[ExI] Qualia/Consciousness

scerir scerir at libero.it
Sun Dec 23 10:46:13 UTC 2007

Stefano Vaj:
> And how comes that brains are unable to perform
> quantum computations at all?

For an interesting philosophical discussion
(why evolution did not like the quantum option?)

In general, there is a growing evidence that
'decoherence' - whatever it means - forbids
superposition of quantum states in biological

See also
'Two is a crowd for quantum particles'.
While a single electron will behave as a purely quantum entity, the mere
presence of another electron is enough to cause the electron to make the
transition from quantum to classical behaviour -- according to an
international team of physicists who have done a bizarre yet simple version
of the famous "double slit" experiment. The result could have important
implications for those seeking to create solid-state quantum computing
devices, where minimizing electron-electron interactions is a key challenge
(Science 318 949).
The wave-like, or quantum, behaviour of individual particles is rarely seen
because particles tend to interact with their environment -- for example,
via gravity, electrical interactions or thermal radiation. These
interactions result in a transition from quantum to classical behaviour
called decoherence. Decoherence has been observed in electrons, atoms, small
molecules and more recently in macroscopic objects, such as C60 and C70
All these experiments involve passing the highly isolated particles or
molecules though a double-slit and watching as the interference pattern --
which is a signature of quantum behaviour -- becomes weaker as the particles
interact with their environment.
However, researchers were unsure as to the minimum level of interaction
needed for decoherence to occur. Now, Reinhard Doerner of the University of
Frankfurt in Germany and colleagues have helped answer this question by
studying what they call the "simplest ever double-slit" -- a hydrogen
molecule, which comprises two electrons and two protons.
The researchers began by firing a single high-energy photon at a hydrogen
molecule, which ejects the two electrons from the molecule. One of these
electrons and the two protons form a simple particle/slit system. This
electron forms a quantum interference pattern as it passes through the slit.
The second electron, which moves much slower than the first, acts like a
minimal environment for the other electron. It interacts with the first
electron via Coulomb interactions, leading to a loss of contrast in the
interference fringes observed in the angular distribution of this electron.
The experiment demonstrates that only a very small number of particles is
needed to turn a quantum system into a classical one. "The fragmentation of
the hydrogen molecule is a four-body problem that can also be solved
numerically using today's computers," Doerner told physicsworld.com. "Our
results could now provide a benchmark for some of the most advanced theories
in few body physics."

More information about the extropy-chat mailing list