Help with Cat in a box

Question

NOTE: I have no/very little knowledge of quantum physics.

With Schroedinger's cat, how is the cat is in both a state of dead and alive at the same time, even though we know it went in alive and died at some point whilst within (or stayed alive depending on the outcome?)

Why does it have to be in a dead/alive state before we know? If it was a human in a box would the paradox be eliminated because it's a human acknowledging "I'm dead now for sure"?

Just because there's no evidence of an outcome to the person conducting the experiment doesn't mean one hasn't happened.

Answer 1

The Copenhagen Interpretation of quantum mechanics suggests that an observer must interact with a quantum system to make an observation or obtain a measurement. This interpretation provides a starting point for an explanation to your question.

In interacting with a quantum system an observer, collapses the wave function of the system and makes and observation of an unrepeatable result. Quantum mechanics only allows the calculation of a probabilistic or expectation value for a result. Thus, the result of an observation is not known until the observer collapses the wave function of the quantum system and obtains an expectation result. Hence, the cat in the box is 'philosophically' superimposed in a wave function state of both being dead and at the same time alive. It is only when the observer opens the box and collapses the wave function that the cat may be seen to be one or the other. Wikipedia adds, 'Schrödinger's cat, often described as a paradox, is a thought experiment devised by Austrian physicist Erwin Schrödinger in 1935. It illustrates what he saw as the problem of the Copenhagen interpretation of quantum mechanics being applied to everyday objects, by considering the example of a cat that may be either alive or dead, according to an earlier random event.'

Arguments such as the above have perplexed philosophers and scientists a like since the emergence of quantum theory during the nineteen-twenties!

Try: -

http://en.wikipedia.org/wiki/Copenhagen_...

For more details.

Answer 2

That's just one way Quantum Mechanics can be interpreted. Interpretations cannot be proved one way or the other. If they could, they would not be called interpretations; they would be theories. You, however, seem to be of a mindset that if there is no evidence for an outcome, you can believe anything that makes you feel the world is the way it should be based on your intuition. Good luck with that.

Answer 3

As vilhelm says, this paradoxical thought experiment was originally written by Erwin Schroedinger to illuminate the absurdity of the quantum ideas. Specifically the the EPR document, the Einstein-Podolsky-Rosen paper which explored the ideas of the Copenhagen interpretation.

The Copenhagen interpretation, produced by Bohr, Heisenberg and others, is that an atom or system can be described by a wavelength and that in fact every particle is a wavelength until they are 'measured' by, for example measuring its momentum which collapses the wave pattern and the wave becomes a particle. A very good example of this is light: it travels as a wave (as demonstrated by the diffraction of light in a prism) but arrives as a particle (a photon) when it strikes, for example, a photoluminescent screen. This duality of states can be seen in the quantum Young double slit experiment (see references).

Schroedinger took the idea that every atom in a 'system' of interlinked particles will only assume a fixed position at a time of quantum measurement and applied it to a complete object - in this example a cat - and 'entangled' its fate with that of a quantum object.

In the original example this was a piece of radioactive material that could potentially decay simultaneously (eg. an single atom of a radioactive material) or not at all. This radiocative material is attached to a geiger tube that, on detecting its decay, is connected to a 'diabolical mechanism' which kills the cat.

This is where the problems begin: the atom itself can be in a quantum 'superposition of states' - i.e. decayed and not decayed - because the state has not been observed by any means. However, as the cat's fate is inextricably linked to the state of the particle it also enters the superposition also. So while in reality the cat is dead or alive, in quantum terms it is both - at least until the state of the radioactive atom has been determined by outside interference. This is the point of Schroedinger's critique: in real terms the idea of entangled wave-function is rediculous, although it seems to have been demonstrated in some circumstances.

Message my profile if you want more info. I hope this is a satisfactory explanation.

Answer 4

Read:

The important point is that it was used to illustrate the problems with a particular interpretation of QM, not so much as an illustration of QM.