Understanding the Cat in a Box Paradox

[ZapperZ]

Anyone who has been on PF long enough can testify to the fact that the issue of the "Schrodinger Cat" comes up extremely frequently. Just do a search on that and on superposition of states. The Schrodinger Cat is nothing more than an illustration of the superposition phenomenon in QM. That must always be the starting point, i.e. the superposition principle, and NOT the "cat", which is merely a "visual" example.

I've given, over the years, many references and experiments that clearly illustrates this principle, and it appears that, even with this latest series of necroposting in a very old thread, that maybe the references might come in handy again. So here it is:

These are the papers that clearly show the Schrodinger Cat-type states (alive+dead, and not alive or dead). All the relevant details are there and anyone interested should read them. Also included is the reference to a couple of review articles which are easier to read, and the reference to two Leggett's papers, who was responsible in suggesting this type of experiments using SQUIDs in the first place. Again, the papers have a wealth of citations and references.

The two experiments from Delft and Stony Brook using SQUIDs are:

C.H. van der Wal et al., Science v.290, p.773 (2000).
J.R. Friedman et al., Nature v.406, p.43 (2000).[ArXiv version can be found here]

Don't miss out the two review articles on these:

G. Blatter, Nature v.406, p.25 (2000).
J. Clarke, Science v.299, p.1850 (2003).

However, what I think is more relevant is the paper by Leggett (who, by the way, started it all by proposing the SQUIDs experiment in the first place):

A.J. Leggett "Testing the limits of quantum mechanics: motivation, state of play, prospects", J. Phys. Condens. Matt., v.14, p.415 (2002).

A.J. Leggett "The Quantum Measurement Problem", Science v.307, p.871 (2005).

This paper clearly outlines the so-called "measurement problem" with regards to the Schrodinger Cat-type measurements.

Zz.

 

[klaymen]

Then maybe you shouldn't be making such definitive statement before you understand the physics.

Coin tossing is known to not be a "random" process. We lump our ignorance of the fine details of the mechanics into the randomness. But it is still deterministic, and the physics is there to verify that.

This is NOT the case in quantum mechanics. Even Einstein had tried to include "hidden variables" that so far have no empirical support. So as far as we know, there is no physics on why a measured superposition of state will produce one of the possible outcome. To say otherwise is to make an unsupported speculation.

so because humans have not found any definitive patterns, it means there aren't any?

i'm sorry, the real problem i have with this whole debate is the implication that the human mind has any effect on the time that the cat will be poisoned. i believe it is purely determined by the activating device, whether we understand the physics of it or not.

 

[ZapperZ]

so because humans have not found any definitive patterns, it means there aren't any?

i'm sorry, the real problem i have with this whole debate is the implication that the human mind has any effect on the time that the cat will be poisoned. i believe it is purely determined by the activating device, whether we understand the physics of it or not.

Luckily, physics cannot be challenged simply based on a matter of tastes, or what you find appealing. It can only be challenged either based on logical inconsistencies, or experimental observation, neither of which is something you have offered here.

The principle of superposition is alive and well, both in chemistry and in material science. That's why we have bonding-antibonding states, why NH3 molecule behave as it is, and why the Delft/Stony Brook SQUID experiments detected the coherence gap.

Zz.

 

[lightarrow]

i'm sorry, the real problem i have with this whole debate is the implication that the human mind has any effect on the time that the cat will be poisoned.

But you know that this is just one of the *interpretations* and nothing more than this.

i believe it is purely determined by the activating device, whether we understand the physics of it or not.

Maybe you prefer the line of thought of "decoherence".

 

[Count Iblis]

What about this paradox?

Let |X_r> denote a member of a complete set of states for the cat being alive and |Y_s> a member of a complete set of states for the cat being dead (I know, this is not very rigorous...).

Let Q be some arbitrary mapping of the set of "alive" states into the set of "dead" states, so for any arbitrary |X_r> there exists an s such that Q|X_r> = |Y_s>. We may then choose the labeling of the dead states such that Q|X_r> = |Y_r>. The total number of alive states N will, of course, be much smaller than the total number M of dead states.

Now, consider measuring the observable

A = \sum_{r=1}^{N}\left[|X_r><Y_r| + |Y_r><X_r|\right] +\sum_{r=N+1}^{M}|Y_r><Y_r|