Quantum interference, complementarity and entanglement

by Tsegaye, Tedros

Abstract (Summary)
A fundamental entity in quantum mechanics is the quantum mechanical state. The only connection between the theory of quantum mechanics and our observable world is provided by state measurements, and in this interference between quantum states plays a key role. Recent interference experiments probing the world of quantum mechanics have started to resolve paradoxes and give new insights. While the classical concepts of phase and polarization are well established, the understanding of their quantum mechanical counterparts is not complete. While examining those concepts the increased understanding of quantum interference give risetonew applications: In quantum cryptography, secure (protected by the laws of physics) secret quantum key distribution has been set-up between places tens of kilometers apart. Quantum computers can be viewed as complex quantum interferometers. This emerging technique anticipates the construction of a new class of computers that can process data (superposition states) in parallel. Certain algorithms exist that can solve problems that groves exponentially for classical computers on a much faster polynomial growing time using quantum computers. The thesis is focused on the generation and detection of some non-classical few-photon states, and in particular on entangled states. A common aspect between the experiments of the thesis is the use of quantum interference. In paper A, the complementary wave-particle duality of light is examined. Paper B, C and D implements relative phase and polarization rotation experiments based on analogous theories. Using two photons, three orthogonal states of the relative phase operator and the polarization rotation operator can be generated. The techniques give a linear increase of the sensitivity of relative phase shifts and polarization rotations with the number of available photons. The sensitivity of classical measurement techniques are limited to the square of the number of available photons. Paper E uses the complementary wave-particle duality of light inaninterference experiment. The technique called interaction free measurements enables (at least in principle) the perfect detection of an absorbing object without the object absorbing any photon. Our method is based on the principle that a Fabry Perot interferometer tuned to resonance transmits an impinging photon. In contrast, when placing an object between the mirrors of the Fabry Perot Interferometer, the impinging photon will be re ected from the rst mirror. This technique using quantum objects could be used to produce entangled multi-photon states that can be used to improve the schemes of papers A, B, C, and D by going to an higher manifold (using a higher number of photons). v vi Preface This thesis is divided into three parts. Part I contains of ve chapters that introduce the reader into the aspects of quantum optics considered in the original work. There are no new results in these chapters. Instead, I have written these chapters to give anintuitive and simpli ed background of the research areain order to give anintroduction to the original work. Most of the contents could be refereed to as \common knowledge " in the quantum optics community, and other parts come from the cited sources. In Part II I give a review of the new theory and the experimental setups that are presented in the thesis. The relationship between the various experiments is also shown in greater detail. Part III contains two chapters. In chapter 9, a summary of the each paper in the original work is provided, including a description of my own contribution. The focus has been put on the scienti c relevance of the results and on the relation to the work of other groups. Finally conclusions of the work are drawn in chapter 10. The scienti c news, that is, my contribution, through my thesiswork to the scienti c progress, is found in the original work. The reprinted papers are found at the end of the thesis. vii viii
Bibliographical Information:


School:Kungliga Tekniska högskolan

School Location:Sweden

Source Type:Doctoral Dissertation



Date of Publication:01/01/2000

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