[extropy-chat] Lighting A Quantum Candle On The Nature of Reality

scerir scerir at libero.it
Tue Jul 27 08:15:13 UTC 2004

> Quantum particle entanglement
> is the closest thing to true 
> Harry-Potter-style magic
> we know of today. 
> Any increase in our current 
> paltry knowledge of how this works 
> has the potential to revolutionize 
> our understanding of the nature 
> of reality.

It seems to me that here too (entanglement) is 
going on the old debate about the nature of "psi": 
"it" or "bit"? 

Imagine you have two atoms: A and B, situated in
distant locations, both in an excited state |0>.

These atoms may both decay to the state |1>,
due to spontaneous emission, producing one photon.

An unfocused detector is placed at half way,
between the two atoms. After some time the dectector
clicks. But we cannot distinguish from which atom
the detected photon came.

We have thus produced this atom-entangled state:
|psi> = 2^(-1/2) [|0>_A |1>_B + e^(i phi)|1>_A |0>_B]
where phi is a fixed phase. (Atoms are entangled here,
not photons).

The point here is the impossibility to determine which
atom emitted the photon ("indistinguishability"). 
Actually the production of entangled states not just 
during emissions, but also during detections is possible, 
even usual now.

So, as you can see from the above, "entanglement"
is more on the "bit" side, than on the "it" side.


"A quantum possibility is more real 
than a classical possibility, 
but less real than a classical reality." 
- Boris Tsilerson 

"It has been argued that quantum mechanics
is not locally causal and cannot be embedded
in a locally causal theory. That conclusion
depends on treating certain experimental parameters,
typically the orientations of polarization filters,
as free variables. But it might be that this apparent
freedom is illusory. Perhaps experimental parameters
and experimental results are both consequences,
or partially so, of some common hidden mechanism.
Then the apparent non-locality could be simulated."
- John Bell, "Free Variables and Local Causality",
  'Epistemological Letters', 15, (1977)

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