Spin Wave Neuroanalog of von Neumann's Microwave Computer
  Frequency and phase of neural activity play important roles in the behaving brain. The emerging understanding of these roles has been informed by the design of analog devices that have been important to neuroscience, among them the neuroanalog computer developed by O. Schmitt in the 1930's. In the 1950's, J. von Neumann, in a search for high performance computing using microwaves, invented a logic machine based on similar devices, that can perform logic functions including binary arithmetic. Described here is a novel embodiment of his machine using nano-magnetics. The embodiment is based on properties of ferromagnetic thin films that are governed by a nonlinear Schrodinger equation for magnetization in a film. Electrical currents through point contacts on a film create spin torque nano oscillators (STNO) that define the oscillator elements of the system. These oscillators may communicate through directed graphs of electrical connections or by radiation in the form of spin waves. It is shown here how to construct a logic machine using STNO, that this machine can perform several computations simultaneously using multiplexing of inputs, that this system can evaluate iterated logic functions, and that spin waves can communicate frequency, phase and binary information. Neural tissue and the Schmitt, von Neumann and STNO devices share a common bifurcation structure, although these systems operate on vastly different space and time scales. This suggests that neural circuits may be capable of computational functionality described here. 
Frank Hoppensteadt
cs.ET