Engineer, S., Rivlin, T., Wollmann, S., Malik, M., & Lock, M. P. E. (2026). Equilibration of objective observables in a dynamical model of quantum measurements. Physical Review A, 113(3), Article 032205. https://doi.org/10.1103/lkqb-jdmg
E141-08 - Forschungsbereich Quantum Optics and Quantum Information
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Journal:
Physical Review A
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ISSN:
2469-9926
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Date (published):
Mar-2026
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Number of Pages:
18
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Publisher:
AMER PHYSICAL SOC
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Peer reviewed:
Yes
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Keywords:
quantum theory; quantum thermodynamics; quantum foundations; quantum measurements; quantum Darwinism; equilibration on average
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Abstract:
The challenge of understanding quantum measurement persists as a fundamental issue in modern physics. Particularly, the abrupt and energy-nonconserving collapse of the wave function appears to contradict classical thermodynamic laws. The contradiction can be resolved by considering measurement itself to be an entropyincreasing process, driven by the second law of thermodynamics. One such resolution explains the apparently irreversible emergence of objective outcomes in an isolated, unitarily evolving quantum system via the theory of closed-system equilibration. Working within this framework, we construct the set of “objectifying observables” that best encode the measurement statistics of a system in an objective manner and establish a measurement error bound to quantify the probability an observer will obtain an incorrect measurement outcome. Using this error bound, we show that the objectifying observables readily equilibrate on average under the set of Hamiltonians which preserve the outcome statistics on the measured system. Using a random matrix model for this set, we numerically determine the measurement error bound, finding that the error only approaches zero with increasing environment size when the environment is coarse grained into so-called observer systems. This indicates the necessity of coarse graining an environment for the emergence of objective, classical measurement outcomes.
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Project title:
Die Thermodynamik von Messungen und isolierten Quantensystemen: ESP7464924 (FWF - Österr. Wissenschaftsfonds) Emergence of Objective Reality: from Qubit to Oscilloscope: ID: 62423 (John Templeton Foundation) Control and complexity in quantum statistical mechanics: 101043705 (European Commission)
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Project (external):
European Research Council (ERC) Starting grant PIQUaNT Marie Skłodowska-Curie Grant UK Engineering and Physical Sciences Research Council European Research Council (ERC) Starting grant PIQUaNT