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To: ETL
Stephen Hawking is famously quoted as saying "When I hear about Schroedinger's cat, I reach for my gun."

Personally, I feel the same way.

The EPR Paradox is not a paradox. It is a rigorously constructed thought experiment, which Einstein, Podolsky and Rosen believed would lead to the overthrow of quantum mechanics when it became clear that real experiments would never verify it. Unfortunately, they were wrong: Quantum Entanglement is real.

Schroedinger's cat is a cat of a different stripe. Frankly, it is not rigorously constructed and a lot of physicists don't see any real issues once you point out the obvious shortcomings. Einstein and Schroedinger actually corresponded over a better version of the paradox which does not involve a cat, but a barrel of dynamite, which, at least in the Copenhagen Interpretation of Quantum mechanics must be partially exploded and partially unexploded until you open the box. It never caught on because nobody cares about a dead physicist who stupidly opens a box containing a mixed superposition barrel of dynamite, just to see if he can project its eigenvector into the right subspace of Hilbert space by inspection, but cats are cute and fluffy.

Removing the cat removes a number of issues, not least of which is that if all that's required is an observer, the cat surely knows if it's alive or dead, which kind of spoils the quantum mechanical surprise when you open the box.

More problematic is the troublesome fact that quantum mechanics requires as one of its axioms that every observable quantity must correspond to a Hermitian operator. Since we don't have a definition of what it means to be "alive" in physics, it's highly unlikely that any such operator even exists. That's a job for biologists, and their definition is suitable for their problem domain, but it's far too "big" to be used in physics any time soon, and is likely to involve more than a single "life operator" anyway.

If there is no such operator, it has no eigenstates either and hence there is no superposition of "live" and "dead" cat states.

Finally, it's been a pretty hot topic of research since the 1980's [although the concept was raised many times in the past in a way that wasn't well articulated] the very notion that there is actually a quantum connection between classical objects [like cats] and quantum mechanical objects [like atoms] in Schroedinger's version of quantum mechanics is far from settled, and that's one of the reasons that in discussing the measurement of quantum systems with classical instrumentation the whole question of quantum coherence and decoherence has become much more interesting.

In response to a two day discussion of the Schroedinger Cat Paradox in the second quantum course in grad school [actually the Measurement Problem in general, which is a much bigger problem, of which Schroedinger's Cat is just an example], one of the students circulated a mimeograph [it's all we had to stand in for the Internet in 1978] mocking the whole thing entitled, Congratulations! You've Created a Machine That Might or Might Not Kill a Cat. Now Get Over It. That pretty much sums up how most physicists I knew felt about Schroedingers G*dd*m cat.

Fortunately, quantum computing in no way relies on the Copenhagen Interpretation or on Schrodinger's cat, whether alive, dead, or in some admixture of the two.

9 posted on 01/18/2014 10:46:25 PM PST by FredZarguna (Das is nicht richtig nur falsch. Das ist nicht einmal falsch.)
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To: FredZarguna
The EPR Paradox is not a paradox. It is a rigorously constructed thought experiment, which Einstein, Podolsky and Rosen believed would lead to the overthrow of quantum mechanics when it became clear that real experiments would never verify it. Unfortunately, they were wrong: Quantum Entanglement is real.

Beat you by 9 x "9192631770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom'..."

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

:)

10 posted on 01/18/2014 10:53:54 PM PST by ETL (ALL (most?) of the Obama-commie connections at my FR Home page: http://www.freerepublic.com/~etl/)
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To: FredZarguna
i always look at the cat as Schroedinger spoofing the concept...

it is NOT dead AND alive, it IS one OR the other, you simply don't know till you open the box

16 posted on 01/19/2014 6:32:07 AM PST by Chode (Stand UP and Be Counted, or line up and be numbered - *DTOM* -vvv- NO Pity for the LAZY - 86-44)
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