Rydberg atom-based antennas exploit the quantum properties of highly excited Rydberg atoms, providing unique advantages over classical antennas, such as high sensitivity, broad frequency range, and low intrinsic noise. Despite the increasing interests in their applications in antenna and communication engineering, some key properties, involving the lack of polarization multiplexing and isotropic reception without mutual coupling, remain unexplored in the analysis of Rydberg atom-based multiple-input–multiple-output (MIMO) communications. Generally, the design considerations for any antenna, even for atomic ones, can be extracted to factors, such as radiation pattern, efficiency, and polarization, allowing them to be seamlessly integrated into existing system models. In this letter, we extract the antenna properties from relevant quantum characteristics, enabling electromagnetic modeling and capacity analysis of Rydberg MIMO systems in both far-field and near-field scenarios. Focusing on spatial multiplexing performance under the same signal-to-noise level, our results indicate that Rydberg atom-based antenna arrays offer certain advantages over classical dipole-type arrays in single-polarization MIMO communications.
Rydberg atom-based antennas exploit the quantum properties of highly excited Rydberg atoms, providing unique advantages over classical antennas, such as high sensitivity, broad frequency range, and low intrinsic noise. Despite the increasing interests in their applications in antenna and communication engineering, some key properties, involving the lack of polarization multiplexing and isotropic reception without mutual coupling, remain unexplored in the analysis of Rydberg atom-based multiple-input–multiple-output (MIMO) communications. Generally, the design considerations for any antenna, even for atomic ones, can be extracted to factors, such as radiation pattern, efficiency, and polarization, allowing them to be seamlessly integrated into existing system models. In this letter, we extract the antenna properties from relevant quantum characteristics, enabling electromagnetic modeling and capacity analysis of Rydberg MIMO systems in both far-field and near-field scenarios. Focusing on spatial multiplexing performance under the same signal-to-noise level, our results indicate that Rydberg atom-based antenna arrays offer certain advantages over classical dipole-type arrays in single-polarization MIMO communications.
Rydberg atomic quantum receivers have been seen as novel radio frequency measurements and the high sensitivity to a large range of frequencies makes it attractive for communications reception. However, current implementations of Rydberg array antennas predominantly rely on simple stacking of multiple single-antenna units. While conceptually straightforward, this approach leads to substantial system bulkiness due to the unique requirements of atomic sensors, particularly the need for multiple spatially separated laser setups, rendering such designs both impractical for real-world applications and challenging to fabricate. This limitation underscores the critical need for developing multiplexed Rydberg sensor array architectures. In the domain of conventional RF array antennas, hybrid analog-digital beamforming has emerged as a pivotal architecture for large-scale millimeter-wave (mmWave) multiple-input multiple-output (MIMO) systems, as it substantially reduces the hardware complexity associated with fully-digital beamforming while closely approaching its performance. Drawing inspiration from this methodology, we conduct a systematic study in this work on the design principles, equivalent modeling, and precoding strategies for low-complexity multiplexed Rydberg array, an endeavor crucial to enabling practical and scalable quantum-enhanced communication systems.
Superdirective receive arrays, whose gain can exceed that of traditional antenna arrays, have been historically challenging to realize due to high sensitivity to white noise, strong mutual coupling, and the complexity of designing receive matching networks in conventional systems. This paper proposes and analyzes a novel superdirective receiver architecture based on an array of Rydberg atomic sensors to overcome these fundamental limitations. By leveraging the quantum properties of Rydberg atoms, the proposed receiver is inherently immune to the internal thermal noise that plagues traditional receivers. As a result, the system performance is primarily limited by external background noise and fundamental quantum noise. We develop a comprehensive signal and noise model and the-oretically derive the upper bound on the directivity gain for the proposed Rydberg-based receiver. Furthermore, we prove that for multi-user scenarios, the effective channel vectors for different users become asymptotically orthogonal as the number of sensors approaches infinity, enabling high-capacity spatial multiplexing even with deep sub-wavelength element spacing. Extensive simulations demonstrate the superior performance of the proposed system over traditional superdirective receivers and validate our theoretical findings. The results highlight Rydberg atomic arrays as a promising technology for developing ultra-sensitive, compact, and broadband superdirective receivers for next-generation communication and sensing applications.
The advancement of Rydberg atoms in quantum information technology is driving a paradigm shift from classicalradio-frequency(RF) receivers to Rydberg atomic receivers. Capitalizing on the extreme sensitivity of Rydberg atoms to external electromagnetic fields, Rydberg atomic receivers are capable of realizing more precise radio-wave measurements than RF receivers to support high-performance wireless communication and sensing. Although the atomic receiver is developing rapidly in quantum-physics domain, its integration with wireless communications is at a nascent stage. In particular, systematic methods to enhance communication performance through this integration are yet to be discovered. Motivated by this observation, we propose in this paper to incorporate Rydberg atomic receivers intomultiple-input-multiple-output(MIMO) communication, a prominent 5G technology, as the first attempt on implementing atomic MIMO receivers. To begin with, we provide a comprehensive introduction on the principles of Rydberg atomic receivers and build on them to design the atomic MIMO receivers. Our findings reveal that signal detection of atomic MIMO receivers corresponds to a non-linear biasedphase retrieval(PR) problem, as opposed to the linear Gaussian model adopted in classical MIMO systems. Then, to recover signals from this non-linear model, we modify the Gerchberg-Saxton (GS) algorithm, a typical PR solver, into a biased GS algorithm to solve the biased PR problem. Moreover, we propose a novel Expectation-Maximization GS (EM-GS) algorithm to cope with the unique Rician distribution of the biased PR model. Our EM-GS algorithm introduces a high-pass filter constructed by the ratio of Bessel functions into the iteration procedure of GS, thereby improving the detection accuracy without sacrificing the computational efficiency. Finally, the effectiveness of the devised algorithms and the feasibility of atomic MIMO receivers are demonstrated by theoretical analysis and numerical simulation.
Rydberg atomic quantum receivers (RAQRs) are emerging quantum precision sensing platforms designed for receiving radio frequency (RF) signals. It relies on the creation of Rydberg atoms from normal atoms by exciting one or more electrons to a very high energy level, thereby making the atom sensitive to RF signals. RAQRs realize RF-to-optical conversions based on atom-light interactions relying on the so-called electromagnetically induced transparency (EIT) and Autler- Townes splitting (ATS) so that the desired RF signal can be read out optically. The large dipole moments of Rydberg atoms associated with rich choices of Rydberg states facilitate an ultra-high sensitivity (~nv⁄cm/√Hz) and an ultra-broadband tunability (direct-current to Terahertz). RAQRs also exhibit compelling scalability and lend themselves to the construction of innovative, compact receivers. Initial experimental studies have demonstrated their capabilities in classical wireless communications and sensing. To fully harness their potential in a wide variety of applications, we commence by outlining the underlying fundamentals of Rydberg atoms, followed by the principles and schemes of RAQRs. Then, we overview the state-of-the-art studies from both physics and communication societies. Furthermore, we conceive Rydberg atomic quantum single-input single-output (RAQ-SISO) and multiple-input multiple- output (RAQ-MIMO) schemes to facilitate the integration of RAQRs with classical wireless systems. Finally, we conclude with a set of potent research directions.
Rydberg atomic quantum receivers (RAQRs) are capable of receiving multi-band radio-frequency (RF) signals simultaneously, which are expected to break Chu's limit for classical electronic antennas. However, signals from different users will interfere with each other in the optical intermediate frequency (IF) domain of the multi-band quantum receiver, which is termed the IF interference (IFI) problem. To address this problem, in this paper, we propose a multi-input multi-output (MIMO) architecture for Rydberg atomic quantum receiver (RAQ-MIMO) by exploiting the additional spatial diversity of MIMO receivers. Specifically, by applying the dynamic signal model of RAQRs, we clarify the physical relationship between the quantum local oscillator (LO) configurations and the multi-band gains with the concept of quantum transconductance. Then, with the quantum transconductance-based signal model, we formulate the spectral efficiency (SE) maximization problem and further propose the quantum weighted minimum mean square error (qWMMSE) algorithm, which jointly optimizes the quantum LO configurations and the classical precoder/combiner matrices. Furthermore, we test the qWMMSE algorithm within the standard space division multiple access (SDMA) scheme and the frequency division multiple access (FDMA) scheme. Simulation results demonstrate that the qWMMSE optimization framework can significantly improve the SE of RAQ-MIMO systems for both multiple access schemes, and that RAQ-MIMO systems can outperform classical electronic receiver-based multi-user MIMO systems by eliminating the mutual coupling effect between classical antennas.
Physical layer security (PLS) provides information-theoretic confidentiality for next-generation wireless systems, yet its practical deployment is fundamentally constrained by the sensitivity and noise characteristics of classical radio receivers. Recent advances in quantum sensing, particularly Rydberg atom-based receivers (RAQRs), present a promising approach to address these limitations. This paper introduces a Rydberg atomic quantum multiple-input multiple-output (RAQ-MIMO) architecture for secure multi-user uplink communications, where an array of Rydberg vapor cells functions as a high-sensitivity, reconfigurable receiving front-end. We develop a comprehensive end-to-end signal and channel model that incorporates quantum sensor response, wireless fading, and eavesdropper behavior under passive interception. To maximize the achievable secrecy rate, we propose a joint optimization framework that adaptively tunes key system degrees of freedom, including the Rabi frequency of the local oscillator, phase configuration, digital combining matrix, and user transmit power. Extensive simulations validate that RAQ-MIMO substantially outperforms classical MIMO in terms of secrecy rate across varying transmission distances, power budgets, and user loads—particularly under low-signal to noise ratio (SNR) and extended-range regimes. Our work establishes a quantum-sensing-assisted security foundation for future high-assurance wireless networks, bridging atomic physics with scalable communication system design with scalable communication system design under narrowband operation.