Test Of The Equivalence Principle With Atoms In Different Spin Orientations

General relativity?GR?and quantum mechanics are two fundamental physics theories which were born in the early twentieth century.Both of them have achieved great success in describing the objective physical world in their respective applicable domain.Gravity is described by GR,but GR is a classical theory,which does not achieve quantization.Attempts to quantify gravity,such as the standard model extension,dilaton model,string theory,loop quantum gravity etc.need the breaking of the equivalence principle?EP?.As one of the fundamental hypotheses of GR,whether the EP is broken or not depends on high precision experimental tests.Traditional experiments have achieved a test precision of 1310-,and a number of space and ground projects are still devoted to further improve the test precision.On the other hand,searching for new breaking mechanism of the EP is another important development trend.Especially in recent years,with the development of atom interferometer,it is possible to test the EP at higher precision using microscopic particlesIn this thesis,we focus on whether the intrinsic spin of atom is coupled with gravity or spacetime torsion,and therefore leads to the breaking of the EP.The main research contents and results are as follows:?1?A novel experiment about testing the spin orientation related EP using cold atom interferometer is carried out.By comparing the difference of the free fall accelerations of atoms with opposite spin orientations in the same gravitational field,the breaking of the EP caused by possible spin-gravity coupling and spin-torsion coupling is examined in quantum realm.?2?The spin orientation related EP is tested using atoms at the level of 10^-7.Since interferometers with atoms in spin orientation polarized states ?m_F=±1? are highly sensitive to magnetic field inhomogeneity,three strategies have been applied to reduce the inhomogeneity influence: background magnetic field shielding,local magnetic field gradient compensation and quasisymmetry interference timing.With these basic improvements,the interfering pulse interval T is increased from 2 ms to 25 ms,and the phase uncertainty of the fitting fringe is only about 30 mrad,which largely improve the measurement sensitivity.Furthermore,a double differential measurement method,which combines reversing the Raman wavevector direction and modulating p pulse timing,is developed to alleviate the residual magnetic field inhomogeneity contribution.The final resultant E?tv?s ratio is ?_s?0.2±1.2?×10^-7.And this result gives an upper constraint of 5.4×10^-6m^-2 for possible spacetime torsion gradient at the first time.?3?Inspired by the test using atom interferometer,we propose a new scheme to test the EP in a cold molecular fountain.The molecular rotational orientation is polarized using state selection by a hexapole electromagnet.The molecular beam is decelerated by a traveling wave Zeeman decelerater,and the cold core is selected to form a molecular fountain.Based on the design of the parameters,three-dimensional Monte Carlo numerical trajectory simulations about the whole procedure are carried out.According to the simulation results,the anticipated test precision of the rotation orientation related EP using molecules is at the level of 10^-7.