We present a hybrid atomic sensor that realizes radio-frequency electric field detection with intrinsic field enhancement and polarization selectivity for robust high-sensitivity field measurement. The sensor incorporates a passive resonator element integrated with an atomic vapor cell that provides enhancement and polarization selectivity of incident radio-frequency fields. The enhanced intra-cavity radio-frequency field is measured by atoms using a quantum-optical readout of AC level shifts of field-sensitive atomic Rydberg states. In our demonstration, we employ a split field-enhancement resonator embedded in a rubidium vapor cell to enhance and detect C-band radio-frequency fields. We observe a field enhancement equivalent to a 24 dB gain in intensity sensitivity. The spatial profile of the resonant field mode inside the field-enhancement cavity is characterized and robust polarization measurement of the incident field is demonstrated. The measured performance metrics of the sensor are in good agreement with simulations. Applications of such atomic sensors in ultra-weak radio-frequency detection and advanced measurement capabilities are discussed.
We present a hybrid atomic sensor that realizes radio-frequency electric field detection with intrinsic field enhancement and polarization selectivity for robust high-sensitivity field measurement. The sensor incorporates a passive resonator element integrated with an atomic vapor cell that provides enhancement and polarization selectivity of incident radio-frequency fields. The enhanced intra-cavity radio-frequency field is measured by atoms using a quantum-optical readout of AC level shifts of field-sensitive atomic Rydberg states. In our demonstration, we employ a split field-enhancement resonator embedded in a rubidium vapor cell to enhance and detect C-band radio-frequency fields. We observe a field enhancement equivalent to a 24 dB gain in intensity sensitivity. The spatial profile of the resonant field mode inside the field-enhancement cavity is characterized and robust polarization measurement of the incident field is demonstrated. The measured performance metrics of the sensor are in good agreement with simulations. Applications of such atomic sensors in ultra-weak radio-frequency detection and advanced measurement capabilities are discussed.
We present a Rydberg-Atom electric field sensor optimized to detect signals at sub-100 MHz carrier frequencies. The sensing setup employs a sapphire vapor cell that allows for detection of signals below 100 MHz-typical vapor cells made of glass or quartz demonstrate strong screening of radio frequency (RF) signals in this frequency regime. Applied signals are detected by observing AC Stark shifts in the atomic vapor energy levels. As a test case for the commercial utility of this receiver, we perform our tests at several carrier frequencies in the Industrial, Scientific, and Medical (ISM) band. At each carrier frequency, we report sensitivity, minimum detectable field, and detectable electric-field dynamic range. We also present a routine for optimizing off-resonant signal detection by tuning experimental parameters such as Rydberg coupler laser detuning and RF local oscillator strength. This Python-based optimization routine, which can be used at any off-resonant carrier frequency, is shared on GitHub for others to use in their own investigations.
Abstract The Rydberg atom can be used as an active probe for precision radio-frequency (RF) electric field (E-field) measurement; however, the RF cavity resonance and scattering effect of an atomic vapor cell lead to polarization distortion inside the cell, and the depolarization effect limits the sensitivity and accuracy of E-field measurement. The finite element simulation and characteristic mode analysis of a hollow-cavity model are implemented to find an optimized solution of minimizing such depolarization. Manipulating atoms in the middle layer of a vapor cell along an incident field vector can avoid the depolarization, which is validated by the vector distribution measurement at 15.09 GHz.
Highly excited Rydberg atoms in a room-temperature vapor cell are promising for developing a radio-frequency (RF) electric field (E-field) sensor and relevant measurement standards with high accuracy and sensitivity. The all-optical sensing approach is based on electromagnetically-induced transparency and Autler-Townes splitting induced by the RF E-field. Systematic investigation of measurement uncertainty is of great importance for developing a national measurement standard. The presence of a dielectric vapor cell containing alkali atoms changes the magnitude, polarization, and spatial distribution of the incident RF field. In this paper, the field distortion of rubidium vapor cells is investigated, in terms of both field strength distortion and depolarization. Full-wave numerical simulation and analysis are employed to determine general optimization solutions for minimizing such distortion and validated by measuring the E-field vector distribution inside different vapor cells. This work can improve the accuracy of atom-based RF E-field measurements and contributes to the development of related RF quantum sensors.
In this article, we propose a new paradigm of room-temperature Rydberg atomic receiver for high frequency (HF) band sensing with high sensitivity. The proposed Rydberg atomic HF band receiver is implemented via a multilayered split-ring resonator (MSRR) and an atomic vapor cell. The MSRR is constructed by a five-layered printed circuit board within a deep-subwavelength size, providing a strongly enhanced electric field of the incident radio-frequency (RF) field. Using a quantum-optical readout of AC level shifts of field-sensitive atomic Rydberg states, the enhanced intra-cavity RF field significantly improves the sensitivity of the atomic receiver. In the measurement, we characterize the AC-stark shift in the frequency and power spectrum of the incident RF field. Furthermore, the sensitivity of the whole system is presented by utilizing the off-resonant Rydberg atomic heterodyne technique. In the absence of the MSRR, the sensitivity for an RF signal at 20.51 MHz was found to be 27.46 μV/cm √Hz. However, with the presence of our MSRR, the sensitivity significantly improved to 29.09 nV/cm √Hz, indicating a remarkable enhancement capacity of 944 times or 60 dB. This research holds great potential for high-sensitivity Rydberg atomic sensing, particularly in the HF band.
Significant progress has been made in atom-based measurements of length, time, gravity and electromagnetic fields in recently years. Rydberg atom-based microwave electric field measurement, using electromagnetically induced transparency (EIT) in room temperature alkali-metal vapors, has been extensively investigated and aroused the broad interest. This approach may establish a new standard for the measurements of microwave (MW) and radio frequency (RF) electric fields.In this review, we describe the work on a new method of measuring electric fields based on quantum interference by using either cesium or rubidium atoms contained in a dielectric vapor cell. Rydberg atoms with principal quantum number n >>1 have large direct current (DC) polarizabilities and microwave transition dipole moments, thereby making them extremely sensitive to external electric fields. Using the Rydberg three-level EIT to detect the level splitting and shift that is induced by the external field, we can realize a rapid and robust self-calibration method of measuring the electric field in a frequency range from 0.01 GHz to 1000 GHz. For the MW electric field (frequency range > 1 GHz), the MW field causes the Rydberg states to split, known as an Autler-Townes splitting (A-T) effect when the applied microwave can resonate with adjacent Rydberg states. The MW coupled A-T splitting is proportional to the applied electric field strength, from which the field strength is measured. Using the EIT window, a high sensitivity of 3 μV·cm-1·Hz-1/2 and small electric field of 1 μV/cm are expected to be achieved with a modest setup, and the limitations of the sensitivity are also addressed in the review. For the RF field at frequency mj EIT lines, and avoided crossings formed with the fine-structure levels of equal mj and different J's, which is used to calibrate and measure the RF field amplitude. On the other hand, the dependence of the EIT-line strength on the RF field polarization provides a fast and robust polarization measurement of RF fields based on matching experimental data with a theoretical simulation. The measurements of minimum strengths and sensitivity of RF fields based on Rydberg atoms are one order magnitude below the values obtained by traditional antenna methods. The atom-based field measurement paves the way for determining fields through calibration-free, invariable atomic properties and miniaturization. We also propose its various potential applications in the future.
We investigate and employ optical Rydberg resonances in an atomic vapor cell for measurements of high-intensity VHF-band radio frequency (rf) electric fields. An atomic vapor cell with integrated electrodes is used to generate high-intensity 50--500 MHz rf electric fields reaching $\ensuremath{\sim}5$ kV/m in a submillimeter gap. The fields are measured using Rydberg electromagnetically induced transparency as an optical readout of field-sensitive 30DJ and 35DJ Rydberg states of atoms within the gap. The rf electric field is determined by matching observed spectroscopic markers, including ac level shifts, even-harmonic rf sidebands, and rf-induced avoided crossings in the Rydberg manifold to calculated spectra derived from a nonperturbative Floquet theory. In our measurements, rf field frequencies and electric-field amplitudes are determined to an accuracy of 1.0 and 1.5, respectively. In the atom-field interaction, we observe a transition from a quantum regime, characterized by discrete even-harmonic Floquet states separated by an even multiple of the rf field frequency, into a semiclassical regime at very strong fields, in which the spectrum exhibits unresolved resonances whose strengths are smoothly modulated at a frequency of approximately five times the rf frequency. The underlying physics is explored.