SPACE-TIME LOCALIZATION WITH QUANTUM-FIELDS

We introduce observables associated with the space-time position of a quantum point defined by the intersection of two light pulses. The tim e observable is canonically conjugated to the energy. Conformal symmet ry of massless quantum fields is used first to build the definition of these observables and then to describe their relativistic properties under frame transformations. The transformations to accelerated frames of the space-time observables depart from the laws of classical relat ivity. The Einstein laws for the shifts of clock rates and frequencies are recovered in the quantum description, and their formulation provi des a conformal metric factor behaving as a quantum observable.