Quantum Communications, Relativistic Entanglement and the Theory of Dilated Locality Mario Mastriani
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Yes, More Decoherence: a Reply to Critics
Yes, More Decoherence: A Reply to Critics Elise M. Crull∗ Submitted 11 July 2017; revised 24 August 2017 1 Introduction A few years ago I published an article in this journal titled \Less interpretation and more decoherence in quantum gravity and inflationary cosmology" (Crull, 2015) that generated replies from three pairs of authors: Vassallo and Esfeld (2015), Okon and Sudarsky (2016) and Fortin and Lombardi (2017). As a philosopher of physics it is my chief aim to engage physicists and philosophers alike in deeper conversation regarding scientific theories and their implications. In as much as my earlier paper provoked a suite of responses and thereby brought into sharper relief numerous misconceptions regarding decoherence, I welcome the occasion provided by the editors of this journal to continue the discussion. In what follows, I respond to my critics in some detail (wherein the devil is often found). I must be clear at the outset, however, that due to the nature of these criticisms, much of what I say below can be categorized as one or both of the following: (a) a repetition of points made in the original paper, and (b) a reiteration of formal and dynamical aspects of quantum decoherence considered uncontroversial by experts working on theoretical and experimental applications of this process.1 I begin with a few paragraphs describing what my 2015 paper both was, and was not, about. I then briefly address Vassallo's and Esfeld's (hereafter VE) relatively short response to me, dedicating the bulk of my reply to the lengthy critique of Okon and Sudarsky (hereafter OS). -
Sudden Death and Revival of Gaussian Einstein–Podolsky–Rosen Steering
www.nature.com/npjqi ARTICLE OPEN Sudden death and revival of Gaussian Einstein–Podolsky–Rosen steering in noisy channels ✉ Xiaowei Deng1,2,4, Yang Liu1,2,4, Meihong Wang2,3, Xiaolong Su 2,3 and Kunchi Peng2,3 Einstein–Podolsky–Rosen (EPR) steering is a useful resource for secure quantum information tasks. It is crucial to investigate the effect of inevitable loss and noise in quantum channels on EPR steering. We analyze and experimentally demonstrate the influence of purity of quantum states and excess noise on Gaussian EPR steering by distributing a two-mode squeezed state through lossy and noisy channels, respectively. We show that the impurity of state never leads to sudden death of Gaussian EPR steering, but the noise in quantum channel can. Then we revive the disappeared Gaussian EPR steering by establishing a correlated noisy channel. Different from entanglement, the sudden death and revival of Gaussian EPR steering are directional. Our result confirms that EPR steering criteria proposed by Reid and I. Kogias et al. are equivalent in our case. The presented results pave way for asymmetric quantum information processing exploiting Gaussian EPR steering in noisy environment. npj Quantum Information (2021) 7:65 ; https://doi.org/10.1038/s41534-021-00399-x INTRODUCTION teleportation30–32, securing quantum networking tasks33, and 1234567890():,; 34,35 Nonlocality, which challenges our comprehension and intuition subchannel discrimination . about the nature, is a key and distinctive feature of quantum Besides two-mode EPR steering, the multipartite EPR steering world. Three different types of nonlocal correlations: Bell has also been widely investigated since it has potential application nonlocality1, Einstein–Podolsky–Rosen (EPR) steering2–6, and in quantum network. -
Quantum Cryptography: from Theory to Practice
Quantum cryptography: from theory to practice by Xiongfeng Ma A thesis submitted in conformity with the requirements for the degree of Doctor of Philosophy Thesis Graduate Department of Department of Physics University of Toronto Copyright °c 2008 by Xiongfeng Ma Abstract Quantum cryptography: from theory to practice Xiongfeng Ma Doctor of Philosophy Thesis Graduate Department of Department of Physics University of Toronto 2008 Quantum cryptography or quantum key distribution (QKD) applies fundamental laws of quantum physics to guarantee secure communication. The security of quantum cryptog- raphy was proven in the last decade. Many security analyses are based on the assumption that QKD system components are idealized. In practice, inevitable device imperfections may compromise security unless these imperfections are well investigated. A highly attenuated laser pulse which gives a weak coherent state is widely used in QKD experiments. A weak coherent state has multi-photon components, which opens up a security loophole to the sophisticated eavesdropper. With a small adjustment of the hardware, we will prove that the decoy state method can close this loophole and substantially improve the QKD performance. We also propose a few practical decoy state protocols, study statistical fluctuations and perform experimental demonstrations. Moreover, we will apply the methods from entanglement distillation protocols based on two-way classical communication to improve the decoy state QKD performance. Fur- thermore, we study the decoy state methods for other single photon sources, such as triggering parametric down-conversion (PDC) source. Note that our work, decoy state protocol, has attracted a lot of scienti¯c and media interest. The decoy state QKD becomes a standard technique for prepare-and-measure QKD schemes. -
Monday O. Gühne 9:00 – 9:45 Quantum Steering and the Geometry of the EPR-Argument Steering Is a Type of Quantum Correlations
Monday O. Gühne Quantum Steering and the Geometry of the EPR-Argument 9:00 – 9:45 Steering is a type of quantum correlations which lies between entanglement and the violation of Bell inequalities. In this talk, I will first give an introduction into the topic. Then, I will discuss two results on steering: First, I will show how entropic uncertainty relations can be used to derive steering criteria. Second, I will present an algorithmic approach to characterize the quantum states that can be used for steering. With this, one can decide the problem of steerability for two-qubit states. [1] A.C.S. Costa et al., arXiv:1710.04541. [2] C. Nguyen et al., arXiv:1808.09349. J.-Å. Larsson Quantum computation and the additional degrees of freedom in a physical 9:45 – 10:30 system The speed-up of Quantum Computers is the current drive of an entire scientific field with several large research programmes both in industry and academia world-wide. Many of these programmes are intended to build hardware for quantum computers. A related important goal is to understand the reason for quantum computational speed- up; to understand what resources are provided by the quantum system used in quantum computation. Some candidates for such resources include superposition and interference, entanglement, nonlocality, contextuality, and the continuity of state- space. The standard approach to these issues is to restrict quantum mechanics and characterize the resources needed to restore the advantage. Our approach is dual to that, instead extending a classical information processing systems with additional properties in the form of additional degrees of freedom, normally only present in quantum-mechanical systems. -
Arxiv:1607.01025V2
Observables, gravitational dressing, and obstructions to locality and subsystems William Donnelly∗ and Steven B. Giddings† Department of Physics, University of California, Santa Barbara, CA 93106 Quantum field theory – our basic framework for describing all nongravitational physics – conflicts with general relativity: the latter precludes the standard definition of the former’s essential principle of locality, in terms of commuting local observables. We examine this conflict more carefully, by investigating implications of gauge (diffeomorphism) invariance for observables in gravity. We prove a dressing theorem, showing that any operator with nonzero Poincar´echarges, and in particular any compactly supported operator, in flat-spacetime quantum field theory must be gravitationally dressed once coupled to gravity, i.e. it must depend on the metric at arbitrarily long distances, and we put lower bounds on this nonlocal dependence. This departure from standard locality occurs in the most severe way possible: in perturbation theory about flat spacetime, at leading order in Newton’s constant. The physical observables in a gravitational theory therefore do not organize themselves into local commuting subalgebras: the principle of locality must apparently be reformulated or abandoned, and in fact we lack a clear definition of the coarser and more basic notion of a quantum subsystem of the Universe. We discuss relational approaches to locality based on diffeomorphism-invariant nonlocal operators, and reinforce arguments that any such locality is state-dependent and approximate. We also find limitations to the utility of bilocal diffeomorphism- invariant operators that are considered in cosmological contexts. An appendix provides a concise review of the canonical covariant formalism for gravity, instrumental in the discussion of Poincar´e charges and their associated long-range fields. -
Many Physicists Believe That Entanglement Is The
NEWS FEATURE SPACE. TIME. ENTANGLEMENT. n early 2009, determined to make the most annual essay contest run by the Gravity Many physicists believe of his first sabbatical from teaching, Mark Research Foundation in Wellesley, Massachu- Van Raamsdonk decided to tackle one of setts. Not only did he win first prize, but he also that entanglement is Ithe deepest mysteries in physics: the relation- got to savour a particularly satisfying irony: the the essence of quantum ship between quantum mechanics and gravity. honour included guaranteed publication in After a year of work and consultation with col- General Relativity and Gravitation. The journal PICTURES PARAMOUNT weirdness — and some now leagues, he submitted a paper on the topic to published the shorter essay1 in June 2010. suspect that it may also be the Journal of High Energy Physics. Still, the editors had good reason to be BROS. ENTERTAINMENT/ WARNER In April 2010, the journal sent him a rejec- cautious. A successful unification of quantum the essence of space-time. tion — with a referee’s report implying that mechanics and gravity has eluded physicists Van Raamsdonk, a physicist at the University of for nearly a century. Quantum mechanics gov- British Columbia in Vancouver, was a crackpot. erns the world of the small — the weird realm His next submission, to General Relativity in which an atom or particle can be in many BY RON COWEN and Gravitation, fared little better: the referee’s places at the same time, and can simultaneously report was scathing, and the journal’s editor spin both clockwise and anticlockwise. Gravity asked for a complete rewrite. -
A Non-Technical Explanation of the Bell Inequality Eliminated by EPR Analysis Eliminated by Bell A
Ghostly action at a distance: a non-technical explanation of the Bell inequality Mark G. Alford Physics Department, Washington University, Saint Louis, MO 63130, USA (Dated: 16 Jan 2016) We give a simple non-mathematical explanation of Bell's inequality. Using the inequality, we show how the results of Einstein-Podolsky-Rosen (EPR) experiments violate the principle of strong locality, also known as local causality. This indicates, given some reasonable-sounding assumptions, that some sort of faster-than-light influence is present in nature. We discuss the implications, emphasizing the relationship between EPR and the Principle of Relativity, the distinction between causal influences and signals, and the tension between EPR and determinism. I. INTRODUCTION II. OVERVIEW To make it clear how EPR experiments falsify the prin- The recent announcement of a \loophole-free" observa- ciple of strong locality, we now give an overview of the tion of violation of the Bell inequality [1] has brought re- logical context (Fig. 1). For pedagogical purposes it is newed attention to the Einstein-Podolsky-Rosen (EPR) natural to present the analysis of the experimental re- family of experiments in which such violation is observed. sults in two stages, which we will call the \EPR analy- The violation of the Bell inequality is often described as sis", and the \Bell analysis" although historically they falsifying the combination of \locality" and \realism". were not presented in exactly this form [4, 5]; indeed, However, we will follow the approach of other authors both stages are combined in Bell's 1976 paper [2]. including Bell [2{4] who emphasize that the EPR results We will concentrate on Bohm's variant of EPR, the violate a single principle, strong locality. -
It Is a Great Pleasure to Write This Letter on Behalf of Dr. Maria
Rigorous Quantum-Classical Path Integral Formulation of Real-Time Dynamics Nancy Makri Departments of Chemistry and Physics University of Illinois The path integral formulation of time-dependent quantum mechanics provides the ideal framework for rigorous quantum-classical or quantum-semiclassical treatments, as the spatially localized, trajectory-like nature of the quantum paths circumvents the need for mean-field-type assumptions. However, the number of system paths grows exponentially with the number of propagation steps. In addition, each path of the quantum system generally gives rise to a distinct classical solvent trajectory. This exponential proliferation of trajectories with propagation time is the quantum-classical manifestation of nonlocality. A rigorous real-time quantum-classical path integral (QCPI) methodology has been developed, which converges to the stationary phase limit of the full path integral with respect to the degrees of freedom comprising the system’s environment. The starting point is the identification of two components in the effects induced on a quantum system by a polyatomic environment. The first, “classical decoherence mechanism” is associated with phonon absorption and induced emission and is dominant at high temperature. Within the QCPI framework, the memory associated with classical decoherence is removable. A second, nonlocal in time, “quantum decoherence process”, which is associated with spontaneous phonon emission, becomes important at low temperatures and is responsible for detailed balance. The QCPI methodology takes advantage of the memory-free nature of system-independent solvent trajectories to account for all classical decoherence effects on the dynamics of the quantum system in an inexpensive fashion. Inclusion of the residual quantum decoherence is accomplished via phase factors in the path integral expression, which is amenable to large time steps and iterative decompositions. -
2011 Steampunk
2011 Steampunk The age of steam - what discoveries it brings forth! What riches in knowledge and science mankind has attained through the march of progress! We marvel at the potential of the atom, and cower at the power of our machinery. And what of our triumphs? What of the work of Tesla, Watt, Faraday and the Curies? What once was the realm of magicians now becomes the realm of science! What wonders might yet spring forth as we delve deeper and deeper into the magia et mysterium of the world of STEAMPUNK! DO YOU DARE TO LOOK UPON THE VISAGE OF THE UNKNOWN? This year at Clementine Productions’ STEAMPUNK IV event, we do not simply aim to look at what lies on the surface of the wonder that scientific arts have delivered, but to delve deeper, into the possibilities to be found in both the uncanny and the academy! There are those who claim to speak with spirits through machines; others yet who claim to have photographed the immaterial! Is it so hard to believe? We have just unlocked the power of the x-ray and the radiowave. There are those who say that invisibility, teleportation, astral projection and psychic enhancements are lurking but around the corner, Model: Ivana. Photo: Tarik Carroll. Stylist: Berít New York. Jewelry: Dope Designs.Makeup: Jarrett Brandon. Jewelry: Carroll. Stylist: Berít New York. Model: Ivana. Photo: Tarik awaiting the next intrepid scientist who will uncover them! This year we take inspiration from such works as Tim Powers’s Infernal Contraptions and Christopher Priest’s The Prestige. -
Teleportation
TELEPORTATION ESSAY FOR THE COURSE QUANTUM MECHANICS FOR MATHEMATICIANS ANNE VAN WEERDEN SUPERVISOR DR B.R.U. DHERIN UTRECHT UNIVERSITY JUNE 2010 PREFACE The aim of this essay is to describe the teleportation process in such a way that it will be clear what is done so far, and what is still needed, to develop a teleportation device for humans, which would be my ultimate goal. However much is done already, there are thresholds that still have to be overcome, some of which will need real ingenuity, and others brute computing power, far more than we are now capable of. But I will show why I have confidence that we will reach this goal by describing the astonishing developments in the field of teleportation and the speed with which computing, or technology, evolves. The discovery that teleportation really is possible came about while I was in my thirties, but I was largely unaware of its further developments until I started the research for this essay. Assuming that I am not the only one who did not know, I wrote this essay aimed at people from my age, in their fifties, who, like me, started out without television and computer, I even remember my Mother telling me how she bought a transistor radio for the first time, placed it in a closet and closed the door, just to be amazed that it could still receive signals and play. We saw it all come by, from the first steps on the Moon watched on the television my parents had only bought a few years earlier, I clearly remember asking my Father who, with much foresight, got us out of our beds despite my -
Approximating Ground States by Neural Network Quantum States
Article Approximating Ground States by Neural Network Quantum States Ying Yang 1,2, Chengyang Zhang 1 and Huaixin Cao 1,* 1 School of Mathematics and Information Science, Shaanxi Normal University, Xi’an 710119, China; [email protected] (Y.Y.); [email protected] (C.Z.) 2 School of Mathematics and Information Technology, Yuncheng University, Yuncheng 044000, China * Correspondence: [email protected] Received: 16 December 2018; Accepted: 16 January 2019; Published: 17 January 2019 Abstract: Motivated by the Carleo’s work (Science, 2017, 355: 602), we focus on finding the neural network quantum statesapproximation of the unknown ground state of a given Hamiltonian H in terms of the best relative error and explore the influences of sum, tensor product, local unitary of Hamiltonians on the best relative error. Besides, we illustrate our method with some examples. Keywords: approximation; ground state; neural network quantum state 1. Introduction The quantum many-body problem is a general name for a vast category of physical problems pertaining to the properties of microscopic systems made of a large number of interacting particles. In such a quantum system, the repeated interactions between particles create quantum correlations [1–3], quantum entanglement [4–6], Bell nonlocality [7–9], Einstein-Poldolsky-Rosen (EPR) steering [10–12]. As a consequence, the wave function of the system is a complicated object holding a large amount of information, which usually makes exact or analytical calculations impractical or even impossible. Thus, many-body theoretical physics most often relies on a set of approximations specific to the problem at hand, and ranks among the most computationally intensive fields of science. -
Science Fiction, Steampunk, Cyberpunk
SCIENCE FICTION: speculative but scientific plausability, write rationally, realistically about alternative possible worlds/futures, no hesitation, suspension of disbelief estrangement+cognition: seek rational understanding of NOVUM (D. Suvin—cognitive estrangement) continuum bw real-world empiricism & supernatural transcendentalism make the incredible plausible BUT alienation/defamiliarization effect (giant bug) Literature of human being encountering CHANGE (techn innovat, sci.disc, nat. events, soc shifts) origins: speculative wonder stories, antiquity’s fabulous voyages, utopia, medieval ISLAND story, scientifiction & Campbell: Hero with a 1000 Faces & Jules Verne, HG Wells (Time Machine, War of the Worlds, The Island of Dr Moreau), Mary Shelley (Frankenstein), Swift Gulliver’s Travels Imaginative, Speculative content: • TIME: futurism, alternative timeline, diff hist. past, time travel (Wells, 2001. A Space Odyssey) • SPACE: outer space, extra-terrestrial adventures, subterranean regions, deep oceans, terra incognita, parallel universe, lost world stories • CHARACTERS: alien life forms, UFO, AI, GMO, transhuman (Invisible Man), mad scientist • THEMES: *new scientific principles, *futuristic technology, (ray guns, teleportation, humanoid computers), *new political systems (post-apocalyptic dystopia), *PARANORMAL abilities (mindcontrol, telekinesis, telepathy) Parallel universe: alternative reality: speculative fiction –scientific methods to explore world Philosophical ideas question limits & prerequisites of humanity (AI) challenge