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 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 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’.

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’.

scholarly journals The passage of positive ions through gases

1933 ◽  
Vol 142 (846) ◽  
pp. 142-172 ◽  
Keyword(s):  
Quantum Mechanics ◽  
Charged Particles ◽  
Foundations Of Quantum Mechanics ◽  
Wave Theory ◽  
Point Of View ◽  
General Description ◽  
Theoretical Point ◽  
Positive Ions ◽  
The Subject ◽  
Ramsauer Effect

A large number of investigations have been carried out on the motion of charged particles through gases, and the subject has received added impetus from the introduction of quantum mechanics, as this theory is capable of dealing with collision phenomena in a manner that was beyond the reach of Bohr’s quantum theory. In the early days of the wave theory, many experiments were devised with a view to testing the validity of the theory; but now the foundations of quantum mechanics have been so firmly laid that we may use the theory to clarify the more complicated phenomena observed in the passage of charged particles through gases. Both from the experimental and theoretical point of view the most convenient particles to study are electrons; and, as a consequence, the phenomena observed in the collisions of electrons with gas molecules are well known and to a large extent understood. Well-marked diffraction phenomena have been observed and the relative probabilities of elastic and inelastic collisions measured for a number of gases. Although detailed theoretical explanations have not always been given, it is possible in nearly all cases to give a general description of the main processes contributing to the observed effects. For example, the Ramsauer effect is now completely explained.

scholarly journals The small stellated dodecahedron code and friends

2018 ◽  
Vol 376 (2123) ◽  
pp. 20170323 ◽  
Author(s):  
J. Conrad ◽  
C. Chamberland ◽  
N. P. Breuckmann ◽  
B. M. Terhal
Keyword(s):  
Quantum Mechanics ◽  
Fault Tolerant ◽  
Three Dimensional ◽  
Foundations Of Quantum Mechanics ◽  
Quantum Code ◽  
Contemporary Society ◽  
Parity Check ◽  
Logical Qubits ◽  
Surface Code ◽  
Logical Qubit

We explore a distance-3 homological CSS quantum code, namely the small stellated dodecahedron code, for dense storage of quantum information and we compare its performance with the distance-3 surface code. The data and ancilla qubits of the small stellated dodecahedron code can be located on the edges respectively vertices of a small stellated dodecahedron, making this code suitable for three-dimensional connectivity. This code encodes eight logical qubits into 30 physical qubits (plus 22 ancilla qubits for parity check measurements) in contrast with one logical qubit into nine physical qubits (plus eight ancilla qubits) for the surface code. We develop fault-tolerant parity check circuits and a decoder for this code, allowing us to numerically assess the circuit-based pseudo-threshold. This article is part of a discussion meeting issue ‘Foundations of quantum mechanics and their impact on contemporary society’.

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 On the Stochastic Origin of Quantum Mechanics

2017 ◽  
Vol 01 (03) ◽  
pp. 1750008 ◽  
Author(s):  
Roumen Tsekov
Keyword(s):  
Stochastic Process ◽  
Diffusion Coefficient ◽  
Quantum Mechanics ◽  
Phase Space ◽  
Quantum System ◽  
Liouville Equation ◽  
Point Of View ◽  
Quantum Phase ◽  
Relativistic Mass ◽  
Space Dynamics

The quantum Liouville equation, which describes the phase space dynamics of a quantum system of fermions, is analyzed from stochastic point of view as a particular example of the Kramers–Moyal expansion. Quantum mechanics is extended to relativistic domain by generalizing the Wigner–Moyal equation. Thus, an expression is derived for the relativistic mass in the Wigner quantum phase space presentation. The diffusion with an imaginary diffusion coefficient is discussed. An imaginary stochastic process is proposed as the origin of quantum mechanics.

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