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Navigation when GPS gets dark

GPS karardığında navigasyonNature Communications (2022). DOI: 10.1038/s41467-022-31410-4″ width=”800″ height=”530″/>

Cross-sectional images of the LPAI sensor head. a, Horizontal section showing the cooling beam and atom detection channels with fixed optical components. The cooling channel light is transmitted to the sensor head through a polarization shielding (PM) fiber where a large aligned Gaussian beam (D1/e2~28mm) is used for cooling. The beam is cut to a diameter of ≈19 mm through the fused silica viewport on the compact LPAI sensor head. The light then passes through a polarizer and a λ/4 wave plate before illuminating the grid chip. GMOT atoms (dark red circle) form ≈ 3.5 mm from the grid surface. The atom detection channel is designed to measure atomic fluorescence through a multimode fiber coupled avalanche photodiode (APD) module. b, Vertical section of the sensor head showing designed beam paths for Doppler sensitive Raman. Cross linear polarized Raman beams are initiated from the same PM fiber and the two components are separated by a polarizing beam splitter (PBS). Fixed optics direct Raman beams in opposite directions to GMOT atoms (dark red circle). Credit: Nature Communication (2022). DOI: 10.1038/s41467-022-31410-4

Words like “hard” or “robust” are rarely associated with a quantum inertia sensor. The extraordinary scientific instrument could measure motion a thousand times more accurately than devices that help guide missiles, planes and drones today. But the delicate, table-sized array of components, including a complex laser and vacuum system, has kept the technology largely grounded and confined to the controlled settings of a lab.

Jongmin Lee wants to change that.

The atomic physicist is part of a team at Sandia that envisions quantum inertial sensors as revolutionary onboard navigational aids. If the team can turn the sensor into a compact, rugged device, the technology can safely guide vehicles where GPS signals are jammed or lost.

In an important milestone towards realizing their vision, the team has successfully built the cold atom interferometer, a key component of quantum sensors, designed to be much smaller and more robust than typical laboratory setups. The team describes their prototype in the academic journal Nature Communicationshows how to integrate several normally separated components into a single monolithic structure. In doing so, they reduced the essential components of a system housed on a large optical table into a sturdy package roughly the size of a shoebox.

“Very high precision has been demonstrated in the lab, but the practical issues for real-world application are that people need to reduce size, weight and strength, and then tackle a variety of issues in a dynamic environment,” Jongmin said. Said.

The document also describes a roadmap to further miniaturize the system using emerging technologies.

Funded by Sandia’s Laboratory Research and Development program, the prototype makes significant strides towards bringing advanced navigation technology out of the lab to vehicles on the ground, underground, in the air, and even in space.

. Credit: Nature Communications (2022). DOI: 10.1038/s41467-022-31410-4″>

GPS karardığında navigasyon. Credit: Nature Communications (2022). DOI: 10.1038/s41467-022-31410-4″/>

Compact light pulse atom interferometry (LPAI) concept for highly dynamic conditions. a 3D view of the compact LPAI sensor head with fixed optics and reliable optomechanical design. b Picture of steady-state GMOT atoms in the sensor head. Credits: Nature Communication (2022). DOI: 10.1038/s41467-022-31410-4

Ultra-precise measurements increase cruise power

As a jet rolls a barrel in the sky, current onboard navigation technology can measure the aircraft’s inclinations, turns and accelerations to calculate its position for a time without GPS. Jongmin said that minor measurement errors gradually lead a vehicle off course unless it is periodically synchronized with the satellites.

Quantum sensing will work just as well, but much better accuracy means onboard navigation will not need to check its calculations as often, reducing reliance on satellite systems.

“There are no manufacturing variations and calibrations in principle,” said Roger Ding, postdoctoral researcher who worked on the project, compared to conventional sensors that can change over time and need to be recalibrated.

Aaron Ison, chief engineer of the project, said he prepared the atomic interferometer for a dynamic environment and used materials proven in extreme environments with his team. In addition, parts that are normally separate and independent were integrated and fixed in place or made with manual locking mechanisms.

“A monolithic structure with as few bolted interfaces as possible was key to creating a more robust atom interferometer structure,” Aaron said. Said.

In addition, the team used industry-standard calculations called finite element analysis to predict that any deformation in the system in conventional environments would be within the required permits. Sandia has not performed mechanical stress tests or field tests on the new design, so more research is needed to measure the device’s strength.

“The overall small, compact design naturally leads to a stiffer and more robust construction,” said Aaron.

Navigation when GPS gets dark

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

Photonics lights the way to a more miniature system

Most modern atom interferometry experiments use a laser system mounted on a large optical table for stability reasons, Roger said. Sandia’s device is relatively compact, but the team has made further design improvements to make the quantum sensors much smaller using integrated photonic technologies.

“There are tens to hundreds of items that can be placed on a chip smaller than a dime,” said Peter Schwindt, the project’s principal investigator and quantum sensing expert.

Photonic devices such as laser or optical fiber use light to do useful work, and integrated devices contain many different elements. Photonics are widely used in telecommunications, and ongoing research is making them smaller and more versatile.

With further improvements, Peter thinks the space needed by an interferometer could be as little as a few liters. His dream is to make one the size of a soda can.

In their article, the Sandia team outlines a future design in which most of the laser setups are replaced with a single photonic integrated circuit, about eight millimeters on each side. Integrating optical components into a circuit not only makes the atom interferometer smaller, it also fixes the components in place, making it more robust.

While the team can’t do that yet, most of the photonic technologies they need are currently being developed at Sandia.

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

Meanwhile, Jongmin said that integrated photonic circuits will likely reduce costs and increase scalability for future production.

“Sandia has demonstrated an ambitious vision for the future of quantum sensing in navigation,” said Jongmin. Said.

This device can pioneer GPS-free navigation

More information:
Jongmin Lee et al., A compact cold atom interferometer with a high data rate grating magneto-optical trap and a photonic integrated circuit compatible laser system, Nature Communication (2022). DOI: 10.1038/s41467-022-31410-4

Provided by Sandia National Laboratories

Quotation: Navigation when GPS dark (2022, Oct 21) Retrieved Oct 22, 2022

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