PhD defense: Carlos Fernando Duarte Faurby

Fusion-Based Quantum Photonics with Quantum Emitters

Photonic quantum computers have the unique potential to directly integrate a rapidly emerging technological platform: photonic microchips, with very promising qubit candidates: single photons generated by quantum emitters. The fundamental lack of photon-photon interactions presents a challenge in practical implementations, but recent theoretical frameworks present a workaround, where the need of entangling operations is replaced by conducting single and multi-photon measurements on already-entangled qubits. Fusion-basedquantum computing is one such theoretical framework, which is of special interest due to its affordable hardware requirements.

This thesis presents four proof-of-principle experiments in quantum information processing, showcasing essential steps towards fusion-based quantum computing using quantum emitters and photonic integrated circuits. 

We perform a first demonstration of a time-like fusion operation between two deterministically generated resource states.  We proceed to showing the interface between single photons from a quantum dot and photonic integrated circuits (PICs) in the Silicon Nitride platform.  We find that photonic indistinguishability is one of the main limiting factors in the fidelity of on-chip fusion operations. We address this limitation by experimentally demonstrating that highly indistinguishable photons can be obtained through quantum interference between multiple photons and heralded detection on a subset of them. 

Finally we employ a large reprogrammable silicon PIC to successfully implement a method to replicate the ground state dynamics of different interacting spin systems, suggesting that the technologies presented in this thesis also may have immediate applications.