Physicist develops detector capable of counting photons for quantum computing

This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Detecting a single photon is a challenge in itself. But what if you also want to know exactly how many photons arrive at a particular point at the same time?

Physicist Erik Baalbergen is working on light detectors that can do just that. They form a key building block for the optical quantum computer of the future. "I always enjoyed the experiments with light the most," says Baalbergen.

"And this project brings together the fields of optics, electronics and solid-state physics. It is precisely that intersection that I find incredibly interesting." During his Ph.D. research at Leiden University, he worked on the development and improvement of specialized light detectors. He defended his thesis, "Photon-Number Resolution with Superconducting Nanowires," on November 3.

"We have developed a technique that allows you to distinguish between one, two and three (or more) photons." Baalbergen explains that an optical quantum computer must have a detector capable of counting the exact number of light particles passing through. This is because the computer uses these photons to perform calculations. Until now, detectors could only determine whether light particles were present or not.

Baalbergen says, "Our new detector therefore measures exactly how many light particles there were, and these measurements also provide information on how certain this result is. It may seem like a small step forward, but it is in fact quite a significant, fundamental step forward. Admittedly, our detector still needs further development, but with the path we have now embarked upon, we will get there." Baalbergen investigated extremely thin wires made of a material that exhibits zero electrical resistance at very low temperatures—so-called superconducting nanowire detectors.

As soon as a photon strikes such a wire, its electrical state changes and a measurable signal is generated. One of the technical solutions Baalbergen investigated is a smart connection between the detector and the electronics that read out the signal. This connection ensures that less of the electrical signal is lost.