete description of all physical facts, and moreover I argue that this is most likely inevitable if we want to be able to give a precise description of quantum events.
This paper is an in depth implementation of the proposal (Ellis 2012 Ann. Phys. NY 327 1890–932) that the quantum measurement issue can be resolved by carefully looking at top-down contextual effects within realistic measurement contexts. The specific setup of the measurement apparatus determines the possible events that can take place. The interaction of local heat baths with a quantum system plays a key role in the process. In contrast to the usual attempts to explain quantum measurement by decoherence, we argue that the heat bath follows unitary time evolution only over limited length and time scales (Drossel 2017 His. Phil. Sci. B 58 12–21) and thus leads to localization and stochastic dynamics of quantum particles that interact with it. We show furthermore that a theory that describes all the steps from the initial arrival of the quantum particle to the final pointer deflection must use elements from classical physics. This proposal also provides a contextual answer to the puzzle of the origin of the arrow of time when quantum measurements take place: it derives from the cosmological direction of time. Overall, our proposal is for contextual wavefunction collapse.