Final PhD Oral Examination (Thesis Title: “Quantum Mechanics of Composite Objects with Internal Entanglement”)

Event Date and Time: 
Wed, 2017-08-09 12:30 - 15:30
Henn 318
Local Contact: 
Physics and Astronomy, UBC
Intended Audience: 

Although many quantum mechanics problems of a point particle have been well understood, the realistic physical model is often a composite object consisting of particles bound together, and its quantum mechanics is an important problem with applications in many areas of physics. Unlike a point particle, a composite object possesses internal structure described by some degrees of freedom which are often entangled with each other. We call the entanglement among these degrees of freedom “internal entanglement”, to distinguish it from any other entanglement they may share with an external object. Examples of internal entanglement include the entanglement be- tween a vibrational and a rotational mode of a molecule, and that between its position and its internal clock-state etc.
In this thesis, we study quantum mechanics of composite objects by fo- cusing on the effects of internal entanglement. We first look at the tunnelling of a diatomic molecule through a half-silvered mirror in continuum space and observe that the spatial superposition state of the diatomic molecule made by the mirror can decohere by emission of radiation due to the fact that its internal degrees of freedom are entangled with radiation fields, and that there exists entanglement between its position and its internal (i.e., relative position) degrees of freedom. Secondly, we study its lattice analog in molecular crystals, namely we replace the diatomic molecule by a biexicton, and the mirror by an impurity. We find that discreteness of a lattice makes the wave vector of a biexicton and the relative distance between two excitons of it entangled with each other. We investigate how this inseparability affects the creation of the biexciton-impurity bound states and the entanglement dynamics. Finally we propose a possible application of our study of internal entanglement to the Anderson model of a composite quasiparticle.

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