Rydberg atoms-based sensors for microwave fields detection – CARDAMONE

Rydberg atoms have been attracting the attention of scientists for more than 50 years, first as a subject of fundamental research or for the development of quantum simulators, and also recently for their potential as sensors for the detection and imaging of electromagnetic fields. Most of the proposed schemes for the detection of microwave fields are based on the use of the Electromagnetically Induced Transparency (EIT) in a ladder system. In this scheme, if the state of highest energy is a Rydberg state coupled with other states, the EIT phenomenon is perturbed by the RF, which splits this level by Autler-Townes effect. Two EIT resonances are then observed instead of one.
Compared to metallic dipole antennas currently used for this kind of applications, the dielectric cells containing Rydberg atoms at room temperature allow to consider wavelength-independent, precise measurements with a very high sensitivity and dynamics, and with intrinsic stability and self-calibration. In addition, the sensitive part of the sensor is purely dielectric and therefore does not disturb the field to be measured. While this emerging technology is of interest to the United States and China, apart from a need for sovereignty, one challenge is to target applications in which Rydberg atomic sensors will be particularly efficient and thus surpass existing technologies. The CARDAMONE project aims at studying the advantages and limitations of this technology, both from experimental and theoretical points of view, and to propose optical solutions based on modulations of the probe and coupling fields.
One of the most obvious limitations of the present state-of-the art of this technology is indeed imposed by the Rydberg levels used, which can address a frequency range from kHz to THz, but whose discrete nature limits the frequency agility and bandwidth of the device. A second bottleneck concerns the instantaneous measurement bandwidth, which is poorly understood today, as shown by the discrepancies between experimental measurements and theoretical calculations. Finally, the detection of the phase of the RF electric field currently requires the addition of an extra antenna emitting a local oscillator, which can be detrimental to the operation of the antenna.
The objective of the ANR ASTRID CARDAMONE is therefore to develop original modulation architectures for the probe and/or pump beam, in order to be able to adjust the RF detection bandwidth of the system at will, while maintaining an adequate sensitivity, and to measure not only the power of the detected RF radiation, but also its phase. It is thus a question of allowing, in the long term, to respond to the applicative stakes of this study, whether it is for the metrology of radiations from transmitting antennas or for applications such as radar or electronic warfare. The consortium of the CARDAMONE project brings together academic and industrial actors, specialists in quantum physics, optical technologies, as well as applications of RF to radars, electronic warfare and communication systems. This synergy between actors with complementary skills will ensure an efficient transfer of CARDAMONE's results from quantum physics to applications.