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Everything from drones to airplanes, ships, and cars are equipped with GPS units to help them navigate around the world. This information is crucial not only for powering autonomous navigation systems, but also for supplying human operators with the information they need to get where they are going. But while this technology has become essential in the modern world, our reliance on it is somewhat concerning. In some locations GPS signals are blocked by obstructions, so the systems that rely on them are useless. Worse yet, GPS signals can be intentionally spoofed or jammed, which could lead to widespread chaos and tragedy. These problems could be averted by using self-contained motion sensors rather than signals from a constellation of satellites. But that would require motion sensors thousands of times more accurate than the types that we have in our smartphones and other consumer electronics. The technology does exist today, but in order to be accurate enough to replace GPS, a quantum inertial measurement unit is the only option available. These systems require six atom interferometers, with each being large enough to fill a small room. That is not exactly practical for the vast majority of applications, and as you might expect, these systems are also extremely expensive. Researchers at Sandia National Laboratories have been working on a much more compact atom interferometer, however, which could make precise, GPS-free navigation a practical reality in the near future. The new system is based on Photonic Integrated Circuits (PICs), which make it significantly more compact than the traditional laser systems used in atom interferometers. The new technology is also more resistant to vibrations and shocks, making it ideal for use in challenging environments. PICs are small, durable chips that can perform the same functions as larger, more complex laser systems. These chips integrate various components — like modulators and amplifiers — onto a single platform, making the entire system smaller, more robust, and easier to produce. One key innovation is the development of a silicon photonic modulator, which is crucial for controlling the light in these systems. This modulator allows the system to generate and manage multiple laser frequencies from a single source, eliminating the need for multiple lasers. These novel modulators were also noted to substantially reduce unwanted echoes called sidebands that plague existing technologies. The result is a compact, high-performance laser system that can be used in a variety of advanced applications, including quantum sensors like atomic clocks and gyroscopes. Overall, this represents a significant step forward in making these advanced sensing technologies more practical and deployable in real-world situations. The team also pointed out that the applications of their technology extend well beyond navigation. These sensors could, for example, be used to locate natural resources hidden beneath the ground by observing how they alter Earth’s gravitational force. Further potential applications exist in enhancing LIDAR sensors, quantum computing, and optical communications.