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Metrology of microwave fields with cold rydberg atoms

Granier, Romain, Bekai, Anthony, El, Romain Duverger, Quentin Marolleau, Alexis Bonnin, Cédric Blanchard, Nassim Zahzam, Yannick Bidel, Malo Cadoret, Alexandre Bresson, Sylvain Schwartz

Published Apr 28, 2025• 0 citations
OpenAlex

Abstract

Rydberg atoms are highly promising for microwave electric field sensing owing to their large dipole matrix elements. While most experimental developments have focused on room-temperature vapors so far, utilizing cold atoms in this context could open new possibilities for applications where accuracy, long term stability and highresolution at large integration times are required, such as calibrating blackbody shifts in state-of-the-art optical clocks or measuring the cosmic MW background. Here, we report a novel approach [1] for the metrology of microwave fields with cold 87 Rubidium Rydberg atoms based on trap-loss-spectroscopy in a magneto-optical trap (MOT).

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We demonstrate a new approach for the metrology of microwave fields based on the trap-loss spectroscopy of cold Rydberg atoms in a magneto-optical trap. Compared to state-of-the-art sensors using room-temperature vapors, cold atoms allow longer interaction times, better isolation from the environment, and a reduced Doppler effect. Our approach is particularly simple, as the detection relies on fluorescence measurements only. Moreover, our signal is well described by a two-level model across a broad measurement range, allowing one, in principle, to reconstruct the amplitude and the frequency of the microwave field simultaneously without the need for an external reference field. We report on a scale-factor linearity at the percent level and no noticeable drifts over two hours, paving the way for new applications of cold Rydberg atoms in metrology, such as calibrating black-body shifts in state-of-the-art optical clocks, monitoring the Earth's cryosphere from space, measuring the cosmic microwave background, or searching for dark matter.

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Investigation of cold rubidium Rydberg atoms in a magneto-optical trap

Denis B. Tretyakov, Ilya I. Beterov, Vasily M. Entin +2 more

This paper reports on the results of experiments with cold rubidium Rydberg atoms in a magneto-optical trap. The specific feature of the experiments is the excitation of Rydberg atoms in a small volume within a cloud of cold atoms and the sorting of measured signals and spectra according to the number of detected Rydberg atoms. The effective lifetime of the 37 P Rydberg state and its polarizability in a weak electric field are measured. The results obtained are in good agreement with theoretical calculations. It is demonstrated that the localization of the excitation volume in the vicinity of the zero-magnetic-field point makes it possible to improve the spectral resolution and to obtain narrow microwave resonances in Rydberg atoms without switching off the quadrupole magnetic field of the trap. The dependence of the amplitude of dipole-dipole interaction resonances in Rydberg atoms on the number of atoms is measured. This dependence exhibits a linear behavior and agrees with the theory for a weak dipole-dipole interaction.

arXiv:0810.5427•Journal of Experimental and Theoretical Physics•Mar 1, 2009•23 citations
Rydberg atoms are highly promising for microwave electric field sensing owing to their large dipole matrix elements. While most experimental developments have focused on room-temperature vapors so far, utilizing cold atoms in this context could open new possibilities for applications where accuracy, long term stability and highresolution at large integration times are required, such as calibrating blackbody shifts in state-of-the-art optical clocks or measuring the cosmic MW background. Here, we report a novel approach [1] for the metrology of microwave fields with cold 87 Rubidium Rydberg atoms based on trap-loss-spectroscopy in a magneto-optical trap (MOT).
We demonstrate a new approach for the metrology of microwave fields based on the trap-loss spectroscopy of cold Rydberg atoms in a magneto-optical trap. Compared to state-of-the-art sensors using room-temperature vapors, cold atoms allow longer interaction times, better isolation from the environment, and a reduced Doppler effect. Our approach is particularly simple, as the detection relies on fluorescence measurements only. Moreover, our signal is well described by a two-level model across a broad measurement range, allowing one, in principle, to reconstruct the amplitude and the frequency of the microwave field simultaneously without the need for an external reference field. We report on a scale-factor linearity at the percent level and no noticeable drifts over two hours, paving the way for new applications of cold Rydberg atoms in metrology, such as calibrating black-body shifts in state-of-the-art optical clocks, monitoring the Earth's cryosphere from space, measuring the cosmic microwave background, or searching for dark matter.
We demonstrate the quantum sensing of radiofrequency fields based on cold Rydberg atoms in a super-molasses trap, without the need for magnetic coils. Our approach combines the metrological advantages of cold atoms with a metal-free dielectric sensor head minimizing perturbations to the electromagnetic environment, a feature that was previously restricted to vapor-cell-based devices. Moreover, the absence of inductive loads allows to rapidly alternate between the cooling phase and the Rydberg excitation, leading to trap-loss spectroscopy signals one order of magnitude narrower than for conventional magneto-optical traps. This enables self-calibrated microwave power measurements with an unprecedented dynamic range of 43dB, opening the door to new perspectives of applications in calibration measurements. We also report a scale factor linearity better than 1%, the absence of drifts over several tens of minutes leading to a 3μμμV/cm resolution, and the possibility to retrieve the ellipticity of the applied microwave field. By demonstrating a cold-atom metrological platform in a compact dielectric sensor head, this work paves the way for new applications in the field of radiofrequency measurements with Rydberg atoms, and in other fields of quantum sensing based on cold atoms such as magnetometry, gravimetry or inertial navigation.
While most experimental developments have focused on room-temperature vapors so far, using cold atoms has the advantage of strongly reducing the frequency broadening associated with Doppler effect, while increasing the interaction time between the atoms and the probing beams, offering prospects to make the most of the intrinsic narrow linewidth of Rydberg atoms and perform long-term, stable measurements. Scientists researchers at ONERA have previously used cold atoms to perform absolute measurements of the gravity field onboard moving carriers, showing that this technology is now compatible with practical applications out of the lab. We have recently developed at ONERA a novel approach to sense electromagnetic fields with cold
The detection of microwave (MW) fields with room-temperature Rydberg atomic vapors is a novel technique of optical sensing, introducing a range of merits typically not possible to achieve with conventional antennas [1]. Firstly, the atomic response to MW fields is dependent on a given transition dipole moment between Rydberg energy levels - as this value can be precisely derived from the theory of alkali atoms, e.g. rubidium, Rydberg sensors are intrinsically calibrated and there is no dependency on particular device. Secondly, the detector does not contain any metal parts (apart from trace amount of rubidium), introducing very little distortion to the measured field, so the detection is stealthy, and the detector is practically invulnerable even to strong fields. Typically, however, the best state-of-the-art performance is achieved with an additional local oscillator MW field [2], emitted from the antenna, in which case the scheme is no longer all-optical and some advantages are lost.
Due to their high sensitivity, wide frequency range, SI-traceability and reduced size at low frequency, Rydberg atoms based- sensors of RF/THz fields hold great prospects for many applications including telecommunications, radar, and THz imaging. So far, almost all of these sensors have consisted in probing by means of EIT spectroscopy the Autler-Townes effect resulting from the interaction between the field and a warm vapor of alkaline Rydberg atoms. Despite significant improvement using heterodyning, this approach suffers several limitations caused by broadening mechanisms inherent to warm vapors, and by using EIT as a probe. We report here on a new approach based on trap-loss spectroscopy of the Autler-Townes effect in cold 87Rb atoms confined in a MOT. The doublet of dressed Rydberg states measured this way obeys well the theoretical model of Autler-Townes effect provided lightshifts from neighboring Rydberg states are considered, suggesting the possibility to infer the characteristics of the field from those of the doublet. Study of the resulting sensor revealed a very good linearity, with residual errors of 1%, and a resolution of 5 µV/cm after an integration time of 2600s.
This paper reports on the results of experiments with cold rubidium Rydberg atoms in a magneto-optical trap. The specific feature of the experiments is the excitation of Rydberg atoms in a small volume within a cloud of cold atoms and the sorting of measured signals and spectra according to the number of detected Rydberg atoms. The effective lifetime of the 37 P Rydberg state and its polarizability in a weak electric field are measured. The results obtained are in good agreement with theoretical calculations. It is demonstrated that the localization of the excitation volume in the vicinity of the zero-magnetic-field point makes it possible to improve the spectral resolution and to obtain narrow microwave resonances in Rydberg atoms without switching off the quadrupole magnetic field of the trap. The dependence of the amplitude of dipole-dipole interaction resonances in Rydberg atoms on the number of atoms is measured. This dependence exhibits a linear behavior and agrees with the theory for a weak dipole-dipole interaction.