Publications old

@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}

}

@article{di_liberto_finite-momentum_2011,

title = {Finite-momentum Bose-Einstein condensates in shaken two-dimensional square optical lattices},

author = {M. Di_Liberto and O. Tieleman and V. Branchina and C. Morais Smith},

doi = {10.1103/PhysRevA.84.013607},

issn = {10502947},

year  = {2011},

date = {2011-07-01},

urldate = {2011-07-01},

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

volume = {84},

number = {1},

abstract = {We consider ultracold bosons in a two-dimensional square optical lattice described by the Bose-Hubbard model. In addition, an external time-dependent sinusoidal force is applied to the system, which shakes the lattice along one of the diagonals. The effect of the shaking is to renormalize the nearest-neighbor-hopping coefficients, which can be arbitrarily reduced, can vanish, or can even change sign, depending on the shaking parameter. Therefore, it is necessary to account for higher-order-hopping terms, which are renormalized differently by the shaking, and to introduce anisotropy into the problem. We show that the competition between these different hopping terms leads to finite-momentum condensates with a momentum that may be tuned via the strength of the shaking. We calculate the boundaries between the Mott insulator and the different superfluid phases and present the time-of-flight images expected to be observed experimentally. Our results open up possibilities for the realization of bosonic analogs of the Fulde, Ferrel, Larkin, and Ovchinnikov phase describing inhomogeneous superconductivity. © 2011 American Physical Society.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{branchina_mapping_2010,

title = {Mapping fermion and boson systems onto the Fock space of harmonic oscillators},

author = {Vincenzo Branchina and Marco Di_Liberto and Ivano Lodato},

doi = {10.1103/PhysRevE.81.011120},

issn = {15393755},

year  = {2010},

date = {2010-01-01},

urldate = {2010-01-01},

journal = {Physical Review E - Statistical, Nonlinear, and Soft Matter Physics},

volume = {81},

number = {1},

abstract = {The fluctuation-dissipation theorem (FDT) is very general and applies to a broad variety of different physical phenomena in condensed matter physics. With the help of the FDT and following the famous work of Caldeira and Leggett, we show that, whenever linear response theory applies, any generic bosonic or fermionic system at finite temperature T can be mapped onto a fictitious system of free-harmonic oscillators. To the best of our knowledge, this is the first time that such a mapping is explicitly worked out. This finding provides further theoretical support to the phenomenological harmonic oscillator models commonly used in condensed matter. Moreover, our result helps in clarifying an interpretation issue related to the presence and physical origin of the Bose-Einstein factor in the FDT. © 2010 The American Physical Society.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{branchina_dark_2009,

title = {Dark energy and Josephson junctions},

author = {Vincenzo Branchina and Marco Di_Liberto and Ivano Lodato},

doi = {10.1088/1475-7516/2009/08/011},

issn = {14757516},

year  = {2009},

date = {2009-01-01},

urldate = {2009-01-01},

journal = {Journal of Cosmology and Astroparticle Physics},

volume = {2009},

number = {8},

abstract = {It has been recently claimed that dark energy can be (and has been) observed in laboratory experiments by measuring the power spectrum S I(ω) of the noise current in a resistively shunted Josephson junction and that in new dedicated experiments, which will soon test a higher frequency range, S I(ω) should show a deviation from the linear rising observed in the lower frequency region because higher frequencies should not contribute to dark energy. Based on previous work on theoretical aspects of the fluctuation-dissipation theorem, we carefully investigate these issues and show that these claims are based on a misunderstanding of the physical origin of the spectral function S I(ω). According to our analysis, dark energy has never been (and will never be) observed in Josephson junctions experiments. We also predict that no deviation from the linear rising behavior of S I(ω) will be observed in forthcoming experiments. Our findings provide new (we believe definite) arguments which strongly support previous criticisms. © 2009 IOP Publishing Ltd and SISSA.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Zuliani2021,

title = {SUPP INF: Quantum-inspired Machine Learning on high-energy physics data},

author = {Davide Zuliani and Timo Felser and Marco Trenti and Lorenzo Sestini and Alessio Gianelle and Donatella Lucchesi and Simone Montangero},

pages = {931},

abstract = {One of the most challenging big data problems in high energy physics is the analysis and classification of the data produced by the Large Hadron Collider at CERN. Recently, machine learning techniques have been employed to tackle such challenges, which, despite being very effective, rely on classification schemes that are hard to interpret. Here, we introduce and apply a quantum-inspired machine learning technique and, exploiting tree tensor networks, we show how to efficiently classify b-jet events in proton-proton collisions at LHCb and to interpret the classification results. In particular, we show how to select important features and adapt the network geometry based on information acquired in the learning process. Moreover, the tree tensor network can be adapted for optimal precision or fast response in time without the need for repeating the learning process. This paves the way to high-frequency real-time applications as needed for current and future LHC event classification to trigger events at the tens of MHz scale.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Arceci2022a,

title = {Supplemntary material: Entanglement of Formation of Mixed Many-Body Quantum States via Tree Tensor Operators},

author = {L. Arceci and Pietro Silvi and Simone Montangero},

pages = {1–20},

keywords = {},

pubstate = {published},

tppubtype = {article}

}