Measurement theory for closed quantum systems

2014/04/28 by Michiel Wouters, Wouters, Michiel
Computer Science · Physics and Astronomy · #FOS: Physical sciences #Quantum Information and Cryptography #Quantum Mechanics and Applications #Quantum Physics (quant-ph) #Quantum many-body systems

paper · pdf · doi:10.48550/arxiv.1404.6963

openalex publication_date 2014/04/28 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28

Abstract

We introduce the concept of a "classical observable" as an operator with vanishingly small quantum fluctuations on a set of density matrices. It is shown how to construct them for a time evolved pure state. The study of classical observables provides a natural starting point to analyse the quantum measurement problem. In particular, it allows to identify Schrödinger cats and the associated projection operators intrinsically, without the need to invoke an environment. We discuss how our new approach relates to the open system analysis of the quantum measurement problem.

Citations

• Microscopic diagonal entropy and its connection to basic thermodynamic relations
• Decoherence, einselection, and the quantum origins of the classical

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