Phd Defense: Vasiliki Angelopoulou

Large-scale entangled quantum states of multiple photons are considered a promising resource for measurement-based quantum computing and long-range quantum communication. 

One approach to scaling up the dimensions of the entangled states, allowing for improved tolerance to qubit losses, involves coupling multiple emitters to create a highly entangled photon state up front.

Direct signatures of coupling between self-assembled quantum dots (QDs) have been challenging to observe, primarily due to inhomogeneities in their emission frequencies and position, along with their susceptibility to decoherences from the environment.

In the present work we demonstrate the first photon-mediated coupling between different pairs of InAs QDs, embedded in a nanophotonic waveguide.

Super- and subradiant coherent dynamics of the coupled system are directly observed in the lifetime measurements, and a proof-of-principle preparation of the collective state is realized. We further probe the coupled system by recording the second-order intensity correlations. Adding to previous investigations, we suggest that the emerging anti-dip at zero time delay can be an exclusive signature of superradiance, when only a single emitter is driven.  

Our findings constitute fundamental research, aiming to serve as the stepping stone towards multi-emitter applications in quantum technologies on-chip.