On 9/25/2012 12:25 AM, smi...@zonnet.nl wrote:
Citeren meekerdb <meeke...@verizon.net>:

On 9/24/2012 8:57 PM, Stephen P. King wrote:
On 9/24/2012 11:17 PM, meekerdb wrote:
On 9/24/2012 8:02 PM, smi...@zonnet.nl wrote:
Citeren meekerdb <meeke...@verizon.net>:

On 9/24/2012 9:28 AM, Stephen P. King wrote:
On 9/24/2012 12:02 PM, John Clark wrote:
Thus the moon does not exist when you are not looking at it.
Hi John,

I expected better from you! This quip is based on the premise that "you" are the only observer involved. Such nonsense! Considering that there are a HUGE number of observers of the moon, the effects of the observations of any one is negligible. If none of them measure the presence of the moon or its effects, then the existence of the moon becomes pure the object of speculation. Note that being affected by the moon in terms of tidal effects is a measurement!

So who or what counts as an observer. Young's slit experiments on fullerenes seem to indicate that a few IR photons or gas molecules qualify.



If I don't observe it, then it doesn't matter who/what else observes something, the rest of the universe is still a superposition. It doesn't matter whether or not an interference pattern can be detected.

?? I could matter. Suppose I bet you $100 there's no interference pattern when the buckyballs are hot? Then it would matter. But apparently it wouldn't matter whether anyone observed the IR photons or not.


Hi Brent,

If we are consistent with the rules of QM, the mere possibility of detection of position basis information is sufficient to prevent the interference pattern. Thus my prediction is that the temperature of the buckyballs is irrelevant for the two slit experiment, so long as a position basis measurement is not possible. Very hard to do...

No, the temperature is crucial and proves your point. When the buckyballs are cold they form an interference pattern. When they are hot, they don't - because they are hot enough to emit enough IR photons on their way through the apparatus to localize themselves, even though nobody and no instruments are recording the IR photons.

It might be interesting to do this experiment out in space where there are no walls or anything else to absorb the IR photons, but I think the outcome would be the same. Just the photons and their eventual interactions with the vacuum would be enough to produce decoherence.


Note that in such experiments, you can restore the interference pattern by measuring the photons. The photons are entangled with the buckyballs, the reason why you don't get a itnerference pattern is simply because the state of the phtons conain the information about the which way path of the buckballs. Then to restore the interference pattern, all you need to do is look at those buckballs hitting the sceen for which the photon is detected in some fixed state X. Then as a function X, the interference pattern changes, if you average over the range of states X can be in, the interference patten will be completely washed out.

This shows that there is still an interference pattern to be detected (at least in princicple), decoherence is nothing more than the state getting entangled with more and more degrees of freedom.


Hi Saibal,

You remark implies that decoherence is just a measure of the difficulty of recovering information required to reconstruct the initial state, no? It never actually vanishes. This seems to imply a possible lowest upper bound on the number of degrees of freedom involved such that below it interference effects can still be recovered. This seems somehow wrong...




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