Need help settling a bet, guys!

[Velocity_Boy]

 

 

Hey all. I need some of physicists who are well-versed (as anyone CAN be in that weird-ass sub-field of Physics) to settle a wage I have with my young nephew. A recent EE grad who fancies himself as an expert in QM. Though I think he drastically over-estimates his prowess in that arena. So here goes...........

 We're talking about Erwin Schroedinger's well-known eponymous "Dead Cat/Live Cat" metaphor. Or thought problem....or hypothetical scenario, or whatever it is. I'm nobody's physicist but I always am forever intrigued with QM and read all I can on it, and thought I was fairly well-acquainted with the paradigm that drives the S's Cat. As you know....the good likens QM's idea of superposition and the notion of a particle being in two states simultaneously to a scenario  of a live cat placed in a steel box along with a steel hammer, some nasty acid, and a trace amount of radioactive substance. And so we have a chance that is this substance decays even a minuscule amount, it could cause a relay to trip the hammer which will break the glass vial and enable the hydrochloric acid to kill the kitty.

 Well....I always thought that ES was just sort of mocking the super-position idea, and basically saying that if we listen to Copenhagen's model, we cannot know for sure WHAT state the particle is in until we look at it. Just like we can't tell about the state of the Cat till that steel box is opened. That BOTH options are valid until observed. But nephew claims it is more than that. Not just the act of observing that stops the guessing and "makes" the particle "settle down" to just one fixed state. No...he says that the electromagnetic energy that is allowed into the heretofore dark box when we open it (photons?) actually causes the cessation of the super-position. And therefore it's not just the idea that we observe it and see what's happening. He claims this whole deal is a metaphor for how observation affects quantum states from breaking open of the closed system (the steel box) that it enjoyed before we disrupted everything.

 Wow...that was a lot harder than I thought it would be--and took longer. Sorry.

So...please tell me I haven't been totally misunderstanding this basic thought problem since I first read it about 20 years ago.

Thanks, as always...for your time and expertise.

VB

Edited May 5, 2018 by Velocity_Boy

[Sensei]

Observer does not have to be human or other living organism. It can be (and often is) machine/device.

Observation does not mean living person is literally looking at event by naked eye. Observation is alternative (misleading?) word for measurement.

 

[swansont]

7 hours ago, Velocity_Boy said:

I always thought that ES was just sort of mocking the super-position idea, and basically saying that if we listen to Copenhagen's model, we cannot know for sure WHAT state the particle is in until we look at it.

Yes, basically.

It doesn't require photons to collapse the wavefunction. They are simply a common tool, since we do so much of our detection via the electromagnetic interaction. Observation does collapse the wavefunction, but "observation" is in one sense a bigger umbrella than that, but one can't use that as the take-away here. If you want to know the state of an atom, you can't just shine any old photon at it, so there are some photons that won't count as an observation, since they can't give you information about the state of the atom. As an example, the box the cat is in isn't "dark" in the sense that there are no photons in there. The cat is absorbing and emitting thermal radiation, which would be in the infrared.  

[Bender]

I would say you both lost the bet.

The illumination of the box is irrelevant. The poison interacts with the air molecules, which interact with the atoms comprising the box, which interact with everything around. Decoherence* of the cat's state happens long before the cat is even dead.

The act of opening the box is of no importance. The only way opening the box could hypothetically matter,  is when the box is entirely isolated, which means not a single particle, photon or other, interacts with the rest of the universe for the complete duration of the experiment. Even in that unlikely scenario, it is unknown whether the cat is simultaneously dead and alive, because we don't know whether there is a limit to the size/complexity of a system to still possibly have superimposed states.

*Decoherence could be wave function "collapse", or the observer and the rest of the universe "joining" the superimposed states (in which case you simultaneously see a living cat and a dead cat ). The distinction is not really relevant for this discussion. 

[swansont]

2 hours ago, Bender said:

I would say you both lost the bet.

The illumination of the box is irrelevant. The poison interacts with the air molecules, which interact with the atoms comprising the box, which interact with everything around. Decoherence* of the cat's state happens long before the cat is even dead.

The act of opening the box is of no importance. The only way opening the box could hypothetically matter,  is when the box is entirely isolated, which means not a single particle, photon or other, interacts with the rest of the universe for the complete duration of the experiment. Even in that unlikely scenario, it is unknown whether the cat is simultaneously dead and alive, because we don't know whether there is a limit to the size/complexity of a system to still possibly have superimposed states.

*Decoherence could be wave function "collapse", or the observer and the rest of the universe "joining" the superimposed states (in which case you simultaneously see a living cat and a dead cat ). The distinction is not really relevant for this discussion. 

Where did Schrödinger propose all of this?

[Bender]

30 minutes ago, swansont said:

Where did Schrödinger propose all of this?

Is that relevant? 

[Mordred]

1 hour ago, Bender said:

Is that relevant? 

of course its relevant

[swansont]

1 hour ago, Bender said:

Is that relevant? 

Yes. The question is about Schrödinger's cat. Not why it doesn't work.

[Velocity_Boy]

4 hours ago, Bender said:

I would say you both lost the bet.

The illumination of the box is irrelevant. The poison interacts with the air molecules, which interact with the atoms comprising the box, which interact with everything around. Decoherence* of the cat's state happens long before the cat is even dead.

The act of opening the box is of no importance. The only way opening the box could hypothetically matter,  is when the box is entirely isolated, which means not a single particle, photon or other, interacts with the rest of the universe for the complete duration of the experiment. Even in that unlikely scenario, it is unknown whether the cat is simultaneously dead and alive, because we don't know whether there is a limit to the size/complexity of a system to still possibly have superimposed states.

*Decoherence could be wave function "collapse", or the observer and the rest of the universe "joining" the superimposed states (in which case you simultaneously see a living cat and a dead cat ). The distinction is not really relevant for this discussion. 

And I'd say you're wrong.

The act of opening the box is the act of observation. Observation tells us the state of the particle in question.

So I think I'm sticking with Swanny's answer about how incoming photons from opening the box don't effect superposition. I think I'm also gonna do some more research. But so far I'm feeling as if I was more on target with the interpretation of S's kitty than was young Alex.

2 hours ago, swansont said:

Where did Schrödinger propose all of this?

I believe it was in Austria in 1935. This Wikipedia blurb is pretty good. At least for us on the laymen level for QM.

 

https://en.m.wikipedia.org/wiki/Schrödinger's_cat

[Bender]

8 hours ago, swansont said:

Yes. The question is about Schrödinger's cat. Not why it doesn't work.

The interaction with photons already is not part of the original thought experiment. Infrared radiation inside the box definitely isn't. The question becomes how far you are going to expand on the original.

If the box is inside a perfect vacuum at 0 K, as the experiment suggests, it must be photons who break the superposition.

I hope we can agree that the human observer is irrelevant?

8 hours ago, Velocity_Boy said:

And I'd say you're wrong.

You can argue that my response is not relevant to you (as others have), but to assert that I'm wrong requires more argumentation.  

[swansont]

6 hours ago, Bender said:

The interaction with photons already is not part of the original thought experiment. Infrared radiation inside the box definitely isn't. The question becomes how far you are going to expand on the original.

The act of observing in the original formulation would be via photons. But it wouldn't be the electromagnetic energy, as such, that collapses the wave function. The discussion of thermal photons was offered to rebut that suggestion.

6 hours ago, Bender said:

If the box is inside a perfect vacuum at 0 K, as the experiment suggests, it must be photons who break the superposition.

Not "must" (you can interrogate a state with other interactions, i.e. strong or weak nuclear) and not because of the EM energy.

6 hours ago, Bender said:

You can argue that my response is not relevant to you (as others have), but to assert that I'm wrong requires more argumentation.  

I was arguing the former, not the latter. What you brought up was irrelevant to the formulation of the Schrödinger's cat argument, and the bet that was described.  

[Bender]

4 hours ago, swansont said:

Not "must" (you can interrogate a state with other interactions, i.e. strong or weak nuclear) and not because of the EM energy.

I guess, but that would again expand beyond the original cat in a box, where such would be highly unlikely.

4 hours ago, swansont said:

I was arguing the former, not the latter. What you brought up was irrelevant to the formulation of the Schrödinger's cat argument, and the bet that was described.

Velocity_Boy argued the latter. You are among the "others" between parentheses.

[swansont]

5 minutes ago, Bender said:

Velocity_Boy argued the latter. You are among the "others" between parentheses.

Sorry. The quote function mashes the whole response together, and I mistook it as being part of what was directed at me.

[Bender]

3 hours ago, swansont said:

Sorry. The quote function mashes the whole response together, and I mistook it as being part of what was directed at me.

No problem.

[Higg’s White Hole]

On 6/23/2018 at 7:17 AM, StringJunky said:

Maths describes the answer, It is not the source of the answer itself. Apparently, Einstein made that mistake later in life; thinking that the answer was in the maths. One can go too far the  other way from neglecting intuition, imagination etc.

True in many circumstances