Sania Jevtic, Matthew F. Pusey, David Jennings, Terry Rudolph
The quantum ellipsoid of a two qubit state is the set of Bloch vectors that Bob can collapse Alice's qubit to when he implements all possible measurements on his qubit. We provide an elementary construction of the ellipsoid for arbitrary states, and explain how this geometric representation can be made faithful. The representation provides a range of new results, and uncovers new features, such as the existence of `incomplete steering' in separable states. We show that entanglement can be analysed in terms of three geometric features of the ellipsoid, and prove that a state is separable if and only if it obeys a `nested tetrahedron' condition. We provide a volume formula for the ellipsoid in terms of the state density matrix, which identifies exactly when steering is fully three dimensional, and identify this as a new feature of correlations, intermediate between discord and entanglement.
View original:
http://arxiv.org/abs/1303.4724
No comments:
Post a Comment