We study the unique role played in quantum mechanics by non-events or 'counterfactuals'. Our earlier analysis of 'quantum oblivion' has revealed some subtle stages in the measurement process, which may end up in self-cancellation. To these findings, we now add two insights derived by two time-symmetric interpretations of quantum mechanics. (i) Like all quantum interactions, the non-event is formed by the conjunction of forward-plus-backward-evolving wave functions. (ii) Then, it is another feature of such dual evolutions, namely the involvement of negative masses and energies, that enables Nature to make some events 'unhappen' while leaving causal traces.
We study the unique role played in quantum mechanics by non-events or 'counterfactuals'. Our earlier analysis of 'quantum oblivion' has revealed some subtle stages in the measurement process, which may end up in self-cancellation. To these findings, we now add two insights derived by two time-symmetric interpretations of quantum mechanics. (i) Like all quantum interactions, the non-event is formed by the conjunction of forward-plus-backward-evolving wave functions. (ii) Then, it is another feature of such dual evolutions, namely the involvement of negative masses and energies, that enables Nature to make some events 'unhappen' while leaving causal traces.
Counterfactuals, i.e., events that could have occurred but eventually did not, play a unique role in quantum mechanics in that they exert causal effects despite their non-occurrence. They are therefore vital for a better understanding of quantum mechanics (QM) and possibly the universe as a whole. In earlier works, we have studied counterfactuals both conceptually and experimentally. A fruitful framework termed quantum oblivion has emerged, referring to situations where one particle seems to "forget" its interaction with other particles despite the latter being visibly affected. This framework proved to have significant explanatory power, which we now extend to tackle additional riddles. The time-symmetric causality employed by the Two State-Vector Formalism (TSVF) reveals a subtle realm ruled by "weak values," already demonstrated by numerous experiments. They offer a realistic, simple and intuitively appealing explanation to the unique role of quantum non-events, as well as to the foundations of QM. In this spirit, we performed a weak value analysis of quantum oblivion and suggest some new avenues for further research.
TWO INTERPRETATIONS OF SPATIO-TEMPORAL COUNTERFACTUALSne general (and straightforward) observation which can be made based on chapters 3 and 4 is that there is more than one way to employ Lewis's semantic framework for counterfactual conditionals in the analysis of quantum entangled states.The main reason is that, as we indicated at the end of chapter 2, there may be various ways to define the similarity relation between possible worlds, and this relation is indispensable for the evaluation of counterfactual statements.To characterize the relation of similarity it is necessary to decide which facts from the actual world are salient with respect to the affinity of possible worlds with it, and which are not.We have already reiterated (and this assessment is unanimously, if mostly tacitly, accepted by all who make use of Lewis's semantics in quantum mechanics) that in the context of the quantummechanical phenomena there is no room for law-breaking possible worlds; therefore Lewis's requirement that the number of unlawful events ("miracles") be minimized cannot act as a criterion of similarity between possible worlds.Only singular, individual and contingent facts can set one possible world apart from another, and only such facts can be taken into account when comparing possible worlds with respect to their affinity with the actual world.But it has already been argued that not all facts taking place in the actual world should count towards similarity.It is imperative, then, to make clear how to tell apart those facts that count from those that do not. "ASYMMETRY BY FIAT" SOLUTION REVIVEDIt seems evident that two dominant intuitions regarding the evaluation of quantum counterfactuals have emerged from the extensive discussion in the two previous chapters.However, it will be much more convenient to describe them in terms of extensions to one of Lewis's alternative approaches to counterfactuals rather than in terms of the similarity relation.As we recall (sec.2.3.3),Lewis indicates that the problem with the temporal asymmetry of counterfactuals can find its solution not only within his O 1 It should be stressed, however, that some authors question the assumed asymmetry of counterfactual dependence.For example H. Price, who defends the idea of backward causation, argues that when evaluating counterfactuals we should hold fixed not the past of the antecedent-event, but rather what is epistemologically accessible to us (see Price 1996, pp.169-170, 178-179).2 It is a matter of choice whether to include or exclude the surface of the light cones in the respective "pasts" of e.We will follow the convention according to which, in the first case, the surface of the forward light cone is excluded from the past, but in the second case the surface of the backward light cone is included in it.
A new interpretation of quantum mechanics, similar to the Copenhagen interpretation, is developed from time-symmetry arguments and commonly held principles concerning time and causality. These principles, which are grounded in ideas outside of quantum mechanics, suggest that the strange features and paradoxes of quantum mechanics come from backward causation, in which future events can change the past. Using these principles this paper gives a better understanding of (and reasons for) stationary states, tunneling, wave-particle duality, the measurement problem with the collapse of the state vector, Hardy's paradox, non-locality, and the EPR paradox. These are only a few of the interpretational successes, and the model will be contrasted to other popular and/or recent interpretations. Unfortunately, this model is metaphysical, without any predictive power.
Among the (in)famous differences between classical and quantum mechanics, quantum counterfactuals seem to be the most intriguing. At the same time, they seem to underlie many quantum oddities. In this article, we propose a simple explanation for counterfactuals, on two levels. Quantum Oblivion (QO) is a fundamental type of quantum interaction that we prove to be the origin of quantum counterfactuals. It also turns out to underlie several well-known quantum effects. This phenomenon is discussed in the first part of the article, yielding some novel predictions. In the second part, a hypothesis is offered regarding the unique spacetime evolution underlying QO, termed Quantum Hesitation (QH). The hypothesis invokes advanced actions and interfering weak values, as derived first by the Two-State-Vector Formalism (TSVF). Here too, weak values are argued to underlie the familiar "strong" quantum values. With these, an event that appears to have never occurred can exert causal effects and then succumb to QO by another time-evolution involving negative weak values that eliminate them. We conclude with briefly discussing the implications of these ideas on the nature of time.
This paper proposes an interpretation of quantum mechanics, relying on the time-symmetric stochastic dynamics of quantum particles and on non-classical probability theory. Our main purpose is to demonstrate that the wave function and its complex conjugate can be interpreted as complex probability distributions in two complex diffusion equations related to non-real forward and backward in time stochastic motions respectively. We say non-real because Schroedinger forward and backward diffusions describe both reversible (real trajectories) and irreversible trajectories (non-real trajectories). The reversible trajectories are the only real trajectories and are given by the intersection of those forward and backward processes. It turns out that if we translate this intersection using set-theoretic language, we are led to a reversible diffusion described by Born rule probabilities. This proposal is useful also for explaining more about the role of complex numbers in quantum mechanics that produces this so-called "wave-like" nature of quantum reality. Our perspective also challenges the notion of physical superposition and aims at a derivation of superposition principle not based on the linearity of Schroedinger's equation but relying on pure probability theory. Moreover, it is suggested that, embracing the idea of stochastic processes in quantum theory, explains the reasons for the appearance of classical behavior in large objects, in contrast to the quantum behavior of small ones. In other words, we claim that a combination of a probabilistic and no-ontic view (neither epistemic though) of the wave function with a stochastic hidden-variables approach, may provide some insight into the quantum physical reality and potentially establish the groundwork for a novel interpretation of quantum mechanics.