Improving the spectral resolution and measurement range of quantum microwave electrometry by cold Rydberg atoms

Abstract

We theoretically and experimentally studied quantum microwave electrometry in a cold atomic system using Rydberg electromagnetic induction transparency (EIT) and Autler--Townes splitting ( EIT-AT splitting). In cold atoms, a spectral linewidth of ~ 500 kHz for EIT was achieved owing to a significant reduction in residual Doppler width, i.e., by at least an order of magnitude, compared to that in vapor cells at room temperature. Therefore, the minimum microwave electric field intensity EMW that can be measured is 430 μV/cm, which is one order higher sensitivity in the EIT-AT regime than that in vapor cells at room temperature. Unlike microwave electrometry in atomic vapor cells, EIT-AT splitting cannot be observed if EMW is so large that the EIT-AT splitting interval Δ fm exceeds the absorption peak width of the cold atom while scanning the frequency of the probe laser (ωp). Moreover, EIT-AT splitting can be observed if Δ fm exceeds the natural linewidth Γeg of the intermediate states while scanning the coupling laser (ωc) and maintains a high spectral resolution with a high signal-to-noise ratio. While scanning ωc, the upper microwave electric field intensity is limited by the scanning range of our setup. Using our system, we measure the maximum field to be 21.6 mV/cm, nearly three times higher than that of 6.8 mV/cm while scanning ωp. The results indicate that the linear range of EMW measured using EIT-AT splitting considerably improves in cold Rydberg atoms.

Magnetic exchange interactions and non-Debye relaxation in spin-3/2 frustrated Kagomé magnet Co3V2O8

“…The parameters extracted from the fitting are plotted in figure 12(b). The DC conductivity obtained from the fitting was further analyzed using the Arrhenius equation: σ dc = σ 0 exp ( −Ea kBT ), where σ 0 is the pre-exponential factor, E a is the DC activation energy [44,45]. From the figure, we can clearly distinguish the presence of two different slopes in two different temperature regions, suggesting the presence of multiple conduction processes in the investigated system with different activation energies.…”

“…The complex dielectric modulus spectroscopy is adopted to investigate the precise capacitive dielectric relaxation process along with the contributions of space charge injection, electrode polarization, and separation of the local behavior of electrode effect. Various polycrystals have been analyzed by means of modulus spectroscopy, which is quite convenient in understanding the multiple relaxation processes [34,45,47]. The frequency dependence of real and imaginary components of the modulus spectra from 36 • C to 270 • C is shown in figures 13(a) and (b), respectively.…”

“…In different frequency regions, i.e. for f < f max and f > f max , the charge transport occurs through long-range translational mobility and short-range mobility of charge carriers, respectively [34,45,51,52]. As can be seen from figure 13(b), the peak corresponding to M ′ ′ max in M ′′ ( f, T) shifts to higher frequencies with the increasing temperature, which further suggests that the relaxation time (τ ) decreases with temperature [53].…”

Microwave electrometry with Rydberg atoms in a vapor cell using microwave amplitude modulation

“…Several methods have been developed to push the lower limit of EIT-AT splitting measurement for MW electric fields. These include the cold atom method, [27,28] MW frequency detuning, [29] auxiliary MW field, [30,31] three-photon excitation [32] and amplitude modulation (AM) dispersion. [33] Laser-cooled cold atoms, with their lower temperatures and reduced dephasing rates, significantly narrow the Rydberg EIT linewidth, enhancing precision.…”

“…Kai-Yu Liao et al achieved a minimum MW field resolution of 100 µV/cm using cold Rydberg atom samples, [27] while Fei Zhou et al reached a 222 µV/cm limit. [28,34] However, the laser cooling of atoms requires complex equipment and has a long preparation cycle. These characteristics make the experimental platform based on cold atoms unfavorable to the subsequent development and maintenance.…”