A New Build Approach For More Efficient Chip Logic Switches

June 22, 2020 by Gary Elinoff

Scientists devise a silicon-compatible method to employ quantum-mechanical “spins” to convey digital information.

Scientists at the Massachusetts Institute of Technology (MIT) and the National Institute of Standards (NIST) have demonstrated a new method based on quantum mechanics to convey digital and analog information. 

Previous approaches have involved elements that could only be built on expensive, exotic substrates. For a first, this new method is built on the same silicon substrates used to fabricate transistors and ICs. It also can take place at room temperature, with no refrigeration required. 

These two vital differences mean that the method is a viable candidate for commercialization. The potential exists for logic, offering very significant advantages to modern-day switches, aka digital logic devices, which depend on power-hungry, heat-generating electron transport.


What are Magnons?

As described by NIST, magnons “are essentially waves that travel through magnetic materials and can carry information.” In this case, the magnetic materials are electrons resident on adjacent atoms, which have a quantum-mechanical property called “spin.” Like the kind of magnets that we are all familiar with, either “north” or “south,” spin is bidirectional and can shift between the two possible orientations.

Spin Waves

Exciting the first electron at the chains represented on the left or right side of the diagram sends a “wave of spin changes traveling downward through the chain,” as described by the NIST article. Which creates a voltage that can be read at the bottom of each chain.

On the left side, the direction of the spins all points in the same direction, resulting in a relatively high voltage read at the bottom. On the right side, the spins from the YIG materials are induced to point in the opposite direction, resulting in a lower voltage read.

The lower voltage corresponds to a “0”, and the higher voltage corresponds to a “1”, duplicating digital logic. As described by Patrick Quarterman, a physicist at the NIST Center for Neutron Research (NCNR), “This is a building block that could pave the way to a new generation of highly efficient computer technology.” 


An artist's conception of the difference between a magnon's open and closed states.

An artist's conception of the difference between a magnon's "open" and "closed" states. Image used courtesy of N. Hanacek/NIST


No Wasted Energy to Generate Troublesome Heat

Today’s computer logic depends on traveling electrons to carry out computations and convey results. This is costly in terms of energy use. Worse, parasitic heat is generated, requiring massive heat sinks that consume board space, and perhaps even fans, which consume more energy.

The electrons that are the heart of this new class of switches are themselves unmoved; only their spins change. The result is that far less heat is generated.

Beyond the Merely Digital

Magnon components can do more than store On or Off, “1” or “0”; they can store analog values such as 0.1, 0.35, or 0.9. As Quarterman puts it, “That’s why we consider this to be more like a valve, you can open or close it a bit at a time.” 

This has an important implication. It takes ten digital switches to store a number ranging from zero to 1024 (210). Little memories with far lower cell counts than today’s devices may eventually be practical, depending on the resolution capability of eventual magnon-based componentry. 


Conserving Power for Wearables and IoT Devices 

Conserving power is of vital concern in electrical engineering today. One reason is to avoid the myriad of problems caused by wasted energy that ends up as heat and the compromises involved in dealing with it. Another is the need to extend battery life for wearables and IoT devices.

Gates based on magnon waves will serve to reduce heat generation in computations and information storage. Recently, we discussed the use of photonics to transfer information internally and between chips as a method to reduce heat and wasted energy. 

Both of these methodologies exhibit significant savings in energy and heat reduction.

Do magnetic waves or photons someday replace moving electrons for computations, storing, and transmitting information? Have electrons, those faithful servants of humankind, outlived their usefulness? If so, will we still call our craft, electronics? Share your thoughts in the comments below.