6,242 research outputs found
The importance of quantum decoherence in brain processes
Based on a calculation of neural decoherence rates, we argue that that the
degrees of freedom of the human brain that relate to cognitive processes should
be thought of as a classical rather than quantum system, i.e., that there is
nothing fundamentally wrong with the current classical approach to neural
network simulations. We find that the decoherence timescales ~10^{-13}-10^{-20}
seconds are typically much shorter than the relevant dynamical timescales
(~0.001-0.1 seconds), both for regular neuron firing and for kink-like
polarization excitations in microtubules. This conclusion disagrees with
suggestions by Penrose and others that the brain acts as a quantum computer,
and that quantum coherence is related to consciousness in a fundamental way.Comment: Minor changes to match accepted PRE version. 15 pages with 5 figs
included. Color figures and links at
http://www.physics.upenn.edu/~max/brain.html or from [email protected].
Physical Review E, in pres
Magnetic Cellular Nonlinear Network with Spin Wave Bus for Image Processing
We describe and analyze a cellular nonlinear network based on magnetic
nanostructures for image processing. The network consists of magneto-electric
cells integrated onto a common ferromagnetic film - spin wave bus. The
magneto-electric cell is an artificial two-phase multiferroic structure
comprising piezoelectric and ferromagnetic materials. A bit of information is
assigned to the cell's magnetic polarization, which can be controlled by the
applied voltage. The information exchange among the cells is via the spin waves
propagating in the spin wave bus. Each cell changes its state as a combined
effect of two: the magneto-electric coupling and the interaction with the spin
waves. The distinct feature of the network with spin wave bus is the ability to
control the inter-cell communication by an external global parameter - magnetic
field. The latter makes possible to realize different image processing
functions on the same template without rewiring or reconfiguration. We present
the results of numerical simulations illustrating image filtering, erosion,
dilation, horizontal and vertical line detection, inversion and edge detection
accomplished on one template by the proper choice of the strength and direction
of the external magnetic field. We also present numerical assets on the major
network parameters such as cell density, power dissipation and functional
throughput, and compare them with the parameters projected for other
nano-architectures such as CMOL-CrossNet, Quantum Dot Cellular Automata, and
Quantum Dot Image Processor. Potentially, the utilization of spin waves
phenomena at the nanometer scale may provide a route to low-power consuming and
functional logic circuits for special task data processing
QED-Cavity model of microtubules implies dissipationless energy transfer and biological quantum teleportation
We refine a QED-cavity model of microtubules (MTs), proposed earlier by two
of the authors (N.E.M. and D.V.N.), and suggest mechanisms for the formation of
biomolecular mesoscopic coherent and/or entangled quantum states, which may
avoid decoherence for times comparable to biological characteristic times. This
refined model predicts dissipationless energy transfer along such "shielded"
macromolecules at near room temperatures as well as quantum teleportation of
states across MTs and perhaps neurons.Comment: 20 pages LATEX, three ps figures incorporate
GaAs optoelectronic neuron arrays
A simple optoelectronic circuit integrated monolithically in GaAs to implement sigmoidal neuron responses is presented. The circuit integrates a light-emitting diode with one or two transistors and one or two photodetectors. The design considerations for building arrays with densities of up to 10^4 cm^-2 are discussed
Neural-Network Approach to Dissipative Quantum Many-Body Dynamics
In experimentally realistic situations, quantum systems are never perfectly
isolated and the coupling to their environment needs to be taken into account.
Often, the effect of the environment can be well approximated by a Markovian
master equation. However, solving this master equation for quantum many-body
systems, becomes exceedingly hard due to the high dimension of the Hilbert
space. Here we present an approach to the effective simulation of the dynamics
of open quantum many-body systems based on machine learning techniques. We
represent the mixed many-body quantum states with neural networks in the form
of restricted Boltzmann machines and derive a variational Monte-Carlo algorithm
for their time evolution and stationary states. We document the accuracy of the
approach with numerical examples for a dissipative spin lattice system
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