To address the long-standing bottlenecks of traditional short-wave sensing technologies, including the insurmountable sensitivity limit caused by Johnson-Nyquist thermal noise and the excessively bulky antenna size restricted by the Chu limit, as well as to further enhance the measurement sensitivity of existing Rydberg atom sensing systems, this study focuses on developing a miniaturized multi-layer square spiral resonator for short-wave atomic sensing enhancement. The proposed resonator is designed based on the traditional metamaterial split-ring resonator (SRR) structure and integrates the miniaturization principle of ceramic laminated wound inductors. It is composed of stacked multi-layer square spirals connected to parallel metal plates via epitaxial metal arms, which not only achieves device miniaturization but also enables responsive capability to multi-polarized waves, with the optimal enhancement effect on right-hand circularly polarized (RCP) waves. Systematic multi-parameter coupling simulations are conducted to clarify the influences of key structural parameters-such as square spiral side length, cross-sectional area, number of spiral layers, resonator height, and connecting arm distance-on the resonant frequency and electric field enhancement performance, thus forming a complete optimization design method. For experimental validation, a physical prototype of the resonator is fabricated using brass, with nylon dielectric pillars added for structural stability and tuning screws integrated to compensate for frequency deviations caused by manufacturing errors. Experimental validation uses two-photon transition to prepare the 72D5/2 Rydberg state of 133Cs atoms, combined with electromagnetically induced transparency spectroscopy and heterodyne measurements. Results demonstrate that at 15.54 MHz, the resonator achieves an electric field enhancement factor of 3981 (corresponding to 72 dB), boosting the system's sensitivity from 10.39 mu V & centerdot;cm(-1)& centerdot;Hz(-1/2 )to 2.60 nV & centerdot;cm(-1)& centerdot;Hz(-1/2). Outdoor tests successfully receive the 13.85 MHz signal from China Radio International via the heterodyne method, with the demodulated signal producing clear audio output without preprocessing. This miniaturized resonator enhances atom-electric field coupling, breaking through the limitations of traditional short-wave sensing and providing technical support for short-wave communication and direction-finding applications. Future work will optimize the structure to balance sensitivity and bandwidth.

Rydberg atomic receiver holds distinctive advantages of ultra-wide operating bandwidth and inherently high sensitivity in electric field measurement1, in particular, it promises unique superiority of miniaturization for low-frequency especially kHz-band signals, which hold pivotal value in applications such as long-range navigation, ground-penetrating radar, and underwater communication. However, the capability of kHz atomic receivers remains severely constrained by the shielding effects of adsorbed alkali metal atoms. Here, we propose a conceptually new self-dressing kHz signal measurement paradigm by converting the undesired coupling-laser-induced DC field to an atomic dressing, and deftly building atomic superheterodyne inside the sapphire vapor cell, which is prepared to adequately suppress the low-frequency shielding through resistivity manipulation engineering. Further, we realize strengthened interaction between the atoms and kHz field by localized enhancement of the incident signals, and finally achieve an ultrahigh sensitivity of 13.5 nV/cm/Hz1/2 at 100 kHz. This architecture represents a significant advance, with the potential to greatly accelerate the practical applications of Rydberg atomic receivers in kHz-band detection, communication, and related fields.

Rydberg atom antennas have the remarkable advantages of nondestructive and high sensitivity for RF telecommunications. However, current implementations are carried out on the optical platform of the laboratory, which exhibits low levels of equipment miniaturization and lacks mobility and integration for movement from the laboratory to outdoor testing. This article proposes a portable atomic antenna with a waveguideintegrated metallic mesh resonator (MMR) to synergize these methods, aiming for system integration and improving sensitivity for deep-space exploration applications. We developed modular 852 and 509 nm fiber systems, laser frequency locking architecture. Thus, a portable atomic antenna is realized with a smaller volume (0.1 & times; 0.25 & times; 0.3 m(3)), lighter weight (26 kg), and narrow probe laser linewidth (5.4 kHz). The experimental investigations were conducted at 8.3 GHz using a vapor cell in the resonators. Spectral measurements indicate that the MMR provides enhancement factors of 24.5 dB. The MMR achieves continuous frequency reconfiguration across 7.49-8.78 GHz by mechanical tuning while significantly reducing field distortions compared to traditional pin-based tuning systems. When MMR was used for Rydberg atomic heterodyning, the sensitivity improved significantly 14.3 nV/cm/ root Hz, which is a 24.5 dB improvement in sensitivity than when MMR was not used. This research represents a significant low-SWaP advancement toward the practical application of Rydberg atomic antennas.

Rydberg atom with resonators is regarded as promising atomic receivers to surpass conventional receivers' sensitivity. However, previous research has presented diverse open resonator structures, focusing on design yet lacking in theoretical guidance. Here we bridge this gap by elucidating the fundamental principles of local enhancement in open resonators, which guides us to adopt positive countermeasures aimed at maximizing the electric-field local enhancement ability and avoid blindly modifications. To overcome limitations of injection-type cylindrical resonators, which require external antennas and lack mobility, we propose an enclosed T-shaped resonator (TSR) integrated within a vapor cell for direct C-band coupling. Simulations show that the enhancement factor rises from 27 times of the basic parallel-plate resonator (PPR) to 57 times of the TSR at the same resonant frequency. An experimental validation was performed with an TSR. The TSR has 32.5 dB at 7.83 GHz electric-field local enhancement ability and an electrical size of 0.18 λ.

To address the high computational cost and efficiency-accuracy trade-off in full-wave simulation of large-scale optical metasurfaces, this paper proposes a local approximation method. The progressive simulation scheme, based on "subdomain partitioning and boundary-condition optimization," transitions from a single meta-unit periodic subdomain to a perfectly matched layer (PML) overlapping subdomain approach. This overcomes the neglect of inter-meta-atom coupling inherent in traditional field-stitching and enhances local near-field accuracy. Validation on a one-dimensional metalens model shows that optimal agreement with full-wave simulation is achieved when both central and overlapping subdomains contain four meta atoms under PML conditions.

The high-efficiency Rydberg field probe (RFP), as the core of Rydberg atomic receivers, has attracted widespread attention due to its advantages of high sensitivity and high integration. This letter presents a broadband right-hand circularly polarized (RHCP) enhancement resonator with unidirectional receiving beam. It can be combined with RFP to enhance the detection sensitivity of the Rydberg atomic receiver. The experimental results demonstrate the excellent broadband CP response of the resonator, with a 3-dB axial ratio (AR) bandwidth of 180 MHz. Using the AC stark effect, the resonator achieves an enhancement of 25.4-28.1 dB for RHCP microwaves (MW), with an optimal AR of 2.15 dB at 2.32 GHz. This designed resonator further expands the range of Rydberg atomic receivers in CP and directional reception applications.

In this letter, 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 mu V/cm root Hz. However, with the presence of our MSRR, the sensitivity significantly improved to 29.09 nV/cm root 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.

Highly sensitive detection of microwave (MW) fields throughout ultra-wideband spectrum is always an important subject in metrology, electromagnetism and cosmology. Rydberg atomic electrometers, which implement electric field measurements by detecting the disturbance of atomic energy levels, have the potentials to breakthrough the sensitivity and size limits of conventional sensors. However, due to the discrete structure of the energy levels, current measurements can only exhibit high sensitivity at the discontinuous frequencies which correspond to certain transitions. In this work, by implementing energy level modulation of Rydberg atom through Zeeman effect, we achieve continuous highly sensitive MW fields detection within 1-40 GHz ultra-wideband spectrum where the detection sensitivity is roundly below 65 nV cm-1 Hz-1/2, which is 2-3 orders of magnitude lower than that of the state-of-the-art continuous measurement architectures. The proposed method is expected to expand the working bandwidth from MHz to THz and therefore greatly accelerate the practical applications in the areas of radar and electronic reconnaissance.

The Rydberg atomic receiver (RAR) has great potential for application in quantum microwave (MW) sensing due to its advantages of self-calibration and high sensitivity. However, the linearly polarized (LP) response of most RARs will reduce the sensitivity to the circularly polarized (CP) MW fields. To address this, we propose a frequency-reconfigurable CP enhancement resonator for RARs. The resonator can convert incident right-hand CP (RHCP) MW fields into LP-enhanced fields for atomic sensing. Frequency reconfiguration is achieved by adjusting the equivalent capacitance of the resonant circuit. The results show that the resonator achieves continuous frequency tuning within the range of 1.606-1.73 GHz, with an optimal axis ratio (AR) as low as 1.93 dB at 1.68 GHz. Based on the AC Stark effect, the enhancement factor (EF) for RHCP MW fields ranges from 20.2 to 24.8 dB across the reconfigurable band. This design provides key technical support for the adaptation of RARs to CP dynamic sensing scenarios.

As a new type of antenna, the Rydberg atomic antenna, with the outstanding advantages of size-independence from the operating wavelength and ultra-wideband characteristics covering the DC to THz, shows important application potentials in the fields of ultra-wideband communication and terahertz detection. At present, the research on its pattern is mainly based on the methods of EIT-AT and AC Stark, while the pattern characteristics in the superheterodyne method have not been clarified. In this paper, the pattern of the Rydberg atomic antenna is tested under the conditions of resonant frequency and non-resonant frequency with the fiber-coupled integrated atomic vapor cell as the experimental object. The experimental results show that the pattern characteristics in the superheterodyne method no longer depend only on the laser polarization, and the polarization of the local oscillation also becomes an influencing factor. This paper clarifies the pattern characteristics of the Rydberg atomic antenna under the superheterodyne method, which provides an important basis for the design and performance optimization in the subsequent practical applications.

Resonant structures provide a promising approach to significantly enhance the sensing sensitivity of Rydberg atomic receivers. However, conventional resonators predominantly operate at fixed frequencies, thereby constraining the intrinsic broadband response capabilities of Rydberg atoms. This study introduces a broadband frequency reconfigurable resonator (BFRR) engineered to augment sensitivity while preserving the broadband characteristics of atomic receivers. By employing varactor diodes to dynamically adjust equivalent capacitance and PIN diodes to selectively activate distinct inductive branches, the BFRR achieves continuous electronic tuning from 231 to 586 MHz, corresponding to a relative bandwidth of 86.9%. In OFF-resonant atomic heterodyne configurations, the integration of the BFRR enhances sensitivity by nearly two orders of magnitude across the tuning range, attaining a sensitivity of 30.4 (nV/cm)/ root Hz at 564.2 MHz. This advancement significantly improves both the sensitivity and broadband adaptability of Rydberg atomic receivers, thereby offering essential support for progress in quantum electrometry.

Rydberg atomic receivers (RARs) have emerged in the field of quantum precision measurement due to high sensitivity and self-calibration. In this letter, we demonstrate a compact tunable enhancement resonator (CTER) for enhancing the detective sensitivity of the RAR. The resonator consists of two printed circuit board (PCB) substrates and a copper tuning column, which achieves resonant frequency variation by continuously sliding the copper tuning column. During the measurement, we have achieved electric field enhancement in the 210 MHz to 308.6 MHz band with a relative bandwidth of 38% and the enhancement factor ranging from 38 dB to 47 dB. By adjusting the height of the CTER, different sizes of atomic vapor cells can be accommodated while maintaining good enhancement. In the off-resonant region, the detective sensitivity of the RAR with and without CTER at 223.7 MHz were measured at 179.37 nV & sdot;cm(-1)& sdot;Hz(-1/2) and 40.16 mu V & sdot;cm(-1)& sdot;Hz(-1/2) by utilizing the Rydberg atomic heterodyne technique, respectively. Furthermore, the CTER displays a compact electrical size, approximately 3.37x 10(-5) lambda(3) in comparison to other resonators, which facilitates the miniaturization and integration of the RAR. Its remarkable resonance characteristics and broadband tuning capability provide support for achieving high-sensitivity and broadband quantum microwave measurements.

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)/$\sqrt{\text{Hz}}$, 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.

Rydberg atom, which exhibits a strong response to weak electric fields, is regarded as a promising atomic receiver to surpass the sensitivity of conventional receivers. However, its sensitivity is strongly limited by the noise coming from both classical and quantum levels, and how to enhance it significantly remains challenging. In theory, we aim to optimize the laser array, highlighting the importance of coherence among microwave signals and the uniformity of laser beam power within the array, to enhance the signal-to-noise ratio (SNR) and elevate sensitivity to a new standard. To enhance practical application mobility and integration, we propose two optimization schemes: a six-port fiber-coupled vapor cell probe array and cascaded diffraction gratings. We maintain steady MW signal coherence in the laser array by using identical vapor cells and positioning the probe lasers on the incident wave's equal phase plane. Our findings reveal that the wavefront phase difference for the six-port fiber-coupled vapor cell array is 10 degrees, while the cascaded diffraction gratings show a 16 degrees difference, with laser intensity uniformity reaching 90.4%. In our experiment, a 4.6-dB SNR enhancement was achieved by utilizing the cascaded diffraction gratings to generate 2 x 2 probe laser arrays compared to the performance of a laser beam, which can be enhanced further just by adding more laser beams. In particular, a 2 x 2 laser array experimental verification yielded 19 nv/cm/root Hz @8.57 GHz. More importantly, the intermediate signals of the laser array maintain coherence. Therefore, SNR improvement is allowed even in detecting weak target signals amid strong noise and clutter. The results could offer an avenue for the design and optimization of ultrahigh-sensitivity Rydberg atomic receivers and promote applications in cosmology, meteorology, communication, and MW quantum technology.

A frequency-tunable resonator used for enhancing electric field incident to Rydberg atoms is proposed in this paper. The simulation results show that the resonator is able to provide local electric field gain higher than 40 dB (100 times). The resonator is made of copper and has the largest size less than 70 millimeters. By moving the copper tunning patch along copper rod, the resonating frequency can be continuously tunable in the whole L band ($1 \text{GHz} \sim 2 \text{GHz}$). The sensitivity of Rydberg atoms electricfield sensing system will get improved with the resonator, which is important to the development of atom radio.

Rydberg atomic electric field detection technology, as a novel quantum precision detection method, offers high detection sensitivity, this feature makes Rydberg atomic sensors (RASs) have excellent capabilities in measuring weak signals. However, the current detection sensitivity of RASs is far from the expected level. Due to the characteristic of Rydberg atoms responding to electric field components, the electric field enhancement structure (EFES) has attracted widespread attention as an effective means to improve detection sensitivity. However, the electric dimension of EFES is usually small, and the E-Gain that EFES can provide has limitations. Integrating EFES with a parabolic reflector (PR) is a simple and effective way to further enhance the E-Gain through the gain brought by the large aperture of the PR, thereby improving the electric field detection sensitivity of RASs. However, the current research on EFES is usually omnidirectional enhancement, which fails to meet the parabolic antenna's requirement for the directivity of the feed. We proposed a directional EFES to enhance the electric field in a specific direction, replacing the feed of the parabolic antenna. Combining this EFES with the PR can further increase the E-Gain on the basis of the EFES, thereby improving the electric field detection sensitivity. The EFES achieves a maximum E-Gain of 40 dB at 1.69 GHz, which combined with the PR, the E-Gain reaches 52 dB.

In this article, we propose a tunable multilayered resonator (TMR) to achieve broadband high-sensitivity sensing within a deep-subwavelength structure. The proposed TMR significantly enhances the incident electric field for Rydberg atoms, improving the sensitivity of the room-temperature atomic sensor. Additionally, by incorporating varactor diodes, the resonant frequency of the TMR can be dynamically controlled by adjusting the diode bias voltage. In the experiment, the TMR realized a 45.26% relative bandwidth, ranging from 13.19 MHz to 19.16 MHz. Furthermore, the sensitivity of the system reached 0.13 µV/cm/Hz in the presence of the TMR at 19.16 MHz, compared to only 24.59 µV/cm/Hz without the TMR.

Atomic receiver system based on Rydberg atoms is expected to achieve breakthroughs in the frequency range and sensitivity of electric field measurements. A miniaturized electric field enhancement structure, which can be utilized for electric field sensing of Rydberg atoms in the shortwave band (3-30 MHz), is proposed in this paper. It can achieve an extremely small electric dimension (0.0054 lambda x 0.0054 lambda x 0.0006 lambda) and provides an electric field enhancement factor of 77.5 dB at 10.4 MHz. With this miniaturized electric field enhancement structure, the sensitivity of the atomic receiver systems in the shortwave band can be significantly enhanced, thereby facilitating precision measurements at ultra-small electrical dimensions.

The integration of electric field enhancement structures (EFESs) with Rydberg atomic sensors (RASs) has garnered considerable interest due to their potential to enhance detection sensitivity in quantum measurement systems. Despite this, there is a dearth of research on the directional response of EFES, and the analysis of the three-dimensional (3D) patterns of RAS remains a formidable challenge. RASs are employed in non-destructive measurement techniques, and are responsive to electric fields, primarily serving as reception devices. However, analyzing their reception patterns is a complex task that requires a sophisticated approach. To address this, we adopt characteristic mode (CM) analysis to illustrate the omnidirectional performance of RAS. According to the CM theory, the reception pattern can be calculated by a series of modal currents and their corresponding coefficients. The analytical representation of these coefficients negates the need for time-consuming full-wave (FW) numerical simulations, which are typically required to generate EFES patterns due to the necessity of scanning numerous angle parameters. This approach significantly reduces the complexity of solving EFES patterns, and provides insightful guidance for the design process. To validate the efficacy of our proposed method, we construct three prototypes. The results indicate that the final model resonates at 1.96 GHz, achieving an electric field gain of 25 dB and an out-of-roundness of 2.4 dB. These findings underscore the effectiveness of our method in analyzing EFES patterns, highlighting its potential for future applications in the field.