How to Minimize the Decoherence Caused by Black Holes

Fuente: arXiv
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Auteurs principaux: Danielson, Daine L., Kudler-Flam, Jonah, Satishchandran, Gautam, Wald, Robert M.
Format: Preprint
Publié: 2025
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author Danielson, Daine L.
Kudler-Flam, Jonah
Satishchandran, Gautam
Wald, Robert M.
author_facet Danielson, Daine L.
Kudler-Flam, Jonah
Satishchandran, Gautam
Wald, Robert M.
contents We consider an experimentalist, Alice, who creates a quantum superposition of a charged or massive body outside of a black hole (or, more generally, in the presence of a Killing horizon). It was previously shown that emission of soft photons/gravitons into the black hole will result in the decoherence of the components of the superposition if it is held open for a sufficiently long span of time. However, at any finite time, $t_c$, during the process, it is not obvious how much decoherence has irrevocably occurred. Equivalently, it is not obvious how much information an observer inside the black hole can extract about Alice's superposition prior to time $t_c$. In this paper, we solve for the optimal experimental protocol to be followed by Alice for $t > t_c$ so as to minimize the decoherence of the components of her superposition. More precisely, given the entangling radiation that has passed through the horizon prior to the cross-section $\mathcal C$ corresponding to the time $t = t_c$ in Alice's lab, we determine the "optimal purification" of this radiation beyond $\mathcal C$ such that the global quantum state of the radiation through the horizon has maximal overlap (quantum fidelity) with the Hartle-Hawking or Unruh vacuum. Due to the intricate low frequency entanglement structure of the quantum field theory vacuum state, we find this optimal purification to be nontrivial. In particular, even if Alice has already "closed" her superposition by bringing the components back together, we find that she can decrease the net decoherence of the components of her superposition somewhat by re-opening it and performing further manipulations.
format Preprint
id arxiv_https___arxiv_org_abs_2501_04773
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle How to Minimize the Decoherence Caused by Black Holes
Danielson, Daine L.
Kudler-Flam, Jonah
Satishchandran, Gautam
Wald, Robert M.
High Energy Physics - Theory
General Relativity and Quantum Cosmology
Quantum Physics
We consider an experimentalist, Alice, who creates a quantum superposition of a charged or massive body outside of a black hole (or, more generally, in the presence of a Killing horizon). It was previously shown that emission of soft photons/gravitons into the black hole will result in the decoherence of the components of the superposition if it is held open for a sufficiently long span of time. However, at any finite time, $t_c$, during the process, it is not obvious how much decoherence has irrevocably occurred. Equivalently, it is not obvious how much information an observer inside the black hole can extract about Alice's superposition prior to time $t_c$. In this paper, we solve for the optimal experimental protocol to be followed by Alice for $t > t_c$ so as to minimize the decoherence of the components of her superposition. More precisely, given the entangling radiation that has passed through the horizon prior to the cross-section $\mathcal C$ corresponding to the time $t = t_c$ in Alice's lab, we determine the "optimal purification" of this radiation beyond $\mathcal C$ such that the global quantum state of the radiation through the horizon has maximal overlap (quantum fidelity) with the Hartle-Hawking or Unruh vacuum. Due to the intricate low frequency entanglement structure of the quantum field theory vacuum state, we find this optimal purification to be nontrivial. In particular, even if Alice has already "closed" her superposition by bringing the components back together, we find that she can decrease the net decoherence of the components of her superposition somewhat by re-opening it and performing further manipulations.
title How to Minimize the Decoherence Caused by Black Holes
topic High Energy Physics - Theory
General Relativity and Quantum Cosmology
Quantum Physics
url https://arxiv.org/abs/2501.04773