ECE PhD Prospectus Defense: Shuto Osawa

Directionally-Unbiased Linear-Optical Multiport: Experiment and Applications

Shuto Osawa ECE PhD Student

Advisor:Alexander Sergienko

Committee:Roberto Paiella, Milos Popovic, Luca Dal Negro

Abstract: Beam splitters are one of the main building blocks in optical quantum information processing. Traditionally, beam splitters are used in a feed-forward configurations that reflects their natural directionalbias meaning a photon cannot leave the scattering element through the entrance port. However, this directional-bias constraint can be circumvented by designing new linear-optical configurations by placing mirrors in addition to the beam splitter. This directionality removal restores a full symmetry in the scattering element and allows the input photon to leave the system from the input port. Such systems can be used as a unitary coin operator, enabling execution of quantum walks on rather complex optical graph networks with great savings in hardware resources when compared with existing approaches utilizing directionally-biased devices. The directionally-unbiased configuration can be realized in different optical systems. Analysis of some originally directional optical devices and principles of their conversion into directionally-unbiased systems form the foundation of this project. Several quantum walk procedures executed on the graph network constructed using directionally-unbiased nodes, targeting quantum Hamiltonian simulation, and quantum search tasks are discussed. A significant saving in hardware and other required resources when compared with traditional directionally-biased beam-splitter-based optical networks is demonstrated.