Utilising Non-Unitary Integrated Quantum Photonics to realise Variational Quantum Algorithms

David D Roberts

Edouard Brainis, Marc Haelterman

La dissertation explore differentes applications des fibres optiques en ingenierie quantique. Deux thematiques sont developpees : d'une part l'utilisation des fibres optiques monomodales en silice pour l'implementation d'algorithmes et de protocoles de communication quantiques et d'autre part l'utilisation de la non-linearite de ces fibres pour realiser des sources de paires de photons correles. L'etude est a la fois theorique et experimentale./ The dissertation explores various uses of optical fibers for quantum engineering. Two topics are developed : first the use of single-mode silica fibers for implementing quantum algorithms and communication protocols, second the use of these fibers for generating correlated photon-pairs.

Thomas P. Pearsall

Mark G. Thompson, Alberto Politi, Jonathan C. F. Matthews +1 more

Although practical realisation of a fully functioning quantum computer is still a long way off, recent progress both experimentally and theoretically is paving the way for possible implementations. One of the leading approaches is quantum optics, where photons are used as carriers of quantum information, and are manipulated in both linear and non-linear optical circuits. More recently, advances in integrated quantum photonics are enabling the realisation of compact and stable quantum gates and circuits. This approach provides routes to enhancing the complexity of quantum optic experiments, and ultimately towards the development of advanced quantum technologies. This study presents an overview of recent developments in the field of integrated waveguide quantum circuits. Key building blocks required for the realisation of quantum circuits are presented, and a rudimentary version of Shor's quantum factoring algorithm is demonstrated. Planar waveguide quantum circuits provide a high-performance platform from which quantum technologies and experimental quantum physics using single photons can be developed, and a new generation of quantum information and computing devices can be monolithically integrated onto a single optical chip.

Hussein Talib, P. Sewell, Ana Vuković +1 more

Abstract A design framework to implement non-unitary input–output operations to a practical unitary photonic integrated circuit is described. This is achieved by utilising the cosine-sine decomposition to recover the unitarity of the original operation. The recovered unitary operation is decomposed into fundamental unitary building blocks, forming a photonic integrated circuit network based on directional couplers and waveguide phase shifters. The individual building blocks are designed and optimised by three-dimensional full-wave simulations and scaled up using a circuit approach. The paper investigates the scalability and robustness of the design approach. Our study demonstrates that the proposed approach of performing unitary matrix completion can be applied to any arbitrary matrices. This design approach allows for implementation of non-unitary operations to perform various linear functions in neuromorphic photonics for computing, sensing, signal processing and communications.