Rapid Decoherence of Complex Systems: Why Macroscopic Objects Cannot Sustain Quantum Superpositions

Runbiao Fang

Macroscopic Quantum States: When Macroscopic Objects Enter Quantum Superposition

Itamar J. Allali, Mark P. Hertzberg

Quantum mechanics allows for states in macroscopic superpositions, but they ordinarily undergo rapid decoherence due to interactions with their environment. A system that only interacts gravitationally, such as an arrangement of dark matter (DM), may exhibit slow decoherence. In this letter, we compute the decoherence rate of a quantum object in general relativity. For axion DM in a superposition of the field's phase, we find that DM in the Milky Way is robust against decoherence, while a spatial superposition is not. This novel phase behavior may be relevant to direct detection experiments.

박채연

Daniel Braun, Petr A. Braun, Fritz Haake

Itamar J. Allali, Mark P. Hertzberg

Quantum mechanics allows for states in macroscopic superpositions, but they ordinarily undergo rapid decoherence due to interactions with their environment. A system that only interacts gravitationally, such as an arrangement of dark matter (DM), may exhibit slow decoherence. In this Letter, we compute the decoherence rate of a quantum object within general relativity, focusing on superposed metric oscillations; a rare quantum general relativistic result. For axion DM in a superposition of the field's phase, we find that DM in the Milky Way is robust against decoherence, while a spatial superposition is not. This novel phase behavior may impact direct detection experiments.

Douglas H. M. FULBER

Abstract We derive a fundamental limit on the mass of objects capable of sustaining spatial superpositions, based on the Bekenstein entropy bound and the holographic principle. We show that the dimension of the Hilbert space required to describe distinguishable macroscopic states grows exponentially with mass, eventually exceeding the information capacity of the bounding surface area. This imposes a structural "Holographic Cutoff" at a critical mass scale M_c ~ 10^-14 kg. Unlike Continuous Spontaneous Localization (CSL) models which predict a gradual decoherence, our analysis predicts a discontinuous loss of interference visibility at M_c. We propose a test using levitated nanoparticle interferometry that can distinguish this intrinsic bound from environmental decoherence. Files in this Record AHolographicBound...pdf: The condensed 4-page Letter (PRL-style submission). No-ScaleTheorem...pdf: The extended manuscript ("Paper") with full derivations and visualizations. Keywords: Quantum Measurement Problem, Holographic Principle, Bekenstein Bound, Macroscopic Superposition, Quantum Gravity, Talbot-Lau Interferometry.