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Paul Lipman is Chief Strategy Officer at Infleqtion , leading growth and productization efforts at the cutting edge of quantum technology. getty I remember as a child building my first crystal radio and being astounded that I could listen to a radio signal using nothing but the power of radiofrequency energy permeating the airwaves in my bedroom. Just an antenna, diode, capacitor, coil and earpiece were all it took.
A little later, I saved up to buy a shortwave radio and accidentally stumbled across a numbers station broadcast. This was in the early ‘80s when these broadcasts were an integral part of Cold War espionage. The realization that the world around me was suffused with radio signals—and that some of these were mysterious and secret—helped spark my lifelong passion for science and engineering.
My colleague Dana Anderson, Infleqtion’s founder, is fond of saying that in the near future, if you’re not operating at the quantum limit, you won’t be competitive. Hearing the word “quantum” leads most people to think of quantum computing. However, this admonition is just as relevant in the world of radio communications.
In fact, the same quantum phenomenon—a highly excited atomic state known as a Rydberg atom —used to create entangling gates in neutral atom quantum computers is enabling a new generation of ultra-sensitive quantum radiofrequency (QRF) receivers that are poised to transform fields, including electronic warfare, signals intelligence and next-generation communications. A highly excited Rydberg atom, typically Rubidium or Cesium, is extremely sensitive to electromagnetic radiation. In a quantum computer, shielding ensures that these atoms aren’t affected by background signals.
However, this same quantum state sensitivity makes these atoms ideal for detecting extremely weak signals. A QRF receiver consists of a small cell (typically just a few cubic centimeters) containing the atomic vapor, a set of lasers for tuning the atoms to the wavelength of interest and back-end signal processing hardware to convert the optical output into an electronic signal. QRF receivers have tremendous advantages over conventional receiver systems.
Because they operate at the quantum limit, they can far exceed the sensitivity of classical receivers, which are constrained by thermal noise and the inherent noise of classical electronics. System sensitivity can also be further enhanced by deploying an array of receiver cells. Classical antennas scale in size with the wavelength of the signal of interest.
For example, ultra-low frequency (ULF) and very-low frequency (VLF) radio—used in fields including submarine and underground communications—require antennas that can span tens to hundreds of meters in size. Because QRF technology uses atoms as an antenna, its size is decoupled from wavelength, enabling extremely compact and low-profile receivers. This makes QRF ideal for use in environments where a large antenna is impractical or inadvisable.
Beyond being compact, the QRF receiver sensor head can be remotely operated, with fiber optics linking it to the rest of the system. Traditional battlefield electronic warfare vehicles are easily identifiable by their forest of antennas. Replacing these with a small array of QRF sensor heads would provide a significant advantage by reducing physical detectability.
Moreover, since the sensor head does not contain a metal antenna, detectability from side-channel leakage and radar reflectivity is minimized. Additionally, its optical signal readout enables precise signal detection without relying on classical electronics, making QRF systems highly resistant to jamming. Each QRF receiver cell can be tuned to a wavelength of interest in mere milliseconds.
One could imagine an array of receiver cells, each tuned to a different wavelength band, enabling simultaneous detection of signals across a broad swath of the electromagnetic spectrum. This presents a tremendous advantage over classical antennas, which require an unwieldy collection of static, often large, antennas to achieve broad-spectrum awareness. This inherent tunability also enables capabilities such as covert communications utilizing rapid frequency hopping.
These systems are transitioning fast from lab-based research projects to commercially deployed systems. Recent field demonstrations have validated this technology in harsh operating environments and have already drawn the attention of major defense contractors . QRF technology offers broad benefits for national security applications.
It is ideally suited to the detection of extremely weak or stealthy signals, making it invaluable for countering jamming and electronic countermeasures in electronic warfare. Its exquisite sensitivity also makes QRF ideal for covert communications, detecting low-power signals beyond the capability of classical receivers. Furthermore, extreme broadband tunability and simultaneous reception across a wide range of wavelengths make a new generation of covert communication systems a near-term reality.
Beyond national security applications, QRF technology holds immense potential for commercial use cases. It will enable the emergence of 6G wireless communications networks, which require ultra-sensitive, precisely tunable, low-power receivers. Similarly, QRF will have broad applications in noninvasive biomedical sensing, weather prediction based on atmospheric RF fluctuations, earthquake prediction through the detection of minute electromagnetic signals associated with tectonic activity, subsurface imaging for mineral and oil exploration, space communications and a new generation of radioastronomy instruments for deepening our understanding of the universe.
The world of technology has come a long way since I first cobbled together a crystal radio and marveled at the invisible waves surrounding me. But in many ways, we are still at the dawn of discovery. Radio waves have always been governed by quantum mechanics—it is only now that we have the tools to harness their full potential.
Quantum RF sensing isn’t just an evolution; it’s a revolution. It will redefine how we communicate, sense and understand the world around us. The airwaves are no longer just a medium for transmission; they are a vast, untapped frontier.
And at the quantum limit, the possibilities are limitless. Forbes Technology Council is an invitation-only community for world-class CIOs, CTOs and technology executives. Do I qualify?.
