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Modern military and civilian communications environments are becoming increasingly crowded. Drones, radios, sensors, satellites, electronic warfare systems, and wireless networks all compete for space in the electromagnetic spectrum. Detecting and identifying individual signals within that environment is becoming more difficult, particularly when operators need to know not just that a signal exists, but where it is coming from.
Researchers have now demonstrated a quantum sensor capable of measuring the full three-dimensional direction of radio-frequency signals. The technology uses highly excited atoms known as Rydberg atoms to detect electromagnetic fields with a level of detail that conventional sensors typically cannot provide.
According to Interesting Engineering, traditional radio-frequency sensors generally measure signal strength along a single axis at a time. To determine direction, multiple antennas or sensor arrays are often required. The new quantum sensor takes a different approach. By analyzing how Rydberg atoms respond to incoming electromagnetic fields, the system can simultaneously determine field strength, polarization orientation, and the direction in which the signal is propagating.
At the center of the device is a small glass cell containing rubidium vapor. Lasers are used to place the rubidium atoms into Rydberg states, an extremely excited condition that makes them highly sensitive to electric fields. When a radio-frequency signal passes through the sensor, it alters the atomic behavior in measurable ways. Researchers can then extract information about the signal’s characteristics, including its three-dimensional direction.
Despite measuring only a few centimeters across, the sensor reportedly determines signal direction with an accuracy of roughly two degrees. Another notable advantage is frequency coverage. Conventional antennas are often optimized for specific frequency bands and may need to be physically comparable in size to the wavelength being detected. The Rydberg-atom approach is not constrained in the same way and can operate across an exceptionally broad range of frequencies, from direct current signals through terahertz frequencies.
From a defense perspective, the technology could support spectrum awareness, electronic warfare, signal intelligence, and secure communications. Modern battlefields often contain hundreds of simultaneous emitters, making rapid identification and localization of signals increasingly important.
The latest demonstration builds on previous work showing that Rydberg-based sensors can measure radio-frequency polarization and decode information carried within those signals. Together, these developments suggest that quantum sensing may become an increasingly important tool for understanding and managing complex electromagnetic environments.
The research was published here.
