We present recent improvements within the growing field of Rydberg atom sensors. While initially started as a path towards absolute, independent measurements of electric fields, the research landscape has evolved into the realm of quantum sensors and receivers. We discuss the capabilities and limitations of Rydberg atom receivers, and we show how different atomic properties enhance or limit sensitivity and bandwidth.This data is for a review paper. Figures 6 (a) and 8 (a) and (b) are new data. The rest of the data is extracted from other NIST publications that have a data management plan. Related data are from the following papers.https://doi.org/10.1063/5.0069195https://doi.org/10.48550/arXiv.2402.00718https://doi.org/10.1116/5.0098057

Rydberg atom-based receivers of modulated radio frequency (RF) fields are promising systems for measurements. These systems are self-calibrating, widely tunable, nearly transparent to RF fields, and can be electrically small. However, the instantaneous bandwidth of current Rydberg atom receivers is typically less than 1 MHz. Using two-photon electromagnetically induced transparency (EIT) to observe the 56D5/2 Rydberg state in cesium, we measure modulation sidebands on each tooth in a probe optical frequency comb that spans the D2 F=4-F'=5 transition resulting from transmission modulation of the probe beam. This transmission modulation occurs from changes in susceptibility of the room temperature cesium vapor as two RF fields impinge on the atoms. A strong RF local oscillator is resonant with the 56D-57P state and mixes with a weak RF signal field detuned from the RF LO by an intermediate frequency. Using a self-heterodyned electro-optic comb setup, we separate positive and negative sideband amplitudes and compare to an equivalent comb-free system. These data report EIT measurement with the comb system, local spectra around two comb teeth - one within and one outside the EIT line, and normalized minimum detectable RF signal field as a function of RF intermediate frequency used to evaluate the instantaneous bandwidth of the single frequency, positive sideband, and negative sideband datasets.

Although Rydberg atom-based electric field sensing provides key advantages over traditional antenna-based detection, it remains limited by the need for a local oscillator (LO) for low-field and phase resolved detection. In this work, we demonstrate the general applicability of closed-loop quantum interferometric schemes for Rydberg field sensing, which eliminate the need for an LO. We reveal that the quantum-interferometrically defined phase and frequency of our scheme provides an internal reference that enables LO-free full 360 degree-resolved phase sensitivity. This internal reference can further be used analogously to a traditional LO for atom-based down-mixing to an intermediate frequency for lock-in-based phase detection, which we demonstrate by demodulating a four phase-state signal broadcast on the atoms.

On-resonance Rydberg atom-based radio-frequency (RF) electric field sensing methods remain limited by the narrow frequency signal detection bands available by resonant transitions. The use ofan additional RF tuner field to dress or shift a target Rydberg state can be used to return a detuned signal field to resonance and thus dramatically extend the frequency range available for resonantsensing. Here we compare three distinct tuning schemes based on adjacent Rydberg transitions, which are shown to have distinct tuning characteristics and can be tuned with mechanisms based onthe tuning field frequency or field strength. We further show that a two-photon Raman feature can be used as an effective tuning mechanism separate from conventional Autler-Townes splitting. Wecompare our tuning schemes to AC Stark effect-based broadband RF field sensing and show that although the sensitivity is diminished as we tune away from a resonant state, it nevertheless can beused in configurations where there is a low density of Rydberg states, which would result in a weak AC Stark effect.

Improving the bandwidth of Rydberg atom-based receivers is an ongoing challenge owing to the long-lived Rydberg state lifetimes that limit the refresh rate of ground state atoms.In particular, the LO-based Rydberg mixer approach allows for bandwidths into the few-MHz range.Here we use heterodyne detection of the Rydberg atom receiver probe laser to separate the negative and positive sidebands that originate from distinct six wave mixing processes in order to investigate their individual bandwidths.We experimentally confirm the prediction that the negative sideband exhibits a higher bandwidth than the positive sideband.We further explore the effect of coupling and probe laser Rabi frequency on the bandwidth, which we find to be in good agreement with our model. We achieved a maximum experimental (and theoretical) bandwidth of about 11 (11)~MHz and 3.5 (5)~MHz for the negative and positive sidebands, respectively, from the -3dB roll-off point for optimized field parameters.This work provides insight into the bandwidth-limiting features of Rydberg atom receivers and points the way towards further optimization of their response.

This dataset represents the results of calculations of atomic absorption spectra for the case of two-color EIT. We compare computation methods, specifically Gaussian sampling, to find that one sampling method converges to smooth transmittance curves in less time than the other. We also include some example scripts which generate and plot the figure data.

Deep subwavelength RF imaging with atomic Rydberg sensors has overcome fundamental limitations of traditionalantennas and enabled ultra-wideband detection of omni-directional time varying fields all in a compactform factor. However, in most applications, Rydberg sensors require the use of a secondary strong RF referencefield to serve as a phase reference. Here, we demonstrate a new type of Rydberg sensor for Angle-of-Arrival(AoA) sensing which utilizes subwavelength imaging of standing wave fields. By placing a metallic plate withinthe Rydberg cell, we can determine the AoA independent of the strength of incoming RF field and without requiringa secondary strong RF phase reference field. We perform precision AoA measurements with a roboticantenna positioning system for 4.2, 5.0, and 5.7 GHz signals and demonstrate a 1.7◦ polar angular resolutionfrom 0◦ to 60◦ AoA and 4.1◦ over all possible angles.

Deep subwavelength RF imaging with atomic Rydberg sensors has overcome fundamental limitations of traditionalantennas and enabled ultra-wideband detection of omni-directional time varying fields all in a compactform factor. However, in most applications, Rydberg sensors require the use of a secondary strong RF referencefield to serve as a phase reference. Here, we demonstrate a new type of Rydberg sensor for Angle-of-Arrival(AoA) sensing which utilizes subwavelength imaging of standing wave fields. By placing a metallic plate withinthe Rydberg cell, we can determine the AoA independent of the strength of incoming RF field and without requiringa secondary strong RF phase reference field. We perform precision AoA measurements with a roboticantenna positioning system for 4.2, 5.0, and 5.7 GHz signals and demonstrate a 1.7◦ polar angular resolutionfrom 0◦ to 60◦ AoA and 4.1◦ over all possible angles.

Simulated transmission curves illustrating an efficient new calculation method. Data was produced for a publication, and is indexed by figure.

These data files contain the data for the measured transition frequencies shown in Table I and the traces in Figure 3 of the publication "Frequency-comb spectroscopy on pure quantum states of a single molecular ion," accessible at https://arxiv.org/abs/1911.12808. In this publication we use generally applicable quantum-logic techniques to prepare a trapped molecular ion in a single quantum state, drive terahertz rotational transitions with an optical frequency comb, and read out the molecular state non-destructively, leaving the molecule ready for further manipulation. One file contains data For Table 1. In the measurement of rotational transition frequencies, the intensities of the comb beams are varied to characterize the effect of AC Stark shift, while the intensity ratio between the sigma and pi polarized beams are kept at close to 2. The average intensity of the sigma-polarized comb beam is quantified by measuring the resultant Stark shift, fSS_sigma, on the 729 nm transition of the Ca+ ion, with the Ca+ ion where the CaH+ ion would be during rotational spectroscopy experiments. The other file contains data for Figure 3, (a) Spectra for the J = 4 to 2 transition: 40CaH+ is prepared in J = 2, followed by a pulse train from the comb Raman beams probing the J = 2 to J = 4 transition. After the probe pulse train, projective measurements of both initial and final states are performed and the state occupation probability is determined. The probe time is ~1.6 ms. The frequency shows the offset of the Raman difference frequency from the resonant value. (b) Rabi flopping on the J = 4 to J = 2 transition: Starting in J = 4, with the comb Raman pulse detuning set to resonance, the state of the 40CaH+ ion is driven coherently to J = 2 by a pulse train of variable duration from the comb Raman beams. The center wavelength of the frequency comb was ~800 nm for these spectra and Rabi flopping traces. The error bars stand for ±1 standard deviation.