Why Two-Photon but Not Two Photons?

Yanhua H. Shih, Dmitry Strekalov, T. D. Pittman +1 more

In his famous book, The Principles of Quantum Mechanics, Dirac stated that “... photon ... interferes only with itself. Interference between two different photons never occurs.” However, two-photon interference has been demonstrated experimentally. Was Dirac wrong? We report an new experiment in this paper. It demonstrated that two-photon interference can not be considered the interference of two photons. “Two-photon” is not two photons. Two-photon is a single entity, which is just like a photon. We may call it biphoton. Dirac was correct. Biphoton interferes only with itself.

Strekalov, Pittman, Рубин +1 more

Dmitry Strekalov, T. B. Pittman, Morton H. Rubin +1 more

What is the difference between two-photon phenomena and phenomena involving two photons? We address this question by reporting two two-photon interference experiments. In the first experiment we show that two-photon interference does not require the “indistinguishability” of two photons, and hence is not interference of two photons.

Toshihiro Nakanishi, Hirokazu Kobayashi, Kazuhiko Sugiyama +1 more

For dissipation-free photon-photon interaction at the single photon level, we analyze one-photon transition and two-photon transition induced by photon pairs in three-level atoms using two-photon wavefunctions. We show that the two-photon absorption can be substantially enhanced by adjusting the time correlation of photon pairs. We study two typical cases: Gaussian wavefunction and rectangular wavefunction. In the latter, we find that under special conditions one-photon transition is completely suppressed while the high probability of two-photon transition is maintained.

Josiah Sinclair, Greg Dmochowski, Matin Hallaji +2 more