Weekly Papers on Quantum Foundations (39)

Towards the Heisenberg limit in microwave photon detection by a qubit array. (arXiv:2009.11271v2 [quant-ph] UPDATED)

上午9:49|P. Navez, A. G. Balanov, S. E. Savel’ev, A. M. Zagoskin|quant-ph updates on arXiv.org

Using an analytically solvable model, we show that a qubit array-based detector allows to achieve the fundamental Heisenberg limit in detecting single photons. In case of superconducting qubits, this opens new opportunities for quantum sensing and communications in the important microwave range.

Post-Newtonian Description of Quantum Systems in Gravitational Fields. (arXiv:2009.11319v1 [gr-qc])

上午9:49|physics.hist-ph updates on arXiv.org

Authors: Philip K. Schwartz

This thesis deals with the systematic treatment of quantum-mechanical systems in post-Newtonian gravitational fields. Starting from clearly spelled-out assumptions, employing a framework of geometric background structures defining the notion of a post-Newtonian expansion, our systematic approach allows to properly derive the post-Newtonian coupling of quantum-mechanical systems to gravity based on first principles. This sets it apart from more heuristic approaches that are commonly employed, for example, in the description of quantum-optical experiments under gravity.

Regarding single particles, we compare simple canonical quantisation of a free particle in curved spacetime to formal expansions of the minimally coupled Klein-Gordon equation, which may be motivated from QFT in curved spacetimes. Specifically, we develop a general WKB-like post-Newtonian expansion of the KG equation to arbitrary order in $c^{-1}$. Furthermore, for stationary spacetimes, we show that the Hamiltonians arising from expansions of the KG equation and from canonical quantisation agree up to linear order in particle momentum, independent of any expansion in $c^{-1}$.

Concerning composite systems, we perform a fully detailed systematic derivation of the first order post-Newtonian quantum Hamiltonian describing the dynamics of an electromagnetically bound two-particle system situated in external electromagnetic and gravitational fields, the latter being described by the Eddington-Robertson PPN metric.

In the last, independent part of the thesis, we prove two uniqueness results characterising the Newton–Wigner position observable for Poincar\’e-invariant classical Hamiltonian systems: one is a direct classical analogue of the quantum Newton–Wigner theorem, and the other clarifies the geometric interpretation of the Newton–Wigner position as `centre of spin’, as proposed by Fleming in 1965.

Comment on “Physics without determinism: Alternative interpretations of classical physics”, Phys. Rev. A, 100:062107, Dec 2019. (arXiv:2009.11709v1 [quant-ph])

上午9:49|physics.hist-ph updates on arXiv.org

Authors: Luca CallegaroFrancesca PennecchiWalter Bich

The paper “Physics without determinism: Alternative interpretations of classical physics” [Phys. Rev. A, 100:062107, Dec 2019] defines finite information quantities (FIQ). A FIQ expresses the available information about the value of a physical quantity. We show that a change in the measurement unit does not preserve the information carried by a FIQ, and therefore that the definition provided in the paper is not complete.

Time Travel Paradoxes and Multiple Histories. (arXiv:1911.11590v2 [gr-qc] UPDATED)

上午9:49|physics.hist-ph updates on arXiv.org

Authors: Jacob HauserBarak Shoshany

If time travel is possible, it seems to inevitably lead to paradoxes. These include consistency paradoxes, such as the famous grandfather paradox, and bootstrap paradoxes, where something is created out of nothing. One proposed class of resolutions to these paradoxes allows for multiple histories (or timelines), such that any changes to the past occur in a new history, independent of the one where the time traveler originated. We introduce a simple mathematical model for a spacetime with a time machine, and suggest two possible multiple-histories models, making use of branching spacetimes and covering spaces respectively. We use these models to construct novel and concrete examples of multiple-histories resolutions to time travel paradoxes, and we explore questions such as whether one can ever come back to a previously visited history and whether a finite or infinite number of histories is required. Interestingly, we find that the histories may be finite and cyclic under certain assumptions, in a way which extends the Novikov self-consistency conjecture to multiple histories and exhibits hybrid behavior combining the two. Investigating these cyclic histories, we rigorously determine how many histories are needed to fully resolve time travel paradoxes for particular laws of physics. Finally, we discuss how observers may experimentally distinguish between multiple histories and the Hawking and Novikov conjectures.

Kant and Hegel in Physics. (arXiv:2009.06198v2 [physics.hist-ph] UPDATED)

上午9:49|physics.hist-ph updates on arXiv.org

Authors: Y.S.Kim

Kant and Hegel are among the philosophers who are guiding the way in which we reason these days. It is thus of interest to see how physical theories have been developed along the line of Kant and Hegel. Einstein became interested in how things appear to moving observers. Quantum mechanics is also an observer-dependent science. The question then is whether quantum mechanics and relativity can be synthesized into one science. The present form of quantum field theory is a case in point. This theory however is based on the algorithm of the scattering matrix where all participating particles are free in the remote past and in the remote future. We thus need, in addition, a Lorentz-covariant theory of bound state which will address the question of how the hydrogen atom would look to moving observers. The question is then whether this Lorentz-covariant theory of bound states can be synthesized with the field theory into a Lorentz-covariant quantum mechanics. This article reviews the progress made along this line. This integrated Kant-Hegel process is illustrated in terms of the way in which Americans practice their democracy.

On Quantum Simulation Of Cosmic Inflation. (arXiv:2009.10921v2 [quant-ph] UPDATED)

上午9:49|gr-qc updates on arXiv.org

Authors: Yue-Zhou LiJunyu Liu

In this paper, we generalize Jordan-Lee-Preskill, an algorithm for simulating flat-space quantum field theories, to 3+1 dimensional inflationary spacetime. The generalized algorithm contains the encoding treatment, the initial state preparation, the inflation process, and the quantum measurement of cosmological observables at late time. The algorithm is helpful for obtaining predictions of cosmic non-Gaussianities, serving as useful benchmark problems for quantum devices, and checking assumptions made about interacting vacuum in the inflationary perturbation theory.

Components of our work also include a detailed discussion about the lattice regularization of the cosmic perturbation theory, a detailed discussion about the in-in formalism, a discussion about encoding using the HKLL-type formula that might apply for both dS and AdS spacetimes, a discussion about bounding curvature perturbations, a description of the three-party Trotter simulation algorithm for time-dependent Hamiltonians, a ground state projection algorithm for simulating gapless theories, a discussion about the quantum-extended Church-Turing Thesis, and a discussion about simulating cosmic reheating in quantum devices.

Definitions more geometrarum and Newton’s scholium on space and time

上午9:49|ScienceDirect Publication: Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern PhysicsScienceDirect RSShttps://www.sciencedirect.com/journal/studies-in-history-and-philosophy-of-science-part-b-studies-in-history-and-philosophy-of-modern-physicsRSS for NodeWed, 24 Jul 2019 09:46:42 GMTCopyright © 2019 Elsevier Ltd. All rights reservedImprints of the underlying structure of physical theoriesPublication date: Available online 12 July 2019Source: Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern PhysicsAuthor(s): Jorge ManeroAbstractIn the context of scientific realism, this paper intends to provide a formal and accurate description of the structural-based ontology posited by classical mechanics, quantum mechanics and special relativity, which is preserved across the empirical domains of these theories and explain their successful predictions. Along the lines of ontic structural realism, such a description is undertaken by

Publication date: Available online 24 September 2020

Source: Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics

Author(s): Zvi Biener

A sideways look at faithfulness for quantum correlations

上午1:04|Philsci-Archive: No conditions. Results ordered -Date Deposited.

Evans, Peter W. (2020) A sideways look at faithfulness for quantum correlations. [Preprint]

Trans-Planckian Philosophy of Cosmology

2020年9月25日 星期五 上午11:26|Philsci-Archive: No conditions. Results ordered -Date Deposited.

Schneider, Mike D. (2020) Trans-Planckian Philosophy of Cosmology. [Preprint]

Debunking prevailing explanations for the emergence of classicality in cosmology

2020年9月25日 星期五 上午11:25|Philsci-Archive: No conditions. Results ordered -Date Deposited.

Berjon, Javier and Okon, Elias and Sudarsky, Daniel (2020) Debunking prevailing explanations for the emergence of classicality in cosmology. [Preprint]

Conformal invariance of the Newtonian Weyl tensor

2020年9月22日 星期二 上午10:57|Philsci-Archive: No conditions. Results ordered -Date Deposited.

Dewar, Neil and Read, James (2020) Conformal invariance of the Newtonian Weyl tensor. [Preprint]

What Price Changing Laws of Nature?

2020年9月22日 星期二 上午10:56|Philsci-Archive: No conditions. Results ordered -Date Deposited.

Sartenaer, Olivier and Guay, Alexandre and Humphreys, Paul (2020) What Price Changing Laws of Nature? [Preprint]

Time–information uncertainty relations in thermodynamics

2020年9月21日 星期一 上午8:00|Jason R. Green|Nature Physics – Issue – nature.com science feeds

Nature Physics, Published online: 21 September 2020; doi:10.1038/s41567-020-0981-y

A time–information uncertainty relation in thermodynamics has been derived, analogous to the time–energy uncertainty relation in quantum mechanics, imposing limits on the speed of energy and entropy exchange between a system and external reservoirs.

Machine learning the thermodynamic arrow of time

2020年9月21日 星期一 上午8:00|Christopher Jarzynski|Nature Physics – Issue – nature.com science feeds

Nature Physics, Published online: 21 September 2020; doi:10.1038/s41567-020-1018-2

The phrase ‘arrow of time’ refers to the asymmetry in the flow of events. A machine learning algorithm trained to infer its direction identifies entropy production as the relevant underlying physical principle in the decision-making process.

Observation of energy-resolved many-body localization

2020年9月21日 星期一 上午8:00|H. Wang|Nature Physics – Issue – nature.com science feeds

Nature Physics, Published online: 21 September 2020; doi:10.1038/s41567-020-1035-1

Many-body localization—a phenomenon where an isolated system fails to reach thermal equilibrium—has been studied with a programmable quantum processor, which reveals the crucial role played by the initial energy on the onset of localization.

A different approach to logic: absolute logic

2020年9月20日 星期日 上午7:01|Philsci-Archive: No conditions. Results ordered -Date Deposited.

Avon, Mauro (2020) A different approach to logic: absolute logic. [Preprint]

The Past Hypothesis and the Nature of Physical Laws

2020年9月19日 星期六 下午11:11|Philsci-Archive: No conditions. Results ordered -Date Deposited.

Chen, Eddy Keming (2020) The Past Hypothesis and the Nature of Physical Laws. [Preprint]

Two Dogmas of Dynamicism

2020年9月19日 星期六 下午11:09|Philsci-Archive: No conditions. Results ordered -Date Deposited.

Weatherall, James Owen (2020) Two Dogmas of Dynamicism. [Preprint]

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