Laser for measuring vacuum fluctuations

A new experiment for verifying quantum electrodynamics (QED)
Absolute emptiness - this is how most of us imagine a vacuum. In reality, however, it is filled with a flicker of energy: quantum fluctuations. Experts are currently preparing a laser experiment that will detect these vacuum fluctuations in a novel way, potentially providing clues to new laws of physics. A research team from Helmholtz-Zentrum Dresden-Rosendorf (HZDR) has proposed many suggestions that can be used to conduct experiments more effectively, which increases the chances of success.

Vacuum fluctuations cannot be directly detected, but can have indirect effects, such as by altering the electromagnetic field of small particles. However, it is currently impossible to detect vacuum fluctuations without any particles. If successful, one of the fundamental theories of physics, quantum electrodynamics, can be proven in previously untested fields. However, if such an experiment reveals a deviation from the theory, this would lead to the conclusion that new and previously undiscovered particles have been discovered.

The experimental plan to achieve this goal is part of the Helmholtz International Beamline for Extreme Fields (HIBEF), which is a research consortium led by HZDR at European X-ray free-electron lasers (XFEL) in Hamburg. It’s principle is that ultra-intense laser emits short and intense flashes into an airless pumping stainless steel chamber, among which he should manipulate the vacuum fluctuations in a seemingly magical way of repolarizing the X-ray flash from the European XFEL, rotating it in its oscillation direction. “It's like pushing a transparent plastic ruler between two polarizing filters and then bending it back and forth, "explained theorist Ralf Schützold. “In fact, the way the filters are set is that no light can be emitted from behind them. However, a bended ruler will change the direction of the light so that you can ultimately see something.” In this picture, the ruler will correspond to vacuum fluctuations, and the ultra-intense laser flash will bend them.

The initial concept was to emit only one optical laser flash into the chamber and use special measurement techniques to record whether it changed the polarization of the X-ray flash. The problem is, "The signal may be very weak," Schützold explained. “Perhaps only one out of a trillion X-ray photons has changed its polarization.” However, this may be below the current measurement limit-the technology may only have slipped through cracks. That's why Schützold and his team rely on a variant, that is they not only use one optical laser pulse, but also simultaneously shoot two laser pulses into an airless chamber.

There, two lightning flashes met, so they actually collided. The X-ray pulse should be emitted to this collision point. The decisive factor is that the colliding laser pulse acts similarly to a crystal on the X-ray pulse. Just as X-ray diffraction occurs when passing through ordinary crystals, X-ray pulses should also be deflected by the short-term optical crystals of two colliding laser pulses. This not only changes the polarization of the X-ray pulse, but also causes some deflection," Schützold said. “I hope this combination can increase the chances of actually measuring the effect.” In their work, the team calculated various variants of the angle at which two laser flashes met in the chamber, and which of these variants has been proven to be the best will be shown in the experiment.

In addition, if two flashes of different wavelengths are injected into the chamber rather than two laser flashes of the same color, the prospects can be improved. In this case, the energy of the X-ray flash may also slightly change, which will also contribute to the measurement effect. But this requires high technique and may not be implemented until later," Schützold said.

Currently, Hamburg is undergoing planning, with the first batch of experiments planned to begin in 2024. If they succeed, they can confirm QED again. However, perhaps these experiments will discover deviations from the proven theories. This may be due to previously undiscovered particles, for instance, an ultralight neutrino called axion. “And this," Schutzholder said, " will be a clear sign that there are other previously unknown laws of nature.”

Source: diodelaser net