Independent indistinguishable quantum light sources on a reconfigurable photonic integrated circuit

We report a compact, scalable, quantum photonic integrated circuit realised by combining multiple, tuneable InGaAs/GaAs quantum dot single photon sources with a silicon oxynitride waveguide circuit. Each waveguide in the circuit is addressed by a separate, electrically controlled quantum dot-containing diode. We show that the quantum dot emission from neighbouring diodes can be independently tuned to degeneracy using the Stark Effect and that the resulting photon streams are indistinguishable. This enables on-chip Hong-Ou-Mandel-type interference, as required for many photonic quantum information processing schemes. Photonic Integrated Circuits (PICs) are rapidly becoming the default platform for photonic quantum applications due to their robustness, interferometric stability, reconfigurability, and scalability.1–3 Furthermore, they allow complex optical systems which, until recently, would occupy a whole laboratory to be reduced to the size of a single chip. PICs have been employed in many quantum applications including logic gates,2,4 higher order path entanglement,5 quantum walks,6,7 tests of Boson Sampling,8–11 and on-chip quantum teleportation.12 These PICs can support optical qubits encoded in path, time bin, polarisation or mode and can be interconverted.13,14 All of these experiments have relied upon photons generated externally and delivered to the PICs through fibre. One route to achieve on-chip photon generation is to use silicon waveguides to directly produce photons,15,16 but the Poissonian statistics of pair generation makes this inherently unscalable. An alternative scheme is to use quantum emitters with naturally sub-Poissonian photon statistics within a waveguide circuit made of the emitter's host material.17–20 It is also possible to evanescently couple the emitter to a low-loss PIC21–23 and these schemes have verified the emission of single photons. However, for realising large scale and compact circuits, it will be necessary to integrate multiple sources of indistinguishable photons on the ...