Creation and measurement of a coherent superposition of quantum states

We demonstrate experimental techniques for creating and measuring a coherent superposition of two degenerate atomic states with equal amplitudes in metastable neon. Starting from state P-3(0), we create adiabatically a coherent superposition of the magnetic sublevels M=+/-1 of the state P-3(2) using a tripod stimulated Raman adiabatic passage scheme. The measurement is based on the coupling of the levels P-3(2)<---->P-3(1) by a linearly polarized laser, followed by the detection of the population in the P-3(2)(M=+/-2) states as a function of the polarization angle of that laser.