Scalable in operando strain tuning of multiple quantum dots within a photonic waveguide architecture.

The quest for an integrated quantum optics platform involving solid state waveguides and cavities combined with semiconductor quantum dots has motivated the field of quantum semiconductor research for two decades. Demonstrations of discrete quantum light sources, single photon switches, transistors, and quantum memory-photon interfaces have become very advanced. Yet the fundamental problem that every quantum dot is different prevents integration and scaling beyond a few quantum dots. Here, we address this challenge by patterning strain via local phase transitions to selectively tune individual quantum dots that are embedded in a photonic architecture. The patterning is implemented with in operando micro-laser crystallization of a thin HfO_2 film sheath on the surface of a GaAs waveguide. Using this approach, we tune InAs quantum dot emission energies over the full inhomogeneous distribution with a step size down to the homogeneous linewidth and a spatial resolution better than 1 mum. As a demonstration, we tune three quantum dots to the same energy within a waveguide. This approach is general, and the same principles extend to other solid-state quantum emitters and photonic structures.