Researchers have leveraged silicon photonic microchip components to execute a quantum sensing method known as atom interferometry, which allows for incredibly accurate measurements of acceleration. This achievement marks a significant step toward creating a type of quantum compass for navigation purposes in scenarios where GPS signals are absent.
If you examine a smartphone, fitness tracker, or virtual reality device, you will discover a small motion sensor that is responsible for tracking its location and movement. Larger, pricier versions of this technology—around the size of a grapefruit and significantly more precise—aid in navigating ships, airplanes, and other vehicles with GPS support.
Currently, scientists are striving to enhance motion sensors to a level of precision that could lessen the country’s dependency on global positioning satellites. Until recently, such a device—being a thousand times more sensitive than the current navigation-grade sensors—would have occupied a moving truck. However, recent developments are drastically reducing both the size and cost of this technology.
For the first time, a team from Sandia National Laboratories has successfully utilized silicon photonic microchip components to implement atom interferometry, a highly precise acceleration measurement technique. This marks a new milestone in the quest to develop a quantum compass for navigation when GPS signals are lacking.
The findings were published as a prominent feature in the journal Science Advances, highlighting a newly developed high-performance silicon photonic modulator—a device that governs light on a microchip.
This research received backing from Sandia’s Laboratory Directed Research and Development program and was partly conducted at the National Security Photonics Center, which focuses on developing integrated photonic solutions for complex challenges within the national security domain.
Navigation without GPS is crucial for national security
“Accurate navigation can be problematic in real-world situations when GPS signals are not available,” explained Sandia scientist Jongmin Lee.
In combat zones, this challenge presents national security threats, as electronic warfare units can interfere with or deceive satellite signals to disrupt military movements and operations.
Quantum sensing provides a potential remedy.
“Using the principles of quantum mechanics, these state-of-the-art sensors achieve unmatched precision in measuring acceleration and angular velocity, facilitating exact navigation even in areas where GPS is unavailable,” Lee noted.
Modulator central to a chip-scale laser setup
Ordinarily, an atom interferometer takes up an entire small room. A fully functioning quantum compass—more accurately referred to as a quantum inertial measurement unit—requires six atom interferometers.
However, Lee and his team are working on ways to reduce its dimensions, weight, and energy consumption. They have already substituted a large, energy-intensive vacuum pump with a vacuum chamber the size of an avocado, condensing multiple components that would typically be spread across an optical table into a single, unified device.
The new modulator is at the heart of a laser system on a microchip, designed to withstand significant vibrations. It replaces conventional laser systems that typically occupy the space of a refrigerator.
Lasers serve multiple functions in an atom interferometer, and the Sandia team employs four modulators to adjust the frequency of one laser for various operations.
However, these modulators can produce unwanted echoes known as sidebands that need control.
Sandia’s suppressed-carrier, single-sideband modulator minimizes these sidebands by an unprecedented 47.8 decibels—utilized to quantify sound intensity but also applicable to light intensity—resulting in a nearly 100,000-fold reduction.
“We have significantly enhanced performance compared to existing options,” stated Sandia scientist Ashok Kodigala.
Silicon device is easily produced and cost-effective
In addition to size, expense has been a substantial barrier to deploying quantum navigation devices. Each atom interferometer requires a laser system, which in turn needs modulators.
“A single full-size single-sideband modulator available on the market costs more than $10,000,” Lee remarked.
By miniaturizing bulky, costly components into silicon photonic chips, these expenses can be reduced.
“We can fabricate hundreds of modulators on an 8-inch wafer and even more on a 12-inch one,” Kodigala explained.
Moreover, since the manufacturing process mirrors that of nearly all computer chips, “This advanced four-channel component, along with additional custom features, can be mass-produced at a significantly lower cost compared to current commercial products, allowing for the cost-efficient creation of quantum inertial measurement units,” Lee asserted.
As this technology approaches practical application, the team is exploring additional uses beyond navigation. Researchers are looking into whether it can assist in locating underground cavities and resources by detecting minor alterations to Earth’s gravitational field. They also envision potential applications for the optical components they developed, including the modulator, in LIDAR, quantum computing, and optical communications.
“It’s genuinely thrilling,” Kodigala expressed. “We are making substantial headway in miniaturization for various applications.”
A collaborative team making the quantum compass a reality
Lee and Kodigala represent two segments of a multidisciplinary team. One segment, including Lee, comprises experts in quantum mechanics and atomic physics. The other, like Kodigala, specializes in silicon photonics—essentially a microchip with light beams replacing electrical currents.
These teams collaborate at Sandia’s Microsystems Engineering, Science and Applications complex, where researchers design, produce, and evaluate chips tailored for national security initiatives.
“We have colleagues just down the hall to discuss this with, working together to solve crucial challenges for this technology to be deployed in the field,” stated Peter Schwindt, a quantum sensing scientist at Sandia.
The team’s ambitious objective—transforming atom interferometers into a compact quantum compass—serves to bridge the gap between foundational research at academic institutions and commercial development by tech firms. An atom interferometer is a validated technology that could serve as an effective instrument for GPS-independent navigation. Sandia’s continuous efforts aim to enhance its stability, field readiness, and commercial feasibility.
The National Security Photonics Center collaborates with industry players, small businesses, academic institutions, and government entities to develop innovative technologies and assist in bringing new products to market. Sandia holds hundreds of patents and numerous others in the pipeline supporting its mission.
“I’m passionate about seeing these technologies applied in real-world situations,” Schwindt shared.
Michael Gehl, a Sandia scientist specializing in silicon photonics, shares this enthusiasm. “It’s fulfilling to see our photonics chips used in practical applications,” he noted.
Sandia National Laboratories is a multi-mission laboratory managed by National Technology and Engineering Solutions of Sandia LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration. Sandia undertakes major research and development tasks in nuclear deterrence, global security, defense, energy innovations, and economic competitiveness, with principal locations in Albuquerque, New Mexico, and Livermore, California.
