Reconstruction of nanometer resolution by quantum precision measurement technology

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  Microwave is an electromagnetic wave with a wavelength of about 1m to 1mm and a corresponding frequency of about 300MHz to 300GHZ. Since the German physicist Heinrich Hertz first generated microwave signals at the end of the 19th century, microwave has been rapidly applied to military defense and radar communication, and soon expanded to the fields of information technology, navigation, semiconductor devices and so on, It reflects a country's scientific and technological level and competitive strength.

  The trend of miniaturization and high integration puts forward more urgent needs for microwave measurement technology in higher spatial resolution, sensitivity and vector field reconstruction. For example, the highly integrated chip basic unit transistor has already entered the size of tens of nanometers, and its characteristic microwave field size is on the nanometer scale. Vector analysis is helpful to understand the transmission and reflection characteristics of microwave and to analyze and improve the performance of devices.

  however, in situ detection of these microwave devices on the nano scale is very challenging. At present, the measurement methods of cold atom and hot atom vapor only reach the spatial resolution of micron and millimeter, and are limited to low temperature or vacuum.

  Professor Du Jiangfeng's research team of China University of science and technology has made a breakthrough in the field of quantum precision measurement. Using the solid-state electron spin in diamond, it has realized the vector reconstruction measurement of microwave field magnetic field component with nano resolution in room temperature atmosphere for the first time in the world. The work was published in the international important academic journal Nature communication under the title of "high resolution vector microwave geometry based on solid states in diamond". This series of research has been supported by NSFC, Ministry of science and technology, Chinese Academy of Sciences, Ministry of education and other units.

  Du Jiangfeng's research team skillfully used the electron spin in the nitrogen vacancy defect in diamond (hereinafter referred to as "Diamond probe") as a quantum sensor to realize the reconstruction and measurement of near-field microwave magnetic field vector. Diamond probe is a kind of crystal defect containing nitrogen, which generally exists in diamond single crystal. There are two unpaired electrons in the defect to form a quantum system with spin 1.

  driven by microwave magnetic field, electron spin can oscillate between two quantum states, which is called Rabbi oscillation. The Rabi oscillation frequency is related to the intensity and vector direction of the microwave magnetic field. By measuring the Rabi oscillation frequency of electron spin and combined with the single crystal characteristics of diamond, the research team skillfully completed the measurement and vector reconstruction of 2.6000ghz linearly polarized microwave magnetic field, and the spatial resolution reached the optical diffraction limit (about 230nm), By processing the experimental data, the vector angle accuracy of 5.6 milliradian and the vector amplitude accuracy of 1 millionth Tesla are obtained. The spatial resolution has been higher than that of cold atom and hot atom vapor method, and the microwave magnetic field detection method has entered the nano scale.

  this experiment provides a new experimental means for high-precision microwave near-field measurement in room temperature atmosphere. With the progress of related technologies, the accuracy and spatial resolution of measurement results still have room for further improvement. Combined with scanning probe microscopy and strong magnetic field technology, this method can image microwave magnetic fields with frequencies ranging from microwave to terahertz band and resolution as low as atomic scale, It provides a new idea to solve the current situation of lack of imaging means in terahertz band. The reviewer also pointed out that "this technology can be used in terahertz near-field imaging and will be an important application point" and "there is no doubt that it is a very valuable method".