What are practical applications?
The diverse properties of Rydberg atoms open up a whole range of applications, from sensors to optical and quantum computers. Some of them are already quite developed. The outermost electron of a Rydberg atom resembles a silk ribbon, which can pick up the slightest movement of air. It can be used for the most sensitive measurements. Individual light particles, for example, cannot be detected without destroying them. The Rydberg atom, however, measures the photon with extreme delicacy. This allows non-destructive detection.Even the finest traces of gases could be detected, such as nitrogen oxides. This is what physicists in Stuttgart are hoping to achieve by turning nitric oxide molecules into Rydberg molecules. These molecules measurably change the current flow through a gas cell, even in the smallest concentration. Such gas sensors will be sensitive enough to detect even the tiniest concentrations of nitric oxide in the air and so find signs of illness.
Another perspective is quantum technology. This uses the bizarre laws of quantum physics to send messages which cannot be eavesdropped on or to solve certain tasks faster than is remotely possible for any ordinary computer. This requires control over individual particles such as atoms or photons. For example, switches that trigger the emission of a single light particle are crucial. With the help of Rydberg atoms, this is possible not only, as previously, at very low temperatures, but even at room temperature. For optical computers or quantum computers, on the other hand, individual photons need to interact with each other in order to perform logical operations. However, light particles "ignore" each other under normal circumstances. But if one photon puts an atom into the Rydberg state, then another photon in the neighbourhood can no longer do so. This indirectly creates the desired interaction. Physicists in Stuttgart are in the process of implementing this principle in semiconductors as well, which could ultimately lead to an optical transistor similar to existing semiconductor components.
Text: Christian Meier. Translation: Kern Group.