
Quantum Darwinism, an Idea to Explain Objective Reality, Passes First Tests - bookofjoe
https://www.quantamagazine.org/quantum-darwinism-an-idea-to-explain-objective-reality-passes-first-tests-20190722/
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jessriedel
I was quoted in this piece, and adapted some of my correspondence with the
author into a blog post: [http://blog.jessriedel.com/2019/07/24/faq-about-
experimental...](http://blog.jessriedel.com/2019/07/24/faq-about-experimental-
quantum-darwinism/)

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pdonis
Are the actual papers available online? On arxiv.org?

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jessriedel
Yes, they are linked from the blog post. The experimental papers are arXiv
numbers 1803.01913, 1808.07388, and 1809.10456. The basic theoretical papers
are available from the Wikipedia page on quantum Darwinism, also linked.

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pdonis
Ok, thanks!

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faissaloo
I don't know if the analogy to darwinian evolution makes much sense, it seems
to me that it makes more sense to see this as a way of error-correcting our
reality, that is to say quantum phenomenon occur because anything else would
cause a severe inconsistency.

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jessriedel
It is indeed a stretch, but it's just supposed to be an evocative name not a
perfect analogy. In particular, quantum Darwinism has a notion of fittest
types of information, and this information is replicated, but it crucially
does not feature a notion of mutation, so in particular it cannot result in
increasing complexity/sophistication over time as produced by biological
Darwinism.

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c3534l
Evocative "sorta" names have a tendency to spread misinformation when the
scientific details are opaque to most people. It's not a practice that I think
is okay.

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jessriedel
Then you should probably express your displeasure to guy who picked the name
:)

Seriously though, all evocative names are imperfect. Laymen always over
interpret them. I don't like "quantum Darwinism" much, but if your standard is
that the name of a mathematical concept not be misinterpreted, then basically
all English words are out.

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gpderetta
Relevant xkcd: [https://xkcd.com/895/](https://xkcd.com/895/)

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jonbaer
Zurek explaining some of it @
[https://www.youtube.com/watch?v=27zMdaBgt6g](https://www.youtube.com/watch?v=27zMdaBgt6g)

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aj7
Really good article but I’m unconvinced about those pointer states. The
classicly observed values simply have overwhelmingly higher probability.

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gpsx
I also view the apearance of classical physics as you say, but I am not sure
if that rules out this concept in the article. I admittedly don't really
understand what the article is saying. (It takes me alot of work to understand
these things.) The author does admit that this is just an implementation of
the basic laws of quantum maechanics. I suppose why this is interesting is
just that in large systems the aggregate behavior does not always follow
obviously from the basic rules.

I would like to write down what I considered to be the standard motivation for
why the classical solution arises, which is in other words why it is more
probable, as you point out.

In the Feynman path integral formalism, any paths in the system is possible,
with an amplitude proprotional to the exponential of the action. (Action as in
a Lagrangian). For paths that are an extremum of the action, there is the
least destructive interference between neighboring paths, since there is the
smallest phase change between these neighboring paths. Of course this extremum
of the action is, not coincidentally, the classical solution, which is the
result from the lagrangian formulation of classical machanics.

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self_awareness
From the first paragraph of the article:

> An atom typically can’t be assigned a definite position, for example — we
> can merely calculate the probability of finding it in various places.

Is this really the case? Or maybe author meant 'electron' instead of 'atom'?

I mean, if we wouldn't be able of calculating the position of an Atom, how
could "A Boy And His Atom" would be possible?

[https://www.youtube.com/watch?v=oSCX78-8-q0](https://www.youtube.com/watch?v=oSCX78-8-q0)

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titzer
There is a limit to the precision of a position measurement of any particle,
and atoms are made of many particles. The Heisenberg Uncertainty Principle
states that the uncertainty of the position and momentum of a particle are
related. In particular, the product of the errors has a constant lower bound.
Visually, if you think of (1d) position and (1d) momentum plotted on a 2d
graph, then Heisenberg's principle means that particles are not points, but
rectangles with a minimum area.

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omarhaneef
I can tell when I don't truly understand something by my ability to disagree,
or make counter arguments. In this case it sounds reasonable -- that the
probability distributions of the quantum scale somehow cohere because of a
Darwinian mechanism. But if you told me, oh, actually the center of mass of
the probability distributions is perceived as the real location, that makes
sense too.

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iainmerrick
I know it’s just an off the cuff example, but that one seems easy to argue
against -- in the double slit experiment, the particle is perceived to go
through both slits, not through the middle.

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thelazydogsback
> possible only because pointer states of quantum objects exist

I knew it was pointers! So observation is the universe's GC? I feel better
knowing that life is here at least to collapse enough wave functions to keep
things humming along nicely. (Ever wake up and feel that you must have been
stopped-and-copied over the night??)

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KevinCarbonara
I know this is a joke, but QD specifically excludes the requirement of a
living observer.

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kleer001
Wrap this up in an visualization animation and I'm sure I could understand it.

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jackfoxy
Here's a rebuttal from a physicist [https://motls.blogspot.com/2019/07/quanta-
magazines-anti-qua...](https://motls.blogspot.com/2019/07/quanta-magazines-
anti-quantum-zeal.html)

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calais
The rebuttal takes a view which is close to my heart—but [Motl] puts it so
viciously, dismisses without genuine inquiry or curiosity the intriguing
claims of the article, and plays so much faster and looser with his ideas than
the author he critiques—you can taste his contrition. Ball and [Motl] are
probably both mistaken about what QD actually explains.

Edit: fixed names

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MrEldritch
For future reference, "Luboš Motl" and "puts it so viciously, dismisses
without genuine inquiry or curiosity [....], and plays so much faster and
looser with his ideas than the author he critiques—you can taste his
contrition" are pretty much synonymous. The man's a troll with a PhD.

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api
I sort of got this but I found this article full of clunky analogies including
the "Darwinism" tag itself.

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pmoriarty
Is there even such a thing as objective reality?

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magnamerc
Would the Universe exist if there were no conscious beings to observe it?

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codesushi42
So much for parallel universes?

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__i___ii____
Damn I feel stupid.

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krastanov
Don't. I just got my PhD (working on quantum computing at a good school) and I
do not really get the point they are making. It is interesting, but esoteric
even for people working in related fields.

However, it is a great opportunity to start learning more about it!

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ohaideredevs
My comment isn't useful, but I really can't get a handle on anything "quantum"
related. The only thing I _sort_ of understand is that if you could entangle a
massive amount of photons/electrons, you could have "quantum radar" which
would be jam-proof.

I don't really understand even that though. Could you verify an electron
reflecting back is entangled with an electron you have on hand, or are they
all just "entangled" with something or "entangled" with some spin (which could
be replicated)?

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andrepd
>My comment isn't useful, but I really can't get a handle on anything
"quantum" related.

That is probably because you have tried to read "applications" papers/articles
(some of them of dubious scientific value, and more sci-fi/futurology) without
properly understanding the fundamentals first. I strongly recommend "Quantum
Mechanics", Cohen-Tannoudji et al. The first two chapters are the best
introduction to quantum mechanics I've read: concise and to the point,
starting from experiment and explaining the key ideas of quantum theory, and
then the mathematical formulation.

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ohaideredevs
Thanks for the recommendation!

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canada_dry
As a layman I just can't get past the glaring reality of: we simply do not
possess the means (i.e. equipment/tools) to examine/measure/control the
fundamental elements of matter without utterly affecting the outcome in ways
we are not able to control, understand or accurately predict.

I don't believe there is any amount of quantum theories that will get us past
this fundamental boundary.

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iainmerrick
It can be made to work in at least some cases -- for example, QED is a theory
about how individual photons and electrons behave that’s in truly fantastic
agreement with experimental results.

There’s a deep philosophical question about whether we can every truly learn
the _real_ fundamental laws of nature, sure; but it certainly looks like we
can get very very close, perhaps arbitrarily close.

