University of Science and Technology of China realizes quantum elliptical polarization imaging

Recently, the team led by Academician Guo Guangcan from the University of Science and Technology of China has made significant progress in the research of quantum elliptical polarization imaging. The research group of Professor Shi Baosen and Associate Professor Zhou Zhiyuan combined high-quality polarization entangled light sources with classical polarization imaging technology to observe the birefringence characteristics of periodically distributed anisotropic materials in weak light fields. They also demonstrated that under the same light intensity environment, the system has higher detection accuracy and anti stray light interference ability compared to classical measurement systems. This achievement was published online on April 4th in the internationally renowned journal Npj Quantum Information.

Polarization imaging technology can capture polarization related characteristics in materials, significantly enhance the contrast between background and target that is difficult to distinguish in traditional imaging, and measure optical constants, chiral features, stress-strain distributions, and other parameters that cannot be detected by conventional imaging. Its application scope covers basic physics research as well as cutting-edge fields such as target recognition, stress detection, biomedical diagnosis, and remote sensing. The introduction of quantum light source illumination in polarization imaging has opened up a new way to improve measurement accuracy, especially in low light fields. Researchers have theoretically and experimentally proven that specific quantum light sources have the ability to break the standard quantum limit under the same illumination intensity, and the non local characteristics of entangled photon sources are also of great significance in the field of remote control. So far, the focus of quantum imaging work has been on accurately measuring the external shape of the tested sample. Quantum research related to polarization has mostly focused on detecting the single point birefringence properties of uniform materials, while the combination of polarization imaging and quantum entanglement is still to be explored.

Professor Shi Baosen, Associate Professor Zhou Zhiyuan, and others have long been engaged in research on the preparation and application of non classical quantum light sources based on nonlinear processes. Currently, quantum light sources have been applied to edge detection of quantum metasurfaces [Sci. Adv. 6, eabc4385 (2020)], and the study of photon interference behavior in polarization interferometers [Phys. Rev. Lett. 120263601 (2018)]. In this work, the team introduced the advantages in the preparation and characterization of polarization entangled quantum light sources into a classical photometric polarization detection system. By constructing a dual path polarization detection structure with separated control and measurement ends, the construction of a quantum ellipsoidal imaging system was achieved. This work selects anisotropic materials with periodic birefringence characteristics as samples, and uses the Structural Similarity Index (SSIM) as a quantitative measure of imaging quality. Under low illumination conditions where the light intensity gradually decreases to the hundred photon level and different intensities of stray light sources, the results of quantum and classical polarization imaging systems are evaluated and compared to verify that the quantum ellipsoidal imaging system has higher measurement accuracy and stronger anti-interference characteristics under weak light conditions. In addition, the team utilized the unique non locality of entangled light sources to demonstrate the system's ability to remotely manipulate the incident polarization state. This feature reduces the interference of the quantum ellipsometry system on the measurement optical path during the detection process to a lower level, which is beneficial for the stability of the detection results and is suitable for some complex detection environments that are unreachable or easily disturbed.

Figure 1. Experimental setup diagram

Figure 2. Imaging comparison under different incident light intensities

Figure 3. Imaging comparison under different noise environments

This work is an interesting attempt to combine quantum entanglement with polarization imaging. By combining the advantages of both fields, this system is expected to achieve potential applications in polarization characteristic detection of photosensitive thin film materials, non-contact and non-invasive biomedical polarization imaging, and target recognition in complex weather environments. Jie Mengyu, a postdoctoral fellow who has graduated from the University of Science and Technology of China, and Niu Sujian, a doctoral student who has already graduated, are co first authors. Shi Baosen and Zhou Zhiyuan are co corresponding authors of the paper. This work has been supported by the "double first-class" construction funds from the National Natural Science Foundation of China, the Chinese Academy of Sciences, the Ministry of Science and Technology and the University of Science and Technology of China.

Source: opticsky