Figure 4.

HOM-type two-photon interference experiments of photons emitted by the XX-state for co- (red) and cross- (gray) polarized measurement configuration. Photon coalescence described by the Hong–Ou–Mandel effect is confirmed by the clear suppression of coincidences in the central peak for copolarized photons. We observe record-high photon-indistinguishabilities of V_raw = 29(2)% and V_4ns = 35(3)% by integrating the raw experimental data over the full 12.5 ns- and a 4 ns-wide delay-window, respectively. The inset shows the same data for a broader range of arrival time delays.