The Pentagon is funding a military-grade laser based on quantum technology that is supposed to be reliable on the battlefield. Researchers at Washington University in St. Louis and Texas A&M University have been awarded a $1 million grant from the Defense Advanced Research Projects Agency (DARPA). This quantum laser aims to overcome the limitations of traditional lasers such as extreme temperatures, long distances, and atmospheric conditions like fog.

A New Era for Lasers

Lasers have revolutionized various aspects of our lives since their introduction in the early 1960s. Yes, they’re only that recent. They are vital to communication, medical procedures, and even grocery store checkouts.

For these everyday purposes, common lasers get the job done. However, ‘good enough’ is rarely acceptable by the military. Lasers are integral to many defense applications, like high-speed comms, targeting for precision munitions, surveillance and reconnaissance. The technology is even in directed energy weapons meant to destroy drones and missiles with concentrated beams of light. The problem is that they sometimes fail — and this can come at great cost.

This is why researchers led by Jung-Tsung Shen, an associate professor at Washington University and an expert in light-manipulation devices, are exploring the potential of quantum mechanics to enhance laser performance. The focus is on developing a quantum photonic-dimer laser, which relies on the principles of quantum entanglement.

Quantum entanglement is a strange phenomenon where two particles remain linked regardless of distance. Before the particles are measured, each will be in a state of superposition. When measured, these entangled particles will always be correlated, like two dancers in perfect sync. If one particle’s spin is up, the other’s will be down.

While traditional lasers produce photons (light particles) all in sync, entanglement allows for the creation of “photonic dimers” – pairs of photons linked in a special way. By “gluing” these photons together, researchers hope to create a more focused and powerful laser beam that can penetrate fog and travel longer distances.

“Photons encode information when they travel, but the travel through the atmosphere is very damaging to them,” Shen said. “When two photons are bound together, they still suffer the effects of the atmosphere, but they can protect each other so that some phase information can still be preserved.”

Quantum Mechanics to the Rescue

In experiments, Shen’s team found that when entangling two photons of different colors to form a photonic dimer, the particles took on the behavior of a blue photon. They now plan to devise a quantum photonic-dimer laser that can create different states at a rate of one million pairs per second.

“The unique thing about this project is its dual focus on generating these novel strongly correlated quantum photonic states and developing the theoretical framework and advanced algorithms for their efficient detection, potentially revolutionizing quantum imaging and communication,” Shen said.

Besides military lasers, quantum entanglement has found itself at the cutting edge of many exciting technologies. First and foremost, quantum entanglement looks like the ultimate ultra-secure communication channel of the future. With information encoded onto entangled photons, any attempt to eavesdrop on the signal would disrupt the entanglement, alerting the sender and receiver. Elsewhere, researchers have used similar entanglement techniques to devise a quantum radar that is 20% more capable than classical radar.