Frontiers of quantum physics

Abstract:

Natural particle-number entanglement resides between spatial modes in coherent ultracold atomic gases. However, operations on the modes are restricted by a superselection rule that forbids coherent superpositions of different particle numbers. This would seemingly prevent mode entanglement from being used as a resource for quantum communication. Here I demonstrate that mode entanglement of a single massive particle can be used for dense coding despite the superselection rule if both parties share a coherent reservoir. © 2011 American Institute of Physics.

Abstract:

We give a pedagogical introduction to quantum discord and discuss the problem of separation of total correlations in a given quantum state into entanglement, dissonance, and classical correlations using the concept of relative entropy. This allows us to put all correlations on an equal footing. Entanglement and dissonance jointly belong to what is known as quantum discord. Our methods are completely applicable for multipartite systems of arbitrary dimensions. We finally show, using relative entropy, how different notions of quantum correlations are related to each other. This gives a single theory that incorporates all correlations, quantum and classical, and different methods of quantifying them. © 2011 American Institute of Physics.