# Weekly Papers on Quantum Foundations (18)

This is a list of this week’s papers on quantum foundations published in various journals or uploaded to preprint servers such as arxiv.org and PhilSci Archive.

The Reality of Casimir Friction. (arXiv:1508.00626v2 [quant-ph] UPDATED)

on 2016-4-29 12:38am GMT

Authors: K. A. MiltonJ. S. HøyeI. Brevik

For more than 35 years theorists have studied quantum or Casimir friction, which occurs when two smooth bodies move transversely to each other, experiencing a frictional dissipative force due to quantum electromagnetic fluctuations, which break time-reversal symmetry. These forces are typically very small, unless the bodies are nearly touching, and consequently such effects have never been observed, although lateral Casimir forces have been seen for corrugated surfaces. Partly because of the lack of contact with phenomena, theoretical predictions for the frictional force between parallel plates, or between a polarizable atom and a metallic plate, have varied widely. Here we review the history of these calculations, show that theoretical consensus is emerging, and offer some hope that it might be possible to experimentally confirm this phenomenon of dissipative quantum electrodynamics.

Entanglement Conservation, ER=EPR, and a New Classical Area Theorem for Wormholes. (arXiv:1604.08217v1 [hep-th])

on 2016-4-29 12:38am GMT

Authors: Grant RemmenNing BaoJason Pollack

We consider the question of entanglement conservation in the context of the ER=EPR correspondence equating quantum entanglement with wormholes. In quantum mechanics, the entanglement between a system and its complement is conserved under unitary operations that act independently on each; ER=EPR suggests that an analogous statement should hold for wormholes. We accordingly prove a new area theorem in general relativity: for a collection of dynamical wormholes and black holes in a spacetime satisfying the null curvature condition, the maximin area for a subset of the horizons (giving the largest area attained by the minimal cross section of the multi-wormhole throat separating the subset from its complement) is invariant under classical time evolution along the outermost apparent horizons. The evolution can be completely general, including horizon mergers and the addition of classical matter satisfying the null energy condition. This theorem is the gravitational dual of entanglement conservation and thus constitutes an explicit characterization of the ER=EPR duality in the classical limit.

A Modest View of Bell’s Theorem. (arXiv:1604.08529v1 [physics.hist-ph])

on 2016-4-29 12:38am GMT

Authors: Stephen Boughn

In the 80 years since the seminal Einstein, Podolsky, and Rosen (EPR) paper, physicists and philosophers have mused about the spooky action at a distance’ aspect of quantum mechanics that so bothered Einstein. In his formal analysis of EPR-type entangled quantum states, Bell (1964) concluded that any hidden variable theory designed to reproduce the predictions of quantum mechanics must necessarily be nonlocal and allow superluminal interactions. This doesn’t immediately imply that nonlocality is a characteristic feature of quantum mechanics let alone a fundamental property of nature; however, many physicists and philosophers of science do harbor this belief. Experts in the field often use the term nonlocality’ to designate particular non-classical aspects of quantum entanglement and do not confuse the term with superluminal interactions. However, many physicists seem to take the term more literally. I endeavor to disabuse the latter of this notion by emphasizing that the correlations of Bell-type entanglement are a result of ordinary quantum superposition with no need to introduce nonlocality. The conclusion of the EPR paper wasn’t that quantum mechanics is nonlocal but rather that it is an incomplete description of reality. For different reasons, many physicists, including me, agree with Einstein that quantum mechanics is necessarily an incomplete description of reality.

Probabilistic Foundations of Contextuality. (arXiv:1604.08412v1 [quant-ph])

on 2016-4-29 12:38am GMT

Authors: Ehtibar DzhafarovJanne Kujala

Contextuality is usually defined as absence of a joint distribution for a set of measurements (random variables) with known joint distributions of some of its subsets. However, if these subsets of measurements are not disjoint, contextuality is mathematically impossible even if one generally allows (as one must) for random variables not to be jointly distributed. To avoid contradictions one has to adopt the Contextuality-by-Default approach: measurements made in different contexts are always distinct and stochastically unrelated to each other. Contextuality is reformulated then in terms of the (im)possibility of imposing on all the measurements in a system a joint distribution of a particular kind: such that any measurements of one and the same property made in different contexts satisfy a specified property, $\mathcal{C}$. In the traditional analysis of contextuality $\mathcal{C}$ means “are equal to each other with probability 1”. However, if the system of measurements violates the “no-disturbance principle”, due to signaling or experimental biases, then the meaning of $\mathcal{C}$ has to be generalized, and the proposed generalization is “are equal to each other with maximal possible probability” (applied to any set of measurements of one and the same property). This approach is illustrated on arbitrary systems of binary measurements, including most of quantum systems of traditional interest in contextuality studies (irrespective of whether “no-disturbance” principle holds in them).

Quantum Cognition Beyond Hilbert Space I: Fundamentals. (arXiv:1604.08268v1 [cs.AI])

on 2016-4-29 12:38am GMT

The formalism of quantum theory in Hilbert space has been applied with success to the modeling and explanation of several cognitive phenomena, whereas traditional cognitive approaches were problematical. However, this ‘quantum cognition paradigm’ was recently challenged by its proven impossibility to simultaneously model ‘question order effects’ and ‘response replicability’. In Part I of this paper we describe sequential dichotomic measurements within an operational and realistic framework for human cognition elaborated by ourselves, and represent them in a quantum-like ‘extended Bloch representation’ where the Born rule of quantum probability does not necessarily hold. In Part II we apply this mathematical framework to successfully model question order effects, response replicability and unpacking effects, thus opening the way toward quantum cognition beyond Hilbert space.

Quantum cognition beyond Hilbert space II: Applications. (arXiv:1604.08270v1 [cs.AI])

on 2016-4-29 12:38am GMT

The research on human cognition has recently benefited from the use of the mathematical formalism of quantum theory in Hilbert space. However, cognitive situations exist which indicate that the Hilbert space structure, and the associated Born rule, would be insufficient to provide a satisfactory modeling of the collected data, so that one needs to go beyond Hilbert space. In Part I of this paper we follow this direction and present a general tension-reduction (GTR) model, in the ambit of an operational and realistic framework for human cognition. In this Part II we apply this non-Hilbertian quantum-like model to faithfully reproduce the probabilities of the ‘Clinton/Gore’ and ‘Rose/Jackson’ experiments on question order effects. We also explain why the GTR-model is needed if one wants to deal, in a fully consistent way, with response replicability and unpacking effects.

Optimal processes for probabilistic work extraction beyond the second law. (arXiv:1604.08094v1 [quant-ph])

on 2016-4-28 2:07am GMT

According to the second law of thermodynamics, for every transformation performed on a system which is in contact with an environment of fixed temperature, the extracted work is bounded by the decrease of the free energy of the system. However, in a single realization of a generic process, the extracted work is subject to statistical fluctuations which may allow for probabilistic violations of the previous bound. We are interested in enhancing this effect, i.e. we look for thermodynamic processes that maximize the probability of extracting work above a given arbitrary threshold. For any process obeying the Jarzynski identity, we determine an upper bound for the work extraction probability that depends also on the minimum amount of work that we are willing to extract in case of failure, or on the average work we wish to extract from the system. Then we show that this bound can be saturated within the thermodynamic formalism of quantum discrete processes composed by sequences of unitary quenches and complete thermalizations. We explicitly determine the optimal protocol which is given by two quasi-static isothermal transformations separated by a finite unitary quench.

Locally Causal and Deterministic Interpretations of Quantum Mechanics: Parallel Lives and Cosmic Inflation. (arXiv:1604.07874v1 [quant-ph])

on 2016-4-28 2:07am GMT

Authors: Mordecai Waegell

Several locally deterministic interpretations of quantum mechanics are presented and reviewed. The fundamental differences between these interpretations are made transparent by explicitly showing what information is carried locally by each physical system in an idealized experimental test of Bell’s theorem. This also shows how each of these models can be locally causal and deterministic. First, a model is presented which avoids Bell’s arguments through the assumption that space-time inflated from an initial singularity, which encapsulates the entire past light cone of every event in the universe. From this assumption, it is shown how quantum mechanics can produce locally consistent reality by choosing one of many possible futures at the time of the singularity. Secondly, we review and expand the Parallel Lives interpretation of Brassard and Raymond-Robichaud, which maintains local causality and determinism by abandoning the strictest notion of realism. Finally, the two ideas are combined, resulting in a parallel lives model in which lives branch apart earlier, under the assumption of a single unified interaction history. The physical content of weak values within each model is discussed, along with related philosophical issues concerning free will.

Quantum Shannon Theory. (arXiv:1604.07450v1 [quant-ph] CROSS LISTED)

on 2016-4-28 2:05am GMT

Authors: John Preskill

This is the 10th and final chapter of my book on Quantum Information, based on the course I have been teaching at Caltech since 1997. An early version of this chapter (originally Chapter 5) has been available on the course website since 1998, but this version is substantially revised and expanded. The level of detail is uneven, as I’ve aimed to provide a gentle introduction, but I’ve also tried to avoid statements that are incorrect or obscure. Generally speaking, I chose to include topics that are both useful to know and relatively easy to explain; I had to leave out a lot of good stuff, but on the other hand the chapter is already quite long. This is a working draft of Chapter 10, which I will continue to update. See the URL on the title page for further updates and drafts of other chapters, and please send me an email if you notice errors. Eventually, the complete book will be published by Cambridge University Press.

Quantum Statistical Mechanical Derivation of the Second Law of Thermodynamics: A Hybrid Setting Approach

PRL: General Physics: Statistical and Quantum Mechanics, Quantum Information, etc.

on 2016-4-27 2:00pm GMT

Author(s): Hal Tasaki

Based on quantum statistical mechanics and microscopic quantum dynamics, we prove Planck’s and Kelvin’s principles for macroscopic systems in a general and realistic setting. We consider a hybrid quantum system that consists of the thermodynamic system, which is initially in thermal equilibrium, and…

[Phys. Rev. Lett. 116, 170402] Published Wed Apr 27, 2016

Towards better understanding of QBism. (arXiv:1604.07766v1 [quant-ph])

on 2016-4-27 1:52am GMT

Authors: Andrei Khrennikov

Recently I posted a paper entitled “External observer reflections on QBism”. As any external observable, I was not able to reflect some features of QBism properly. Therefore comments which I received from one of its creators, C. Fuchs, are very valuable – to understand better the views of QBists. Some of QBism features are very delicate and to extract them from articles of QBists is not a simple task. Therefore I hope that the second portion of my reflection on QBism (or better to say my reflections on Fuchs’ reflections on my reflections) might be interesting and useful for other experts in quantum foundations and quantum information theory (especially by taking into account my previous aggressively anti-QBism position). In the present paper I correct some of my previously posted critical comments on QBism. At the same time better understanding of QBists views on some problems leads to improvement and strengthening of other critical comments.

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Bounding quantum gravity inspired decoherence using atom interferometry. (arXiv:1604.07810v1 [quant-ph])

on 2016-4-27 1:52am GMT

Hypothetical models have been proposed in which explicit collapse mechanisms prevent the superposition principle to hold at large scales. In particular, the model introduced by Ellis and co-workers [Phys. Lett. B ${\bf 221}$, 113 (1989)] suggests that quantum gravity might be responsible for the collapse of the wavefunction of massive objects in spatial superpositions. We here consider a recent experiment reporting on interferometry with atoms delocalized over half a meter for timescale of a second [Nature ${\bf 528}$, 530 (2015)] and show that the corresponding data strongly bound quantum gravity induced decoherence and rule it out in the parameter regime considered originally.

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Bypassing the Groenewold–van Hove Obstruction: A Physically Meaningful Quantization for R2n. (arXiv:1604.07754v1 [math-ph])

on 2016-4-27 1:52am GMT

Authors: Maurice de Gosson

There are known obstructions to a full geometric quantization of R2n, the most known being the Groenewold-van Hove no-go result. We show, following a suggestion of S. Kauffmann, that it is possible to construct a unique quantization procedure by weakening the usual requirement that commutators should correspond to Poisson brackets. The weaker requirement consists in demanding that this correspondence should only hold for Hamiltonian functions of the type T(p)+V(q). This reformulation leads to a non-injective quantization of all tempered distributions on R2n which, when restricted to polynomials, is the rule proposed by the physicists Born and Jordan in the early days of quantum mechanics.

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Popescu-Rohrlich correlations imply efficient instantaneous nonlocal quantum computation. (arXiv:1512.04930v2 [quant-ph] UPDATED)

on 2016-4-27 1:52am GMT

In instantaneous nonlocal quantum computation, two parties cooperate in order to perform a quantum computation on their joint inputs, while being restricted to a single round of simultaneous communication. Previous results showed that instantaneous nonlocal quantum computation is possible, at the cost of an exponential amount of prior shared entanglement (in the size of the input). Here, we show that a linear amount of entanglement suffices, (in the size of the computation), as long as the parties share nonlocal correlations as given by the Popescu-Rohlich box. This means that communication is not required for efficient instantaneous nonlocal quantum computation. Exploiting the well-known relation to position-based cryptography, our result also implies the impossibility of secure position-based cryptography against adversaries with non-signalling correlations. Furthermore, our construction establishes a quantum analogue of the classical communication complexity collapse under non-signalling correlations.

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Trading coherence and entropy by a quantum Maxwell demon. (arXiv:1604.07557v1 [quant-ph])

on 2016-4-27 1:52am GMT

Authors: A. V. LebedevD. OehriG. B. LesovikG. Blatter

The Second Law of Thermodynamics states that the entropy of a closed system is non-decreasing. Discussing the Second Law in the quantum world poses new challenges and provides new opportunities, involving fundamental quantum-information-theoretic questions and novel quantum-engineered devices. In quantum mechanics, systems with an evolution described by a so-called unital quantum channel evolve with a non-decreasing entropy. Here, we seek the opposite, a system described by a non-unital and, furthermore, energy-conserving channel that describes a system whose entropy decreases with time. We propose a setup involving a mesoscopic four-lead scatterer augmented by a micro-environment in the form of a spin that realizes this goal. Within this non-unital and energy-conserving quantum channel, the micro-environment acts with two non-commuting operations on the system in an autonomous way. We find, that the process corresponds to a partial exchange or swap between the system and environment quantum states, with the system’s entropy decreasing if the environment’s state is more pure. This entropy-decreasing process is naturally expressed through the action of a quantum Maxwell demon and we propose a quantum-thermodynamic engine with four qubits that extracts work from a single heat reservoir when provided with a reservoir of pure qubits. The special feature of this engine, which derives from the energy-conservation in the non-unital quantum channel, is its separation into two cycles, a working cycle and an entropy cycle, allowing to run this engine with no local waste heat.

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Quantum circuit dynamics via path integrals: Is there a classical action for discrete-time paths?. (arXiv:1604.07452v1 [quant-ph])

on 2016-4-27 1:52am GMT

It is straightforward to give a sum-over-paths expression for the transition amplitudes of a quantum circuit as long as the gates in the circuit are balanced, where to be balanced is to have all nonzero transition amplitudes of equal magnitude. Here we consider the question of whether, for such circuits, the relative phases of different discrete-time paths through the configuration space can be defined in terms of a classical action, as they are for continuous-time paths. We show how to do so for certain kinds of quantum circuits, namely, Clifford circuits where the elementary systems are continuous-variable systems or discrete systems of odd-prime dimension. These types of circuit are distinguished by having phase-space representations that serve to define their classical counterparts. For discrete systems, the phase-space coordinates are also discrete variables. We show that for each gate in the generating set, one can associate a symplectomorphism on the phase-space and to each of these one can associate a generating function, defined on two copies of the configuration space. For discrete systems, the latter association is achieved using tools from algebraic geometry. Finally, we show that if the action functional for a discrete-time path through a sequence of gates is defined using the sum of the corresponding generating functions, then it yields the correct relative phases for the path-sum expression. These results are likely to be relevant for quantizing physical theories where time is fundamentally discrete, characterizing the classical limit of discrete-time quantum dynamics, and proving complexity results for quantum circuits.

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Single-world interpretations of quantum theory cannot be self-consistent. (arXiv:1604.07422v1 [quant-ph])

on 2016-4-27 1:52am GMT

Authors: Daniela FrauchigerRenato Renner

According to quantum theory, a measurement may have multiple possible outcomes. Single-world interpretations assert that, nevertheless, only one of them “really” occurs. Here we propose a gedankenexperiment where quantum theory is applied to model an experimenter who herself uses quantum theory. We find that, in such a scenario, no single-world interpretation can be logically consistent. This conclusion extends to deterministic hidden-variable theories, such as Bohmian mechanics, for they impose a single-world interpretation.

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Classical approximations of relativistic quantum physics. (arXiv:1604.07654v1 [quant-ph])

on 2016-4-27 1:52am GMT

Authors: Glenn Eric Johnson

A correspondence of classical to quantum physics studied by Schr\”{o}\-dinger and Ehrenfest applies without the necessity of technical conjecture that classical observables are associated with Hermitian Hilbert space operators. This correspondence provides appropriate nonrelativistic classical interpretations to realizations of relativistic quantum physics that are incompatible with the canonical formalism. Using this correspondence, Newtonian mechanics for a $1/r$ potential provides approximations for the dynamics of nonrelativistic classical particle states within unconstrained quantum field theory (UQFT).

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Replacing the Singlet Spinor of the EPR-B Experiment in the Configuration Space with Two Single-Particle Spinors in Physical Space

Latest Results for Foundations of Physics

on 2016-4-27 12:00am GMT

Abstract

Recently, for spinless non-relativistic particles, Norsen (Found Phys 40:1858–1884, 2010) and Norsen et al. (Synthese 192:3125–3151,2015) show that in the de Broglie–Bohm interpretation it is possible to replace the wave function in the configuration space by single-particle wave functions in physical space. In this paper, we show that this replacment of the wave function in the configuration space by single-particle functions in the 3D-space is also possible for particles with spin, in particular for the particles of the EPR-B experiment, the Bohm version of the Einstein–Podolsky–Rosen experiment.

Fine Structure Constant: Theme With Variations. (arXiv:1604.07092v1 [gr-qc])

on 2016-4-26 11:57am GMT

In this paper, we study the spatial variation of the fine structure constant $\alpha$ due to the presence of a static and spherically symmetric gravitational source. The procedure consists of calculating the solution including the energy eigenvalues of a massive scalar field around that source, considering the weak-field regimen, which yields the gravitational analog of the atomic Bohr levels. From this result, we obtain several values for the effective $\alpha$ by considering some scenarios of semi-classical and quantum gravities. Constraints on the parameters of the involved theories are calculated from astrophysical observations of the white dwarf emission spectra. Such constraints are compared with those ones obtained in the literature.

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Emergence, causation and storytelling: condensed matter physics and the limitations of the human mind. (arXiv:1604.06845v1 [physics.hist-ph])

on 2016-4-26 11:57am GMT

Authors: S. J. Blundell

The physics of matter in the condensed state is concerned with problems in which the number of constituent particles is vastly greater than can be easily comprehended. The inherent physical limitations of the human mind are fundamental and restrict the way in which we can interact with and learn about the universe. This presents challenges for developing scientific explanations that are met by emergent narratives, concepts and arguments that have a non-trivial relationship to the underlying microphysics. By examining examples within condensed matter physics, and also from cellular automata, I show how such emergent narratives efficiently describe elements of reality.

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A strict epistemic approach to physics. (arXiv:1601.00680v2 [quant-ph] UPDATED)

on 2016-4-26 11:57am GMT

Authors: Per Östborn

The general view is that all fundamental physical laws should be formulated within the framework given by quantum mechanics (QM). In a sense, QM therefore has the character of a metaphysical theory. Consequently, if it is possible to derive QM from more basic principles, these principles should be of general, philosophical nature. Here, we derive the formalism of QM from well-motivated epistemic principles. A key assumption is that a physical theory that relies on entities or distinctions that are unknowable in principle gives rise to wrong predictions. First, an epistemic formalism is developed, using concepts like knowledge and potential knowledge, identifying a physical state $S$ with the potential knowledge of the physical world. It is demonstrated that QM emerges from this formalism. However, Hilbert spaces, wave functions and probabilities are defined in certain well-defined observational contexts only. This means that the epistemic formalism is broader than QM. In the fundamental layer of description, the physical state $S$ is a subset of a state space $\mathcal{S}=\{Z\}$, such that $S$ always contains many elements $Z$. These elements correspond to unattainable states of complete knowledge of the world. The evolution of $S$ cannot be determined in terms of the individual evolution of the elements $Z$, unlike the evolution of an ensemble in classical phase space. The evolution of $S$ is described in terms of sequential time $n\in \mathbf{\mathbb{N}}$, which is updated according to $n\rightarrow n+1$ each time an event occurs, each time potential knowledge changes. Sequential time $n$ can be separated from relational time $t$, which describes distances between events in space-time. There is an entire space-time associated with each $n$, in which $t$ represents the knowledge at sequential time $n$ about the temporal relations between present and past events.

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Quantum Measurement, Complexity and Discrete Physics. (arXiv:quant-ph/0310033v2 UPDATED)

on 2016-4-26 11:57am GMT

Authors: Martin Leckey

This paper presents a new modified quantum mechanics, Critical Complexity Quantum Mechanics, which includes a new account of wavefunction collapse. This modified quantum mechanics is shown to arise naturally from a fully discrete physics, where all physical quantities are discrete rather than continuous. I compare this theory with the spontaneous collapse theories of Ghirardi, Rimini, Weber and Pearle and discuss some implications of the theory for a realist view of the quantum realm.

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Logical inference approach to relativistic quantum mechanics: derivation of the Klein-Gordon equation. (arXiv:1604.07265v1 [quant-ph])

on 2016-4-26 11:57am GMT

The logical inference approach to quantum theory, proposed earlier [Ann. Phys. 347 (2014) 45-73], is considered in a relativistic setting. It is shown that the Klein-Gordon equation for a massive, charged, and spinless particle derives from the combination of the requirements that the space-time data collected by probing the particle is obtained from the most robust experiment and that on average, the classical relativistic equation of motion of a particle holds.

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Quantum features of natural cellular automata. (arXiv:1604.06652v1 [quant-ph])

on 2016-4-25 12:06pm GMT

Authors: Hans-Thomas Elze

Cellular automata can show well known features of quantum mechanics, such as a linear rule according to which they evolve and which resembles a discretized version of the Schroedinger equation. This includes corresponding conservation laws. The class of “natural” Hamiltonian cellular automata is based exclusively on integer-valued variables and couplings and their dynamics derives from an Action Principle. They can be mapped reversibly to continuum models by applying Sampling Theory. Thus, “deformed” quantum mechanical models with a finite discreteness scale $l$ are obtained, which for $l\rightarrow 0$ reproduce familiar continuum results. We have recently demonstrated that such automata can form “multipartite” systems consistently with the tensor product structures of nonrelativistic many-body quantum mechanics, while interacting and maintaining the linear evolution. Consequently, the Superposition Principle fully applies for such primitive discrete deterministic automata and their composites and can produce the essential quantum effects of interference and entanglement.

Relativistic collapse dynamics and black hole information loss. (arXiv:1604.06537v1 [gr-qc])

on 2016-4-25 12:06pm GMT

We study a proposal for the resolution of the black hole information puzzle within the context of modified versions of quantum theory involving spontaneous reduction of the quantum state. The theories of this kind, which were developed in order to address the so called “measurement problem” in quantum theory have, in the past, been framed in a non-relativistic setting and in that form they were previously applied to the black hole information problem. Here, and for the first time, we show in a simple toy model, a treatment of the problem within a fully relativistic setting. We also discuss the issues that the present analysis leaves as open problems to be dealt with in future refinements of the present approach.

Spacetime Quanta? : Real Discrete Spectrum of a Quantum Spacetime Four-Volume Operator in Unimodular Loop Quantum Cosmology. (arXiv:1604.06584v1 [gr-qc])

on 2016-4-25 12:06pm GMT

Authors: Joseph Bunao

This study considers the operator $\hat{T}$ corresponding to the classical spacetime four-volume $T$ of a finite patch of spacetime in the context of Unimodular Loop Quantum Cosmology for the homogeneous and isotropic model with flat spatial sections and without matter sources. Since $T$ is canonically conjugate to the cosmological “constant” $\Lambda$, the operator $\hat{T}$ is constructed by solving its canonical commutation relation with $\hat{\Lambda}$ – the operator corresponding to $\Lambda$. %This is done by expanding $\hat{T}$ in terms of Bender-Dunne-like basis operators $\hat{T}_{m,n}$ and solving for the expansion coefficients. This conjugacy, along with the action of $\hat{T}$ on definite volume states reducing to $T$, allows us to interpret that $\hat{T}$ is indeed a quantum spacetime four-volume operator. The eigenstates $\Phi_{\tau}$ are calculated and, considering $\tau\in\mathbb{R}$, we find that the $\Phi_{\tau}$’s are normalizable suggesting that the real line $\mathbb{R}$ is in the discrete spectrum of $\hat{T}$. The real spacetime four-volume $\tau$ is then discrete or quantized.

Is General Relativity a (partial) Return of Aristotelian Physics?. (arXiv:1604.06491v1 [physics.hist-ph])

on 2016-4-25 12:06pm GMT

Authors: Herbert Pietschmann

Aristotle has split physics at the sphere of the moon; above this sphere there is no change except eternal spherical motion, below are two different kinds of motion: Natural motion (without specific cause) and enforced motion. In modern view motion is caused by gravity and by other forces. The split at the sphere of the moon has been definitely overcome through the observation of a supernova and several comets by Tycho Brahe. The second distinction was eradicated by Isaak Newton who showed that gravitational motion was caused by a force proportional to the inverse square of the distance. By the theory of General Relativity, Albert Einstein showed that there is no gravitational force but motion under gravity (i.e. Aristotles <natural motion>) is caused by the curved geometry of spacetime. In this way, the Aristotelian distinction between natural motion and enforced motion has come back in the form of two great theories: General Relativity and Quantum Field Theory which are today incompatible. To find a way out of this dilemma is the challenge of modern physics.

Free Will – A road less travelled in quantum information. (arXiv:1604.06489v1 [physics.hist-ph])

on 2016-4-25 12:06pm GMT

Authors: Ilyas Khan

Conway and Kochen’s Free Will Theory is examined as an important foundational element in a new area of activity in computer science – developing protocols for quantum computing

Irreversibility in physics stemming from unpredictable symbol-handling agents. (arXiv:1604.06771v1 [quant-ph])

on 2016-4-25 12:06pm GMT

The basic equations of physics involve a time variable t and are invariant under the transformation $t goes to -t$. This invariance at first sight appears to impose time reversibility as a principle of physics, in conflict with thermodynamics. But equations written on the blackboard are not the whole story in physics. In prior work we sharpened a distinction obscured in today’s theoretical physics, the distinction between obtaining evidence from experiments on the laboratory bench and explaining that evidence in mathematical symbols on the blackboard. The sharp distinction rests on a proof within the mathematics of quantum theory that no amount of evidence, represented in quantum theory in terms of probabilities, can uniquely determine its explanation in terms of wave functions and linear operators. Building on the proof we show here a role in physics for unpredictable symbol-handling agents acting both at the blackboard and at the workbench, communicating back and forth by means of transmitted symbols. Because of their unpredictability, symbol-handling agents introduce a heretofore overlooked source of irreversibility into physics, even when the equations they write on the blackboard are invariant under t goes to -t\$. Widening the scope of descriptions admissible to physics to include the agents and the symbols that link theory to experiments opens up a new source of time-irreversibility in physics.

Uncertain for A Century: Quantum Mechanics and The Dilemma of Interpretation. (arXiv:1604.06488v1 [physics.hist-ph])

on 2016-4-25 12:06pm GMT

Quantum Mechanics, the physical theory describing the microworld, represents one of science’s greatest triumphs. It lies at the root of all modern digital technologies and offers unparalleled correspondence between prediction and experiments. Remarkably, however, after more than 100 years it is still unclear what quantum mechanics means in terms of basic philosophical questions about the nature of reality. While there are many interpretations of the mathematical machinery of quantum physics, there remains no experimental means to distinguish between most of them.

In this contribution, (based on a discussion at the NYAS), I wish to consider the ways in which the enduring lack of an agreed upon interpretation of quantum physics influences a number of critical philosophical debates about physics and reality. I briefly review two problems effected by quantum interpretations: the meaning of the term ‘Universe’ and the nature of consciousness. In what follows I am explicitly not advocating for any particular quantum interpretation. Instead, I am interested in how the explicit inability of modern physics to experimentally distinguish between interpretations with wildly divergent ontological/epistemological implications plays into discussions of physics and its description of the world.

arXiv:1604.02836 [pdfpsother]

Symmetry and the Relativity of States and Observables in Quantum Mechanics

Kazuya Okamura and Masanao Ozawa, Measurement Theory in Local Quantum Physics, Journal of Mathematical Physics 57 (1), 015209/1-015209/29 (2016).

[Special Issue: Operator Algebras and Quantum Information Theory]

http://dx.doi.org/10.1063/1.4935407

arXiv:1510.02063 [pdfpsother]

Approximating relational observables by absolute quantities: A quantum accuracy-size trade-off