On the 11th, the reporter learned from the University of Science and Technology of China that Professor Peng Xinhua, Associate Professor Jiang Min and other researchers in the Key Laboratory of Micro Magnetic Resonance of the Chinese Academy of Sciences of the University successfully carried out the direct search experiment of axion dark matter in the "axion window" by using quantum precision measurement technology, raising the detection limit in this field internationally by at least 50 times. The research results were recently published in the international academic journal Physical Review Letters. The particles and interactions described by the Standard Model of Particle Physics account for only 5% of the observed energy density in the universe. The unified theory, string theory, and hyperdimensional theory, among many other theories that go beyond the standard model, predict the hot candidate particles for dark matter such as axions. Quantum precision measurement technology utilizes properties such as coherence, correlation, and entanglement to achieve ultra sensitive measurements of weak energy levels, providing a transformative tool for searching for dark matter. However, due to the extremely weak signal of axion dark matter, which is easily masked by environmental noise and interference signals from classical magnetic fields, only a few research teams have conducted experimental searches in this mass range. A team of researchers from the University of Science and Technology of China cleverly utilized two polarized atomic ensembles located 60 millimeters apart to detect spin related interactions induced by dark matter in the axion window. Researchers used an atomic ensemble as a spin sensor and another atomic ensemble as a spin source in an experimental setup. In order to improve the polarization or detection sensitivity of nuclear spin in the atomic ensemble, they mixed alkali metals into the atomic ensemble and successfully amplified the polarization vector signal of the atomic ensemble by up to 145 times, constructing an ultra sensitive axion dark matter detector. However, due to the extremely weak dark matter signal of axion, classical magnetic field interference may become a huge challenge for high-sensitivity identification of axion signals. To overcome this challenge, researchers carefully designed a magnetic shielding system that successfully suppressed classical magnetic field signals by 1010 times. In addition, they also adopted the optimal filtering technique widely used in gravitational wave detection to maximize the signal-to-noise ratio of the axion dark matter signal. Although researchers have not yet found direct evidence of the existence of axion dark matter, they have still provided the strongest neutron neutron coupling boundary to date within the axion window, setting a new international best record. Researchers say that this achievement not only demonstrates the enormous potential of quantum precision measurement technology in the field of dark matter detection, but also lays a solid foundation for future related research. (New Society)