Rydberg atom-based field sensing enhancement using a split-ring resonator
Christopher L. Holloway, Nikunjkumar Prajapati, Alexandra B. Artusio‐Glimpse, Samuel Berweger, Matthew T. Simons, Yoshiaki Kasahara, Andrea Alù, Richard W. Ziolkowski
We investigate the use of a split-ring resonator (SRR) incorporated with an atomic-vapor cell to improve the sensitivity and the minimal detectable electric (E) field of Rydberg atom-based sensors. In this approach, a sub-wavelength SRR is placed around an atomic vapor-cell filled with cesium atoms for E-field measurements at 1.3 GHz. The SRR provides a factor of 100 in the enhancement of the E-field measurement sensitivity. Using electromagnetically induced transparency (EIT) with Aulter–Townes splitting, E-field measurements down to 5 mV/m are demonstrated with the SRR, while in the absence of the SRR, the minimal detectable field is 500 mV/m. We demonstrate that by combining EIT with a heterodyne Rydberg atom-based mixer approach, the SRR allows for a sensitivity of 5.5 μV/mHz, which is two-orders of magnitude improvement in sensitivity than when the SRR is not used.
We investigate the use of a split-ring resonator (SRR) incorporated with an atomic-vapor cell to improve the sensitivity and the minimal detectable electric (E) field of Rydberg atom-based sensors. In this approach, a sub-wavelength SRR is placed around an atomic vapor-cell filled with cesium atoms for E-field measurements at 1.3 GHz. The SRR provides a factor of 100 in the enhancement of the E-field measurement sensitivity. Using electromagnetically induced transparency (EIT) with Aulter–Townes splitting, E-field measurements down to 5 mV/m are demonstrated with the SRR, while in the absence of the SRR, the minimal detectable field is 500 mV/m. We demonstrate that by combining EIT with a heterodyne Rydberg atom-based mixer approach, the SRR allows for a sensitivity of 5.5 μV/mHz, which is two-orders of magnitude improvement in sensitivity than when the SRR is not used.
Abstract Rydberg atom-based sensors using the atomic heterodyne technique demonstrate prominent performance on sensing sensitivity and thus have significant potential for radar, electronic reconnaissance, and communication applications. Here, we propose a local oscillator (LO) embedded field enhancement resonator to improve the sensitivity and integration of Rydberg atomic heterodyne sensors. In this approach, a vapor cell filled with cesium atoms is placed into the resonance structure for electric (E) field measurements. By integrating parallel-plate waveguide (PPWG) antennas and the resonator, the LO signal can be directly guided to the resonator using coaxial cable instead of the use of external antennas radiating through free space, allowing for a more flexible and practical Rydberg atom-based heterodyne technique. Based on the off-resonant Rydberg atomic heterodyne approach, for a radio frequency (RF) signal at 638 MHz, it is found that the sensitivity is 43 μ V/cm Hz Hz in the absence of the resonator, while in the presence of our resonator, the sensitivity is down to 854.36 nV/cm Hz Hz , indicating 50 times or 34 dB improvement capacity of the proposed resonator. This type of enhancement resonator is expected to benefit Rydberg atomic heterodyne applications in practical environments.
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 experimentally demonstrate enhanced sensitivity of an atom-based Rydberg radio frequency (RF) receiver integrated with a gradient refractive index (GRIN) Luneburg-type metamaterial lens. By analyzing the electromagnetically induced transparency (EIT) effect in Cesium vapor, we compare receiver performance with and without the GRIN lens under a 2.2~GHz and a 3.6~GHz far-field excitation. Our measurements reveal a significant amplification of the EIT window when the lens is introduced, consistent with the theoretical prediction that the local E-field enhancement at the vapor cell reduces the minimum detectable electric field and improves the microwave electric field measurement sensitivity of the Rydberg atom-based RF receiver over an ultrawide bandwidth of the lens. This experimental validation demonstrates the potential of metamaterial-enhanced quantum RF sensing for a wide range of applications, such as electromagnetic compatibility (EMC) testing, quantum radar, and wireless communication.
Rydberg atoms have been used for measuring radio-frequency (RF) electric (E)-fields due to their strong dipole moments over the frequency range of 500 MHz-1 THz. For this, electromagnetically induced transparency (EIT) within the Autler-Townes (AT) regime is used such that the detected E-field is proportional to AT splitting. However, for weak E-fields AT peak separation becomes unresolvable thus limiting the minimum detectable E-field. Here, we demonstrate using the Rydberg atoms as an RF mixer for weak E-field detection well below the AT regime with frequency discrimination better than 1 Hz resolution. A heterodyne detection scenario with two E-fields incident on a vapor cell filled with cesium atoms is used. One E-field at 19.626000 GHz drives the 34D5/2 → 35P3/2 Rydberg transition and acts as a local oscillator (LO) and a second signal E-field (Sig) of interest is at 19.626090 GHz. In the presence of the LO, the Rydberg atoms naturally down convert the Sig field to a 90 kHz intermediate frequency (IF) signal. This IF signal manifests as an oscillation in the probe laser intensity through the Rydberg vapor and is easily detected with a photodiode and lock-in amplifier. In the configuration used here, E-field strength down to ≈ 46 μV/m ± 2 μV/m were detected with a sensitivity of ≈ 79 μVm−1Hz−1/2. Furthermore, neighboring fields 0.1 Hz away and equal in strength to Sig could be discriminated without any leakage into the lock-in signal. For signals 1 Hz away and as high as +60 dB above Sig, leakage into the lock-in signal could be kept below -3 dB.
The Rydberg atomic heterodyne technique and resonant structures represent two prominent approaches that can notably enhance the sensing sensitivity of Rydberg atomic receivers in the atomic and microwave domains, respectively. However, current implementations exhibit low levels of integration, particularly in the VHF band. This article introduces local oscillator (LO) port-integrated resonators (LOIRs) to synergize these methods, aiming to improve sensitivity and system integration in Rydberg atom-based receivers. Through an analysis of the electric field distribution in the split-ring resonator (SRR), we developed two types of LOIRs: the standing wave type LOIR (SIR) and the traveling wave type LOIR (TIR). Experimental investigations were conducted at 264 MHz using a vapor cell containing cesium atoms in the resonators. Spectral measurements indicate that the SIR and TIR provide enhancement factors of 45.8 and 45.3 dB, respectively. When employing the SIR and TIR for Rydberg atomic heterodyning, sensitivity significantly improved to 104.34 and 105.54 (nV/cm)/Hz, respectively. Furthermore, in comparison to the SRR setup in the atomic heterodyne scenario, the LO power consumption decreased to 22.4% and 3.7% with the SIR and TIR, respectively. This research represents a significant advancement toward the practical application of Rydberg atomic receivers.