Hybrid circuits can increase computational power of chaos-based systems

April 28, 2017 by Tracey Peake, North Carolina State University
Two iterations of Tent map for superstable initial conditions. Credit: John F. Lindner

New research from North Carolina State University has found that combining digital and analog components in nonlinear, chaos-based integrated circuits can improve their computational power by enabling processing of a larger number of inputs. This "best of both worlds" approach could lead to circuits that can perform more computations without increasing their physical size.

Computer scientists and designers are struggling to keep up with Moore's law, which states that the number of transistors on an integrated circuit will double every two years in order to meet processing demands. They are rapidly reaching the limits of physics in terms of transistor size - it isn't possible to continue shrinking the transistors to fit more on a chip.

Chaos-based, nonlinear have been proposed as a solution to the problem, as one circuit can perform multiple computations instead of the current "one circuit, one task" design. However, the number of inputs that can be processed in chaos-based computing is limited by , which decreases accuracy. Ambient refers to random signal fluctuations that can be caused by temperature variations, voltage fluctuations or semiconductor defects.

"Noise has always been a big problem in almost all engineering applications including computing devices and communications," says Vivek Kohar, postdoctoral research scholar at NC State and lead author of a paper describing the work. "Our system is nonlinear and so noise can be even more problematic."

To address the problem, the researchers created a hybrid system which uses a digital block of AND gates and an analog nonlinear circuit to distribute the computation between the digital and . The result is an exponential reduction in computational time, which means that the output can be measured while the noise-based deviations are still small. In short, the computations are performed so quickly that noise doesn't have time to affect their accuracy.

To further improve the accuracy, Kohar and his colleagues' proposed solution couples multiple systems. This coupling provides a safety net that reduces the effect of noise-based deviations at the final stage.

"Think about mountaineering," says Kohar. "The climbers can climb individually but if one slips then he/she may have a dangerous fall. So they use ropes to connect them with each other. If one slips, the others will prevent their fall. Our system is somewhat like this, where all the systems are connected with each other all the time.

"The systems are tuned in such a way that at the time of measurement, our is at the maxima or minima - the points where the effects of noise are low in general and much lower if the systems are coupled. Considering the mountaineering example again, this means that we take the averages of climbers when they are at resting locations like the peak or in a valley, where the distances between them are smallest."

The research appears in Physical Review Applied.

Explore further: Reconfigurable chaos-based microchips offer possible solution to Moore's law

More information: Vivek Kohar et al, Implementing Boolean Functions in Hybrid Digital-Analog Systems, Physical Review Applied (2017). DOI: 10.1103/PhysRevApplied.7.044006

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not rated yet Apr 28, 2017
A new approach to central processing will be required as the dimensional limits approach maximum, like super-positioning operations as in quantum circuits, or FM-based parallel processing. Optics will play a role to speed up processing with outrageously fast switching speeds. Still, the computer will always only be as fast a the slowest event in the chain of processes that make it fly.
Da Schneib
not rated yet Apr 28, 2017
This is actually pretty damn interesting. Combining the reliability of digital circuits with the computational potential of analog circuits by using the digital domain to eliminate noise is a real innovation. This approach could also help quantum computer design.
not rated yet Apr 29, 2017
Moore's law, which states that the number of transistors on an integrated circuit will double every two years in order to meet processing demands.

Nope. That's not the Moore's law. Moore's law states the number of transistors of the most cost-effective circuit will double every n years, where n keeps changing depending on who you ask and when, also applying to Moore himself.

Again, every single time they get it wrong.
5 / 5 (1) Apr 29, 2017
Da Schneib, yeah it is. I have been watching the quantum computer progress, and its slow because a universal quantum computer is a heavy lift compared to exploiting limited parts of that behavior in a hybrid machine. Look at what a single photon "computes" in Feynman's path integral formulation of QM. Imagine the cost of doing the same on a computer. So obviously, physics experiments can answer certain queries dramatically faster than computer simulations of them. If you can harnass that, you can do computations faster than a classic computer can without being full quantum computer.
not rated yet May 01, 2017
Analog computers were used before digital ones. For a lot of situations that is still true. Regardless, digital eventually is replacing analog everywhere as long as the digital simulation of analog is fast enough. The possibility of a EAFPA (electronically alterable field programmable array) of this new type circuit could easily make SDR (software defined radio) extremely more efficient. I look forward to more reports on this subject.

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