(a) Experimental setup. The optical dipole trap is composed of two focused red-detuned laser beams in x and y directions. The gravity is in − z direction. Ultracold atoms are simultaneously probed in the vertical and horizontal directions. (b) Measuring the trapping frequencies by probing the oscillations of the centers of mass along three directions respectively. Each experimental data is the average of three measurements. The solid line is the fitting with a sinusoidal wavefunction.