We experimentally demonstrate digital communications in the terahertz (THz) band using a rubidium vapor cell as a quantum receiver. We utilize amplitude modulation to encode digital information in THz photons, which are coherently upconverted to optical photons via a Rydberg six-wave-mixing process. We achieve a data transmission rate of up to 1.16 Mbit/s and a tunable bandwidth of up to 142 MHz near a 0.11 THz carrier. With reduced data rate and increased integration time per bit, we demonstrate weak-field THz transmission with a receiver sensitivity in the −130 dBm range. As a proof of principle, we perform an end-to-end transmission of digital color images in the THz band. Our work provides the possibility of THz communication at the single-photon level.
We experimentally demonstrate digital communications in the terahertz (THz) band using a rubidium vapor cell as a quantum receiver. We utilize amplitude modulation to encode digital information in THz photons, which are coherently upconverted to optical photons via a Rydberg six-wave-mixing process. We achieve a data transmission rate of up to 1.16 Mbit/s and a tunable bandwidth of up to 142 MHz near a 0.11 THz carrier. With reduced data rate and increased integration time per bit, we demonstrate weak-field THz transmission with a receiver sensitivity in the −130 dBm range. As a proof of principle, we perform an end-to-end transmission of digital color images in the THz band. Our work provides the possibility of THz communication at the single-photon level.
Single-photon terahertz (THz) detection is one of the most demanding technologies for a variety of fields and could lead to many breakthroughs. Although significant progress has been made in the past two decades, operating it at room temperature still remains a great challenge. Here, we demonstrate, for the first time, a room temperature THz detector at single-photon levels based on nonlinear wave mixing in thermal Rydberg atomic vapor. The low-energy THz photons are coherently upconverted to high-energy optical photons via a nondegenerate Rydberg state involved in a six-wave mixing process, and therefore, single-photon THz detection is achieved by a conventional optical single-photon counting module. The noise equivalent power of such a detector reaches 9.5 × 10−19 W/Hz1/2, which is more than four orders of magnitude lower than the state-of-the-art room temperature THz detectors. The optimum quantum efficiency of the whole-wave mixing process is about 4.3%, with 40.6 dB dynamic range, and the maximum conversion bandwidth is 172 MHz, which is all-optically controllable. The developed fast and continuous-wave single-photon THz detector at room temperature operation has a great potential for portability and chip-scale integration, and could be revolutionary for a wide range of applications in remote sensing, wireless communication, biomedical diagnostics, and quantum optics.
Realization of practical terahertz wireless communications still faces many challenges. The receiver with high sensitivity is important for THz wireless communications. Here we demonstrate a terahertz receiver based on the cesium Rydberg atoms in a room-temperature vapor cell. The minimum detectable THz electric field is calibrated. With this receiver, the phase-sensitive conversion of amplitude-modulated or frequency-modulated terahertz waves into optical signals is performed. The results show that the atomic receiver has many advantages due to its quantum properties. Particularly, the long distance THz wireless communications is achievable using this receiver. Furthermore, the atomic receiver can be used in the THz wireless-to-optical link.
Rydberg atoms, with one highly excited, nearly ionized electron, have extreme sensitivity to electric fields, including microwave fields ranging from 100 MHz to over 1 THz. Here, we show that room-temperature Rydberg atoms can be used as sensitive, high bandwidth, microwave communication antennas. We demonstrate near photon-shot-noise limited readout of data encoded in amplitude-modulated 17 GHz microwaves, using an electromagnetically induced-transparency (EIT) probing scheme. We measure a photon-shot-noise limited channel capacity of up to 8.2 Mbit s−1 and implement an 8-state phase-shift-keying digital communication protocol. The bandwidth of the EIT probing scheme is found to be limited by the available coupling laser power and the natural linewidth of the rubidium D2 transition. We discuss how atomic communication receivers offer several opportunities to surpass the capabilities of classical antennas.
We demonstrate an atom-based amplitude-modulation (AM) receiver for digital communication with a weak continuous frequency carrier using a Rydberg AC Stark effect in a vapor cell and achieve the operating carrier frequency continuously from 0.1 GHz to 5 GHz at a single Rydberg state. A strong local oscillator (LO) field E LO acts as a gain to shift the Rydberg level to a high sensitivity region, and a weak carrier field E Carr keeps the same frequency with the LO field. The digital baseband signals are encoded onto the E Carr using the amplitude modulation technique with the different modulation frequency. The response of Rydberg atom to the baseband signal is probed via a Rydberg electromagnetically induced transparency (EIT). The measured instantaneous bandwidth of the system is about 230 kHz. To demonstrate the performance of our system for an actual communication, we consider a color image as an example, the received image displays that the bit error rate (BER) is less than 5% when the maximum data transfer rate is about 238 kbps. Meanwhile, our system shows the weak carrier field of E Carr ≥ 13.52 μ V/cm can be used for the practical communication with BER less than 5%. Our works break the limitation that EIT-AT based atomic receivers only operate at the near resonant frequencies of the Rydberg transitions, making this emerging of quantum technology close to the practical application with high sensitivity and broad bandwidth.
Up to now, the measurement of radio-frequency (RF) electric field achieved using the electromagnetically-induced transparency (EIT) of Rydberg atoms has proved to be of high-sensitivity and shows a potential to produce a promising atomic RF receiver at resonance between two chosen Rydberg states. In this paper, we study the extension of the feasibility of digital communication via this quantum-based antenna over a continuously tunable RF-carrier at off-resonance. Our experiment shows that the digital communication at a rate of 500 kbps can be performed reliably within a tunable bandwidth of 200 MHz near a 10.22 GHz carrier. Outside of this range, the bit error rate (BER) increases, rising to, for example, 15% at an RF-detuning of ±150 MHz. In the measurement, the time-varying RF field is retrieved by detecting the optical power of the probe laser at the center frequency of RF-induced symmetric or asymmetric Autler-Townes splitting in EIT. Prior to the digital test, we studied the RF-reception quality as a function of various parameters including the RF detuning and found that a choice of linear gain response to the RF-amplitude can suppress the signal distortion. The modulating signal can be decoded at speeds up to 500 kHz in the tunable bandwidth. Our test consolidates the physical basis for reliable communication and spectral sensing over a wider broadband RF-carrier, which paves a way for the concurrent multi-channel communications founded on the same pair of Rydberg states.
Terahertz imaging has become increasingly important across various fields and practical production applications. Achieving both high sensitivity and high speed remains a primary challenge for most current THz imaging technologies. In this work, we present an imaging system based on Rydberg atomic vapor operating at frequencies exceeding 1 THz. By utilizing Cesium 133 atoms coupled with THz waves, de-excitation radiation generated after atomic excitation to Rydberg states converts invisible THz waves into visible light, enabling the acquisition of spatial information and intensity distributions of THz fields. The system achieves a minimum detectable power of 330 fW /s 1/2 per (2.4×2.4) μm 2 , an imaging resolution of approximately 1.7 mm, and an imaging bandwidth of 8.6 MHz. Additionally, the theoretical imaging rate can exceed 1 MHz. The Rydberg-atom-based THz imaging system exhibits a simple structure and is amenable to miniaturization. This THz imaging method holds promise for advancing applications in THz nondestructive testing, biomedical imaging, and concealed object detection.