J. I. Latorre

J. I. Latorre
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J. I. Latorre
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High Energy Physics - Phenomenology (26)
 
Quantum Physics (20)
 
High Energy Physics - Experiment (12)
 
High Energy Physics - Theory (12)
 
Physics - Statistical Mechanics (7)
 
Physics - Other (4)
 
Physics - Strongly Correlated Electrons (3)
 
Physics - Data Analysis; Statistics and Probability (3)
 
Physics - Computational Physics (2)
 
Mathematics - Number Theory (2)
 
Nuclear Theory (2)
 
Mathematics - Mathematical Physics (1)
 
Computer Science - Computational Complexity (1)
 
Mathematical Physics (1)
 
Physics - Mesoscopic Systems and Quantum Hall Effect (1)
 
Nuclear Experiment (1)
 
Physics - Superconductivity (1)
 
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Publications Authored By J. I. Latorre

The notion of compressed quantum computation is employed to simulate the Ising interaction of a 1D--chain consisting out of $n$ qubits using the universal IBM cloud quantum computer running on $\log(n)$ qubits. The external field parameter that controls the quantum phase transition of this model translates into particular settings of the quantum gates that generate the circuit. We measure the magnetization, which displays the quantum phase transition, on a two--qubit system, which simulates a four--qubit Ising chain, and show its agreement with the theoretical prediction within a certain error. Read More

Bell inequalities can be studied both as constraints in the space of probability distributions and as expectation values of multipartite operators. The latter approach is particularly useful when considering outcomes as eigenvalues of unitary operators. This brings the possibility of exploiting the complex structure of the coefficients in the Bell operators. Read More

Violation of Mermin inequalities is tested on the 5-qubit IBM quantum computer. For 3, 4 and 5 parties, quantum states that violate the corresponding Mermin inequalities are constructed using quantum circuits on superconducting qubits. Measurements on different basis are included as additional final gates in the circuits. Read More

One of the most fascinating challenges in the context of parton density function (PDF) is the determination of the best combined PDF uncertainty from individual PDF sets. Since 2014 multiple methodologies have been developed to achieve this goal. In this proceedings we first summarize the strategy adopted by the PDF4LHC15 recommendation and then, we discuss about a new approach to Monte Carlo PDF compression based on clustering through machine learning algorithms. Read More

Absolutely Maximally Entangled (AME) states are those multipartite quantum states that carry absolute maximum entanglement in all possible partitions. AME states are known to play a relevant role in multipartite teleportation, in quantum secret sharing and they provide the basis novel tensor networks related to holography. We present alternative constructions of AME states and show their link with combinatorial designs. Read More

We develop a methodology for the construction of a Hessian representation of Monte Carlo sets of parton distributions, based on the use of a subset of the Monte Carlo PDF replicas as an unbiased linear basis, and of a genetic algorithm for the determination of the optimal basis. We validate the methodology by first showing that it faithfully reproduces a native Monte Carlo PDF set (NNPDF3.0), and then, that if applied to Hessian PDF set (MMHT14) which was transformed into a Monte Carlo set, it gives back the starting PDFs with minimal information loss. Read More

The current PDF4LHC recommendation to estimate uncertainties due to parton distribution functions (PDFs) in theoretical predictions for LHC processes involves the combination of separate predictions computed using PDF sets from different groups, each of which comprises a relatively large number of either Hessian eigenvectors or Monte Carlo (MC) replicas. While many fixed-order and parton shower programs allow the evaluation of PDF uncertainties for a single PDF set at no additional CPU cost, this feature is not universal, and moreover the a posteriori combination of the predictions using at least three different PDF sets is still required. In this work, we present a strategy for the statistical combination of individual PDF sets, based on the MC representation of Hessian sets, followed by a compression algorithm for the reduction of the number of MC replicas. Read More

There exists a remarkable four-qutrit state that carries absolute maximal entanglement in all its partitions. Employing this state, we construct a tensor network that delivers a holographic many body state, the H-code, where the physical properties of the boundary determine those of the bulk. This H-code is made of an even superposition of states whose relative Hamming distances are exponentially large with the size of the boundary. Read More

We propose several designs to simulate quantum many-body systems in manifolds with a non-trivial topology. The key idea is to create a synthetic lattice combining real-space and internal degrees of freedom via a suitable use of induced hoppings. The simplest example is the conversion of an open spin-ladder into a closed spin-chain with arbitrary boundary conditions. Read More

We study optimal control of diffusions with slow and fast variables and address a question raised by practitioners: is it possible to first eliminate the fast variables before solving the optimal control problem and then use the optimal control computed from the reduced-order model to control the original, high-dimensional system? The strategy "first reduce, then optimize"--rather than "first optimize, then reduce"--is motivated by the fact that solving optimal control problems for high-dimensional multiscale systems is numerically challenging and often computationally prohibitive. We state sufficient and necessary conditions, under which the "first reduce, then control" strategy can be employed and discuss when it should be avoided. We further give numerical examples that illustrate the "first reduce, then optmize" approach and discuss possible pitfalls. Read More

Large series of prime numbers can be superposed on a single quantum register and then analyzed in full parallelism. The construction of this Prime state is efficient, as it hinges on the use of a quantum version of any efficient primality test. We show that the Prime state turns out to be very entangled as shown by the scaling properties of purity, Renyi entropy and von Neumann entropy. Read More

We consider a frustrated anti-ferromagnetic triangular lattice Hamiltonian and show that the properties of the manifold of its degenerated ground state are represented by a novel type of tensor networks. These tensor networks are not based on ancillary maximally entangled pairs, but rather on triangular W-like simplices. Anti-ferromagnetic triangular frustration is then related to ancillary W-states in contrast to ferromagnetic order which emerges from the contraction of GHZ-like triangular simplices. Read More

We present a brief non-technical introduction to the standing discussion on the relation between Quantum Mechanics and Determinism. Quantum Mechanics inherent randomness in the measurement process is sometimes presented as a door to explain free will. We argue against this interpretation. Read More

We propose a quantum circuit that creates a pure state corresponding to the quantum superposition of all prime numbers less than 2^n, where n is the number of qubits of the register. This Prime state can be built using Grover's algorithm, whose oracle is a quantum implementation of the classical Miller-Rabin primality test. The Prime state is highly entangled, and its entanglement measures encode number theoretical functions such as the distribution of twin primes or the Chebyshev bias. Read More

We develop a numerical algorithm for computing the effective drift and diffusivity of the steady-state behavior of an overdamped particle driven by a periodic potential whose amplitude is modulated in time by multiplicative noise and forced by additive Gaussian noise (the mathematical structure of a flashing Brownian motor). The numerical algorithm is based on a spectral decomposition of the solution to the Fokker-Planck equation with periodic boundary conditions and the cell problem which result from homogenization theory. We also show that the numerical method of Wang, Peskin, Elston (WPE, 2003) for computing said quantities is equivalent to that resulting from homogenization theory. Read More

In this paper we revisit the problem of Brownian motion in a tilted periodic potential. We use homogenization theory to derive general formulas for the effective velocity and the effective diffusion tensor that are valid for arbitrary tilts. Furthermore, we obtain power series expansions for the velocity and the diffusion coefficient as functions of the external forcing. Read More

We present the first determination of parton distributions of the nucleon at NLO and NNLO based on a global data set which includes LHC data: NNPDF2.3. Our data set includes, besides the deep inelastic, Drell-Yan, gauge boson production and jet data already used in previous global PDF determinations, all the relevant LHC data for which experimental systematic uncertainties are currently available: ATLAS and LHCb W and Z lepton rapidity distributions from the 2010 run, CMS W electron asymmetry data from the 2011 run, and ATLAS inclusive jet cross-sections from the 2010 run. Read More

We study the existence of absolutely maximally entangled (AME) states in quantum mechanics and its applications to quantum information. AME states are characterized by being maximally entangled for all bipartitions of the system and exhibit genuine multipartite entanglement. With such states, we present a novel parallel teleportation protocol which teleports multiple quantum states between groups of senders and receivers. Read More

We present a new strategy for contracting tensor networks in arbitrary geometries. This method is designed to follow as strictly as possible the renormalization group philosophy, by first contracting tensors in an exact way and, then, performing a controlled truncation of the resulting tensor. We benchmark this approximation procedure in two dimensions against an exact contraction. Read More

We present a general strategy to simulate a D+1-dimensional quantum system using a D-dimensional one. We analyze in detail a feasible implementation of our scheme using optical lattice technology. The simplest non-trivial realization of a fourth dimension corresponds to the creation of a bivolume geometry. Read More

We determine the strong coupling alpha_s at NNLO in perturbative QCD using the global dataset input to the NNPDF2.1 NNLO parton fit: data from neutral and charged current deep-inelastic scattering, Drell-Yan, vector boson production and inclusive jets. We find alpha_s(M_Z)=0. Read More

We discuss the statistical properties of parton distributions within the framework of the NNPDF methodology. We present various tests of statistical consistency, in particular that the distribution of results does not depend on the underlying parametrization and that it behaves according to Bayes' theorem upon the addition of new data. We then study the dependence of results on consistent or inconsistent datasets and present tools to assess the consistency of new data. Read More

We develop in more detail our reweighting method for incorporating new datasets in parton fits based on a Monte Carlo representation of PDFs. After revisiting the derivation of the reweighting formula, we show how to construct an unweighted PDF replica set which is statistically equivalent to a given reweighted set. We then use reweighting followed by unweighting to test the consistency of the method, specifically by verifying that results do not depend on the order in which new data are included in the fit via reweighting. Read More

We present a determination of the parton distributions of the nucleon from a global set of hard scattering data using the NNPDF methodology at LO and NNLO in perturbative QCD, thereby generalizing to these orders the NNPDF2.1 NLO parton set. Heavy quark masses are included using the so-called FONLL method, which is benchmarked here at NNLO. Read More

We construct a tensor network that delivers an unnormalized quantum state whose coefficients are the solutions to a given instance of 3SAT, an NP-complete problem. The tensor network contraction that corresponds to the norm of the state counts the number of solutions to the instance. It follows that exact contractions of this tensor network are in the #P-complete computational complexity class, thus believed to be a hard task. Read More

We determine the strong coupling alpha_s from a next-to-leading order analysis of processes used for the NNPDF2.1 parton determination, which includes data from neutral and charged current deep-inelastic scattering, Drell-Yan and inclusive jet production. We find alpha_s(M_Z)=0. Read More

We discuss the impact of the treatment of NMC structure function data on parton distributions in the context of the NNPDF2.1 global PDF determination at NLO and NNLO. We show that the way these data are treated, and even their complete removal, has no effect on parton distributions at NLO, and at NNLO has an effect which is below one sigma. Read More

We present a determination of the parton distributions of the nucleon from a global set of hard scattering data using the NNPDF methodology including heavy quark mass effects: NNPDF2.1. In comparison to the previous NNPDF2. Read More

This document is intended as a study of benchmark cross sections at the LHC (at 7 TeV) at NLO using modern parton distribution functions currently available from the 6 PDF fitting groups that have participated in this exercise. It also contains a succinct user guide to the computation of PDFs, uncertainties and correlations using available PDF sets. A companion note, also submitted to the archive, provides an interim summary of the current recommendations of the PDF4LHC working group for the use of parton distribution functions and of PDF uncertainties at the LHC, for cross section and cross section uncertainty calculations. Read More

We present a method for incorporating the information contained in new datasets into an existing set of parton distribution functions without the need for refitting. The method involves reweighting the ensemble of parton densities through the computation of the chi-square to the new dataset. We explain how reweighting may be used to assess the impact of any new data or pseudodata on parton densities and thus on their predictions. Read More

We argue that the Fermi-Hubbard Hamiltonian describing the physics of ultracold atoms on optical lattices in the presence of artificial non-Abelian gauge fields, is exactly equivalent to the gauge theory Hamiltonian describing Dirac fermions in the lattice. We show that it is possible to couple the Dirac fermions to an "artificial" gravitational field, i.e. Read More

We show that gauge transformations can be simulated on systems of ultracold atoms. We discuss observables that are invariant under these gauge transformations and compute them using a tensor network ansatz that escapes the phase problem. We determine that the Mott-insulator-to-superfluid critical point is monotonically shifted as the induced magnetic flux increases. Read More

We review recent progress towards a determination of a set of polarized parton distributions from a global set of deep-inelastic scattering data based on the NNPDF methodology, in analogy with the unpolarized case. This method is designed to provide a faithful and statistically sound representation of parton distributions and their uncertainties. We show how the FastKernel method provides a fast and accurate method for solving the polarized DGLAP equations. Read More

We discuss the implementation of the FONLL general-mass scheme for heavy quarks in deep-inelastic scattering in the FastKernel framework, used in the NNPDF series of global PDF analysis. We present the general features of FONLL and benchmark the accuracy of its implementation in FastKernel comparing with the Les Houches heavy quark benchmark tables. We then show preliminary results of the NNPDF2. Read More

We present predictions for relevant LHC observables obtained with the NNPDF2.0 set. We compute the combined PDFs uncertainties on these observables, and show that combining errors in quadrature yields an excellent approximation to exact error propagation. Read More

This report summarizes the activities of the SM and NLO Multileg Working Group of the Workshop "Physics at TeV Colliders", Les Houches, France 8-26 June, 2009. Read More

Entanglement entropy obeys area law scaling for typical physical quantum systems. This may naively be argued to follow from locality of interactions. We show that this is not the case by constructing an explicit simple spin chain Hamiltonian with nearest neighbor interactions that presents an entanglement volume scaling law. Read More

We present a determination of the parton distributions of the nucleon from a global set of hard scattering data using the NNPDF methodology: NNPDF2.0. Experimental data include deep-inelastic scattering with the combined HERA-I dataset, fixed target Drell-Yan production, collider weak boson production and inclusive jet production. Read More

We consider the generic problem of performing a global fit to many independent data sets each with a different overall multiplicative normalization uncertainty. We show that the methods in common use to treat multiplicative uncertainties lead to systematic biases. We develop a method which is unbiased, based on a self--consistent iterative procedure. Read More

It is shown that a simple modification of the geometry in which Raman lasers are applied to a cold gas in an optical lattice results in transforming the emerging effective electromagnetic field into a pure gauge. This contrived gauge-away effect can be observed experimentally by measuring the Mott-Insulator to Superfluid critical point. The underlying mechanism for this phenomenon is the ability to engineer the transfer of the transverse component of the gauge potential into its longitudinal one. Read More

We use recent neutrino dimuon production data combined with a global deep-inelastic parton fit to construct a new parton set, NNPDF1.2, which includes a determination of the strange and antistrange distributions of the nucleon. The result is characterized by a faithful estimation of uncertainties thanks to the use of the NNPDF methodology, and is free of model or theoretical assumptions other than the use of NLO perturbative QCD and exact sum rules. Read More

We review some of the recent progress on the study of entropy of entanglement in many-body quantum systems. Emphasis is placed on the scaling properties of entropy for one-dimensional multi-partite models at quantum phase transitions and, more generally, on the concept of area law. We also briefly describe the relation between entanglement and the presence of impurities, the idea of particle entanglement, the evolution of entanglement along renormalization group trajectories, the dynamical evolution of entanglement and the fate of entanglement along a quantum computation. Read More

2009Mar
Authors: H. Jung1, A. De Roeck2, Z. J. Ajaltouni3, S. Albino4, G. Altarelli5, F. Ambroglini6, J. Anderson7, G. Antchev8, M. Arneodo9, P. Aspell10, V. Avati11, M. Bahr12, A. Bacchetta13, M. G. Bagliesi14, R. D. Ball15, A. Banfi16, S. Baranov17, P. Bartalini18, J. Bartels19, F. Bechtel20, V. Berardi21, M. Berretti22, G. Beuf23, M. Biasini24, I. Bierenbaum25, J. Blumlein26, R. E. Blair27, C. Bombonati28, M. Boonekamp29, U. Bottigli30, S. Boutle31, M. Bozzo32, E. Brucken33, J. Bracinik34, A. Bruni35, G. E. Bruno36, A. Buckley37, A. Bunyatyan38, H. Burkhardt39, P. Bussey40, A. Buzzo41, M. Cacciari42, F. Cafagna43, M. Calicchio44, F. Caola45, M. G. Catanesi46, P. L. Catastini47, R. Cecchi48, F. A. Ceccopieri49, S. Cerci50, S. Chekanov51, R. Chierici52, M. Ciafaloni53, M. A. Ciocci54, V. Coco55, D. Colferai56, A. Cooper-Sarkar57, G. Corcella58, M. Czakon59, A. Dainese60, M. Dasgupta61, M. Deak62, M. Deile63, P. A. Delsart64, L. Del Debbio65, A. de Roeck66, C. Diaconu67, M. Diehl68, E. Dimovasili69, M. Dittmar70, I. M. Dremin71, K. Eggert72, R. Engel73, V. Eremin74, S. Erhan75, C. Ewerz76, L. Fano77, J. Feltesse78, G. Ferrera79, F. Ferro80, R. Field81, S. Forte82, F. Garcia83, A. Geiser84, F. Gelis85, S. Giani86, S. Gieseke87, M. A. Gigg88, A. Glazov89, K. Golec-Biernat90, K. Goulianos91, J. Grebenyuk92, V. Greco93, D. Grellscheid94, G. Grindhammer95, M. Grothe96, A. Guffanti97, C. Gwenlan98, V. Halyo99, K. Hamilton100, F. Hautmann101, J. Heino102, G. Heinrich103, T. Hilden104, K. Hiller105, J. Hollar106, X. Janssen107, S. Joseph108, A. W. Jung109, H. Jung110, V. Juranek, J. Kaspar, O. Kepka, V. A. Khoze, Ch. Kiesling, M. Klasen, S. Klein, B. A. Kniehl, A. Knutsson, J. Kopal, G. Kramer, F. Krauss, V. Kundrat, K. Kurvinen, K. Kutak, L. Lonnblad, S. Lami, G. Latino, J. I. Latorre, O. Latunde-Dada, R. Lauhakangas, V. Lendermann, P. Lenzi, G. Li, A. Likhoded, A. Lipatov, E. Lippmaa, M. Lokajicek, M. Lo Vetere, F. Lucas Rodriguez, G. Luisoni, E. Lytken, K. Muller, M. Macri, G. Magazzu, A. Majhi, S. Majhi, P. Marage, L. Marti, A. D. Martin, M. Meucci, D. A. Milstead, S. Minutoli, A. Nischke, A. Moares, S. Moch, L. Motyka, T. Namsoo, P. Newman, H. Niewiadomski, C. Nockles, E. Noschis, G. Notarnicola, J. Nystrand, E. Oliveri, F. Oljemark, K. Osterberg, R. Orava, M. Oriunno, S. Osman, S. Ostapchenko, P. Palazzi, E. Pedreschi, A. V. Pereira, H. Perrey, J. Petajajarvi, T. Petersen, A. Piccione, T. Pierog, J. L. Pinfold, O. I. Piskounova, S. Platzer, M. Quinto, Z. Rurikova, E. Radermacher, V. Radescu, E. Radicioni, F. Ravotti, G. Rella, P. Richardson, E. Robutti, G. Rodrigo, E. Rodrigues, M. Rogal, T. C. Rogers, J. Rojo, P. Roloff, L. Ropelewski, C. Rosemann, Ch. Royon, G. Ruggiero, A. Rummel, M. Ruspa, M. G. Ryskin, D. Salek, W. Slominski, H. Saarikko, A. Sabio Vera, T. Sako, G. P. Salam, V. A. Saleev, C. Sander, G. Sanguinetti, A. Santroni, Th. Schorner-Sadenius, R. Schicker, I. Schienbein, W. B. Schmidke, F. Schwennsen, A. Scribano, G. Sette, M. H. Seymour, A. Sherstnev, T. Sjostrand, W. Snoeys, G. Somogyi, L. Sonnenschein, G. Soyez, H. Spiesberger, F. Spinella, P. Squillacioti, A. M. Stasto, A. Starodumov, H. Stenzel, Ph. Stephens, A. Ster, D. Stocco, M. Strikman, C. Taylor, T. Teubner, R. S. Thorne, Z. Trocsanyi, M. Treccani, D. Treleani, L. Trentadue, A. Trummal, J. Tully, W. K. Tung, M. Turcato, N. Turini, M. Ubiali, A. Valkarova, A. van Hameren, P. Van Mechelen, J. A. M. Vermaseren, A. Vogt, B. F. L. Ward, G. Watt, B. R. Webber, Ch. Weiss, Ch. White, J. Whitmore, R. Wolf, J. Wu, A. Yagues-Molina, S. A. Yost, G. Zanderighi, N. Zotov, M. zur Nedden
Affiliations: 1DESY, U. Antwerp, 2CERN, U. Antwerp, 3DESY, U. Antwerp, 4DESY, U. Antwerp, 5DESY, U. Antwerp, 6DESY, U. Antwerp, 7DESY, U. Antwerp, 8DESY, U. Antwerp, 9DESY, U. Antwerp, 10DESY, U. Antwerp, 11DESY, U. Antwerp, 12DESY, U. Antwerp, 13DESY, U. Antwerp, 14DESY, U. Antwerp, 15DESY, U. Antwerp, 16DESY, U. Antwerp, 17DESY, U. Antwerp, 18DESY, U. Antwerp, 19DESY, U. Antwerp, 20DESY, U. Antwerp, 21DESY, U. Antwerp, 22DESY, U. Antwerp, 23DESY, U. Antwerp, 24DESY, U. Antwerp, 25DESY, U. Antwerp, 26DESY, U. Antwerp, 27DESY, U. Antwerp, 28DESY, U. Antwerp, 29DESY, U. Antwerp, 30DESY, U. Antwerp, 31DESY, U. Antwerp, 32DESY, U. Antwerp, 33DESY, U. Antwerp, 34DESY, U. Antwerp, 35DESY, U. Antwerp, 36DESY, U. Antwerp, 37DESY, U. Antwerp, 38DESY, U. Antwerp, 39DESY, U. Antwerp, 40DESY, U. Antwerp, 41DESY, U. Antwerp, 42DESY, U. Antwerp, 43DESY, U. Antwerp, 44DESY, U. Antwerp, 45DESY, U. Antwerp, 46DESY, U. Antwerp, 47DESY, U. Antwerp, 48DESY, U. Antwerp, 49DESY, U. Antwerp, 50DESY, U. Antwerp, 51DESY, U. Antwerp, 52DESY, U. Antwerp, 53DESY, U. Antwerp, 54DESY, U. Antwerp, 55DESY, U. Antwerp, 56DESY, U. Antwerp, 57DESY, U. Antwerp, 58DESY, U. Antwerp, 59DESY, U. Antwerp, 60DESY, U. Antwerp, 61DESY, U. Antwerp, 62DESY, U. Antwerp, 63DESY, U. Antwerp, 64DESY, U. Antwerp, 65DESY, U. Antwerp, 66DESY, U. Antwerp, 67DESY, U. Antwerp, 68DESY, U. Antwerp, 69DESY, U. Antwerp, 70DESY, U. Antwerp, 71DESY, U. Antwerp, 72DESY, U. Antwerp, 73DESY, U. Antwerp, 74DESY, U. Antwerp, 75DESY, U. Antwerp, 76DESY, U. Antwerp, 77DESY, U. Antwerp, 78DESY, U. Antwerp, 79DESY, U. Antwerp, 80DESY, U. Antwerp, 81DESY, U. Antwerp, 82DESY, U. Antwerp, 83DESY, U. Antwerp, 84DESY, U. Antwerp, 85DESY, U. Antwerp, 86DESY, U. Antwerp, 87DESY, U. Antwerp, 88DESY, U. Antwerp, 89DESY, U. Antwerp, 90DESY, U. Antwerp, 91DESY, U. Antwerp, 92DESY, U. Antwerp, 93DESY, U. Antwerp, 94DESY, U. Antwerp, 95DESY, U. Antwerp, 96DESY, U. Antwerp, 97DESY, U. Antwerp, 98DESY, U. Antwerp, 99DESY, U. Antwerp, 100DESY, U. Antwerp, 101DESY, U. Antwerp, 102DESY, U. Antwerp, 103DESY, U. Antwerp, 104DESY, U. Antwerp, 105DESY, U. Antwerp, 106DESY, U. Antwerp, 107DESY, U. Antwerp, 108DESY, U. Antwerp, 109DESY, U. Antwerp, 110DESY, U. Antwerp

2nd workshop on the implications of HERA for LHC physics. Working groups: Parton Density Functions Multi-jet final states and energy flows Heavy quarks (charm and beauty) Diffraction Cosmic Rays Monte Carlos and Tools Read More

We construct a quantum algorithm that creates the Laughlin state for an arbitrary number of particles $n$ in the case of filling fraction one. This quantum circuit is efficient since it only uses $n(n-1)/2$ local qudit gates and its depth scales as $2n-3$. We further prove the optimality of the circuit using permutation theory arguments and we compute exactly how entanglement develops along the action of each gate. Read More

We provide an assessment of the state of the art in various issues related to experimental measurements, phenomenological methods and theoretical results relevant for the determination of parton distribution functions (PDFs) and their uncertainties, with the specific aim of providing benchmarks of different existing approaches and results in view of their application to physics at the LHC. We discuss higher order corrections, we review and compare different approaches to small x resummation, and we assess the possible relevance of parton saturation in the determination of PDFS at HERA and its possible study in LHC processes. We provide various benchmarks of PDF fits, with the specific aim of studying issues of error propagation, non-gaussian uncertainties, choice of functional forms of PDFs, and combination of data from different experiments and different processes. Read More

We present some exact results for the optimal Matrix Product State (MPS) approximation to the ground state of the infinite isotropic Heisenberg spin-1/2 chain. Our approach is based on the systematic use of Schmidt decompositions to reduce the problem of approximating for the ground state of a spin chain to an analytical minimization. This allows to show that results of standard simulations, e. Read More

We present recent progress within the NNPDF parton analysis framework. After a brief review of the results from the DIS NNPDF analysis, NNPDF1.0, we discuss results from an updated analysis with independent parametrizations for the strange and anti-strange distributions, denoted by NNPDF1. Read More

We present the determination of a set of parton distributions of the nucleon, at next-to-leading order, from a global set of deep-inelastic scattering data: NNPDF1.0. The determination is based on a Monte Carlo approach, with neural networks used as unbiased interpolants. Read More

We present recent results of the NNPDF collaboration on a full DIS analysis of Parton Distribution Functions (PDFs). Our method is based on the idea of combining a Monte Carlo sampling of the probability measure in the space of PDFs with the use of neural networks as unbiased universal interpolating functions. The general structure of the project and the features of the fit are described and compared to those of the traditional approaches. Read More