Interpretacions de la Mecànica Quàntica

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Time, the Arrow of Time, and Quantum Mechanics

It is brought forward that viable theories of the physical world that have no variable at all that can play the role of time, do not exist; some notion of time is one of the very first ingredients a candidate theory should possess. Almost by definition, time has an arrow. In contrast, time reversibility, or even the possibility to run the equations of motion backwards in time, is not at all a primary requirement. This means that the direction of the arrow of time may well be uniquely defined in the theory, even locally. It is explained that a rigorous definition of time, as well as a formulation of the causality and locality concepts, can only be given when one has a model for the physical phenomena described. The only viable causality condition is one that is symmetric under time reversal. We explain these statements in terms of the author's favored deterministic cellular automaton interpretation of quantum mechanics, also to be referred to as “vector space analysis,” and expand on these ideas. It is also summarized how our more rigorous causality condition affects Bell's theorems. What distinguishes quantum systems from classical ones is our fundamental inability to control the microscopic details of the initial state when phenomena are studied in the light of some theoretical model.

https://www.frontiersin.org/articles/10.3389/fphy.2018.00081/full

Quantum decoherence

Quantum decoherence is the loss of quantum coherence, the process in which a system's behaviour changes from that which can be explained by quantum mechanics to that which can be explained by classical mechanics. In quantum mechanics, particles such as electrons are described by a wave function, a mathematical representation of the quantum state of a system; a probabilistic interpretation of the wave function is used to explain various quantum effects. As long as there exists a definite phase relation between different states, the system is said to be coherent. A definite phase relationship is necessary to perform quantum computing on quantum information encoded in quantum states. Coherence is preserved under the laws of quantum physics.

https://en.wikipedia.org/wiki/Quantum_decoherence

Interpretacions

Copenhagen interpretation

The Copenhagen interpretation is a collection of views about the meaning of quantum mechanics, stemming from the work of Niels Bohr, Werner Heisenberg, Max Born, and others.[1] The term "Copenhagen interpretation" was apparently coined by Heisenberg during the 1950s to refer to ideas developed in the 1925–1927 period, glossing over his disagreements with Bohr.[2][3] Consequently, there is no definitive historical statement of what the interpretation entails.

https://en.wikipedia.org/wiki/Copenhagen_interpretation

Ensemble interpretation

The ensemble interpretation of quantum mechanics considers the quantum state description to apply only to an ensemble of similarly prepared systems, rather than supposing that it exhaustively represents an individual physical system.[1]

https://en.wikipedia.org/wiki/Ensemble_interpretation

Text que no té gaire sentit de moment (no fer-li cas)

Aleshores algunes notes sobre la interpretació de Copenhaguen

Un dels conceptes fonamentals d’aquesta interpretació és el concepte del pas del temps (time arrow), i la idea que el passat està completament definit mentre que el futur està totalment indefinit, és a dir que vivim en un món indeterministic.

De manera una mica més boja

Tot l’univers sencer estaria descrit per la funció d’ona, que seria solució de l’equació de Schrödinger que viuria en , sent el nombre de partícules més elementals possibles i la dimensió espacial del nostre univers (en principi ). El passat estaria completament definit i el futur completament indefinit, a cada moment en què el futur es fes present, la funció d’ona “col·lapsaria” i l’univers prendria aleatòriament un dels “quantum states” possibles, on cada “quantum state” quedaria descrit per un vector en l’espai de Hilbert.

Aquest “quantum state” que prendria l’univers seria tal que les partícules obligades a ser mesurades o mostrades, prendrien un estat concret mesurable en els reals.

Aleshores no és tan que nosaltres “mesurem” o “col·lapsem” la funció d’ona, de fet nosaltres com a éssers humans no fem res, només podem col·locar o canviar algunes coses (fer experiments) de manera que limitem la quantitat de “quantum states” possibles de l’univers i fem que alguns passin a ser impossibles mentre que d’altres totalment probables (o alguns més probables i d’altres menys). Però és la funció d’ona que “col·lapsa” per si sola a cada instant de temps.