We suggest solving the measurement problem by postulating the existence of a special future final boundary condition for the universe. Although this is an extension of the way boundary conditions are usually chosen (in terrestrial laboratories), it is our only deviation from standard quantum mechanics. Using two state vectors, or the "two-state", to describe completely the state of systems of interest, we analyze ideal and "weak" measurements, and show the consistency of our scheme. If the final state of a measuring device is assigned to be one of the possible outcomes of the measurement, an effective reduction is observed after an ideal measurement process. For final conditions chosen with an appropriate distribution, the predictions of standard quantum mechanics may be reconstructed, thus eliminating probability from the description of any single measurement. The interpretation attained, the Teleological Interpretation, is an ontological one; it is local and deterministic. Other special assumptions in the choice of the final boundary condition may explain certain unaccounted for phenomena, or even supply a mechanism for essential free will. In this context we believe that a new conception of time should be adopted.
We suggest solving the measurement problem by postulating the existence of a special future final boundary condition for the universe. Although this is an extension of the way boundary conditions are usually chosen (in terrestrial laboratories), it is our only deviation from standard quantum mechanics. Using two state vectors, or the "two-state", to describe completely the state of systems of interest, we analyze ideal and "weak" measurements, and show the consistency of our scheme. If the final state of a measuring device is assigned to be one of the possible outcomes of the measurement, an effective reduction is observed after an ideal measurement process. For final conditions chosen with an appropriate distribution, the predictions of standard quantum mechanics may be reconstructed, thus eliminating probability from the description of any single measurement. The interpretation attained, the Teleological Interpretation, is an ontological one; it is local and deterministic. Other special assumptions in the choice of the final boundary condition may explain certain unaccounted for phenomena, or even supply a mechanism for essential free will. In this context we believe that a new conception of time should be adopted.
We suggest an interpretation of quantum mechanics, inspired by the ideas of Aharonov et al. of a time-symmetric description of quantum theory. We show that a special final boundary condition for the Universe, may be consistently defined as to determine single classical-like measurement outcomes, thus solving the "measurement problem". No other deviation is made from standard quantum mechanics, and the resulting theory is deterministic (in a two-time sense) and local. Quantum mechanical probabilities are recovered in general, but are eliminated from the description of any single measurement. We call this the Two-time interpretation of quantum mechanics. We analyze ideal measurements, showing how the quantum superposition is, in effect, dynamically reduced to a single classical state via a "two-time decoherence" process. We discuss some philosophical aspects of the suggested interpretation. We also discuss weak measurements using the two-time formalism, and remark that in these measurement situations, special final boundary conditions for the Universe, might explain some unaccounted for phenomena.
Accepting a time-symmetric quantum dynamical world with ontological wave functions or fields, we follow arguments that naturally lead to a two-boundary interpretation of quantum mechanics. The usual two boundary picture is a valid superdeterministic interpretation. It has, however, one unsatisfactory feature. The random selection of a chosen measurement path of the universe is far too complicated. To avoid it, we propose an alternate two-boundary concept called surjective mapping conjecture. It takes as fundamental a quantum-time running forward like the usual time on the wave-function side and backward on the complex conjugate side. Unrelated fixed arbitrary boundary conditions at the initial and the final quantum times then determine the measurement path of the expanding and contracting quantum-time universe in the required way.
Interpretation problems are eliminated from quantum theory by picturing a quantum history as having been sampled from a probability distribution over the set of histories which are permitted by all relevant boundary conditions. In laboratory physics, the final measurement plays a crucial role in defining the set of allowed histories by constraining the final state to be an eigenstate of the measurement operator. For the universe itself, a final boundary condition can play a similar role. Together with the special big bang initial state, the final constraint may ensure that the universe admits a classical description in the asymptotic future. Acknowledging the role of a future constraint dispels the mysteries of quantum theory without any amendment to the theory itself.
The (consistent or decoherent) histories interpretation provides a consistent realistic ontology for quantum mechanics, based on two main ideas. First, a logic (system of reasoning) is employed which is compatible with the Hilbert-space structure of quantum mechanics as understood by von Neumann: quantum properties and their negations correspond to subspaces and their orthogonal complements. It employs a special (single framework) syntactical rule to construct meaningful quantum expressions, quite different from the quantum logic of Birkhoff and von Neumann. Second, quantum time development is treated as an inherently stochastic process under all circumstances, not just when measurements take place. The time-dependent Schrödinger equation provides probabilities, not a deterministic time development of the world. The resulting interpretive framework has no measurement problem and can be used to analyze in quantum terms what is going on before, after, and during physical preparation and measurement processes. In particular, appropriate measurements can reveal quantum properties possessed by the measured system before the measurement took place. There are no mysterious superluminal influences: quantum systems satisfy an appropriate form of Einstein locality. This ontology provides a satisfactory foundation for quantum information theory, since it supplies definite answers as to what the information is about. The formalism of classical (Shannon) information theory applies without change in suitable quantum contexts, and this suggests the way in which quantum information theory extends beyond its classical counterpart.
ABSTRACT This essay aims at reviewing one of the major difficulties affecting the standard formulation of quantum mechanics, that is, the well‐known measurement problem. As it will be explained, the latter originates as a consequence of the quantum theory's postulates. Referring to this, we analyze in particular the conceptual issues implied by the projection (or collapse) rule. After having presented the measurement problem, we then illustrate three possible solutions offered by major interpretations of/alternatives to quantum theory: Bohmian mechanics, Ghirardi–Rimini–Weber theories, and the many‐worlds interpretation. As the reader will see, these theoretical frameworks solve this issue by virtue of their unambiguous ontologies and consistent dynamical laws. Finally, a synopsis of the open debates and future perspectives concerning the measurement problem in relativistic contexts concludes the paper.
Quantum mechanics is based on Schrodinger’s wave function with linear superposition of vectors in a Hilbert space. Due to superposition, multiple physical states are considered simultaneously for the same time point, but when the corresponding quantum mechanical experiments are realized, there is only one outcome and not a superposition of pointer positions. This observation characterizes the quantum mechanical measurement problem, which for about a century found multiple interpretations, which can be classified as potentiality, as proposed by Heisenberg, or as real physical entities, for instance fields. Potentialities are yet inexistent in reality and unobservable in the present, since they represent a possible future. Thus, they can only be an intra-mental representation of a future process and not a physical extra-mental process ongoing in the present. There is coexistence of a physical object observable in reality and a mental prediction by an observer concerning the future behavior of this object. The characterization of quantum mechanical formalism by some physicists corresponds to a prediction and therefore to a mental representation of the future behavior of elementary particles and not to a description of an ongoing extra-mental process. Prediction in life and science has some characteristics, which resemble the measurement problem, since it undergoes a “multiple to one” reduction of mental potentialities to only one observable real outcome. Besides quantum mechanics, such reductions can also be found with many kinds of predictions, in classical physics for regular and irregular dynamical processes and in humans for programming future actions. Superposition in classical physics only concerns variable effects, but in quantum mechanics includes variable effects and non-localizable causes. Quantum mechanics, interpreted as prediction of future outcomes with multiple potentialities but only one realization, would resemble the general prediction problem in life and science and thereby loos its weird aspects.