J. I. Cirac

Max Planck Institute of Quantum Optics, Arching, Bavaria, Germany

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Publications (359)1645.85 Total impact

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    ABSTRACT: We propose the use of photonic crystal structures to design subwavelength optical lattices in two dimensions for ultracold atoms by using both Guided Modes and Casimir-Polder forces. We further show how to use Guided Modes for photon-induced large and strongly long-range interactions between trapped atoms. Finally, we analyze the prospects of this scheme to implement spin models for quantum simulation
    07/2014;
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    ABSTRACT: We show how the static magnetic field of a finite source can be transferred and routed to arbitrary long distances. This is achieved by using transformation optics, which results in a device made of a material with a highly anisotropic magnetic permeability. We show that a simplified version of the device, made by a superconducting-ferromagnet hybrid, also leads to an excellent transfer of the magnetic field. The latter is demonstrated with a proof-of-principle experiment where a ferromagnet tube coated with a superconductor improves the transfer of static magnetic fields with respect to conventional methods by a 400% factor over distances of 14 cm.
    Physical Review Letters 06/2014; 112(25):253901. · 7.73 Impact Factor
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    ABSTRACT: We analyze the low energy excitations of spin lattice systems in two dimensions at zero temperature within the framework of projected entangled pair state models. Perturbations in the bulk give rise to physical excitations located at the edge. We identify the corresponding degrees of freedom, give a procedure to derive the edge Hamiltonian, and illustrate that it can exhibit a rich phase diagram. For topological models, the edge Hamiltonian is constrained by the topological order in the bulk, which gives rise to one-dimensional edge models with unconventional properties; for instance, a topologically ordered bulk can protect a ferromagnetic Ising chain at the edge against spontaneous symmetry breaking.
    Physical Review Letters 01/2014; 112(3):036402. · 7.73 Impact Factor
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    ABSTRACT: We propose a scheme for the deterministic generation of steady-state entanglement between the two nuclear spin ensembles in an electrically defined double quantum dot. Because of quantum interference in the collective coupling to the electronic degrees of freedom, the nuclear system is actively driven into a two-mode squeezedlike target state. The entanglement buildup is accompanied by a self-polarization of the nuclear spins towards large Overhauser field gradients. Moreover, the feedback between the electronic and nuclear dynamics leads to multistability and criticality in the steady-state solutions.
    Physical Review Letters 12/2013; 111(24):246802. · 7.73 Impact Factor
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    T. B. Wahl, H. -H. Tu, N. Schuch, J. I. Cirac
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    ABSTRACT: We show that Projected Entangled-Pair States (PEPS) in two spatial dimensions can describe chiral topological states by explicitly constructing a family of such states with a non-trivial Chern number. They are ground states of two different kinds of free-fermion Hamiltonians: (i) local and gapless; (ii) gapped, but with hopping amplitudes that decay according to a power law. We also prove that they are necessarily non-injective, and cannot correspond to exact ground states of gapped, local parent Hamiltonians. We provide numerical evidence that they can nevertheless approximate well the physical properties of topological insulators with local Hamiltonians at arbitrary temperatures.
    Physical Review Letters 12/2013; 111(23):236805. · 7.73 Impact Factor
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    M. Roncaglia, M. Rizzi, J. I. Cirac
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    ABSTRACT: We propose and analyze a nanoengineered vortex array in a thin-film type-II superconductor as a magnetic lattice for ultracold atoms. This proposal addresses several of the key questions in the development of atomic quantum simulators. By trapping atoms close to the surface, tools of nanofabrication and structuring of lattices on the scale of few tens of nanometers become available with a corresponding benefit in energy scales and temperature requirements. This can be combined with the possibility of magnetic single site addressing and manipulation together with a favorable scaling of superconducting surface-induced decoherence.
    Physical Review Letters 10/2013; 111(14):145304. · 7.73 Impact Factor
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    ABSTRACT: We analyze a criterion which guarantees that the ground states of certain many body systems are stable under perturbations. Specifically, we consider PEPS, which are believed to provide an efficient description, based on local tensors, for the low energy physics arising from local interactions. In order to assess stability in the framework of PEPS, one thus needs to understand how physically allowed perturbations of the local tensor affect the properties of the global state. In this paper, we show that a restricted version of the Local Topological Quantum Order (LTQO) condition provides a checkable criterion which allows to assess the stability of local properties of PEPS under physical perturbations. We moreover show that LTQO itself is stable under perturbations which preserve the spectral gap, leading to nontrivial examples of PEPS which possess LTQO and are thus stable under arbitrary perturbations.
    Physical review. B, Condensed matter 06/2013; 88(11). · 3.77 Impact Factor
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    ABSTRACT: We show the feasibility of tensor network solutions for lattice gauge theories in Hamiltonian formulation by applying matrix product states algorithms to the Schwinger model with zero and non-vanishing fermion mass. We introduce new techniques to compute excitations in a system with open boundary conditions, and to identify the states corresponding to low momentum and different quantum numbers in the continuum. For the ground state and both the vector and scalar mass gaps in the massive case, the MPS technique attains precisions comparable to the best results available from other techniques.
    05/2013;
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    ABSTRACT: Topology plays a central role in ensuring the robustness of a wide variety of physical phenomena. Notable examples range from the current-carrying edge states associated with the quantum Hall and the quantum spin Hall effects to topologically protected quantum memory and quantum logic operations. Here we propose and analyse a topologically protected channel for the transfer of quantum states between remote quantum nodes. In our approach, state transfer is mediated by the edge mode of a chiral spin liquid. We demonstrate that the proposed method is intrinsically robust to realistic imperfections associated with disorder and decoherence. Possible experimental implementations and applications to the detection and characterization of spin liquid phases are discussed.
    Nature Communications 03/2013; 4:1585. · 10.02 Impact Factor
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    ABSTRACT: We propose to use subwavelength confinement of light associated with the near field of plasmonic systems to create nanoscale optical lattices for ultracold atoms. Our approach combines the unique coherence properties of isolated atoms with the subwavelength manipulation and strong light-matter interaction associated with nanoplasmonic systems. It allows one to considerably increase the energy scales in the realization of Hubbard models and to engineer effective long-range interactions in coherent and dissipative many-body dynamics. Realistic imperfections and potential applications are discussed.
    Physical Review Letters 12/2012; 109(23):235309. · 7.73 Impact Factor
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    D. E. Chang, J. I. Cirac, H. J. Kimble
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    ABSTRACT: Atoms coupled to nanophotonic interfaces represent an exciting frontier for the investigation of quantum light-matter interactions. While most work has considered the interaction between statically positioned atoms and light, here we demonstrate that a wealth of phenomena can arise from the self-consistent interaction between atomic internal states, optical scattering, and atomic forces. We consider in detail the case of atoms coupled to a one-dimensional nanophotonic waveguide, and show that this interplay gives rise to self-organization of atomic positions along the waveguide, which can be probed experimentally through distinct characteristics of the reflection and transmission spectra.
    Physical Review Letters 11/2012; 110(11). · 7.73 Impact Factor
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    T. Shi, J. I. Cirac
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    ABSTRACT: We propose and analyze a scheme to observe topological phenomena with ions in microtraps. We consider a set of trapped ions forming a regular structure in two spatial dimensions and interacting with lasers. We find phonon bands with non-trivial topological properties, which are caused by the breaking of time reversal symmetry induced by the lasers. We investigate the appearance of edge modes, as well as their robustness against perturbations. Long-range hopping of phonons caused by the Coulomb interaction gives rise to flat bands which, together with induced phonon-phonon interactions, can be used to produce and explore strongly correlated states. Furthermore, some of these ideas can also be implemented with cold atoms in optical lattices.
    Physical Review A 10/2012; 87(1). · 3.04 Impact Factor
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    ABSTRACT: We show that by magnetically trapping a superconducting microsphere close to a quantum circuit, it is possible to perform ground-state cooling and prepare quantum superpositions of the center-of-mass motion of the microsphere. Due to the absence of clamping losses and time-dependent electromagnetic fields, the mechanical motion of micrometer-sized metallic spheres in the Meissner state is predicted to be very well isolated from the environment. Hence, we propose to combine the technology of magnetic microtraps and superconducting qubits to bring relatively large objects to the quantum regime.
    Physical Review Letters 10/2012; 109(14):147205. · 7.73 Impact Factor
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    ABSTRACT: The realization of devices which harness the laws of quantum mechanics represents an excit-ing challenge at the interface of modern tech-nology and fundamental science[1, 2]. An ex-emplary paragon of the power of such quantum primitives is the concept of "quantum money" [3]. A dishonest holder of a quantum bank-note will invariably fail in any forging attempts; in-deed, under assumptions of ideal measurements and decoherence-free memories such security is guaranteed by the no-cloning theorem [4]. In any practical situation, however, noise, decoherence and operational imperfections abound. Thus, the development of secure "quantum money"-type primitives capable of tolerating realistic infideli-ties is of both practical and fundamental impor-tance. Here, we propose a novel class of such pro-tocols and demonstrate their tolerance to noise; moreover, we prove their rigorous security by determining tight fidelity thresholds. Our pro-posed protocols require only the ability to pre-pare, store and measure single qubit quantum memories, making their experimental realization accessible with current technologies [5–7]. Recent extensions to Wiesner's original "quantum money" protocol [3] have garnered significant interest [8– 11]. One particular extension enables the authentication of quantum tokens via classical public communication with a trusted verifier [12]. However, to tolerate noise, the verification process must condone a certain finite frac-tion of qubit failures; naturally, such a relaxation of the verification process enhances the ability for a dishonest user to forge quantum tokens. It is exactly this interplay which we, here, seek to address, by focusing on a class of "quantum token"-protocols which involve either direct physical or classical communication verification of qubit memories.
    Proceedings of the National Academy of Sciences 10/2012; 109(40). · 9.81 Impact Factor
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    ABSTRACT: We theoretically show that intriguing features of coherent many-body physics can be observed in electron transport through a quantum dot (QD). We first derive a master-equation-based framework for electron transport in the Coulomb-blockade regime which includes hyperfine (HF) interaction with the nuclear spin ensemble in the QD. This general tool is then used to study the leakage current through a single QD in a transport setting. We find that, for an initially polarized nuclear system, the proposed setup leads to a strong current peak, in close analogy with superradiant emission of photons from atomic ensembles. This effect could be observed with realistic experimental parameters and would provide clear evidence of coherent HF dynamics of nuclear spin ensembles in QDs.
    Physical review. B, Condensed matter 08/2012; 86(8). · 3.77 Impact Factor
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    ABSTRACT: We investigate dissipative phase transitions in an open central spin system. In our model the central spin interacts coherently with the surrounding many-particle spin environment and is subject to coherent driving and dissipation. We develop analytical tools based on a self-consistent Holstein-Primakoff approximation that enable us to determine the complete phase diagram associated with the steady states of this system. It includes first- and second-order phase transitions, as well as regions of bistability, spin squeezing, and altered spin-pumping dynamics. Prospects of observing these phenomena in systems such as electron spins in quantum dots or nitrogen-vacancy centers coupled to lattice nuclear spins are briefly discussed.
    Physical Review A 07/2012; 86:012116. · 3.04 Impact Factor
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    ABSTRACT: Stable quantum bits, capable both of storing quantum information for macroscopic time scales and of integration inside small portable devices, are an essential building block for an array of potential applications. We demonstrate high-fidelity control of a solid-state qubit, which preserves its polarization for several minutes and features coherence lifetimes exceeding 1 second at room temperature. The qubit consists of a single (13)C nuclear spin in the vicinity of a nitrogen-vacancy color center within an isotopically purified diamond crystal. The long qubit memory time was achieved via a technique involving dissipative decoupling of the single nuclear spin from its local environment. The versatility, robustness, and potential scalability of this system may allow for new applications in quantum information science.
    Science 06/2012; 336(6086):1283-6. · 31.20 Impact Factor
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    ABSTRACT: We present a new characterization of quantum states, what we call Projected Entangled-Pair States (PEPS). This characterization is based on constructing pairs of maximally entangled states in a Hilbert space of dimension D2, and then projecting those states in subspaces of dimension d. In one dimension, one recovers the familiar matrix product states, whereas in higher dimensions this procedure gives rise to other interesting states. We have used this new parametrization to construct numerical algorithms to simulate the ground state properties and dynamics of certain quantum-many body systems in two dimensions.
    International Journal of Modern Physics B 01/2012; 20(30n31). · 0.46 Impact Factor
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    ABSTRACT: The realization of a scalable quantum information processor has emerged over the past decade as one of the central challenges at the interface of fundamental science and engineering. Here we propose and analyse an architecture for a scalable, solid-state quantum information processor capable of operating at room temperature. Our approach is based on recent experimental advances involving nitrogen-vacancy colour centres in diamond. In particular, we demonstrate that the multiple challenges associated with operation at ambient temperature, individual addressing at the nanoscale, strong qubit coupling, robustness against disorder and low decoherence rates can be simultaneously achieved under realistic, experimentally relevant conditions. The architecture uses a novel approach to quantum information transfer and includes a hierarchy of control at successive length scales. Moreover, it alleviates the stringent constraints currently limiting the realization of scalable quantum processors and will provide fundamental insights into the physics of non-equilibrium many-body quantum systems.
    Nature Communications 01/2012; 3:800. · 10.02 Impact Factor

Publication Stats

27k Citations
1,645.85 Total Impact Points

Institutions

  • 2002–2014
    • Max Planck Institute of Quantum Optics
      Arching, Bavaria, Germany
    • Ludwig-Maximilian-University of Munich
      München, Bavaria, Germany
    • California Institute of Technology
      • Institute for Quantum Information and Matter
      Pasadena, CA, United States
  • 2002–2013
    • Harvard University
      • Department of Physics
      Boston, MA, United States
  • 2010
    • University of Vienna
      • Faculty of Physics
      Vienna, Vienna, Austria
  • 2009
    • University of Queensland 
      • School of Mathematics and Physics
      Brisbane, Queensland, Australia
    • ETH Zurich
      • Institute for Theoretical Physics
      Zürich, ZH, Switzerland
  • 1990–2008
    • Complutense University of Madrid
      • • Departamento de Análisis Matemático
      • • Departamento de Óptica
      Madrid, Madrid, Spain
  • 2007
    • Spanish National Research Council
      • Institute of Fundamental Physics
      Madrid, Madrid, Spain
  • 1995–2007
    • University of Castilla-La Mancha
      • Departamento de Física Aplicada
      Ciudad Real, Castille-La Mancha, Spain
  • 1997–2006
    • University of Innsbruck
      • Institut für Theoretische Physik
      Innsbruck, Tyrol, Austria
  • 2001
    • Aarhus University
      • Department of Physics and Astronomy
      Aars, Region North Jutland, Denmark
    • Harvard-Smithsonian Center for Astrophysics
      • Institute for Theoretical Atomic, Molecular and Optical Physics
      Cambridge, Massachusetts, United States
  • 2000
    • University of Oxford
      • Department of Physics
      Oxford, England, United Kingdom
    • University of Science and Technology of China
      Luchow, Anhui Sheng, China
  • 1999
    • Polish Academy of Sciences
      Warszawa, Masovian Voivodeship, Poland
  • 1998
    • Antioch University, Santa Barbara
      Santa Barbara, California, United States
  • 1996–1997
    • University of California, Santa Barbara
      • Kavli Institute for Theoretical Physics
      Santa Barbara, California, United States
  • 1993
    • University of Colorado at Boulder
      • Department of Physics
      Boulder, CO, United States