The Department of Defense is looking to the extraordinary capabilities of quantum sensing technology to find alternatives to GPS, the space-based position navigation and timing (PNT) service that’s become the essential enabler of the American way of war.
In a shooting war with a peer adversary, “you really must presume a denied and degraded [communications] environment in which you cannot rely upon external PNT signals like GPS,” explained Lt. Col. Nicholas Estep from the Defense Innovation Unit (DIU) the DOD’s acquisition outpost in Silicon Valley that aims to help innovative commercial firms sell cutting-edge technology to the U.S. military.
But the Pentagon currently does rely on GPS, not just to target precision-guided munitions, but to let troops know where they and the enemy are—creating the common operational picture that’s essential for multidomain operations.
GPS is also essential for industries from banking to agriculture, and GPS jamming and spoofing associated with military conflicts has forced commercial aircraft to rely on inferior alternative navigation systems.
“What are we going to do in order to maintain PNT-enabled solutions, to allow the joint force to execute its mission?” asked Estep, director of DIU’s Emerging Technology portfolio, which covers quantum sensing, hypersonics, and advanced materials.
DIU is seeking answers to that question in an industry offering earlier this year for nontraditional defense suppliers, looking for quantum sensing technology that could be deployable to augment or back up GPS for military missions within a couple of years.
DIU received dozens of proposals, said Estep: “We did get a very strong signal of interest from the community, a mixture of traditional primes, startups, and non-traditional companies.”
They’re not alone in their interest. Resilient PNT, a capability that can operate in a GPS-denied environment, was one of two capabilities identified by Air Force Secretary Frank Kendall to use the ‘Quick Start’ funding provisions placed in the FY24 NDAA. And the Space Force is seeking to diversify GPS signals across multiple orbits to increase its resilience.
Quantum Sensing
Quantum mechanics is the science that deals with the extraordinary, if not downright spooky, properties of subatomic particles. Although the principles of quantum mechanics date back almost a century to Einstein’s work, recent advances in nano-engineering—the manipulation of matter at the atomic and subatomic level—have made it possible for the first time to actually demonstrate and exploit the extraordinary properties of quantum particles.
Celia Merzbacher is executive director of the Quantum Economic Development Consortium (QED-C), an industry-led stakeholder forum supported by the National Institute for Standards and Technology. She told Air & Space Forces Magazine that quantum sensing is one of the least understood but most mature of the three fields of quantum mechanics, the other two being quantum computing and quantum communications.
“Quantum sensing for PNT is, to some extent, already here,” she said, citing the wide commercial use of atomic clocks, which provide precise timing based on the movements of subatomic particles.
In a report in September, QED-C noted that “quantum sensors can provide navigational information in environments where GPS signals are unavailable or unreliable.”
The report and the DIU industry offering outline three ways quantum sensing can provide PNT: measuring movement, gravity, and Earth’s magnetic field.
Each offers a way for a plane, ship, or vehicle to accurately ascertain its position, just as GPS does.
Merzbacher predicted that a commercial market for quantum sensing alternatives to GPS would emerge within five years. However, for that to happen, DOD will need to step up its investments, “because these companies that are developing quantum sensors for PNT and other uses are smaller companies, and they have somewhat limited resources to invest in anything that’s beyond two or three years to market.”
As an early adopter with rigorous standards, “government can really accelerate progress by stepping in and helping to defray the cost of the engineering and R&D at this stage. Eventually the flywheel will be spinning, and as revenues are being generated, those companies can reinvest. But if the government doesn’t step in and invest … then progress will just be much slower,” she said.
The QED-C report identified the transition from lab to battlefield as a key hurdle. “A big challenge is integrating these new components that are really just being developed in the lab, in a controlled environment, integrating and packaging those into something that can go onto a plane or a space platform,” and withstand the rigors of vibration or radiation, she said.
“There’s going to be a lot of work needing to be done,” she said.
All the while, the U.S. risks falling behind adversaries like China, said Dana Goward, a career U.S. Coast Guard officer who is now president of the Resilient Navigation and Timing Foundation, a 501(c)3 scientific and educational charity.
China (and U.S. allies South Korea and Saudi Arabia) already had a functioning terrestrial alternative to GPS in an Enhanced Long-Range Navigation (eLORAN) system. eLoran relies on hyperbolic navigation, where a plane, ship or vehicle can ascertain its location by correlating signals from two or more terrestrial broadcast towers.
“It’s much more accurate, much more difficult to disrupt,” than GPS or other satellite-based PNT, said Goward.
Goward called quantum sensing “exciting,” but worries that given the regulatory requirements for commercial aircraft, it could be “many years” before the technology was available for broad adoption. “How close are we to something that is viable in any commercial application?” he asked.
GPS is now taken for granted by consumers and businesses, but there is little understanding of its fragility, Goward said. Meanwhile, technologies demonstrated in a laboratory require materials maintained at absolute zero or extremely specific laser frequencies that aren’t ready for prime time, he said. “They’ll keep making it better and better, and perhaps someday it’ll get down to the common folk like you and me.”
Quantum Orienteering
The supporters of quantum sensing for PNT say it represents a step change, away from the inherently fragile beacon-based approach of GPS and other satellite-based PNT systems.
“The next generation of PNT technologies returns positioning to the local vehicle or individual and it says, essentially, now we want to be able to navigate using only things that we measure locally,” said Michael Biercuk, CEO of Q-CTRL, a quantum technology company.
Because the Earth’s magnetic and gravitational fields vary minutely from place to place and because those variations have already been mapped, a tool that can measure those minute variations can accurately locate the user, Biercuk explained.
“If you combine a really good map of these geophysical phenomena with a really good local sensor, you can do what we sometimes jokingly refer to as quantum orienteering,” Biercuk said, “You can take your map and your sensor and figure it out where you are.”
The extreme technical requirements of quantum sensing equipment can be mitigated by the use of software algorithms, he said.
“The laboratory performance is extraordinary, but the performance outside the lab is tremendously degraded. Anytime you put it on a moving vessel, it’s really hard to keep it operational. They’re very, very sensitive devices,” he said.
Q-CTRL had been “able to show that when you combine, obviously very good hardware engineering with software enablement, you can actually make these tools viable in real environments,” he said.