Annotation evolution: how Web 2.0 technologies are enabling a change in annotation practice

Are Web 2.0 tools and technologies changing how and why scholars annotate their research sources? We begin to answer this question by assessing current technology and tools that support new functions for one of the most common scholarly research activity: taking notes. The results suggest a new approach to personalized information retrieval.published or submitted for publicationis peer reviewe

Mixed-state certification of quantum capacities for noisy communication channels

We extend a recent method to detect lower bounds to the quantum capacity of quantum communication channels by considering realistic scenarios with general input probe states and arbitrary detection procedures at the output. Realistic certification relies on a new bound for the coherent information of a quantum channel that can be applied with arbitrary bipartite mixed input states and generalized output measurements.Comment: 7 pages, 2 figure

Equivalence between squeezed-state and twin-beam communication channels

We show the equivalence between two different communication schemes that employ a couple of modes of the electromagnetic field. One scheme uses unconventional heterodyne detection, with correlated signal and image-band modes in a twin-beam state from parametric downconversion. The other scheme is realized through a complex-number coding over quadrature-squeezed states of two uncorrelated modes, each detected by ordinary homodyning. This equivalence concerns all the stages of the communication channel: the encoded state, the optimal amplifier for the channel, the master equation modeling the loss, and the output measurement scheme. The unitary transformation that connects the two communication schemes is realized by a frequency conversion device.Comment: 15 pages. Two latex figures included. To appear on Modern Phys. Lett.

Detection of properties and capacities of quantum channels

We review in a unified way a recently proposed method to detect properties of unknown quantum channels and lower bounds to quantum capacities, without resorting to full quantum process tomography. The method is based on the preparation of a fixed bipartite entangled state at the channel input or, equivalently, an ensemble of an overcomplete set of single-system states, along with few local measurements at the channel output.Comment: 8 pages, 1 figure. arXiv admin note: text overlap with arXiv:1510.0021