Figure 1: Schematic of time-bin entanglement generation and analysis.
(a) Energy-level scheme for resonant two-photon excitation of a biexciton (|b›) from the ground state (|g›). The H-polarized pump laser populates the biexciton state resonantly through a virtual level (dashed grey line). Following the excitation, a V-polarized biexciton (XXV) exciton (XV) photon cascade is generated through the intermediate exciton state (|xV›). Exciton and biexciton photons are detuned from the excitation laser due to the biexciton binding energy Eb. (b) Quantum dot emission spectrum. (c) Scheme to generate and analyse time-bin entangled photons. Outputs of analysing interferometers, X1, X2, XX1 and XX2, are fibre coupled to avalanche photon diodes (APD). Here, φP, φX and φXX are the phases in the pump and analysing interferometers, respectively, and Δt is the time difference between the early and late time bins.
