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Litt,
A., Eliasmith, C., Kroon, F.W., Weinstein, S. and Thagard, P. (2006). Is the Brain a Quantum Computer?. Cognitive Science, 30: 593--603.
Author of the
summary: Amir Anvari, 2012, amiraanvari@gmail.com
Cite this paper for:
- Quantum effects on Brain activity
- Quantum Computation and Neural Computation
- Penrose�Hameroff �Orch OR� Model for Brain Function
Given
the exciting new developments in quantum computation technology it is
reasonable to consider the question of whether the brain is a quantum computer,
or whether some questions about consciousness and cognition can be explained in
the quantum computing framework. It is argued here that both of these are
implausible given the current state of knowledge in brain and cognitive
sciences.
A
compelling explanation describes a mechanism that generates the phenomenon in
question. A mechanism is essentially a system of entity and activities that
produce a certain pattern of information. Now just as an explanation of how
birds fly can be carried out using classical mechanics and the structure and
function of the wings without any reference to the atomic bonding properties of
the wings and feathers, it is argued that everything that we might want to
explain about the mind and cognition can be stated independent of the underlying
quantum events.
Three
classes of arguments are presented that raise questions about the relevance of
quantum mechanical processes to explaining how brains operate.
The first of these is the
computational argument. In quantum computing qubits are
used as units of computation. Unlike the bits of classical computers qubits may exist simultaneously as coherent superpositions of 1 and 0, which means that potentially a
quantum computer is capable of solving the problems that are intractable for
classical computers.� There is
substantial evidence that time scales for quantum events in the brain are
not in accord with the temporal requirements for influencing
neural activity.
In other words, quantum events are too fast to be able to influence the neural
firing patterns. Of course it is not argued that the brain activity is
independent of quantum reality but that the quantum-level events do not have
any explanatory relevance. For the general operations of the brain quantum
effects happen on a so low a level that any such fluctuations can be
categorized as noise.
The second
argument is the biological argument. Maintenance of a low temperature and a
high degree of isolation from the environment is an important prerequisite to
prevent decoherence and being able to carry out
computational tasks in quantum computers. This stands in sharp contrast to what
we know about human and animal brains which are warm and wet. Another problem
is that of error correction which is carried out in the brain and while several
neural correlates have been proposed with some empirical evidence to implement
this task, error correction in quantum computers follows a highly complicated
scheme which does not seem to be biologically feasible.
The last
argument is the psychological argument. It could be argued that some class of
psychological phenomena, such as mathematical thinking and conscious
experience, can be explained only in terms of quantum events.� First it is noted that simply theorizing
about the quantum effects in the brain is not enough and empirical evidence is
needed. Second, there is at present no reason not to think that neural
computation is capable of coming up with an adequate explanation regarding
these issues.
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