quantum sensing for GPS free navigation

Transforming Navigation Technology: From Smartphones to Quantum Compass

Introduction to Motion Sensors and Their Evolution

Disassemble a smartphone, fitness tracker, or VR headset, and you'll discover a compact motion sensor meticulously monitoring position and movement. Larger, more precise iterations of this technology, approximately the size of a grapefruit and significantly more accurate, aid in the navigation of ships, aircraft, and other vehicles, often with GPS support.

Advancements in Motion Sensor Technology

Scientists are now working to develop a motion sensor with such precision that it could significantly reduce the nation's dependence on GPS satellites. Previously, a sensor with this level of sensitivity---thousands of times more accurate than current navigation-grade devices--would have been as large as a moving truck. However, recent advancements are enabling this technology to become more compact and cost-effective.

Breakthroughs at Sandia National Laboratories

Researchers at Sandia National Laboratories have successfully utilized silicon photonic microchip components to execute atom interferometry--a quantum sensing method known for its ultra-precise acceleration measurements. This breakthrough marks a significant step toward creating a quantum compass for navigation in the absence of GPS signals.

The research team published their groundbreaking results, featuring a newly developed high-performance silicon photonic modulator--a microchip-based light control device---on the cover of Science Advances.

This research was funded by Sandia's Laboratory Directed Research and Development program and was conducted in part at the National Security Photonics Center, where collaborative efforts focus on integrated photonics solutions for national security challenges.

GPS-free Navigation as a Cornerstone of National Security

"Without GPS signals, maintaining precise navigation in real-world situations becomes increasingly difficult," observed Sandia scientist Jongmin Lee.

Within a war zone, such challenges heighten national security risks, with electronic warfare units capable of jamming or falsifying satellite signals to hinder military maneuvers.

"Leveraging quantum mechanics, these state-of-the-art sensors achieve unmatched precision in acceleration and angular velocity measurements, facilitating accurate navigation in GPS-denied environments," Lee stated.

The Modulator is the Central Feature of the Chip-Scale Laser System, Driving its Functionality

Conventional atom interferometers typically require a space the size of a small room. Constructing a complete quantum compass, or quantum inertial measurement unit, necessitates the deployment of six atom interferometers.

Lee and his team have successfully minimized the size, weight, and power consumption of the system. They have substituted a larger, energy-intensive vacuum pump with a compact vacuum chamber the size of an avocado and integrated multiple components, typically spread across an optional table, into a unified, rigid assembly.

Enhancing Modulator Performance and Cost

At the core of this microchip laser system is the new modulator, engineered to endure substantial vibrations. This advanced modulator replaces conventional laser systems, which are generally the size of a refrigerator.

In an atom interferometer, lasers fulfill multiple roles. The Sandia team utilizes four modulators to adjest the frequency of a single laser for various functions.

However, modulators commonly produce extraneous echoes referred to as sidebands, which require mitigation.

Sandia's suppressed-carrier, single-sideband modulator achieves and exceptional reduction of sidebands by 47.8 decibels--a unit commonly used for sound intensity but also relevant for light intensity--leading to a nearly 100,000-fold decrease.

Sandia scientist Ashok Kodigala stated, "Our performance enhancements represent a significant advancement over existing technologies."

Mass Production of the Silicon Device is Feasible, and it has become significantly more affordable

In addition to their size, the cost of quantum navigation devices has been a significant barrier. Each atom interferometer requires a laser system, which in turn depends on modulators.

A single full-size single-sideband modulator available on the market costs over $10,000, according to Lee.

Transforming large, costly components into compact silicon photonic chips significantly reduces associated expenses.

"We are capable of fabricating hundreds of modulators on an 8-inch wafer and an even greater number on a 12-inch wafer," noted Kodigala.

"Leveraging the same manufacturing processes used for computer chips, this advanced four-channel component, with bespoke features, can be produced at a fraction of the cost of current commercial options, making quantum ineratial measurement units more affordable," Lee stated.

As the technology advances toward field application, the team is examining additional potential uses beyond navigation. Researchers are evaluating its capability to detect underground cavities and resources by measuring minute variations in Earth's gravitational field. Furthermore, the newly developed optional components, including the modulator, are being explored for applications in LIDAR, quantum computing, and optical communications.

Kodigala conveyed excitement about the progress, remarking, "This is an exhilarating development. We are making substantial progress in the miniaturization of various applications."

An interdisciplinary team is transforming the quantum compass idea into a tangible reality

Lee and Kodigala exemplify the dual expertise within their multidisciplinary team: Lee's proficiency in quantum mechanics and atomic physics balances Kodigala's knowledge of silicon photonics, where optical rather than electrical circuits are employed.

At Sandia's Microsystems Engineering, Science, and Applications complex, these teams work together to desing, develop, and test chips tailored for national security applications.

According to Peter Schwindt, a quantum sensing scientist at Sandia, "Our proximity to colleagues enables us to collaboratively tackle critical challenges and facilitate the technology's transition to practical use."

The team's ambitious goal of transforming atom interferometers into a compact quantum compass aims to connect fundamental academic research with practical commercial applications. Atom interferometers, already a validated technology, hold promise for GPS-denied navigation. Sandia's initiatives focus on enhancing its stability, field readiness, and commercial potential.

The National Security Photonics Center engages in collaborative efforts with industry partners, small enterprises, academic institutions, and government agencies ot advance technological innovation and facilitate product launches. Sandia supports its mission with an extensive portfolio of issued patents and numerous additional patents currently in prosecution.

Schwindt highlighted his fervor for seeing these technologies transition into tangible applications, demonstrating his dedication to their practical implementation.

Michael Gehl, a Sandia scientist specializing in silicon photonics, expressed enthusiasm about the practical application of their photonics chips. "It's rewarding to witness our technology being utilized in real-world scenarios," he remarked.

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