Delft scientists have managed to make a superconducting version of a crucial electronic component. Will it, as the research leader claims, lead to computers that run hundreds of times faster than the current ones?

We would like to have electronics that make use of superconductivity: the phenomenon that certain materials no longer have electrical resistance at low temperatures. This would allow you to make circuits much faster and more economical, it is expected.

It’s just a shame that we don’t have a superconducting variant of a diode: a component that conducts current well in one direction, but not in the other direction. As early as the 1970s, IBM realized that this lack was the bottleneck on the road to a computer that works with superconductivity.

Now Delft researchers have succeeded in making such a superconducting diode. An important step towards a computer revolution – or is that too much to say?

Not very practical

The basis of the superconducting diode is a so-called Josephson junction. That is basically a sandwich with two superconductors on the outside and another, non-superconducting material in between.

Normally, such a Josephson junction does not function as a diode, but previous researchers have succeeded in making one out of it. The problem with this was that magnetic fields always had to be used. And that makes such a diode not very practical, explains research leader Mazhar Ali in a press release† “Nanometer-scale magnetic fields are very difficult to control and limit.”

Few atoms thick

Ali and colleagues have now succeeded in doing the same thing without magnetic fields. They have, they write in the scientific journal Naturedeveloped a “field-free Josephson diode”.

The material between the superconductors is crucial. This is not an ‘ordinary’ material, but a so-called quantum material: a compound of niobium and bromine with the chemical formula Nb3bro8† This material has a two-dimensional structure, says Ali, just like the ‘wonder material’ graphene, for example. This allowed the researchers to coat their sandwich with a layer of topping that was only a few atoms thick. And with that, the whole turned out to function as a diode.

Even at higher temperatures?

As for the applications, Ali says: “Technology that was previously only possible with semiconductors can now be made possible with the help of this building block with superconductors.” This also includes computers that are three to four hundred times faster than the computers we use today, he continues.

Now superconductors only work at low temperatures. For example, the superconductor that Ali used in his diode only acquires a resistance of zero at temperatures below -266.55 degrees Celsius. As a next step, the Delft researchers want to see whether they can repeat the same trick with materials that become superconducting at higher temperatures.

But for the time being you are still talking about chips that work at around -200 degrees Celsius. So you will find them sooner in large-scale server farms and in supercomputers, then in your home computer. But Ali does not see that as a major objection. “All intensive calculations are now performed in centralized facilities,” he says. “And the existing infrastructure can be adapted to electronics based on superconducting diodes without too much cost.”

Speculative promises

That sounds like a big step towards much better computers. Is it that too? Not according Bram Nautauniversity professor at the University of Twente and creator of the nauta switch† “It’s nice basic research, and there’s nothing wrong with that, but the promises are very speculative and not based on how computers work,” he says.

“You can’t build computers with diodes,” Nauta continues. “In a computer you need an amplifying element with which you can ‘pimp up’ ones and zeros when they have sunk. You also have to be able to turn a one into a zero. This is not possible with diodes. Moreover, cooling a superconductor consumes an awful lot of energy; much more than you save due to the low losses of a ‘bare’ superconductor.”

In short: nice work, but the picture of the future that Ali paints is perhaps a bit too rosy.