Investigation of spin entanglement produced from elastic scattering of unpolarized electrons

A symmetric electron–electron scattering experiment has been set up, where the electrons differ from each other only by their spin direction. At these conditions a spin entanglement of the scattered electrons is expected, but was not yet observed. To demonstrate the spin entanglement, a single particle-resolved spin measurement of the electrons has to be performed. Till date, a high ratio of coincidences normalized to random coincidences could be demonstrated only without performing a spin measurement. It is shown that this ratio is related to an experiment-depending nearly constant efficiency of coincidence detection. To enhance the efficiency of the spin detection, a new compact mini-Mott spin analyzer has been developed. Due to a compact small size of this analyzer, a higher efficiency which is a prerequisite to the electron spin resolved coincidence measurements is obtained now.