A navigation system that does not rely on global positioning satellites (GPS) is drawing closer as scientists at Sandia National Laboratories took significant steps toward a compact and more accurate compass powered by quantum mechanics.
The researchers made history after successfully performing a quantum sensing technique called atom interferometry using silicon photonic (SiPh) microchip components for the first time. This technique provides ultra-precise acceleration measurements and can be applied to enable navigation in GPS-denied areas.
Additionally, the team debuted a new high-performance SiPh modulator, a device that essentially controls a light beam on a microchip.
The research, supported by Sandia’s Laboratory Directed Research and Development program, was performed, in part, at the National Security Photonics Center. The findings of the research and the modulator are currently published in Science Advances.
Smaller, cheaper, and less noisy
One major challenge in building a quantum compass is size. A complete quantum inertial measurement unit (quantum compass) requires six atom interferometers, but a typical atom interferometer fills a small room.
Fortunately, Sandia researchers have come up with innovative ways to reduce that. They already have developed a vacuum chamber, with a size similar to an avocado, to replace the large-power-hungry vacuum pump in an atom interferometer. Several other components have also been consolidated into a single, rigid apparatus.
In addition to that, the new SiPh modulator would serve as the main component of a laser system on a microchip. In an atom interferometer, four modulators will be used to shift the frequency of a single laser to perform different functions. They would replace a conventional laser system that could reach the size of a refrigerator.
Addressing the large size of the technology is only one of the hurdles that the researchers needed to overcome. Sandia scientist Jongmin Lee stated that one commercially available modulator can cost over $10,000.
Lee and his team managed to cut that cost by miniaturizing bulky and expensive components into silicon photonic chips. Fellow scientist Ashok Kodigala said, “We can make hundreds of modulators on a single 8-inch wafer and even more on a 12-inch wafer.”
This allows for the mass production of atom interferometers at a much lower cost than current commercial alternatives, paving the way for cheaper production of quantum compass in the future.
Still, there is one more problem—modulators produce undesirable echoes known as sidebands.
However, Sandia researchers claimed that their suppressed-carrier, single-sideband modulator reduced these sidebands by 47.8 decibels, which is equivalent to around a 100,000-fold drop.
Navigation and beyond
This achievement in quantum sensing technology offers promising applications in real-world navigation, particularly in scenarios and areas where GPS signals are unavailable.
For instance, the lack of accurate navigation in war zones threatens national security since electronic warfare units can spoof or jam satellite signals to sabotage troop operations and movements.
“By harnessing the principles of quantum mechanics, these advanced sensors provide unparalleled accuracy in measuring acceleration and angular velocity, enabling precise navigation even in GPS-denied areas,” Lee noted.
Besides navigation, the researchers are also eyeing other potential uses. They are currently studying whether or not the technology could assist in locating underground cavities and resources. Moreover, they are confident that their modulator and other optical components could find application in quantum computing, optical communications, and light detection and ranging.
