Quantum logical entropy: fundamentals and general properties. (arXiv:2108.02726v1 [quant-ph])

上午10:04 | | | Boaz Tamir, Ismael L. Paiva, Zohar Schwartzman-Nowik, Eliahu Cohen | | | quant-ph updates on arXiv.org |

Logical entropy gives a measure, in the sense of measure theory, of the distinctions of a given partition of a set, an idea that can be naturally generalized to classical probability distributions. Here, we analyze how fundamental concepts of this entropy and other related definitions can be applied to the study of quantum systems, leading to the introduction of the quantum logical entropy. Moreover, we prove several properties of this entropy for generic density matrices that may be relevant to various areas of quantum mechanics and quantum information. Furthermore, we extend the notion of quantum logical entropy to post-selected systems.

The Quantum Theory of Time: a Calculus for Q-numbers. (arXiv:2108.02771v1 [quant-ph])

上午10:04 | | | Samuel Kuypers | | | quant-ph updates on arXiv.org |

In quantum theory, physical systems are usually assumed to evolve relative to a c-number time. This c-number time is unphysical and has turned out to be unnecessary for explaining dynamics: in the timeless approach to quantum theory developed by Page & Wootters (1983), subsystems of a stationary universe can instead evolve relative to a ‘clock’, which is a quantum system with a q-number time observable. Page & Wootters formulated their construction in the Schr\”odinger picture and left open the possibility that the c-number time still plays an explanatory role in the Heisenberg picture. I formulate their construction in the Heisenberg picture and demonstrate that the c-number time is completely unnecessary in that picture, too. When the Page-Wootters construction is formulated in the Heisenberg picture, the descriptors of physical systems are functions of the clock’s q-number time, and derivatives with respect to this q-number time can be defined in terms of the clock’s algebra of observables, resulting in a calculus for q-numbers.

上午10:04 | | | Jose Bernabeu, Antonio Di Domenico | | | quant-ph updates on arXiv.org |

Entangled neutral K-mesons allow the study of their correlated dynamics at interference and decoherence times not accessible in any other system. We find novel quantum phenomena associated to a correlation-in-time between the two partners: the past state of the first decayed Kaon, when it was entangled before its decay, is influenced by the result and the time of the future observation of the second decay channel. This surprising “from future to past” effect is fully observable and leads to the unique experimental tag of the KS-state, an unsolved problem since the discovery of CP violation.

Scientific Objectivity and its Limits. (arXiv:2010.01013v2 [quant-ph] UPDATED)

上午10:04 | | | Richard Healey | | | quant-ph updates on arXiv.org |

Measurement outcomes provide data for a physical theory. Unless they are objective they support no objective scientific knowledge. So the outcome of a quantum measurement must be an objective physical fact. But recent arguments purport to show that if quantum theory is universally applicable then there is no such fact. This calls for a reappraisal of the notions of fact and objectivity. If quantum theory is universally applicable the facts about the physical world include a fact about each quantum measurement outcome. These physical facts lack an ideal kind of objectivity but their more modest objectivity is all that science needs.

Trapped electrons and ions as particle detectors. (arXiv:2104.05737v2 [quant-ph] UPDATED)

上午10:04 | | | Daniel Carney, Hartmut Häffner, David C. Moore, Jacob M. Taylor | | | quant-ph updates on arXiv.org |

Electrons and ions trapped with electromagnetic fields have long served as important high-precision metrological instruments, and more recently have also been proposed as a platform for quantum information processing. Here we point out that these systems can also be used as highly sensitive detectors of passing charged particles, due to the combination of their extreme charge-to-mass ratio and low-noise quantum readout and control. In particular, these systems can be used to detect energy depositions many orders of magnitude below typical ionization scales. As illustrations, we suggest some applications in particle physics. We outline a non-destructive time-of-flight measurement capable of sub-eV energy resolution for slowly moving, collimated particles. We also show that current devices can be used to provide competitive sensitivity to models where ambient dark matter particles carry small electric millicharges $\ll e$. Our calculations may also be useful in the characterization of noise in quantum computers coming from backgrounds of charged particles.

On Quanta of Information and Electromagnetic Fields. (arXiv:2107.02786v2 [quant-ph] UPDATED)

上午10:04 | | | Masroor H. S. Bukhari | | | quant-ph updates on arXiv.org |

We attempt to establish an equivalence of information and physical action, with the quanta (or packets of words) of information as possible sources of quantum fields (with a possible role in governing the interactions among those), similar to the quantum fields being the source of information. A physical model is formulated and reported here introducing the form and structure of these quanta of information, and their possible interactions with quantum fields. Information and quantum fields seem to be entangled with each other, and their underlying basis seems to have both a well-defined thermodynamic and probabilistic structure. The description of equivalent energy of a quantum of the electromagnetic field in terms of its information content, as well as an expression of signal power are provided. Various aspects of this problem and its possible implications and repercussions on our understanding of elementary quantum fields and their origin are discussed.

How a fake Kepler portrait became iconic. (arXiv:2108.02213v1 [physics.hist-ph])

上午10:04 | | | physics.hist-ph updates on arXiv.org |

Authors: Steven N. Shore, Václav Pavlík

For several decades a portrait of Johannes Kepler has been widely circulating among professional astronomers, scientific and academic institutions, and the general public. Despite its provenance and identification having been questioned in the early part of the last century, this painting has reached iconic status. We review its history from its first mention in the literature in the 1870s to a published but virtually unknown judgment of competent art experts of the 1920s that the work is in fact an early nineteenth century forgery. We display the painting in context with other more secure portraits and suggest that if it is based on anything, the painting may derive from the well known portrait from life of Michael M\”astlin. This correction takes on certain urgency since 2021 is the 450th anniversary of Kepler’s birth.

上午10:04 | | | physics.hist-ph updates on arXiv.org |

Authors: Artur Szczepanski

Classical objects have been excluded as subjects of the observed quantum properties, and the related problem of quantum objects nature has been suspended since the early days of Quantum Theory. Recent experiments show that the problem could be reasonably revisited. The outlined model indicates new issues, which could result from following and exploring the canonical idea of Dirac. Topological defects in solids are considered as an example. The aim is helping to grasp the underlying pre-theoretical new intuitions, which should replace the old ones attached to the background of classical physics.

Complexity and the Big Bang. (arXiv:2104.09626v3 [gr-qc] UPDATED)

上午10:04 | | | gr-qc updates on arXiv.org |

Authors: Hermann Nicolai

After a brief review of current scenarios for the resolution and/or avoidance of the Big Bang, an alternative hypothesis is put forward implying an infinite increase in complexity towards the initial singularity. This may result in an effective non-calculability which would present an obstruction to actually reaching the beginning of time. This proposal is motivated by the appearance of certain infinite-dimensional duality symmetries of indefinite Kac–Moody type in attempts to unify gravity with the fundamental matter interactions, and deeply rooted in properties of Einstein’s theory.

上午10:04 | | | gr-qc updates on arXiv.org |

Authors: Debaprasad Maity, Sourav Pal

Universe is believed to be born out of a quantum state. However, defining any observables associated the quantum properties and their possible observational possibilities in the present universe has gained significant interest recently. In this submission we propose quantum Poincare sphere measurement as an observable quantity which can give us hint of quantumness of the origin of primordial gravitational waves and large scale magnetic field. The Poincare sphere is defined in terms of power spectrum and quantum stokes operators associated with the polarization of those fields, which can be directly measured. To support our results we further explored the possible Bell violation test for a set of generalized pseudo spin operators defined in the polarization space of those fields.

Spacetime is material. (arXiv:2108.01712v1 [physics.hist-ph] CROSS LISTED)

上午10:04 | | | gr-qc updates on arXiv.org |

Authors: Luciano Combi

Space and time are central concepts for understanding our World. They are important ingredients at the core of every scientific theory and subject of intense debate in philosophy. Albert Einstein’s Special and General theories of Relativity showed that space and time blend in a single entity called spacetime. Even after a century of its conception, many questions about the nature of spacetime remain controversial. In this chapter, we analyze the ontological status of spacetime from a realistic and materialistic point of view. We start by outlining the well-known controversy between substantivalism and relationalism and the evolution of the debate with the appearance of General Relativity. We analyze how to interpret spacetime as a physical system and how to model its properties in a background-free theory where spacetime itself is dynamical. We discuss the concept of change, energy, and the ontology of spacetime events. In the last section, we review the mereology of spacetime and its relevance in cosmology.

2021年8月4日 星期三 上午8:00 | | | Latest Results for Synthese |

**Abstract**

In this paper I present a new perspective for interpreting the wavefunction as a non-material, non-epistemic, non-representational entity. I endorse a functional view according to which the wavefunction is defined by its roles in the theory. I argue that this approach shares some similarities with the nomological account of the wave function as well as with the pragmatist and epistemic approaches to quantum theory, while avoiding the major objections of these alternatives.

2021年8月2日 星期一 上午8:00 | | | Anders Malthe-Sørenssen | | | Nature Physics – Issue – nature.com science feeds |

Nature Physics, Published online: 02 August 2021; doi:10.1038/s41567-021-01312-1

Frictional sliding starts with a crack front propagating across an interface — a process that is well described by fracture mechanics. Experiments now show that the onset of crack formation is governed by physics that is yet to be fully understood.

Nucleation fronts ignite the interface rupture that initiates frictional motion

2021年8月2日 星期一 上午8:00 | | | Jay Fineberg | | | Nature Physics – Issue – nature.com science feeds |

Nature Physics, Published online: 02 August 2021; doi:10.1038/s41567-021-01299-9

Frictional motion between two surfaces in contact starts with the formation of nucleating rupture fronts. It is now shown that these emerge from nucleation fronts, which develop from a certain stress level onwards and with a characteristic velocity.

Intrinsic local distances: a mixed solution to Weyl’s tile argument

2021年8月1日 星期日 上午8:00 | | | Latest Results for Synthese |

**Abstract**

Weyl’s tile argument purports to show that there are no natural distance functions in atomistic space that approximate Euclidean geometry. I advance a response to this argument that relies on a new account of distance in atomistic space, called *the mixed account*, according to which *local distances* are primitive and other distances are derived from them. Under this account, atomistic space can approximate Euclidean space (and continuous space in general) very well. To motivate this account as a genuine solution to Weyl’s tile argument, I argue that this account is no less natural than the standard account of distance in continuous space. I also argue that the mixed account has distinctive advantages over Forrest’s (Synthese 103:327–354, 1995) account in response to Weyl’s tile argument, which can be considered as a restricted version of the mixed account.

Reliability of mathematical inference

2021年8月1日 星期日 上午8:00 | | | Latest Results for Synthese |

**Abstract**

Of all the demands that mathematics imposes on its practitioners, one of the most fundamental is that proofs ought to be correct. It has been common since the turn of the twentieth century to take correctness to be underwritten by the existence of formal derivations in a suitable axiomatic foundation, but then it is hard to see how this normative standard can be met, given the differences between informal proofs and formal derivations, and given the inherent fragility and complexity of the latter. This essay describes some of the ways that mathematical practice makes it possible to reliably and robustly meet the formal standard, preserving the standard normative account while doing justice to epistemically important features of informal mathematical justification.

2021年8月1日 星期日 上午8:00 | | | Latest Results for Synthese |

**Abstract**

The proposal that probabilistic inference and unconscious hypothesis testing are central to information processing in the brain has been steadily gaining ground in cognitive neuroscience and associated fields. One popular version of this proposal is the new theoretical framework of predictive processing or prediction error minimization (PEM), which couples unconscious hypothesis testing with the idea of ‘active inference’ and claims to offer a unified account of perception and action. Here we will consider one outstanding issue that still looms large at the core of the PEM framework: the lack of a clear criterion for distinguishing conscious states from unconscious ones. In order to fulfill the promise of becoming a unifying framework for describing and modeling cognition, PEM needs to be able to differentiate between conscious and unconscious mental states or processes. We will argue that one currently popular view, that the contents of conscious experience are determined by the ‘winning hypothesis’ (i.e. the one with the highest posterior probability, which determines the behavior of the system), falls short of fully accounting for conscious experience. It ignores the possibility that some states of a system can control that system’s behavior even though they are apparently not conscious (as evidenced by e.g. blindsight or subliminal priming). What follows from this is that the ‘winning hypothesis’ view does not provide a complete account of the difference between conscious and unconscious states in the probabilistic brain. We show how this problem (and some other related problems) for the received view can be resolved by augmenting PEM with Daniel Dennett’s multiple drafts model of consciousness. This move is warranted by the similar roles that attention and internal competition play in both the PEM framework and the multiple drafts model.

Macroscopic limit of quantum systems. (arXiv:2107.13594v1 [quant-ph])

2021年7月31日 星期六 上午9:55 | | | Janos Polonyi | | | quant-ph updates on arXiv.org |

The classical physics is approached from quantum mechanics in the macroscopic limit. The technical device to achieve this goal is the quantum version of the central limit theorem, derived for an observable at a given time and for the time-dependent expectation value of the coordinate. The emergence of the classical trajectory can be followed and the deterministic classical laws can be recovered in all practical purposes owing to the largeness of Avogadro’s number. The emergence of a classical trajectory is followed qualitatively in Wilson’s cloud chamber.

Locality and entanglement of indistinguishable particles. (arXiv:2107.13911v1 [quant-ph])

2021年7月31日 星期六 上午9:55 | | | Till Jonas Frederick Johann, Ugo Marzolino | | | quant-ph updates on arXiv.org |

Entanglement is one of the strongest quantum correlation, and is a key ingredient in fundamental aspects of quantum mechanics and a resource for quantum technologies. While entanglement theory is well settled for distinguishable particles, there are five inequivalent approaches to entanglement of indistinguishable particles. We analyse the different definitions of indistinguishable particle entanglement in the light of the locality notion. This notion is specified by two steps: i) the identification of subsystems by means of their local operators; ii) the requirement that entanglement represent correlations between the above subsets of operators. We prove that three of the aforementioned five entanglement definitions are incompatible with any locality notion defined as above.

Causal reappraisal of the quantum three box paradox. (arXiv:2107.13937v1 [quant-ph])

2021年7月31日 星期六 上午9:55 | | | Pawel Blasiak, Ewa Borsuk | | | quant-ph updates on arXiv.org |

Quantum three box paradox is a prototypical example of some bizarre predictions for intermediate measurements made on pre- and post-selected systems. Although in principle those effects can be explained by measurement disturbance, it is not clear what mechanisms are required to fully account for the observed correlations. In this paper, this paradox is scrutinised from the causal point of view. We consider an array of potential causal structures behind the experiment, eliminating those without enough explanatory power. This gives a means of differentiating between the various mechanisms in which measurement disturbance can propagate in the system. Specifically, we distinguish whether it is just the measurement outcome or the full measurement context that is required for the causal explanation of the observed statistics. We show that the latter is indispensable, but only when the full statistics is taken into account (which includes checking the third box too). Furthermore, we discuss the realism assumption which posits the existence of preexisting values revealed by measurements. It is shown that in this case measurement disturbance is necessary. Interestingly, without the realism assumption, the original version of the paradox (with just two boxes considered for inspection) can be explained without resorting to any measurement disturbance. These various results illustrate the richness of the paradox which is better appreciated from the causal perspective.

2021年7月31日 星期六 上午9:55 | | | Rhea Alexander, Si Gvirtz-Chen, David Jennings | | | quant-ph updates on arXiv.org |

Symmetry principles are fundamental in physics, and while they are well understood within Lagrangian mechanics, their impact on quantum channels has a range of open questions. The theory of asymmetry grew out of information-theoretic work on entanglement and quantum reference frames, and allows us to quantify the degree to which a quantum system encodes coordinates of a symmetry group. Recently a complete set of entropic conditions was found for asymmetry in terms of correlations relative to infinitely many quantum reference frames. However these conditions are difficult to use in practice and the physical implications unclear. Here we show that this set of conditions has extensive redundancy, and one can restrict to reference frames forming any closed surface in the state space that has the maximally mixed state in its interior. This in turn implies that asymmetry can be reduced to just a single entropic condition evaluated at the maximally mixed state. Contrary to intuition, this shows that we do not need macroscopic, classical reference frames to determine the asymmetry properties of a quantum system, but instead infinitesimally small frames suffice. Building on this analysis, we provide simple, closed conditions to estimate the minimal depolarization needed so as to make a given quantum state accessible under $G$-covariant quantum channels.

Ontology in quantum mechanics. (arXiv:2107.14191v1 [quant-ph])

2021年7月31日 星期六 上午9:55 | | | Gerard t Hooft | | | quant-ph updates on arXiv.org |

It is suspected that the quantum evolution equations describing the micro-world as we know it are of a special kind that allows transformations to a special set of basis states in Hilbert space, such that, in this basis, the evolution is given by elements of the permutation group. This would restore an ontological interpretation. It is shown how, at low energies per particle degree of freedom, almost any quantum system allows for such a transformation. This contradicts Bell’s theorem, and we emphasise why some of the assumptions made by Bell to prove his theorem cannot hold for the models studied here. We speculate how an approach of this kind may become helpful in isolating the most likely version of the Standard Model, combined with General Relativity. A link is suggested with black hole physics.

2021年7月31日 星期六 上午9:55 | | | Andrea Di Biagio, Pietro Donà, Carlo Rovelli | | | quant-ph updates on arXiv.org |

The operational formulations of quantum theory are drastically time oriented. However, to the best of our knowledge, microscopic physics is time-symmetric. We address this tension by showing that the asymmetry of the operational formulations does not reflect a fundamental time-orientation of physics. Instead, it stems from built-in assumptions about the $users$ of the theory. In particular, these formalisms are designed for predicting the future based on information about the past, and the main mathematical objects contain implicit assumption about the past, but not about the future. The main asymmetry in quantum theory is the difference between knowns and unknowns.