Quantum Precision Measurement: Change "Invisible" to "Visible"

Recently, the world's first commercial low-temperature scanning nitrogen-vacancy probe microscope was released in Hefei, Anhui. The instrument is mainly used to detect the surface magnetism of nanomaterials and will provide a new tool for research in materials science, condensed matter physics, life science and other fields. The instrument is independently developed by Chinese enterprises, marking a new breakthrough in the industrialization of quantum precision measurement technology in China.

Quantum precision measurement refers to the use of quantum characteristics such as energy level transition, coherent superposition and entanglement to achieve a significant leap in measurement accuracy, sensitivity and resolution. For example, we can use a thermometer to measure the body temperature of a person, but we cannot use a thermometer to measure the body temperature of a mosquito, because the end of the thermometer is larger than that of a mosquito, and a large sensor is difficult to measure a small object. To measure objects much smaller than mosquitoes, such as single DNA molecules, drug protein molecules, etc., we need sensors smaller than molecules and cells.

In recent years, scientists have discovered a quantum sensor based on a "diamond defect". The sensing unit of this sensor is only the size of an atom, which can be said to be one of the smallest sensors that humans can develop. Diamonds seem to be flawless, but in fact there are many "defects", but it is these "defects" that make diamonds show certain characteristics that can be used. For example, when two adjacent carbon atoms in a diamond are replaced by a nitrogen atom and a vacancy, the structure formed shows a very good optical properties and quantum coherence. Scientists named it diamond nitrogen-vacancy (NV) color center.

NV color center is an excellent quantum sensor, which can be simply regarded as an extremely tiny magnetic needle. Through light detection magnetic resonance technology, researchers can not only observe the NV color center, but also use it to measure the surrounding magnetic field, and use light and microwave to read out the specific magnetic field size. After dozens of fine micro-nano processing steps such as nitrogen ion implantation and annealing, the researchers were able to manually prepare diamond NV color cores and produce them on a large scale into scanning NV probes that can be used for scanning imaging.

The commercial low-temperature scanning NV probe microscope developed by the researchers is a quantum precision measuring instrument that combines NV color center optical detection magnetic resonance technology and atomic force microscope scanning imaging technology. It can realize high-resolution, high-sensitivity, quantitative and non-destructive magnetic imaging in a wide temperature range, with high spatial resolution of nanoscale and ultra-high detection sensitivity of single spin.

In addition to diamond NV color center, there are many technical routes for quantum precision measurement, including atomic magnetometers, atomic clocks, etc. Atomic magnetometer is a technology that uses the interaction of light and atoms to detect magnetic fields, which can detect coronary heart disease and heart rate abnormalities. Optical lattice clock, as a new generation of atomic clock, can reach 10 billion years with an error of only 1 second. Each technical route, according to the application scenario to show their magic.

Quantum sensors are known as "a key to the micro-world". It is not only small, but also very sensitive. It can detect many undetectable and uncertain signals in the past, such as brain magnetic and cardiac magnetic signals, and can be used for early diagnosis of neurological diseases, coronary heart disease and other diseases. At the same time, quantum precision measurement also brings some innovations in detection methods, such as leakage current detection in lithium batteries in the field of new energy, power grid management in the field of energy exploration, and chip current imaging in the field of semiconductors/integrated circuits.

The industry regards quantum precision measurement as another "mature industrialization" direction in the field of quantum information technology, and technological innovation is becoming more and more active. In recent years, a number of start-ups in the field of quantum measurement have been hatched around the world to tap various application scenarios and promote the progress of quantum commercialization.

In layman's terms, quantum precision measurement is to change "invisible" to "visible". If we compare the world we know to an iceberg, what is above the water surface is what the current sensors can see, which is only the tip of the iceberg, and what can be observed by quantum precision measurement in the future. Quantum precision measurement will become a powerful tool for us to tap the "iceberg" of valuable information, and continue to expand the boundaries of human cognition. In the microscope, it foresees an unlimited future for global technological development.