Testing the reality of the quantum state

Matthew F. Pusey, Jonathan Barrett, Terry Rudolph

Matthew F. Pusey, Jonathan Barrett, Terry Rudolph

Abner Shimony

F. Pat Eblen

Draft preprint paper abstract: Bell tests have occupied a central role in the interpretation of quantum mechanics for over sixty years, widely regarded as definitive evidence for quantum nonlocality and the impossibility of local hidden-variable theories. We argue that this centrality is methodologically misplaced. Bell test outcome functionals are many-to-one maps that collapse a physically rich quantum state into a single binary value per trial, discarding the overwhelming majority of the physical information and actualities present. Conclusions about quantum reality drawn from such maximally coarse-grained outputs cannot be regarded as definitive descriptions of the underlying ontic state. By contrast, three independent and universal physical constraints — the Heisenberg Uncertainty Principle (HUP), the thermodynamic requirement of strictly nonzero entropy, and the Bekenstein entropy bound — each mandate irreducible dispersion in every physical process without exception. We propose that these pervasive, filter-free, and theoretically convergent constraints constitute stronger foundational evidence about quantum reality than Bell test statistics, and we examine the implications for the nonlocality interpretation. We do not claim Bell’s theorem is mathematically incorrect; we claim its physical regime is too narrow to support the sweeping ontological conclusions commonly attributed to it.

Johan Hansson

Bell's theorem, and its experimental tests, has shown that the two premises for Bell's inequality—locality and objective reality—cannot both hold in nature, as Bell's inequality is broken. A simple test is proposed, which for the first time may decide which alternative nature actually prefers on the fundamental, quantum level. If each microscopic event is truly random (e.g., as assumed in orthodox quantum mechanics) objective reality is not valid whereas if each event is described by an unknown but deterministic mechanism (“hidden variables”) locality is not valid. This may be analyzed and decided by the well-known reconstruction method of Ruelle and Takens; in the former case no structure should be discerned, in the latter a reconstructed structure should be visible. This could in principle be tested by comparing individual “hits” in a double-slit experiment, but in practice a single fluorescent atom, and its (seemingly random) temporal switching between active/inactive states would possibly be better/more practical, easier to set up, observe, and analyze. However, only imagination limits the list of possible experimental setups.