The worldwide internet traffic produces more CO₂ than all airplanes combined. Computers consume energy because their elements resist the current running through them. They convert electrical energy into waste heat. So unless you use your laptop as an electrical heater, you are wasting energy. If we could make superconducting computers, in which currents keep running without any dissipation, that would be an important step towards a CO₂ neutral world. Leiden physicists Jan Aarts and Kaveh Lahabi perform fundamental research into the memory of such computers. They are now the first ones to have control over the bits of a new type of superconducting memory elements.

Supercurrent

The research group of Aarts generates so-called spin-polarized supercurrents that consist of pairs of two electrons which spin in the same direction. These pairs are called triplets. The physicists research these triplets by combining superconductors and magnets. Earlier, they managed to maintain triplets in their vulnerable state long enough to be applicable in computers. Now they control which path a supercurrent chooses through a memory element.

Bit

The path of the supercurrent acts as a bit in superconducting memory. That is because this path determines the maximum current for which the memory element is still superconducting. The computer reads out a bit by increasing the current until, at maximum supercurrent, it starts to measure a voltage. If this happens at low current, it is a 0, and at higher current it is a 1. The research team’s new design permits even more than two values, with next to zeros and ones also twos and threes. Because the researchers control the supercurrent’s path, they can choose the maximum current, and therefore the value of a bit.

Publication

Kaveh Lahabi, Morten Amundsen, Jabir Ali Ouassou, Ewout Beukers, Menno Pleijster, Jacob Linder, Paul Alkemade & Jan Aarts, 'Controlling supercurrents and their spatial distribution in ferromagnets', Nature Communications