Scientists from the universities of Würzburg and Bielefeld discover the quantum properties of the optical-electronic oscillations at the nanoscale. The results can contribute to the development of new computer chips.
Whether the lights in our homes are turned on or off in everyday life can be regulated just by reaching for the switch. However, when the space for light is reduced to a few nanometers, the effect of quantum mechanics is controlled and it is not known whether there is light or not. Both may be the case at the same time, as scientists from the Julius-Maximilians-Universität Würzburg (JMU) and the University of Bielefeld show in the journal “Nature Physics”.
“Exploring these special conditions of quantum physics at the level of electronic transistors can help to develop optical technology for future computer chips,” explains Würzburg professor Bert Hecht. The studied nano structures were made in his group. The technology of our digital world is based on the principle of current going or not: one or zero, on or off. Two clear states exist. In quantum physics, on the other hand, it is possible to ignore this principle and create arbitrary limits that are thought to be counter intuitive. This increases the possibility of transmission and processing of information. Such superposition states have been known for some time, especially for light particles, called photons, and are used in the detection of gravitational waves.
Quantum states detected
A team of physicists and physical chemists from Bielefeld and Würzburg has now succeeded in detecting such superposition states of light directly in a nanostructure. Light in the nanostructure is trapped in small spaces and associated with electronic oscillations: plasmons. This allows energy to be captured at the nanoscale.
In the experiments of the group of Würzburg professor Tobias Brixner, who conducts research to study how many photons of a light pulse couple in the nanostructure. Result: simultaneously no photon and three photons! Brixner explains: “Identifying this signature was a big challenge. Photons can be detected effectively by detectors; However, in the case of a single photon, which also exists in the context of quantum mechanical superposition, the appropriate methods do not exist in the nanoworld. Also, the combined states of photons and electrons live less than a millionth of a millionth of a second and then decay again, leaving little time for their detection.
Better combined spatial and temporal resolution
In the experiments published so far, special investigations are used. “The energy released during the decay of the state is enough to release electrons again from the nanostructure,” explains Professor Walter Pfeiffer (Bielefeld), who plays an important role in the development of the physical model and the definition of data. These excited electrons can be captured and imaged using a photo emission electron microscope with a resolution of a few nanometers. Because of the fast decay time, a series of ultrashort laser pulses is used to create a high-resolution “fingerprint”.
This is the first step towards the goal of investigating the full physical state of the photons and electrons associated with them at the nanometer scale. The procedure, as in medicine, is explained by the word tomography. The lights in the offices and laboratories of the scientists involved will continue to shine brightly.
