Authors: Job Feldbrugge, Jean-Luc Lehners, Neil Turok

We identify a fundamental obstruction to any theory of the beginning of the universe, formulated as a semiclassical path integral. Hartle and Hawking's no boundary proposal and Vilenkin's tunneling proposal are examples of such theories. Each may be formulated as the quantum amplitude for obtaining a final 3-geometry by integrating over 4-geometries. We introduce a new mathematical tool - Picard-Lefschetz theory - for defining the semiclassical path integral for gravity. The Lorentzian path integral for quantum cosmology with a positive cosmological constant is meaningful in this approach, but the Euclidean version is not. Framed in this way, the resulting framework and predictions are unique. Unfortunately, the outcome is that primordial tensor (gravitational wave) fluctuations are unsuppressed. We prove a general theorem to this effect, in a wide class of theories.

# The Algebra of the Pseudo-Observables II: The Measurement Problem. (arXiv:1708.01170v1 [quant-ph] CROSS LISTED)

## physics.hist-ph updates on arXiv.org

Authors: Edoardo Piparo

In this second paper, we develop the full mathematical structure of the algebra of the pseudo-observables, in order to solve the quantum measurement problem. Quantum state vectors are recovered but as auxiliary pseudo-observables storing the information acquired in a set of observations. The whole process of measurement is deeply reanalyzed in the conclusive section, evidencing original aspects. The relation of the theory with some popular interpretations of Quantum Mechanics is also discussed, showing that both Relational Quantum Mechanics and Quantum Bayesianism may be regarded as compatible interpretations of the theory. A final discussion on reality, tries to bring a new insight on it.

# The Algebra of the Pseudo-Observables I: Why Quantum Mechanics is the ultimate description of Reality. (arXiv:1707.05633v3 [quant-ph] CROSS LISTED)

## physics.hist-ph updates on arXiv.org

Authors: Edoardo Piparo (Ministero dell'Istruzione dell'Università e della Ricerca)

This paper is the first of several parts introducing a new powerful algebra: the algebra of the pseudo-observables. This is a C*-algebra whose set is formed by formal expressions involving observables. The algebra is constructed by applying the Occam's razor principle, in order to obtain the minimal description of physical reality. Proceeding in such a manner, every aspect of quantum mechanics acquires a clear physical interpretation or a logical explanation, providing, for instance, in a natural way the reason for the structure of complex algebra and the matrix structure of Werner Heisenberg's formulation of quantum mechanics. Last but not least, the very general hypotheses assumed, allow one to state that quantum mechanics is the unique minimal description of physical reality.

Authors: Job Feldbrugge, Jean-Luc Lehners, Neil Turok

In recent work, we introduced Picard-Lefschetz theory as a tool for defining the Lorentzian path integral for quantum gravity in a systematic semiclassical expansion. This formulation avoids several pitfalls occurring in the Euclidean approach. Our method provides, in particular, a more precise formulation of the Hartle-Hawking no boundary proposal, as a sum over real Lorentzian four-geometries interpolating between an initial three-geometry of zero size, {\it i.e}, a point, and a final three-geometry. With this definition, we calculated the no boundary amplitude for a closed universe with a cosmological constant, assuming cosmological symmetry for the background and including linear perturbations. We found the opposite semiclassical exponent to that obtained by Hartle and Hawking for the creation of a de Sitter spacetime "from nothing". Furthermore, we found the linearized perturbations to be governed by an {\it inverse} Gaussian distribution, meaning they are unsuppressed and out of control. Recently, Diaz Dorronsoro {\it et al.} followed our methods but attempted to rescue the no boundary proposal by integrating the lapse over a different, intrinsically complex contour. Here, we show that, in addition to the desired Hartle-Hawking saddle point contribution, their contour yields extra, non-perturbative corrections which again render the perturbations unsuppressed. We prove there is {\it no} choice of complex contour for the lapse which avoids this problem. We extend our discussion to include backreaction in the leading semiclassical approximation, fully nonlinearly for the lowest tensor harmonic and to second order for all higher modes. Implications for quantum de Sitter spacetime and for cosmic inflation are briefly discussed.

# On the thermodynamic implications of path integral formalism of quantum mechanics. (arXiv:1708.05113v1 [cond-mat.stat-mech])

## quant-ph updates on arXiv.org

Authors: Ken Funo, H. T. Quan

By introducing novel concepts of work and heat functionals along individual $"$path$"$, we reformulate quantum Jarzynski equality based on the path integral formulation of quantum mechanics. When applied to an open quantum system described by the quantum Brownian motion model, we establish a consistent framework of quantum thermodynamics in the strong coupling regime. Using the work and heat functionals, we derive a path-integral expression for the work and heat statistics. This formalism provides an effective way to calculate the work and heat in open quantum systems by utilizing various path integral techniques. By performing the $\hbar$ expansion, we analytically prove the quantum-classical correspondence of the work and heat statistics. In addition, we obtain the $n$-th order quantum correction to the classical work.

# Complementarity, wave-particle duality, and domains of applicability

## ScienceDirect Publication: Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics

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

Author(s): Peter Bokulich

Complementarity has frequently, but mistakenly, been conflated with wave-particle duality, and this conflation has led to pervasive misunderstandings of Bohr's views and several misguided claims of an experimental “disproof” of complementarity. In this paper, I explain what Bohr meant by complementarity, and how this is related to, but distinct from, wave-particle duality. I list a variety of possible meanings of wave-particle duality, and canvass the ways in which they are (or are not) supported by quantum physics and Bohr's interpretation. I also examine the extent to which wave-particle duality should be viewed as an example of the sort of dualities one finds in, e.g., string theory. I argue that the most fruitful way of reading of Bohr's account complementarity is by comparing it to current accounts of effective theories with limited domains of applicability.

# Analysis of the Jun Ishiwara's "The universal meaning of the quantum of action". (arXiv:1708.04676v1 [physics.hist-ph])

## physics.hist-ph updates on arXiv.org

Authors: Karla Pelogia, Carlos Alexandre Brasil

Here we present an analysis of the paper "Universelle Bedeutung des Wirkungsquantums" (The universal meaning of the quantum of action), published by Jun Ishiwara in German in the "Proceedings of Tokyo Mathematico-Physical Society 8 (1915) 106-116". In his work, Ishiwara, established in the Sendai University, Japan, proposed - simultaneously with Arnold Sommerfeld, William Wilson and Niels Bohr in Europe - the phase-space-integral quantization, a rule that would be incorporated into the old-quantum-theory formalism. The discussions and analysis render this paper fully accessible to undergraduate students of physics with elementary knowledge of quantum mechanics.

# Non-interferometric test of the Continuous Spontaneous Localization model based on the torsional motion of a cylinder. (arXiv:1708.04812v1 [quant-ph])

## quant-ph updates on arXiv.org

Authors: Matteo Carlesso, Mauro Paternostro, Hendrik Ulbricht, Andrea Vinante, Angelo Bassi

The Continuous Spontaneous Localization (CSL) model is the best known and studied among collapse models, which modify quantum mechanics and identify the fundamental reasons behind the unobservability of quantum superpositions at the macroscopic scale. Albeit several tests were performed during the last decade, up to date the CSL parameter space still exhibits a vast unexplored region. Here, we study and propose an unattempted non-interferometric test aimed to fill this gap. We show that the angular momentum diffusion predicted by CSL heavily constrains the parametric values of the model when applied to a macroscopic cylinder, eventually allowing to cover the unexplored region of the parameter space.

# Quantum bit commitment and the reality of the quantum state. (arXiv:1708.04964v1 [quant-ph])

## quant-ph updates on arXiv.org

Authors: R. Srikanth

Quantum bit commitment (QBC) is insecure in the standard non-relativistic quantum cryptographic framework, essentially because Alice can exploit quantum steering to defer making her commitment. Two assumptions implicit in this framework are that: (a) the same system $E$ would be used for submitting the evidence for either commitment (That is, only the commitment-encoding states are different-- but not the submitted system itself-- for different commitments); and (b) system $E$ is quantum rather than classical. Here, we show how relaxing assumption (a) or (b) can render her malicious steering operation indeterminable or inexistent, respectively. Finally, we present a secure protocol that relaxes both assumptions in a quantum teleportation setting. Without appeal to an ontological framework, we argue that the protocol's security entails the reality of the quantum state, provided retrocausality is excluded.

# From statistical proofs of the Kochen-Specker theorem to noise-robust noncontextuality inequalities. (arXiv:1708.04793v1 [quant-ph])

## quant-ph updates on arXiv.org

Authors: Ravi Kunjwal, Robert W. Spekkens

The Kochen-Specker theorem rules out models of quantum theory wherein sharp measurements are assigned outcomes deterministically and independently of context. This notion of noncontextuality is not applicable to experimental measurements because these are never free of noise and thus never truly sharp. For unsharp measurements, therefore, one must drop the requirement that an outcome is assigned deterministically in the model and merely require that the distribution over outcomes that is assigned in the model is context-independent. By demanding context-independence in the representation of preparations as well, one obtains a generalized principle of noncontextuality that also supports a quantum no-go theorem. Several recent works have shown how to derive inequalities on experimental data which, if violated, demonstrate the impossibility of finding a generalized-noncontextual model of this data. That is, these inequalities do not presume quantum theory and, in particular, they make sense without requiring a notion of "sharpness" of measurements in any operational theory describing the experiment. We here describe a technique for deriving such inequalities starting from arbitrary proofs of the Kochen-Specker theorem. It extends significantly previous techniques, which worked only for logical proofs (based on uncolourable orthogonality graphs), to the case of statistical proofs (where the graphs are colourable, but the colourings cannot explain the quantum statistics). The derived inequalities are robust to noise.

# Analysis of the Jun Ishiwara's "The universal meaning of the quantum of action". (arXiv:1708.04676v1 [physics.hist-ph])

## quant-ph updates on arXiv.org

Authors: Karla Pelogia, Carlos Alexandre Brasil

Here we present an analysis of the paper "Universelle Bedeutung des Wirkungsquantums" (The universal meaning of the quantum of action), published by Jun Ishiwara in German in the "Proceedings of Tokyo Mathematico-Physical Society 8 (1915) 106-116". In his work, Ishiwara, established in the Sendai University, Japan, proposed - simultaneously with Arnold Sommerfeld, William Wilson and Niels Bohr in Europe - the phase-space-integral quantization, a rule that would be incorporated into the old-quantum-theory formalism. The discussions and analysis render this paper fully accessible to undergraduate students of physics with elementary knowledge of quantum mechanics.

# Quantum mechanics with space-time noncommutativity. (arXiv:1708.04769v1 [quant-ph])

## quant-ph updates on arXiv.org

Authors: Partha Nandi, Sayan Kumar Pal, Aritra N Bose, Biswajit Chakraborty

We construct an effective commutative Schr\"odinger equation in Moyal space-time in $(1+1)$-dimension where both $t$ and $x$ are operator-valued and satisfy $\left[ \hat{t}, \hat{x} \right] = i \theta$. Beginning with a time-reparametrised form of an action we identify the actions of various space-time coordinates and their conjugate momenta on quantum states, represented by Hilbert-Schmidt operators. Since time is also regarded as a configuration space variable, we show how an `induced' inner product can be extracted, so that an appropriate quantum mechanical interpretation is obtained. We then discuss several other applications of the formalism developed so far.

# Conservation, Inertia, and Spacetime Geometry

## Philsci-Archive: No conditions. Results ordered -Date Deposited.

# Notes on microstates, Tsallis statistics and entropic gravity formalism. (arXiv:1708.04596v1 [hep-th])

## gr-qc updates on arXiv.org

Authors: Everton M. C. Abreu, Jorge Ananias Neto, Albert C. R. Mendes, Daniel O. Souza

It is an old idea to realize Einstein's equations as a thermodynamical equation of state. Since then, there has been new conjectures to understand gravity from another point of view. In this way we can accept that the gravitational field is not an underlying one like an emergent force from other approaches based on the knowledge of relativity, quantum and black holes thermodynamics, and different statistical formalisms. One important question concerning this gravity/thermostatistics correspondence is whether the holographic screen could be well defined for a nonrelativistic case of a source mass. Hence, to understand the actual role of the holographic screen is a very relevant issue. In this letter we have analyzed the entropy as a function of the holographic screen in some different scenarios. We have disclosed modified Newtonian dynamics (MOND) from Verlinde's ideas. Besides, we have calculated some cosmological elements using the same ideas. The results obtained using MOND will guide us to obtain other cosmological results.

# A conjecture concerning determinism, reduction, and measurement in quantum mechanics. (arXiv:1204.0614v6 [quant-ph] UPDATED)

## physics.hist-ph updates on arXiv.org

Authors: Arthur Jabs

Determinism is established in quantum mechanics by tracing the probabilities in the Born rules back to the absolute (overall) phase constants of the wave functions and recognizing these phase constants as pseudorandom numbers. The reduction process (collapse) is independent of measurement. It occurs when two wavepackets overlap in ordinary space and satisfy a certain criterion, which depends on the phase constants of both wavepackets. Reduction means contraction of the wavepackets to the place of overlap. A measurement apparatus always fans out the incoming wavepacket into spatially separated eigenpackets of the chosen observable. When one of these eigenpackets together with a wavepacket in the apparatus satisfy the criterion, the reduction associates the place of contraction with an eigenvalue of the observable. The theory is nonlocal and contextual.

ISBN: 9780198714057

Binding: Hardcover

Publication Date: 15 August 2017

Price: $45.00

# Salecker-Wigner-Peres clock, Feynman paths, and a tunneling time that should not exist

## PRA: Fundamental concepts

Author(s): D. Sokolovski

The Salecker-Wigner-Peres (SWP) clock is often used to determine the duration a quantum particle is supposed to spend in a specified region of space Ω. By construction, the result is a real positive number, and the method seems to avoid the difficulty of introducing complex time parameters, which ar...

[Phys. Rev. A 96, 022120] Published Mon Aug 14, 2017

# Including temperature in a wavefunction description of the dynamics of the quantum Rabi model. (arXiv:1708.03460v1 [quant-ph])

## quant-ph updates on arXiv.org

Authors: Michael Werther, Frank Grossmann

We present a wavefunction methodology to account for finite temperature initial conditions in the quantum Rabi model. The approach is based on the Davydov-Ansatz together with a statistical sampling of the canonical harmonic oscillator initial density matrix. Equations of motion are gained from a variational principle and numerical results are compared to those of the thermal Hamiltonian approach. For a system consisting of a single spin and a single oscillator and for moderate coupling strength, we compare our new results with full quantum ones as well as with other Davydov-type results based on alternative sampling/summation strategies. All of these perform better than the ones based on the thermal Hamiltonian approach. The best agreement is shown by a Boltzmann weighting of individual eigenstate propagations. Extending this to a bath of many oscillators will, however, be very demanding numerically. The use of any one of the investigated stochastic sampling approaches will then be favorable.

# Multi-Time Wave Functions versus Multiple Timelike Dimensions. (arXiv:1708.03376v1 [quant-ph])

## quant-ph updates on arXiv.org

Authors: Matthias Lienert, Sören Petrat, Roderich Tumulka

Multi-time wave functions are wave functions for multi-particle quantum systems that involve several time variables (one per particle). In this paper we contrast them with solutions of wave equations on a space-time with multiple timelike dimensions, i.e., on a pseudo-Riemannian manifold whose metric has signature such as ${+}{+}{-}{-}$ or ${+}{+}{-}{-}{-}{-}{-}{-}$, instead of ${+}{-}{-}{-}$. Despite the superficial similarity, the two behave very differently: Whereas wave equations in multiple timelike dimensions are typically mathematically ill-posed and presumably unphysical, relevant Schr\"odinger equations for multi-time wave functions possess for every initial datum a unique solution on the spacelike configurations and form a natural covariant representation of quantum states.

Nature Physics. doi:10.1038/nphys4239

Author: Spencer R. Klein

The ATLAS Collaboration observed photons elastically scattering from other photons — an effect predicted by quantum electrodynamics over 80 years ago.

# Determining the quantum expectation value by measuring a single photon

## Nature Physics - AOP - nature.com science feeds

Nature Physics. doi:10.1038/nphys4223

Authors: Fabrizio Piacentini, Alessio Avella, Enrico Rebufello, Rudi Lussana, Federica Villa, Alberto Tosi, Marco Gramegna, Giorgio Brida, Eliahu Cohen, Lev Vaidman, Ivo P. Degiovanni & Marco Genovese

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