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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, 

Cite this paper for:

  • Quantum effects on Brain activity
  • Quantum Computation and Neural Computation
  • Penrose�HameroffOrch 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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