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I don't think anyone has a satisfactory answer to this

so the cat state hasn't collapsed.

If the cat interacts with a quon, you just have two states: quon in state 1 + cat alive and quon in state 2 + cat dead (for example).

…. if you observe the cat….

Or do we, like the quon, become part of the quantum state? If the latter is true, we have to explain why we never experience being in a superposition, which likely requires explaining consciousness scientifically.

Quote from: JP on 14/05/2014 12:42:39 Or do we, like the quon, become part of the quantum state? If the latter is true, we have to explain why we never experience being in a superposition, which likely requires explaining consciousness scientifically. What are you expecting the experience of being in a superposition to be like? What could you notice about it that would be any different?

I suspect I may not have expressed my original question very well, so I’ll give it another shot.1. An unobserved quon is in an indeterminate state of superposition. When it is observed, measured or interacts with anything in its environment it assumes definite characteristics. This change is thermodynamically irreversible.

This is still fundamentally 2 quantum states in a superposition.

QuoteThis is still fundamentally 2 quantum states in a superposition.This is because there are only two states, irrespective of how many quons are involved?

4. Given that 1-3 are correct; why have not all the quons in the Universe already succumbed to decoherence? Have they? Are all quons that are in a state of quantum superposition artificially generated in experiments etc?

No, it's because I chose a simple example. :p

I would say the starting point is to just consider the interaction of 2 quons. Let's say quon 1 starts in a superposition of two states, 1A and 1B (the 1 signifies it is quon 1 and the A/B signifies one of two possible states).

Now quon 1 interacts with quon 2. In reality, interactions can be complicated, but in our thought experiment, let's say they interact in such a way that quon 2 goes into the same A or B state as quon 1. To describe this, we now have a state that is a superposition of 2 states: 1A+2A and 1B+2B. This is entanglement, by the way--if I measure particle 1 to be in a state, I know that particle 2 is in a matching state.

Assuming all particles behave like these quons, after interaction with N quons, we'll have a superposition of 2 states:1A+2A+3A+4A+...+NA and 1B+2B+3B+4B+...NB

The point of this is to show that it is not simply "interacting with a lot of other particles" that causes collapse.

if the initial quon is in superposition and it interacts with a second quon

. So if we draw a big box around everything our first quon has interacted with, we haven't lost information about the quantum-ness of it……

…… and can in theory recover its superposition.

What decoherence says is that to get full information about the quantum state of my quon, I need to have full information about the current quon and everything it's interacted with.

Quote if the initial quon is in superposition and it interacts with a second quon If the initial quon is not in superposition, would this mean that the interaction was not “quantum in nature”, or would the fact of the second quon being in superposition ensure the quantum nature of the reaction?

Quote . So if we draw a big box around everything our first quon has interacted with, we haven't lost information about the quantum-ness of it……Presumably this applies to the second quon as well.

Quote …… and can in theory recover its superposition. Just checking on the word “recover”. I assume it is “we” who do the recovering, as in learning about; not that the quon had lost its quantum-ness, and needs to get it back.

Quote What decoherence says is that to get full information about the quantum state of my quon, I need to have full information about the current quon and everything it's interacted with. This is where I may go off the rails. What I am getting from this is that decoherence does not come about as a result of quantum reactions between quons, but is a function of the extraction of information from a quantum system.

What I am assuming is that quantum mechanics underlies the behavior of quons.

although your original quon might be a mess once it's interacted with all the other quons in the box, information about its initial state is still preserved in there somehow.

Decoherence is based on a quantum version of statistical mechanics........

Quote What I am assuming is that quantum mechanics underlies the behavior of quons.I imagine it would be difficult to do anything in QM without this assumption.

Quote although your original quon might be a mess once it's interacted with all the other quons in the box, information about its initial state is still preserved in there somehow.Would this reflect the difference between waveform collapse and decoherence?

Quote Decoherence is based on a quantum version of statistical mechanics........ I know I've said this before, but if you have not already written a pop sci book, you should; and if you have, I want it!The reason I included the “Schrödingcat” in the OP is that most of the pop sci explanations I have seen have been attempts to describe why the cat would not be in superposition. How far off track would it be to ask if the cat might not be in superposition, but the individual quons of which the cat is composed might be?

Wavefunction collapse means that some process causes a part of the state to vanish irrecovably. Decoherence means that while your particle might appear to now be in only one state, its second state will be somehow stored in the environment. So in theory, the information's still there, even if it's impractical to access it.

There's another interesting theorem in quantum mechanics related to this: the no cloning theorem. What this says is that if you want to make a perfect copy of quon 1, you can't do it by measuring it and creating a second quon. The reason is that measurement will collapse its state. So if it is X% in state A and Y% in state B, and you take a measurement and see state A, you've lost information about the percentages, so you can't make a perfect copy. Decoherence may put the quon into state A, but the percentages are somehow stored in the environment.

If we observer a cat, we end up in a superposition. But this has a major problem that it can't explain why we don't feel like we're in a superposition.

Quote from: JP Wavefunction collapse means that some process causes a part of the state to vanish irrecovably. Decoherence means that while your particle might appear to now be in only one state, its second state will be somehow stored in the environment. So in theory, the information's still there, even if it's impractical to access it.That makes sense to me, but still leaves one point to be cleared up. In current scientific wisdom, are wavefunction collapse and decoherence considered as two separate things, either of which might happen; or is wavefunction collapse and outdated idea that has largely been replaced by decoherence?

Quote If we observer a cat, we end up in a superposition. But this has a major problem that it can't explain why we don't feel like we're in a superposition. So, as I sit “observing” my computer screen, I am in quantum superposition with my computer, but cannot be aware of that??

A interesting thread this one.

If you think of all the interpretations as just ways of trying to make sense of the mathematics of quantum mechanics, then you can pick or choose which makes the math the clearest for you.

....since all are equally well supported by both theory and experiment.