Southwest Quantum Information and Technology

Thirteenth Annual Meeting, February 17-20, 2011
Boulder, Colorado

Full Program | Thursday | Friday | Saturday | Sunday | All Sessions

SESSION 10c: Breakout C -- Entanglement and Superpositions
Session Chair:
4:00pm-4:30pm	Miguel-Angel Garcia-March, Colorado School of Mines
	Ultracold bosons in 3D double wells: macroscopic superposition of vortex states and the tunneling of atoms carrying vorticity
	Abstract. M.A. Garcia-March and L.D. Carr We study ultracold bosons in three-dimensional double wells when they are allowed either to condense in single-particle ground states or to occupy excited states. This permits the consideration of angular degrees of freedom on the model, since the second level eigenstates can carry angular momentum. We show that the number of relevant parameters is increased, since new processes, like two-particle hopping between different levels or vortex-antivortex pair creation or annihilation, are considered. We clearly demarcate the new range of dynamical regimes obtained in terms of the new parameters. We show the presence, in the interaction-dominated regimes, of macroscopic superposition states of atoms with non-zero angular momentum. This leads to the study of the dynamics of atoms carrying vorticity while tunneling between wells. Among these new tunneling processes, we find vortex hopping and vortex-antivortex pair superposition along with the sloshing of atoms between both wells.
4:30pm-5:00pm	Jess Riedel, Los Alamos National Laboratory
	Quantum Darwinism in an Everyday Environment: Huge Redundancy in Scattered Photons
	Abstract. We study quantum Darwinism---the redundant recording of information about the preferred states of a decohering system by its environment---for an object illuminated by a blackbody. In the cases of point-source, small disk, and isotropic illumination, we calculate the quantum mutual information between the object and its photon environment. We demonstrate that this realistic model exhibits fast and extensive proliferation of information about the object into the environment and results in redundancies orders of magnitude larger than the exactly soluble models considered to date. We also demonstrate a reduced ability to create records as initial environmental mixedness increases, in agreement with previous studies.
5:00pm-5:30pm	Peter Love, Haverford College
	Convex Roof Optimization from Cartan Decompositions
	Abstract. Extension of pure state entanglement measures to mixed states requires optimization over the set of ensembles that realize the density matrix. As discovered independently by Schroedinger, Jaynes and Hughston, Josza and Wooters, all ensembles may be realized by a unitary transformation of an initial ensemble. Hence the convex roof extension of pure state entanglement may be phrased as a problem of optimization on the unitary group. Prior work on this problem has used an Euler-Hurwitz parameterization of the unitary group. In this work, we describe the use of a parameterization based on a pair of Cartan decompositions previously developed in the context of the quantum Shannon decomposition.
5:30pm-6:00pm	Gilad Gour, Institute for Quantum Information Science, University of Calgary
	Multipartite Entanglement: Classification, Quantification, Manipulation, Evolution and Applications
	Abstract. Exotic multipartite entangled states plays an important role in a variety of quantum information processing tasks such as conventional and measurement-based quantum computation, quantum error correction schemes, quantum secret sharing, quantum simulations, and in principle in the description of every composite system consisting of more than one subsystem. The amount of information needed to describe N-party quantum system grows exponentially with N, which makes it very difficult and almost impossible to classify multipartite entangled states. In this talk I will show that a new formalism based on the stabilizer group of a given multipartite state, not only makes it possible to classify and quantify the amount of entanglement in multipartite states, but also describes fully the manipulation of multipartite entanglement under separable operations. In particular, I will introduce necessary and sufficient conditions to transform one pure multipartite state to another multipartite state via separable operations. In addition, I will discuss the evolution of multipartite entanglement under noise and decoherence, and its quantification in terms of SL-invariant polynomials. I will end with few applications to quantum secret sharing. Some of the work presented here is based on a joint work with Nolan Wallach.