Quantum Nonlocality: Myth and Reality

Quantum mechanics is, like classical mechanics, a local theory: one system cannot influence another system with which it does not interact. Claims to the contrary based on quantum violations of Bell inequalities are shown to be incorrect. A specific example traces a violation of the CHSH Bell inequality in the case of a spin-3/2 particle to the noncommutation of certain quantum operators in a situation where (non)locality is not an issue. A consistent analysis of what quantum measurements measure, in terms of quantum properties, is used to identify the basic error in derivations of Bell inequalities: the use of classical concepts (hidden variables) rather than a probabilistic structure appropriate to the quantum domain. The flaw in the original Einstein-Podolsky-Rosen (EPR) argument for the incompleteness of quantum mechanics is traced to a counterfactual argument which is not valid if one assumes that Hilbert-space quantum mechanics is complete; locality is not an issue. The quantum correlations that violate Bell inequalities can be understood using local quantum common causes. Wavefunction collapse and Schr\"odinger steering are calculational procedures, not physical processes. A general Principle of Einstein locality rules out nonlocal influences between noninteracting quantum systems. Some suggestions are made for changes in terminology that could clarify discussions of quantum foundations and be less confusing to students.