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Designing High-Tech Sensors to Steer Vehicles Without Satellites

A quantum inertial sensor can quantity motion a thousand times more precisely than the tools that help steer present-day aircraft, missiles, and drones.

Sandia National Laboratories atomic physicist Jongmin Lee examines the sensor head of a cold-atom interferometer that could help vehicles stay on course where GPS is unavailable. Image Credit: Bret Latter

However, its delicate, table-sized range of components, including a multifaceted laser and vacuum system, has mostly kept the technology grounded and limited to the regulated settings of a laboratory.

Jongmin Lee is keen to see that change.

The atomic physicist is part of a group of researchers at Sandia National Laboratories, who see quantum inertial sensors as revolutionary onboard navigational aids. If the group can redesign the sensor into a small, sturdy device, the technology could securely steer vehicles where GPS signals are lost or jammed.

In a key milestone toward accomplishing their vision, the researchers have successfully developed a cold-atom interferometer, a key component of quantum sensors, engineered to be smaller and tougher than standard lab configurations.

The researchers illustrate their prototype in the academic journal Nature Communications, demonstrating how to incorporate numerous typically separated constituents into one monolithic structure. In doing so, they shrunk the core components of a system that were present on a large optical table down to a robust package approximately the size of a shoebox.

Very high sensitivity has been demonstrated in the lab, but the practical matters are, for real-world application, that people need to shrink down the size, weight, and power, and then overcome various issues in a dynamic environment.

Jongmin Lee, Atomic Physicist, Sandia National Laboratories

The article also illustrates a roadmap for further miniaturizing the system using developing technologies.

The prototype, sponsored by Sandia’s Laboratory Directed Research and Development program, shows substantial strides toward shifting advanced navigation technology out of the laboratory and into vehicles in the air, on the ground, underground, and even in space.

Ultrasensitive Measurements Drive Navigational Power

As a jet performs a barrel roll in the sky, current onboard navigation technology can measure the aircraft’s tilts, accelerations, and turns to measure its location without GPS, for a time. Lee explained that small measurement mistakes slowly cause a vehicle to go off course unless it intermittently syncs with the satellites.

Quantum sensing would function in the same manner, but highly improved accuracy would mean that onboard navigation would not need to cross-verify its calculations as frequently, decreasing dependence on satellite systems.

Roger Ding, a postdoctoral scientist who participated in the project, said, “In principle, there are no manufacturing variations and calibrations,” compared to traditional sensors that can change over time and have to be remodified.

Aaron Ison, the project’s lead engineer, said to ready the atom interferometer for a dynamic setting, he and his team used materials tested in extreme environments.

Furthermore, components that are usually separate and self-supporting were incorporated together and installed in place or were constructed with manual lockout mechanisms.

A monolithic structure having as few bolted interfaces as possible was key to creating a more rugged atom interferometer structure.

Aaron Ison, Project Lead Engineer, Sandia National Laboratories

Moreover, the researchers used industry-standard calculations known as finite element analysis to estimate that any system deformation in traditional settings would fall within the mandatory allowances. Sandia has not performed mechanical stress tests or field tests on the new project, so additional research is required to compute the strength of the device.

“The overall small, compact design naturally leads toward a stiffer more robust structure,” Ison said.

Photonics Light the Way to a More Miniaturized System

Ding stated that most contemporary atom interferometry experiments use a system of lasers positioned on a large optical table to deliver stability. Sandia’s device is relatively small, but the team has already made additional design improvements to make the quantum sensors much smaller using unified photonic technologies.

There are tens to hundreds of elements that can be placed on a chip smaller than a penny.

Peter Schwindt, Project Principal Investigator and Quantum Sensing Expert, Sandia National Laboratories

Photonic devices, such as optical fiber or laser, employ light to carry out useful work and integrated devices include many varied elements. Photonics are used extensively in telecommunications, and current research is making them more versatile and smaller.

With additional enhancements, Schwindt believes the space an interferometer requires could be as little as a few liters. His vision is to create one the size of a soda can.

In their article, the Sandia researchers plan a future design wherein most of their laser installation is substituted by a single photonic integrated circuit, around 8 mm on each side. Incorporating the optical parts into a circuit would render an atom interferometer smaller and make it sturdier by fixing the parts in place.

While the researchers cannot achieve this yet, a number of the photonic technologies they need are presently in production at Sandia.

“This is a viable path to highly miniaturized systems,” Ding said.

In the meantime, Lee explained that integrated photonic circuits would probably lower costs and enhance scalability for future manufacturing.

Sandia has shown an ambitious vision for the future of quantum sensing in navigation.

Jongmin Lee, Atomic Physicist, Sandia National Laboratories

Journal Reference

Lee, J., et al. (2022) A compact cold-atom interferometer with a high data-rate grating magneto-optical trap and a photonic-integrated-circuit-compatible laser system. Nature Communications.


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