Rydberg atoms are highly excited atoms that have large sensitivities to external fields, lending these atoms extraordinary characteristics for fundamental high-precision spectroscopy as well as for electromagnetic-field sensing applications. Recent results on high-precision spectroscopy with cold Rydberg atoms in modulated optical lattices are presented. The discussed approach can serve as a platform for fundamental-physics studies, which include a model-insensitive measurement of the Rydberg constant and a search for wave-like dark matter. As an example for the utility of Rydberg atoms in field sensing applications, an experiment is presented in which the linear Stark effect of cold Rydberg atoms is employed to measure electric fields in cold ion clouds, demonstrating that Rydberg laser spectroscopy allows electrode-free, non-invasive plasma diagnostics.
Atoms cooled and trapped using laser light have become the backbone of modern quantum physics research. Various new applications based on laser-cooled atoms are in active development. The work described in this dissertation is dedicated to this endeavor. I present experimental and numerical investigations on several fundamental properties of the laser-cooled atoms in different quantum states and how they may translate into applications within several emerging atom-based technologies. First, I describe the precision measurements of the dynamic polarizability and photo-ionization cross-section at 1064-nm light of the
5D3/2 state in rubidium, which is of interest for the portable atomic clocks. Two different spectroscopic methods are implemented to extract the polarizability from the experimental data. The results are statistically equivalent: -524(17) [-499(59)] atomic units from the first [second] method. The photo-ionization cross section of the
5D3/2 state at 1064~nm is measured to be 44(1) Mb. The aforementioned photo-ionization cross section is suitable for efficient ion generation and the subsequent application in cold-atom-based ion sources. This is demonstrated in the second study presented here. The ion source employs a novel method to monitor the electric microfields of the ions using the Stark effect of the highly-excited (Rydberg) atoms seeded within the origin of the ion source. Rydberg atoms are extremely sensitive to electric fields and serve as an embedded real-time sensor and tracker of the ion-source performance because of their quasicontinuous creation and detection. The principles of such ion-microfield sensing are discussed and analyzed in detail and can be utilized in any cold-atom-based focused-ion-beam source. The hyperfine structure of the
4D3/2 state in rubidium is investigated next. The measurement utilizes two-photon optical absorption spectroscopy and a detailed analysis of light shifts. All four hyperfine components are resolved in the experimental data. The magnetic-dipole and electric-quadrupole hyperfine constants are obtained to be 7.419(45) MHz and 4.19(19) MHz, respectively. Future applications of the
4D3/2 state in optical atomic clocks and Rydberg-atom physics are discussed. Next, I investigate a Rydberg-atom-ion molecule bound by long-range multipolar forces. The molecule is the first example of a bound state between a Rydberg atom and an ion. Strong interactions between these two particles lead to large molecular binding energy (reaching a few GHz) and large binding length (exceeding 1
mum). The Born-Oppenheimer approximation does not hold for the Rydberg-atom-ion molecule because the motion of the Rydberg-atom nucleus is on the same timescale as the dynamics of the ion. The Born-Huang theory is utilized to investigate the resultant nonadiabatic dynamics of the molecule and to make the first fully quantum predictions of its lifetime as a function of the vibrational state and quantum principal number of the Rydberg atom. Lastly, I present a novel technique for atom interferometry that employs uninterrupted three-dimensional confinement and manipulation during the interferometric protocol. The atoms in the existing apparatuses have to follow several-meter-long trajectories along which various detrimental effects such as wave-packet dispersion erase useful phase information. ``Tractor atom interferometry" presented here promises to suppress the harmful effects and improve the interferometers’ sensitivity; provide flexible control over the atomic trajectories; and significantly reduce the experimental footprint. The suitability of this approach for measuring background acceleration (such as due to the gravitational field) is demonstrated. The sensitivity estimations, experimental considerations, and initial laboratory work are discussed.
Rydberg atoms are neutral atoms excited to high principal quantum number states, which endows them with exaggerated properties such as large electric dipole moments, long lifetimes, and extreme sensitivity to external electromagnetic fields. These characteristics form the foundation of Rydberg atom-based sensors, an emerging class of quantum devices capable of optically detecting electric fields across frequencies from DC to the terahertz regime. Rydberg-based electrometry operates through both Autler–Townes (AT) splitting of resonant Rydberg transitions and Stark-shift measurements for high-frequency or far-detuned fields, enabling broadband field sensing from DC to the THz regime. Using ladder-type electromagnetically induced transparency (EIT) and AT splitting, these sensors enable non-invasive, SI-traceable measurements of field amplitude, frequency, phase, and polarization. Recent developments have demonstrated broadband electric field probes, voltage calibration standards, and compact RF receivers based on thermal vapor cells and integrated photonic architectures. Furthermore, innovations in multi-photon EIT, superheterodyne readout, and multi wave mixing have expanded the dynamic range and bandwidth of Rydberg-based electrometry. Despite challenges related to environmental perturbations, linewidth broadening, and laser stabilization, ongoing advances in atomic control, hybrid photonic integration, and EIT-based readout promise scalable, chip-compatible sensors. This review summarizes the physical principles, experimental progress, and emerging applications of Rydberg atom-based sensing, emphasizing their potential for next generation quantum metrology, wireless communication, and precision field mapping.
Measurements of plasma electric fields are essential to the advancement of plasma science and applications. Performing non-invasive in situ measurements of plasma fields on sub-millimeter length scales with high sensitivity over a large range of field magnitude remains an outstanding challenge. We introduce and demonstrate a method for plasma electric field measurement that employs electromagnetically induced transparency as a high-resolution quantum-optical probe for the Stark energy level shifts of Rydberg atoms embedded in a plasma and serving as highly sensitive field sensors. The method is applied in diagnostics of plasmas generated by photo-excitation of a cesium vapor. The plasma electric fields are extracted from spatially resolved measurements of field-induced lineshape changes and shifts of Rydberg resonances in rubidium tracer atoms. Measurement capabilities over a range of plasma densities and temperatures are exploited to characterize plasmas in applied magnetic fields and to image electric-field distributions in cyclotron-heated plasmas. Our results pave the way toward further applications of Rydberg-atom-based field sensors to diagnostics and monitoring of electric fields due to plasmas.
Measurements of plasma electric fields are essential to the advancement of plasma science and applications. Methods for non-invasive in situ measurements of plasma fields on sub-millimeter length scales with high sensitivity over a large field range remain an outstanding challenge. Here, we introduce and demonstrate a new method for plasma electric field measurement that employs electromagnetically induced transparency as a high-resolution quantum-optical probe for the Stark energy level shifts of plasma-embedded Rydberg atoms, which serve as highly-sensitive field sensors with a large dynamic range. The method is applied in diagnostics of plasmas photo-excited out of a cesium vapor. The plasma electric fields are extracted from spatially-resolved measurements of field-induced shape changes and shifts of Rydberg resonances in rubidium tracer atoms. Measurement capabilities over a range of plasma densities and temperatures are exploited to characterize plasmas in applied magnetic fields and to image electric-field distributions in cyclotron-heated plasmas.
Rydberg atoms have emerged as a versatile and efficient platform for high-sensitivity quantum sensing of free-space electric fields, with remarkable progress in detecting low-frequency signals. To date, low-frequency Rydberg receivers have relied on a constant bias field, typically realized via intra-cell electrodes or Rydberg plasmas generated by photoelectric effects or inter-atomic interactions. While these approaches improve sensitivity, they suffer from inherent challenges in calibration, long-term stability, and robustness, hindering practical deployment. Here, we propose, design, and experimentally demonstrate a quantum sensing scheme for low-frequency electric signals using modulated auxiliary fields in Rydberg atoms. Unlike conventional methods that employ external DC electric fields that are often fully shielded by adsorbed atom layers on the cell walls, we introduce an AC-field modulation strategy. The incoming low-frequency signal mixes with the auxiliary field, and together they induce Stark shifts of the Rydberg level. These shifts are mapped onto the probe laser via electromagnetically induced transparency (EIT), in a manner analogous to heterodyne detection. We demonstrate a sensitivity of
7.5±2.6 μV/(cm⋅Hz1/2) at 5 kHz and a minimal detectable field of
0.26±0.04 μV/cm with an integration time of 1000 s. Furthermore, we extend this approach to systematically analyze the performance of generalized auxiliary fields containing multiple frequency components. By virtue of modulated auxiliary field and quantum frequency mixing, our results establish a robust and systematic framework for quantum sensing of low-frequency electric fields with Rydberg atoms, offering improved sensitivity, stability, and immunity to environmental drifts.