Lately, the scientists researching radio frequencies have been focusing on the study of extremely
high frequencies. It is clear to see why: next generations of wireless communication need faster and
faster data transfer, which requires higher radio frequencies. The current 5G technology already
uses frequencies 20 times higher than the ones that our standard WiFi runs on. The plans for 6G and
7G technologies include even higher ones. When we increase the frequency of radio waves, their length
decreases, and it happens that for extremely high frequencies, the waves have a few millimetres, which
is why they are called mmWaves.
The problem with the mmWaves is that they are difficult to measure precisely. Because they have
extremely high frequencies, they oscillate very quickly, and we need very fast equipment to even register
them. What is more, because for mmWave a lot may change at a distance of a few millimetres, all
of the circuits and antennas have to be very carefully and precisely manufactured. It all comes down
to very high costs of all the equipment, and it is viable to look for alternative technologies.
One of the most promising emerging quantum technologies is Rydberg atoms – atoms enlarged and specially prepared
with lasers. They can be very sensitive to radio frequencies, in particular even mmWaves, and because
they are placed in a glass cell, the detectors based on them contain no metal – this is a very different
situation than when standard metallic antennas are used. The Rydberg atoms are so sensitive that
using them, we can observe effects that can be explained only by the laws of quantum physics.
In this project, we want to study how detectors based on Rydberg atoms behave when they are
placed near a resonant structure made for mmWaves, such as an antenna or a resonant cavity. In
particular, cavities seem to be very interesting – they can trap the mmWaves inside, and the Rydberg
detector placed there may register such a trapped wave. It is promising that due to the exceptional
sensitivity, we may count even single photons trapped in a cavity.