Annalen der Physik

Cover image for Vol. 525 Issue 10-11

Special Issue: Quantum Simulations

November 2013

Volume 525, Issue 10-11

Pages A145–A166, 739–888, L35–L39

Issue edited by: Rainer Blatt, Immanuel Bloch, Ignacio Cirac, Peter Zoller

  1. Front Cover

    1. Top of page
    2. Front Cover
    3. Back Cover
    4. Issue Information
    5. Call for Papers
    6. Contents
    7. Retrospect
    8. Advisory Board
    9. Physics Forum
    10. Special Features
    11. Review Articles
    12. Original Papers
    13. Rapid Research Letter
    1. You have free access to this content
      Cover Picture: Ann. Phys. 10-11'2013

      Article first published online: 4 NOV 2013 | DOI: 10.1002/andp.201370100

      Thumbnail image of graphical abstract

      “Quantum Simulators”, as originally envisaged by Richard Feynman are highly controllable and specially engineered many-body systems that have the potential to shed new light on open questions in condensed matter physics, high-energy and nuclear physics. They are currently set-up and explored in a diverse range of quantum systems ranging from ultracold quantum gases, over trapped ions and photonic systems, to superconducting and semiconductor devices.

      Image: The mathematical description of a phenomenon to be investigated is programmed using a series of laser pulses to perform a quantum calculation with atoms (credit: H. Ritsch).

  2. Back Cover

    1. Top of page
    2. Front Cover
    3. Back Cover
    4. Issue Information
    5. Call for Papers
    6. Contents
    7. Retrospect
    8. Advisory Board
    9. Physics Forum
    10. Special Features
    11. Review Articles
    12. Original Papers
    13. Rapid Research Letter
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      Cover Picture: Ann. Phys. 10-11'2013

      Article first published online: 4 NOV 2013 | DOI: 10.1002/andp.201370101

      Thumbnail image of graphical abstract

      Sketch of a quasi one-dimensional Wigner crystal of mutually repelling quantum particles (e.g. ions) in a cigar-shaped trap. Depending on the radial confinement, the equilibrium configuration is either a linear structure (top layer) or a zig-zag structure (bottom layer). In the article by P. Silvi et al., a full characterization of such quantum phase transition is studied, through theory and numerical methods.

      Picture: P. Silvi et al., pp. 827–832 in this issue

  3. Issue Information

    1. Top of page
    2. Front Cover
    3. Back Cover
    4. Issue Information
    5. Call for Papers
    6. Contents
    7. Retrospect
    8. Advisory Board
    9. Physics Forum
    10. Special Features
    11. Review Articles
    12. Original Papers
    13. Rapid Research Letter
    1. You have free access to this content
      Issue Information: Ann. Phys. 10-11'2013

      Article first published online: 4 NOV 2013 | DOI: 10.1002/andp.201370107

  4. Call for Papers

    1. Top of page
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    3. Back Cover
    4. Issue Information
    5. Call for Papers
    6. Contents
    7. Retrospect
    8. Advisory Board
    9. Physics Forum
    10. Special Features
    11. Review Articles
    12. Original Papers
    13. Rapid Research Letter
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      Call For Papers: Ann. Phys. 10-11'2013 (page A145)

      Article first published online: 4 NOV 2013 | DOI: 10.1002/andp.201370102

  5. Contents

    1. Top of page
    2. Front Cover
    3. Back Cover
    4. Issue Information
    5. Call for Papers
    6. Contents
    7. Retrospect
    8. Advisory Board
    9. Physics Forum
    10. Special Features
    11. Review Articles
    12. Original Papers
    13. Rapid Research Letter
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      Contents: Ann. Phys. 10-11'2013 (pages A146–A150)

      Article first published online: 4 NOV 2013 | DOI: 10.1002/andp.201370103

  6. Retrospect

    1. Top of page
    2. Front Cover
    3. Back Cover
    4. Issue Information
    5. Call for Papers
    6. Contents
    7. Retrospect
    8. Advisory Board
    9. Physics Forum
    10. Special Features
    11. Review Articles
    12. Original Papers
    13. Rapid Research Letter
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  7. Advisory Board

    1. Top of page
    2. Front Cover
    3. Back Cover
    4. Issue Information
    5. Call for Papers
    6. Contents
    7. Retrospect
    8. Advisory Board
    9. Physics Forum
    10. Special Features
    11. Review Articles
    12. Original Papers
    13. Rapid Research Letter
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      Advisory Board (page A152)

      Article first published online: 4 NOV 2013 | DOI: 10.1002/andp.201370105

  8. Physics Forum

    1. Top of page
    2. Front Cover
    3. Back Cover
    4. Issue Information
    5. Call for Papers
    6. Contents
    7. Retrospect
    8. Advisory Board
    9. Physics Forum
    10. Special Features
    11. Review Articles
    12. Original Papers
    13. Rapid Research Letter
    1. Editorial

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      Quantum simulation - an exciting adventure (pages A153–A154)

      Rainer Blatt, Immanuel Bloch, Ignacio Cirac and Peter Zoller

      Article first published online: 4 NOV 2013 | DOI: 10.1002/andp.201300738

    2. Then & Now

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    3. Expert Opinion

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    4. You have free access to this content
    5. Erratum

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      Observational effects from quantum cosmology (page A165)

      Gianluca Calcagni

      Article first published online: 24 SEP 2013 | DOI: 10.1002/andp.201380227

      This article corrects:

      Observational effects from quantum cosmology

      Vol. 525, Issue 5, 323–338, Article first published online: 12 MAR 2013

  9. Special Features

    1. Top of page
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    3. Back Cover
    4. Issue Information
    5. Call for Papers
    6. Contents
    7. Retrospect
    8. Advisory Board
    9. Physics Forum
    10. Special Features
    11. Review Articles
    12. Original Papers
    13. Rapid Research Letter
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      Special Features (page A166)

      Article first published online: 4 NOV 2013 | DOI: 10.1002/andp.201370106

  10. Review Articles

    1. Top of page
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    3. Back Cover
    4. Issue Information
    5. Call for Papers
    6. Contents
    7. Retrospect
    8. Advisory Board
    9. Physics Forum
    10. Special Features
    11. Review Articles
    12. Original Papers
    13. Rapid Research Letter
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      Superposition, entanglement, and raising Schrödinger's cat (pages 739–752)

      David J. Wineland

      Article first published online: 6 SEP 2013 | DOI: 10.1002/andp.201300736

      Thumbnail image of graphical abstract

      Experimental control of quantum systems has been pursued widely since the invention of quantum mechanics. Today, we can in fact experiment with individual quantum systems, deterministically preparing superpositions and entanglements. In his Nobel lecture, D. J. Wineland gives an overview of this research which has led to the Nobel prize in physics in 2012**.

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      Controlling photons in a box and exploring the quantum to classical boundary (pages 753–776)

      Serge Haroche

      Article first published online: 23 SEP 2013 | DOI: 10.1002/andp.201300737

      Thumbnail image of graphical abstract

      Photons trapped in a superconducting cavity constitute an ideal system to realize some of the thought experiments imagined by the founding fathers of quantum physics. Physics laureate S. Haroche gives a personal account of the experiments performed with this “photon box” at the Ecole Normale Supérieure**.

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      Ultracold quantum gases and lattice systems: quantum simulation of lattice gauge theories (pages 777–796)

      U.-J. Wiese

      Article first published online: 22 JUL 2013 | DOI: 10.1002/andp.201300104

      Thumbnail image of graphical abstract

      Abelian and non-Abelian gauge theories are of central importance in many areas of physics. In condensed matter physics, Abelian U(1) lattice gauge theories arise in the description of certain quantum spin liquids. In quantum information theory, Kitaev's toric code is a Z(2) lattice gauge theory. In particle physics, Quantum Chromodynamics (QCD), the non-Abelian SU(3) gauge theory of the strong interactions between quarks and gluons, is non-perturbatively regularized on a lattice. Quantum link models extend the concept of lattice gauge theories beyond the Wilson formulation, and are well suited for both digital and analog quantum simulation using ultracold atomic gases in optical lattices. Since quantum simulators do not suffer from the notorious sign problem, they open the door to studies of the real-time evolution of strongly coupled quantum systems, which are impossible with classical simulation methods. A plethora of interesting lattice gauge theories suggests itself for quantum simulation, which should allow us to address very challenging problems, ranging from confinement and deconfinement, or chiral symmetry breaking and its restoration at finite baryon density, to color superconductivity and the real-time evolution of heavy-ion collisions, first in simpler model gauge theories and ultimately in QCD.

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      Detection of topological matter with quantum gases (pages 797–807)

      I. B. Spielman

      Article first published online: 31 JUL 2013 | DOI: 10.1002/andp.201300110

      Thumbnail image of graphical abstract

      Creating and measuring topological matter – with non-local order deeply embedded in the global structure of its quantum mechanical eigenstates – presents unique experimental challenges. Since this order has no signature in local correlation functions, it might seem experimentally inaccessible in any macroscopic system; however, as the precisely quantized Hall plateaux in integer and fractional quantum Hall systems show, topology can have macroscopic signatures at the system's edges. Ultracold atoms provide new experimental platforms where both the intrinsic topology and the edge behavior can be directly measured. This article reviews, using specific examples, how non-interacting topological matter may be created and measured in quantum gases.

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      Quantum Dot Systems: a versatile platform for quantum simulations (pages 808–826)

      Pierre Barthelemy and Lieven M. K. Vandersypen

      Article first published online: 16 SEP 2013 | DOI: 10.1002/andp.201300124

      Thumbnail image of graphical abstract

      Quantum mechanics often results in extremely complex phenomena, especially when the quantum system under consideration is composed of many interacting particles. The states of these many-body systems live in a space so large that classical numerical calculations cannot compute them. Quantum simulations can be used to overcome this problem: complex quantum problems can be solved by studying experimentally an artificial quantum system operated to simulate the desired hamiltonian.

      Quantum dot systems have shown to be widely tunable quantum systems, that can be efficiently controlled electrically. This tunability and the versatility of their design makes them very promising quantum simulators. This paper reviews the progress towards digital quantum simulations with individually controlled quantum dots, as well as the analog quantum simulations that have been performed with these systems. The possibility to use large arrays of quantum dots to simulate the low-temperature Hubbard model is also discussed. The main issues along that path are presented and new ideas to overcome them are proposed.

  11. Original Papers

    1. Top of page
    2. Front Cover
    3. Back Cover
    4. Issue Information
    5. Call for Papers
    6. Contents
    7. Retrospect
    8. Advisory Board
    9. Physics Forum
    10. Special Features
    11. Review Articles
    12. Original Papers
    13. Rapid Research Letter
    1. Full characterization of the quantum linear-zigzag transition in atomic chains (pages 827–832)

      Pietro Silvi, Gabriele De Chiara, Tommaso Calarco, Giovanna Morigi and Simone Montangero

      Article first published online: 31 JUL 2013 | DOI: 10.1002/andp.201300090

      Thumbnail image of graphical abstract

      A string of repulsively interacting particles exhibits a phase transition to a zigzag structure, by reducing the transverse trap potential or the interparticle distance. Based on the emergent symmetry ℤ2 it has been argued that this instability is a quantum phase transition, which can be mapped to an Ising model in transverse field. An extensive Density Matrix Renormalization Group analysis is performed, resulting in an high-precision evaluation of the critical exponents and of the central charge of the system, confirming that the quantum linear-zigzag transition belongs to the critical Ising model universality class. Quantum corrections to the classical phase diagram are computed, and the range of experimental parameters where quantum effects play a role is provided. These results show that structural instabilities of one-dimensional interacting atomic arrays can simulate quantum critical phenomena typical of ferromagnetic systems.

    2. Quantum simulations of localization effects with dipolar interactions (pages 833–844)

      Gonzalo A. Álvarez, Robin Kaiser and Dieter Suter

      Article first published online: 8 OCT 2013 | DOI: 10.1002/andp.201300096

      Thumbnail image of graphical abstract

      Quantum information processing often uses systems with dipolar interactions. Here a nuclear spin-based quantum simulator is used to study the spreading of information in such a dipolar-coupled system. While the information spreads with no apparent limits in the case of ideal dipolar couplings, additional perturbations limit the spreading, leading to localization. In previous work [Phys. Rev. Lett. 104, 230403 (2010)], it was found that the system size reaches a dynamic equilibrium that decreases with the square of the perturbation strength. This work examines the impact of a disordered Hamiltonian with dipolar 1/r3 interactions. It shows that the expansion of the cluster of spins freezes in the presence of large disorder, reminiscent of Anderson localization of non-interacting waves in a disordered potential.

    3. Simulating quantum magnets with symmetric top molecules (pages 845–865)

      Michael L. Wall, Kenji Maeda and Lincoln D. Carr

      Article first published online: 23 SEP 2013 | DOI: 10.1002/andp.201300105

      Thumbnail image of graphical abstract

      A correspondence is established between the electric dipole matrix elements of a polyatomic symmetric top molecule in a state with nonzero projection of the total angular momentum on the symmetry axis of the molecule and the magnetic dipole matrix elements of a magnetic dipole associated with an elemental spin F. It is shown that this correspondence makes it possible to perform quantum simulation of the single-particle spectrum and the dipole-dipole interactions of magnetic dipoles in a static external magnetic field B with symmetric top molecules subject to a static external electric field EDC. It is further shown that no such correspondence exists for 1Σ molecules in static fields, such as the alkali metal dimers. The effective spin angular momentum of the simulated magnetic dipole corresponds to the rotational angular momentum of the symmetric top molecule, and so quantum simulation of arbitrarily large integer spins is possible. Further, taking the molecule CH3F as an example, it is shown that the characteristic dipole-dipole interaction energies of the simulated magnetic dipole are a factor of 620, 600, and 310 larger than for the highly magnetic atoms Chromium, Erbium, and Dysprosium, respectively. Several applications of the correspondence for many-body physics are presented, including long-range and anisotropic spin models with arbitrary integer spin S using symmetric top molecules in optical lattices, quantum simulation of molecular magnets, and spontaneous demagnetization of Bose-Einstein condensates due to dipole-dipole interactions. These results are expected to be relevant as cold symmetric top molecules reach quantum degeneracy through Stark deceleration and opto-electrical cooling.

    4. Quantum simulations of the early universe (pages 866–876)

      Bogdan Opanchuk, Rodney Polkinghorne, Oleksandr Fialko, Joachim Brand and Peter D. Drummond

      Article first published online: 10 SEP 2013 | DOI: 10.1002/andp.201300113

      Thumbnail image of graphical abstract

      A procedure is described whereby a linearly coupled spinor Bose condensate can be used as a physically accessible quantum simulator of the early universe. In particular, an experiment to generate an analog of an unstable vacuum in a relativistic scalar field theory is proposed. This is related to quantum theories of the inflationary phase of the early universe. There is an unstable vacuum sector whose dynamics correspond to the quantum sine-Gordon equations in one, two or three space dimensions. Numerical simulations of the expected behavior are reported using a truncated Wigner phase-space method, giving evidence for the dynamical formation of complex spatial clusters. Preliminary results showing the dependence on coupling strength, condensate size and dimensionality are obtained.

    5. Resource efficient gadgets for compiling adiabatic quantum optimization problems (pages 877–888)

      Ryan Babbush, Bryan O'Gorman and Alán Aspuru-Guzik

      Article first published online: 3 SEP 2013 | DOI: 10.1002/andp.201300120

      Thumbnail image of graphical abstract

      A resource efficient method by which the ground-state of an arbitrary k-local, optimization Hamiltonian can be encoded as the ground-state of a (k – 1)-local, optimization Hamiltonian is developed. This result is important because adiabatic quantum algorithms are often most easily formulated using many-body interactions but experimentally available interactions are generally 2-body. In this context, the efficiency of a reduction gadget is measured by the number of ancilla qubits required as well as the amount of control precision needed to implement the resulting Hamiltonian. First, methods of applying these gadgets to obtain 2-local Hamiltonians using the least possible number of ancilla qubits are optimized. Next, a novel reduction gadget which minimizes control precision and a heuristic which uses this gadget to compile 3-local problems with a significant reduction in control precision are shown. Finally, numerics are presented which indicate a substantial decrease in the resources required to implement randomly generated, 3-body optimization Hamiltonians when compared to other methods in the literature.

  12. Rapid Research Letter

    1. Top of page
    2. Front Cover
    3. Back Cover
    4. Issue Information
    5. Call for Papers
    6. Contents
    7. Retrospect
    8. Advisory Board
    9. Physics Forum
    10. Special Features
    11. Review Articles
    12. Original Papers
    13. Rapid Research Letter
    1. Fluctuations and quantum criticality in the two-dimensional Bose Hubbard model (pages L35–L39)

      Eric Duchon and Nandini Trivedi

      Article first published online: 8 OCT 2013 | DOI: 10.1002/andp.201300109

      Thumbnail image of graphical abstract

      At a quantum phase transition, one ground state evolves into a different one by passing through a quantum critical region with enhanced spatial and temporal fluctuations. A method to map the quantum critical region using the single, local quantity R, the ratio of compressibility to local number fluctuations is proposed. R can be calculated from in situ experiments and also enables thermometry and phase diagnosis (for example whether superfluid or Mott insulating). The definition of R can be generalized to inhomogeneous systems and provides a powerful tool for experimentally mapping the finite temperature phase diagram demonstrated here for the two-dimensional Bose Hubbard model.

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