Testing the Universality of Free Fall by Comparing the Atoms in Different Hyperfine States with Bragg Diffraction

We perform a precision atom interferometry experiment to test the universality of free fall. Our experiment employs the Bragg atom interferometer with ^87Rb atoms either in hyperfine state \left| F = 1,m_F = 0 \right\rangle or \left| F = 2,m_F = 0 \right\rangle , and the wave packets in these two states are diffracted by one pair of Bragg beams alternatively, which is helpful for suppressing common-mode systematic errors. We obtain an Eötvös ratio \eta_1 - 2 = \left( 0.9 \pm 2.7 \right) \times 10^- 10, and set a new record on the precision with improvement of nearly 5 times. This measurement also provides constraint on the difference of the diagonal terms of the mass-energy operator.