$9.9million invested into magnetic logic research

The Defense Advanced Research Projects Agency (DARPA) has awarded the funds to a team of researchers, led by Wolfgang Porod, pictured, Freimann Prof of Electrical Engineering and director of the University of Notre Dame's Center for Nano Science and Technology. Porod and Craig Lent, a Freimann Professor of electrical engineering at Notre Dame, have created a transistorless approach to computing called Quantum-Dot Cellular Automata (QCA). The current research, Nano-Magnet logic (NML), is described as magnetic implementation of QCA. Conventional microelectronic technology has relied on shrinking transistors to produce increasingly smaller, faster and more powerful computers. However, because the laws of physics prevent conventional devices from working below a certain size, that method is nearing its physical limits. According to Porod, QCA leapfrogs that barrier with an entity known as a 'quantum dot', a tiny structure in which an electron can be confined. The quantum dots can be created and arranged into cells through microelectronic techniques, and in turn, these cells can be lined up end to end to form binary wires or arrayed to form switches and various computer logic devices. Since it does not rely on flowing electrons to transmit a signal, no electric current is produced and heat problems are avoided. While attempting to implement the original charge based QCA concept, the researchers encountered certain challenges in its applications. Stray charges from the quantum dots presented difficulties and current technological limitations in fabrication meant that QCA operating temperatures had to be extremely low, thereby reducing its practical applications. As an alternative, the team decided to study magnetic systems for QCA implementations. "The basic idea of NML is the same as for the original electronic QCA, except that nanomagnets hold the information and magnetic interactions are used to perform logic," Porod said. "We were quite surprised to learn how strong magnetic interactions are between nanomagnets, which can be fabricated quite easily." Magnets are already being used in memory and data storage, but the Notre Dame team's research demonstrates that nanomagnets can be used for logic functions. "In our opinion, the main significance is the demonstration of logic in a magnetic system, which opens the door to all magnetic information processing systems, including memory and logic," Porod said. "Advantages of nanomagnet logic include room temperature operation, and this technology also leverages advances made by the magnetic storage industry for patterned magnetic media. In addition, NML is non-volatile, which means that the information is not lost when the chip is powered down, offering instant on computers, without the need for lengthy startup procedures when turning the computer on." One of the main advantages of NML is that it requires only low power to operate and a potential application of the magnetic version includes portable systems where power is at a premium. Energy is lost in conventional systems because of the heat generated by the flow of electrical currents, but NML won't have these losses due to the use of magnetic phenomena. This technology may also lead to an all-magnetic information processing system, including memory and logic, which uses little or no electricity. "In the future, we would like to fabricate larger structures, beyond the single majority logic gate demonstrated so far," Porod said. "Also, we would like to realise electronic ways to set the input and to read the output. So far, inputs are set by external magnetic fields."