Controllable Photonic Time-Bin Qubits from a Quantum Dot

Photonic time-bin qubits are well suited to transmission via optical fibers and waveguide circuits. The states take the form1(2)(α|0⟩+eiϕβ|1⟩), with|0⟩and|1⟩referring to the early and late time bin, respectively. By controlling the phase of a laser driving a spin-flip Raman transition in a single-hole-charged InAs quantum dot, we demonstrate complete control over the phase,ϕ. We show that this photon generation process can be performed deterministically, with only a moderate loss in coherence. Finally, we encode different qubits in different energies of the Raman scattered light, paving the way for wavelength-division multiplexing at the single-photon level.