Quantum light generation by semiconductor devices

Often referred to as "artificial atoms", quantum dots possess discrete energy levels that make them viable hosts for electronic qubits or sources of photonic qubits. However, unlike atoms, no two quantum dots are alike, a complication for quantum information schemes requiring either indistinguishable electronic states in different quantum dots, or indistinguishable photons emitted from different quantum dots. We demonstrate here that the transition energy of a quantum dot can be continuously varied, over a range much larger than the linewidth, using an electric field applied in a diode structure. By tuning individual quantum dots to identical energies we demonstrate two-photon interference of photons emitted from truly remote, independent quantum dots, thereby overcoming a significant barrier to scalable quantum information processing.