Tests of fundamental quantum mechanics in continuous variable systems

Abstract

Finding the boundary between quantum and classical domains is very much an open question that is fundamental to a great deal of research spanning across many physics communities. The division is not clear cut and a deeper understanding is necessary for the future generation and engineering of quantum devices. In this thesis we introduce and apply a variety of tests that will reveal non classicality in real physical systems. The systems that we consider in many instances can be deemed classical and so our study is well motivated by the endeavor to explain the quantum to classical transition. We investigate three main classes of nonclassicality tests: Bell non locality, Kochen-Specker quantum contextuality and violation of Leggett-Garg macrorealism. These tests are applied to specific continuous variable systems that live in infinite dimensional Hilbert spaces and represent various states of the electromagnetic field. Firstly we test non locality in multimode versions of the thermal state. We show numerous violations of relevant Bell inequalities under quite unfavorable conditions and include state generation schemes. We then demonstrate through the violation of a Kochen-Specker inequality the state-independent quantum contextuality of a range of continuous variable states. These states include variations of entangled coherent states, a two-mode squeezed state and states represented by a generalized quasi-probability function. In what follows in the thesis we study non-locality of the nonclassical state of a system consisting of a qubit and an oscillator exposed to the effects of non-Markovian evolutions. Here we show interesting features related to the various facets with which non-Markovianity manifests itself. Finally this work tests macroscopic realism of a coherent and thermal state. We successively show violation of a Leggett-Garg inequality for a range of coherent state amplitude and degree of thermal mixedness.EThOS - Electronic Theses Online ServiceGBUnited Kingdo