Rydberg atoms enable ultrasensitive microwave detection through their exceptional polarizability, but their use as decoders in communications is limited by a scarcity of scalable frequency points, which arises from cross-modulation in multifrequency fields and narrow operational bandwidth of the sensor. This work introduces a digital communication framework that integrates orbital angular momentum (OAM) with frequency-division multiplexing (FDM). By mapping each FDM subcarrier to a distinct OAM, we construct a 2-D multiplexing space that combines the spectral dimension of FDM with the spatial-phase dimension of OAM. As a result, the theoretical channel capacity scales as the product of the capacities attainable in each individual dimension, thereby overcoming the inherent limit of conventional single-dimensional multiplexing. OAM features are mapped to Rydberg electromagnetically induced transparency (EIT) spectra through quadrupole-gradient coupling, enabling simultaneous OAM identification and FDM demodulation using spectral templates, without separate detectors. Simulations show greater than 98% overall recognition accuracy under the transition$|61\text {D}_{5/2}\rangle \to |63\text {P}_{1/2}\rangle $: at an SNR of under 10 dB, OAM mode 1 is identified with 99.6% accuracy (0.4% misclassification) and OAM mode 0 with 98.1% (1.9% misclassification). Meanwhile, QPSK phase recognition remains greater than 98.5%, with$\varphi _{k}=\pi /2$and$3\pi /2$being 1.5–2% lower than for$\varphi _{k}=0$and$\pi $. This work supports high-performance multifrequency microwave technologies by enhancing capacity and simplifying the architecture.
Rydberg atoms enable ultrasensitive microwave detection through their exceptional polarizability, but their use as decoders in communications is limited by a scarcity of scalable frequency points, which arises from cross-modulation in multifrequency fields and narrow operational bandwidth of the sensor. This work introduces a digital communication framework that integrates orbital angular momentum (OAM) with frequency-division multiplexing (FDM). By mapping each FDM subcarrier to a distinct OAM, we construct a 2-D multiplexing space that combines the spectral dimension of FDM with the spatial-phase dimension of OAM. As a result, the theoretical channel capacity scales as the product of the capacities attainable in each individual dimension, thereby overcoming the inherent limit of conventional single-dimensional multiplexing. OAM features are mapped to Rydberg electromagnetically induced transparency (EIT) spectra through quadrupole-gradient coupling, enabling simultaneous OAM identification and FDM demodulation using spectral templates, without separate detectors. Simulations show greater than 98% overall recognition accuracy under the transition∣61D5/2⟩→∣63P1/2⟩: at an SNR of under 10 dB, OAM mode 1 is identified with 99.6% accuracy (0.4% misclassification) and OAM mode 0 with 98.1% (1.9% misclassification). Meanwhile, QPSK phase recognition remains greater than 98.5%, withφk=π/2and3π/2being 1.5–2% lower than forφk=0andπ. This work supports high-performance multifrequency microwave technologies by enhancing capacity and simplifying the architecture.
The orbital angular momentum (OAM) technology, promising for future communications, radar, and quantum information processing, confronts challenges in OAM detection of the microwave photons, due to the noise and equipment complexity. Conventional detection approaches based on gyrotron systems, which demand vacuum and high-voltage environments, prove impractical for scalable applications. Thus, we introduce a Rydberg-atom-based architecture for OAM detection of vortex microwave photons, which operates in normal pressure and low voltage with miniaturized equipment. Specifically, leveraging the unique dipole-forbidden, quadrupole-allowed transitions of Rydberg atoms, we can receive the vortex microwave photons and identify the corresponding intrinsic OAM (IOAM), with precise frequency alignment by external electrode plates for fine-tuning. Moreover, experimental observations reveal the insight of Autler–Townes splitting, confirming that the OAM of microwave photons can couple to atomic energy levels through electric-quadrupole interactions, inducing a dynamic Stark effect. In contrast, the experiments with plane microwave photons, i.e., the OAM mode is zero, show the result with only static stark broadening rather than the peak splitting, which highlights the critical role of quadrupole transitions in OAM detection. Significantly, this approach overcomes the limitations of conventional techniques requiring high-energy superconducting devices or high-voltage setups, offering a low-cost, scalable solution for efficient vortex microwave photons detection with promising applications, e.g., secure wireless communications and quantum radars.
Rydberg atoms have been extensively utilized in microwave measurement with high sensitivity, which has great potential in the field of communication. In this study, we discuss the digital communication based on a Rydberg atomic receiver under simultaneously coupling by resonant and near detuning microwaves. In addition, we verify the feasibility of the Rydberg atom-based frequency division multiplexing (FDM) in microwave communication. We demonstrate the principle and performance of the atom-based FDM receiver by applying amplitude modulation (AM) and frequency modulation (FM), respectively. To demonstrate the actual communication performance at different data transfer rates, we consider monochromatic images as an example. The experimental results show that the maximum acceptable data transfer rate of both AM and FM is about 200 kbps, whereas their maximum bit error rates (BER) is less than 5%. When compared with the traditional electronic receiver, this atomic receiver, which is compatible with FDM, has numerous advantages, such as small size, low power consumption, and high sensitivity. Furthermore, this receiver has a strong ability of anti-electromagnetic interference, and the signals transmitted do not interfere with each other in different channels.
Communication technologies advance toward secure communication, with frequency hopping communication (FH-C) widely used. However, traditional FH-C is limited by slow hopping speed, narrow bandwidth, and a few hopping points. Rydberg atoms offer a solution but face challenges like poor non-resonant microwave sensitivity and local oscillator synchronization limits. Here, we propose a frequency-hopping receiver based on atomic heterodyne detection that employs high orbital angular momentum (high-OAM) Rydberg states for resonant detection of rapidly hopping radio-frequency signals across multiple, widely separated frequency bands. The high-OAM Rydberg atoms ( l =3,4,5) resonantly detect 315 MHz, 1.7 GHz, and 29.74 GHz RF hopping signals (spanning 6 octaves). With heterodyne detection and a continuous excitation scheme, the system eliminates spectral establishment time, achieving 60 khops/s without transmitter-receiver synchronization, and uses frequency combs to extend hopping points to 5 MHz around resonant frequencies. These advances demonstrate the potential of Rydberg-atom–based receivers for high-speed and wide-band frequency-hopping communication.
To achieve multi-channel parallel transmission of complex signals and enhance spectral efficiency, this study presents a Rydberg atomic antenna system that can demonstrate multiplexed communication schemes. 852-nm and 509-nm lasers are used to excite cesium atoms into Rydberg states in a vapor cell, while employing differential detection techniques to suppress common-mode noise in order to obtain high signal-to-noise ratio electromagnetically induced transparency (EIT) spectra. Under weak electric field conditions, microwave field coupling causes atomic energy level shifts, resulting in two-photon detuning and rendering the EIT transmission intensity almost linearly dependent on the microwave electric field strength. Based on this effect, the integrated electrode configuration in the atomic cell generates a time-varying electric field, which can measure the waveforms, amplitudes, and frequencies of microwave and low-frequency electric fields. According to this principle, we decompose complex chaotic signals into three-dimensional orthogonal electric field components in order to demonstrate time-division multiplexing (TDM) of three-channel signals. Meanwhile, frequency-division multiplexing (FDM) is realized by modulating the x -, y -, z - channels with 3 kHz, 5 kHz, and 4 kHz carriers, respectively. The quantitative analysis of the parameters related to the transmition signal and the reference signal reveals high-fidelity reconstruction, with the fidelity levels reaching 95% for TDM and 90% for FDM. These results validate the feasibility of using optical atomic antennas to reconstruct complex signal waveforms and emphasize the potential of Rydberg-based systems in high-performance electromagnetic field sensing and communication applications.
Optical vortex beams (OVBs) carrying orbital angular momentum (OAM) offer access to an unbounded set of orthogonal states, enabling a dramatic increase in the information capacity for optical communication systems. However, practical OAM detection in telecommunication platforms remains challenging due to background noise, detector limitations at infrared communication wavelengths, and the destructive nature of conventional sampling methods. Here, we introduce an all-optical, nearly nondestructive OAM detection method based on sum-frequency generation (SFG) that overcomes these limitations by transferring the information on the OAM into a distinct frequency domain. In our scheme, two OVBs─one carrying OAM-encoded information and the other serving as a reference─are coupled within a beta-barium borate (BBO) crystal to generate an SFG signal. Our theoretical and experimental studies demonstrate that SFG efficiency is governed by the spatial overlap of the interacting vortex profiles, providing mode-selective and OAM-resolved detection. Crucially, as only a small fraction of the input photons undergo conversion into the nonlinear signal, the original beams remain functionally intact. Since detection is performed exclusively on the upconverted signal in a spectrally distinct visible wavelength region, the signal-to-noise ratio can be improved. Moreover, the SFG signal is generated only when specific OAM states and temporal overlap conditions are simultaneously satisfied, enabling ultrafast and conditionally gated access to the OAM information. This nonlinear selectivity offers enhanced physical-layer security and high-throughput capabilities. Together, our approach provides a robust and versatile platform for advanced OAM-based optical communications and high-capacity photonics applications.
Orbital angular momentum (OAM) of photons provides a promising approach to enhance the capacity, robustness, and functionality of quantum communication systems in optical fibers. With many twist states available, OAM enables high-dimensional encoding, significantly increasing data rates and noise tolerance. This review explores sources, channels, and system architectures for OAM-based quantum communication in fibers. It compares free-space and integrated emitters, discussing in-fiber pair generation and mode conversion pathways that produce fiber-ready single photons and entangled states. For the channels, it details design principles and trade-offs for step-index and ring-core fibers that minimize intermodal coupling and reviews milestones in kilometer-scale single-photon transmission and high-dimensional entanglement transport. On the system side, the review examines coupling, multiplexing, and detection techniques—including mode (de)multiplexers, lanterns, and programmable sorters—and discusses transmission-matrix-based control methods to mitigate dispersion and bending effects. The review concludes with practical guidance and open challenges, such as improving mode selectivity and stability under real-world conditions; developing compact, efficient detectors for many modes; and integrating co-designed error correction schemes. These directions aim to bridge laboratory demonstrations with the deployment of scalable, high-dimensional fiber networks that harness OAM to significantly boost capacity, resilience, and functionality.