
#1
Jun2111, 05:04 PM

P: 91

I'm not good in quantum but i heard about this cause (cat) what happen to this cat
and why he use cat although quantum used for microscopy system ? 



#2
Jun2111, 05:29 PM

P: 113

The cat is in a box with a gieger counter. If normal quantum effects (such as a wave function) governs macroscopic systems, then if the geiger counter releases a poisenous gas, is the cat dead or alive? Quantum theory (old quantum theory) would say that the cat is both dead and alive becuase no one has made a weak measurement (observation) on the cat. But decoherence is relatively new concept which was recenently proven in 1996 by Alain aspect that particles in large enough groups begin to decohere, and quantum eigenstates appear. The cat will be dead if the gas goes off, no denying it  macroscopic systems like cats are not in superpositions.... these are quantum effects being badly applied to the world at large that we deal with every day.




#3
Jun2111, 06:02 PM

PF Gold
P: 11,011

Just in case you didn't know, Schrodingers Cat is simply a thought experiment. It didn't actually happen.




#4
Jun2311, 04:24 PM

P: 91

What is Schrodinger cat?
thank you very much




#5
Jun2411, 02:09 AM

P: 15

Correct me if I'm wrong, but this thought experiment is still a good illustration of the unsolved 'Measurement Problem' in QM
in principle, if you work out all the math using QM to describe the cat's fate, you will get an 'answer' consisting of two components, 'Alive Cat and Dead Cat' (even considering decoherence). Various interpretations of QM then 'trim down' this dual result into only one of its components, for instance by saying that they are actually random probabilities, or that both outcomes occur in parallel realities. 



#7
Jun2411, 05:30 AM

P: 3,178

Thus Schrodinger explained: http://en.wikipedia.org/wiki/Schr%C3%B6dinger%27s_cat 



#8
Jun2411, 06:18 AM

HW Helper
P: 3,337

Yeah, whether state reduction happens at the cat depends on your interpretation of quantum mechanics.
I personally think that state reduction happens at any classical object, so the cat wouldn't be a superposition of dead and alive. But there are other interpretations which would say the cat was a superposition of alive and dead (for example manyworlds interpretation). 



#9
Jun2411, 04:31 PM

P: 113





#10
Jun2411, 04:35 PM

P: 113





#11
Jun2411, 04:59 PM

P: 15

For example, from Wikipedia: "The measurement problem in quantum mechanics is the unresolved problem of how (or if) wavefunction collapse occurs. The inability to observe this process directly has given rise to different interpretations of quantum mechanics, and poses a key set of questions that each interpretation must answer." from http://en.wikipedia.org/wiki/Measurement_problem Brian Greene also says something similar in Fabric of the Cosmos if I recall correctly; decoherence alone does not even really address the fundamental measurement problem. 



#12
Jun2411, 05:19 PM

P: 113




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