Weekly Papers on Quantum Foundations (49)

Authors: Ning BaoSean M. CarrollAidan Chatwin-DaviesJason PollackGrant N. Remmen

We discuss the branching structure of the quantum-gravitational wave function that describes the evaporation of a black hole. A global wave function that initially describes a classical Schwarzschild geometry is continually decohered into distinct semiclassical branches by the emission of Hawking radiation. The laws of quantum mechanics dictate that the wave function evolves unitarily, but this unitary evolution is only manifest when considering the global description of the wave function: it is not implemented by time evolution on a single semiclassical branch. Conversely, geometric notions like the position or smoothness of a horizon only make sense on the level of individual branches. We consider the implications of this picture for probes of black holes by classical observers in definite geometries, like those involved in the AMPS construction. We argue that individual branches can describe semiclassical geometries free of firewalls, even as the global wave function evolves unitarily. We show that the pointer states of infalling detectors that are robust under Hamiltonian evolution are distinct from, and incompatible with, those of exterior detectors stationary with respect to the black hole horizon, in the sense that the pointer bases are related to each other via nontrivial transformations that mix system, apparatus, and environment. This result describes a Hilbert-space version of black hole complementarity.

Chen, Eddy Keming (2017) Time’s Arrow in a Quantum Universe I: On the Simplicity and Uniqueness of the Initial Quantum State. [Preprint]
Weatherall, James Owen (2015) Understanding Gauge. [Preprint]

Authors: Lee Smolin

A proposal is made for a fundamental theory, in which the history of the universe is constituted of diverse views of itself. Views are attributes of events, and the theory’s only be-ables; they comprise information about energy and momentum transferred to an event from its causal past. A dynamics is proposed for a universe constituted of views of events, which combines the energetic causal set dynamics with a potential energy based on a measure of the distinctiveness of the views, called the variety. As in the real ensemble formulation of quantum mechanics, quantum pure states are associated to ensembles of similar events; the quantum potential of Bohm then arises from the variety.

Authors: Yongwan GimHwajin UmWontae Kim

When gravitation is combined with quantum theory, the Heisenberg uncertainty principle could be extended to the generalized uncertainty principle accompanying a minimal length. To see how the generalized uncertainty principle works in the context of black hole complementary, we calculate the required energy to duplicate information for the Schwarzschild black hole. It shows that the duplication of information is not allowed and black hole complementarity is still valid even assuming the generalized uncertainty principle. On the other hand, the generalized uncertainty principle with the minimal length could lead to a modification of the conventional dispersion relation in light of Gravity’s Rainbow where the minimal length is also invariant as well as the speed of light. Revisiting the gedanken experiment, we show that the no-cloning theorem for black hole complementarity can be made valid in the regime of Gravity’s Rainbow on a certain combination of parameters.

Authors: Przemysław MałkiewiczArtur MiroszewskiHervé Bergeron

We develop a phase space formulation of quantum mechanics based on unitary irreducible representations of classical phase spaces. We use a quantum action functional to derive the basic equations. In principle, our formulation is equivalent to the Hilbert space formulation. However, the former allows for consistent truncations to reduced phase spaces in which approximate quantum motions can be derived. We predict that our approach can be very useful in the domain of quantum cosmology and therefore, we use the cosmological phase spaces to establish the basic equations of the new formalism.

Chen, Eddy Keming (2017) An Intrinsic Theory of Quantum Mechanics: Progress in Field’s Nominalistic Program, Part I. [Preprint]

Author(s): C. Marletto and V. Vedral

Two proposals describe how to test whether gravity is inherently quantum by measuring the entanglement between two masses.


[Phys. Rev. Lett. 119, 240402] Published Wed Dec 13, 2017

Author(s): Sougato Bose, Anupam Mazumdar, Gavin W. Morley, Hendrik Ulbricht, Marko Toroš, Mauro Paternostro, Andrew A. Geraci, Peter F. Barker, M. S. Kim, and Gerard Milburn

Two proposals describe how to test whether gravity is inherently quantum by measuring the entanglement between two masses.


[Phys. Rev. Lett. 119, 240401] Published Wed Dec 13, 2017

Author(s): Sougato Bose, Anupam Mazumdar, Gavin W. Morley, Hendrik Ulbricht, Marko Toroš, Mauro Paternostro, Andrew A. Geraci, Peter F. Barker, M. S. Kim, and Gerard Milburn

Two proposals describe how to test whether gravity is inherently quantum by measuring the entanglement between two masses.


[Phys. Rev. Lett. 119, 240401] Published Wed Dec 13, 2017

Author(s): C. Marletto and V. Vedral

Two proposals describe how to test whether gravity is inherently quantum by measuring the entanglement between two masses.


[Phys. Rev. Lett. 119, 240402] Published Wed Dec 13, 2017

Abstract

This paper presents a realistic, stochastic, and local model that reproduces nonrelativistic quantum mechanics (QM) results without using its mathematical formulation. The proposed model only uses integer-valued quantities and operations on probabilities, in particular assuming a discrete spacetime under the form of a Euclidean lattice. Individual (spinless) particle trajectories are described as random walks. Transition probabilities are simple functions of a few quantities that are either randomly associated to the particles during their preparation, or stored in the lattice nodes they visit during the walk. QM predictions are retrieved as probability distributions of similarly-prepared ensembles of particles. The scenarios considered to assess the model comprise of free particle, constant external force, harmonic oscillator, particle in a box, the Delta potential, particle on a ring, particle on a sphere and include quantization of energy levels and angular momentum, as well as momentum entanglement.

Myrvold, Wayne C. (2017) Relativistically Invariant Markovian Dynamical Collapse Theories Must Employ Nonstandard Degrees of Freedom. Physical Review A, 96 (6). 062116.
de Ronde, Christian and Fernandez Moujan, Ramiro (2017) Epistemological vs. Ontological Relationalism in Quantum Mechanics: Relativism or Realism? [Preprint]

Quantum violation of an instrumental test

Quantum violation of an instrumental test, Published online: 11 December 2017; doi:10.1038/s41567-017-0008-5

Theory and experiment show that quantum correlations violate the instrumental test—a common statistical method used to estimate the strength of causal relationships between two variables.

Le Bihan, Baptiste (2018) Priority Monism Beyond Spacetime. [Preprint]
Esfeld, Michael (2017) Individuality and the account of non-locality: the case for the particle ontology in quantum physics. [Preprint]

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