Spaceborne radar remote sensing of the earth system is essential to study natural and man-made changes in the ecosystem, water and energy cycles, weather and air quality, sea level, and surface dynamics. A major challenge with current approaches is the lack of broad spectrum tunability due to narrow band microwave electronics, that limit systems to specific science variable retrievals. This results in a significant limitation in studying dynamic coupled earth system processes such as surface and subsurface hydrology, where broad spectrum radar remote sensing is needed to sense multiple variables simultaneously. Rydberg atomic sensors are highly sensitive broad-spectrum quantum detectors that can be dynamically tuned to cover micro-to-millimeter waves with no requirement for band-specific electronics. Rydberg atomic sensors can use existing transmitted signals such as navigation and communication satellites to enable remote sensing. We demonstrate remote sensing of soil moisture, an important earth system variable, via ground-based radar reflectometry with Rydberg atomic systems. To do this, we sensitize the atoms to XM satellite radio signals and use signal correlations to demonstrate use of these satellite signals for remote sensing of soil moisture. Our approach provides a step towards satellite-based broad-spectrum Rydberg atomic remote sensing.
Spaceborne radar remote sensing of the earth system is essential to study natural and man-made changes in the ecosystem, water and energy cycles, weather and air quality, sea level, and surface dynamics. A major challenge with current approaches is the lack of broad spectrum tunability due to narrow band microwave electronics, that limit systems to specific science variable retrievals. This results in a significant limitation in studying dynamic coupled earth system processes such as surface and subsurface hydrology, where broad spectrum radar remote sensing is needed to sense multiple variables simultaneously. Rydberg atomic sensors are highly sensitive broad-spectrum quantum detectors that can be dynamically tuned to cover micro-to-millimeter waves with no requirement for band-specific electronics. Rydberg atomic sensors can use existing transmitted signals such as navigation and communication satellites to enable remote sensing. We demonstrate remote sensing of soil moisture, an important earth system variable, via ground-based radar reflectometry with Rydberg atomic systems. To do this, we sensitize the atoms to XM satellite radio signals and use signal correlations to demonstrate use of these satellite signals for remote sensing of soil moisture. Our approach provides a step towards satellite-based broad-spectrum Rydberg atomic remote sensing.
Detecting microwave signals over a wide frequency range has numerous advantages as it enables simultaneous transmission of a large amount of information and access to more spectrum resources. This capability is crucial for applications such as microwave communication, remote sensing, and radar. However, conventional microwave receiving systems are limited by amplifiers and band-pass filters that can only operate efficiently in a specific frequency range. Typically, these systems can only process signals within a three-fold frequency range, which limits the data transfer bandwidth of the microwave communication systems. Developing novel atom-integrated microwave sensors, for example, radio frequency (RF)-chip coupled Rydberg atomic receiver, provides opportunities for a large working bandwidth of microwave sensing at the atomic level. Here, an ultra-wide dual-band RF sensing scheme is demonstrated by space-division multiplexing two RF-chip-integrated atomic receiver modules. The system can simultaneously receive dual-band microwave signals that span a frequency range exceeding 6 octaves (300 MHz and 24 GHz). This work paves the way for multi-band microwave reception applications within an ultra-wide range by RF-chip-integrated Rydberg atomic sensor.
Detecting microwave signals over a wide frequency range has numerous advantages as it enables simultaneous transmission of a large amount of information, and access to more spectrum resources. This capability is crucial for applications such as microwave communication, remote sensing, and radar. However, conventional microwave receiving systems are limited by amplifiers and band-pass filters that can only operate efficiently in a specific frequency range. Typically, these systems can only process signals within a three-fold frequency range, which limits the data transfer bandwidth of the microwave communication systems. Developing novel atom-integrated microwave sensors, for example, radio frequency (RF)-chip coupled Rydberg atomic receiver, provides opportunities for a large working bandwidth of microwave sensing at the atomic level. Here, an ultra-wide dual-band RF sensing scheme is demonstrated by space-division multiplexing two RF-chip-integrated atomic receiver modules. The system can simultaneously receive dual-band microwave signals that span a frequency range exceeding 6 octaves (300 MHz and 24 GHz). This work paves the way for multi-band microwave reception applications within an ultra-wide range by RF-chip-integrated Rydberg atomic sensor.
Rydberg-atom receivers aim for ultra-high sensitivity to microwave fields through various techniques, but receiving satellite signals has remained a significant challenge, due to the difficulty of capturing weak microwaves over long distances. In this work, we introduce a high-gain antenna to focus satellite signals, and then apply into an atomic cell via a microwave cavity. Using microwave-enhanced coupling, the minimum detectable power of incident microwave is down to -128 dBm, and the corresponding sensitivity is estimated as 21 nV/cm/Hz1/2 at frequency of 3.80 GHz. Furthermore, beacon signal from geostationary satellites is captured with Rydberg sensors for the first time, without the need for a low-noise amplifier. And C-band modulated signals are read out with a signal-to-noise ratio of 8 dB. Our results mark a significant breakthrough in facilitating satellite communications using Rydberg-atom receivers.
Rydberg electric field sensors exploit the large number of Rydberg resonances to provide sensitivity over a broad range of the electromagnetic spectrum. However, due to the difficulty of accessing resonant Rydberg states at ultra-high frequency (UHF) and below, ubiquitous bands in the world's current wireless communications infrastructure, they currently fall, short in sensitivity in this range. We present a resonant Rydberg electric field sensor operating in the UHF band using a dual-optical dual-microwave spectroscopy scheme. Adding an additional microwave photon allows us to access transitions between Rydberg states with higher angular momentum (L=3→4), which have lower resonant frequencies than transitions typically used in Rydberg sensors. We discuss the applicability of this type of sensor across the UHF band and below and measure the resonant sensitivity of our system at 2.3 GHz to be 70(5) μV m−1 Hz−1∕2, 57 times better than the measured sensitivity with a far off-resonant probing scheme at this frequency. We also show the effectiveness of this sensing scheme by measuring Sirius XM satellite radio (2.320–2.345 GHz) received outside the laboratory and rebroadcast onto the atoms.
Rydberg atoms are atoms in their highly excited energy states. The physical properties of Rydberg atoms in the presence of external fields play an important role in quantum precision measurement. In recent years, radio-frequency electric field sensing based on Rydberg atoms has attracted significant interest. It is widely recognized as an electromagnetic sensing system fundamentally different from traditional ones. As a quantum sensor, it is expected to surpass several foundational limitations of traditional receivers, such as sensitivity, dynamic range and frequency bandwidth. It was reported that Rydberg sensing systems can sense microwaves of frequencies from DC up to 1THz. Its quantum nature would possibly avoid internal thermal (Johnson) noise, even at room temperature. Recent demonstrations have also observed high precision for terahertz imaging, strong fields sensing, proof-of-principle communication. However, limitations of this novel system have not been addressed, especially for a practical radar, communication or electronic warfare system. Here in this work, we first compare the architectures of different microwave receivers and then analyze the metrics of Rydberg microwave receivers, such as instantaneous bandwidth and dynamic range based on experimental results. We concluded by pointing out several main obstacles to overcome for realizing a practical state-of-the-art microwave receiver.
Quantum Rydberg atom-based radio frequency (RF) sensors exploit the exceptional sensitivity of highly excited atomic states to detect electromagnetic fields with very high precision, offering potential advances in telecommunications, radar and microwave radiometer systems, GNSS-Reflectometers, and electromagnetic compatibility testing. This study presents a detailed MATLAB simulation analysis of radio-frequency sensors modeled as a five-level rubidium-87 (Rb-87) system under the influence of RF and optical fields. The simulation leverages the Lindblad master equation to capture the coherent evolution, the spontaneous emission, the collisional dephasing, and the field-induced ionization. For an external RF electric field of E0 = 100 mV/m, a frequency sweep from 10MHz to 10GHz reveals the impact of noise: an ideal case just limited by quantum noise yields a sensitivity of 0.01 µV/m/ v Hz and a SNR of 177dB, while for E0 = 10 mV/m and a realistic noise (-130 dBm/Hz) the sensitivity worsens to 72 - 633 µV/m/ v Hz and a SNR of 72 dB. The study investigates the effects of RF field amplitude, atom density, and environmental parameters such as residual magnetic field and ambient temperature, in the sensitivity and bandwidth of these promising receivers, offering a framework to optimize Rydberg-based sensing technologies for Earth Observation, Communication and Navigation systems.