The first examples of Bohmian trajectories for photons have been worked out for simple situations, using the Kemmer-Duffin-Harishchandra formalism.Comment: 7 pages, Latex, Comments about time-like properties of Bohmian velocities added. Revised version accepted for publication in Physics Letters

The emerging field of entanglement or nonseparability in classical optics is reviewed, and its similarities with and differences from quantum entanglement clearly pointed out through a recapitulation of Hilbert spaces in general, the special restrictions on Hilbert spaces imposed in quantum mechanics and the role of Hilbert spaces in classical polarization optics. The production of Bell-like states in classical polarization optics is discussed, and new theorems are proved to discriminate between separable and nonseparable states in classical wave optics where no discreteness is involved. The influence of the Pancharatnam phase on a classical Bell-like state is deived. Finally, to what extent classical polarization optics can be used to simulate quantum information processing tasks is also discussed. This should be of great practical importance because coherence and entanglement are robust in classical optics but not in quantum systems.

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Technological advances have made it possible to perform experiments, once considered to be purely gedanken, which test the counterintuitive and bizarre consequences of quantum theory. This book provides simple accounts of these experiments and an understanding of what they aim to prove and why this is important. After introducing the main theoretical concepts and problems with the foundations of quantum mechanics, early chapters discuss experiments in the areas of wave-particle duality, cavity quantum electrodynamics and quantum non-demolition measurement. The text then examines investigation of certain predictions including the Aharanov-Bohm effect, before tackling the problem of macroscopic quantum coherence. Later chapters consider methods of testing the quantum Zeno paradox, collapse, macroscopic quantum jumps, tunnelling times and Einstein-Bell non-locality. Introductions to the theory behind types of measuring devices such as micromasers and those based on the concept of quantum non-demolition are also given. Detailed references are included.