Particle Optics
In this chapter we focus on particle optics, i.e., atom optics, neutron optics, and non-ballistic electron optics. The recent literature is concerned mainly with atom optics due to the larger wealth of phenomena encountered in comparison to neutron or ele
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In this chapter we focus on particle optics, i.e., atom optics, neutron optics, and non-ballistic electron optics. The recent literature is concerned mainly with atom optics due to the larger wealth of phenomena encountered in comparison to neutron or electron optics. We therefore also dedicate a much greater space to atom optics. The interaction with the environment and the possibility of manipulating quantum particles depends on the particle type: neutrons are spin-1/2 particles, thus fermions, whereas atoms can be fermions or bosons, as in Bose-Einstein condensates, for example. Atom optics usually refers to neutral atoms, which interact in a quite different manner with matter compared to electrically charged electrons. In particular, atom interaction with static electromagnetic fields is much weaker. On the other hand atoms are easier to produce than neutrons. No particle accelerator or nuclear reactor is needed. Moreover, recent progress in the generation and manipulation of Bose-Einstein condensates has led not only to the development of intense and coherent atom beams that can be referred to as atom laser beams, but also to the development of atom optical components able to preserve this coherence [see for example Bloch et al. (2001)]. Particle optics refers in general to the manipulation of trajectories and to the exploitation of the wave properties of quantum particles. Several physical mechanisms have been used to this end: the strong interaction of electrons and neutrons with static electromagnetic fields, and the manipulation of atoms using light forces or microfabricated structures. The wave nature of massive particles was demonstrated experimentally a long time ago: the groundbreaking experiments of Davisson and Germer (1927) and Thomson (1927) for electrons and Estermann and Stern (1930) for atoms are included in almost any text book. Our aim in this chapter is not to review the progress made in the particle optics domain. There are plenty of review papers and books devoted to this subject. We are only interested in bringing out the mathematical similarities and physical differences that form the basis of the implementation in particle optics of classical optical concepts and devices. This is quite a challenging task since quantum particles behave as waves in quantum mechanics, whereas light is wavelike in classical physics. The center-
D. Dragoman et al., Quantum-Classical Analogies © Springer-Verlag Berlin Heidelberg 2004
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6 Particle Optics
of-mass motion of atoms, for example, can in many cases be described by classical mechanics, whereas photons are particle-like only in a quantum mechanical treatment of light. Moreover, in many atom optics experiments, the role of classical light and matter are interchanged, in the sense that light fields act as optical systems for beams of atoms. Both the ray and wave optical behavior of massive quantum particles will be tackled, in an attempt to illustrate the fact that the boundaries between waves and particles fade away in quantum mechanics. However,
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