Sandia National Laboratories scientist Jongmin Lee, left, prepares a rubidium cold-atom cell for an atom interferometry experiment while scientists Ashok Kodigala, right, and Michael Gehl initialize the controls for a packaged single-sideband modulator chip. (Photo by Craig Fritz)
Peel apart a smartphone, fitness tracker, or virtual reality headset, and you’ll find a tiny motion sensor tracking its position and movement. Similar larger, more expensive versions exist that are about as big as a grapefruit and a thousand times more accurate. These devices aid GPS-assisted navigation in ships, airplanes, and other vehicles.
Now imagine a sensor a thousand times more accurate than these navigation-grade devices, shrunk down to a microchip that can navigate without GPS. Researchers at Sandia National Laboratories say they have developed just that. They are terming it the “mother of all motion sensors,” a novel technology that could reshape navigation as we know it.
Quantum sensing could redefine precision navigation
This device could mark a milestone in the nascent field of quantum sensing. “For the first time, researchers from Sandia National Laboratories have used silicon photonic microchip components to perform a quantum sensing technique called atom interferometry, an ultra-precise way of measuring acceleration,” explains Jongmin Lee, a scientist at Sandia.
The heart of this technology lies in miniaturizing atom interferometry, a process that traditionally required equipment to fill a small room. Sandia’s team has managed to shrink this technology down to a microchip scale, relying on advanced silicon photonics. This miniaturization not only makes the technology more practical for real-world uses but also could pave the way for mass production and reduced costs.
It’s worth noting that a complete quantum compass — more precisely called a quantum inertial measurement unit — would require six atom interferometers. The Sandia team has made significant progress in reducing the size, weight, and power needs of these systems. For instance, they’ve replaced a large, power-hungry vacuum pump with an avocado-sized vacuum chamber and consolidated several components usually delicately arranged across an optical table into a single, rigid apparatus.
Sandia’s modulator achieves nearly 100,000-fold noise reduction
A central component of this system is Sandia’s newly developed suppressed-carrier, single-sideband modulator. Sandia notes that the device significantly enhances the system’s performance by reducing unwanted signal echoes, known as sidebands. “Our modulator reduces these sidebands by an unprecedented 47.8 decibels — a measure often used to describe sound intensity but also applicable to light intensity — resulting in a nearly 100,000-fold drop,” Lee said. This reduction in noise translates to a high level of precision in acceleration measurement.
Sandia National Laboratories’ four-channel, silicon photonic single-sideband modulator chip, measuring 8 millimeters on each side and marked with a green Sandia thunderbird logo, sits inside the packaging that incorporates optical fibers, wire bonds, and ceramic pins. (Photo by Craig Fritz)
Ashok Kodigala, a Sandia scientist, emphasizes the significance of this achievement: “We have drastically improved the performance compared to what’s out there.”
Sandia expects the combination of miniaturization and improved accuracy to open new doors for navigation and sensing applications, especially in environments where GPS signals are unreliable or unavailable. “By harnessing the principles of quantum mechanics, these advanced sensors provide unparalleled accuracy in measuring acceleration and angular velocity, enabling precise navigation even in GPS-denied areas,” Lee added.
Towards a quantum sensing future
Sandia used a collaborative approach in its quest to miniaturize quantum sensing technology. “We have colleagues that we can go down the hall and talk to about this and figure out how to solve these key problems for this technology to get it out into the field,” said Peter Schwindt, a quantum sensing scientist at Sandia. This close-knit research ecosystem, housed within Sandia’s Microsystems Engineering, Science, and Applications complex, helped align basic research and practical application.
“I have a passion around seeing these technologies move into real applications,” adds Schwindt.
While the primary focus of this technology has been on navigation, the potential applications extend far beyond GPS-free positioning. Researchers at Sandia are already exploring novel uses for their quantum sensing technology. “We’re investigating whether it could help locate underground cavities and resources by detecting the tiny changes these make to Earth’s gravitational force,” explains Lee. This capability could revolutionize fields such as geology, mining, and even archaeology. Moreover, the team sees broader potential for the optical components they’ve invented, including the high-performance modulator. “There are promising applications in LIDAR, quantum computing, and optical communications,” Lee adds.
The cost reduction aspect of this technology is significant. Lee points out, “Just one full-size single-sideband modulator, a commercially available one, is more than $10,000.” In contrast, the team’s approach could drastically reduce costs. Kodigala explains, “We can make hundreds of modulators on a single 8-inch wafer and even more on a 12-inch wafer.” This mass production capability could make quantum sensing technology much more accessible and affordable.
These diverse applications underscore the technology’s versatility, suggesting that the impact of this breakthrough could ripple across multiple industries and scientific disciplines. As research continues, it’s likely that even more unforeseen applications will emerge, further cementing the importance of this quantum sensing milestone.
Michael Gehl, a Sandia scientist who works with silicon photonics, sums up the team’s excitement: “It’s great to see our photonics chips being used for real-world applications.”
According to Lee, the technology could be used for “any system that relies on GPS for targeting or maneuvering could benefit from this technology. But it could also help find underground water sources, minerals, urban infrastructure in need of updating or natural cavities that could be used for carbon sequestration.”
“The precision and stability of a quantum inertial sensor would also make it suitable for mapping Earth’s gravity from space to study the movements of water, ice sheets and sea levels,” adds Ashok Kodigala.
