Developing indistinguishable heralded single-photon sources in silicon photonics

• Main Author: Faruque, Imad
• Other Authors: Thompson, Mark ; Rarity, John
• Published: University of Bristol 2018
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.767950

Quantum photonics is one of the newest strands of research that shares the border between fundamental science and state of the art technology. Many of the visions of quantum photonics, for example, linear optical quantum computing, require ideal single-photon sources (SPSs). A key pre-requisite of an ideal SPS is the near unity (>99%) indistinguishability among single-photons from multiple SPSs. This is a true measure of scalability, as multiple indistinguishable SPSs can be integrated on a single chip for performing complex quantum information algorithms. To date, higher than 95% indistinguishability has not been shown in any photonic platform. Silicon on insulator (SOI) photonics is one of the platforms that promises a near ideal heralded SPS. It also offers mature fabrication technology, truly scalable architecture and a roadmap to electronic integration. If higher than 99% indistinguishable SPSs are achieved, it will pave the way to implement adequately complex algorithms that cannot be reproduced using classical computers. The primary focus of this thesis is to investigate ways to achieve and compare indistinguishable heralded SPSs in the SOI photonic platform. Specifically, we have chosen two well-known structures as heralded SPSs: nanowire waveguides and micro-ring resonators. Although the brightness and purity of the single-photons generated in those two structures are investigated both theoretically and experimentally, the indistinguishability data is scarce in the literature. In fact, the indistinguishability of the micro-ring resonator heralded SPSs has not been experimentally demonstrated in SOI or any other photonic platform. The intrinsic resonance enhancement in the resonator predicts high brightness and purity simultaneously with high indistinguishability. Thus, designing and implementing on-chip photon indistinguishability measurement (PIM) circuits for micro-ring resonator SPSs cover a significant portion of this thesis. Also, the purity of the designed heralded SPSs has been simulated, and the effects of the possible imperfections of the PIM circuits along with practical SPSs have been investigated with numerical models. As such, the study presented here provides insights into the indistinguishability of the heralded SPSs to build scalable quantum technologies in SOI photonic platform.