Anders Sørensen

Quantum emitters, e.g. quantum dots, in optical waveguides have matured to a level where we can achieve almost ideal control of light-matter interactions. I will describe ongoing experimental and theoretical efforts to scale quantum dots in optical waveguides into full scale quantum information processors. By embedding a spin in a quantum dot we can turn it into a source of large scale photonic entanglement. By interfering the emitted photons with linear optical elements and detecting the output, these photonic resource states can be fused into even larger strutures and this can form the basis of fault-tolerant quantum computers. 

I will describe how we use quantum dots as sources of photonic entanglement and our first preliminary attempts at fusing them into larger structures. I will also discuss how the sources fit into the envisioned architectures for quantum computing and the requirements that this put on the sources. 

A drawback of the fusion process described above is that it is probabilistic and only succeed with a probability of at most 50%. This can be remedied by exploiting the non-linear response of the quantum dots. If two photons are incident on a two-level system simultaneously, it creates an effective interaction between the photons. If time allows, I will describe how we observe and can potentially exploit this interaction to increase the fusion success probability and thereby lower the requirements for fault-tolerant quantum computation. By adding additional quantum dots to the waveguide and sending in more photons, we enter into the regime of many-body quantum optics where we can engineer light-matter interaction one emitter and one photon at a time.