Quantum computers are one of the most important technological breakthroughs of the 21st century.
University of Paderborn Researchers, led by Professor Thomas Zentgraf and in collaboration with colleagues from the Australian National University and Singapore University of Technology and Design, have created a new light manipulation technique that can be used as basis for future optical quantum computers.
The results have now been published in the prestigious professional journal “Nature Photonics.”
New optical elements manipulating light will allow more innovative applications in new information technologies, especially in quantum computers. The non-reciprocal propagation of light via nanostructured surfaces, where these surfaces have been exploited at the microscopic scale, however, remains a significant challenge.
In reciprocal propagation, light can take the same path forward and backward through a structure; however, non-reciprocal propagation is comparable to a one-way street where it can only extend in one direction.
Thomas Zentgraf, Professor, University of Paderborn
Zentgraf was also the head of the working group on ultrafast nanophotonics.
Non-reciprocity is an optical property that causes light to generate different material properties when its direction is reversed. An example of this is a glass window that is transparent on one side and lets light through but acts as a reflective surface on the other side and reflects light. This is called duality.
“In the field of photonics, such duality can be very useful for developing innovative optical elements to manipulate light.“says Zentgraf.
Non-reciprocal propagation of light has been merged with frequency conversion of laser light in an existing partnership between his working group at the University of Paderborn and scientists from the Australian National University and the University of Technology and design from Singapore.
“We used frequency conversion in specially designed structures, with dimensions on the order of a few hundred nanometers, to convert infrared light, invisible to the human eye, into visible light.“, explains Dr. Sergey Kruk, Marie Curie fellow in the Zentgraf group.
Studies have shown that for the nanostructured surface, this transformation process only occurs in one illumination path and is suppressed in the opposite direction of illumination. The duality of frequency conversion characteristics was used to program images into a rather transparent surface.
We have arranged the different nanostructures in such a way that they produce a different image depending on whether the surface of the sample is illuminated from the front or from the back. Images only became visible when we used infrared laser light for illumination.
Thomas Zentgraf, Professor, University of Paderborn
The severity of frequency-converted light in the visible range was still very low in their initial experiments. The next challenge is to increase the efficiency even further so that less infrared light is needed for frequency conversion.
Orientation control for frequency conversion in optically prospective integrated circuits could be used to exchange light directly with new light or to create unique photonic conditions for efficient quantum optical calculations on a small chip.
“Perhaps we will see the application in future optical quantum computers where the directed production of individual photons using frequency conversion plays an important role“says Zentgraf.
Journal reference:
Kruk, SS, et al. (2022) Asymmetric Parametric Image Generation with Nonlinear Dielectric Metasurfaces. Nature Photonics. doi.org/10.1038/s41566-022-01018-7.
Source: https://www.uni-paderborn.de/en/
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