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Precise mix of light and sound

Scientists from a Polish-German research team from the Technical University of Wrocław, the Universities of Augsburg and Münster as well as Munich have succeeded in creating nanoscale sound waves reported Light quanta to mix. For their research, the results of which have just been published in the renowned journal Optica were published, they used an artificial atom that converts sound wave vibrations into individual light quanta with unprecedented precision. Photons - converts.

Light and sound waves form the basis of modern communication technologies. Light is used to transmit data over the global fiber optic network. And devices that use sound waves are used for wireless communication between routers, tablets or smartphones. These two key technologies must now be adapted to the coming age of quantum communication. So-called hybrid quantum technologies are the key here.

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Hybrid quantum technologies combine light and sound

They combine different ones Quantum systemsby taking advantage of the unique advantages of each system while pushing its limits. Are in this area Crystal lattice vibrations particularly promising, explains Prof. Hubert Krenner, who heads research at the University of Augsburg. He adds that phonons, like physicists, do this vibrations literally stretch and compress every object embedded in the crystal and thus change its physical properties.

In their research, the scientists use surface acoustic waves on the nanometer scale, which are a single artificial atom, a so-called Quantum dotIn our simulations, we were able to reproduce the spectra measured in Augsburg almost perfectly by incorporating nanoscale sound waves into our model, as if it were a phonon laser beam. The presented results are a milestone in the development of hybrid Quantum technologies, because a quantum dot sends individual light quanta, so-called Photons, which are precisely timed by a sound wave, "says a delighted Dr. Daniel Wigger, who as a NAWA-ULAM Fellow at the University of Münster and the Technical University of Wrocław investigates the coupling between quantum dots and phonons.

Dr. Matthias Weiß, on the other hand, who did his doctorate at the Institute for Physics in Augsburg, adds that it is fascinating that the spectral lines of the Quantum dots are so extremely sharp. In this way we could observe how the low energy of a single phonon reduces the Spectral line of a quantum dot, explains Dr. Matthias White.

Smallest portions of energy

The research team has taken another important step forward. The scientists used a second Sound wave with another frequency. New spectral lines appeared in the spectrum of the quantum dot, which correspond to the sum or difference of the frequencies of the two sound waves. Prof. Hubert Krenner notes that this phenomenon has been known as wave mixing in optics for decades.

Laser pointers use this process to generate green light. There are lasers in our work sound wavesthat we are with Light quanta mix, says Prof. Hubert Krenner, who finds the precision of this phenomenon breathtaking.

Dr. Matthias Weiß adds that the scientists when they set the frequency of one of the two sound waves changed by a trillionth, observed that the spectrum oscillates as predicted with a period of about half a day. The quantum dot itself represents the so-called qubit represents, a fundamental unit in quantum computing.

Dr. Daniel Wigger, meanwhile, points out that the researchers the Quantum dot in the model as qubit that is modulated by a sound wave. In addition, they did not have to make any assumptions. The researchers believe that the extraordinary agreement between calculations and experimental results proves that their very general model accurately describes all key properties. It should therefore also apply to many others Qubit implementations be applicable.

Published in Optica