This work encompasses two projects employing coherent probing of neutral rubidium atom vapors for sensing applications: 1) observing and characterizing new ``twists'' within Nonlinear Magneto-Optical Rotation (NMOR) signals in laser-cooled atoms. Using these features an in-situ, multi-directional characterization of magnetic fields and gradients at the sub-mG (and mG/mm) level in a compact cold-atom system is demonstrated; 2) high-bandwidth, phase-sensitive electrometry via Electromagnetically Induced Transparency (EIT) with a warm vapor of Rydberg atoms is employed as a digital communication receiver of free-space, modulated RF carrier electric fields. Channel capacities in excess of 10 Mbit/s are measured. Performance limitations due to EIT probing and fundamental quantum noise are explored in detail.
This work encompasses two projects employing coherent probing of neutral rubidium atom vapors for sensing applications: 1) observing and characterizing new ``twists'' within Nonlinear Magneto-Optical Rotation (NMOR) signals in laser-cooled atoms. Using these features an in-situ, multi-directional characterization of magnetic fields and gradients at the sub-mG (and mG/mm) level in a compact cold-atom system is demonstrated; 2) high-bandwidth, phase-sensitive electrometry via Electromagnetically Induced Transparency (EIT) with a warm vapor of Rydberg atoms is employed as a digital communication receiver of free-space, modulated RF carrier electric fields. Channel capacities in excess of 10 Mbit/s are measured. Performance limitations due to EIT probing and fundamental quantum noise are explored in detail.
Atoms form the basis of precise measurement for many quantities (time, acceleration, rotation, magnetic field, etc.). Measurements of microwave frequency electric fields by traditional methods (i.e. engineered antennas) have limited sensitivity and can be difficult to calibrate properly. Highly-excited (Rydberg) neutral atoms have very large electric-dipole moments and many dipole allowed transitions in the range of 1 - 500 GHz. It is possible to sensitively probe the electric field in this range using the combination of two quantum interference phenomena: electromagnetically induced transparency and the Autler-Townes effect. This technique allows for very sensitive field amplitude, polarization, and sub-wavelength imaging measurements. These quantities can be extracted by measuring properties of a probe laser beam as it passes through a warm rubidium vapor cell. Thus far, Rydberg microwave electrometry has relied upon the absorption of the probe laser. We report on our use of polarization rotation, which corresponds to the real part of the susceptibility, for measuring the properties of microwave frequency electric fields. Our simulations show that when a magnetic field is present and directed along the optical propagation direction a polarization rotation signal exists and can be used for microwave electrometry. One central advantage in using the polarization rotation signal rather than the absorption signal is that common mode laser noise is naturally eliminated leading to a potentially dramatic increase in signal-to-noise ratio.
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.
Quantum sensing exploits the sensitivity of quantum systems to their environment, translating external fields and forces into measurable shifts in quantum-mechanical observables. Neutral atoms constitute a highly effective and scalable sensing platform owing to their identical nature and extended coherence times. This dissertation investigates two implementations of atom-based quantum sensing: electric field diagnostics in low-pressure plasma discharges using Rydberg electromagnetically induced transparency (EIT), and inertial sensing via tractor atom interferometry (TAI). Non-invasive electric field measurement is crucial for understanding plasma dynamics without disturbing the local environment, for which high-resolution, coherent spectroscopy of Rydberg states via EIT is a promising candidate. Deploying EIT in plasma environments requires a systematic characterization of collisional effects. To this end, Rydberg-EIT is analyzed in rubidium vapor interacting with plasma precursor gases such as argon, neon, and nitrogen at pressures up to 5 Torr. The observed frequency shifts and collisional broadening are consistent with semiclassical predictions from the Fermi pseudopotential model. Crucially, collisional broadening remains narrower than typical EIT linewidths below 100 mTorr, identifying this pressure range as an operational window for EIT-based plasma field diagnostics. Rydberg-EIT is subsequently applied to a low-pressure, inductively coupled plasma (ICP). In a custom ultra-high-vacuum plasma chamber, Rydberg Stark shifts of rubidium tracers seeded into a continuous argon discharge are mapped via EIT. Prior to plasma ignition, Rydberg spectra exhibit modulation sidebands driven by both electric and magnetic near-fields of the ICP coil. Upon ignition, the bulk plasma screens the rf drive field, suppressing the sidebands. The resulting in-plasma lineshapes are instead governed by V/cm-scale plasma microfields and collisional broadening. Modeling the microfield with a Holtsmark distribution enables the extraction of plasma electron densities as a function of pressure and rf power. By resolving a Rydberg resonance whose lineshape is governed by the plasma environment rather than by spectroscopic limits, these measurements establish a framework for sensitive and non-invasive plasma field diagnostics. The second part of the dissertation investigates inertial sensing via a tractor atom interferometer (TAI). Unlike free-space propagation, TAI utilizes continuous three-dimensional confinement and coherent atomic transport. This mitigates wave packet dispersion, guarantees path closure, permits variable holding times, and enables complex spatial trajectories. The proposed experimental framework employs a Laguerre-Gaussian ``pinwheel" optical lattice to drive multi-loop interferometric sequences. Numerical simulations confirm that TAI implementations may achieve rotation sensitivities comparable to those of established free-space interferometers. In the fast-transport regime required for large enclosed areas, where nonadiabatic excitations would otherwise degrade contrast, quantum optimal control is used to design acceleration sequences that remain fast while preserving coherence. These results illustrate the versatility of neutral atoms as a sensing platform, probing electromagnetic fields through their internal structure and inertial forces through their center-of-mass motion.
The aim of this book is to present new results in rapidly developing fields of nonlinear optics such as atomic coherence, magneto-optics of atomic media, Doppler-free spectroscopy, time-domain spectroscopy of dense atomic vapors, frequency comb spectroscopy and atom-surface interactions. The discovery of such coherent effects as coherent population trapping (CPT), electromagnetically induced transparency (EIT) and electromagnetically induced absorption (EIA) opened a new avenue for development in many fields of nonlinear optics. Investigations during the last decade have shown many related new results and approaches in nonlinear optics. These include nonlinear magneto-optical processes (NMOP) in the context of high precision magnetometry, quantum information storage and processing, magnetic resonance imaging and magnetic particle detection; the use of ultra-thin (nanometric length) atomic vapor cells in magneto-optical experiments, which show new peculiarities of both coherent effects and NMOP; the use of frequency and amplitude modulated laser beams for NMOP studies in atomic vapors with the aim of extending the range of ultra-precise magnetometers to stronger, particularly geomagnetic fields; application of the counter-propagating beam technique to reveal the Doppler free nonlinear Faraday rotation signals, as a spectroscopic tool and for applications; enhanced nonlinearity due to atomic coherence in multi-state systems; experimental study of EIT in solids; the use of the phase stabilized frequency domain combs of femtosecond laser pulses for velocity selective optical pumping of atomic hyperfine levels, as a direct frequency comb spectroscopy; time-domain nonlinear spectroscopy of dense atomic vapors; atom-surface interactions and laser induced adsorption and desorption of alkali atoms on the surface of solid materials for nanotechnology applications
Research of hot atomic vapor systems has a long history. Recently, much-improved technologies, such as lasers, microwaves and digital/analog control systems, have led to exciting progress in this reviving field. Due to its cryogenic-free and vacuum-free deployment potential, room-temperature and quantum-enabled sensing devices using gaseous atoms have become a popular research topic, and engineering such devices has received considerable attention. Proof-of-principle experiments have been performed demonstrating new ideas such as quantum-enhanced motion sensors, next-generation magnetometers, Rydberg enabled microwave sensors, etc. This thesis focuses on my work related to electromagnetic-field sensing using Rydberg atoms in vapor cells, where Rydberg atoms are excited and detected by electromagnetically induced transparency (EIT) spectroscopy. I first investigate the detection of strong magnetic fields (sim 1~T) in the Paschen-Back regime. The diamagnetic (quadratic) response of the Rydberg levels makes the atoms sensitive to small fluctuations in field strength on a large background. By implementing an isotope-mixed cell, we demonstrate that accurate measurement, within a relative uncertainty of pm0.12%. Many Rydberg-enabled radio frequency and microwave sensing applications require a capability of zeroing or intentional tuning of small DC electric fields inside the vapor cell. For this purpose, I explore an in-situ DC electric-field sensing and tuning method without using any bulk or thin film electrodes. I find that the photoelectric effect on the vapor cell walls (with invisible, atomic Rb aggregate layers covering the surfaces) can generate tuning fields up to 0.8~V/cm, with an inhomogeneity of about 2%. The spatial distribution of these fields can be directly monitored by quadratic Stark shifts of the Rydberg atoms. This work may inspire new approaches for DC-field control in miniaturized, metal-free atomic vapor-cell devices. Like many other quantum measurements on hot gaseous samples, short interaction time and other technical decoherence processes are the major factors which limit the precision and, in certain cases, the accuracy of the metrological results. In order to study these effects in the context of EIT, I performed an EIT experiment using a Lambda-type quantum system consisting of the hyperfine ground states and the first excited electronic state of the Rb atoms contained in a buffer-gas-free thermal vapor cell without anti-relaxation coating. Technical line-broadening effects due to inhomogeneity of stray magnetic fields, laser frequency jitter, transverse beam intensity distribution, interaction time distribution, and atom-wall/impurity gas collisions are studied. Experimental results and numerical simulations are compared. These results provide crucial information and quantitative insights for vapor cell sensor design. The development of compact and multi-functional spectroscopy vapor cells is widely considered to be a critical engineering step towards manufacturing field-deployable sensors for real life applications. My R&D efforts towards fabrication of glass spectroscopy cells with integrated, highly-conductive silicon components are presented in the last part of my thesis. I explored various technical challenges and successfully developed a proof-of-principle prototype from scratch. The device allows the application of electric fields inside the cell for particle trapping and for tuning Rydberg transitions. Further, the highly-conductive silicon components enable microwave polarization filtering for microwave sensing applications, plasma-physics studies, etc. Preliminary experimental/technical data and simulations are presented. In summary, in my thesis I report on a comprehensive study of several spectroscopic and field sensing applications of Rydberg and ground-state atoms in vapor cells, as well as forays into novel methods to engineer vapor cells with embedded electrodes.