The Westflische Wilhelms-Universitt Mnster.

Researchers control individual light quanta at very high speed
A focused laserbeam (left, blue) generates single photos by a single quantum dot inside the photonic waveguides (red), which are fabricated on top of crystalline gallium arsenide- (GaAs-) aluminium gallium arsenide (Al0.2Ga0.8As).Two interdigitating electrodes (interdigital transducers, IDT) generate nanoscale soundwaves (surface acoustic waves, SAWs), which dynamically strain the waveguides. The nanoscale soundwave generated by the left IDT switches the color of the emitted single photons. The two waveguides are coupled by two so-called multimode interference beamsplitters (MMIs). The soundwave generated by the right IDT sorts the single photons according to their colour (red and green) between the two outputs on the right. Credit: Dominik Bühler

A group of researchers from Germany and Spain succeeded in controlling individual light quanta to a high degree of precision. The researchers report in Nature Communications how they use sound waves to switch individual frequencies on a chip. For the first time, this method can be used for acoustic quantum technology.

Modern communication uses light waves and sound waves. While glass fibers with laser light form the World Wide Web, nanoscale sound waves on chips process signals at gigahertz frequencies. How these technologies can be extended to quantum systems is one of the most pressing questions for the future.

The leader of the study in Mnster and Augsburg says that light quanta plays a big part in the development of quantum technologies. He says that the team has succeeded in generating individual photons on a chip the size of a thumbnail and then controlling them with unprecedented precision.

The functional principle of the chip was known to us, but now, using light quanta, we have succeeded in making the long-awaited breakthrough.

The researchers fabricated a chip which has conducting paths for light quanta. These are much thinner than human hair. The chip contained quantum dots.

The quantum dots, just a few nanometers in size, are islands inside the waveguides which emit light as individual photons. We don't have to use complicated methods to generate individual photons because the quantum dots are in our chip.

Dr. Bhler points out that the quantum chips can be switched between two outputs in less than a second.

The researchers consider their results to be a milestone on the way to hybrid quantum technologies as they combine three different quantum systems. The research team had high expectations for the hybrid quantum chips, but they exceeded them.

The international team is moving towards acoustic quantum technologies. "We are working to enhance our chip so that we can program the quantum state of the photon as we wish, or even control several photon with different colors between four or more outputs," says Dr. Mauricio de Lima, with a view to the future.

The strength of the sound waves on the surface of the chip makes it possible for us to control almost as many waveguides as we want.

There is more information about On-chip generation and dynamic piezo-optomechanical rotation.

Journal information: Nature Communications

It was provided by Westflische Wilhelms-Universitt Mnster.