# Weekly Papers on Quantum Foundations (22)

Faking quantum probabilites: Beyond Bell’s theorem and Tsirelson bounds. (arXiv:2105.12728v1 [quant-ph])

Local hidden-variable model of singlet-state correlations discussed in M. Czachor, Arithmetic loophole in Bell’s Theorem: Overlooked threat to entangled-state quantum cryptography”, Acta Phys. Polon. A 139, 70-83 (2021), is shown to be a particular case of an infinite hierarchy of local hidden-variable models based on an infinite hierarchy of calculi. Violation of Bell-type inequalities is shown to be a `confusion of languages’ problem, a result of mixing different but neighboring levels of the hierarchy. Mixing of non-neighboring levels results in violations beyond the Tsirelson bounds.

Collapse-in and Collapse-out in Partial Measurement in Quantum Mechanics and its WISE Interpretation

Gui-Lu Long (Tsinghua University)

SCIENCE CHINA Physics, Mechanics & Astronomy, (2021)

In this short communication, we will concentrate on the partial measurement issue and give an explanation concerning the WISE interpretation. The essential idea of WISE is given in Ref. [4], together with the linear combination of unitaries (LCU) formalism of quantum computing. LCU has now become one of the major techniques in quantum algorithm design. The quantum circuit implementation of LCU is given in Refs. [7, 8], and a review of the subject is given in Ref.[9].

Protecting quantum states against loss. (arXiv:2105.13233v1 [quant-ph])

Quantum error correcting codes (QECCs) are the means of choice whenever quantum systems suffer errors, e.g., due to imperfect devices, environments, or faulty channels. By now, a plethora of families of codes is known, but there is no universal approach to finding new or optimal codes for a certain task and subject to specific experimental constraints. In particular, once found, a QECC is typically used in very diverse contexts, while its resilience against errors is captured in a single figure of merit, the distance of the code. This does not necessarily give rise to the most efficient protection possible given a certain known error or a particular application for which the code is employed.

In this paper, we investigate the loss channel, which plays a key role in quantum communication, and in particular in quantum key distribution over long distances. We develop a numerical set of tools that allows to optimize an encoding specifically for recovering lost particles without the need for backwards communication, where some knowledge about what was lost is available, and demonstrate its capabilities. This allows us to arrive at new codes ideal for the distribution of entangled states in this particular setting, and also to investigate if encoding in qudits or allowing for non-deterministic correction proves advantageous compared to known QECCs. While we here focus on the case of losses, our methodology is applicable whenever the errors in a system can be characterized by a known linear map.

Science Spoofs, Physics Pranks and Astronomical Antics. (arXiv:2103.17057v2 [physics.hist-ph] UPDATED)

Authors: Douglas Scott

Some scientists take themselves and their work very seriously. However, there are plenty of cases of humour being combined with science. Here I review some examples from the broad fields of physics and astronomy, particularly focusing on practical jokes and paper parodies. This is a mostly serious overview of a non-serious subject, but I’d like to claim that there is in fact some connection between humour and creativity in the physical sciences.

Gibbs Paradox in the View of Information Entropy. (arXiv:2105.12566v2 [cond-mat.stat-mech] UPDATED)

Authors: Xiao Xu

This paper introduces the basic concepts of information theory. Based on these concepts, we regard the states in the state space and the types of ideal gases as the symbols in a symbol set to calculate the mixing entropy of ideal gas involved in Gibbs Paradox. The discussion above reveals that the non-need for distinguishing can resolve the contradiction of Gibbs Paradox, implying the introduction of indistinguishability is not necessary. Further analysis shows that the information entropy of gas molecular types does not directly correlate to the energy of a gas system, so it should not be used for calculating thermodynamic and statistical dynamic entropies. Therefore, the mixing entropy of the ideal gas is independent of the molecular types and is much smaller than the value commonly thought.

Antimatter and the second law of thermodynamics. (arXiv:1704.01750v4 [hep-th] UPDATED)

Authors: Gabor Etesi

In this short paper we make a proposal that the second law of thermodynamics holds true for a closed physical system consisting of pure antimatter in the thermodynamical limit, but in a reversed form. We give two plausible arguments in favour to this proposal: one refers to the CPT theorem of relativistic quantum field theories while the other one is based on general thermodynamical arguments. However in our understanding the ultimate validity or invalidity of this idea can be decided only by future physical experiments.

As a consequence of the proposal we argue that the dynamical evolution of pure macroscopic antimatter systems can be very different from that of ordinary matter systems in the sense that sufficiently massive antimatter systems could have stronger tendency to form black holes during time evolution than their ordinary counterparts. Taking into account the various uniqueness theorems in black hole physics as well, as a result, antimatter could tracelessly disappear behind black hole event horizons faster in time than ordinary matter. The observed asymmetry of matter and antimatter could then be explained even if their presence in the Universe was symmetric in the beginning.

Black hole thermodynamics in the presence of a maximal length and minimum measurable in momentum. (arXiv:2104.08672v4 [gr-qc] UPDATED)

Authors: Bilel HamilBekir Can Lütfüoğlu

In this work, incorporating the effect of the minimum measurable in momentum and maximal length, we studied thermodynamics property of Schwarzschild black hole and the Unruh effect. {\color{red} According to this scenario, we see that the black hole temperature cannot be smaller than a certain minimum value of $T_{\min}$. Moreover, we find that black hole mass cannot be larger than a maximum mass value of $M_{\max }$. Considering these findings first we compute the corrected Hawking temperature versus the mass and examine its characteristic behavior. Then, we derive the black hole’s entropy and heat capacity. We find that the black hole is stable when $\frac{M_{\max }}{\sqrt{3}}<M<M_{\max }$. Finally, we examined the modified Unruh effect. We find that the modified Unruh temperature explicitly depends on $\alpha$.

Assessing Relational Quantum Mechanics

Muciño, Ricardo and Okon, Elias and Sudarsky, Daniel (2021) Assessing Relational Quantum Mechanics. [Preprint]

Shakin’ All Over: Proving Landauer’s principle without neglect of fluctuations

Myrvold, Wayne C. (2021) Shakin’ All Over: Proving Landauer’s principle without neglect of fluctuations. [Preprint]

I ain’t afraid of no ghost

Dougherty, John (2021) I ain’t afraid of no ghost. Studies in History and Philosophy of Science.

Quantum many-body scars and weak breaking of ergodicity

Nature Physics, Published online: 27 May 2021; doi:10.1038/s41567-021-01230-2

Most large quantum systems are ergodic, meaning that over time they forget their initial conditions and thermalize. This article reviews our understanding of seemingly ergodic systems that in fact have some long-lived, non-thermal states.

Open Quantum Systems’ Decay across Time

Author(s): Juliane Klatt, Chahan M. Kropf, and Stefan Y. Buhmann

The description of an open quantum system’s decay almost always requires several approximations so as to remain tractable. In this Letter, we first revisit the meaning, domain, and seeming contradictions of a few of the most widely used of such approximations: (semigroup) Markovianity, linear respon…

[Phys. Rev. Lett. 126, 210401] Published Wed May 26, 2021

Journeys in Mathematical Landscapes: Genius or Craft?

Lane, Lorenzo and Martin, Ursula and Murray-Rust, Dave and Pease, Alison and Tanswell, Fenner (2019) Journeys in Mathematical Landscapes: Genius or Craft? [Preprint]

Invariance or equivalence: a tale of two principles

Abstract

The presence of symmetries in physical theories implies a pernicious form of underdetermination. In order to avoid this theoretical vice, philosophers often espouse a principle called Leibniz Equivalence, which states that symmetry-related models represent the same state of affairs. Moreover, philosophers have claimed that the existence of non-trivial symmetries motivates us to accept the Invariance Principle, which states that quantities that vary under a theory’s symmetries aren’t physically real. Leibniz Equivalence and the Invariance Principle are often seen as part of the same package. I argue that this is a mistake: Leibniz Equivalence and the Invariance Principle are orthogonal to each other. This means that it is possible to hold that symmetry-related models represent the same state of affairs whilst having a realist attitude towards variant quantities. Various arguments have been presented in favour of the Invariance Principle: a rejection of the Invariance Principle is inter alia supposed to cause indeterminism, undetectability or failure of reference. I respond that these arguments at best support Leibniz Equivalence.

The Gauge Argument: A Noether Reason

Gomes, Henrique and Roberts, Bryan W. and Butterfield, Jeremy (2021) The Gauge Argument: A Noether Reason. [Preprint]

One World Is (Probably) Just as Good as Many

Steeger, Jeremy (2021) One World Is (Probably) Just as Good as Many. [Preprint]

Inside quantum black boxes

Nature Physics, Published online: 24 May 2021; doi:10.1038/s41567-021-01246-8

On the face of it, characterizing quantum dynamics in the exponentially large Hilbert space of a many-body system might require prohibitively many experiments. In fact, the locality of physical interactions means that it can be done efficiently.