The intimate relation between interference and diffraction has its origin in the interference equation itself. - F. J. Duarte

The EPR claim of an "all values" spread in the coordinate depends on an idealized absolute and exact measurement of <math>p</math> with <math>\Delta p\ = 0</math>. Since this is physically impossible, the claim of "no physical reality" can be negated.

The longer the cavity and the narrower the beam waist, the better the beam quality of the laser emission, or
<math> |\langle x | s \rangle|^2\ = \sum_{j=1}^\N\,\Psi(r_j)^2\ +2 \sum_{j=1}^\N\,\Psi(r_j)\bigg(\sum_{m=j+1}^\N\,\Psi(r_m)cos(\Omega_m-\Omega_j)\bigg) </math>

The Dirac notation, though originally applied to the propagation of single particles, also applies to describing the propagation of ensembles of coherent, or indistinguishable, photons.