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apr10-offprint-hardy.pdf

“Quantum foundations” is the field of physics that seeks to understand what quantum theory is telling us about the nature of reality. Researchers hope to answer questions such as: What do the elements of the mathematical formalism of quantum theory represent? From what physical principles can the formalism be derived? What are the precise ways in which a quantum world differs from a classical world and other possible worlds? Progress on these questions is likely to come both from an operational approach, wherein one characterizes a theory entirely in terms of the predictions for macroscopic experiments described using everyday concepts, and from a realist approach, wherein one seeks to find deeper explanations for these predictions in terms of simple entities and abstract concepts. We illustrate the practical significance of foundational research by recalling the role that it played as a spawning ground for the field of quantum information science, and we explain why we think that it will have a similar role to play in unifying quantum theory with general relativity.