Quantum sensors are fascinating instruments that reveal nature to us in ways that were unthinkable just a few years ago. These are relatively small devices that help investigate items of scientific interest ranging from the infinitesimal specks of energy called photons to the unimaginably large web of galaxies that span the universe. Through the lens of these small quantum devices we can appreciate the breadth of nature and its secrets.
In this article, we delve into the understanding of Rydberg atoms, which enable an especially promising type of quantum sensor. Rydberg-based devices are being developed and commercialized by a company called Rydberg Technologies—and how Rydberg sensors could revolutionize telecommunications in the years to come.
Rydberg radio-frequency sensors use atoms that have a single electron in their outer orbits that has been energized artificially, causing the electron to occupy an orbit much farther away from the nucleus. That makes the atom very sensitive to changes in external electrical fields.
Scientists were aware of Rydberg atoms as far back as 1885. The atoms were named after Swedish physicist Johannes Rydberg, who did important early work that helped to describe these atoms. But initial research into their use in sensors started in the 1970s with the development of tunable dye lasers. Serious scientific research became possible once laser trapping and cooling allowed researchers to use lasers like tweezers to hold and manipulate atoms. This was a turning point in our understanding of Rydberg atoms. It was so important that the Nobel Prize for Physics was awarded in 1997 for this breakthrough.
Rubidium is an alkali metal atom that is a good candidate for Rydberg atoms because it has a single valence electron in the outer shell and 36 inner core electrons. This is important because the inner electrons act as a shield and weaken the attraction between the single outer electron and the atom’s nucleus.
To create the Rydberg atoms, energy is added to a rubidium atom using lasers. The additional energy moves the outermost electron into a higher orbit, where the attraction of the nucleus is weakened. This makes the atom increasingly susceptible to external magnetic and electrical fields.
Rydberg atoms have applications beyond quantum RF sensors. They can be used as qubits in quantum computing, in high-resolution imaging, and the detection of electromagnetic signals. Rydberg atoms have also been used in astrophysics research.
Rydberg Technologies recently announced the development of the world’s first long-range radio communications device using a Rydberg quantum sensor. The device was demonstrated at the U.S. Army Network Modernization Experiment 2023 event—a reliable test for next-gen communications and intelligence technology.
Rydberg atomic receivers have high sensitivity across a wide range of frequencies in the electromagnetic spectrum. They offer superior signal selectivity, low detection probability, and the ability to reject unwanted electromagnetic interference.
Rydberg Technologies has been able to shrink the sensors from refrigerator-sized devices in 2018 to today’s briefcase-sized sensors that can receive signals from more than a kilometer away. These devices have potential applications in defense, electronic warfare, surveillance, electromagnetic testing, and spectrum monitoring.
Rydberg Technologies is one of eight industry and university research teams chosen by DARPA for its Science of Atomic Vapors for New Technologies (SAVaNT) program. The company has demonstrated the capability of a Rydberg atomic sensor to receive electromagnetic waves over an unprecedented frequency range.
The deployment of Rydberg atom quantum sensors in the electromagnetic domain will create sweeping changes in wireless technology, revolutionizing telecommunications and providing capabilities superior to today’s technology.
