But its delicate, table-sized array of components that includes a complex laser and vacuum system has largely kept the technology grounded and confined to the controlled settings of a lab.
Jongmin Lee, an atomic physicist at Sandia National Laboratories that envisions quantum inertial sensors as revolutionary, onboard navigational aids, wants to change all that. If the team can reengineer the sensor into a compact, rugged device, the technology could safely guide vehicles when GPS signals end up jammed or lost.
Incorporating Separated Components
The team showed how to integrate several normally separated components into a single monolithic structure. In doing so, they reduced the key components of a system that existed on a large optical table down to a sturdy package roughly 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,” Lee said.
A prototype, funded by Sandia’s Laboratory Directed Research and Development program, demonstrated movement toward advanced navigation tech out of the lab and into vehicles on the ground, underground, in the air and even in space.
As a jet does a barrel roll through the sky, current onboard navigation tech can measure the aircraft’s tilts and turns and accelerations to calculate its position without GPS, for a time. Small measurement errors gradually push a vehicle off course unless it periodically syncs with the satellites, Lee said.
Quantum sensing would operate in the same way, but the much better accuracy would mean onboard navigation wouldn’t need to cross-check its calculations as often, reducing reliance on satellite systems.
Sandia National Laboratories atomic physicist Jongmin Lee examines the sensor head of a cold-atom interferometer that could help vehicles stay on course when GPS is unavailable.
Source: Bret Latter, Sandia National Laboratories
“In principle, there are no manufacturing variations and calibrations,” compared to conventional sensors that can change over time and need recalibration, said Roger Ding, a postdoctoral researcher who worked on the project.
Extreme Materials
To prepare the atom interferometer for a dynamic environment, Aaron Ison, the lead engineer on the project, and his team used materials proven in extreme environments. Additionally, parts that are normally separate and freestanding integrated together and fixed in place or built with manual lockout mechanisms.
“A monolithic structure having as few bolted interfaces as possible was key to creating a more rugged atom interferometer structure,” Ison said.
The team also used industry-standard calculations called finite element analysis to predict any deformation of the system in conventional environments would fall within required allowances. Sandia did not conduct mechanical stress tests or field tests on the new design, so they need to do further research to measure the device’s strength.
“The overall small, compact design naturally leads toward a stiffer more robust structure,” Ison said.
Most modern atom interferometry experiments use a system of lasers mounted to a large optical table for stability reasons, Ding said. Sandia’s device is comparatively compact, but the team has already come up with further design improvements to make the quantum sensors much smaller using integrated photonic technologies.
“There are tens to hundreds of elements that can be placed on a chip smaller than a penny,” said Peter Schwindt, the principal investigator on the project and an expert in quantum sensing.
Photonic devices, such as a laser or optical fiber, use light to perform useful work and integrated devices include many different elements. Ongoing research is making photonics smaller and more versatile.
Size of Soda Can
With further improvements, Schwindt thinks the space an interferometer needs could be as little as a few liters. His dream is to make one the size of a soda can.
In a paper on the subject, the Sandia team outlines a future design in which most of their laser setup is replaced by a single photonic integrated circuit, about eight millimeters on each side. Integrating the optical components into a circuit would not only make an atom interferometer smaller, it would also make it more rugged by fixing the components in place.
While the team can’t do this yet, many of the photonic technologies they need are currently in development at Sandia.
“This is a viable path to highly miniaturized systems,” Ding said.