The global positioning system (GPS), which provides location information through signals from satellites, is used for vehicle navigation, as well as aircraft and ship operations. Although it is widely used in the civilian sector now, it was only utilized by the military for operating fighter jets and missiles in the early 1990s. GPS is the global navigation satellite system (GNSS) provided by the United States. Currently, besides the United States (GPS), Russia (GLONASS), Europe (Galileo), and China (Beidou) are also establishing their own GNSS.
The heart of GPS is the clock. GPS calculates distance and location based on the time it takes for signals to arrive. The precision of time provision affects the degree of error. GPS satellites are equipped with atomic clocks that provide precise time. In the military, where missiles are guided and cyber warfare occurs in a race against time, time is crucial. Recently, China announced that it has developed an advanced atomic clock that could fundamentally change the landscape of future warfare. The United Kingdom also disclosed that its previously secret defense research institute has developed a military atomic clock utilizing quantum technology. The competition to secure accurate and precise time in the defense sector is spreading.
◇Outdoor atomic clock loaded onto military trucks
The Chinese Academy of Metrology and the Advanced Tracking Technology Innovation Center researchers unveiled on the 18th (local time) that they developed a small cesium atomic clock (NIM-TF3) the size of a short refrigerator at 1.5 meters.
Countries around the world possess precise atomic clocks to maintain a stable time standard. An atomic clock is a clock that utilizes the property of electrons in the atomic shell vibrating consistently. It measures time by counting the frequency of these vibrations. Cesium is mostly used in atomic clocks due to its stability. The globally recognized duration of one second is defined by cesium atomic clocks.
Atomic clocks are generally operated in specially designed research facilities that are isolated from environmental influences. Researchers explained that the newly developed clock is small enough to be mounted on a truck and robust enough to function normally even after long-distance transport. It maintains an accuracy of less than one quintillionth of a second even after traversing bumpy roads, a figure that is more than ten times higher than that of portable atomic clocks operated in the United States.
The new atomic clock developed by the Chinese Academy of Metrology operates similarly to a fountain. The clock shoots a laser to cool cesium atoms and then launches them vertically. As these atoms fall back down due to gravity, they emit light. Counting this flickering provides accurate time information.
◇China competing with the U.S. in precision clocks
Atomic clocks are not only extremely complex and expensive, but they also require thorough maintenance. They are very vulnerable to external factors such as vibration and magnetic fields. In addition to atomic clocks, laser and microwave clocks also provide precise time information. However, these technologies require a lot of energy or can malfunction even if they are handled slightly roughly. Researchers stated, “The new atomic clock requires minimal maintenance and supervision and can operate autonomously for extended periods,” adding that it is “ideal for military applications.”
The research team undertook various attempts, including redesigning the clock’s ion pump and shifting its location to the center. These efforts ultimately contributed to dramatically reducing the volume of the atomic clock. To improve the overall efficiency and stability of the system, the team revived a computer language that is now rarely used. They rewrote the program that operates the atomic clock in assembly language, which was used by developers in the 1980s and 1990s.
China is fiercely competing with the United States to secure precise time information. The most accurate atomic clock on Earth is still in the hands of the United States, but a team led by Chinese researchers has developed one. The Hong Kong South China Morning Post reported that as relations between the two countries deteriorate, some of these scientists are considering returning to China.
China is rapidly narrowing the technology gap by continuously introducing innovative atomic clocks like the NIM-TF3. There are analyses suggesting that the atomic clock used in the Beidou satellite, known as China's version of GPS, outperforms the atomic clocks in U.S. GPS satellites. The hydrogen atomic clock affixed to China's space station, Tiangong-2, broke the world record for maintaining time accuracy in space. Last year, China's longest and most accurate time synchronization optical fiber network also began operations.
In the scientific community, there are projections that China could catch up with the United States within a few years if this trend continues. This implies that the People's Liberation Army (PLA) could surpass the United States in electronic warfare, laser weapons, and unmanned technology.
◇Core of electronic warfare and cyber warfare
High-precision timekeeping systems, including atomic clocks, have emerged as the center of modern warfare. Accurate time information is essential for efficiently operating radars that detect stealth fighters thousands of kilometers away. Precision time information is also needed to utilize lasers or microwaves as powerful energy weapons to destroy enemies.
Encrypted secure communication systems rely on highly synchronized time. Precise time information is also essential for calculating trajectories and coordinating attacks to enhance the accuracy of advanced weapon systems like guided missiles. In operations like cyber warfare that race against the millisecond (ms), accurate timing is extremely important.
The United States is responding with its ‘nuclear clock’ that surpasses atomic clocks. The National Institute of Standards and Technology (NIST) and the University of Colorado Boulder are developing a ‘nuclear clock’ using the rare isotope thorium-229, which can maintain accuracy without a single second of error for billions of years. Unlike atomic clocks that depend on electronic transitions, the nuclear clock uses the transitions of atomic nuclei, which are less affected by external forces, based on frequency.
The research team announced in September that they discovered the first high-resolution spectrum of nuclear transitions and developed a nuclear clock device using thorium-229 crystals in collaboration with researchers in Vienna, Austria. They found a method to reduce radiation to one-thousandth using thin films of thorium tetrafluoride (ThF4) and significantly cut expenses as well. Scientists expect that within 2 to 3 years, nuclear clocks will surpass atomic clocks in accuracy.
The U.S. Department of Defense is also promoting projects to develop advanced atomic clocks applicable not only in defense but also in banks and the same key national infrastructure for power systems. The Defense Advanced Research Projects Agency (DARPA) under the U.S. Department of Defense is developing a chip-scale atomic clock (CSAC) that is the size of a small chip but has improved performance by 1,000 times.
◇Nuclear clocks and other quantum clocks are also under development
Efforts to secure precise time systems in defense are expanding. The UK Ministry of Defense surprisingly disclosed on the 2nd that it is developing a quantum clock to enhance the British armed forces' intelligence and reconnaissance operations. This clock, developed by the previously secret Defense Science and Technology Laboratory (DSTL) in the UK, is so precise that it can maintain an accuracy of one second over billions of years through experimental quantum technology. Initial experiments have already been completed incorporating the opinions of the British Royal Navy and Army.
The UK Ministry of Defense stated, “We expect that quantum clocks will reduce reliance on GPS, which can be disrupted by hostile forces and improve communications, while enhancing the accuracy of advanced weapons,” adding, “We intend to deploy them in military operations within the next five years.” DSTL assessed that “the quantum clock is an important achievement of the UK's quantum technology and will enhance operational capacities in navigation and guidance, promote industrial and scientific advancement, and create highly skilled jobs.”
The Australian Department of Defense and QuantX Labs, based in Adelaide, announced last year that they are developing a quantum clock with an accuracy of one part in 30 billion seconds. Quantum technology is one of the eight core technologies shared under the AUKUS (Australia-United Kingdom-United States) trilateral security pact. The Australian military has already acquired quantum optical clocks and is incorporating them into its communication and navigation systems. Additionally, they plan to further introduce atomic clocks within this year for testing in mobile environments. The Australian military aims to utilize quantum clocks to ensure normal operation of various weapons even in situations where GPS signals are subjected to jamming attacks.
References
Acta Metrologica Sinica (2024), http://jlxb.china-csm.org:81/Jwk_jlxb/EN/10.3969/j.issn.1000-1158.2024.12.19
Nature (2024), DOI: https://doi.org/10.1038/s41586-024-07839-6