Four-wave mixing (4WM) in the hyperfine Paschen-Back (HPB) regime
In the absence of a magnetic field, multiple-path interference results in a 4WM signal that is complex and difficult to model. In the presence of a high magnetic field (0.6 T), entry into the HPB regime removes the interference and results in a "clean" 4WM signal which is readily modelled with 4-level Optical Bloch equations
Heralded single photons
Through a four-wave mixing (4WM) process in rubidium-87, we can generate heralded bichromatic single photons from an atomic collective spin excitation (CSE). The photon arrival times display collective quantum beats (see image below), a novel interference effect that results from the relative motion of atoms in the CSE.