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Zurek estimates that a gram of matter at normal conditions of temperature and density will undergo an interaction with its environment within 10 seconds. Misconceptions around the idea of isolation may be at the basis of the 'measurement problem'. Standard quantum theory supporting the paradox assume that the cat system would remain an isolated non-interacting quantum system until a human measurement looking in the box was performed.
Some even ventured so far as to speculate that human consciousness was required to have the state of the cat resolved into an 'alive' or 'dead' outcome. This view now seems hopelessly anthropomorphic and one wonders how it could have been seriously entertained.
As the work of Zurek and others on decoherence makes clear the quantum superposition of states such as 'alive' and 'dead' tend to rapidly decohere into particular classical states such as 'alive' or 'dead'. This process is now understood to be analogous with axiom 4 above but rather than a wave function 'collapse' we should view decoherence as the preferential extinction of quantum superpositions and the survival of classical states due to interactions that may be human measurements buy are typically environmental interactions. Basically any measurement can only result in some special values associated with 'pointer states'.
Pointer states are thus associated with the type of measurement being performed. For instance in the case of a measurement designed to determine the survival of the cat there are two pointer states: 'alive' and 'dead'. The isolated quantum system consists of a superposition or combination of these pointer states as well as superpositions of all other pointer states associated with other possible measurements typical values for these superpositions are that the cat is both alive and dead and that it is here as well as over there. Environmental interaction with the system results in the extinction of the pointer state superpositions and the survival of only 'pure' pointer states.
The weird quantum states are filtered out in the emergence of our classical reality from its quantum roots.
Wojciech Zurek - Google Scholar Citations
As is common with successful scientific theories explaining how a few possibilities allowing vast increases in complexity are selected from a multitude of fruitless alternatives he posits a Darwinian mechanism at its heart. The resulting theory of Quantum Darwinism is relatively straightforward:. The primary mechanism causing decoherence is the many types of interactions that the quantum system has with its environment.
Typically quantum systems experience a vast number of such environmental interactions selectively destroying entangled quantum states. Their prolonged survival is due to the peculiar property of these pointer states that interactions with the environment and the subsequent decoherence leave them largely unchanged.
They alone are able to survive in the face of environmental monitoring. It is these environmental copies that we actually experience and from which we gain information concerning quantum systems in almost all cases. For instance quantum systems are in continual interaction with the vast number of photons in their immediate environment. When we observe an object visually we are actually accessing information that has been imprinted on photons during previous interactions with the quantum system under observation. While this process may explain the emergence of classical physics from quantum physics it may not be clear where the Darwinian part comes in.
Zurek explains his motivation in naming Quantum Darwinism:. Classical domain of pointer states offers a static summary of the result of quantum decoherence.
Save for classical dynamics, almost nothing happens to these einselected states, even though they are immersed in the environment. Still we might quibble and demand a more formal comparison of Quantum Darwinism to the defining mechanisms of a Darwinian process. A Darwinian process is any that utilizes the following algorithm:. Information concerning the state of a quantum system is copied with variations.
Thus we can see, at least from one point of view, that Quantum Darwinism is a true Darwinian process and meets the criterion for inclusion within the field of Universal Darwinism.
Such a view is cautioned against by some researchers but this may be due to the unfamiliarity of many physical scientists with Darwinian concepts. It looks somewhat like evolution theory in biology: the dissemination of information in environment is like reproduction but reproduction of information, not of material bodies. There is however no direct competition between the states for a limited supply of resources, as in real life, and of course no sexual reproduction of states!
An amusing metaphor which should be used with caution. Darwin was the first to note that the Darwinian process is an algorithm given above that if followed will result in evolution and is not limited to a biological implementation. None of Haroche's objections oppose this algorithm.
His first point is somewhat confusing as it is now well accepted that information always has a physical representation.
Decoherence, Einselection, And the Quantum Origins of the Classical
A reading of research in Universal Darwinism makes clear how the Darwinian algorithm is implemented in a wide variety of fields outside of biology [vi] , [vii]. Given that Quantum Darwinism is a Darwinian mechanism we should expect to see products of its evolutionary design in our world.
What might these be? The answer may be both surprising and revolutionary as the surviving physical states produced by Quantum Darwinism are the totality of the classical word in which we live and experience the rest of the universe. In other words the evolutionary products of Quantum Darwinism may be the classical reality in which all other Darwinian processes operate and produce their own evolutionary products.
I have a question not directly related to decoherence about your general view of QM. In all your posts touching the subject of QM you insist on the "proven" fundamentally probabilistic nature of our universe and on the failure of various non-orthodox interpretations to explain the experimental data.
My question is how do you explain the experimental results correctly predicted by QM for a simple EPR experiment where both Alice and Bob measure the spin on the same axis. We know for a fact that every such measurement will result in a perfect anticorrelation or correlation if using PDC.
Logically, I see only two possible explanations: 1. A non-local interaction of some sort wave function might be a real, physical field, or some other non-local force might be at work 2. A strict deterministic evolution of the entire system including the so-called free choices of Alice and Bob - hypothesis named superdeterminism by Bell.
As far as I could understand you reject both explanations and say that one must accept the pure probabilistic nature of QM. However, I don't see how this appeal to probabilities explains the experimental data. Can you explain your position on this matter, or you take the "shut up and calculate" approach? Thank you, Andrei Bocan. Dear Andrei, indeed, both "explanations" that you can see are wrong. And indeed, one must accept the probabilistic interpretation of QM.
It's interesting that you admit that you know this possible answer, but you still don't include it among the explanations that "you can see". Do you become blinded right before you enumerate the answers that "you can see"? It explains all of them. The probabilistic distributions always match the predictions of QM, and so does the very random character of all individual events. What we see is what quantum mechanics predicts. An alternative theory would claim that the outcome of individual measurements is not random - but huge classes of such conceivably alternative theories have been proven impossible i.
- Localization of Coherent Wave Packets in Plasmas due to Decoherence.
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So it is not only about these theories' being uneconomic; they are literally excluded today. I think that I am explaining my position about all these matters all the time. Why do you think that I am not? I think that it is because you may be a blinded zealot who simply doesn't want to "see" certain things. After all those detailed and brutally indisputable explanations, "shut up and calculate" sounds far too optimistic because you don't seem to want to calculate anything.
Thank you! I accept the fact that QM correctly predicts anything that can be tested. But you didn't answer the question of how do you explain those predictions? Why does Alice's measurement change the probabilities at Bob's place which can be far away if the two regions cannot influence each other? Dear Andrei, when it comes to common language, "explain" is something different because it can also mean what the teachers are supposed to do, while "predict" is what the analysts are doing.
Related Decoherence, einselection,and the quantum origins of the classical
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