It would be great to discuss your problems with decoherence, but you haven’t yet told me what they are! Unfortunately I don’t have time to read this paper you mentioned — I read the paragraph you suggested but it didn’t make sense to me without having read the rest of his argument.

Perhaps you could start by explaining what is wrong with the examples I gave of decoherence in my paper in the section titled Decoherence, starting on page 2. (Here’s the paper: https://arxiv.org/pdf/1811.09062.pdf)

Cheers

Paul

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]]>Thank you so much for your reply.

Why do I think that decoherence does not solve the measurement problem?

Well, thre is so much fuss about decoherence and now quantum Darwinism, so many serious people working in this field, that I can not simply ignore them.

I have started studying their contributions in earnest with strong feeling that there must be something important about the world that decoherence can reveal, yet the more I read the more I am puzzled and worried.

I am not very advanced in my study of the formalism and its consequences, but it is not something wrong with the formalism that keeps me awake at nights 🙂

I have rather serious difficulties to grasp the meaning, the foundations.

To be honest, I am not a 100% layman, but now I am more interested in philosophy of physics (and were my first name be different, I would have lost my initial enthusiasm for the works of Wojciech H. Zurek long time ago 😉 )

Reading more about the philosophy of quantum theory I have got infected with doubts that seems fatal and incurable for me.

The main infector for me was Chris Fields, take a look on his argumentation here: http://arxiv.org/abs/1402.6629v6

(about decoherence in the last paragraph of chapter 4, I do not understand what he writes in chap 5 and I suspect him of being wrong there but it does not matter)

or here: https://chrisfieldsresearch.com/quant-freedom.pdf

As you can see, it is not some specific part of the measurement problem that decoherence have not elucidated yet, the problem is deeper (I feel it must be so, as the observer is the keystone)

But it is so good to have such problem to think about, what a sad world would it be, were such problems could be solved so easily with decoherence or something like that!

Best regards,

Wojciech

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]]>Thanks for your comment and interest!

In my opinion decoherence does completely solve the measurement problem, but I didn’t fully explain this in my essay, hence the wording I used. But apologies if what I wrote in the abstract was misleading.

You said: “Is not the measurement problem (with ubiquitous questions about the role of the observer) the core, the essence of the problem of why and how our classical reality emerges?”

Generally I do agree with this! It depends on exactly how you define the measurement problem, and what aspect of classical reality you are trying to explain, but I agree that generally the measurement problem is a key part.

So, why do you think that decoherence does not solve the measurement problem? Which specific part of the measurement problem is not solved? If you tell me this, I will try to answer as best I can.

Best,

Paul

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]]>I have just discovered your very interesting blog via your last paper about decoherence and quantum Darwinism (http://arxiv.org/pdf/1811.09062.pdf), the one you mention here in this post.

Please excuse my layman question (being at the same time a friendly provocation), but introducing your paper you write:

> Together these theories explain how our classical reality emerges from an underlying quantum mechanical description

and in the last sentence of the abstract you announce that finally you are going to

> demonstrate how decoherence and quantum Darwinism can shed significant light on the measurement problem

(and indeed you write about the role of the observer and about the measurement problem just near the end, just before comparisions with Everett Interpretation and Conclusion)

How can you state the problem of emergence of classical reality solved when you can only (!) ,,shed significant light” on the measurement problem?

(what is more quirky you seem to admit that even having read almost the whole paper ,,it may not be immediately obvious” that decoherence and quantum Darwinism can shed that light)

Is not the measurement problem (with ubiquitous questions about the role of the observer) the core, the essence of the problem of why and how our classical reality emerges?

I know your answer:

> in decoherence and quantum Darwinism this is not the case

but is it a truly honest answer? or rather, is it the answer of someone from the Decoherence Church? I doubt it as in another paper (https://knottquantum.weebly.com/uploads/9/0/9/4/90944896/does_consciousness_collapse_the_quantum_state.pdf) you write:

> the so-called measurement problem of quantum mechanics […] lies at the very heart of the theory

and BTW, I do agree that ,,we cannot ever confirm that we are in a superposition”, but from completely different reasons, I just feel that trying to conduct such measurement would be like trying to bootstrap oneself up, what is more, using bootstrap in a superposition 😉

Best regards,

Wojciech

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]]>Next Bob makes a measurement. In a similar way, Bob will become entangled with the particles, and also with Alice and her surroundings, giving the state |A0>|00>|B0> + |A1>|11>|B1>. But Bob’s and Alice’s environments increasing interact with a larger volume of space, e.g. by photons flying around hitting things, then quite quickly the border between the two environments will meet. But at this point nothing magical happens because Bob and Alice are entangled already because they were entangled with the particle, so the branch in which Alice measures 0 is the same as the branch in which Bob measures 0.

In short, there is no non-locality, because everything travels only at the speed of light. And there is realism, because we can assume that the particles have a specific state (I think). So as far as I know in many worlds there is no problem at all with Bell’s Theorem, and we can have both locality and realism for free!

To do this analysis properly we have to imagine Alice and Bob measuring in difference bases, which basically results in a branch into more (probably 4) universes. But it still works nicely and retains locality and realism as far as I know.

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]]>Thank you

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