Erwin Schrödinger's Cat Redux

So my question is ... so things behave weirdly down at the quantum level. They clearly do not behave that way up at our level. At what point does that phenomenon stop?

No one knows. The Theory of Quantum Mechanics is incomplete. There are two popular interpretations of what might be going on:

1. In the Copenhagen interpretation, a system stops being a mixture of states and becomes one or the other when an observation has taken place. The Cat thought experiment illustrates that it's unclear what exactly an observation is. One could argue the position that while the box is closed, the system exists in a mixed superposition of the states "decayed nucleus/dead cat" and "undecayed nucleus/living cat" and that only when the box is opened and an observation performed does the wave function collapse into one of the two states. This is intuitively absurd, but should we trust our intuition when dealing with the RAM and CPU that we cannot sense? One might think that the "observation" is when a particle from the nucleus hits the detector. However (and this is the point of the thought experiment), there isn't any rule that says one way or the other, and Quantum Mechanics is incomplete without such rules and explanations for how such rules come to exist.


2. In the Everett "many-worlds" interpretation, which does not single out observation as a special process, both states persist, but decohere. When an observer opens the box, he becomes entangled with the cat, so observer-states corresponding to the cat being alive and dead are formed, and each can have no interaction with the other.

Curiously, all of this has some practical use in quantum cryptography. It is possible to send light that is in a mixture of states down a fiber optic cable. If one places a wiretap in the middle of the cable which intercepts the transmission and retransmits it, one conducts an observation which causes the light to fall into one state or another. By doing statistics at the other end of the cable, one can tell if one is received light that is in a mixture of states or if the light has been already observed and retransmitted. This allows one to develop communication systems that cannot be tapped without being noticed at the other end. Of great interest to me personally is this experiment (which one can do) also illustrates that the "observation" in Quantum Mechanics has nothing to do with consciousness in that a perfectly unconscious wiretap will cause the statistics at the end of the wire to be different.

I'll be in Croatia next week - in part presenting cryptography at a conference, but I doubt I will mention this wiretap discovery!

Schrödinger, Erwin! Professor of physics!
Wrote daring equations! Confounded his critics!
(Not bad, eh? Don't worry. This part of the verse
Starts off pretty good, but it gets a lot worse.)
Win saw that the theory that Newton'd invented
By Einstein's discov'ries had been badly dented.
What now? wailed his colleagues. Said Erwin, "Don't panic,
No grease monkey I, but a quantum mechanic.
Consider electrons. Now, these teeny articles
Are sometimes like waves, and then sometimes like particles.
If that's not confusing, the nuclear dance
Of electrons and suchlike is governed by chance!
No sweat, though - my theory permits us to judge
Where some of 'em is and the rest of 'em was."
Not everyone bought this. It threatened to wreck
The comforting linkage of cause and effect.
E'en Einstein had doubts, and so Schrödinger tried
To tell him what Quantum Mechanics implied.
Said Win to Al, "Brother, suppose we've a cat,
And inside a tube we have put that cat at -
Along with a solitaire deck and some Fritos,
A bottle of Night Train, a couple mosquitoes
(Or something else rhyming) and, oh, if you got 'em,
One vial prussic acid, one decaying ottom
Or atom - whatever - but when it emits,
A trigger device blasts the vial into bits
Which snuffs our poor kitty. The odds of this crime
Are 50 to 50 per hour each time.
The cylinder's sealed. The hour's passed away. Is
Our pussy still purring - or pushing up daisies?
Now, *you'd* say the cat either lives or it don't
But Quantum Mechanics is stubborn and won't.
Statistically speaking, the cat (goes the joke),
Is half a cat breathing and half a cat croaked.
To some this may seem a ridiculous split,
But Quantum Mechanics must answer, 'Tough s**t.
We may not know much, but one thing's fo sho':
There's things in the cosmos that we cannot know.
Shine light on electrons - you'll cause them to swerve.
The act of observing disturbs the observed -
Which ruins your test. But then if there's no testing
To see if a particle's moving or resting
Why try to conjecture? Pure useless endeavor!
We know probability - certainty, never.'
The effect of this notion? I very much fear
'Twill make doubtful all things that were formerly clear.
Till soon the cat doctors will say in reports,
'We've just flipped a coin and we've learned he's a corpse.'"
So said Herr Erwin. Quoth Albert, "You're nuts.
God doesn't play dice with universe, putz.
I'll prove it!" he said, and the Lord knows he tried -
In vain - until fin'ly he more or less died.
Win spoke at the funeral: "Listen, dear friends,
Sweet Al was my buddy. I must make amends.
Though he doubted my theory, I'll say of this saint:
Ten-to-one he's in heaven - but five bucks says he ain't."

:-) You may have even sent me that !

Contrary to this ditty, Schrödinger did not intend his thought experiment to indicate that he believed that the dead-alive cat would actually exist; rather he considered the Quantum Mechanical Theory to be incomplete and not representative of reality in this case.

PS. For the path of an object Newtonian Mechanics does work (ie. forces curving the path of a particle in flat space), however The Theory of General Relativity (where the particle is following basically a straight line in curved spacetime) describes the path of the object with a greater degree of accuracy. Not infinite accuracy I might add due to the way the Universe is, a line or a Euclidean point can't actually exist in the real world due to the fuzziness of the place, that fuzziness is what the incomplete Theory of Quantum Mechanics is concerned with.