Neutral kaons from ϕ meson decays are produced in pairs, which offers the possibility to select pure kaon beams: the detection of a Ks (KL) tags the presence of a KL (Ks), the same holds for charged kaons. This allows to perform precise measurement of kaon properties. Additionally, these neutral kaon pairs are produced in a pure quantum state (JPC = 1−−), which allows to investigate CP and CPT symmetries via quantum interference effects, as well as the basic principles of quantum mechanics.Introduction to kaon interferometry and the results on the decoherence parameter and CPT test obtained by the KLOE experiment at the DAΦNE e+e− collider will be presented together with prospects for KLOE-2 project.