# Weekly Papers on Quantum Foundations (32)

Fundamental Limitation on the Detectability of Entanglement. (arXiv:2208.02518v1 [quant-ph])

Entanglement detection is essential in quantum information science and quantum many-body physics. It has been proved that entanglement exists almost surely for a random quantum state, while the realizations of effective entanglement criteria usually consume exponential resources, and efficient criteria often perform poorly without prior knowledge. This fact implies a fundamental limitation might exist in the detectability of entanglement. In this work, we formalize this limitation as a fundamental trade-off between the efficiency and effectiveness of entanglement criteria via a systematic method to theoretically evaluate the detection capability of entanglement criteria. For a system coupled to an environment, we prove that any entanglement criterion needs exponentially many observables to detect the entanglement effectively when restricted to single-copy operations. Otherwise, the detection capability of the criterion will decay double-exponentially. Furthermore, if multi-copy joint measurements are allowed, the effectiveness of entanglement detection can be exponentially improved, which implies a quantum advantage in entanglement detection problems.

Bulk Locality and Asymptotic Causal Diamonds. (arXiv:1902.06709v3 [hep-th] UPDATED)

In AdS/CFT, the non-uniqueness of the reconstructed bulk from boundary subregions has motivated the notion of code subspaces. We present some closely related structures that arise in flat space. A useful organizing idea is that of an {\em asymptotic} causal diamond (ACD): a causal diamond attached to the conformal boundary of Minkowski space. The space of ACDs is defined by pairs of points, one each on the future and past null boundaries, ${\cal I}^{\pm}$. We observe that for flat space with an IR cut-off, this space (a) encodes a preferred class of boundary “subregions”, (b) is a plausible way to capture holographic data for local bulk reconstruction, (c) has a natural interpretation as the kinematic space for holography, (d) leads to a holographic entanglement entropy in flat space that matches previous definitions and satisfies strong sub-additivity, and, (e) has a bulk union/intersection structure isomorphic to the one that motivated the introduction of quantum error correction in AdS/CFT. By sliding the cut-off, we also note one substantive way in which flat space holography differs from that in AdS. Even though our discussion is centered around flat space (and AdS), we note that there are notions of ACDs in other spacetimes as well. They could provide a covariant way to abstractly characterize tensor sub-factors of Hilbert spaces of holographic theories.

Emergent quantum mechanics of the event-universe, quantization of events via Denrographic Hologram Theory. (arXiv:2208.01931v2 [quant-ph] UPDATED)

Quantum mechanics (QM) is derived based on a universe composed solely of events, for example, outcomes of observables. Such an event universe is represented by a dendrogram (a finite tree) and in the limit of infinitely many events by the p-adic tree. The trees are endowed with an ultrametric expressing hierarchical relationships between events. All events are coupled through the tree structure. Such a holistic picture of event-processes was formalized within the Dendrographic Hologram Theory (DHT). The present paper is devoted to the emergence of QM from DHT. We used the generalization of the QM-emergence scheme developed by Smolin. Following this scheme, we did not quantize events but rather the differences between them and through analytic derivation arrived at Bohmian mechanics. Previously, we were able to embed the basic elements of general relativity (GR) into DHT, and now after Smolin-like quantization of DHT, we can take a step toward quantization of GR. Finally, we remark that DHT is nonlocal in the treelike geometry, but this nonlocality refers to relational nonlocality in the space of events and not Einstein’s spatial nonlocality.

Is there evidence for exponential quantum advantage in quantum chemistry?. (arXiv:2208.02199v1 [physics.chem-ph] CROSS LISTED)

The idea to use quantum mechanical devices to simulate other quantum systems is commonly ascribed to Feynman. Since the original suggestion, concrete proposals have appeared for simulating molecular and materials chemistry through quantum computation, as a potential “killer application”. Indications of potential exponential quantum advantage in artificial tasks have increased interest in this application, thus, it is critical to understand the basis for potential exponential quantum advantage in quantum chemistry. Here we gather the evidence for this case in the most common task in quantum chemistry, namely, ground-state energy estimation. We conclude that evidence for such an advantage across chemical space has yet to be found. While quantum computers may still prove useful for quantum chemistry, it may be prudent to assume exponential speedups are not generically available for this problem.

Consciousness and quantum mechanics: a philosophical approach. (arXiv:2201.09663v5 [quant-ph] UPDATED)

Authors: Raoni Wohnrath Arroyo

This book deals with some ontological implications of standard non-relativistic quantum mechanics, and the use of the notion of `consciousness’ to solve the measurement problem.

Advanced General Relativity Notes. (arXiv:2208.02506v1 [gr-qc])

Authors: M. Le Delliou

These lecture notes are intended as a guide to Graduate level readers that are already familiar with basic General Relativity. They present in a concise way some advanced concepts and problems encountered in the study of gravitation. In these notes are covered: Alternates forms of the Schwarzschild Black Hole solution, including the classic Kruskal extension; An account of the building of Conformal, Carter-Penrose, diagrams; A discussion of Birkhoff Theorem; A discussion of tools for Geodesics and congruences, including Energy Conditions; A discussion of Horizons and an approach to some of the singularity theorems; An exploration of the Kerr Black Hole solution properties, including the Penrose Process and Black Hole Thermodynamics; A discussion of the Eckart and Israel-Stewart Relativistic Thermodynamics; A discussion of Tetrads in Relativity, in Einstein-Cartan theory and in Newman-Penrose formalism; An explicitation of calculations on Geodesics approach from Hamilton-Jacobi Formalism; A derivation from Least action of the equation of Motion of a top in Relativity, the M.P.D. equations

UV And IR Effects On Hawking Radiation. (arXiv:2207.07122v2 [hep-th] UPDATED)

Authors: Pei-Ming HoHikaru Kawai

We study the time-dependence of Hawking radiation for a black hole in the Unruh vacuum, and find that it is not robust against certain UV and IR effects. If there is a UV cutoff at the Planck scale, Hawking radiation is turned off after the scrambling time. In the absence of a UV cutoff, Hawking radiation is sensitive to the IR cutoff through a UV/IR connection due to higher-derivative interactions in the effective theory. Furthermore, higher-derivative interactions with the background contribute to a large amplitude of particle creation that changes Hawking radiation. This unexpected large effect is related to a peculiar feature of the Hawking particle wave packets.

From maximum force to physics in 9 lines — and implications for quantum gravity. (arXiv:2208.01038v2 [gr-qc] UPDATED)

Authors: Christoph Schiller

A compact summary of present fundamental physics is given and evaluated. Its 9 lines contain both general relativity and the standard model of particle physics. Their precise agreement with experiments, in combination with their extreme simplicity and their internal consistency, suggest that there are no experimental effects beyond the two theories. The combined properties of the 9 lines also imply concrete suggestions for the search for a theory of quantum gravity. Finally, the 9 lines specify the only decisive tests that allow checking any specific proposal for such a theory.

Why It Matters that Idealizations Are False

Potochnik, Angela (2020) Why It Matters that Idealizations Are False. [Preprint]

High-Dimensional Bell Test without Detection Loophole

Author(s): Xiao-Min Hu, Chao Zhang, Bi-Heng Liu, Yu Guo, Wen-Bo Xing, Cen-Xiao Huang, Yun-Feng Huang, Chuan-Feng Li, and Guang-Can Guo

Violation of Bell’s inequalities shows strong conflict between quantum mechanics and local realism. Loophole-free Bell tests not only deepen understanding of quantum mechanics, but are also important foundations for device-independent (DI) tasks in quantum information. High-dimensional quantum syste…

[Phys. Rev. Lett. 129, 060402] Published Wed Aug 03, 2022

Understanding Time Reversal in Quantum Mechanics: A Full Derivation

Gao, Shan (2022) Understanding Time Reversal in Quantum Mechanics: A Full Derivation. [Preprint]

On the unreasonable reliability of mathematical inference

Abstract

In (Avigad, 2020), Jeremy Avigad makes a novel and insightful argument, which he presents as part of a defence of the ‘Standard View’ about the relationship between informal mathematical proofs (that is, the proofs that mathematicians write for each other and publish in mathematics journals, which may in spite of their ‘informal’ label be rather more formal than other kinds of scientific communication) and their corresponding formal derivations (‘formal’ in the sense of computer science and mathematical logic). His argument considers the various strategies by means of which mathematicians can write informal proofs that meet mathematical standards of rigour, in spite of the prodigious length, complexity and conceptual difficulty that some proofs exhibit. He takes it that showing that and how such strategies work is a necessary part of any defence of the Standard View.

In this paper, I argue for two claims. The first is that Avigad’s list of strategies is no threat to critics of the Standard View. On the contrary, this observational core of heuristic advice in Avigad’s paper is agnostic between rival accounts of mathematical correctness. The second is that that Avigad’s project of accounting for the relation between formal and informal proofs requires an answer to a prior question: what sort of thing is an informal proof? His paper havers between two answers. One is that informal proofs are ultimately syntactic items that differ from formal derivations only in completeness and use of abbreviations. The other is that informal proofs are not purely syntactic items, and therefore the translation of an informal proof into a derivation is not a routine procedure but rather a creative act. Since the ‘syntactic’ reading of informal proofs reduces the Standard View to triviality, makes a mystery of the valuable observational core of his paper, and underestimates the value of the achievements of mathematical logic, he should choose some version of the second option.

Experimental Demonstration of Genuine Tripartite Nonlocality under Strict Locality Conditions

Author(s): Liang Huang, Xue-Mei Gu, Yang-Fan Jiang, Dian Wu, Bing Bai, Ming-Cheng Chen, Qi-Chao Sun, Jun Zhang, Sixia Yu, Qiang Zhang, Chao-Yang Lu, and Jian-Wei Pan

Nonlocality captures one of the counterintuitive features of nature that defies classical intuition. Recent investigations reveal that our physical world’s nonlocality is at least tripartite; i.e., genuinely tripartite nonlocal correlations in nature cannot be reproduced by any causal theory involvi…

[Phys. Rev. Lett. 129, 060401] Published Tue Aug 02, 2022

Is There Causation in Fundamental Physics? New Insights from Process Matrices and Quantum Causal Modelling

Adlam, Emily (2022) Is There Causation in Fundamental Physics? New Insights from Process Matrices and Quantum Causal Modelling. [Preprint]

Rethinking conspiracy theories

Abstract

I argue that that an influential strategy for understanding conspiracy theories stands in need of radical revision. According to this approach, called ‘generalism’, conspiracy theories are epistemically defective by their very nature. Generalists are typically opposed by particularists, who argue that conspiracy theories should be judged case-by-case, rather than definitionally indicted. Here I take a novel approach to criticizing generalism. I introduce a distinction between ‘Dominant Institution Conspiracy Theories and Theorists’ and ‘Non-Dominant Institution Conspiracy Theories and Theorists’. Generalists uncritically center the latter in their analysis, but I show why the former must be centered by generalists’ own lights: they are the clearest representatives of their views, and they are by far the most harmful. Once we make this change in paradigm cases, however, various typical generalist theses turn out to be false or in need of radical revision. Conspiracy theories are not primarily produced by extremist ideologies, as generalists typically claim, since mainstream, purportedly non-extremist political ideologies turn out to be just as, if not more responsible for such theories. Conspiracy theories are also, we find, not the province of amateurs: they are often created and pushed by individuals widely viewed as experts, who have the backing of our most prestigious intellectual institutions. While generalists may be able to take this novel distinction and shift in paradigm cases on board, this remains to be seen. Subsequent generalist accounts that do absorb this distinction and shift will look radically different from previous incarnations of the view.

Physicalism without the idols of mathematics

Szabo, Laszlo E. (2021) Physicalism without the idols of mathematics. [Preprint]

An Armstrongian Defense of Dispositional Monist Accounts of Laws of Nature

Mohammadian, Mousa (2022) An Armstrongian Defense of Dispositional Monist Accounts of Laws of Nature. [Preprint]