Quantum theory of the classical: quantum jumps, Born's Rule and objective classical reality via quantum Darwinism

The emergence of the classical from the quantum substrate is a long-standing conundrum. I will describe three insights into the transition from quantum to classical based on recognition of the role of the environment [1]. I will first derive preferred sets of states that define what exists -- our everyday classical reality. They arise as a result of breaking of the unitary symmetry of the Hilbert space resulting from the conflict between linearity of quantum evolutions and nonlinearities inherent in the process of amplification -- of replicating information. This accounts for quantum jumps and the emergence of the preferred pointer states consistent with those obtained via environment-induced superselection, (einselection), but is accomplished without the usual tools of decoherence. Pointer states determine what can happen -- define events -- without appealing to probabilities. Therefore, Born’s Rule can now be deduced from entanglement-assisted invariance, or envariance -- a symmetry of entangled quantum states. Envariance also provides new basis for statistical physics, allowing one to deduce thermodynamics from symmetries of entanglement -- that is, without the need for ensembles [2]. Information flows accompanying decoherence explain how the perception of objective classical reality arises from the quantum substrate: the effective amplification they represent accounts for the objective existence of the einselected states of macroscopic quantum systems through redundancy of their records in the environment -- through quantum Darwinism [1].

[1] W. H. Zurek (2018) Quantum theory of the classical: quantum jumps, Born's Rule and objective classical reality via quantum Darwinism, Phil. Trans. Roy. Soc. A 376 Article #20180107 DOI:10.1098/rsta.2018.0107

[2] W. H. Zurek (2018) Eliminating ensembles from equilibrium statistical physics: Maxwell’s demon, Szilard’s engine, and thermodynamics via entanglement, Phys. Rep. 755, pp. 1-21 doi.org/10.1016/j.physrep.2018.04.003