Publications old

@article{Tschirsich2019,

title = {Phase diagram and conformal string excitations of square ice using gauge invariant matrix product states},

author = {Ferdinand Tschirsich and Simone Montangero and Marcello Dalmonte},

url = {http://arxiv.org/abs/1807.00826},

doi = {10.21468/SciPostPhys.6.3.028},

issn = {2542-4653},

year  = {2019},

date = {2019-03-06},

volume = {6},

number = {3},

pages = {028},

abstract = {We investigate the ground state phase diagram of square ice — a U(1) lattice gauge theory in two spatial dimensions — using gauge invariant tensor network techniques. By correlation function, Wilson loop, and entanglement diagnostics, we characterize its phases and the transitions between them, finding good agreement with previous studies. We study the entanglement properties of string excitations on top of the ground state, and provide direct evidence of the fact that the latter are described by a conformal field theory. Our results pave the way to the application of tensor network methods to confining, two-dimensional lattice gauge theories, to investigate their phase diagrams and low-lying excitations.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{goerz_erratum:_2019,

title = {Erratum: Optimizing for an arbitrary perfect entangler. II. Application [Phys. Rev. A 91 , 062307 (2015)]},

author = {Michael H. Goerz and Giulia Gualdi and Daniel M. Reich and Christiane P. Koch and Felix Motzoi and K. Birgitta Whaley and Jiří Vala and Matthias M. Müller and Simone Montangero and Tommaso Calarco},

url = {https://link.aps.org/doi/10.1103/PhysRevA.99.019903},

doi = {10.1103/PhysRevA.99.019903},

issn = {2469-9926},

year  = {2019},

date = {2019-01-23},

volume = {99},

number = {1},

pages = {019903},

abstract = {© 2019 American Physical Society. The difficulty of an optimization task in quantum information science depends on the proper mathematical expression of the physical target. Here we demonstrate the power of optimization functionals targeting an arbitrary perfect two-qubit entangler, which allow generation of a maximally entangled state from some initial product state. We show for two quantum information platforms of current interest, i.e., nitrogen vacancy centers in diamond and superconducting Josephson junctions, that an arbitrary perfect entangler can be reached faster and with higher fidelity than both specific two-qubit gates and local equivalence classes of two-qubit gates. Our results are obtained using two independent optimization approaches, underscoring the critical role of the optimization target.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Weiss2018,

title = {Kibble-Zurek scaling of the one-dimensional Bose-Hubbard model at finite temperatures},

author = {Werner Weiss and Matthias Gerster and Daniel Jaschke and Pietro Silvi and Simone Montangero},

url = {http://arxiv.org/abs/1808.04649},

doi = {10.1103/PhysRevA.98.063601},

issn = {2469-9926},

year  = {2018},

date = {2018-12-03},

volume = {98},

number = {6},

pages = {063601},

abstract = {We use tensor network methods - Matrix Product States, Tree Tensor Networks, and Locally Purified Tensor Networks - to simulate the one dimensional Bose-Hubbard model for zero and finite temperatures in experimentally accessible regimes. We first explore the effect of thermal fluctuations on the system ground state by characterizing its Mott and superfluid features. Then, we study the behavior of the out-of-equilibrium dynamics induced by quenches of the hopping parameter. We confirm a Kibble-Zurek scaling for zero temperature and characterize the finite temperature behavior, which we explain by means of a simple argument.},

note = {Publisher: American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{gorlach_simulation_2018,

title = {Simulation of two-boson bound states using arrays of driven-dissipative coupled linear optical resonators},

author = {Maxim A. Gorlach and Marco Di_Liberto and Alessio Recati and Iacopo Carusotto and Alexander N. Poddubny and Chiara Menotti},

doi = {10.1103/PhysRevA.98.063625},

issn = {24699934},

year  = {2018},

date = {2018-12-01},

urldate = {2018-12-01},

journal = {Physical Review A},

volume = {98},

number = {6},

abstract = {We present a strategy based on two-dimensional arrays of coupled linear optical resonators to investigate the two-body physics of interacting bosons in one-dimensional lattices. In particular, we want to address the bound pairs in topologically nontrivial Su-Schrieffer-Heeger arrays. Taking advantage of the driven-dissipative nature of the resonators, we propose spectroscopic protocols to detect and tomographically characterize bulk doublon bands and doublon edge states from the spatially resolved transmission spectra, and to highlight Feshbach resonance effects in two-body collision processes. We discuss the experimental feasibility using state-of-the-art devices, with a specific eye on arrays of semiconductor micropillar cavities.},

note = {Publisher: American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Heck2018,

title = {Remote optimization of an ultra-cold atoms experiment by experts and citizen scientists},

author = {Robert Heck and Oana Vuculescu and Jens Jakob Sørensen and Jonathan Zoller and Morten G Andreasen and Mark G Bason and Poul Ejlertsen and Ottó Elíasson and Pinja Haikka and Jens S Laustsen and Lærke L Nielsen and Andrew Mao and Romain Müller and Mario Napolitano and Mads K Pedersen and Aske R Thorsen and Carsten Bergenholtz and Tommaso Calarco and Simone Montangero and Jacob F Sherson},

url = {http://www.ncbi.nlm.nih.gov/pubmed/30413625},

doi = {10.1073/pnas.1716869115},

issn = {1091-6490},

year  = {2018},

date = {2018-11-09},

urldate = {2018-11-12},

pages = {201716869},

abstract = {We introduce a novel remote interface to control and optimize the experimental production of Bose-Einstein condensates (BECs) and find improved solutions using two distinct implementations. First, a team of theoreticians employed a Remote version of their dCRAB optimization algorithm (RedCRAB), and second a gamified interface allowed 600 citizen scientists from around the world to participate in real-time optimization. Quantitative studies of player search behavior demonstrated that they collectively engage in a combination of local and global search. This form of adaptive search prevents premature convergence by the explorative behavior of low-performing players while high-performing players locally refine their solutions. In addition, many successful citizen science games have relied on a problem representation that directly engaged the visual or experiential intuition of the players. Here we demonstrate that citizen scientists can also be successful in an entirely abstract problem visualization. This gives encouragement that a much wider range of challenges could potentially be open to gamification in the future.},

note = {Publisher: National Academy of Sciences},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Jaschke2018,

title = {One-dimensional many-body entangled open quantum systems with tensor network methods},

author = {Daniel Jaschke and Simone Montangero and Lincoln D. Carr},

url = {http://arxiv.org/abs/1804.09796},

doi = {10.1088/2058-9565/aae724},

issn = {2058-9565},

year  = {2018},

date = {2018-11-06},

volume = {4},

number = {1},

pages = {013001},

abstract = {We present a collection of methods to simulate entangled dynamics of open quantum systems governed by the Lindblad equation with tensor network methods. Tensor network methods using matrix product states have been proven very useful to simulate many-body quantum systems and have driven many innovations in research. Since the matrix product state design is tailored for closed one-dimensional systems governed by the Schrtextbackslashödinger equation, the next step for many-body quantum dynamics is the simulation of open quantum systems. We review the three dominant approaches to the simulation of open quantum systems via the Lindblad master equation: quantum trajectories, matrix product density operators, and locally purified tensor networks. Selected examples guide possible applications of the methods and serve moreover as a benchmark between the techniques. These examples include the finite temperature states of the transverse quantum Ising model, the dynamics of an exciton traveling under the influence of spontaneous emission and dephasing, and a double-well potential simulated with the Bose-Hubbard model including dephasing. We analyze which approach is favorable leading to the conclusion that a complete set of all three methods is most beneficial, push- ing the limits of different scenarios. The convergence studies using analytical results for macroscopic variables and exact diagonalization methods as comparison, show, for example, that matrix product density operators are favorable for the exciton problem in our study. All three methods access the same library, i.e., the software package Open Source Matrix Product States, allowing us to have a meaningful comparison between the approaches based on the selected examples. For example, tensor operations are accessed from the same subroutines and with the same optimization eliminating one possible bias in a comparison of such numerical methods.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{mukherjee_experimental_2018,

title = {Experimental Observation of Aharonov-Bohm Cages in Photonic Lattices},

author = {Sebabrata Mukherjee and Marco Di_Liberto and Patrik Öhberg and Robert R. Thomson and Nathan Goldman},

doi = {10.1103/PhysRevLett.121.075502},

issn = {10797114},

year  = {2018},

date = {2018-08-01},

urldate = {2018-08-01},

journal = {Physical Review Letters},

volume = {121},

number = {7},

abstract = {We report on the experimental realization of a uniform synthetic magnetic flux and the observation of Aharonov-Bohm cages in photonic lattices. Considering a rhombic array of optical waveguides, we engineer modulation-assisted tunneling processes that effectively produce nonzero magnetic flux per plaquette. This synthetic magnetic field for light can be tuned at will by varying the phase of the modulation. In the regime where half a flux quantum is realized in each plaquette, all the energy bands dramatically collapse into nondispersive (flat) bands and all eigenstates are completely localized. We demonstrate this Aharonov-Bohm caging by studying the propagation of light in the bulk of the photonic lattice. Besides, we explore the dynamics on the edge of the lattice and discuss how the corresponding edge states can be continuously connected to the topological edge states of the Creutz ladder. Our photonic lattice constitutes an appealing platform where the interplay between engineered gauge fields, frustration, localization, and topological properties can be finely studied.},

note = {arXiv: 1805.03564 

Publisher: American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Gerster2018,

title = {Dynamical Ginzburg criterion for the quantum-classical crossover of the Kibble-Zurek mechanism},

author = {Matthias Gerster and Benedikt Haggenmiller and Ferdinand Tschirsich and Pietro Silvi and Simone Montangero},

url = {http://arxiv.org/abs/1807.10611},

year  = {2018},

date = {2018-07-27},

pages = {1–11},

abstract = {We introduce a simple criterion for lattice models to predict quantitatively the crossover between the classical and the quantum scaling of the Kibble-Zurek mechanism, as the one observed in a lattice $textbackslashphitextasciicircum4$-model in 1+1 dimensions [Phys. Rev. Lett. 116, 225701 (2016)]. We show that the crossover is a general feature of critical models on a lattice, by testing our paradigm on the quantum Ising model in transverse field for arbitrary spin-$s$ ($s textbackslashgeq 1/2$) in 1+1 dimensions. By means of tensor network methods, we fully characterize the equilibrium properties of this model, and locate the quantum critical regions via our dynamical Ginzburg criterion. We numerically simulate the Kibble-Zurek quench dynamics and show the validity of our picture, also according to finite-time scaling analysis.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{chaviguri_density-dependent_2018,

title = {Density-dependent hopping for ultracold atoms immersed in a Bose-Einstein-condensate vortex lattice},

author = {R. H. Chaviguri and T. Comparin and M. Di_Liberto and M. A. Caracanhas},

doi = {10.1103/PhysRevA.97.023614},

issn = {24699934},

year  = {2018},

date = {2018-02-01},

urldate = {2018-02-01},

journal = {Physical Review A},

volume = {97},

number = {2},

abstract = {Both mixtures of atomic Bose-Einstein condensates and systems with atoms trapped in optical lattices have been intensely explored theoretically, mainly due to the exceptional developments on the experimental side. We investigate the properties of ultracold atomic impurities (bosons) immersed in a vortex lattice of a second Bose-condensed species. In contrast to the static optical-lattice configuration, the vortex lattice presents intrinsic dynamics given by its Tkachenko modes. These excitations induce additional correlations between the impurities, which consist of a long-range attractive potential and a density-dependent hopping, described here in the framework of an extended Bose-Hubbard model. We compute the quantum phase diagram of the impurity species through a Gutzwiller ansatz and through the mean-field approach, and separately identify the effects of the two additional terms, i.e., the shift and the deformation of the Mott-insulator lobes. The long-range attraction, in particular, induces the existence of a triple point in the phase diagram, in agreement with previous quantum Monte Carlo calculations [Chaviguri et al., Phys. Rev. A 95, 053639 (2017)2469-992610.1103/PhysRevA.95.053639].},

note = {Publisher: American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{di_liberto_particle-hole_2018,

title = {Particle-Hole Character of the Higgs and Goldstone Modes in Strongly Interacting Lattice Bosons},

author = {M. Di_Liberto and A. Recati and N. Trivedi and I. Carusotto and C. Menotti},

doi = {10.1103/PhysRevLett.120.073201},

issn = {10797114},

year  = {2018},

date = {2018-02-01},

urldate = {2018-02-01},

journal = {Physical Review Letters},

volume = {120},

number = {7},

abstract = {We study the low-energy excitations of the Bose-Hubbard model in the strongly interacting superfluid phase using a Gutzwiller approach. We extract the single-particle and single-hole excitation amplitudes for each mode and report emergent mode-dependent particle-hole symmetry on specific arc-shaped lines in the phase diagram connecting the well-known Lorentz-invariant limits of the Bose-Hubbard model. By tracking the in-phase particle-hole symmetric oscillations of the order parameter, we provide an answer to the long-standing question about the fate of the pure amplitude Higgs mode away from the integer-density critical point. Furthermore, we point out that out-of-phase symmetric oscillations in the gapless Goldstone mode are responsible for a full suppression of the condensate density oscillations. Possible detection protocols are also discussed.},

note = {arXiv: 1709.06575 

Publisher: American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Kohn2017,

title = {Probabilistic low-rank factorization accelerates tensor network simulations of critical quantum many-body ground states},

author = {Lucas Kohn and Ferdinand Tschirsich and Maximilian Keck and Martin B. Plenio and Dario Tamascelli and Simone Montangero},

url = {http://arxiv.org/abs/1710.01463},

doi = {10.1103/PhysRevE.97.013301},

issn = {2470-0045},

year  = {2018},

date = {2018-01-03},

volume = {97},

number = {1},

pages = {013301},

abstract = {We provide evidence that randomized low-rank factorization is a powerful tool for the determination of the ground state properties of low-dimensional lattice Hamiltonians through tensor network techniques. In particular, we show that randomized matrix factorization outperforms truncated singular value decomposition based on state-of-the-art deterministic routines in TEBD and DMRG-style simulations, even when the system under study gets close to a phase transition: We report linear speedups in the bond- or local dimension, of up to 24 times in quasi-2D cylindrical systems.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{salerno_topological_2018,

title = {Topological two-body bound states in the interacting Haldane model},

author = {Grazia Salerno and Marco Di_Liberto and Chiara Menotti and Iacopo Carusotto},

doi = {10.1103/PhysRevA.97.013637},

issn = {24699934},

year  = {2018},

date = {2018-01-01},

urldate = {2018-01-01},

journal = {Physical Review A},

volume = {97},

number = {1},

abstract = {We study the topological properties of the two-body bound states in an interacting Haldane model as a function of interparticle interactions. In particular, we identify topological phases where the two-body edge states have either the same or the opposite chirality as compared to single-particle edge states. We highlight that in the moderately interacting regime, which is relevant for the experimental realization with ultracold atoms, the topological transition is affected by the internal structure of the bound state, and the phase boundaries are consequently deformed.},

note = {arXiv: 1711.01272 

Publisher: American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Montangero2018,

title = {Exploration of experimental design and statistical methods using the textitstick-on-the-wall spaghetti rule},

author = {Simone Montangero and Francesca Vittone and Sally Olderbak and Oliver Wilhelm},

url = {http://doi.wiley.com/10.1111/test.12149},

doi = {10.1111/test.12149},

issn = {0141982X},

year  = {2018},

date = {2018-01-01},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{di_liberto_two-body_2017,

title = {Two-body bound and edge states in the extended SSH Bose-Hubbard model},

author = {M. Di_Liberto and A. Recati and I. Carusotto and C. Menotti},

doi = {10.1140/epjst/e2016-60388-y},

issn = {19516401},

year  = {2017},

date = {2017-07-01},

urldate = {2017-07-01},

journal = {European Physical Journal: Special Topics},

volume = {226},

number = {12},

pages = {2751–2762},

abstract = {We study the bosonic two-body problem in a Su-Schrieffer-Heeger dimerized chain with on-site and nearest-neighbor interactions. We find two classes of bound states. The first, similar to the one induced by on-site interactions, has its center of mass on the strong link, whereas the second, existing only thanks to nearest-neighbor interactions, is centered on the weak link. We identify energy crossings between these states and analyse them using exact diagonalization and perturbation theory. In the presence of open boundary conditions, novel strongly-localized edge-bound states appear in the spectrum as a consequence of the interplay between lattice geometry, on-site and nearest-neighbor interactions. Contrary to the case of purely on-site interactions, such EBS persist even in the strongly interacting regime.},

note = {arXiv: 1612.02601 

Publisher: Springer Verlag},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{di_liberto_two-body_2016,

title = {Two-body physics in the Su-Schrieffer-Heeger model},

author = {M. Di_Liberto and A. Recati and I. Carusotto and C. Menotti},

doi = {10.1103/PhysRevA.94.062704},

issn = {24699934},

year  = {2016},

date = {2016-12-01},

urldate = {2016-12-01},

journal = {Physical Review A},

volume = {94},

number = {6},

abstract = {We consider two interacting bosons in a dimerized Su-Schrieffer-Heeger (SSH) lattice. We identify a rich variety of two-body states. In particular, for open boundary conditions and moderate interactions, edge bound states (EBS) are present even for the dimerization that does not sustain single-particle edge states. Moreover, for large values of the interactions, we find a breaking of the standard bulk-boundary correspondence. Based on the mapping of two interacting particles in one dimension onto a single particle in two dimensions, we propose an experimentally realistic coupled optical fibers setup as quantum simulator of the two-body SSH model. This setup is able to highlight the localization properties of the states as well as the presence of a resonant scattering mechanism provided by a bound state that crosses the scattering continuum, revealing the closed-channel population in real time and real space.},

note = {arXiv: 1608.07341 

Publisher: American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{di_liberto_topological_2016,

title = {Topological varma superfluid in optical lattices},

author = {M. Di_Liberto and A. Hemmerich and C. Morais Smith},

doi = {10.1103/PhysRevLett.117.163001},

issn = {10797114},

year  = {2016},

date = {2016-10-01},

urldate = {2016-10-01},

journal = {Physical Review Letters},

volume = {117},

number = {16},

abstract = {Topological states of matter are peculiar quantum phases showing different edge and bulk transport properties connected by the bulk-boundary correspondence. While noninteracting fermionic topological insulators are well established by now and have been classified according to a tenfold scheme, the possible realization of topological states for bosons has not been explored much yet. Furthermore, the role of interactions is far from being understood. Here, we show that a topological state of matter exclusively driven by interactions may occur in the p band of a Lieb optical lattice filled with ultracold bosons. The single-particle spectrum of the system displays a remarkable parabolic band-touching point, with both bands exhibiting non-negative curvature. Although the system is neither topological at the single-particle level nor for the interacting ground state, on-site interactions induce an anomalous Hall effect for the excitations, carrying a nonzero Chern number. Our work introduces an experimentally realistic strategy for the formation of interaction-driven topological states of bosons.},

note = {arXiv: 1604.06055 

Publisher: American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{di_liberto_ultracold_2014,

title = {Ultracold fermions in a one-dimensional bipartite optical lattice: Metal-insulator transitions driven by shaking},

author = {M. Di_Liberto and D. Malpetti and G. I. Japaridze and C. Morais Smith},

doi = {10.1103/PhysRevA.90.023634},

issn = {10941622},

year  = {2014},

date = {2014-08-01},

urldate = {2014-08-01},

journal = {Physical Review A - Atomic, Molecular, and Optical Physics},

volume = {90},

number = {2},

abstract = {We theoretically investigate the behavior of a system of fermionic atoms loaded in a bipartite one-dimensional optical lattice that is under the action of an external time-periodic driving force. By using Floquet theory, an effective model is derived. The bare hopping coefficients are renormalized by zeroth-order Bessel functions of the first kind with different arguments for the nearest-neighbor and next-nearest-neighbor hopping. The insulating behavior characterizing the system at half filling in the absence of driving is dynamically suppressed, and for particular values of the driving parameter the system becomes either a standard metal or an unconventional metal with four Fermi points. The existence of the four-Fermi-point metal relies on the fact that, as a consequence of the shaking procedure, the next-nearest-neighbor hopping coefficients become significant compared to the nearest-neighbor ones. We use the bosonization technique to investigate the effect of on-site Hubbard interactions on the four-Fermi-point metal-insulator phase transition. Attractive interactions are expected to enlarge the regime of parameters where the unconventional metallic phase arises, whereas repulsive interactions reduce it. This metallic phase is known to be a Luther-Emery liquid (spin-gapped metal) for both repulsive and attractive interactions, contrary to the usual Hubbard model, which exhibits a Mott-insulator phase for repulsive interactions. Ultracold fermions in driven one-dimensional bipartite optical lattices provide an interesting platform for the realization of this long-studied four-Fermi-point unconventional metal.},

note = {Publisher: American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{liberto_quantum_2014,

title = {Quantum simulation of correlated-hopping models with fermions in optical lattices},

author = {M. Di_Liberto and C. E. Creffield and G. I. Japaridze and C. Morais Smith},

doi = {10.1103/PhysRevA.89.013624},

issn = {10502947},

year  = {2014},

date = {2014-01-01},

urldate = {2014-01-01},

journal = {Physical Review A - Atomic, Molecular, and Optical Physics},

volume = {89},

number = {1},

abstract = {By using a modulated magnetic field in a Feshbach resonance for ultracold fermionic atoms in optical lattices, we show that it is possible to engineer a class of models usually referred to as correlated-hopping models. These models differ from the Hubbard model in exhibiting additional density-dependent interaction terms that affect the hopping processes. In addition to the spin-SU(2) symmetry, they also possess a charge-SU(2) symmetry, which opens the possibility of investigating the η-pairing mechanism for superconductivity introduced by Yang for the Hubbard model. We discuss the known solution of the model in one dimension (where η states have been found in the degenerate manifold of the ground state) and show that, away from the integrable point, quantum Monte Carlo simulations at half filling predict the emergence of a phase with coexisting incommensurate spin and charge order. © 2014 American Physical Society.},

note = {arXiv: 1310.7959},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{di_liberto_controlling_2014,

title = {Controlling coherence via tuning of the population imbalance in a bipartite optical lattice},

author = {M. Di_Liberto and T. Comparin and T. Kock and M. Ölschläger and A. Hemmerich and C. Morais Smith},

doi = {10.1038/ncomms6735},

issn = {20411723},

year  = {2014},

date = {2014-01-01},

urldate = {2014-01-01},

journal = {Nature Communications},

volume = {5},

abstract = {The control of transport properties is a key tool at the basis of many technologically relevant effects in condensed matter. The clean and precisely controlled environment of ultracold atoms in optical lattices allows one to prepare simplified but instructive models, which can help to better understand the underlying physical mechanisms. Here we show that by tuning a structural deformation of the unit cell in a bipartite optical lattice, one can induce a phase transition from a superfluid into various Mott insulating phases forming a shell structure in the superimposed harmonic trap. The Mott shells are identified via characteristic features in the visibility of Bragg maxima in momentum spectra. The experimental findings are explained by Gutzwiller mean-field and quantum Monte Carlo calculations. Our system bears similarities with the loss of coherence in cuprate superconductors, known to be associated with the doping-induced buckling of the oxygen octahedra surrounding the copper sites.},

note = {Publisher: Nature Publishing Group},

keywords = {},

pubstate = {published},

tppubtype = {article}

}