Publications

Order by: publication date number of citations

• Efficient qudit based scheme for photonic quantum computing

  Márton Karácsony, László Oroszlány, Zoltan Zimboras

  SciPost Phys. Core 7, 032 (2024) · published 3 June 2024 | Toggle abstract · pdf

  Linear optics is a promising alternative for the realization of quantum computation protocols due to the recent advancements in integrated photonic technology. In this context, usually qubit based quantum circuits are considered, however, photonic systems naturally allow also for d-ary, i.e., qudit based, algorithms. This work investigates qudits defined by the possible photon number states of a single photon in d > 2 optical modes. We demonstrate how to construct locally optimal non-deterministic many-qudit gates using linear optics and photon number resolving detectors, and explore the use of qudit cluster states in the context of a d-ary optimization problem. We find that the qudit cluster states require less optical modes and are encoded by a fewer number of entangled photons than the qubit cluster states with similar computational capabilities. We illustrate the benefit of our qudit scheme by applying it to the k-coloring problem.

  3 citations

• Future Physics Prospects with the CMS Detector at the High-Luminosity LHC

  Conor Henderson

  SciPost Phys. Proc. 8, 111 (2022) · published 13 July 2022 | Toggle abstract · pdf

  The High-Luminosity Large Hadron Collider is expected to deliver up to 3000 fb$^{-1}$ of proton-proton collisions at 14 TeV center-of-mass energy. We present prospects for selected heavy-ion, Standard Model and Higgs sector measurements with the CMS detector at the HL-LHC, and discuss potential sensitivity to several beyond-Standard Model new physics scenarios.

  3 citations

• Weak topological insulating phases of hard-core-bosons on the honeycomb lattice

  Amrita Ghosh, Eytan Grosfeld

  SciPost Phys. 10, 059 (2021) · published 9 March 2021 | Toggle abstract · pdf

  We study the phases of hard-core-bosons on a two-dimensional periodic honeycomb lattice in the presence of an on-site potential with alternating sign along the different y-layers of the lattice. Using quantum Monte Carlo simulations supported by analytical calculations, we identify a weak topological insulator, characterized by a zero Chern number but non-zero Berry phase, which is manifested at either density 1/4 or 3/4, as determined by the potential pattern. Additionally, a charge-density-wave insulator is observed at 1/2-filling, whereas the phase diagram at intermediate densities is occupied by a superfluid phase. The weak topological insulator is further shown to be robust against any amount of nearest-neighbor repulsion, as well as weak next-nearest-neighbor repulsion. The experimental realization of our model is feasible in an optical lattice setup.

  3 citations

• Magnetic properties of the putative higher-order topological insulator EuIn$_2$As$_2$

  Tomasz Toliński, Dariusz Kaczorowski

  SciPost Phys. Proc. 11, 005 (2023) · published 5 June 2023 | Toggle abstract · pdf

  In higher-order topological insulator (HOTI), a gap is preserved both for the bulk and the surface states, and only hinges or corners become gapless. Recently, it has been predicted that the antiferromagnetic compound EuIn$_2$As$_2$ can host both the HOTI and axion insulator features. Preliminary experimental confirmation of this finding was obtained using angle-resolved photoemission spectroscopy. The main objective of this work was to characterize the anisotropic magnetic properties of single-crystalline EuIn$_2$As$_2$. In addition, complementary studies on the transport properties, heat capacity, and magnetocaloric effect in this compound were performed.

  3 citations

• Quantum annealing for neural network optimization problems: A new approach via tensor network simulations

  Guglielmo Lami, Pietro Torta, Giuseppe E. Santoro, Mario Collura

  SciPost Phys. 14, 117 (2023) · published 17 May 2023 | Toggle abstract · pdf

  Here, we focus on the problem of minimizing complex classical cost functions associated with prototypical discrete neural networks, specifically the paradigmatic Hopfield model and binary perceptron. We show that the adiabatic time evolution of QA can be efficiently represented as a suitable Tensor Network. This representation allows for simple classical simulations, well-beyond small sizes amenable to exact diagonalization techniques. We show that the optimized state, expressed as a Matrix Product State (MPS), can be recast into a Quantum Circuit, whose depth scales only linearly with the system size and quadratically with the MPS bond dimension. This may represent a valuable starting point allowing for further circuit optimization on near-term quantum devices.

  3 citations

• Jet modifications from colour rope formation in dense systems of non-parallel strings

  Christian Bierlich, Smita Chakraborty, Gösta Gustafson, Leif Lönnblad

  SciPost Phys. 13, 023 (2022) · published 17 August 2022 | Toggle abstract · pdf

  We revisit our rope model for string fragmentation that has been shown to give a reasonable description of strangeness and baryon enhancement in high-multiplicity pp events at the LHC. A key feature of the model is that the enhancement is driven by the increased string tension due to strings overlapping in dense systems. By introducing an improved space-time picture for the overlap between fragmenting strings, where also non-parallel strings are properly taken into account, we are now able to investigate the enhancement both in jets and in the underlying event in a consistent way.

  3 citations

• 2D topological matter from a boundary Green's functions perspective: Faddeev-LeVerrier algorithm implementation

  Miguel Alvarado, Alfredo Levy Yeyati

  SciPost Phys. 13, 009 (2022) · published 25 July 2022 | Toggle abstract · pdf

  Since the breakthrough of twistronics a plethora of topological phenomena in correlated systems has appeared. These devices can be typically analyzed in terms of lattice models using Green's function techniques. In this work we introduce a general method to obtain the boundary Green's function of such models taking advantage of the numerical Faddeev-LeVerrier algorithm to circumvent some analytical constraints of previous works. We illustrate our formalism analyzing the edge features of a Chern insulator, the Kitaev square lattice model for a topological superconductor and the Checkerboard lattice hosting topological flat bands. The efficiency and accuracy of the method is demonstrated by comparison to standard recursive Green's function calculations and direct diagonalizations.

  3 citations

• All Jordanian deformations of the $AdS_5 \times S^5$ superstring

  Riccardo Borsato, Sibylle Driezen

  SciPost Phys. 14, 160 (2023) · published 19 June 2023 | Toggle abstract · pdf

  We explicitly construct and classify all Jordanian solutions of the classical Yang-Baxter equation on $\mathfrak{psu}(2,2|4)$, corresponding to Jordanian Yang-Baxter deformations of the $AdS_5\times S^5$ superstring. Such deformations preserve the classical integrability of the underlying sigma-model and thus are a subclass of all possible integrable deformations. The deformations that we consider are divided into two families, unimodular and non-unimodular ones. The former ensure that the deformed backgrounds are still solutions of the type IIB supergravity equations. For the simplest unimodular solutions, we find that the corresponding backgrounds preserve a number $N<32$ of supercharges that can be $N=12,8,6,4,0$.

  3 citations

• Semiconductor electron-phonon equations: A rung above Boltzmann in the many-body ladder

  Gianluca Stefanucci, Enrico Perfetto

  SciPost Phys. 16, 073 (2024) · published 13 March 2024 | Toggle abstract · pdf

  Starting from the ab initio many-body theory of electrons and phonons, we go through a series of well defined simplifications to derive a set of coupled equations of motion for the electronic occupations and polarizations, nuclear displacements as well as phononic occupations and coherences. These are the semiconductor electron-phonon equations (SEPE), sharing the same scaling with system size and propagation time as the Boltzmann equations. At the core of the SEPE is the mirrored Generalized Kadanoff-Baym Ansatz (GKBA) for the Green's functions, an alternative to the standard GKBA which we show to lead to unstable equilibrium states. The SEPE treat coherent and incoherent degrees of freedom on equal footing, widen the scope of the semiconductor Bloch equations and Boltzmann equations, and reduce to them under additional simplifications. The new features of the SEPE pave the way for first-principles studies of phonon squeezed states and coherence effects in time-resolved absorption and diffraction experiments.

  3 citations

• On $\varepsilon$-factorised bases and pure Feynman integrals

  Hjalte Frellesvig, Stefan Weinzierl

  SciPost Phys. 16, 150 (2024) · published 6 June 2024 | Toggle abstract · pdf

  We investigate $\varepsilon$-factorised differential equations, uniform transcendental weight and purity for Feynman integrals. We are in particular interested in Feynman integrals beyond the ones which evaluate to multiple polylogarithms. We show that a $\varepsilon$-factorised differential equation does not necessarily lead to Feynman integrals of uniform transcendental weight. We also point out that a proposed definition of purity works locally, but not globally.

  3 citations