The Weak Equivalence Principle (WEP) is a central pillar of general relativity. Its precise test with quantum systems in space offers a unique window onto new physics. Here we report the first in-orbit quantum test of the WEP. A dual-species (85Rb/87Rb) atom interferometer is realized aboard the China Space Station. Methods of platform motion suppression, fluorescence detection switching, and two-photon detuning switching are developed to eliminate phase noise and improve measurement accuracy. A test uncertainty of 2.8*10-8 is obtained from 280 days of WEP test data, and a test result of (-3.1+/-4.6)*10-7 is achieved after error estimation. This improves prior atom-interferometric WEP tests in microgravity by three orders of magnitude. This work paves the way for space-borne quantum inertial sensors and their application to future fundamental physics in space.
In the atom-interferometric test of the weak equivalence principle (WEP) with multicomponent atomic gases, the difference in the center-of-mass positions between different components, as well as the difference in the center-of-mass velocities, leads to systematic uncertainties. An effective way to reduce these systematic uncertainties is to suppress such differences at the preparation stage of atomic sources. In this work, we propose an efficient strategy for preparing two-component gases with a perfectly spatial overlap of the center-of-mass positions and that of the velocities, according to a scheme of the time-optimized atomic lensing mechanism. The key of the time-optimized atomic lensing lies in a two-step quench process of the trap frequency, which is accessible in free-fall experiments by appropriately manipulating the trapping frequency and the center position of the trap. By taking a dual-species rubidium atomic gas as an example, our calculations indicate that the differences in the center-of-mass positions and velocities between
85Rb and
87Rb atoms are simultaneously eliminated, which provides an optimized starting point to test the WEP. An estimation of the systematic uncertainties is also presented. Our method can serve as a potential protocol for the preparation of atom sources in tests of the WEP with multicomponent atomic gases.