Paradox Paradigm

Any time a politician says, "Yes, I'm a Christian [Catholic, Mormon, atheist, Buddhist, etc.], but I don't let that affect my voting," then you be quite sure he (she) doesn't truly believe in anything except obtaining, keeping, and wielding power. This doesn't automatically disqualify the person, who might actually do a good job representing the constituents, purely out of self-interest. But if the electorate relaxes its vigilance, such a person will take full advantage. Given how short the electorate's attention span is, this situation will inevitably occur. Therefore, I never vote for politicians with this kind of "private faith." There is no such thing, not in that sense. On the other hand, it is very different when a candidate says, "Yes, I am a Christian, and it affects every decision I make. But since I'm currently running for political office, let's concentrate right now on my positions and my voting record on the issues at hand."

At the risk of embarassing myself by asking a dumb question: Has anyone ever actually made such an experiment? Not with a cat (I assume), but with some macroscopic object?

I know that people have entangled two photons. In which case, you no longer have two photons (that are entangled). Instead, you have a two-photon entangled state. It is a new thing. So then, the reason God can't know the state of each photon in an entangled pair is not because His knowledge is limited, but because there are NOT two photons any more. So it is not correct to say that you can measure the spin of one electron in the pair and thereby determine the spin of the other electron. Once you get them entangled, all you can do is destroy the entanglement. It is like creating a gamma ray out of an electron and a positron. Once the gamma ray is formed, it is nonsense to ask "what is the spin of the electron?" The electron and the positron are both gone, dude. Non-entities don't have properties. You can call the new entity an electron-positron entangled state instead of a gamma ray, if you want to be complicated. Sooner or later, the gamma ray will interact with matter. It may then decay into an electron-positron pair, with correlated properties. Is this the same pair you started with? Again, a nonsensical question. ALL electrons are the same, except for location, momentum, and spin.

Please correct me if I've gotten something wrong.

The point of the Einstein-Podolsky-Rosen paradox was to show that objects with two, noncommuting properties could be observed pairwise. Recall that Bohr had said that one object with two non-commuting properties could only be fixed in one of those properties because the measurement would ruin the other. (Cop to driver, "excuse me, but do you know how fast you were going?" Heisenberg, "No, but I know exactly where I am.")

EPR pointed out that if a pair of particles which shared a common wavefunction (entangled or coherent) were used, one could measure property 1 on the first guy, and property 2 on the second guy, thereby avoiding Bohr's "instrumentalist" interpretation of QM. E.g., both properties were there, we just didn't have the instruments to measure them both simultaneously.

After thinking about it, Bohr agreed with EPR, abandonning his instrumentalist argument, and embracing full-fledged Copenhagen interpretation, that there was no simultaneous existence of non-commuting properties in QM. Einstein thought that was silly, or at least "incomplete".

So back to your dumb question. No one has used cats, partly because it is mighty hard to get cats to be coherent. But large systems have been made coherent, and non-commuting properties measured, and yes, the entangled state is neither fish nor fowl, but indeterminate. Photons inside Mach-Zender interferometers have been entangled, atoms from Bose-Einstein Condensates, electrons, the spin of hydrogen atoms in a lattice, and the list goes on. Physically, the only difference between these and a cat is about 24 orders of magnitude more atoms (which means the opportunity to detangle or decohere is about 24 orders of magnitude greater, and our cat-tangled state lasts a nano-nano second) but there's no philosophical difference.