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Vibrations in emptiness



  ** Vibrations in emptiness
Vacuum fluctuations of an electromagnetic field (color lines) can be measured due to their effect on two laser beams (red) that propagate through a crystal. Credit: ETH Zurich
In quantum physics, the vacuum is not empty, but rather full of tiny fluctuations in the electromagnetic field. Until recently, it was impossible to directly study these fluctuations of the vacuum. Researchers at ETH Zurich have developed a method that allows detailed description of oscillations.
The void is not really empty ̵
1; not by the laws of quantum physics. The vacuum, in which classically "nothing" is assumed, causes so-called vacuum fluctuations in quantum mechanics. This is a small excursion to the electromagnetic field, for example, that on average, to zero over time, but may deviate from it for a short time. Jerome Feist, a professor at the ETQ Institute of Quantum Electronics in Zurich, and his staff for the first time succeeded in characterizing these vacuum fluctuations directly.

"Electromagnetic field vacuum fluctuations have clear visible effects, and other things responsible for the fact that the atom can spontaneously radiate light," explains Ileana-Christine Benae-Helmus, recently graduated from a PhD thesis. The Faissing Lab and the first author of the study recently published in the scientific journal Nature . "Measuring them directly, however, seems impossible at first glance. Traditional light detectors, such as photodiodes, are based on the principle that light particles – and, therefore, energy – are absorbed by the detector. the energy state of the physical system, it is impossible to extract extra energy. Electrooptical Detection

Fayst and his colleagues decided to measure the electric field of fluctuations directly. To this end, they used a detector based on the so-called electro-optical effect. The detector consists of a crystal in which the polarization (ie, the direction of oscillation, that is) of a light wave can be rotated by an electric field – for example, the electric field of vacuum oscillations. Thus, such an electric field leaves a visible label in the form of a modified polarization direction of the light wave. Two very short laser pulses lasting a fraction of a thousandth of a billionth of a second are sent through a crystal at two different points and at a different time, and then their polarization is measured. From these measurements, finally, one can calculate the spatial and temporal correlations between the instantaneous electric fields of the crystal.

To verify that the measured electric fields in this way actually arise from the fluctuations of the vacuum, and not from the thermal radiation of the black body, the researchers cooled the entire apparatus to -269 degrees Celsius. At such low temperatures, in essence, no photons of thermal radiation remain inside the apparatus, so that any fluctuations of the remaining electric field must come from vacuum. "However, the measured signal is absolutely tiny," ETH professor Faist admits, "and we really had the maximum of our experimental capabilities to measure very small fields." According to Fiesta, another problem is that the frequencies of electromagnetic oscillations, measured with the help of an electro-optical detector, lie in the terahertz range, that is, about a few thousand billionths of a second. In its experiment, the ETH scientist was still able to measure quantum fields with a resolution below the cycle of light oscillations in both time and space

Measurement of exotic oscillations of the vacuum

which in the future they will be able to measure even more exotic cases of fluctuations of vacuum, using their method. In the presence of strong interactions between the photons and the substance that can be achieved, for example, within the optical cavities, according to theoretical calculations, the vacuum should be filled with a set of so-called virtual photons. The method developed by the Faist and his collaborators should allow the verification of these theoretical predictions.


The research group states that it directly selected the fluctuations of the vacuum of the electric field


Additional information:
Moskalenko and others Correlation is detected in a quantum vacuum, Nature (2019). DOI: 10,1038 / d41586-019-01083-z

Ileana-Cristina Benea-Chelmus et al. Correlation measurements of the electric field on the state of electromagnetic vacuum, Nature (2019). DOI: 10.1038 / s41586-019-1083-9

Citation :
Fluctuations in emptiness (April 2019, April 11)
restored on April 11, 2019
from https://phys.org/news/2019-04-fluctuations-void.html

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