scholarly journals What is quantum in quantum randomness?

2018 ◽  
Vol 376 (2123) ◽  
pp. 20170322 ◽  
Author(s):  
P. Grangier ◽  
A. Auffèves
Keyword(s):  
Quantum Mechanics ◽  
Quantum Theory ◽  
Quantum Physics ◽  
Foundations Of Quantum Mechanics ◽  
Quantum Systems ◽  
Contemporary Society ◽  
Quantum Thermodynamics ◽  
Quantum Randomness ◽  
Classical World ◽  
The Impact

It is often said that quantum and classical randomness are of different nature, the former being ontological and the latter epistemological. However, so far the question of ‘What is quantum in quantum randomness?’, i.e. what is the impact of quantization and discreteness on the nature of randomness, remains to be answered. In a first part, we make explicit the differences between quantum and classical randomness within a recently proposed ontology for quantum mechanics based on contextual objectivity. In this view, quantum randomness is the result of contextuality and quantization. We show that this approach strongly impacts the purposes of quantum theory as well as its areas of application. In particular, it challenges current programmes inspired by classical reductionism, aiming at the emergence of the classical world from a large number of quantum systems. In a second part, we analyse quantum physics and thermodynamics as theories of randomness, unveiling their mutual influences. We finally consider new technological applications of quantum randomness that have opened up in the emerging field of quantum thermodynamics. This article is part of a discussion meeting issue ‘Foundations of quantum mechanics and their impact on contemporary society’.

scholarly journals Operational locality in global theories

2018 ◽  
Vol 376 (2123) ◽  
pp. 20170321 ◽  
Author(s):  
Lea Krämer ◽  
Lídia del Rio
Keyword(s):  
Quantum Mechanics ◽  
Quantum Theory ◽  
Physical Theory ◽  
Foundations Of Quantum Mechanics ◽  
Building Blocks ◽  
Contemporary Society ◽  
Operational Model ◽  
State Spaces ◽  
Local Functions ◽  
Generalized Probability

Within a global physical theory, a notion of locality allows us to find and justify information-processing primitives, like non-signalling between distant agents. Here, we propose exploring the opposite direction: to take agents as the basic building blocks through which we test a physical theory, and recover operational notions of locality from signalling conditions. First, we introduce an operational model for the effective state spaces of individual agents, as well as the range of their actions. We then formulate natural secrecy conditions between agents and identify the aspects of locality relevant for signalling. We discuss the possibility of taking commutation of transformations as a primitive of physical theories, as well as applications to quantum theory and generalized probability frameworks. This ‘it from bit’ approach establishes an operational connection between local actions and local observations, and gives a global interpretation to concepts like discarding a subsystem or composing local functions. This article is part of a discussion meeting issue ‘Foundations of quantum mechanics and their impact on contemporary society’.

scholarly journals Timelessness Strictly Inside the Quantum Realm

Entropy ◽  
2021 ◽  
Vol 23 (6) ◽  
pp. 772
Author(s):  
Knud Thomsen
Keyword(s):  
Real World ◽  
Quantum Physics ◽  
Quantum Systems ◽  
The Real ◽  
Classical World ◽  
Quantum Objects ◽  
The Everyday ◽  
Double Slit

Time is one of the undisputed foundations of our life in the real world. Here it is argued that inside small isolated quantum systems, time does not pass as we are used to, and it is primarily in this sense that quantum objects enjoy only limited reality. Quantum systems, which we know, are embedded in the everyday classical world. Their preparation as well as their measurement-phases leave durable records and traces in the entropy of the environment. The Landauer Principle then gives a quantitative threshold for irreversibility. With double slit experiments and tunneling as paradigmatic examples, it is proposed that a label of timelessness offers clues for rendering a Copenhagen-type interpretation of quantum physics more “realistic” and acceptable by providing a coarse but viable link from the fundamental quantum realm to the classical world which humans directly experience.

scholarly journals Consistent description of microscopic phenomena by macroscopic observers in quantum theory

2021 ◽  
Author(s):  
Alexey Kryukov
Keyword(s):  
Quantum Mechanics ◽  
Quantum Theory ◽  
Quantum Physics ◽  
Random Noise ◽  
Thought Experiments ◽  
Newtonian Physics ◽  
Measurement Results ◽  
Modern Physics ◽  
Measured System ◽  
Physical Phenomena

Abstract Quantum mechanics is the foundation of modern physics that is thought to be applicable to all physical phenomena, at least in principle. However, when applied to macroscopic bodies, the theory seems to be inconsistent. Wigner's friend and related thought experiments demonstrate that accounts by different observers described by the rules of quantum mechanics may be contradictory. Although still highly debated, such experiments seem to demonstrate an incompatibility of quantum mechanics with the usual rules of logic. Alternatively, one of the hidden assumptions in the thought experiments must be wrong. For instance, the argument is invalidated if macroscopic observers cannot be considered as physical systems described by the rules of quantum theory. Here we prove that there is a way to apply the rules of quantum mechanics to macroscopic observers while avoiding contradictory accounts of measurement by the observers. The key to this is the random noise that is ever present in nature and that represents the uncontrollable part of interaction between measured system and the surroundings in classical and quantum physics. By exploring the effect of the noise on microscopic and macroscopic bodies, we demonstrate that accounts of Wigner, the friend and other agents all become consistent. Our result suggests that the existing attempts to modify the Schrodinger equation to account for measurement results may be misguided. More broadly, the proposed mechanism for modeling measurements underlies the phenomenon of decoherence and is shown to be sufficient to explain the transition to Newtonian physics in quantum theory.

scholarly journals Extracontextuality and extravalence in quantum mechanics

2018 ◽  
Vol 376 (2123) ◽  
pp. 20170311 ◽  
Author(s):  
Alexia Auffèves ◽  
Philippe Grangier
Keyword(s):  
Quantum Mechanics ◽  
Quantum System ◽  
Foundations Of Quantum Mechanics ◽  
Point Of View ◽  
Contemporary Society ◽  
The Continuum

We develop the point of view where quantum mechanics results from the interplay between the quantized number of ‘modalities’ accessible to a quantum system, and the continuum of ‘contexts’ that are required to define these modalities. We point out the specific roles of ‘extracontextuality’ and ‘extravalence’ of modalities, and relate them to the Kochen–Specker and Gleason theorems. This article is part of a discussion meeting issue ‘Foundations of quantum mechanics and their impact on contemporary society’.

scholarly journals Irreversibility in quantum mechanics

2004 ◽  
Vol 2004 (1) ◽  
pp. 75-83 ◽  
Author(s):  
R. C. Bishop ◽  
A. Bohm ◽  
M. Gadella
Keyword(s):  
Quantum Mechanics ◽  
Quantum Theory ◽  
Boundary Conditions ◽  
Liouville Equation ◽  
Quantum Systems ◽  
Arrow Of Time ◽  
Time Asymmetry ◽  
Classical Physics ◽  
Von Neumann ◽  
Signal Features

Time asymmetry and irreversibility are signal features of our world. They are the reason of our aging and the basis for our belief that effects are preceded by causes. These features have many manifestations called arrows of time. In classical physics, some of these arrows are described by the increase of entropy or probability, and others by time-asymmetric boundary conditions of time-symmetric equations (e.g., Maxwell or Einstein). However, there is some controversy over whether probability or boundary conditions are more fundamental. For quantum systems, entropy increase is usually associated with the effects of an environment or measurement apparatus on a quantum system and is described by the von Neumann-Liouville equation. But since the traditional (von Neumann) axioms of quantum mechanics do not allow time-asymmetric boundary conditions for the dynamical differential equations (Schrödinger or Heisenberg), there is no quantum analogue of the radiation arrow of time. In this paper, we review consequences of a modification of a fundamental axiom of quantum mechanics. The new quantum theory is time asymmetric and accommodates an irreversible time evolution of isolated quantum systems.

Quantum theory from quantum information: the purification route

2013 ◽  
Vol 91 (6) ◽  
pp. 475-478 ◽  
Author(s):  
Giulio Chiribella ◽  
Xiao Yuan
Keyword(s):  
Quantum Mechanics ◽  
Information Processing ◽  
Quantum Theory ◽  
Quantum Information ◽  
Foundations Of Quantum Mechanics ◽  
Mathematical Structure ◽  
Mathematical Language ◽  
Standard Quantum ◽  
Information Theoretic

Quantum information provided a new angle on the foundations of quantum mechanics, where the emphasis is placed on operational tasks pertaining to information-processing and computation. In this spirit, several authors have proposed that the mathematical structure of quantum theory could (and should) be rebuilt from purely information-theoretic principles. Here we review the particular route proposed by D'Ariano, Perinotti, and one of the authors (Chiribella et al. Phys. Rev. A, 84, 012311 (2011)), with the purpose of giving a synopsis of the informational principles therein, along with a translation of those principles into the mathematical language of standard quantum theory.

scholarly journals Locality and quantum mechanics

2018 ◽  
Vol 376 (2123) ◽  
pp. 20170320 ◽  
Author(s):  
W. G. Unruh
Keyword(s):  
Quantum Mechanics ◽  
Foundations Of Quantum Mechanics ◽  
Contemporary Society ◽  
Non Local

It is argued that it is best not to think of quantum mechanics as non-local, but rather that it is non-realistic. This article is part of a discussion meeting issue ‘Foundations of quantum mechanics and their impact on contemporary society’.

Processual Thinking in the Ontological and Epistemological context of Quantum Mechanics

2019 ◽  
Vol 62 (7) ◽  
pp. 21-36 ◽  
Author(s):  
Vladimir I. Arshinov ◽  
Vladimir G. Budanov
Keyword(s):  
Quantum Mechanics ◽  
Quantum Physics ◽  
Biological Diversity ◽  
Relativistic Quantum ◽  
Foundations Of Quantum Mechanics ◽  
Natural Environments ◽  
Cultural Codes ◽  
Problems Of Translation ◽  
Different Cultures ◽  
Cognitive Niches

The problem of commensurability/incommensurability of different cultural codes is a key problem of modern civilizational development. This is the problem of the search for communicative unity in the world of cultural and biological diversity, which has to be protected, and the search for the cohesion of different Umwelten, of semiotically-defined artificial and natural environments, of ecological and cognitive niches, taking into account that each of them has their own identity and uniqueness. The purpose of the article is to draw attention to the fact that the question of the so-called incommensurability of different conceptual schemes, paradigms, language consciousnesses is widely discussed not only in cross-cultural studies and philosophical problems of translation but also in connection with the problems of incommensurability (untranslatability) between the language of classical physics and the language of relativistic quantum physics. Attention is drawn to the problem of the incommensurability and correlation of different languages that are used in debates about the foundations of quantum mechanics, its interpretation, comprehension and ontology. Two approaches stand out in this debate. The first approach is based on the language of the formed being, on the language of things localized in time and on the logic of Aristotle. The second approach is based on the language of the becoming, process and nonlocality, on the search for various processual-oriented temporal logics. In this regard, we discuss the processual approach to understanding quantum mechanics, proposed in the philosophical and physical works of D. Bohm. The authors argue that (a) the experience of constructive understanding of the metaproblems of the interpretation of quantum mechanics, (b) the critical reception of the legacy of such philosophers of the process as Peirce, Bergson and Whitehead, (c) the deep reflection on the problems of commensurability/ incommensurability of linguistic consciousnesses of different cultures – will eventually create a common synergetic-interdisciplinary space of cooperation for the solutions of the above-mentioned issues.

scholarly journals ‘Space is blue and birds fly through it’

2018 ◽  
Vol 376 (2123) ◽  
pp. 20170312 ◽  
Author(s):  
Carlo Rovelli
Keyword(s):  
Quantum Mechanics ◽  
Foundations Of Quantum Mechanics ◽  
Quantum States ◽  
Contemporary Society ◽  
Physical Variables

Quantum mechanics is not about ‘quantum states’: it is about values of physical variables. I give a short fresh presentation and update on the relational perspective on the theory, and a comment on its philosophical implications. This article is part of a discussion meeting issue ‘Foundations of quantum mechanics and their impact on contemporary society’.

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