Euclidean volume ratios characterizing the typicality of entangled and separable states are investigated for two-qubit and qubit-qutrit quantum states. For this purpose a new numerical approach is developed. It is based on the Peres-Horodecki criteri
on, on a characterization of the convex set of quantum states by inequalities resulting from Newton identities and Descartes rule of signs and on combining this characterization with standard and Multiphase Monte Carlo algorithms. Our approach confirms not only recent results on two-qubit states but also allows for a numerically reliable numerical treatment of so far unexplored special classes of two-qubit and qubit-qutrit states. However, our results also hint at the limits of efficiency of our numerical Monte Carlo approaches which is already marked by the most general qubit-qutrit states forming a convex set in a linear manifold of thirtyfive dimensions.
Debugging is famously one the hardest parts in programming. In this paper, we tackle the question: what does a debugging environment look like when we take interactive visualization as a central design principle? We introduce Anteater, an interactive
visualization system for tracing and exploring the execution of Python programs. Existing systems often have visualization components built on top of an existing infrastructure. In contrast, Anteaters organization of trace data enables an intermediate representation which can be leveraged to automatically synthesize a variety of visualizations and interactions. These interactive visualizations help with tasks such as discovering important structures in the execution and understanding and debugging unexpected behaviors. To assess the utility of Anteater, we conducted a participant study where programmers completed tasks on their own python programs using Anteater. Finally, we discuss limitations and where further research is needed.
Protocols for probabilistic entanglement-assisted quantum teleportation and for entanglement swapping of material qubits are presented. They are based on a protocol for postselective Bell-state projection which is capable of projecting two material q
ubits onto a Bell state with the help of ancillary coherent multiphoton states and postselection by balanced homodyne photodetection. Provided this photonic postselection is successful we explore the theoretical possibilities of realizing unit fidelity quantum teleportation and entanglement swapping with $25%$ success probability. This photon-assisted Bell projection is generated by coupling almost resonantly the two material qubits to single modes of the radiation field in two separate cavities in a Ramsey-type interaction sequence and by measuring the emerged field states in a balanced homodyne detection scenario. As these quantum protocols require basic tools of quantum state engineering of coherent multiphoton states and balanced homodyne photodetection they may offer interesting perspectives in particular for current quantum optical applications in quantum information processing.
We present new low-resolution HI spectral line imaging, obtained with the Karl G. Jansky Very Large Array (JVLA), of the star-forming Magellanic irregular galaxy UGCA 105. This nearby (D = 3.39+/-0.25 Mpc), low mass [M_HI=(4.3+/-0.5)x10^8 Solar masse
s] system harbors a large neutral gas disk (HI radius ~7.2 kpc at the N_HI=10^20 cm^-2 level) that is roughly twice as large as the stellar disk at the B-band R_25 isophote. We explore the neutral gas dynamics of this system, fitting tilted ring models in order to extract a well-sampled rotation curve. The rotation velocity rises in the inner disk, flattens at 72+/-3 km/s, and remains flat to the last measured point of the disk (~7.5 kpc). The dynamical mass of UGCA 105 at this outermost point, (9+/-2)x10^9 Solar masses, is ~10 times as large as the luminous baryonic components (neutral atomic gas and stars). The proximity and favorable inclination (55 degrees) of UGCA 105 make it a promising target for high-resolution studies of both star formation and rotational dynamics in a nearby low-mass galaxy.
In this contribution we present recent progress in the computation of next-to-leading order (NLO) QCD corrections for the production of an electroweak vector boson in association with jets at hadron colliders. We focus on results obtained using the v
irtual matrix element library BLACKHAT in conjunction with SHERPA, focusing on results relevant to understanding the background to top production.
We review recent NLO QCD results for W,Z + 3-jet production at hadron colliders, computed using BlackHat and SHERPA. We also include some new results for Z + 3-jet production at the LHC at 7 TeV. We report new progress towards the NLO cross section f
or W + 4-jet production. In particular, we show that the virtual matrix elements produced by BlackHat are numerically stable. We also show that with an improved integrator and tree-level matrix elements from BlackHat, SHERPA produces well-behaved real-emission contributions. As an illustration, we present the real-emission contributions -- including dipole-subtraction terms -- to the p_T distribution of the fourth jet, for a single subprocess with the maximum number of gluons.
Using BlackHat in conjunction with SHERPA, we have computed next-to-leading order QCD predictions for a variety of distributions in Z,gamma*+1,2,3-jet production at the Tevatron, where the Z boson or off-shell photon decays into an electron-positron
pair. We find good agreement between the NLO results for jet p_T distributions and measurements by CDF and D0. We also present jet-production ratios, or probabilities of finding one additional jet. As a function of vector-boson p_T, the ratios have distinctive features which we describe in terms of a simple model capturing leading logarithms and phase-space and parton-distribution-function suppression.
We have performed a theoretical study of electronic transport in single and bilayer graphene based on the standard linear-response (Kubo) formalism and continuum-model descriptions of the graphene band structure. We are focusing especially on the int
erband contribution to the optical conductivity. Analytical results are obtained for a variety of situations, which allow clear identification of features in the conductivity that are associated with relevant electronic energy scales. Our work extends previous numerical studies and elucidates ways to infer electronic properties of graphene samples from optical-conductivity measurements.
We have calculated the optical conductivity of a disorder-free single graphene sheet in the presence of spin-orbit coupling, using the Kubo formalism. Both intrinsic and structural-inversion-asymmetry induced types of spin splitting are considered wi
thin a low-energy continuum theory. Analytical results are obtained that allow us to identify distinct features arising from spin-orbit couplings. We point out how optical-conductivity measurements could offer a way to determine the strengths of spin splitting due to various origins in graphene.
We present an identity satisfied by the kinematic factors of diagrams describing the tree amplitudes of massless gauge theories. This identity is a kinematic analog of the Jacobi identity for color factors. Using this we find new relations between co
lor-ordered partial amplitudes. We discuss applications to multi-loop calculations via the unitarity method. In particular, we illustrate the relations between different contributions to a two-loop four-point QCD amplitude. We also use this identity to reorganize gravity tree amplitudes diagram by diagram, offering new insight into the structure of the KLT relations between gauge and gravity tree amplitudes. This can be used to obtain novel relations similar to the KLT ones. We expect this to be helpful in higher-loop studies of the ultraviolet properties of gravity theories.
