Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99


Any time

2020 ( 4 )

2019 ( 322 )

2018 ( 469 )

2017 ( 465 )

Custom range...

Search Results: 1 - 10 of 286099 matches for " E. F. Galvao "
All listed articles are free for downloading (OA Articles)
Page 1 /286099
Display every page Item
Tripartite entanglement and quantum relative entropy
E. F. Galvao,M. B. Plenio,S. Virmani
Physics , 2000, DOI: 10.1088/0305-4470/33/48/316
Abstract: We establish relations between tripartite pure state entanglement and additivity properties of the bipartite relative entropy of entanglement. Our results pertain to the asymptotic limit of local manipulations on a large number of copies of the state. We show that additivity of the relative entropy would imply that there are at least two inequivalent types of asymptotic tripartite entanglement. The methods used include the application of some useful lemmas that enable us to analytically calculate the relative entropy for some classes of bipartite states.
Violation of the Universal Behavior of Membranes Inside Cylindrical Tubes at Nanoscale
E. Perim,A. F. Fonseca,N. M. Pugno,D. S. Galvao
Physics , 2014, DOI: 10.1209/0295-5075/105/56002
Abstract: Recently, it was proposed based on classical elasticity theory and experiments at macroscale, that the conformations of sheets inside cylindrical tubes present a universal behavior. A natural question is whether this behavior still holds at nanoscale. Based on molecular dynamics simulations and analytical modeling for graphene and boron nitride membranes confined inside carbon nanotubes, we show that the class of universality observed at macroscale is violated at nanoscale. The precise origins of these discrepancies is addressed and proven to be related to both surface and atomistic effects.
Molecular Recognition Effects in the Surface Diffusion of Large Organic Molecules: The Case of Violet Lander
F. Sato,S. B. Legoas,R. Otero,F. Hummelink,P. Thostrup,E. Laegsgaard,I. Stensgaard,F. Besenbacher,D. S. Galvao
Physics , 2007, DOI: 10.1038/nmat1243
Abstract: Violet Lander (VL) (C108H104) is a large organic molecule that when deposited on Cu (110) exhibited lock-and-key like behavior (Otero et al., Nature Mater. 3, 779 (2004)). In this work we report on a detailed fully atomistic molecular dynamics study of this phenomenon. Our results show that it has its physical basis in the interplay of the molecular hydrogens and the Cu(110) atomic spacing, which is a direct consequence of an accidental commensurability between molecule and surface dimensions. This knowledge could be used to engineer new molecules capable of displaying lock-and-key behavior with new potential applications in nanotechology.
Economical ontological models for discrete quantum systems
Ernesto F. Galvao
Physics , 2009, DOI: 10.1103/PhysRevA.80.022106
Abstract: I use the recently proposed framework of ontological models [Harrigan et al., arXiv:0709.1149v2] to obtain economical models for results of tomographically complete sets of measurements on finite-dimensional quantum systems. I describe a procedure that simplifies the models by decreasing the number of necessary ontic states, and present an explicit model with just 33 ontic states for a qutrit.
Discrete Wigner functions and quantum computational speedup
Ernesto F. Galvao
Physics , 2004, DOI: 10.1103/PhysRevA.71.042302
Abstract: In [Phys. Rev. A 70, 062101 (2004)] Gibbons et al. defined a class of discrete Wigner functions W to represent quantum states in a finite Hilbert space dimension d. I characterize a set C_d of states having non-negative W simultaneously in all definitions of W in this class. For d<6 I show C_d is the convex hull of stabilizer states. This supports the conjecture that negativity of W is necessary for exponential speedup in pure-state quantum computation.
Foundations of quantum theory and quantum information applications
Ernesto F. Galvao
Physics , 2002,
Abstract: This thesis establishes a number of connections between foundational issues in quantum theory, and some quantum information applications. It starts with a review of quantum contextuality and non-locality, multipartite entanglement characterisation, and of a few quantum information protocols. Quantum non-locality and contextuality are shown to be essential for different implementations of quantum information protocols known as quantum random access codes and quantum communication complexity protocols. I derive sufficient experimental conditions for tests of these quantum properties. I also discuss how the distribution of quantum information through quantum cloning processes can be useful in quantum computing. Regarding entanglement characterisation, some results are obtained relating two problems, that of additivity of the relative entropy of entanglement, and that of identifying different types of tripartite entanglement in the asymptotic regime of manipulations of many copies of a given state. The thesis ends with a description of an information processing task in which a single qubit substitutes for an arbitrarily large amount of classical communication. This result is interpreted in different ways: as a gap between quantum and classical computation space complexity; as a bound on the amount of classical communication necessary to simulate entanglement; and as a basic result on hidden-variable theories for quantum mechanics. I also show that the advantage of quantum over classical communication can be established in a feasible experiment.
A feasible quantum communication complexity protocol
Ernesto F. Galvao
Physics , 2001, DOI: 10.1103/PhysRevA.65.012318
Abstract: I show that a simple multi-party communication task can be performed more efficiently with quantum communication than with classical communication, even with low detection efficiency $\eta$. The task is a communication complexity problem in which distant parties need to compute a function of the distributed inputs, while minimizing the amount of communication between them. A realistic quantum optical setup is suggested that can demonstrate a five-party quantum protocol with higher-than-classical performance, provided $\eta>0.33$ .
Experimental requirements for quantum communication complexity protocols
Ernesto F. Galvao
Physics , 2000,
Abstract: I present a simple two-party quantum communication complexity protocol with higher success rate than the best possible classical protocol for the same task. The quantum protocol is shown to be equivalent to a quantum non-locality test, except that it is not necessary to close the locality loophole. I derive bounds for the detector efficiency and background count rates necessary for an experimental implementation and show that they are close to what can be currently achieved using ion trap technology. I also analyze the requirements for a three-party protocol and show that they are less demanding than those for the two-party protocol. The results can be interpreted as sufficient experimental conditions for quantum non-locality tests using two or three entangled qubits.
General rules for bosonic bunching in multimode interferometers
N. Spagnolo,C. Vitelli,L. Sansoni,E. Maiorino,P. Mataloni,F. Sciarrino,D. J. Brod,E. F. Galvao,A. Crespi,R. Ramponi,R. Osellame
Physics , 2013, DOI: 10.1103/PhysRevLett.111.130503
Abstract: We perform a comprehensive set of experiments that characterize bosonic bunching of up to 3 photons in interferometers of up to 16 modes. Our experiments verify two rules that govern bosonic bunching. The first rule, obtained recently in [1,2], predicts the average behavior of the bunching probability and is known as the bosonic birthday paradox. The second rule is new, and establishes a n!-factor quantum enhancement for the probability that all n bosons bunch in a single output mode, with respect to the case of distinguishable bosons. Besides its fundamental importance in phenomena such as Bose-Einstein condensation, bosonic bunching can be exploited in applications such as linear optical quantum computing and quantum-enhanced metrology.
Experimental boson sampling in arbitrary integrated photonic circuits
A. Crespi,R. Osellame,R. Ramponi,D. J. Brod,E. F. Galvao,N. Spagnolo,C. Vitelli,E. Maiorino,P. Mataloni,F. Sciarrino
Physics , 2012, DOI: 10.1038/nphoton.2013.112
Abstract: Photons naturally solve the BosonSampling problem: sample the outputs of a multi-photon experiment in a linear-optical interferometer. This is strongly believed to be hard to do on a classical computer, and motivates the development of technologies that enable precise control of multi-photon interference in large interferometers. Here we report multi-photon experiments in a 5-mode integrated interferometer. We use novel three-dimensional manufacturing techniques to achieve simultaneous control of 25 independent parameters that describe an arbitrary interferometer. We characterize the chip using one- and two-photon experiments, and confirm the quantum mechanical predictions for three-photon interference. Scaled up versions of this setup are the most promising way to demonstrate the computational capability of quantum systems, and may have applications in high-precision measurements and quantum communication.
Page 1 /286099
Display every page Item

Copyright © 2008-2017 Open Access Library. All rights reserved.