The first deep-sea experimental application of diamond quantum vector magnetometer

The ocean abundant with undiscovered resources is an important frontier for humanity’s exploration of the Earth. As the pressure on global supply and demands increases, deep-sea research and developments have attracted growing attention worldwide. Magnetometer is one of the most crucial tools for ocean exploration since the Age of Exploration. To this day, it still remains one of the most important tools in marine resources detection, oceanic geological investigation, and geophysical data acquisition. By monitoring the geomagnetic anomalies on the seafloor, magnetometers could effectively search for targets such as ferromagnetic mineral deposits, provide valuable geophysical data about tectonic activities, and serve as navigation references for vehicles in ocean. However, the current mainstream marine magnetometers primarily focus on scalar total field measurements. For all-directional measurements, they face technical challenges such as multiple-sensor setup stability and axis non-orthogonality, and still have much room for improvement in vector magnetometry under dynamic conditions. These bottlenecks have hindered the widespread application of magnetometry in deep-sea resource exploration and navigation.

In December 2022, a research collaboration led by the University of Science and Technology of China (USTC), in partnership with the Institute of Deep-Sea Science and Engineering of the Chinese Academy of Sciences (CAS) and Zhejiang University, successfully developed a novel deep-sea quantum vector magnetometer based on Nitrogen-Vacancy(NV) center in diamond, which is capable of all-directional vector measurements. The device was deployed aboard the Shenhai Yongshi manned submersible and tested in the Haima cold seep region of the South China Sea at a depth of 1400 meters. This milestone marks the first successful application of deep-sea magnetic field measurements using quantum precision sensing technology based on solid-state spins, advancing this system from laboratory-based research to real-world engineering applications. This work has been published in the journal National Science Review, titled “Experimental Demonstration of Diamond Quantum Vector Magnetometer for Deep-Sea Applications”. The study’s corresponding authors include Dr. Yijin Xie, Professor Xing Rong, and Professor Jiangfeng Du.

The fundamental sensing unit of the diamond vector magnetometer is the nitrogen-vacancy (NV) color center, a point defect in the diamond lattice. This structure is a solid-state spin system capable of quantum state coherent manipulation and readout at room temperature and under atmospheric conditions, enabling spin-state detection and physical measurements through optically detected magnetic resonance (ODMR). Unlike traditional all-directional vector magnetometers, the diamond quantum magnetometer utilizes the inherently stable diamond lattice structure as a reference for vector magnetic field measurements, effectively avoiding the synthetic errors introduced by mechanical variations in vector component units in existing magnetometers. Additionally, diamond's exceptional compatibility with extreme environments allows the magnetometer to operate across a wide range of temperatures and pressures, making it ideal for high-precision measurements in extreme deep-sea environments. To adapt the diamond sensor's spin manipulation and readout system to marine conditions using ODMR technology, the research team independently developed an FPGA-based electronic control and readout system, as well as an integrated optical system. Based on this, they successfully built the world's first prototype of a diamond quantum magnetometer capable of functioning in deep-sea environments. Furthermore, the team deployed this prototype aboard the Shenhai Yongshi manned deep-sea submersible for field trials in the South China Sea. These trials successfully demonstrated its capabilities in navigation magnetic compass applications, geomagnetic observation, and environmental magnetic field time-frequency monitoring. This achievement marks a significant breakthrough: transforming the diamond-based quantum system from laboratory experimentation to practical deep-sea engineering equipment.