In-orbit test of the weak equivalence principle with atom interferometry

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 an 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 (-2.7 ± 4.7) × 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.