Abstract: | The question of localization of relativistic particles and the ensuing uncertainty relations is not yet fully resolved. We present a consistent derivation of localization probability and current that are built from the energy density of a quantized field, particleʼs momentum-space wave function and its energy. The resulting probability density for photons can be derived from the Newton-Wigner wave function, even if the Newton-Wigner position operator does not exist. Using it we derive a sharp uncertainty relation ΔqΔp >hbar/2 that is testable with experimentally realizable single-photon states. |