Researchers control individual quanta of light at very high speed

Researchers control individual quanta of light at very high speed

A focused laser beam (left, blue) generates single-quantum dot images inside optical waveguides (red), which are synthesized on top of crystalline gallium-(GaAs-) aluminum gallium arsenide (Al0.2Ga0.8As). Interlocking electrodes (interdigital transducers, IDT) generate nanoscale acoustic waves (surface acoustic waves, SAWs), which dynamically strain the waveguides. The nanoacoustic wave generated by the left IDT switches the color of the emitted single photons. The two waveguides are coupled with so-called multi-mode interference beamformers (MMIs). The acoustic wave generated by the right IDT sorts the individual photons according to their color (red and green) between the two outputs on the right. Credit: Dominique Buehler

A team of German and Spanish researchers from Valencia, Münster, Augsburg, Berlin and Munich have succeeded in controlling individual quanta of light with an extremely high degree of precision. in Nature CommunicationsThe researchers report how, using sound waves, they switch individual photons on a chip back and forth between two outputs at gigahertz frequencies. This method, described here for the first time, can now be used for acoustic quantum technologies or complex integrated optical networks.

Light waves and sound waves form the technological backbone of modern communications. While glass fibers and laser light form the World Wide Web, nano-acoustic waves on chips process signals at gigahertz frequencies for wireless transmission between smartphones, tablets or laptops. One of the most pressing questions for the future is how these technologies can be scaled up Quantum systemsto build secure (i.e., click-free) quantum communication networks.

“Light quanta, or photons, play a very central role in the development of quantum technologies,” says physicist Professor Hubert Krener, who heads the study in Münster and Augsburg. “Our team has now succeeded in generating individual photons on a chip the size of a thumbnail and then controlled with unprecedented precision, it is precisely recorded by means of sound waves.”

Dr. Mauricio de Lima, who is researching at the University of Valencia and coordinating the work being done there, adds, “The functional principle of our chips was known to us in relation to conventional laser light, but now, with quantum light, we have succeeded in making the long-awaited breakthrough towards quantum technologies.”

In their study, the researchers made a chip equipped with precise “conductive paths” for light quanta – so-called waveguides. It is 30 times thinner than a human hair. In addition, this chip contains quantum light sources, called quantum dots.

Dr. Matthias Weiss from the University of Münster conducted the optical experiments and added: “These quantum dots, which are only a few nanometers in size, are islands inside the waveguides that emit light as individual photons. Quantum dots are embedded in our chips and so we don’t have to use complicated methods to generate individual photons by remotely.” another source way.

Dominik Buehler, who designed the quantum chips as part of his Ph.D. at the University of Valencia, he notes how fast the technology is: “Using nanoacoustic waves, we can shunt photons directly on the chip back and forth between two outputs at an unprecedented speed as they propagate in waveguides.”

The researchers consider their findings a milestone on their path toward hybrid quantum technologies as they combine three different quantum systems: quantum light sources in the form of quantum dots, optical quanta created, and phonons (quantum particles in the sound wave). Hybrid quantum chips — designed at the University of Valencia and manufactured at the Paul Drude Institute for Solid State Electronics using Quantum dots Produced at the Technical University of Munich – exceeded the expectations that the research team had.

The international team has taken another crucial step toward acoustic quantum technologies. “We are already working fully to improve our chips so that we can program the quantum state of the photons as we wish, or even control several photons of different colors between four or more outputs,” says Dr. Mauricio de Lima. Look into the future.

Professor Hubert Krener adds: “Here we make use of the unique power of our nanoscale acoustic waves: because these waves propagate almost losslessly over the surface of the wafer, we can precisely control as many waveguides as we want with just one wave – and with a high very accurate.”

more information:
Dominic D. Nature Communications (2022). DOI: 10.1038/s41467-022-34372-9

Provided by Westfälische Wilhelms-Universität Münster

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