Test Of The Equivalence Principle With Atoms In Different Internal States

The general relativity decribes the gravitational interaction and the prophecies of many physical phenomena have been proved.In order to unify the gravity and other fundamental interactions,many theories and models have been proposed in succession,which predict the violation of equivalence principle that is one of the most fundamental postulations of the general relativity.In order to verify the validity of these new theories and study the scope of application of the equivalence principle,high precision experiments are required to test the validity of equivalence principle.In recent years,the development of high precision atom interferometer makes it possible to use quantum system to test the equivalence principle.Testing the equivalence principle with test masses of microscopic particles has the advantage of higher potential precision,and it is supposed to shied a light on possible new physics.In this thesis,we have performed a precision Bragg atom interferometry on testing the equivalence principle with cold atoms in different quantum states.The main works are presented as follows:1.We developed the composite optical system to realize the two-photon stimulated Raman transition and multi-photon Bragg diffraction respectively,and completed the coherent manipulation of atoms with sequential control.After the optimization of the Raman and Bragg pulses,high precision Bragg atom interferometer with diffraction order of n=2 and pulse sepration time of T=250 ms has been realized.The contrast of Bragg interference fringes is 15%and the sensitivity of measuring the gravity acceleration is 1.6×10-8g/(?).2.Testing the equivalence principle with 87Rb in different hyperfine states.We prepared atoms in ground states of different hyperfine states |1>and |2>,and realized the measurement of differential gravtational acceleration based on the Bragg interferometer and the detection method with Raman spectroscopy.With analyzing and eliminating the systematic effects due to the multiwave interference and the overlap of atom wavepacket,we had obtained an Eotwos ratio ?1-2=(0.9±2.7)×10-10,after correcting various systematic errors.With an improvement of 5 times on the test precision comparing to the reported results,this result showed that the equivalence principle is still valid at the precision of 10-10.3.Futher using atoms in the coherent superposition of magnetic states to test the equivalence principle and studing the impact of quantum property when pushing the test to three-dimensional Hilbert space at the first time.We prepared atoms in the coherent superposition |s>of three magnetic states,and compared the gravity acceleration with atoms in single state |0>.Then we obtained an E(?)tw(?)s ratio ?0-s=(-2.3±4.0)×10-9,indicating that the equivalence principle was still valid at 10-9 level without depending on test masses whether staying in quantum superposition or not.4.We proposed a spin-gravity operator to describe the possible breaking mechansim of the equivalence principle when atoms in superposed spin states free falling in the gravitational field.After considering the noises of atom interferometer with atoms in state|s>,we set an upper bound to the off-diagonal terms of possible spin-gravity coupling operator as |b|?4×10-8 and |c| ?9×10-8.