Two-Photon Wave Packets

Yoon-Ho Kim

One-photon and two-photon wave packets of entangled two-photon states in spontaneous parametric downconversion (SPDC) fields are calculated and measured experimentally. For type II SPDC, measured one-photon and two-photon wave packets agree well with theory. For type I SPDC, the measured one-photon wave packet agrees with the theory. However, the two-photon wave packet is much bigger than the expected value, and the visibility of interference is low. We identify the sources of this discrepancy as the spatial filtering of the two-photon bandwidth and nonpair detection events caused by the detector apertures and the tuning-curve characteristics of the type I SPDC.

Dmitry Strekalov, T. B. Pittman, Yanhua H. Shih

We report a two-photon interference experiment in which a single-photon wave-packet concept fails to give a correct prediction, but the two-photon wave-packet, or biphoton, concept is helpful. Based on our experiment, we argue that single-photon wave-packet information available from two-photon measurement is limited.

Barbara A. Capron

Mads Middelhede Lund, Fan Yang, Klaus Mølmer

We employ a cascaded system approach to numerically simulate the interaction of photon pulses with a two-level scatterer in a chiral waveguide QED setup and show that the scattering of a two-photon pulse may lead to the predominant population of only two output wave packet modes in an entangled state, $|2,0\ensuremath{\rangle}--|0,2\ensuremath{\rangle}$. In a complementary wave-packet basis, this is a product state of two orthogonal single-photon wave packets. Operating this process in reverse allows a perfect merging of distinguishable single-photon wave packets into a single-mode pulse carrying two identical photons.