18,696 research outputs found
Towards Physarum Binary Adders
Plasmodium of \emph{Physarum polycephalum} is a single cell visible by
unaided eye. The plasmodium's foraging behaviour is interpreted in terms of
computation. Input data is a configuration of nutrients, result of computation
is a network of plasmodium's cytoplasmic tubes spanning sources of nutrients.
Tsuda et al (2004) experimentally demonstrated that basic logical gates can be
implemented in foraging behaviour of the plasmodium. We simplify the original
designs of the gates and show --- in computer models --- that the plasmodium is
capable for computation of two-input two-output gate and
three-input two-output . We assemble the
gates in a binary one-bit adder and demonstrate validity of the design using
computer simulation.Comment: Biosystems (2010), in press. Please download final version of the
paper from the Publishers's sit
Quantum Information Processing with Ferroelectrically Coupled Quantum Dots
I describe a proposal to construct a quantum information processor using
ferroelectrically coupled Ge/Si quantum dots. The spin of single electrons form
the fundamental qubits. Small (<10 nm diameter) Ge quantum dots are optically
excited to create spin polarized electrons in Si. The static polarization of an
epitaxial ferroelectric thin film confines electrons laterally in the
semiconductor; spin interactions between nearest neighbor electrons are
mediated by the nonlinear process of optical rectification. Single qubit
operations are achieved through "g-factor engineering" in the Ge/Si structures;
spin-spin interactions occur through Heisenberg exchange, controlled by
ferroelectric gates. A method for reading out the final state, while required
for quantum computing, is not described; electronic approaches involving single
electron transistors may prove fruitful in satisfying this requirement.Comment: 10 pages, 3 figure
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