Talks

Entropy plays a fundamental role in quantum information theory through applications ranging from communication theory to condensed matter physics.  These applications include finding the best possible communication rates over noisy channels and characterizing ground state entanglement in strongly-correlated quantum systems.  In the latter, localized entanglement is often characterized by an area law for entropy.  Long-range entanglement, on the other hand, can give rise to topologically ordered materials whose collective excitations are robust against local noise.  In this talk, I will present a property of quantum entropy for multipartite quantum systems that resolves several open questions in quantum information theory about entanglement measures, provides new algorithmic opportunities and makes nontrivial statements about the structure of states with vanishing - but nonzero - topological entropy.  I will also comment how extensions of this work could help our understanding of quantum communication over certain very noisy channels.

Supersymmetry is a popular candidate for the 'model beyond the Standard Model', however minimal versions of it are quite constrained by the first year of data from the LHC. In this talk I will focus on supersymmetry scenarios where the gaugino masses are Dirac rather than Majorana. This seemingly innocuous change has a profound impact on collider bounds -- reducing the bound on (1st and 2nd generation) squark masses by nearly a factor of two. In addition, Dirac gaugino scenarios have amazing flavor properties, smoking gun LHC signals, and cosmological implications.

This talk presents two results on the interplay between causality and quantum information flow. First I will discuss about the task of switching the connections among quantum gates in a network. In ordinary quantum circuits, gates are connected in a fixed causal sequence.  However, we can imagine a physical mechanism where the connections among gates are not fixed, but instead are controlled by the quantum state of a control system. Such a "quantum switch" mechanism is consistent with quantum theory but cannot be described with in the standard model of causally ordered circuits, where it would be equivalent to a deterministic time travel and hence would violate the causality principle. With respect to the standard circuit model, the quantum switch is a new primitive that enables new information-processing protocols, such as the perfect discrimination between two classes of channels that are not perfectly distinguishable in a single query by any ordinary quantum circuit. Second, I will discuss about the probabilistic simulation of impossible channels that take an input in the future and produce an output in the past. In this case, I will show that the maximum probability of success in such a simulation is determined by causality and is inversely proportional to the amount of information that the channel can transmit.

Observing lepton-number violating processes is a decisive step toward establishing the Majorana nature of the neutrino mass. We explore the prospects searching for Delta L = 2 processes and propose the tests for the three types of the Seesaw mechanisms. Potential signals at the LHC
are studied and correlations to the neutrino oscillation parameters are investigated.

Recent progress in massive gravity has made it possible to construct consistent theories of interacting spin-2 fields.  In this talk I'll describe these developments, focusing on the resolution of the Boulware-Deser ghost problem and the promotion of massive gravity to a bimetric theory of gravity with two dynamical, interacting spin-2 fields.  I'll then discuss the generalization of these bimetric theories to theories of multiple interacting spin-2 fields.

Quantum corrections to three-point functions of scalar single trace operators in planar ${\cal N}=4$ Super-Yang-Mills theory are studied using integrability. At one loop, we find  new algebraic structures that not only govern all two loop corrections to the mixing of the operators but also automatically incorporate all one loop diagrams correcting the tree level Wick contractions. Speculations about possible extensions of our construction to all loop orders are given. We also match our results with the strong coupling predictions in the classical (Frolov-Tseytlin) limit.