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Panoramic view on the North Campus © Jürgen Huhn​/​TU Dortmund
Manipulation of quantum vacua

Behind the Veil of Nothingness

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Photo of Christoph Lange © Felix Schmale​/​TU Dortmund
Prof. Christoph Lange and his team study custom quantum vacua.
An international research team from Germany and France has created structures in which light fields interact with electrons so strongly that the quantum vacuum itself is significantly altered. Using extremely short bursts of light, they interrupted this coupling much faster than the time scale of a vacuum fluctuation and observed an intriguing ringing of the emitted electromagnetic field, indicating the collapse of the vacuum state. Their key achievement could improve our understanding of the nature of nothingness – the vacuum of space itself, paving a way towards photonics exploiting vacuum fluctuations. The results are published in the current issue of Nature Photonics.

One of the key insights of quantum mechanics is that absolute nothingness, a concept already discussed by Greek philosophers, is nowhere to be found in reality. Quite to the contrary, quantum field theory has shown that seemingly empty space is filled by fluctuations of light and matter fields, leading to a continuous popping into existence and disappearance of photons as well as massive particles. In the founding days of quantum mechanics, these consequences of Heisenberg’s uncertainty principle were often not taken too seriously. However, modern physics is more and more discovering how our universe is shaped by fluctuations of physical fields, which not only lead to tiny shifts of spectral lines of atoms, but moreover may cause the evaporation of black holes, and are ultimately responsible for the large-scale structure of our universe, formed during the inflationary period following the big bang. Yet, controlling these fluctuations on a laboratory scale with the relevant temporal precision has remained extremely challenging to this date.

Specialized semiconductor structures

Researchers around Professor Christoph Lange (Department of Physics, TU Dortmund University), Professor Dominique Bougeard, and Professor Rupert Huber (Department of Physics, University of Regensburg) as well as Professor Cristiano Ciuti (Université de Paris) have now made a large leap towards controlling strongly enhanced vacuum fluctuations much faster than typical time scales of virtual photons. To this end, they created a specialized semiconductor structure in which electrons are extremely strongly coupled to the light fields of tiny antennas designed for the so-called terahertz spectral range. As a result, vacuum fluctuations of light and matter fields participate in the interaction, strongly increasing the presence of virtual photons – even in complete darkness.

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