MMM-Intermag 2010

Javier Pulecio and Sanjukta Bhanja, "Magnetic Cellular Automata Coplanar Cross Wire Systems", in MMM-Intermag 2010.

Magnetic Cellular Automata Coplanar Cross-wire Systems (JAP 2010)

J. Pulecio, S. Bhanja, "Magnetic Cellular Automata Coplanar Cross-wire Systems"
AIP ID: 149917JAP
Accepted in Journal: J. Appl. Phys., Ed Code: JR09-3490, 2010.

Abstract:

Quantum Cellular Automata (QCA) has proposed an exclusive architecture, where two coplanar perpendicular wires have the ability to intersect one another without signal degradation. The physical realization of cross wire architectures has yet to be implemented and researchers share concerns over the reliability of such a system. Here we have designed a coplanar cross wire layout for Magnetic Cellular Automata (MCA) and have fabricated two different systems. We have implemented a system containing two ferromagnetic coupled coplanar crossing wires and demonstrate all possible combinations. We have also fabricated a cross wire system consisting of nine junctions and one hundred and twenty single domain nano-magnets. The complex system’s ability to reach an energy minimum combined with the demonstration of all combinations of the smaller system leads us to conclude that a cross wire system is physically feasible and reliable in Magnetic Cellular Automata.

Landauer Clocking for Magnetic Cellular Automata (IEEE TVLSI 2010)

A. Kumari and S. Bhanja, "Landauer Clocking for Magnetic Cellular Automata (MCA) Arrays", Accepted for publication IEEE Transactions on VLSI, 2010.

Abstract:

Magnetic Cellular Automata (MCA) is a variant of Quantum-dot-cellular automata (QCA) where neighboring single-domain nanomagnets (also termed as magnetic cell) process and propagate information (logic 1 or logic 0) through mutual interaction. The attractive nature of this framework is that not only room temperature operations are feasible but also interaction between neighbors is central to information processing as opposed to creating interference. In this work, we explore spatially moving Landauer clocking scheme for MCA arrays (length of eight, sixteen and thirty-two cells) and show the role and effectiveness of the clock in propagating logic signal from input to output without magnetic frustration. Simulation performed in OOMMF suggests that the clocking field is sensitive to scaling, shape and aspect ratio.

Magnetic Cellular Automata

We are interested in Low Energy Computing where computing occurs due to the coupling of the computing elements. In conventional computing, electrons flow from one points to another to process information. In Nano-computing-Resaerch-Group@EE-Univ. of South florida, we pursue a novel cellular automata computing paradigm, where state of the computing elements change and the next computing element couples to the change in the previous computing element and extreme low power dissipation is possible.

We are currently exploring computing with nano-scale soft magnets that are easy to switch, requires no power in the memory state, and can be operated at room temperature. Each magnetic cell is a single domain nano magnet in which all the spins are aligned to one direction. By shape engineering, we can have two dominant state "0" and "1" as shown here. Information processing occurs due to neighbor interactions and there is no physical movement of magnets. In this sense, requirement from Magnetic Cellular automata (MCA) is orthogonal to Magnetic RAM when inter-cell interaction are prohibited. We are however interested in interfacing such systems with MRAM, and sensors providing low energy embedded computing.

In this work, we fabricate nano magnetic structure by E-beam Lithography and observe them qualitatively using Scanning Probe Mucroscope in magnetic mode. So far, varous length of magnetic interconnects, and magnetic crosswires are fabricated.

We have also proposed a spatially moving clocking field for the ordering of the magnets. We are also interested in defect characterization, shape engineering, scaling limits on such devices.

Our recent interest is in creating multi-layer magnetic cells as MQCA elements. We are exploring various clocking and device designs and architectures that can resolve some of the criticism of device integration and low power operation of its previous generation.
We will post a Verilog A model for the cell and architecture shortly once the copyright issues are resolved.

Quantum Cellular Automata

We are interested in Low Energy Computing where computing occurs due to the coupling of the computing elements. In conventional computing, electrons flow from one points to another to process information. In Nano-computing-Resaerch-Group@EE-Univ. of South florida, we pursue a novel cellular automata computing paradigm, where state of the computing elements change and the next computing element couples to the change in the previous computing element and extreme low power dissipation is possible. In Quantum Cellular Automata, each computing cell has four Q-dot and two electrons. Electrons occupy the diagonal Q-dots to minimize the overall energy. Inter-cell barrier confines the electrons in the cell. However, electrons in the neighboring cells allign themselves accroding to the driver cell transfering information. Various cells including a shift register, inverter etc are fabricated and large designs are have been proposed using four phase clocking scheme. We are interested in modeling reliablity, defect, design and power-error trade-offs in Quantum Cellular Automata.

 

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Reliability Analysis for post-CMOS Devices

We work on probabilistic graph structures like Bayesian Networks to model statistical variability of nano-devices. Note that this problem is not new and huge literature exists on"computing with unreliable components" and bounds.

What changed though from before is the phenomenal error rates simply due to extremely low energy computing requirements that random thermal energy can cause temporary errors. We transform the circuit (shown in Figure) into a probabilistic network which in turn is transformed into a junction tree for local computing advantages.

Problems that we intend to look at are

1. Can we arrive at models driven by the underlying Physics of the devices?
2. What would be best heuristics to track worst case scenario?
3. Error/Defect at the boundaries of integration of various devices.
4. Are we heading back to analog? If so, why not use some of the strength?
5. Can we learn structures successfully in inputs and in defects?

Magnetic Cellular Automata Coplanar Cross Wire Systems

J. Pulecio and S.Bhanja,"Magnetic Cellular Automata Coplanar Cross Wire Systems", Accepted to Nano-DDS (Platform paper, oral), 2009.