We study a system of few electrons over a film of liquid helium. The advantage of putting the electrons over the film of helium is that it provides almost ideal isolator. Unlike metal or semiconductors, where electrons are never more than few nanometers from an impurity or a crystalline defect, liquid helium has no defects. The behaviour of the quasiparticles in helium, such as surface or bulk waves (ripplons and phonons) and their interaction with electrons is rather well understood. We control the electrons with system of electrodes under the helium film and detect their motion with a Single Electron Transistor, which is an extremely sensitive electrometer. We plan to isolate a single electron in a metallic ring electrode and study its relaxation time. If the relaxation is as slow as predicted by theory, this system can be used as an element of a quantum computer.