China University of science and technology has made important progress in nano scale quantum sensing research
Academician Guo guangcan's team has made important progress in the research of nano scale quantum sensing. Professor Sun Fangwen's research group of the team combined quantum sensing technology with optical super-resolution imaging technology to study the ultra-small localization and high-precision detection of nano-scale electromagnetic field, and experimentally realized the localization of electromagnetic field at the wavelength of one millionth. Based on this finding, the local electromagnetic field energy and the interaction intensity with matter are further increased by 8 and 4 orders of magnitude, respectively. The achievement is based on "focusing the electromagnetic field to 10-6" λ For ultra-high enhancement of field matter interaction "was published in the internationally renowned journal Nature communication on November 4.
In general, electromagnetic waves can be bound within their wavelength range because of their volatility. However, in order to pursue strong interaction with matter, nanoscience needs to realize smaller scale electromagnetic field localization and detection, and promote the development of nanotechnology, information storage, biosensor, microwave photonics and quantum information. At present, based on evanescent field coupling, the localization of electromagnetic field in sub wavelength scale can be realized, and has been widely used in the fields of micro, nano optoelectronics and so on. In addition, the effective detection of electromagnetic field with high spatial resolution also restricts the mechanism research and application development of the interaction between electromagnetic field and matter in nano scale.
Sun Fangwen's research group has been committed to using quantum sensing technology to realize high-precision detection of micro and nano electromagnetic fields. Based on the diamond nitrogen vacancy system, an ultra-low pump power charge state depletion nano imaging technique is proposed and developed to achieve 4.1 nm spatial resolution imaging and quantum state regulation (light: Science & applications 4, e230 (2015); Phys. Rev. Appl. 7014008 (2017)).
In this study, the research group combined the charge state depletion nano imaging with the quantum sensing technology of nitrogen vacancy color center to characterize the nano scale microwave field. Experimentally, by detecting the spin transitions of different axial nitrogen vacancy color center electrons pumped by the local microwave field around the nanowire (wavelength: 10.4 cm), it is observed that the microwave field can be localized in the region of about 291 nm near the nanowire, which is equivalent to 10-6 times of its wavelength. By further measuring the intensity and vector information of nano scale electromagnetic field, it is found that the localization of the deep sub wavelength comes from the near-field radiation of electron motion in one-dimensional nano conductive materials, rather than the evanescent field of electromagnetic wave. Based on the experimental results, the research group designed a metal nanowire bow antenna structure to collect, localize and enhance the interaction with electron spin. By measuring the Rabi oscillation of electron spin pumped by local microwave field, it is observed that this structure can enhance the local microwave energy by 8 orders of magnitude and increase the interaction intensity with spin by 4 orders of magnitude. Using the polarization dependence of the nanowire bow antenna, the research group also realizes the selective manipulation of spin bits by changing the polarization of free space microwave field, and verifies that the structure is used for high spatial resolution quantum bit manipulation.
This achievement successfully applies high spatial resolution quantum sensing to nano science research, and provides an effective tool for exploring the interaction between electromagnetic field and matter in nano scale. The interaction between deep sub wavelength electromagnetic field and local and super electromagnetic field and matter realized in the experiment can be used not only for far-field qubit manipulation, but also for the measurement of very weak electromagnetic signals, such as the development of microwave radar based on qubit.
The first author is Dr. Chen Xiangdong, associate researcher of the Key Laboratory of quantum information, Chinese Academy of Sciences, and the corresponding author is Professor Sun Fangwen. The work was supported by the Ministry of science and technology, the Foundation Committee, the Chinese Academy of Sciences and Anhui Province.
Link：https://www.nature.com/articles/s41467-021-26662-5
