Decoherence, einselection, and the quantum origins of the classical

By Wojciech H. Zurek. 2001

3,734 citations recorded by the source corpus.

as quantum engineering. In the past two decades it has become increasingly clear that many (perhaps all) of the symptoms of classicality can be induced in quantum systems by their environments. Thus decoherence is caused by the interaction in which the environment in effect monitors certain observables of the system, destroying coherence between the pointer states corresponding to their eigenvalues. This leads to environment-induced superselection or einselection, a quantum process associated with selective loss of information. Einselected pointer states are stable. They can retain correlations with the rest of the universe in spite of the environment. Einselection enforces classicality by imposing an effective ban on the vast majority of the Hilbert space, eliminating especially the flagrantly nonlocal ''Schrodinger-cat states.'' The classical structure of phase space emerges from the quantum Hilbert space in the appropriate macroscopic limit. Combination of einselection with dynamics leads to the idealizations of a point and of a classical trajectory. In measurements, einselection replaces quantum entanglement between the apparatus and the measured system with the classical correlation. Only the preferred pointer observable of the apparatus can store information that has predictive power. When the measured quantum system is microscopic and isolated, this restriction on the predictive utility of its correlations with the macroscopic apparatus results in the effective ''collapse of the wave packet.'' The existential interpretation implied by einselection regards observers as open quantum systems, distinguished only by their ability to acquire, store, and process information. Spreading of the correlations with the effectively classical pointer states throughout the environment allows one to understand ''classical reality'' as a property based on the relatively objective existence of the einselected states. Effectively classical pointer states can be ''found out'' without being re-prepared, e.g, by intercepting the information already present in the environment. The redundancy of the records of pointer states in the environment (which can be thought of as their ''fitness'' in the Darwinian sense) is a measure of their classicality. A new symmetry appears in this setting. Environment-assisted invariance or envariance sheds new light on the nature of ignorance of the state of the system due to quantum correlations with the environment and leads to Born's rules and to reduced density matrices, ultimately justifying basic principles of the program of decoherence and einselection.

Subfields: Artificial Intelligence, Atomic and Molecular Physics, and Optics

View Paper: https://www.semanticscholar.org/paper/fc9f147b969157cd23e06748db4b798a33db90cc

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Citations in the corpus

Quantum Information and Relativity Theory (2002, background): “A reassessment of this issue and many important technical details were recently published by Zurek (2002, 2003).”
Colloquium: Quantum interference of clusters and molecules (2011, background): “This distinction of states with welldefined position can be explained within the framework of quantum mechanics by the concept of environmental decoherence (Joos et al., 2003; Schlosshauer, 2007; Zurek, 2003).”
Phase space representation of quantum dynamics (2009, methodology): “(Zurek, 2003)) Ẇ = {H,W} − ~ 2 223!”
Decoherence, the measurement problem, and interpretations of quantum mechanics (2003, methodology): “…for example, have been based on the von Neumann entropy −Trρ2Ψ(t) ln ρ2Ψ(t), or the purity Trρ2Ψ(t), with the goal of finding the most robust states or the states which become least entangled with the environment in the course of the evolution (Zurek, 1993, 1998, 2003b; Zurek et al., 1993).”
Harnessing the Power of the Second Quantum Revolution (2020, background): “How is quantum coherence lost when going from the microscopic to the macroscopic [4,38]?”
Decoherence, entanglement and irreversibility in quantum dynamical systems with few degrees of freedom (2008, background): “Accordingly, claims have been made of an environment-induced entropy production governed by the system’s Lyapunov exponent λ (Monteoliva and Paz, 2000; Pattanayak, 1999; Zurek, 2003), without rigorous analytical derivation, nor strong numerical evidence (Refs.”
Universal decoherence due to gravitational time dilation (2013, background): “A prominent role in this transition is commonly attributed to decoherence [4, 5]: due to interaction with an external environment, a particle gets entangled with its environment and loses its quantum coherence.”
Quantum interference experiments with large molecules (2003, methodology): “We are currently witnessing an experimental race to reach the ground state using different set-ups, such as nano- or microcantilevers [12], membranes [13], or vibrating microtoroids [14].”