TY - JOUR A1 - Ostermeyer, Martin A1 - Korn, Dietmar A1 - Puhlmann, Dirk A1 - Henkel, Carsten A1 - Eisert, Jens T1 - Two-dimensional characterization of spatially entangled photon pairs N2 - We characterize the entanglement in position and momentum of photon pairs generated in type-II parametric down- conversion. Coincidence maps of the photon positions in the near-field and far-field planes are observed in two transverse dimensions using scanning fiber probes. We estimate the covariance matrix of an effective two-mode system and apply criteria for entanglement based on covariance matrices to certify space-momentum entanglement. The role of higher- order spatial modes for observing spatial entanglement between the two photons is discussed. Y1 - 2009 UR - http://www.informaworld.com/openurl?genre=journal&issn=0950-0340 U6 - https://doi.org/10.1080/09500340903359962 SN - 0950-0340 ER - TY - JOUR A1 - Plenio, M. B. A1 - Hartley, J. A1 - Eisert, Jens T1 - Dynamics and manipulation of entanglement in coupled harmonic systems with many degrees of freedom N2 - We study the entanglement dynamics of a system consisting of a large number of coupled harmonic oscillators in various configurations and for different types of nearest-neighbour interactions. For a one-dimensional chain, we provide compact analytical solutions and approximations to the dynamical evolution of the entanglement between spatially separated oscillators. Key properties such as the speed of entanglement propagation, the maximum amount of transferred entanglement and the efficiency for the entanglement transfer are computed. For harmonic oscillators coupled by springs, corresponding to a phonon model, we observe a non-monotonic transfer efficiency in the initially prepared amount of entanglement, i.e. an intermediate amount of initial entanglement is transferred with the highest efficiency. In contrast, within the framework of the rotating-wave approximation (as appropriate, e.g. in quantum optical settings) one finds a monotonic behaviour. We also study geometrical configurations that are analogous to quantum optical devices (such as beamsplitters and interferometers) and observe characteristic differences when initially thermal or squeezed states are entering these devices. We show that these devices may be switched on and off by changing the properties of an individual oscillator. They may therefore be used as building blocks of large fixed and pre-fabricated but programmable structures in which quantum information is manipulated through propagation. We discuss briefly possible experimental realizations of systems of interacting harmonic oscillators in which these effects may be confirmed experimentally Y1 - 2004 SN - 1367-2630 ER - TY - JOUR A1 - Riera, Arnau A1 - Gogolin, Christian A1 - Eisert, Jens T1 - Thermalization in nature and on a quantum computer JF - Physical review letters N2 - In this work, we show how Gibbs or thermal states appear dynamically in closed quantum many-body systems, building on the program of dynamical typicality. We introduce a novel perturbation theorem for physically relevant weak system-bath couplings that is applicable even in the thermodynamic limit. We identify conditions under which thermalization happens and discuss the underlying physics. Based on these results, we also present a fully general quantum algorithm for preparing Gibbs states on a quantum computer with a certified runtime and error bound. This complements quantum Metropolis algorithms, which are expected to be efficient but have no known runtime estimates and only work for local Hamiltonians. Y1 - 2012 U6 - https://doi.org/10.1103/PhysRevLett.108.080402 SN - 0031-9007 VL - 108 IS - 8 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Räder, Andy A1 - Eisert, Jens A1 - Wilkens, Martin A1 - Schmidt, Robert A1 - Micka, Bettina A1 - Ostermeyer, Martin A1 - Zill, Rüdiger A1 - Baur, Jürgen A1 - Schmidt, Renate A1 - Leppin, Karin A1 - Slotowski, Agnes A1 - Resch-Esser, Ursula T1 - Portal = Albert Einsteins Erbe: Uni-Physiker forschen weiter BT - Die Potsdamer Universitätszeitung N2 - Aus dem Inhalt: - Albert Einsteins Erbe: Uni-Physiker forschen weiter - Uni-Studiengang im europäischen Exzellenzprogramm - Sternenstaubsammler - Mit Einfallsreichtum gegen den Trend T3 - Portal: Das Potsdamer Universitätsmagazin - 01-03/2005 Y1 - 2005 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-439846 SN - 1618-6893 IS - 01-03/2005 ER - TY - JOUR A1 - Schuch, Norbert A1 - Harrison, Sarah K. A1 - Osborne, Tobias J. A1 - Eisert, Jens T1 - Information propagation for interacting-particle systems JF - Physical review : A, Atomic, molecular, and optical physics N2 - We study the speed at which information propagates through systems of interacting quantum particles moving on a regular lattice and show that for a certain class of initial conditions there exists a maximum speed of sound at which information can propagate. Our argument applies equally to quantum spins, bosons such as in the Bose-Hubbard model, fermions, anyons, and general mixtures thereof, on arbitrary lattices of any dimension. It also pertains to dissipative dynamics on the lattice, and generalizes to the continuum for quantum fields. Our result can be seen as an analog of the Lieb-Robinson bound for strongly correlated models. Y1 - 2011 U6 - https://doi.org/10.1103/PhysRevA.84.032309 SN - 1050-2947 VL - 84 IS - 3 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Serafini, A. A1 - Eisert, Jens A1 - Wolf, M. M. T1 - Multiplicativity of maximal output purities of Gaussian channels under Gaussian inputs N2 - We address the question of the multiplicativity of the maximal p-norm output purities of bosonic Gaussian channels under Gaussian inputs. We focus on general Gaussian channels resulting from the reduction of unitary dynamics in larger Hilbert spaces. It is shown that the maximal output purity of tensor products of single-mode channels under Gaussian inputs is multiplicative for any p is an element of (1, infinity) for products of arbitrary identical channels as well as for a large class of products of different channels. In the case of p=2, multiplicativity is shown to be true for arbitrary products of generic channels acting on any number of modes Y1 - 2005 ER - TY - JOUR A1 - Wolf, M. M. A1 - Eisert, Jens T1 - Classical information capacity of a class of quantum channels N2 - We consider the additivity of the minimal output entropy and the classical information capacity of a class of quantum channels. For this class of channels, the norm of the output is maximized for the output being a normalized projection. We prove the additivity of the minimal output Renyi entropies with entropic parameters alpha is an element of [ 0, 2], generalizing an argument by Alicki and Fannes, and present a number of examples in detail. In order to relate these results to the classical information capacity, we introduce a weak form of covariance of a channel. We then identify various instances of weakly covariant channels for which we can infer the additivity of the classical information capacity. Both additivity results apply to the case of an arbitrary number of different channels. Finally, we relate the obtained results to instances of bi-partite quantum states for which the entanglement cost can be calculated Y1 - 2005 SN - 1367-2630 ER - TY - JOUR A1 - Yang, Dong A1 - Eisert, Jens T1 - Entanglement combing N2 - We show that all multipartite pure states can, under local operations, be transformed into bipartite pairwise entangled states in a "lossless fashion": An arbitrary distinguished party will keep pairwise entanglement with all other parties after the asymptotic protocol-decorrelating all other parties from each other-in a way that the degree of entanglement of this party with respect to the rest will remain entirely unchanged. The set of possible entanglement distributions of bipartite pairs is also classified. Finally, we point out several applications of this protocol as a useful primitive in quantum information theory. Y1 - 2009 UR - http://prl.aps.org/ U6 - https://doi.org/10.1103/Physrevlett.103.220501 SN - 0031-9007 ER - TY - JOUR A1 - Zoller, Peter A1 - Beth, Thomas A1 - Binosi, D. A1 - Blatt, Rainer A1 - Briegel, Hans J. A1 - Bruss, D. A1 - Calarco, Tommaso A1 - Cirac, Juan Ignacio A1 - Deutsch, David A1 - Eisert, Jens A1 - Ekert, Artur A1 - Fabre, Claude A1 - Gisin, Nicolas A1 - Grangiere, P. A1 - Grassl, Markus A1 - Haroche, Serge A1 - Imamoglu, Atac A1 - Karlson, A. A1 - Kempe, Julia A1 - Kouwenhoven, Leo P. A1 - Kröll, S. A1 - Leuchs, Gerd A1 - Lewenstein, Maciej A1 - Loss, Daniel A1 - Lütkenhaus, Norbert A1 - Massar, Serge A1 - Mooij, J. E. A1 - Plenio, Martin Bodo A1 - Polzik, Eugene A1 - Popescu, Sandu A1 - Rempe, Gerhard A1 - Sergienko, Alexander A1 - Suter, David A1 - Twamley, John A1 - Wendin, Göran A1 - Werner, Reinhard F. A1 - Winter, Andreas A1 - Wrachtrup, Jörg A1 - Zeilinger, Anton T1 - Quantum information processing and communication : Strategic report on current status, visions and goals for research in Europe N2 - We present an excerpt of the document "Quantum Information Processing and Communication: Strategic report on current status, visions and goals for research in Europe", which has been recently published in electronic form at the website of FET (the Future and Emerging Technologies Unit of the Directorate General Information Society of the European Commission, http://www.cordis.lu/ist/fet/qipc-sr.htm). This document has been elaborated, following a former suggestion by FET, by a committee of QIPC scientists to provide input towards the European Commission for the preparation of the Seventh Framework Program. Besides being a document addressed to policy makers and funding agencies (both at the European and national level), the document contains a detailed scientific assessment of the state-of-the-art, main research goals, challenges, strengths, weaknesses, visions and perspectives of all the most relevant QIPC sub-fields, that we report here Y1 - 2005 SN - 1434-6060 ER -