Latest Papers on Quantum Foundations - Updated Daily by IJQF


Diverse measurements indicate that entropy grows as the universe evolves, we analyze from a quantum point of view plausible scenarios that allow such increase.

Authors: Pisin Chen, Dong-han Yeom

We investigate the entanglement entropy and the information flow of two-dimensional moving mirrors. Here we point out that various mirror trajectories can help to mimic different candidate resolutions to the information loss paradox following the semi-classical quantum field theory: (i) a suddenly stopping mirror corresponds to the assertion that all information is attached to the last burst, (ii) a slowly stopping mirror corresponds to the assertion that thermal Hawking radiation carries information, and (iii) a long propagating mirror corresponds to the remnant scenario. Based on such analogy, we find that the last burst of a black hole cannot contain enough information, while slowly emitting radiation can restore unitarity. For all cases, there is an apparent inconsistency between the picture based on quantum entanglements and that based on the semi-classical quantum field theory. Based on the quantum entanglement theory, a stopping mirror will generate a firewall-like violent emission which is in conflict with notions based on the semi-classical quantum field theory.

Authors: A. M. Aloisi, P. F. Nali

Around year 2000 the centenary of Planck's thermal radiation formula awakened interest in the origins of quantum theory, traditionally traced back to the Planck's conference on 14 December 1900 at the Berlin Academy of Sciences. A lot of more accurate historical reconstructions, conducted under the stimulus of that recurrence, placed the birth date of quantum theory in March 1905 when Einstein advanced his light quantum hypothesis. Both interpretations are yet controversial, but science historians agree on one point: the emergence of quantum theory from a presumed "crisis" of classical physics is a myth with scarce adherence to the historical truth. This article, written in Italian language, was originally presented in connection with the celebration of the World Year of Phyics 2005 with the aim of bringing these scholarly theses to a wider audience.


Tradizionalmente la nascita della teoria quantistica viene fatta risalire al 14 dicembre 1900, quando Planck present\`o all'Accademia delle Scienze di Berlino la dimostrazione della formula della radiazione termica. Numerose ricostruzioni storiche pi\`u accurate, effettuate nel periodo intorno al 2000 sotto lo stimolo dell'interesse per il centenario di quell'avvenimento, collocano invece la nascita della teoria quantistica nel marzo del 1905, quando Einstein avanz\`o l'ipotesi dei quanti di luce. Entrambe le interpretazioni sono tuttora controverse, ma gli storici della scienza concordano su un punto: l'emergere della teoria quantistica da una presunta "crisi" della fisica classica \`e un mito con scarsa aderenza alla verit\`a storica. Con questo articolo in italiano, presentato originariamente in occasione delle celebrazioni per il World Year of Phyics 2005, si \`e inteso portare a un pi\`u largo pubblico queste tesi gi\`a ben note agli specialisti.

Authors: John van de Wetering

There is a long history of representing a quantum state using a quasi-probability distribution: a distribution allowing negative values. In this paper we extend such representations to deal with quantum channels. The result is a convex, strongly monoidal, functorial embedding of the category of trace preserving completely positive maps into the category of quasi-stochastic matrices. This establishes quantum theory as a subcategory of quasi-stochastic processes. Such an embedding is induced by a choice of minimal informationally complete POVM's. We show that any two such embeddings are naturally isomorphic. The embedding preserves the dagger structure of the categories if and only if the POVM's are symmetric, giving a new use of SIC-POVM's. We also study general convex embeddings of quantum theory and prove a dichotomy that such an embedding is either trivial or faithful. The results of this paper allow a clear explanation of the characteristic features of quantum mechanics coming from being epistemically restricted (no-cloning, teleportation) and having negative probabilities (Bell inequalities, computational speed-up).

Authors: Zhong Chao Wu

Using the synchronous coordinates, the creation of a Schwarzschild black hole immersed in a de Sitter spacetime can be viewed as a coherent creation of a collection of timelike geodesics. The previously supposed conical singularities do not exist at the horizons of the constrained instan- ton. Instead, the unavoidable irregularity is presented as a non-vanishing second fundamental form elsewhere at the quantum transition 3-surface. The same arguments can be applied to charged, topological or higher dimensional black hole cases.

Authors: Andrew E Chubykalo, Augusto Espinoza, B P Kosyakov

The interplay between the action-reaction principle and the energy-momentum conservation law is revealed by the examples of the Maxwell-Lorentz and Yang-Mills-Wong theories, and general relativity. These two statements are shown to be equivalent in the sense that both hold or fail together. Their mutual agreement is demonstrated most clearly in the self-interaction problem by taking account of the rearrangement of degrees of freedom appearing in the action of the Maxwell-Lorentz and Yang-Mills-Wong theories. The failure of energy-momentum conservation in general relativity is attributed to the fact that this theory allows solutions having nontrivial topologies. The total energy and momentum of a system with nontrivial topological content is found to be ambiguous, coordintization-dependent quantities. For example, the energy of a Schwarzschild black hole may take any positive value greater than, or equal to, the mass of the body whose collapse is responsible for arising this black hole. We draw the analogy to the paradoxial Banach-Tarski theorem; the measure becomes a poorly defined concept if initial three-dimensional bounded sets are rearranged in topologically nontrivial ways through the action of free non-Abelian isometry groups.

Authors: C. Wetterich

Graviton fluctuations induce strong non-perturbative infrared renormalization effects for the cosmological constant. In flat space the functional renormalization flow drives a positive cosmological constant to zero. We propose a simple computation of the graviton contribution to the flow of the effective potential for scalar fields. Within variable gravity we find that the potential increases asymptotically at most quadratically with the scalar field. With effective Planck mass proportional to the scalar field, the solutions of the derived cosmological equations lead to an asymptotically vanishing cosmological "constant" in the infinite future, providing for dynamical dark energy in the present cosmological epoch. Beyond a solution of the cosmological constant problem, our simplified computation also entails a sizeable positive graviton-induced anomalous dimension for the quartic Higgs coupling in the ultraviolet regime, as required for the successful prediction of the Higgs boson mass within the asymptotic safety scenario for quantum gravity.

Authors: Tamás Geszti

A minimally nonlinear von Neumann equation for a Stern-Gerlach or Bell-type measuring apparatus, containing coordinate and momentum in a skew-symmetric, split scalar product structure over the configuration space, is shown to display pumping of weights between setup-defined basis states, with a single winner randomly selected in accordance with Born's rule, and the rest collapsing to zero, following Pearle's "gambler's ruin" scheme. Randomness emerges from deterministic irregular dynamics of the detectors, their microscopic states acting as a nonlocal set of hidden parameters, controlling individual outcomes. Statistical predictions defining quantum behavior are fully reproduced, which warrants that the scheme is non-signaling.

Authors: Pasquale Bosso, Saurya Das, Robert B. Mann

The Generalized Uncertainty Principle (GUP) is a modification of Heisenberg's Principle predicted by several theories of Quantum Gravity. It consists of a modified commutator between position and momentum. In this work we compute potentially observable effects that GUP implies for the harmonic oscillator, coherent and squeezed states in Quantum Mechanics. In particular, we rigorously analyze the GUP-perturbed harmonic oscillator Hamiltonian, defining new operators that act as ladder operators on the perturbed states. We use these operators to define the new coherent and squeezed states. We comment on potential applications.

Authors: Robert Street

The physical constructs underlying the properties of quantum mechanics are explored. Arguments are given that the particle wave function as well as photon and phonon quanta must derive from a more fundamental physical construct that has not yet been identified. An approach to identifying the construct is discussed and a specific construct is proposed and explained.

Authors: Roderich Tumulka

Bohmian mechanics, also known as pilot-wave theory or de Broglie-Bohm theory, is a formulation of quantum mechanics whose fundamental axioms are not about what observers will see if they perform an experiment but about what happens in reality. It is therefore called a "quantum theory without observers." It follows from these axioms that in a universe governed by Bohmian mechanics, observers will see outcomes with exactly the probabilities specified by the usual rules of quantum mechanics for empirical predictions. Specifically, Bohmian mechanics asserts that electrons and other elementary particles have a definite position at every time and move according to an equation of motion that is one of the fundamental laws of the theory and involves a wave function that evolves according to the usual Schr\"odinger equation. Bohmian mechanics is named after David Bohm (1917-1992), who was, although not the first to consider this theory, the first to realize (in 1952) that it actually makes correct predictions.

Authors: Giorgio Papini

In the study of covariant wave equations, linear gravity manifests itself through the metric deviation $\gamma_{\mu\nu}$ and a two-point vector potential $K_{\lambda}$ itself constructed from $\gamma_{\mu\nu}$ and its derivatives. The simultaneous presence of the two gravitational potentials is non contradictory. Particles also assume the character of quasiparticles and $K_{\lambda}$ carries information about the matter with which it interacts. We consider the influence of $K_{\lambda}$ on the dispersion relations of the particles involved, the particles' motion, quantum tunneling through a horizon, radiation, energy-momentum dissipation and flux quantization. % No {\it REVTEX} limit to number of lines.

Brown, Harvey R. (2017) Once and for all: the curious role of probability in the Past Hypothesis. [Preprint]
Redhead, Michael (2017) The Relativistic Einstein-Podolsky-Rosen Argument. [Preprint]
Crull, Elise (2017) Translation of: P. Ehrenfest (1925), 'Energieschwankungen im Strahlungsfeld oder Kristallgitter bei Superposition quantisierter Eigenschwingungen'. [Preprint]
de Swart, Jaco and Bertone, Gianfranco and van Dongen, Jeroen (2017) How dark matter came to matter. Nature Astronomy, 1 (0059). ISSN 2397-3366


Quantum trajectory-based descriptions of interference between two coherent stationary waves in a double-slit experiment are presented, as given by the de Broglie–Bohm (dBB) and modified de Broglie–Bohm (MdBB) formulations of quantum mechanics. In the dBB trajectory representation, interference between two spreading wave packets can be shown also as resulting from motion of particles. But a trajectory explanation for interference between stationary states is so far not available in this scheme. We show that both the dBB and MdBB trajectories are capable of producing the interference pattern for stationary as well as wave packet states. However, the dBB representation is found to provide the ‘which-way’ information that helps to identify the hole through which the particle emanates. On the other hand, the MdBB representation does not provide any which-way information while giving a satisfactory explanation of interference phenomenon in tune with the de Broglie’s wave particle duality. By counting the trajectories reaching the screen, we have numerically evaluated the intensity distribution of the fringes and found very good agreement with the standard results.

Pashby, Thomas (2017) At what time does a quantum experiment have a result? [Preprint]
Publication date: Available online 20 April 2017
Source:Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics
Author(s): Jeffrey A. Barrett
Hugh Everett III presented pure wave mechanics, sometimes referred to as the many-worlds interpretation, as a solution to the quantum measurement problem. While pure wave mechanics is an objectively deterministic physical theory with no probabilities, Everett sought to show how the theory might be understood as making the standard quantum statistical predictions as appearances to observers who were themselves described by the theory. We will consider his argument and how it depends on a particular notion of branch typicality. We will also consider responses to Everett and the relationship between typicality and probability. The suggestion will be that pure wave mechanics requires a number of significant auxiliary assumptions in order to make anything like the standard quantum predictions.

Authors: Yuri Bonder, Gabriel Leon

Modified gravity theories are supposed to incorporate low-energy quantum-gravity effects and, at the same time, they could shed light into the dark matter and dark energy problems. Here we study a particular modification of general relativity where local Lorentz invariance is spontaneously broken and whose physical effects, despite a decade-long effort, were unknown. We show that, during inflation, this modification produces anisotropies that would generate measurable effects on the Cosmic Microwave Background. Then, by using empirical constraints on the B-mode polarization spectrum, we can estimate that the `coefficient' components absolute value have to be smaller than $10^{-43}$. This is a remarkably strong limit, in fact, it is 29 orders of magnitude better than the best constraints on similar coefficients. Thus, we propose that inflation could stringently test other modified gravity theories.

Authors: Diederik Aerts, Massimiliano Sassoli de Bianchi

We show that the extended Bloch representation of quantum mechanics also applies to infinite-dimensional entities, to the extent that the number of (possibly infinitely degenerate) outcomes of a measurement remains finite, which is always the case in practical situations.

Authors: Jean Michel Sellier, K.G. Kapanova

Recently a new formulation of quantum mechanics has been suggested which is based on the concept of signed particles, that is, classical objects provided with a position, a momentum and a sign simultaneously. In this paper, we comment on the plausibility of simulating atomic systems beyond the Born-Oppenheimer approximation by means of the signed particle formulation of quantum mechanics. First, in order to show the new perspective offered by this new formalism, we provide an example studying quantum tunnelling through a simple Gaussian barrier in terms of the signed particle formulation. Then, we perform a direct simulation of the hydrogen atom as a full quantum two-body system, showing that the formalism can be a very promising tool for first-principle-only quantum chemistry.

Authors: Zong-Quan Zhou, Xiao Liu, Yaron Kedem, Jin-Min Cui, Zong-Feng Li, Yi-Lin Hua, Chuan-Feng Li, Guang-Can Guo

A century after its conception, quantum mechanics still hold surprises that contradict many "common sense" notions. The contradiction is especially sharp in case one consider trajectories of truly quantum objects such as single photons. From a classical point of view, trajectories are well defined for particles, but not for waves. The wave-particle duality forces a breakdown of this dichotomy and quantum mechanics resolves this in a remarkable way: Trajectories can be well defined, but they are utterly different from classical trajectories. Here, we give an operational definition to the trajectory of a single photon by introducing a novel technique to mark its path using its spectral composition. The method demonstrates that the frequency degree of freedom can be used as a bona fide quantum measurement device (meter). The analysis of a number of setups, using our operational definition, leads to anomalous trajectories which are non-continuous and in some cases do not even connect the source of the photon to where it is detected. We carried out an experimental demonstration of these anomalous trajectories using a nested interferometer. We show that the Two-state vector formalism provides a simple explanation for the results.

Arageorgis, Aristidis and Earman, John (2017) Bohmian Mechanics: A Panacea for What Ails Quantum Mechanics, or a Different and Problematic Theory? [Preprint]
Earman, John (2017) Quantum Bayesianism Assessed. [Preprint]
Christian, Joy (2017) Local Causality in a Friedmann-Robertson-Walker Spacetime. [Preprint]

Authors: Juan Maldacena, Douglas Stanford, Zhenbin Yang

We study various aspects of wormholes that are made traversable by an interaction beween the two asymptotic boundaries. We concentrate on the case of nearly-$AdS_2$ gravity and discuss a very simple mechanical picture for the gravitational dynamics. We derive a formula for the two sided correlators that includes the effect of gravitational backreaction, which limits the amount of information we can send through the wormhole. We emphasize that the process can be viewed as a teleportation protocol where the teleportee feels nothing special as he/she goes through the wormhole. We discuss some applications to the cloning paradox for old black holes. We point out that the same formula we derived for $AdS_2$ gravity is also valid for the simple SYK quantum mechanical theory, around the thermofield double state. We present a heuristic picture for this phenomenon in terms of an operator growth model. Finally, we show that a similar effect is present in a completely classical chaotic system with a large number of degrees of freedom.

Authors: Daniel J. Burger, Raúl Carballo-Rubio, Nathan Moynihan, Jeff Murugan, Amanda Weltman

The use of quantum field theory to understand astrophysical phenomena is not new. However, for the most part, the methods used are those that have been developed decades ago. The intervening years have seen some remarkable developments in computational quantum field theoretic tools. In particle physics, this technology has facilitated calculations that, even ten years ago would have seemed laughably difficult. It is remarkable, then, that most of these new techniques have remained firmly within the domain of high energy physics. We would like to change this. As alluded to in the title, this is the first in a series of papers aimed at showcasing the use of modern on-shell methods in the context of astrophysics and cosmology. In this first article, we use the old problem of the bending of light by a compact object as an anchor to pedagogically develop these new computational tools. Once developed, we then illustrate their power and utility with an application to the scattering of gravitational waves.

Authors: Louis Marchildon

Everett's interpretation of quantum mechanics was proposed to avoid problems inherent in the prevailing interpretational frame. It assumes that quantum mechanics can be applied to any system and that the state vector always evolves unitarily. It then claims that whenever an observable is measured, all possible results of the measurement exist. This assertion of multiplicity has been understood in many ways by proponents of Everett's theory. Here we shall illustrate how different views on multiplicity carry onto different views on spacetime.

Perception: Our useful inability to see reality

Nature 544, 7650 (2017). doi:10.1038/544296a

Author: Douwe Draaisma

There's some deviant thinking behind perception, discovers Douwe Draaisma.

Author(s): Miloslav Znojil, Iveta Semorádová, František Růžička, Hafida Moulla, and Ilhem Leghrib

During recent developments in quantum theory it has been clarified that observable quantities (such as energy and position) may be represented by operators Λ (with real spectra) that are manifestly non-Hermitian in a preselected friendly Hilbert space H(F). The consistency of these models is known t…

[Phys. Rev. A 95, 042122] Published Tue Apr 18, 2017

Authors: Andrei Khrennikov

We discuss the problems of quantum theory (QT) complicating its merging with general relativity (GR). QT is treated as a general theory of micro-phenomena - a bunch of models. Quantum mechanics (QM) and quantum field theory (QFT) are the most widely known (but, e.g., Bohmian mechanics is also a part of QT). The basic problems of QM and QFT are considered in interrelation. For QM, we stress its nonrelativistic character and the presence of spooky action at a distance. For QFT, we highlight the old problem of infinities. And this is the main point of the paper: it is meaningless to try to unify QFT so heavily suffering of infinities with GR. We also highlight difficulties of the QFT-treatment of entanglement. We compare the QFT and QM based measurement theories by presenting both theoretical and experimental viewpoints. Then we discuss two basic mathematical constraints of both QM and QFT, namely, the use of real (and, hence, complex) numbers and the Hilbert state space. We briefly present non-Archimedean and non-Hilbertian approaches to QT and their consequences. Finally, we claim that, in spite of the Bell theorem, it is still possible to treat quantum phenomena on the basis of a classical-like causal theory. We present a random field model generating the QM and QFT formalisms. This emergence viewpoint can serve as the basis for unification of novel QT (may be totally different from presently powerful QM and QFT) and general relativity GR. (It may happen that the latter would also be revolutionary modified.)

Authors: Gerd Christian Krizek

In May of 1935 Einstein published with two co-authors the famous EPR-paper about entangled particles, which questioned the completeness of Quantum Mechanics by means of a gedankenexperiment. Only one month later he published a work that seems unconnected to the EPR-paper at first, the so called Einstein-Rosen-paper that presented a solution of the field equations for particles in the framework of general relativity. Both papers ask for the conception of completeness in a theory and from a modern perspective it is easy to believe that there is a connection between these topics. We question whether Einstein might have considered that a correlation between nonlocal features of Quantum Mechanics and the Einstein-Rosen bridge can be used to explain entanglement. We analyse this question by discussing the used conceptions of "completeness", "atomistic structure of matter", and "quantum phenomena". We discuss the historical embedding of the two works and the context to modern research. Recent approaches are presented that formulate a EPR=ER principle and claim an equivalence of the basic principles of these two papers.

Author(s): Robin Harper, Robert J. Chapman, Christopher Ferrie, Christopher Granade, Richard Kueng, Daniel Naoumenko, Steven T. Flammia, and Alberto Peruzzo

We propose a framework for the systematic and quantitative generalization of Bell's theorem using causal networks. We first consider the multiobjective optimization problem of matching observed data while minimizing the causal effect of nonlocal variables and prove an inequality for the optimal regi…

[Phys. Rev. A 95, 042120] Published Mon Apr 17, 2017

Authors: Sanved Kolekar, Jorma Louko

Recently, Hawking, Perry and Strominger described a physical process that implants supertranslational hair on a Schwarzschild black hole by an infalling matter shock wave without spherical symmetry. Using the BMS-type symmetries of the Rindler horizon, we present an analogous process that implants supertranslational hair on a Rindler horizon by a matter shock wave without planar symmetry, and we investigate the corresponding memory effect on the Rindler family of uniformly linearly accelerated observers. We assume each observer to remain linearly uniformly accelerated through the wave, in the sense of the curved spacetime generalisation of the Letaw-Frenet equations. Starting with a family of observers who follow the orbits of a single boost Killing vector before the wave, we find that after the wave has passed, each observer still follows the orbit of a boost Killing vector but this boost differs from trajectory to trajectory, and the trajectory-dependence carries a memory of the planar inhomogeneity of the wave. We anticipate this classical memory phenomenon to have a counterpart in Rindler space quantum field theory.

Authors: A. Araujo, D. F. Lopez, J. G. Pereira

The replacement of the Poincar\'e-invariant Einstein special relativity by a de Sitter-invariant special relativity produces concomitant changes in all relativistic theories, including general relativity. A crucial change in the latter is that both the background de Sitter curvature and the gravitational dynamical curvature turns out to be included in a single curvature tensor. This means that the cosmological term no longer explicitly appears in Einstein equation, and is consequently not restricted to be constant. In this paper, the Newtonian limit of such theory is obtained, and the ensuing Newtonian Friedmann equations are show to provide a good account of the dark energy content of the present-day universe.

Authors: G. Rosi, G. D'Amico, L. Cacciapuoti, F. Sorrentino, M. Prevedelli, M. Zych, C. Brukner, G. M. Tino

The Einstein Equivalence Principle (EEP) has a central role in the understanding of gravity and space-time. In its weak form, or Weak Equivalence Principle (WEP), it directly implies equivalence between inertial and gravitational mass. Verifying this principle in a regime where the relevant properties of the test body must be described by quantum theory has profound implications. Here we report on a novel WEP test for atoms. A Bragg atom interferometer in a gravity gradiometer configuration compares the free fall of rubidium atoms prepared in two hyperfine states and in their coherent superposition. The use of the superposition state allows testing genuine quantum aspects of EEP with no classical analogue, which have remained completely unexplored so far. In addition, we measure the Eotvos ratio of atoms in two hyperfine levels with relative uncertainty in the low $10^{-9}$, improving previous results by almost two orders of magnitude.

Authors: Thomas J. Elliott, Mile Gu

Continuous-time stochastic processes pervade everyday experience, and the simulation of models of these processes is of great utility. Classical models of systems operating in continuous-time must typically track an unbounded amount of information about past behaviour, even for relatively simple models, enforcing limits on precision due to the finite memory of the machine. However, quantum machines can require less information about the past than even their optimal classical counterparts to simulate the future of discrete-time processes, and we demonstrate that this advantage extends to the continuous-time regime. Moreover, we show that this reduction in the memory requirement can be unboundedly large, allowing for arbitrary precision even with a finite quantum memory. We provide a systematic method for finding superior quantum constructions, and a protocol for analogue simulation of continuous-time renewal processes with a quantum machine.

Author(s): Adam Bednorz

Local realism in recent experiments is excluded on condition of freedom or randomness of choice combined with no signaling between observers by implementations of simple quantum models. Both no signaling and the underlying quantum model can be directly checked by analysis of experimental data. For p…

[Phys. Rev. A 95, 042118] Published Fri Apr 14, 2017

Publication date: Available online 14 April 2017
Source:Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics
Author(s): Barbara Drossel
It is widely believed that the underlying reality behind statistical mechanics is a deterministic and unitary time evolution of a many-particle wave function, even though this is in conflict with the irreversible, stochastic nature of statistical mechanics. The usual attempts to resolve this conflict for instance by appealing to decoherence or eigenstate thermalization are riddled with problems. This paper considers theoretical physics of thermalized systems as it is done in practice and shows that all approaches to thermalized systems presuppose in some form limits to linear superposition and deterministic time evolution. These considerations include, among others, the classical limit, extensivity, the concepts of entropy and equilibrium, and symmetry breaking in phase transitions and quantum measurement. As a conclusion, the paper suggests that the irreversibility and stochasticity of statistical mechanics should be taken as a real property of nature. It follows that a gas of a macroscopic number N of atoms in thermal equilibrium is best represented by a collection of N wave packets of a size of the order of the thermal de Broglie wave length, which behave quantum mechanically below this scale but classically sufficiently far beyond this scale. In particular, these wave packets must localize again after scattering events, which requires stochasticity and indicates a connection to the measurement process.

Authors: Egon Truebenbacher

The Dirac equation requires a treatment of the step potential that differs fundamentally from the traditional treatment, because the Dirac plane waves, besides momentum and spin, are characterized by a quantum number with the physical meaning of sign of charge. Since the Hermitean operator corresponding to this quantum number does not commute with the step potential, the time displacement parameter used in the ansatz of the stationary state does not have the physical meaning of energy. Therefore there are no paradoxal values of the energy. The new solution of the Dirac equation with a step potential is obtained. This solution, again, allows for phenomena of the Klein paradox type, but in addition it contains a positron amplitude localized at the threshold point of the step potential.

Authors: Jan Naudts

A simple transformation of field variables eliminates Coulomb forces from the theory of quantum electrodynamics. This suggests that Coulomb forces may be an emergent phenomenon rather than being fundamental. This possibility is investigated in the context of reducible quantum electrodynamics. It is shown that states exist which bind free photon and free electron fields. The binding energy peaks in the long-wavelength limit. This makes it plausible that Coulomb forces result from the interaction of the electron/positron field with long-wavelength transversely polarized photons.

Authors: Berthold-Georg Englert, Kelvin Horia, Jibo Dai, Yink Loong Len, Hui Khoon Ng

We analyze Vaidman's three-path interferometer with weak path marking [Phys. Rev. A 87, 052104 (2013)] and find that common sense yields correct statements about the particle's path through the interferometer. This disagrees with the original claim that the particles have discontinuous trajectories at odds with common sense. In our analysis, "the particle's path" has operational meaning as acquired by a path-discriminating measurement. For a quantum-mechanical experimental demonstration of the case, one should perform a single-photon version of the experiment by Danan et al. [Phys. Rev. Lett. 111, 240402 (2013)] with unambiguous path discrimination. We present a detailed proposal for such an experiment.

Authors: Björn Schrinski, Klaus Hornberger, Stefan Nimmrichter

We study how matter-wave interferometry with Bose-Einstein condensates is affected by hypothetical collapse models and by environmental decoherence processes. Motivated by recent atom fountain experiments with macroscopic arm separations, we focus on the observable signatures of first-order and higher-order coherence for different two-mode superposition states, and on their scaling with particle number. This can be used not only to assess the impact of environmental decoherence on many-body coherence, but also to quantify the extent to which macrorealistic collapse models are ruled out by such experiments. We find that interference fringes of phase-coherently split condensates are most strongly affected by decoherence, whereas the quantum signatures of independent interfering condensates are more immune against macrorealistic collapse. A many-body enhanced decoherence effect beyond the level of a single atom can be probed if higher-order correlations are resolved in the interferogram.

Authors: F. Darabi, K. Atazadeh

We study the Generalized Uncertainty Principle (GUP) in the framework of Einstein static universe (ESU). It is shown that the deformation parameter corresponding to the Snyder non-commutative space can induce an energy density subject to GUP which obeys the holographic principle (HP) and plays the role of a cosmological constant. Using the holographic feature of GUP energy density, we introduce new holographic based IR and UV cut-offs. Moreover, we propose a solution to the cosmological constant problem. This solution is based on the result that the Einstein equations just couple to the tiny holographic based surface energy density (cosmological constant) induced by the deformation parameter, rather than the large quantum gravitational based volume energy density (vacuum energy) having contributions of order $M_P^4$.

The group theoretical methods worked out by Bargmann, Mackey and Wigner, which deductively establish the Quantum Theory of a free particle for which Galileian transformations form a symmetry group, are extended to the case of an interacting particle. In doing so, the obstacles caused by loss of symmetry are overcome. In this approach, specific forms of the wave equation of an interacting particle, including the equation derived from the minimal coupling principle, are implied by particular first-order invariance properties that characterize the interaction with respect to specific subgroups of Galileian transformations; moreover, the possibility of yet unknown forms of the wave equation is left open.

Authors: Tung Ten Yong

In this paper, we explore realist models of quantum theory that does not fit into the standard definitions of ontological models. The models here go beyond standard definition of ontological models in the sense that quantum states do not correspond to distributions over the ontic state space and a system prepared in a quantum state is not in an ontic state. Instead, a system in a quantum state is always in a process, i.e. moving around in the ontic state space. Also, quantum measurement outcomes are not direct measurement of the ontic state, but depend probabilistically on the entire path the system takes during the measurement process. Consequently, we explain how, in our model, quantum states can neither be classified as ontic nor epistemic in the sense of knowledge about an underlying reality. In our model, quantum probabilities describes our (objective) knowledge about measurement outcomes. We also look at two hybrid models where either the preparation or measurement do follow the definitions in standard ontological models. Lastly, we propose a form of generalised ontological model that reduces to the standard PBR model when the underlying process reduces to a point in ontic space.

Authors: Leonardo Banchi, Daniel Burgarth, Michael J. Kastoryano

Randomness is an essential tool in many disciplines of modern sciences, such as cryptography, black hole physics, random matrix theory and Monte Carlo sampling. In quantum systems, random operations can be obtained via random circuits thanks to so-called q-designs, and play a central role in the fast scrambling conjecture for black holes. Here we consider a more physically motivated way of generating random evolutions by exploiting the many-body dynamics of a quantum system driven with stochastic external pulses. We combine techniques from quantum control, open quantum systems and exactly solvable models (via the Bethe-Ansatz) to generate Haar-uniform random operations in driven many-body systems. We show that any fully controllable system converges to a unitary q-design in the long-time limit. Moreover, we study the convergence time of a driven spin chain by mapping its random evolution into a semigroup with an integrable Liouvillean and finding its gap. Remarkably, we find via Bethe-Ansatz techniques that the gap is independent of q. We use mean-field techniques to argue that this property may be typical for other controllable systems, although we explicitly construct counter-examples via symmetry breaking arguments to show that this is not always the case. Our findings open up new physical methods to transform classical randomness into quantum randomness, via a combination of quantum many-body dynamics and random driving.

Authors: Robert B. Griffiths

The correctness of the consistent histories analysis of weakly interacting probes, related to the path of a particle, is maintained against the criticisms in the Comment, and against the alternative approach described there, which receives no support from standard (textbook) quantum mechanics.

Christian, Joy (2017) On a Surprising Oversight by John S. Bell in the Proof of his Famous Theorem. [Preprint]

Authors: Yuri Bonder

Quantum gravity phenomenology is the strategy towards quantum gravity where the priority is to make contact with experiments. Here I describe what I consider to be the best procedure to do quantum gravity phenomenology. The key step is to have a generic parametrization which allows one to perform self-consistency checks and to deal with many different experiments. As an example I describe the role that the Standard Model Extension has played when looking for Lorentz violation.

Authors: Marco Mamone-Capria

Some of the strategies which have been put forward in order to deal with the inconsistency between quantum mechanics and special relativity are examined. The EPR correlations are discussed as a simple example of quantum mechanical macroscopic effects with spacelike separation from their causes. It is shown that they can be used to convey information, whose reliability can be estimated by means of Bayes' theorem. Some of the current reasons advanced to deny that quantum mechanics contradicts special relativity are refuted, and an historical perspective is provided on the issue.

Authors: Md. Manirul Ali, Po-Wen Chen

We investigate the nonclassicality of an open quantum system using Leggett-Garg inequality (LGI) which test the correlations of a single system measured at different times. Violation of LGI implies nonclassical behavior of the open system. We investigate the violation of the Leggett-Garg inequality for a two level system (qubit) spontaneously decaying under a general non-Markovian dissipative environment. Our results are exact as we have calculated the two-time correlation functions exactly for a wide range of system-environment parameters beyond Born-Markov regime.

Authors: Ariel Caticha

Entropic Dynamics is a framework in which dynamical laws such as those that arise in physics are derived as an application of entropic methods of inference. No underlying action principle is postulated. Instead, the dynamics is driven by entropy subject to constraints reflecting the information that is relevant to the problem at hand. In this work I review the derivation of quantum theory but the fact that Entropic Dynamics is based on inference methods that are of universal applicability suggests that it may be possible to adapt these methods to fields other than physics.

Brown, Harvey R. (2017) The reality of the wavefunction: old arguments and new. [Preprint]
Jhun, Jennifer and Palacios, Patricia and Weatherall, James Owen (2017) Market Crashes as Critical Phenomena? Explanation, Idealization, and Universality in Econophysics. [Preprint]
Lampert, Timm and Säbel, Markus (2016) Wittgenstein's Elimination of Identity for Quantifier-Free Logic. [Preprint]

Authors: Carlos Sabín

We show how to use quantum metrology to detect a wormhole. A coherent state of the electromagnetic field experiences a phase shift with a slight dependence on the throat radius of a possible distant wormhole. We show that this tiny correction is, in principle, detectable by homodyne measurements after long propagation lengths for a wide range of throat radii and distances to the wormhole, even if the detection takes place very far away from the throat, where the spacetime is very close to a flat geometry. We use realistic parameters from state-of-the-art long-baseline laser interferometry, both Earth-based and space-borne. The scheme is, in principle, robust to optical losses and initial mixedness.

Authors: Francesco Vedovato, Costantino Agnesi, Matteo Schiavon, Daniele Dequal, Luca Calderaro, Marco Tomasin, Davide Giacomo Marangon, Andrea Stanco, Vincenza Luceri, Giuseppe Bianco, Giuseppe Vallone, Paolo Villoresi

Gedankenexperiments have consistently played a major role in the development of quantum theory. A paradigmatic example is Wheeler's delayed-choice experiment, a wave-particle duality test that cannot be fully understood using only classical concepts. Here, we implement Wheeler's idea along a satellite-ground interferometer which extends for thousands of kilometers in Space. We exploit temporal and polarization degrees of freedom of photons reflected by a fast moving satellite equipped with retro-reflecting mirrors. We observed the complementary wave-like or particle-like behaviors at the ground station by choosing the measurement apparatus while the photons are propagating from the satellite to the ground. Our results confirm quantum mechanical predictions, demonstrating the need of the dual wave-particle interpretation, at this unprecedented scale. Our work paves the way for novel applications of quantum mechanics in Space links involving multiple photon degrees of freedom.


Dynamical collapse models embody the idea of a physical collapse of the wave function in a mathematically well-defined way. They involve modifications to the standard rules of quantum theory in order to describe collapse as a physical process. This appears to introduce a time reversal asymmetry into the dynamics since the state at any given time depends on collapses in the past but not in the future. Here we challenge this conclusion by demonstrating that, subject to specified model constraints, collapse models can be given a structurally time symmetric formulation in which the collapse events are the primitive objects of the theory. Three different examples of time asymmetries associated with collapse models are then examined and in each case it is shown that the same dynamical rule determining the collapse events works in both the forward and backward in time directions. Any physically observed time asymmetries that arise in such models are due to the asymmetric imposition of initial or final time boundary conditions, rather than from an inherent asymmetry in the dynamical law. This is the standard explanation of time asymmetric behaviour resulting from time symmetric laws.


A large literature has grown up around the proposed use of ‘weak measurements’ (i.e., unsharp measurements followed by post-selection) to allegedly provide information about hidden ontological features of quantum systems. This paper attempts to clarify the fact that ‘weak measurements’ involve strong (projective) measurements on one (pointer) member of an entangled system. The only thing ‘weak’ about such measurements is that the correlation established via the entanglement does not correspond to eigenstates of the ‘weakly measured observable’ for the remaining component system(s) subject to the weak measurement. All observed statistics are straightforwardly and easily predicted by standard quantum mechanics. Specifically, it is noted that measurement of the pointer steers the remaining degree(s) of freedom into new states with new statistical properties—constituting a non-trivial (even if generally small) disturbance. In addition, standard quantum mechanics readily allows us to conditionalize on a final state if we choose, so the ‘post-selection’ that features prominently in time-symmetric formulations is also equipment from standard quantum theory. Assertions in the literature that weak measurements leave a system negligibly disturbed, and/or that standard quantum theory is cumbersome for computing the predicted measurement results, are therefore unsupportable, and ontological claims based on such assertions need to be critically reassessed.

Dawid, Richard and Hartmann, Stephan (2017) The No Miracles Argument without the Base Rate Fallacy. [Preprint]

Author(s): Philipp Strasberg, Gernot Schaller, Tobias Brandes, and Massimiliano Esposito

Nanomachines are subject to random thermal and quantum fluctuations that are not captured by traditional thermodynamic theory. A new theoretical investigation offers a step toward a unified nanoscale theory by showing how externally prepared systems (e.g., atoms in an optical cavity or DNA bases in an enzyme reaction) that interact with a nanoscopic device can be a source of nonequilbrium free energy.

[Phys. Rev. X 7, 021003] Published Fri Apr 07, 2017

Author(s): Yuan-Yuan Zhao, Paweł Kurzyński, Guo-Yong Xiang, Chuan-Feng Li, and Guang-Can Guo

The original Heisenberg error-disturbance relation was recently shown to be not universally valid and two different approaches to reformulate it were proposed. The first one focuses on how the error and disturbance of two observables A and B depend on a particular quantum state. The second one asks …

[Phys. Rev. A 95, 040101(R)] Published Fri Apr 07, 2017

Publication date: Available online 6 April 2017
Source:Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics
Author(s): Katie Robertson
Over many years, Aharonov and co-authors have proposed a new interpretation of quantum mechanics: the two-time interpretation. This interpretation assigns two wavefunctions to a system, one of which propagates forwards in time and the other backwards. In this paper, I argue that this interpretation does not solve the measurement problem. In addition, I argue that it is neither necessary nor sufficient to attribute causal power to the backwards-evolving wavefunction Φ | and thus its existence should be denied, contra the two-time interpretation. Finally, I follow Vaidman in giving an epistemological reading of Φ | .

Authors: Gabor Etesi

In this letter 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 is based on the $CPT$ theorem of relativistic quantum field theories while the other one is based on Noether's theorem of theoretical physics. 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 "no-hair" 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.

Authors: Stan Gudder

This paper begins with a theoretical explanation of why spacetime is discrete. The derivation shows that there exists an elementary length which is essentially Planck's length. We then show how the existence of this length affects time dilation in special relativity. We next consider the symmetry group for discrete spacetime. This symmetry group gives a discrete version of the usual Lorentz group. However, it is much simpler and is actually a discrete version of the rotation group. From the form of the symmetry group we deduce a possible explanation for the structure of elementary particle classes. Energy-momentum space is introduced and mass operators are defined. Discrete versions of the Klein-Gordon and Dirac equations are derived. The final section concerns discrete quantum field theory. Interaction Hamiltonians and scattering operators are considered. In particular, we study the scalar spin~0 and spin~1 bosons as well as the spin~$1/2$ fermion cases


Frauchiger and Renner have recently claimed to prove that “Single-world interpretations of quantum theory cannot be self-consistent”. This is contradicted by a construction due to Bell, inspired by Bohmian mechanics, which shows that any quantum system can be modelled in such a way that there is only one “world” at any time, but the predictions of quantum theory are reproduced. This Bell–Bohmian theory is applied to the experiment proposed by Frauchiger and Renner, and their argument is critically examined. It is concluded that it is their version of “standard quantum theory”, incorporating state vector collapse upon measurement, that is not self-consistent.

Maroney, O J E and Timpson, C G (2017) How is there a Physics of Information? On characterising physical evolution as information processing. [Preprint]
Gao, Shan (2017) Can particle configurations represent measurement results in Bohm's theory? [Preprint]
Arnold, Eckhart and Kästner, Johannes (2013) When can a Computer Simulation act as Substitute for an Experiment? A Case-Study from Chemisty. [Preprint]
Roberts, Bryan W. (2017) Rovelli on disharmony between the quantum arrows of time. [Preprint]
Roberts, Bryan W. (2017) Unreal Observables. Philosophy of Science.
Roberts, Bryan W. (2017) Observables, Disassembled. [Preprint]

Author(s): Dongfeng Gao, Jin Wang, and Mingsheng Zhan

Various models of quantum gravity imply the Planck-scale modifications of Heisenberg's uncertainty principle into a so-called generalized uncertainty principle (GUP). The GUP effects on high-energy physics, cosmology, and astrophysics have been extensively studied. Here, we focus on the weak-equival…

[Phys. Rev. A 95, 042106] Published Thu Apr 06, 2017

Authors: Bharath Ron

Physics is studying a system based on the information available about it. There are two approaches to physics deterministic and the nondeterministic. The deterministic approaches assume complete availability of information. Since full information about the system is never available nondeterministic approaches such as statistical physics and quantum physics are of high importance. This article is concerned with informational foundations of Physics and a description of time in terms of information. This article addresses the problem of time and a cluster of problems around measurement in quantum mechanics. It gives an interpretation for time in terms of information. The thermal time is shown to be emergent from the noncommutativity of quantum theory.

Authors: Yoav Levine, David Yakira, Nadav Cohen, Amnon Shashua

Deep convolutional networks have witnessed unprecedented success in various machine learning applications. Formal understanding on what makes these networks so successful is gradually unfolding, but for the most part there are still significant mysteries to unravel. The inductive bias, which reflects prior knowledge embedded in the network architecture, is one of them. In this work, we establish a fundamental connection between the fields of quantum physics and deep learning. We use this connection for asserting novel theoretical observations regarding the role that the number of channels in each layer of the convolutional network fulfills in the overall inductive bias. Specifically, we show an equivalence between the function realized by a deep convolutional arithmetic circuit (ConvAC) and a quantum many-body wave function, which relies on their common underlying tensorial structure. This facilitates the use of quantum entanglement measures as well-defined quantifiers of a deep network's expressive ability to model intricate correlation structures of its inputs. Most importantly, the construction of a deep ConvAC in terms of a Tensor Network is made available. This description enables us to carry a graph-theoretic analysis of a convolutional network, with which we demonstrate a direct control over the inductive bias of the deep network via its channel numbers, that are related min-cut in the underlying graph. This result is relevant to any practitioner designing a convolutional network for a specific task. We theoretically analyze ConvACs, and empirically validate our findings on more common ConvNets which involve ReLU activations and max pooling. Beyond the results described above, the description of a deep convolutional network in well-defined graph-theoretic tools and the formal connection to quantum entanglement, are two interdisciplinary bridges that are brought forth by this work.

Author(s): D. J. Bedingham and O. J. E. Maroney

The notion of a physical collapse of the wave function is embodied in dynamical collapse models. These involve a modification of the unitary evolution of the wave function so as to give a dynamical account of collapse. The resulting dynamics is at first sight time asymmetric for the simple reason th…

[Phys. Rev. A 95, 042103] Published Wed Apr 05, 2017

Huggett, Nick (2014) Reading the Past in the Present. [Preprint]
Gao, Shan (2017) Failure of psychophysical supervenience in Everett's theory. [Preprint]
Publication date: Available online 31 March 2017
Source:Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics
Author(s): Alexei Grinbaum
Dirac sought an interpretation of mathematical formalism in terms of physical entities and Einstein insisted that physics should describe “the real states of the real systems”. While Bell inequalities put into question the reality of states, modern device-independent approaches do away with the idea of entities: physical theory may contain no physical systems. Focusing on the correlations between operationally defined inputs and outputs, device-independent methods promote a view more distant from the conventional one than Einstein׳s ‘principle theories’ were from ‘constructive theories’. On the examples of indefinite causal orders and almost quantum correlations, we ask a puzzling question: if physical theory is not about systems, then what is it about? Device-independent models suggest that physical theory can be ‘about’ languages.

Grinbaum, Alexei (2017) The Effectiveness of Mathematics in Physics of the Unknown. [Preprint]
Feintzeig, Benjamin H. (2017) On the Choice of Algebra for Quantization. [Preprint]

Authors: Stefano Gogioso

We present a uniform framework for the treatment of a large class of toy models of quantum theory. Specifically, we will be interested in theories of wavefunctions valued in commutative involutive semirings, and which give rise to some semiring-based notion of classical non-determinism via the Born rule. The models obtained with our construction possess many of the familiar structures used in Categorical Quantum Mechanics. We also provide a bestiary of increasingly exotic examples: some well known, such as real quantum theory and relational quantum theory; some less known, such as hyperbolic quantum theory, p-adic quantum theory and "parity quantum theory"; and some entirely new, such as "finite-field quantum theory" and "tropical quantum theory". As a further bonus, the measurement scenarios arising within these theories can be studied using the sheaf-theoretic framework for non-locality and contextuality.

Authors: Ward Struyve

Loop quantum gravity is believed to eliminate singularities such as the big bang and big crunch singularity. In order to base this belief on theoretical analysis, the notorious problems such as the problem of time and the problem of the actual meaning of singularities must be addressed and eventually overcome. In this paper, we address the problem of singularities in the context of the Bohmian formulation of loop quantum cosmology (which describes symmetry-reduced models of quantum gravity using the quantization techniques of loop quantum gravity). This formulation solves the mentioned conceptual problems. For example the notion of singularity is clear in this case, since there is an actual metric in addition to the wave function. As such, there is a singularity whenever this actual metric is singular. It is shown that in the loop quantum cosmology for a homogeneous and isotropic Friedmann-Lemaitre-Robertson-Walker space-time with arbitrary constant spatial curvature and possibly a cosmological constant, coupled to a massless homogeneous scalar field, a big bang or big crunch singularity is never obtained. This result is obtained without assuming any boundary conditions. This result should also be contrasted with the fact that in the Bohmian formulation of the Wheeler-DeWitt theory singularities may exist (depending on the wave function and the initial conditions for the metric and scalar field).

Authors: H. D. Zeh

Time-asymmetric spacetime structures, in particular those representing black holes and the expansion of the universe, are intimately related to other arrows of time, such as the second law and the retardation of radiation. The nature of the quantum arrow, often attributed to a collapse of the wave function, is essential, in particular, for understanding the much discussed "black hole information loss paradox". However, this paradox assumes a new form and can possibly be avoided in a consistent causal treatment that may be able to avoid horizons and singularities. The master arrow that would combine all arrows of time does not have to be identified with a direction of the formal time parameter that serves to formulate the dynamics as a succession of global states (a trajectory in configuration or Hilbert space). It may even change direction with respect to a fundamental physical clock such as the cosmic expansion parameter if this was formally extended either into a future contraction era or to negative "pre-big-bang" values.

Authors: Tom Banks

I propose that much recent history can be explained by hypothesizing that sometime during the last quarter of 2016, the history of the world underwent a macroscopic quantum tunneling event, creating, according to the Many Worlds Interpretation, a new branch of the multiverse in which my consciousness and that of my readers is now trapped. The failure of much political polling is then understood by assuming that the particular branch we are on had very low amplitude in the quantum wave function of the multiverse. In this view, one must take a different attitude towards alternative facts than that proposed by the mainstream media. We know that quantum tunneling can change the low energy laws of physics in the different branches of the wave function. Alternative facts may simply be the reflection of the media's ignorance of the state of the world after a quantum transition of this magnitude.

Authors: Sujoy K. Modak, Daniel Sudarsky

We give general overview of a novel approach, recently developed by us, to address the issue black hole information paradox. This alternative viewpoint is based on theories involving modifications of standard quantum theory, known as "spontaneous dynamical state reduction" or "wave-function collapse models" which were historically developed to overcome the notorious foundational problems of quantum mechanics known as the "measurement problem". We show that these proposals, when appropriately adapted and refined for this context, provide a self-consistent picture where loss of information in the evaporation of black holes is no longer paradoxical.

Authors: John T. Brooker

This paper presents an alternative quantum theory, the Theory of Discrete Extension, which avoids many of the conceptual problems of standard quantum mechanics. It is a deterministic, dynamic collapse theory with a well-defined primitive ontology.

In place of the dual, classical concepts of wave and particle, the unitary, non-classical concept of a discretely extended object emerges directly from the theory's dynamic equations as a primitive ontology. Because this ontology is unitary, the theory avoids the dilemmas of wave-particle dualism and complementarity.

Furthermore, the theory's dynamic equations generate correct, quasi-discrete values of action increments and energy levels without recourse to the operator formalism and eigenvalue postulate of standard quantum mechanics. Quantization of the harmonic oscillator provides a simple illustration.

The theory provides insight into the nature of a number of quantum effects such as the zero-point energy of the harmonic oscillator. It also makes a number of predictions that distinguish it from standard quantum mechanics and from Bohmian mechanics.

Authors: Yuan Yuan, Zhibo Hou, Yuan-Yuan Zhao, Han-Sen Zhong, Guo-Yong Xiang, Chuan-Feng Li, Guang-Can Guo

Wave-particle duality is a typical example of Bohr's principle of complementarity that plays a significant role in quantum mechanics. Previous studies used visibility to quantify wave property and used path information to quantify particle property. However, coherence is the core and basis of the interference phenomena of wave. If we use it to characterize wave property, which will be useful to strengthen the understanding of wave-particle duality. A recent theoretical work [Phys. Rev. Lett. 116, 160406 (2016)] found two relations between wave property quantified by coherence in different measure and particle property. Here, we demonstrated the wave-particle duality based on two coherence measures quantitatively for the first time. The path information can be obtained by the discrimination of detector states encoded in polarization of photons corresponding each path and mutual information between detector states and the outcome of the measurement performed on them. We obtain wave property quantified by coherence in l1 measure and relative entropy measure using tomography of photon state that encoded in paths. Our work will deepen people's further understanding of coherence and provides a new angle of view for wave-particle duality.

Authors: Christos Efthymiopoulos, George Contopoulos, Athanasios C. Tzemos

We discuss the main mechanisms generating chaotic behavior of the quantum trajectories in the de Broglie - Bohm picture of quantum mechanics, in systems of two and three degrees of freedom. In the 2D case, chaos is generated via multiple scatterings of the trajectories with one or more `nodal point - X-point complexes'. In the 3D case, these complexes form foliations along `nodal lines' accompanied by `X-lines'. We also identify cases of integrable or partially integrable quantum trajectories. The role of chaos is important in interpreting the dynamical origin of the `quantum relaxation' effect, i.e. the dynamical emergence of Born's rule for the quantum probabilities, which has been proposed as an extension of the Bohmian picture of quantum mechanics. In particular, the local scaling laws characterizing the chaotic scattering phenomena near X-points, or X-lines, are related to the global rate at which the quantum relaxation is observed to proceed. Also, the degree of chaos determines the rate at which nearly-coherent initial wavepacket states lose their spatial coherence in the course of time.

Authors: Stefan Ataman

Entangled states are notoriously non-separable, their sub-ensembles being only statistical mixtures yielding no coherences and no quantum interference phenomena. The interesting features of entangled states can be revealed only by coincidence counts over the (typically) two sub-ensembles of the system. In this paper we show that this feature extends to properties thought to be local, for example the transmissivity coefficient of a beam splitter. We discuss a well-known experimental setup and propose modifications, so that delayed-choice can be added and this new feature of entanglement tested.

Authors: Johann Marton, S. Bartalucci, A. Bassi, M. Bazzi, S. Bertolucci, C. Berucci, M. Bragadireanu, M. Cargnelli, A. Clozza, Catalina Curceanu, L. De Paolis, S. Di Matteo, S.Donadi, J.-P. Egger, C. Guaraldo, M. Iliescu, M. Laubenstein, E. Milotti, Andreas Pichler, D. Pietreanu, K. Piscicchia, A. Scordo, H. Shi, D. Sirghi F. Sirghi, L. Sperandio, O. Vazquez-Doce, E. Widmann, J. Zmeskal

We are experimentally investigating possible violations of standard quantum mechanics predictions in the Gran Sasso underground laboratory in Italy. We test with high precision the Pauli Exclusion Principle and the collapse of the wave function (collapse models). We present our method of searching for possible small violations of the Pauli Exclusion Principle (PEP) for electrons, through the search for anomalous X-ray transitions in copper atoms, produced by fresh electrons (brought inside the copper bar by circulating current) which can have the probability to undergo Pauli-forbidden transition to the 1 s level already occupied by two electrons and we describe the VIP2 (VIolation of PEP) experiment under data taking at the Gran Sasso underground laboratories. In this paper the new VIP2 setup installed in the Gran Sasso underground laboratory will be presented. The goal of VIP2 is to test the PEP for electrons with unprecedented accuracy, down to a limit in the probability that PEP is violated at the level of 10$^{-31}$. We show preliminary experimental results and discuss implications of a possible violation.

Authors: B.L. van der Waerden in Groningen (Holland), Guglielmo Pasa

"Let us call the novel quantities which, in addition to the vectors and tensors, have appeared in the quantum mechanics of the spinning electron, and which in the case of the Lorentz group are quite differently transformed from tensors, as spinors for short. Is there no spinor analysis that every physicist can learn, such as tensor analysis, and with the aid of which all the possible spinors can be formed, and secondly, all the invariant equations in which spinors occur?" So Mr Ehrenfest asked me and the answer will be given below.

Redhead, Michael (2017) The Relativistic Einstein-Podolsky-Rosen Argument. [Preprint]

Author(s): M. Bilardello, A. Trombettoni, and A. Bassi

We investigate how ultracold atoms in double-well potentials can be used to study and put bounds on models describing wave-function collapse. We refer in particular to the continuous spontaneous localization (CSL) model, which is the most well studied among dynamical reduction models. It modifies th…

[Phys. Rev. A 95, 032134] Published Wed Mar 29, 2017

Author(s): Eduardo O. Dias and Fernando Parisio

In quantum theory we refer to the probability of finding a particle between positions x and x+dx at the instant t, although we have no capacity of predicting exactly when the detection occurs. In this work, we first present an extended nonrelativistic quantum formalism where space and time play equi…

[Phys. Rev. A 95, 032133] Published Wed Mar 29, 2017

Publication date: Available online 28 March 2017
Source:Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics
Author(s): Jean-Philippe Martinez
The Hartree-Fock method, one of the first applications of the new quantum mechanics in the frame of the many-body problem, had been elaborated by Rayner Douglas Hartree in 1928 and Vladimir Fock in 1930. Promptly, the challenge of tedious computations was being discussed and it is well known that the application of the method benefited greatly from the development of computers from the mid-to-late 1950s. However, the years from 1930 to 1950 were by no means years of stagnation, as the method was the object of several considerations related to its mathematical formulation, possible extension, and conceptual understanding. Thus, with a focus on the respective attitudes of Hartree and Fock, in particular with respect to the concept of quantum exchange, the present work puts forward some mathematical and conceptual clarifications, which played an important role for a better understanding of the many-body problem in quantum mechanics.

Battle between quantum and thermodynamic laws heats up

Nature 543, 7647 (2017).

Author: Davide Castelvecchi

Physicists try to rebuild the laws of heat and energy for processes at a quantum scale.

Volume 3, Issue 2, pages 31-64

Jean Bricmont [Show Biography]

I was born 12 April 1952 in Belgium; I got my phD in 1977 at the University of Louvain in Belgium. I worked at Rutgers and Princeton universities and have been a professor of theoretical physics at the university of Louvain, but I am now retired. I worked on statistical mechanics, the renormalization group and nonlinear partial differential equations. I am also interested in making sense of quantum mechanics, see

The goal of this paper is to explain how the views of Albert Einstein, John Bell and others, about nonlocality and the conceptual issues raised by quantum mechanics, have been rather systematically misunderstood by the majority of physicists.

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