#### Special topics

SPECIAL TOPIC — Ultracold atom and its application in precision measurement

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 Select Improve the performance of interferometer with ultra-cold atoms Xiangyu Dong(董翔宇), Shengjie Jin(金圣杰), Hongmian Shui(税鸿冕), Peng Peng(彭鹏), and Xiaoji Zhou(周小计) Chin. Phys. B, 2021, 30 (1): 014210.   DOI: 10.1088/1674-1056/abcf33 Abstract （387）   HTML （3）    PDF （3289KB）（244）       Ultra-cold atoms provide ideal platforms for interferometry. The macroscopic matter-wave property of ultra-cold atoms leads to large coherent length and long coherent time, which enable high accuracy and sensitivity to measurement. Here, we review our efforts to improve the performance of the interferometer. We demonstrate a shortcut method for manipulating ultra-cold atoms in an optical lattice. Compared with traditional ones, this shortcut method can reduce the manipulation time by up to three orders of magnitude. We construct a matter-wave Ramsey interferometer for trapped motional quantum states and significantly increase its coherence time by one order of magnitude with an echo technique based on this method. Efforts have also been made to enhance the resolution by multimode scheme. Application of a noise-resilient multi-component interferometer shows that increasing the number of paths could sharpen the peaks in the time-domain interference fringes, which leads to a resolution nearly twice compared with that of a conventional double-path two-mode interferometer. With the shortcut method mentioned above, improvement of the momentum resolution could also be fulfilled, which leads to atomic momentum patterns less than 0.6 $$\hbar k_L$$. To identify and remove systematic noises, we introduce the methods based on the principal component analysis (PCA) that reduce the noise in detection close to the $$1/\sqrt2$$ of the photon-shot noise and separate and identify or even eliminate noises. Furthermore, we give a proposal to measure precisely the local gravity acceleration within a few centimeters based on our study of ultracold atoms in precision measurements.