An important step towards improved quantum computers

Imagine you’re shown two identical objects and then asked to close your eyes. Open them again, and you see the same two objects. How can you determine if they have been swapped? Intuition and the laws of quantum mechanics agree: If the objects are truly identical, there is no way to tell.

While this sounds like common sense, it actually only applies to our familiar three-dimensional world. If the identical objects are restricted to only move in a two-dimensional (2D) plane, our intuition can sometimes fail. Quantum mechanics allows for something bizarre: in 2D, it has been predicted that special particles, called non-Abelian anyons, exist. In this case, it’s possible to tell that they have been exchanged, despite being indistinguishable.

Researchers had attempted to realize their curious behavior for decades, but until this past fall, no one had succeeded.

First posted in October 2022, our paper “Non-Abelian braiding of graph vertices in a superconducting processor” has now been published in Nature, and so we’re happy to be able to share our peer-reviewed results. In this work, we report that we have observed this non-Abelian exchange behavior for the first time. Non-Abelian anyons could open a new avenue for quantum computation, in which researchers achieve quantum operations by swapping particles around one another, just like strings are swapped around one another to create braids. Realizing this new exchange behavior on our superconducting quantum processor could be an alternate route to so-called topological quantum computation, which is protected from the environmental noise that presents a big challenge in quantum computing efforts today.

For an explanation of exactly how this non-Abelian braiding sequence works — with helpful diagrams that walk you through the process — please read the paper in Nature.