Computational Paradigms in Nanoelectronics: Quantum Coupled Single Electron Logic and Neuromorphic Networks

We describe a new class of nanoelectronic circuits where circuit functions are derived from cooperative, quantum mechanical interactions between single electrons confined in arrays of quantum dots. Two specific architectures are examined: (i) quantum coupled logic in which Boolean logic functions are implemented by quantum mechanical spin-spin interactions between single electrons in arrays of quantum dots, and (ii) quantum neuromorphic networks that exploit the complex spatial and temporal evolution of discrete charge in an ensemble of non-linearly interacting quantum dots to elicit collective computational behavior. The first class of circuits includes combinational and sequential digital systems. Both logically irreversible elements such as half-adders, S-R flip-flops, shift registers, ring counters, etc., and reversible Feynman gates for quantum computation have been designed in this paradigm. These circuits can be endowed with the required "unidirectional" (non-reciprocal) character that previous (flawed) designs of similar circuits lacked. The second class of circuits comprises discrete Hopfield networks which utilize single electron tunneling events in arrays of metallic islands to perform neuromorphic computation. They can solve NP-complete optimization problems (such as the traveling salesman problem), produce associative memory effects and also exhibit rudimentary image-processing capability.