Richard Healey: Correlations, probabilities and quantum states

The speaker opens the conference by welcoming attendees and setting the stage for a discussion on the intersection of quantum mechanics and information theory. They highlight the importance of understanding quantum mechanics from different perspectives, acknowledging the diversity in knowledge levels and interpretations among the participants. The conference celebrates the publication of Jeffrey Boop's book, 'Banana World,' and its influence on the field. The speaker also marks the anniversary of John Bell's seminal paper on hidden variables and the foundational contributions of David Bohm and Yakir Aharonov, emphasizing the evolution of discussions on quantum foundations and the shift towards viewing quantum mechanics through the lens of quantum information theory.

The speaker delves into a comparison of his views with those of Jeffrey on understanding quantum theory, focusing on broad strokes rather than the intricate details of the book. They find common ground in the rejection of certain interpretations, such as realist views including Bohmian mechanics and Everettian approaches, as well as the insufficiency of instrumentalist interpretations. The speaker discusses the concept of probabilistic correlations in quantum theory, disagreeing with the notion that the quantum state vector represents knowledge or reality. Instead, they propose a pragmatist view where quantum theory is about the structure of information and the probabilistic correlations it predicts, which are distinct from classical theories.

The speaker explores the concept of probabilistic correlations in quantum theory, challenging the idea that they are determined by statistical data. They argue that probabilistic phenomena are abstract and not directly constituted by data, using the example of coin flips to illustrate the difference between a manifestation of probability and a single instance that is compatible with it. The speaker also addresses the disagreement on what constitutes 'realizable' correlations, suggesting that Bell's theorem and the concept of non-locality are misunderstood and that quantum theory itself may offer a way to explain non-localized correlations without invoking action at a distance.

The speaker discusses the function of quantum states and their role in providing probabilities for magnitude claims through the Born rule. They emphasize the importance of the context in which quantum theory is applied, suggesting that the theory itself is not about predicting observations but rather about the probabilistic correlations that are of interest to agents. The speaker also touches on the concept of agency, differentiating between passive observers and agents capable of applying quantum theory to achieve certain outcomes, and the significance of environmental decoherence in determining which magnitude claims have well-defined content for the application of the Born rule.

The speaker addresses the concept of change in the context of quantum mechanics and relativity, challenging the notion of a universal time to which change is relativized. They argue that change should be understood with respect to space-time points rather than time slices, suggesting that the idea of predetermination in quantum mechanics is not about time slices but about the probabilities assigned to events at specific space-time points. The speaker also discusses the implications of this view for the understanding of quantum entanglement and the nature of quantum states, emphasizing the importance of the environment in determining the content of magnitude claims.