Quantum weapons: the strange world of particles enters the war

Strange things happen in the world of atoms: particles can exist in two places at once, pass through solid barriers like walls, and even communicate across thousands of miles instantly. In the reality we see, these behaviors are impossible, confined to the realm of science fiction; but at the atomic level, dubbed the quantum world , they are an everyday reality that scientists have been exploring since the last century, trying to somehow reconcile with our "banal" materiality.

These almost "magical" but completely real properties of atoms will lead many to believe that, in the future, technology will be able to turn a solid object into a kind of "ghost" that passes through walls, or that the power of ubiquity can be obtained. And then, it's possible that imaginations will soar to the point of being able to glimpse the military applications of these tools: from invisible armies to weapons that cause unimaginable damage. That extreme remains science fiction: while scientists are still exploring their possibilities and applications, the field is more focused on creating quantum computers with unprecedented computing capacity, allowing everything from creating on-demand drugs to optimizing industrial processes in any factory down to the last millimeter.

Of course, military applications are also being explored, with countries like the US and China leading the way in investing in this promising new technology.

For example, in 2023, the US Department of Defense announced a $45 million project to integrate quantum components into weapons systems to increase targeting accuracy. In early 2024, the UK Ministry of Defense tested a quantum navigation system that cannot be jammed.

So, could quantum physics change wars as we know them?

"The main objective of quantum technologies is to manipulate or process information," Diego Porras Torre, president of the Specialized Group on Quantum Technologies and Information of the Royal Spanish Society of Physics (RSEF), explained to ABC. In other words, "teleportation" applies more to information than to matter. "This is the case in quantum computing, communications, and sensors, whose objective is to make high-precision measurements using quantum entanglement or coherence."

One of the most talked-about examples of the military application of this new technology is quantum radar. Although it's still a very early system—and even its actual viability is questionable—the idea is that this tool uses the quantum capacity of photons (the particles that make up light), allowing two of them to entangle and immediately communicate each other's state, changing their own, even when separated by great distances. It's a bit like the ability sometimes assumed of twins: they can sense what each other is experiencing even when they're apart.

There are prototypes in which one photon is taken from each entangled pair and fired into a microwave beam. The other photon is retained within the radar system. Of all the emitted photons, only the few that collide with a vehicle will be reflected, just as radio waves are reflected in radar. However, unlike radio waves, which already have ways to evade them, quantum radar would be impossible to escape, since if the fired photon is "disturbed" by a collision with an aircraft or submarine, the other entangled particle will instantly signal the change.

However, projects of this type, such as the one presented in 2018 by China's largest electronic defense company, China Electronics and Technology Corporation (CETC), or the device being worked on by Jonathan Baugh, a researcher at the University of Waterloo (Canada), which is intended to be used at Arctic stations managed by the North American Aerospace Defense Command (NORAD, a joint US-Canadian organization), are still in the testing phase, and little is known about them. "It's important to clarify that many of these applications, such as quantum radar, are highly speculative, and strictly speaking, it's not yet clear whether they can be used in practical applications," Porras points out.

"Unfortunately, there is a lot of biased noise and unreliable news in all areas of quantum technologies, much of it without scientific backing or verifiable publications. The field of radar is one such case," explains Juan José García Ripoll, a researcher in the Quantum Information and Foundations of Quantum Theory group at IFF-CSIC. "On the other hand, in the field of quantum communication, there is more than decent progress, although the technology is still not free of uncertainties." And here, it is true that several successful experiments have already been carried out, suggesting that quantum applications in the field of communication may be closer.

Quantum communication basically follows the same principle as quantum radar: two entangled particles containing information communicate instantaneously. However, if someone attempts to intercept that message, the system is so sensitive that the content is destroyed, making it impossible to eavesdrop and granting a level of security never seen before in traditional encryption systems. In this regard, the Asian giant takes center stage in increasingly sophisticated experiments. For example, in 2020, a team of researchers from the University of Science and Technology of China published an article in the journal Nature describing how, with the help of a satellite, they were able to send a quantum message between two ground stations separated by 1,120 kilometers. Earlier this year, China joined Russia in an article published in the journal Optics Express, which stated that they had managed to shatter this record, transmitting a message between two points separated by 3,800 kilometers.

China isn't the only one interested in this technology. Last December, an international team led by Jordan Thomas, a researcher at Northwestern University in the United States, published an experiment in the journal Optics that achieved, for the first time, quantum teleportation through 30 kilometers of high-power, but conventional, fiber optic cable. And in Europe, there is a quantum communications program, EuroQCI (European Quantum Communication Infrastructure), whose vision is to create European communications networks with security based on quantum cryptography, both in space and on the ground. "Currently, this initiative has been naturally absorbed by IRIS2 , due to its strategic nature, while the ground component (fiber) is being explored with more conventional instruments," notes García-Ripoll.

At the international level, quantum technologies are a focus of observation for organizations such as NATO because of their applications (such as much more precise navigation systems that do not require GPS; or the use of quantum gravimeters, which, in addition to being very useful for measuring the Earth's gravitational field with millimeter precision, can aid in the detection of tunnels or secret infrastructure). In fact, last November, a group of scientists published an open letter in Nature on the need to consider the ethical impacts of quantum technologies applied to defense. "Quantum technologies can help defend nations, but they also threaten human rights and values," noted M. Taddeo, A. Blanchard, and K.

Pundyk, the article's signatories. And they warn: "Its design and development need ethical guidance, before it's too late."

"There's a lot of hype surrounding quantum technologies because they need to attract a lot of investment," says David Trillo, a researcher and lecturer at CUNEF and a PhD in Physics. "But, in practice, it hasn't yet been proven that these technologies can be viable." Trillo explains that the problem with quantum tools is that many similar systems must work simultaneously and "continue to function quantum-wise, which is very complicated." "So far, experiments have been carried out with very few quantum systems. But what if there's a limit or an unknown physical law that limits our ability to use quantum technologies? That hasn't yet been ruled out."

Even so, Trillo believes that quantum technologies will not represent a drastic change in the way humanity understands war. "Nothing will explode, like a nuclear bomb; it will be more focused on better directing a missile, for example." García Ripoll shares the same opinion: "Generally speaking, quantum technologies are not tools for developing science fiction weapons, like the 'phasers' in 'Star Trek.' There is already sufficient destructive power in other 'conventional' weapons, such as the hydrogen bomb, which, although it was conceived thanks to an understanding of quantum fusion processes, is not the subject of our research."

Porras, for his part, agrees with both: "It's difficult to imagine that these technologies could have a directly offensive nature, although quantum technologies are in the development phase, and it's still difficult to predict what their ultimate impact on our lives will be." In general, quantum technologies are in the development phase, and it's still difficult to predict what their ultimate impact on our lives will be. The future of quantum mechanics is, at least for now, as mysterious as the world of particles itself.