Rydberg Atomic Quantum Receivers for Classical Wireless Communications and Sensing: Their Models and Performance

Abstract: The significant progress of quantum sensing technologies offer numerous radical solutions for measuring a multitude of physical quantities at an unprecedented precision. Among them, Rydberg atomic quantum receivers (RAQRs) emerge as an eminent solution for detecting the electric field of radio frequency (RF) signals, exhibiting great potential in assisting classical wireless communications and sensing. So far, most experimental studies have aimed for the proof of physical concepts to reveal its promise, while the practical signal model of RAQR-aided wireless communications and sensing remained under-explored. Furthermore, the performance of RAQR-based wireless receivers and their advantages over classical RF receivers have not been fully characterized. To fill these gaps, we introduce the RAQR to the wireless community by presenting an end-to-end reception scheme. We then develop a corresponding equivalent baseband signal model relying on a realistic reception flow. Our scheme and model provide explicit design guidance to RAQR-aided wireless systems. We next study the performance of RAQR-aided wireless systems based on our model, and compare them to classical RF receivers. The results show that Doppler broadening-free RAQRs are capable of achieving a substantial received signal-to-noise ratio (SNR) gain of over $27$ decibel (dB) and $40$ dB in the photon shot limit and standard quantum limit regimes, respectively.

• The paper introduces a detailed RAQR signal model incorporating four-level quantum schemes to optimize receiver parameters.
• It demonstrates a superheterodyne configuration achieving over 40 dB SNR gain in the standard quantum limit regime.
• The study highlights RAQRs' broadband tunability and compactness, underscoring their potential to enhance wireless system performance.

Rydberg Atomic Quantum Receivers for Wireless Communications and Sensing

Introduction

The development of high-sensitivity receivers is critical for meeting the requirements of next-generation wireless systems, characterized by aspirations for high data rates, extensive connectivity, and ultra-reliable low latency. Traditional RF technologies, reliant on integrated circuits and antenna advancements, confront limitations in sensitivity due to extrinsic noise and bandwidth constraints. The advent of quantum technologies, particularly quantum sensing, introduces revolutionary solutions. Rydberg atomic quantum receivers (RAQRs) exhibit exceptional sensitivity and offer a promising alternative for outperforming classical RF receivers in wireless communication and sensing applications.

RAQRs: Characteristics and Advantages

RAQRs leverage the unique properties of Rydberg atoms, where electrons are excited to a high energy state, resulting in enhanced sensitivity to external RF signals. They offer benefits such as broadband tunability, compactness, and SI-traceability. RAQRs demonstrate sensitivity in the order of microvolts per centimeter per square root of Hertz and can be enhanced to nanovolts using advanced configurations like superheterodyne structures. Additionally, RAQRs can operate across a wide range from near DC to THz frequencies using a single vapor cell, a feat constrained by the frequency-dependent component sizes in traditional RF systems.

Signal Model and System Design

This paper introduces an end-to-end reception scheme and signal model for RAQR-aided wireless systems, particularly focusing on a superheterodyne structure. The novel RAQR signal model presented includes a more realistic depiction of quantum electron transitions, incorporating four-level quantum schemes in conjunction with RF signal coupling. The model provides insight into optimizing RAQR parameters such as laser detuning frequencies and LO signal strength, demonstrating substantial received SNR gains.

Performance Analysis

The study compares the performance of RAQRs to classical RF receivers, establishing that doppler broadening-free RAQRs achieve an SNR gain surpassing 40 dB in the standard quantum limit (SQL) regime. Despite additional complexities in system integration, RAQRs offer unparalleled sensitivity, paving the way for potentially transformative applications in wireless communications and sensing. This advantage is especially pronounced in obtaining precise field measurements and capitalizing on untapped spectral resources.

Implications and Future Directions

The implications of RAQR technology are wide-ranging, offering improvements in measurement precision and viability across various frequencies with minimal calibration efforts. Practically, RAQRs can enhance communication systems, particularly where low strength and broadband signal detection are paramount. Future research should explore enhancements in RAQR architectures that address existing challenges in size, power consumption, and system complexity. The integration of RAQRs into comprehensive wireless networks also warrants further exploration, potentially redefining paradigms in high-frequency and sensitive sensing scenarios.

Conclusion

This paper delivers a robust exploration into the potential of Rydberg atomic quantum receivers, furnishing a detailed, theoretically grounded model that supports practical system design and performance optimization. The insights provided offer a promising direction for future wireless systems, where RAQR technology could play a pivotal role in achieving unparalleled sensitivity and operational efficacy in demanding environments. As we progress, the synthesis of quantum receivers and conventional systems might redefine the current technological landscape, inviting further experimentation and innovation in quantum-aided communications and sensing.