The foundation of current communications technology is made up of light and sound waves. While nanoscale soundwaves on semiconductors process signals at gigahertz frequencies for wireless transmission, glass fibers with laser light create the World Wide Web.
One of the most pressing questions for the future is how these technologies can be extended to quantum systems to build up secure (i.e., tap-free) quantum communication networks.
Light quanta or photons play a very central role in developing quantum technologies.
A team of German and Spanish scientists from Valencia, Münster, Augsburg, Berlin, and Munich has successfully controlled individual light quanta to an extremely high degree of precision. Their study uses a soundwave to switch individual photons on a chip between two outputs at gigahertz frequencies.
This is the first time that scientists have demonstrated a new method that can be used for acoustic quantum technologies or complex integrated photonic networks.
Physicist Prof. Hubert Krenner, who heads the study in Münster and Augsburg, said, “Our team has now succeeded in generating individual photons on a chip the size of a thumbnail and then controlling them with unprecedented precision, precisely clocked by means of soundwaves.”
Dr. Mauricio de Lima, who researches at the University of Valencia and coordinates the work being done there, adds, “The functional principle of our chip was known to us as regards conventional laser light, but now, using light quanta, we have succeeded in making the long-wished-for breakthrough towards quantum technologies.”
In the study, scientists fabricated a chip with minute ‘conducting paths’ for light quanta – so-called waveguides. These are approximately 30 times thinner than human hair. The chip also contains quantum light sources, so-called quantum dots.
Dr. Matthias Weiß from the University of Münster carried out the optical experiments and added: “These quantum dots, just a few nanometres in size, are islands inside the waveguides which emit light as individual photons. The quantum dots are included in our chip, so we don’t have to use complicated methods to generate individual photons by means of another source.”
Dr. Dominik Bühler, who designed the quantum chips as part of his Ph.D. at the University of Valencia, points out how fast the technology is: “By using nanoscale soundwaves, we can directly switch the photons on the chip back and forth between two outputs at an unprecedented speed during their propagation in the waveguides.”
Dr. Mauricio de Lima, with a view to the future, said, “We are already working flat out to enhance our chip so that we can programme the quantum state of the photons as we wish or even control several photons with different colors between four or more outputs.”
Prof. Hubert Krenner adds, “We benefit here from a unique strength which our nanoscale soundwaves have: as these waves propagate virtually loss-free on the surface of the chip, we can neatly control almost as many waveguides as we want with just one single wave – and to an extremely high degree of precision.”
- Dominik D. Bühler, Matthias Weiß, Antonio Crespo-Poveda, Emeline D. S. Nysten, Jonathan J. Finley, Kai Müller, Paulo V. Santos, Mauricio M. de Lima Jr., H. J. Krenner (2022): On-chip generation and dynamic piezo-optomechanical rotation of single photons. Nature Communications 13, DOI: 10.1038/s41467-022-34372-9