Emergence of dark solitons in the course of measurements of particle positions in the Lieb-Liniger model: detailed analysis

TL;DR

This paper analyzes the Lieb-Liniger model to explore how dark solitons emerge during particle position measurements, linking hole excitations to soliton profiles through analytical solutions and numerical simulations.

Contribution

It provides a detailed analytical and numerical study connecting hole excitations with dark solitons in the Lieb-Liniger model, highlighting measurement-induced symmetry breaking.

Findings

Measurement of particle positions reveals dark soliton profiles in type II eigenstates.

Successive measurements break translation symmetry, exposing soliton structures.

Dark solitons are observed in both weak and strong interaction regimes.

Abstract

The thesis contains description of the Lieb-Liniger model in the context of the correspondence between dark solitons and the so-called hole excitations. We present a detailed analysis of the analytical solution given by the Bethe ansatz and discuss two types of elementary - particle (type I) and hole (type II) - excitations. It turns out that the type I excitations are reproduced by the Bogoliubov spectrum which means that they correspond to the sound waves in the system. It is believed that the eigenstates corresponding to the second branch are strictly connected with dark solitons. The main evidence bases on the comparison between the spectrum of the hole excitations and the dispersion relation of the semi-classical soliton. All the knowledge needed to fully understand the problem is presented in details in the thesis. Our numerical simulations show that successive measurement of particle positions is able to break the translation symmetry of the system and reveal particle densities expected from the dark soliton profiles if the system is prepared in a type II eigenstate. We analyze single and double dark solitons in weak and strong interaction regime.