Hannover 2013 – wissenschaftliches Programm

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Q: Fachverband Quantenoptik und Photonik

Q 68: Quantum information: Photons and nonclassical light II

Q 68.5: Vortrag

Freitag, 22. März 2013, 15:00–15:15, F 142

Quantification of nonclassicality — •Melanie Mraz, Jan Sperling, Werner Vogel, and Boris Hage — Universität Rostock, Institut für Physik, Rostock, Deutschland

At the beginning of the 20th century the discussion on physics beyond the classical regime started. This was the hour of birth of quantum physics and, with Einstein's description of the photoelectric effect, of quantum optics. Even the physicists had problems to understand nonclassical quantum phenomena, because of its non-intuitive properties. So, why further struggling?

Nonclassical states have an advantage over classical states for various applications. Only one example is the quantum teleportation which would be unthinkable without nonclassical states. Hence, it is of a fundamental interest to study properties of nonclassical quantum states. It is already possible to say if a state is nonclassical or not, but how can we decide how much nonclassicality is in our system?

We propose a degree of nonclassicality being a nonclassicality measure. It is determined by the decomposition of a quantum state into superpositions of coherent states. On the one hand, coherent states resembles the behavior of a classical harmonic oscillator most closely. On the other hand, the more quantum superpositions of coherent states are needed, the more quantum interferences arise. A method for such a decomposition of quantum states is presented and the degree of nonclassicality is determined for different states. We apply our method to typical nonclassical states, such as the compass state and the squeezed vacuum state.