Japan plans to develop compact quantum magnetic sensors for aerial drones that could help locate submarines at sea.
Tokyo included research into the technology in its fiscal 2027 defense budget request. Japan aims to complete development by fiscal 2031, according to the Nikkei newspaper.
The sensors would detect tiny magnetic changes linked to submerged vessels. Japan wants to mount them on low-cost drones operating near the ocean surface.
Quantum sensors target submarines
Quantum magnetic sensors use atomic properties to measure extremely small changes in magnetic fields. A submarine can disturb the surrounding magnetic field, potentially creating a detectable signature.
The technology could complement sonar and sonobuoys in Japan’s anti-submarine arsenal. Cheap drones could also cover areas for longer without putting aircrews at risk.
Defense specialist Masashi Murano told the South China Morning Post that magnetic sensors have limited detection ranges. That makes them less suitable for searching enormous areas of ocean.
Strategic chokepoints could make the technology more useful. Chinese submarines heading toward the Pacific must pass through several constrained waterways. Japan could deploy large numbers of drones around those routes and maintain persistent surveillance.
“Even if the detection range of each individual sensor is short,” Murano said, cheap unmanned systems could make coverage more efficient. That could reduce reliance on Japan’s P-1 maritime patrol aircraft. Crewed patrols remain valuable, but they carry significant operating and personnel costs.
China builds its own network
China is pursuing similar technology. Chinese researchers reported testing a drone-mounted quantum magnetic sensor system at sea last year.
Beijing has also expanded its wider anti-submarine capabilities. The effort includes the Y-9Q maritime patrol aircraft and Z-20F naval helicopter.
China has also developed a Wing Loong X drone variant capable of deploying sonobuoys. These devices can create temporary underwater listening networks.
The country is also developing broader ocean surveillance infrastructure. Satellites, buoys, underwater gliders and seabed listening arrays could work together across large maritime areas. Some analysts have dubbed parts of this network an “Underwater Great Wall.”
The surveillance race comes as China’s submarine fleet continues to expand. The Pentagon expects China could operate around 80 submarines by 2035 as its shipbuilding capacity grows.
US allies expand unmanned warfare
The United States and its allies are developing new unmanned systems for submarine warfare. General Atomics tested its MQ-9B SeaGuardian with a larger sonobuoy payload earlier this year. The U.S. Navy has also sought industry input on Silent Anvil, a compact air-launched torpedo.
The weapon could eventually allow more crewed and uncrewed aircraft to attack submarines. AUKUS partners Australia, Britain and the United States are developing payloads for autonomous underwater vehicles. Anti-submarine warfare remains a major focus.
Japan has also joined the three countries in testing underwater acoustic communications for maritime autonomous systems. Murano described the competition as two strategic pressures moving in parallel.
China has a growing sea-based nuclear force that needs protection. Its nuclear-powered attack submarines also need routes beyond the first island chain.
The United States and its allies face a different challenge. They rely heavily on undersea forces because submarines can operate inside China’s weapons engagement zone.
Japan’s drone project could add another layer to that contest. It aims to turn relatively inexpensive aircraft into persistent submarine-hunting platforms.