  We find that biorthogonal quantum mechanics with a scalar product that counts
both absorbed and emitted particles leads to covariant position operators with
localized eigenvectors. In this manifestly covariant formulation the
probability for a transition from a one-photon state to a position eigenvector
is the first order Glauber correlation function, bridging the gap between
photon counting and the sensitivity of light detectors to electromagnetic
energy density. The position eigenvalues are identified as the spatial
parameters in the canonical quantum field operators and the position basis
describes an array of localized devices that instantaneously absorb and re-emit
bosons.
