Quantum Information in Relativity: The Challenge of QFT Measurements

Anastopoulos, Charis; Savvidou, Ntina

doi:10.3390/e24010004

Cited by 14 publications

(17 citation statements)

References 97 publications

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“…The stock answer to this question in the literature [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] is as follows. There are certain non-trivial mathematical differences between QFT and non-relativistic quantum theory which disallow us from directly transplanting our non-relativistic measurement theory into QFT.…”

Section: What Blocks Their Way Homementioning

confidence: 99%

“…Firstly, is this need recognized? Unfortunately not, as far as I am aware only a few theoretical research groups [5,[7][8][9][10][11][13][14][15] are engaged with these topics and very few experimental groups make use of explicit Figure 8. This figure shows the three ways that one can approach and cross a QFT-cut: horizontal moves, diagonal cuts and vertical cuts.…”

Section: The State Of the Artmentioning

confidence: 99%

“…III will answer this question. As a growing portion of the physics community is now becoming aware [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21], the hand-wavy measurement models for QFT described in most textbooks on quantum field theory, quantum optics and particle physics are deeply unphysical and unsatisfying. Why is this so?…”

Section: Introduction: a Quantum Measurement Problemmentioning

confidence: 99%

“…It is often said [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] that the unphysical nature of these textbook measurement models can be traced to certain non-trivial mathematical differences between QFT and non-relativistic quantum theory (e.g., new causal and algebraic structures at play). These differences disallow us from directly transplanting our non-relativistic quantum measurement theory into QFT.…”

Section: Introduction: a Quantum Measurement Problemmentioning

confidence: 99%

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The Pragmatic QFT Measurement Problem and the need for a Heisenberg-like Cut in QFT

Grimmer¹

2022

Preprint

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Section: What Blocks Their Way Homementioning

confidence: 99%

Section: The State Of the Artmentioning

confidence: 99%

Section: Introduction: a Quantum Measurement Problemmentioning

confidence: 99%

Section: Introduction: a Quantum Measurement Problemmentioning

confidence: 99%

See 2 more Smart Citations

The Pragmatic QFT Measurement Problem and the need for a Heisenberg-like Cut in QFT

Grimmer¹

2022

Preprint

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“…Current QIT is problematic when basic relativistic principles both special and general -such as causality and covariance, need be accounted for. A relativistic QIT that expresses all informational notions in terms of quantum fields is currently missing, largely because of difficulties in formulating a comprehensive QFT theory of measurement [3].…”

Section: Problems With Treating Qft As Quantum Channelmentioning

confidence: 99%

Gravity, Quantum Fields and Quantum Information: Problems with classical channel and stochastic theories

Anastopoulos,

2022

Preprint

Self Cite

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In recent years an increasing number of papers attempt to mimic or supplant quantum field theory in discussions of issues related to gravity by the tools and through the perspective of quantum information theory, often in the context of alternative quantum theories. In this essay, we point out three common mistakes or inconsistencies in such treatments. First, we show that the notion of interactions mediated by an information channel is not, in general, equivalent to the treatment of interactions by quantum field theory. When used to describe gravity, this notion may lead to inconsistencies with general relativity. Second, we point out that in general one cannot replace a quantum field by that of classical stochastic sources, or mock up the effects of quantum fluctuations by classical noises, because in so doing important quantum features such as coherence and entanglement will be left out. Third, we explain how under specific conditions semi-classical and stochastic theories indeed can be formulated from their quantum origins and play a role at certain regimes of interest.-Prepared for Entropy: Special Issue on Quantum Information in Quantum Gravity.

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Eliminating the ‘Impossible’: Recent Progress on Local Measurement Theory for Quantum Field Theory

Papageorgiou,

Fraser

2024

Found Phys

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Arguments by Sorkin (Impossible measurements on quantum fields. In: Directions in general relativity: proceedings of the 1993 International Symposium, Maryland, vol 2, pp 293–305, 1993) and Borsten et al. (Phys Rev D 104(2), 2021. https://doi.org/10.1103/PhysRevD.104.025012) establish that a natural extension of quantum measurement theory from non-relativistic quantum mechanics to relativistic quantum theory leads to the unacceptable consequence that expectation values in one region depend on which unitary operation is performed in a spacelike separated region. Sorkin [1] labels such scenarios ‘impossible measurements’. We explicitly present these arguments as a no-go result with the logical form of a reductio argument and investigate the consequences for measurement in quantum field theory (QFT). Sorkin-type impossible measurement scenarios clearly illustrate the moral that Microcausality is not by itself sufficient to rule out superluminal signalling in relativistic quantum theories that use Lüders’ rule. We review three different approaches to formulating an account of measurement for QFT and analyze their responses to the ‘impossible measurements’ problem. Two of the approaches are: a measurement theory based on detector models proposed in Polo-Gómez et al. (Phys Rev D, 2022. https://doi.org/10.1103/physrevd.105.065003) and a measurement framework for algebraic QFT proposed in Fewster and Verch (Commun Math Phys 378(2):851–889, 2020). Of particular interest for foundations of QFT is that they share common features that may hold general morals about how to represent measurement in QFT. These morals are about the role that dynamics plays in eliminating ‘impossible measurements’, the abandonment of the operational interpretation of local algebras $${\mathcal {A}}(O)$$ A ( O ) as representing possible operations carried out in region O, and the interpretation of state update rules. Finally, we examine the form that the ‘impossible measurements’ problem takes in histories-based approaches and we discuss the remaining challenges.

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Quantum Information in Relativity: The Challenge of QFT Measurements

Cited by 14 publications

References 97 publications

The Pragmatic QFT Measurement Problem and the need for a Heisenberg-like Cut in QFT

The Pragmatic QFT Measurement Problem and the need for a Heisenberg-like Cut in QFT

Gravity, Quantum Fields and Quantum Information: Problems with classical channel and stochastic theories

Eliminating the ‘Impossible’: Recent Progress on Local Measurement Theory for Quantum Field Theory

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