[ExI] The Quantum Zeno effect (was: CQT Researcher)

John Clark jonkc at bellsouth.net
Tue Dec 14 05:36:33 UTC 2010

On Dec 4, 2010, at 1:23 PM, Damien Broderick wrote:

> I had this halfassed idea the other day: a Deutschean shadow-universes intuition that the Quantum Zeno effect might derive from superposed activities in adjacent, only slightly divergent M-W realities

Suppose there were a radioactive atom with a half life of 60 minutes, in Many Worlds one way of looking at it, that's not really correct mathematically but can help getting an intuitive feel of it, is that if you look at it after 60 minutes the universe will have split into 2 with the atom decaying in one and not in the other. If you look after 30 minutes there is a 25% chance it will decay so the universe will have split into 4 with 3 having no decay and one with decay, if you look after another 30 minutes each of those 3 will have split yet again with 3 having no decay and one with decay. If you looked after just a nanosecond one universe will see decay and many billions will not, you can see that the number of Damiens (who splits just like everything else) who see no decay of the atom vastly outnumbers the Damiens that do see decay, and more often you check the larger the outnumbering. There will never be a 0% chance you will see a decay but you can approach it asymptotically if you keep checking on the atom at smaller and smaller time intervals, and this is just what we observe in the Quantum Zeno effect.

Possible objection to the above:

I thought the crown jewel of Many Worlds was that it got rid of the unique status of the observer, doesn't this bring back the mysterious nature of measurement just like in Copenhagen?

Possible retort: 

It's true that the universe splits, and in one a measurement has been made and in the other it has not, but the split was made because there was a change in the universe and a measurement is no different from any other change, and the observer is no different from anything else except that it just happens to be the assembly of atoms that generated the report we are reading in this thought experiment. 

Another objection to the above:

But what does it even mean to say that the universe splits into 4 where 3 were identical and one that was different, if the 3 were identical wouldn't that just be one universe? And when dealing with non-denumerable infinite sets can you really obtain probabilities from counting?

Embarrassing admission:

No you can not and Everett specifically warns us from doing so. He formally derived the same results in a way that was mathematically precise (at every branching point the probabilities always added up to exactly 100% just as it should) but was much less intuitive. So what I said is not true, but there still may be an element of truthiness to it. 

> where intentionally directed activities reinforce or prohibit a certain outcome, unlike ordinary stochastic radioactivity, say, where the "shadow overlaps" in/from nearby worlds are arbitrary.

I don't know what you mean by intentionally. Arbitrary or stochastic stuff is just an effect without a cause, and everything including intentionality happens because of cause and effect or it does not; there are simply no other possibilities.

  John K Clark 

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