Figure 4.

Heralded spectroscopy. (a) Two-dimensional histogram of photon pairs following the same excitation pulse, according to the energy of the first (E_BX) and second (E_1X) photons (vertical and horizontal axes, respectively), over a 5 min measurement. Dashed green line serves as a guide to the eye, marking the same energy for both photons (undetectable by the system). (b) Spectrum of the BX (red dots), 1X (blue rings), and all on state detections (gray area, normalized). Solid red and dashed blue lines are fits of the BX and 1X spectra, respectively, to a Cauchy–Lorentz distribution. Binding energy, estimated as the difference between BX and 1X spectral peaks, is ε_b = 9.3 ± 1.0 meV. (c) Binding energy as a function of 1X spectral peak for 30 QDs. Error bars depict 68% confidence intervals.