Chinese crystal ‘paves way’ for GPS-free thorium clock navigation

A research team from the Xinjiang Technical Institute of Physics and Chemistry in China has achieved a breakthrough in materials science, creating the world's first crystal capable of producing the specific ultraviolet light required for next-generation thorium nuclear clocks. Led by Pan Shilie, the team developed a fluorinated borate compound that pushes laser light to a record 145.2 nanometres (nm), as reported in *Advanced Materials*. This wavelength is crucial because it surpasses the previous benchmark of 150nm set by potassium beryllium fluoroborate crystals and finally meets the 148.3nm target needed to 'tick' the thorium-229 nucleus. The innovation paves the way for the practical development of portable, ultra-precise timekeeping devices.

Unlike atomic clocks that use electron vibrations, nuclear clocks measure time using vibrations inside an atomic nucleus, which is far less susceptible to environmental interference. This fundamental difference promises significantly higher precision, enabling reliable navigation in environments where GPS signals are unavailable or unreliable, such as deep underwater for submarines or in the vastness of space for probes. The team's work provides a new pathway for designing deep-ultraviolet materials, directly addressing a major technical hurdle in making these theoretical clocks a practical reality for future autonomous systems.