[PhD Thesis Presentation_Zoom] - Ms. Ayaka Usui - "Control and measurement ofnon-classical properties of cold atomic and optical systems"

Presentater: Ms. Ayaka Usui

Supervisor: Prof. Thomas Busch

Zoom URL: https://oist.zoom.us/webinar/register/WN_f0jYCZSER0-Xq4zD8zCk-A

Title: Control and measurement ofnon-classical properties of cold atomic and optical systems

Abstract:

In this work I consider various systems from the area of ultracold quantum gases and quantum optics to reveal non-classical correlations and features. First, I investigate the presence of a dynamical phase transition in a system of cold atoms trapped in a one-dimensional optical lattices. To the best of my knowledge this has been the first work to study dynamical phase transitions in a continuous model, and it revealed the relation between the dynamical phase transition and temporal orthogonality. Second, I consider an impurity coupled to a gas in a two dimensional lattice. This work has revealed the dynamics of the impurity and proposed an approach to probe the local excitation spectrum of the gas at the site that is coupled to the impurity. Third, I study two strongly interacting bosons with synthetic spin-orbit coupling. This work discovers the ground state beyond the mean-field regime and explores non-classical correlations in the ground state. Fourth, I present my contribution to a project on Bayesian estimation with continuous-variable systems, which are realised with optical setups. I explore what is the best probe state for heterodyne or homodyne measurements to estimate any phase rotation. Finally, I consider qubit and higher dimensional machines interfacing with an environment and monitoring a target system. The behaviour of the target is too complicated in general to reveal the dynamics and even the steady state. I suggest to use a virtual qubit is a tool to predict the quantitative behaviour of the target qubit. For this I generalise the idea of the virtual qubit to higher-level target systems so that one can design autonomous quantum machines beyond a few qubits.