Lorentz-invariant mass and entanglement of biphoton states
arXiv:1905.03459 · doi:10.1088/1612-202X/ab1dde
Abstract
The concept of the Lorentz-invariant mass of a group of particles is shown to be applicable to biphoton states formed in the process of spontaneous parametric down conversion. The conditions are found when the Lorentz-invariant mass is related directly with (proportional to) the Schmidt parameter determining a high degree of entanglement of a biphoton state with respect to transverse wave vectors of emitted photons.