Rydberg Technologies Shows Potential of Long-Range RF with Quantum Sensor at NetModX23

Rydberg Technologies, an Ann Arbor, Michigan-based quantum technology startup, demonstrated the use of an atomic receiver for long-range RF applications during the NetModX23 event hosted by the U.S. Army Combat Capabilities Development Command (DEVCOM) C5ISR Center in December.

The 2023 edition of NetModX featured 10 weeks of experimentation spanning 62 different technologies across 17 focus areas and five modernization priorities including “Future Vertical Lift, Long-Range Precision Fires, Network, Next Generation Combat Vehicle and Soldier Lethality,” according to the Army. A major goal sought by the C5ISR Center with NetModX is to take technologies that are nearing maturity from research labs directly into operational environments for assessments by active warfighters.

One such technology is the prototype Rydberg atomic receiver developed by Rydberg Technologies, which has been refining the performance, design and form-factor aspects of its device over the last decade. In a press release following the NetModX event, the company described it as a historic demonstration of the “world’s first long-range radio communications with an atomic quantum sensor.”

An image of an atomic RF sensor, the Rydberg field and measurement system. This was not the atomic receiver demonstrated during the NetModX event. No images of the receiver were available for this article. (Image: Rydberg Technologies)

According to Rydberg Technologies CEO David Anderson, the company “demonstrated the smallest ever atomic receiver at frequencies and long-range communication distances that show a clear path for transitioning Rydberg atom quantum technologies from laboratory to real-world applications.”

Anderson has also compiled several in-depth research papers about specific elements of quantum sensing, the advantages of Rydberg atom-based RF measurement and other related topics available on the company’s website.

Shortly after the completion of the NetModX event, Aerospace & Defense Technology caught up with Anderson to discuss the demonstration of their atomic receiver prototype and the future potential of quantum sensing in real-world military RF applications.

A&DT: Why was the demonstration of your atomic receiver at NetModX23 such a historic and significant milestone for the use of quantum sensing in military RF applications?

Dave Anderson: In quantum technologies and quantum sensing, the transition of laboratory research outcomes into practical solutions requires realizing physical devices and sensor hardware to validate technological capabilities and establish a path for deployment in real-world applications. In recent years, we have been focused on not only the advancing capabilities of our atomic receivers but also to substantially reducing the size, weight and power of atomic receiver hardware for deployment in real-world applications. As a reference point, in 2018 our atomic RF field measurement prototype, the first of its kind, was about the size of a refrigerator. Since then, we have been able to miniaturize our systems into a field-deployable device about the size of a briefcase.

At NetModX, we deployed this next generation atomic receiver device in an operationally relevant outdoor environment and demonstrated a host of capabilities afforded by this new type of atomic antenna.

In our own tests of the atomic receiver device, we have demonstrated a longrange RF signal communication over a kilometer range with an atomic sensor for the first time, as well as wideband frequency coverage from HF to SHF bands with a single compact atomic sensing element. It’s important to note however that we are still far from both practical and fundamental limits of atomic receivers, including fundamental quantum limits of sensitivity that we have not yet reached.

A&DT: How were you able to achieve that reduction in size to develop a field-deployable prototype atomic receiver?

Anderson: One major element was to leverage smart engineering of laser systems that are needed for an atomic receiver of this size. We also had to incorporate new hardware components and subsystems developed at Rydberg to get to the smaller design. It is important to note that the supply chain for quantum technologies generally is still evolving and growing.

Army DEVCOM C5ISR Center researchers work with radios during the Network Modernization Experimentation 23 at Joint Base McGuire-Dix-Lakehurst, New Jersey. (Image: U.S. Army)

We are continuously improving the design and engineering of our devices, and demonstrations such as these provide invaluable data that help guide those improvements. The detector heads that contain the sensing atoms, for example, may require alternative designs and adaptations to address application-specific use cases. Also, for deployment of these receivers in harsh operational environments with military RF systems in use today, further ruggedization will be needed.

Another image of Army DEVCOM C5ISR Center researchers performing demonstrations and experimentations with radios during the Network Modernization Experimentation 23 event. (Image: U.S. Army)
A&DT: What do you see as some of the main advantages of using a quantum sensor in comparison to traditional RF antennas and devices in use today?

Anderson: Traditional RF antennas and devices are generally based on driving electric currents in conductive structures to detect or generate RF electromagnetic waves. Rydberg atom sensors operate based on fundamentally different physics principles, in which the loosely bound electron of an atom serves as a highly sensitive sensor of RF electromagnetic waves that can be read out using light. Leveraging the properties of Rydberg atoms, these atomic quantum sensors provide several performance advantages compared to traditional RF sensor technologies. One advantage lies in the inherently small size of atoms.

An atomic receiver can be made significantly smaller than the size of traditional RF antenna receivers, whose size generally scales proportionally to the wavelength of the RF electromagnetic signal of interest. Atomic sensors break this proportionality requirement, enabling the prospect of compact detectors operational across large swaths of the radio spectrum from long-wavelength RF to millimeter-wave and even THz bands. On the long-wavelength portion of the spectrum, the function of large antennas often used for reception of very long wavelength RF signals, for example in long-distance communications systems, could be drastically reduced in size.

There are also major advantages in performance capabilities in terms of sensitivity and selectivity. When you start considering real-world operationally relevant scenarios, in which there can be significant electromagnetic interference and congested RF spectrum environments, atomic quantum sensing opens new possibilities for more resilient communications as well as significantly smaller form factors.

An Army DEVCOM C5ISR Center arranges a radio for a demonstration atop an Army ground vehicle during the Network Modernization Experimentation 23 event. (Image: U.S. Army)
A&DT: Are there any specific aerospace and defense applications that you have envisioned for the atomic receiver to enable in the future?

Anderson: I think the application possibilities are expansive, especially considering that the capabilities of the technology continue to advance. Several aerospace and defense application areas that atomic receivers could enable in the future include advanced resilient communication systems, low probability of detection/intercept (LPD/LPI) and anti-jamming applications, spectrum monitoring, and situational awareness in EW systems.

When you look at resilient communications specifically, the atomic sensor presents an entirely new modality distinct from traditional antenna technology. As we advance the capabilities of the technology, we also greatly benefit from working with partners in the aerospace and defense industry and actively seek feedback and expertise from the industry to guide development of the technology to address other specific application needs and future capabilities.

A&DT: Now that you have completed the NetModX demonstration, are there any design, form factor or performance improvements that you want to make to the atomic receiver moving forward?

Anderson: We are far from the fundamental limits of performance of atomic sensors, and we are still looking to push capability further. That includes everything from advancing performance in sensitivity, selectivity and other metrics, to exploiting the quantum nature of these atomic RF systems into new technology domains. On the hardware side, it’s driving further miniaturization and ruggedization and operation in harsh real-world environments and to address a broader set of applications with even smaller form factors.

In addition to deployment, hardware development in quantum and photonics also ties critically to enabling new capabilities with quantum sensors. Going forward, we’ll also continue to carry out more field demonstrations and development initiatives with early adopters, as getting user feedback remains critical in guiding a path to deployment.

This article was written by Woodrow Bellamy III, Senior Editor, SAE Media Group.