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romsofia
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When does the probabilistic nature of QM breakdown?
Is it just as a the system gets larger, it's less probabilistic?
Is it just as a the system gets larger, it's less probabilistic?
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tom.stoer said:... decoherence which explains to some extent the emergence of a classical world ...
StevieTNZ said:Do note that decoherence is "for all practical purposes" (FAPP). In principle, at least according to QM, no to a classical world (i.e. definite state) occurs. We still have a measurement problem on our hands.
We need to wait and see the results of various experiments place, whereby putting a (I think 40kg) - definite a large mirror in size, so macroscopic, into a superposition of two distinct macroscopic states (in this case the observable position). There is a book reference I cannot find now, but there is notes on making clear that we are seeing distinct MACROSCOPIC states, conforming to certain (minimum) standards, as to ascert e.g. between a live and dead cat. I will try find it later, and if I can, will post it in this thread.
Do note, even though we find macroscopic superposition occurs, we still need to rule out macrorealism - even using the Leggett-Garg inequality, WITHOUT the use of coarse-grain measurements.
audioloop said:a good parameters at:
Phys. Rev. Lett. 106, 220401 (2011)
Quantification of Macroscopic Quantum Superpositions
http://prl..org/abstract/PRL/v106/i22/e220401
...we propose a novel measure to quantify macroscopic quantum superpositions. Our measure simultaneously quantifies two different kinds of essential information for a given quantum state in a harmonious manner: the degree of quantum coherence and the effective size of the physical system that involves the superposition. It enjoys remarkably good analytical and algebraic properties. It turns out to be the most general and inclusive measure ever proposed that it can be applied to any types of multipartite states and mixed states represented in phase space...
The probabilistic breakdown of quantum mechanics refers to the idea that at the quantum level, particles and systems do not behave in a deterministic manner, but rather their behavior is described by probabilities. This means that it is impossible to predict the exact outcome of a quantum experiment, but we can calculate the likelihood of different outcomes.
Probability plays a central role in quantum mechanics because it is used to describe the behavior of particles and systems at the quantum level. According to the principles of quantum mechanics, particles can exist in multiple states at the same time, and their behavior is described by a wave function that assigns probabilities to each possible state.
In classical mechanics, the behavior of particles and systems is deterministic, meaning that their exact position and momentum can be predicted with complete certainty. In quantum mechanics, however, the behavior is probabilistic, and it is impossible to predict the exact outcome of a measurement.
The uncertainty principle, first proposed by Werner Heisenberg, states that it is impossible to know both the exact position and momentum of a particle at the same time. This is because the act of measuring one property of a particle affects the other, and the more precisely one is measured, the less precisely the other can be known. This is a fundamental aspect of the probabilistic nature of quantum mechanics.
There have been numerous experiments conducted that demonstrate the probabilistic nature of quantum mechanics. One of the most famous is the double-slit experiment, which shows that particles can behave as both waves and particles, and their behavior is described by probabilities. Other experiments, such as the Bell test, also support the probabilistic nature of quantum mechanics.