Is the Brain a Quantum Computer.pdf

Is the Brain a Quantum Computer? Abninder Litta, Chris Eliasmithb,c, Frederick W. Kroona, Steven Weinsteinb,d, Paul Thagarda,b,e aSchool of Computer Science, University of Waterloo bDepartment of Philosophy, University of Waterloo cDepartment of Systems Design Engineering, University of Waterloo dDepartment of Physics, University of Waterloo eDepartment of Psychology, University of Waterloo Received 16 February 2005; received in revised form 8 July 2005; accepted 18 October 2005 Abstract We argue that computation via quantum mechanical processes is irrelevant to explaining how brains produce thought, contrary to the ongoing speculations of many theorists. First, quantum effects do not have the temporal properties required for neural information processing. Second, there are substantial physical obstacles to any organic instantiation of quantum computation. Third, there is no psychological evidence that such mental phenomena as consciousness and mathematical thinking require explanation via quantum theory. We conclude that understanding brain function is unlikely to require quantum com- putation or similar mechanisms. Keywords: Brain function; Consciousness; Explanation; Neuroscience; Quantum computation 1. Introduction Scientific attempts to understand human thinking have historically drawn on analogies with contemporary technologies, from clockworks to telephone switchboards to digital computers. Today, one of the most exciting emerging technologies is quantum computation, which at- tempts to overcome limitations of classical computers by employing phenomena unique to quantum-level events, such as nonlocal entanglement and superposition. It is therefore not sur- prising that many researchers have conjectured that quantum effects in the brain are crucial for explaining psychological phenomena, including consciousness (e.g., Alfinito Vitiello, 2000; Chrisley, 1997; Hameroff, 1998b; Kak, 1995; Penrose, 1994, 1997). We argue, however, that explaining brain function by