Superconducting materials contain defects that generate disturbing noise. Today, no one knows for sure exactly what these defects consist of.
– They are atoms or molecules with electric charge that exist in dielectric * materials, on the surface of metals and insulating materials. There is always a thin oxide that forms on the surface, and the oxide is not completely perfect but has defects in it, says Jonas Bylander, associate professor at the Quantum Technology Laboratory at the Department of Microtechnology and Nanoscience.
In the newly published research, Jonas Bylander and his colleagues show how it is possible to reduce the noise in the materials by exposing them to a radio-frequency electric field.
– We discovered that it is the same kind of defects that dominate how well different materials and components work, says Jonas Bylander. And we developed a model that explains in detail what is happening.
The researchers discovered that the defects display so-called "motional narrowing" when they are exposed to the radio-frequency electric field, something that has not been previously detected in dielectric materials. Jonas Bylander compares the effect that occurs with that of reduced motion blur in a photograph.
– One can say that these existing defects can have several different positions, and when the background fluctuates, the defects can jump between these positions. But when we make the background fluctuate faster, the defects do not catch up. The result is that the defects appear to be sitting still. Unintuitively, it’s almost the opposite of motion blur.
The newly published research increases the understanding of how materials used to build superconducting circuits work – when reducing the noise, the components perform better.
– We try to build better components from better materials and design the components so that they are not so sensitive to noise, and if we understand the materials better, we will also be able to build better quantum computers.
Read the scientific article here
* A dielectric material is an electrical insulator that can be polarized by an applied electric field.