How Does Environmentally Induced Decoherence Affect Quantum State Reduction?

[stevendaryl]

(BTW, does anybody know how to attach a jpg picture which would demonstrate my child artistic talents? I have a scanned version of the picture on my computer, but I don't have an URL.)

What does the "media" button do?

You could send the picture to me, and I could upload it to my website (which is pretty much only used for sharing pictures).

 

[Feeble Wonk]

Well, from MW perspective there are two cats: one dead and one alive.
In a "potential-world" language I guess one would say that the cat has (a potential for both being dead) and (a potential for being alive). However, due to decoherence it does not have a potential for being (dead and alive).

Yes... That's what I meant. The "post-decoherence" worlds will all have either a live cat or a dead cat. So if I'm understanding you correctly, as with the ensemble interpretation, the concept of a superposed (pure state) live AND dead cat is not really accurate with the MW type of interpretation either.
Before considering "collapse" models, I suppose I should get some clarification on the dBB/pilot wave scenario. My general impression at this point is that this is a deterministic model where the trajectory of the isolated system within the closed box is statistically predicted by quantum mechanics. But here too, the cat inside the closed box might be dead OR alive after the system has decohered, but should not be thought of as being in a superposed pure state of dead AND alive.
Correct?

 

[Feeble Wonk]

(BTW, does anybody know how to attach a jpg picture which would demonstrate my child artistic talents? I have a scanned version of the picture on my computer, but I don't have an URL.)

I don't know how to do it, but I'd like to see it. Any chance it's a picture of a cat? [emoji15]

 

[stevendaryl]

Well, from MW perspective there are two cats: one dead and one alive.

In a "potential-world" language I guess one would say that the cat has (a potential for both being dead) and (a potential for being alive). However, due to decoherence it does not have a potential for being (dead and alive). What's the difference? Let me give a non-quantum analog from my own experience. When I was a child I have showed some talent for physics and also some talent for arts. But I had to choose only one profession. So I had (a potential to be a physicist) and (a potential to be an artist), but I did not have a potential to be (a physicist and an artist). As you may guess, in actuality I have chosen the former (and never regretted ).

(BTW, does anybody know how to attach a jpg picture which would demonstrate my child artistic talents? I have a scanned version of the picture on my computer, but I don't have an URL.)

Okay, if you are in "edit" mode, there is a button marked "upload". (You might have to first select "More" or "More options" before you get to "upload")

 

[Demystifier]

Yes... That's what I meant. The "post-decoherence" worlds will all have either a live cat or a dead cat. So if I'm understanding you correctly, as with the ensemble interpretation, the concept of a superposed (pure state) live AND dead cat is not really accurate with the MW type of interpretation either.
Before considering "collapse" models, I suppose I should get some clarification on the dBB/pilot wave scenario. My general impression at this point is that this is a deterministic model where the trajectory of the isolated system within the closed box is statistically predicted by quantum mechanics. But here too, the cat inside the closed box might be dead OR alive after the system has decohered, but should not be thought of as being in a superposed pure state of dead AND alive.
Correct?

Correct.

 

[Demystifier]

OK, here I give two of my early artistic works from a dark phase. In one of them you can see an influence of Dali.

 

[Feeble Wonk]

Definite artistic prowess. But.. How old were you? These seem awfully dark for an early life creation.

 

[Demystifier]

Definite artistic prowess. But.. How old were you? These seem awfully dark for an early life creation.

Well, in those works I was not really a child. At that time I was already in high school, meaning old enough to be dark.

I also have some works from a real childhood. They are technically good too, but do not have such an artistic feature. That's why I didn't show them.

Or maybe I should have shown the high-school works from the erotic phase?

 

[Feeble Wonk]

Interesting. Is the second drawing a reflection of "Nature being subjugated by mankind", "Mankind being a slave to its animal instincts"... Or "just a cool drawing"? [emoji848]

 

[Demystifier]

Interesting. Is the second drawing a reflection of "Nature being subjugated by mankind", "Mankind being a slave to its animal instincts"... Or "just a cool drawing"? [emoji848]

The last one.

 

[Feeble Wonk]

The last one.

[emoji106]

 

[Feeble Wonk]

...maybe I should have shown the high-school works from the erotic phase?

"Phase"? Is that supposed to be a phase? [emoji33]

 

[Demystifier]

"Phase"? Is that supposed to be a phase? [emoji33]

I meant in the artistic sense only.

 

[Demystifier]

Anyway, if one forgot what it has to do with the topic, here is a reminder. Decoherence -> MWI -> two very different simultaneous topics of discussion in the same thread. I hope the moderators will accept that argument.

 

[Feeble Wonk]

Anyway, if one forgot what it has to do with the topic, here is a reminder. Decoherence -> MWI -> two very different simultaneous topics of discussion in the same thread. I hope the moderators will accept that argument.

[emoji39] OK. Back to the decoherence discussion...
So, if I've followed you correctly, the three primary "non-collapse" QT interpretation models (ensemble, MW and dBB) view the "cat in the box" as fully decohered into a mixed state (dead OR alive), even from the external perspective. Right?

If so, before considering collapse models, are there any other interpretations (other than your SHV - which I'd like to address later) that might view the isolated system box contents as still being in a "pure" state of superposition (with the cat dead AND alive)?

 

[vanhees71]

Well, one of the topics is totally irrelevant for physics, but that's also something it has in common with the MWI ;-)). SCNR.

 

[Demystifier]

So, if I've followed you correctly, the three primary "non-collapse" QT interpretation models (ensemble, MW and dBB) view the "cat in the box" as fully decohered into a mixed state (dead OR alive), even from the external perspective. Right?

Sort of, but one has to be careful in wording. In MWI there are TWO cats; dead AND alive. But any ONE of them is dead OR alive.

 

[Demystifier]

Well, one of the topics is totally irrelevant for physics, but that's also something it has in common with the MWI ;-)). SCNR.

If physics is really fundamental as physicists like to think that it is, then everything has to do physics.

 

[Demystifier]

If so, before considering collapse models, are there any other interpretations (other than your SHV - which I'd like to address later) that might view the isolated system box contents as still being in a "pure" state of superposition (with the cat dead AND alive)?

Perhaps something like that is valid in quantum logic. Roughly speaking, in quantum logic it is true that
(Cat is dead) AND (cat is alive).
but it is not true that
Cat is (dead and alive).

 

[Feeble Wonk]

Sort of, but one has to be careful in wording. In MWI there are TWO cats; dead AND alive. But any ONE of them is dead OR alive.

Got it. In fact, I presume, there are innumerable cats... all with minuscule quantum differences... but all of them are dead OR alive.

 

[Feeble Wonk]

Perhaps something like that is valid in quantum logic. Roughly speaking, in quantum logic it is true that
(Cat is dead) AND (cat is alive).
but it is not true that
Cat is (dead and alive).

OK. So, I guess this gets us to the general category of collapse interpretations. Conceptually, do you think the various forms of this interpretational genre should be further subdivided to accurately discuss how they view the state of the cat within the isolated system? If so, how and why?

 

[Demystifier]

OK. So, I guess this gets us to the general category of collapse interpretations. Conceptually, do you think the various forms of this interpretational genre should be further subdivided to accurately discuss how they view the state of the cat within the isolated system? If so, how and why?

They can be subdivided according to the cause of collapse (consciousness, stochastic law for all matter, ...), according to the ontology (abstract state $|\psi\rangle$, wave function $\langle x|\psi\rangle$, flashes, ...), etc.

 

[ddd123]

Isn't the "consciousness causes collapse" camp dead today? I only find old speculations by Wigner, but the consensus on the role of consciousness seems shifted towards some aspects of MWI.

 

[Feeble Wonk]

They can be subdivided according to the cause of collapse (consciousness, stochastic law for all matter, ...), according to the ontology (abstract state $|\psi\rangle$, wave function $\langle x|\psi\rangle$, flashes, ...), etc.

And, these collapse theory subdivisions view the state of the cat in the box differently in terms of being pure or mixed (being in true superposition)? If so, could you please offer a brief (conceptual) explanation of why/how?

 

[Feeble Wonk]

Isn't the "consciousness causes collapse" camp dead today? I only find old speculations by Wigner, but the consensus on the role of consciousness seems shifted towards some aspects of MWI.

At this point, I'm not too interested in arguments for or against the interpretational positions, but I'm just looking for a conceptual description of "what" the position is regarding the state of the cat in the isolated system of the box.

 

[Demystifier]

Isn't the "consciousness causes collapse" camp dead today?

It's not very popular, but not disproved either.

 

[Demystifier]

And, these collapse theory subdivisions view the state of the cat in the box differently in terms of being pure or mixed (being in true superposition)? If so, could you please offer a brief (conceptual) explanation of why/how?

They pretty much agree that the cat is not in superposition, except for a very short time which is too short to be measured.

 

[Feeble Wonk]

They pretty much agree that the cat is not in superposition, except for a very short time which is too short to be measured.

OK. So, if I've followed you correctly, regardless of the interpretational perspective, the cat in the box (a completely isolated system) should be thought of as always decohering into a mixed state of dead OR alive, and never really in a pure state of dead AND alive. That makes sense to me.
I suppose the next step for me is to better understand the nature of the "post-decoherence" mixed state. The conceptual difference between a "proper" and an "improper" mixed state remains somewhat fuzzy to me. Is there a decent way of explaining that which doesn't require the use of density matrices?

 

[Demystifier]

The conceptual difference between a "proper" and an "improper" mixed state remains somewhat fuzzy to me. Is there a decent way of explaining that which doesn't require the use of density matrices?

It depends. Can I use pure entangled states such as $|\varphi_1\rangle |\psi_1\rangle + |\varphi_2\rangle |\psi_2\rangle$?

 

[Feeble Wonk]

Well, I'd definitely have a better chance of understanding that than the density matrix explanation... but words would be even better. [emoji849]
I know that's asking a lot, and is likely too limiting for you. Use the mathematical (bra-ket) symbols necessary, and I'll struggle through.