Publications

Order by: publication date number of citations

• A general learning scheme for classical and quantum Ising machines

  Ludwig Schmid, Enrico Zardini, Davide Pastorello

  SciPost Phys. Core 7, 013 (2024) · published 14 March 2024 | Toggle abstract · pdf

  An Ising machine is any hardware specifically designed for finding the ground state of the Ising model. Relevant examples are coherent Ising machines and quantum annealers. In this paper, we propose a new machine learning model that is based on the Ising structure and can be efficiently trained using gradient descent. We provide a mathematical characterization of the training process, which is based upon optimizing a loss function whose partial derivatives are not explicitly calculated but estimated by the Ising machine itself. Moreover, we present some experimental results on the training and execution of the proposed learning model. These results point out new possibilities offered by Ising machines for different learning tasks. In particular, in the quantum realm, the quantum resources are used for both the execution and the training of the model, providing a promising perspective in quantum machine learning.

  3 citations

• Non-collinear magnetic structures in the magnetoelectric Swedenborgite CaBaFe4O7 derived by powder and single-crystal neutron diffraction

  N. Qureshi, B. Ouladdiaf, A. Senyshyn, V. Caignaert, M. Valldor

  SciPost Phys. Core 5, 007 (2022) · published 3 February 2022 | Toggle abstract · pdf

  We have investigated the magnetic structures of the Swedenborgite compound CaBaFe4O7 using magnetic susceptibility and neutron diffraction experiments on powder and single-crystal samples. Below TN1 = 274 K the system orders in a ferrimagnetic structure with spins along the c axis and an additional antiferromagnetic component within the kagome plane which obviously cannot satisfy all exchange interactions. Competing single-ion anisotropy and exchange interactions lead to a transition into a multi-q conical structure at TN2 = 202 K. The derivation of the complex ordering scheme below TN2 is an important step towards the understanding of the magnetoelectric effect under magnetic fields in this polar ferrimagnet.

  3 citations

• Comparative analysis of tight-binding models for transition metal dichalcogenides

  Bert Jorissen, Lucian Covaci, Bart Partoens

  SciPost Phys. Core 7, 004 (2024) · published 6 February 2024 | Toggle abstract · pdf

  We provide a comprehensive analysis of the prominent tight-binding (TB) models for transition metal dichalcogenides (TMDs) available in the literature. We inspect the construction of these TB models, discuss their parameterization used and conduct a thorough comparison of their effectiveness in capturing important electronic properties. Based on these insights, we propose a novel TB model for TMDs designed for enhanced computational efficiency. Utilizing $MoS_2$ as a representative case, we explain why specific models offer a more accurate description. Our primary aim is to assist researchers in choosing the most appropriate TB model for their calculations on TMDs.

  3 citations

• Neural network quantum states analysis of the Shastry-Sutherland model

  Matěj Mezera, Jana Menšíková, Pavel Baláž, Martin Žonda

  SciPost Phys. Core 6, 088 (2023) · published 22 December 2023 | Toggle abstract · pdf

  We utilize neural network quantum states (NQS) to investigate the ground state properties of the Heisenberg model on a Shastry-Sutherland lattice using the variational Monte Carlo method. We show that already relatively simple NQSs can be used to approximate the ground state of this model in its different phases and regimes. We first compare several types of NQSs with each other on small lattices and benchmark their variational energies against the exact diagonalization results. We argue that when precision, generality, and computational costs are taken into account, a good choice for addressing larger systems is a shallow restricted Boltzmann machine NQS. We then show that such NQS can describe the main phases of the model in zero magnetic field. Moreover, NQS based on a restricted Boltzmann machine correctly describes the intriguing plateaus forming in magnetization of the model as a function of increasing magnetic field.

  3 citations

• Unconventional superconductivity in a strongly correlated band-insulator without doping

  Anwesha Chattopadhyay, H. R. Krishnamurthy, Arti Garg

  SciPost Phys. Core 4, 009 (2021) · published 28 April 2021 | Toggle abstract · pdf

  We present a novel route for attaining unconventional superconductivity in a strongly correlated system without doping. In a simple model of a correlated band insulator at half-filling we demonstrate, based on a generalization of the projected wavefunctions method, that superconductivity emerges for a broad range of model parameters when e-e interactions and the bare band-gap are both much larger than the kinetic energy, provided the system has sufficient frustration against the magnetic order. As the interactions are tuned, the superconducting phase appears sandwiched between the correlated band insulator followed by a paramagnetic metal on one side, and a ferrimagnetic metal, antiferromagnetic half-metal, and Mott insulator phases on the other side

  3 citations

• Identifying diffusive length scales in one-dimensional Bose gases

  Frederik Møller, Federica Cataldini, Jörg Schmiedmayer

  SciPost Phys. Core 7, 025 (2024) · published 7 May 2024 | Toggle abstract · pdf

  In the hydrodynamics of integrable models, diffusion is a subleading correction to ballistic propagation. Here we quantify the diffusive contribution for one-dimensional Bose gases and find it most influential in the crossover between the main thermodynamic regimes of the gas. Analysing the experimentally measured dynamics of a single density mode, we find diffusion to be relevant only for high wavelength excitations. Instead, the observed relaxation is solely caused by a ballistically driven dephasing process, whose time scale is related to the phonon lifetime of the system and is thus useful to evaluate the applicability of the phonon bases typically used in quantum field simulators.

  3 citations

• Rapidity distribution within the defocusing non-linear Schrödinger equation model

  Yasser Bezzaz, Léa Dubois, Isabelle Bouchoule

  SciPost Phys. Core 6, 064 (2023) · published 26 September 2023 | Toggle abstract · pdf

  We consider the classical field integrable system whose evolution equation is the nonlinear Schrödinger equation with defocusing non-linearities, which is the classical limit of the quantum Lieb-Liniger model. We propose a simple derivation of the relation between two sets of conserved quantities: on the one hand the trace of the monodromy matrix, parameterized by the spectral parameter and introduced in the inverse-scattering framework, and on the other hand the rapidity distribution, a concept imported from the Lieb-Liniger model. To do so we use the definition of the rapidity distribution as the asymptotic momentum distribution after a very large expansion. We propose two different ways to derive the result, each one using a thought experiment that implements an expansion.

  3 citations

• Predicting quantum potentials by deep neural network and metropolis sampling

  Rui Hong, Peng-Fei Zhou, Bin Xi, Jie Hu, An-Chun Ji, Shi-Ju Ran

  SciPost Phys. Core 4, 022 (2021) · published 13 September 2021 | Toggle abstract · pdf

  The hybridizations of machine learning and quantum physics have caused essential impacts to the methodology in both fields. Inspired by quantum potential neural network, we here propose to solve the potential in the Schrodinger equation provided the eigenstate, by combining Metropolis sampling with deep neural network, which we dub as Metropolis potential neural network (MPNN). A loss function is proposed to explicitly involve the energy in the optimization for its accurate evaluation. Benchmarking on the harmonic oscillator and hydrogen atom, MPNN shows excellent accuracy and stability on predicting not just the potential to satisfy the Schrodinger equation, but also the eigen-energy. Our proposal could be potentially applied to the ab-initio simulations, and to inversely solving other partial differential equations in physics and beyond.

  3 citations

• Out-of-equilibrium dynamics of two interacting optically-trapped particles

  Victor S. Dotsenko, Alberto Imparato, Pascal Viot, Gleb Oshanin

  SciPost Phys. Core 6, 056 (2023) · published 17 August 2023 | Toggle abstract · pdf

  We present a theoretical analysis of a non-equilibrium dynamics in a model system consisting of two particles which move randomly on a plane. The two particles interact via a harmonic potential, experience their own (independent from each other) noises characterized by two different temperatures $T_1$ and $T_2$, and each particle is being held by its own optical tweezer. Such a system with two particles coupled by hydrodynamic interactions was previously realised experimentally in Bérut et al. [EPL 107, 60004 (2014)], and the difference between two temperatures has been achieved by exerting an additional noise on either of the tweezers. Framing the dynamics in terms of two coupled over-damped Langevin equations, we show that the system reaches a non-equilibrium steady-state with non-zero (for $T_1 \neq T_2$) probability currents that possess non-zero curls. As a consequence, in this system the particles are continuously spinning around their centers of mass in a completely synchronized way - the curls of currents at the instantaneous positions of two particles have the same magnitude and sign. Moreover, we demonstrate that the components of currents of two particles are strongly correlated and undergo a rotational motion along closed elliptic orbits.

  3 citations

• On the complex structure of Yang-Mills theory

  Jan Horak, Jan M. Pawlowski, Nicolas Wink

  SciPost Phys. Core 8, 048 (2025) · published 7 July 2025 | Toggle abstract · pdf

  We consider the coupled set of spectral Dyson-Schwinger equations in Yang-Mills theory for ghost and gluon propagators. Within this set-up, we perform a systematic analytic evaluation of the constraints on generalised spectral representations in Yang-Mills theory that are most relevant for informed spectral reconstructions. Furthermore, we provide numerical results for the coupled set of ghost and gluon spectral functions for a range of potential mass gaps of the gluon, while allowing for small violations of the spectral representation. The analyses are accompanied by thorough discussion of the limitations and extensions of the present work.

  3 citations