“When we don’t have GPS, we have to rely on our onboard inertial sensors that measure acceleration, rotation, and time to figure out where we were going, how fast we were going, and how fast we were turning to figure out where we are some time later,” Narducci said.
Though the devices are prohibitively expensive for widespread use in military vehicles, Narducci says they could start appearing on new large warships or submarines in the next several years. The U.S. Department of Energy’s Sandia National Laboratories already has a working quantum inertial sensor that it now needs to miniaturize.
Quantum sensors using similar technology could also detect objects hidden underground, by measuring miniscule changes in gravity from above Earth’s surface. “In Iraq, at some point, we were very concerned about weapons of mass destruction being buried,” Narducci said. “Quantum sensors can help us detect those things.”
The next most likely impact on national defense will be quantum communications. Already, countries are building prototype quantum communications networks impervious to hacking, thanks to a reliance on quantum properties for encryption, rather than the complex math problems used today.
China is the world leader in this field, having deployed integrated quantum networks and a second generation of quantum satellites. “The rest of the world is just building the first generation. In this sense, we are a little bit behind,” said Michal Krelina at Quantum Phi, a consulting firm focused on quantum applications for national defense.
While quantum technologies offer the promise of secure communication, they also pose the largest threat to cracking our current encryption protocols. Math problems used for encryption may take thousands of years for a classical computer to crack, but a quantum device should, in theory, be able to do it in a matter of days or quicker. Some security researchers have said it is likely the world’s largest intelligence services, including the U.S. Central Intelligence Agency, are already collecting reams of encrypted data in the hopes that quantum decryption technologies will one day become capable enough to decrypt it efficiently.
If we can build quantum computers capable of breaking encryption, it’s likely they’ll be useful for a whole host of other applications, too, from creating complex new military chemicals to chaotic battlefield simulations. But a clear-cut use is still uncertain because of the low computational firepower of today’s machines.
The time frame for when a powerful enough quantum computer becomes available is still heavily uncertain, Krelina said, and could take anywhere from a few years to decades, partly due to breakthroughs in classical computing making quantum advantages void, and partly because of the difficulty in correcting errors that are naturally part of quantum computing systems, a task that isn’t straightforward.
“We are still speaking about fundamental research,” Krelina said. “There is still risk, or probability, that there will be some surprise in a positive or negative sense. There could be some bottleneck in scaling up, or someone will come up with a super-effective error correction code that fixes most quantum errors.”
Despite these uncertainties, the world’s militaries recognize the potential scale of change and are pouring funds into quantum technologies. In 2023, the Department of Defense asked Congress for more than $700 million for research and development for work related to quantum information science, according to market intelligence firm GovWin. Comparative figures for China aren’t readily available, but the total government spend on quantum technologies for 2023 is around $15 billion.
Raw spending amounts don’t always tell the full story. Krelina said, “The U.S. has very strong private investments that are world-leading, which allow companies like IBM to be at the top.” Development programs like DARPA, which direct funding toward narrow and specific goals, can also accelerate technological breakthroughs faster than just throwing money at the problem.
Ultimately, the quantum revolution for national defense applications is unlikely to happen all at once. It will be a steady drumbeat of increasing capability, starting with onboard sensors, followed by large-scale communications networks impervious to hacking, and culminating in quantum computers that can perform calculations impossible for even the most powerful classical computers.
