Bosonic Hubbard-Holstein model and its realization in optical lattices

Kalani Hettiarachchilage, Valy Rousseau, Juana Moreno +1 more

J. P. Hague, P. E. Kornilovitch, C. MacCormick

We describe a quantum simulator for the Hubbard-Holstein model (HHM), comprising two dressed Rydberg atom species held in a monolayer by independent painted potentials, predicting that boson-mediated preformed pairing and Berezinskii-Kosterlitz-Thouless (BKT) transition temperatures are experimentally accessible. The HHM is important for modeling the essential physics of unconventional superconductors. Experimentally realizable quantum simulators for HHMs are needed (1) since HHMs are difficult to solve numerically and analytically, (2) to explore how competition between electron-phonon interactions and strong repulsion affects pairing in unconventional superconductors, and (3) to understand the role of boson-mediated local pairing in pseudogaps and fermion condensates. We propose and study a quantum simulator for the HHM, using optical lattices, painted using zeros in the ac Stark shift, to control two Rydberg atom species independently within a monolayer. We predict that interactions are sufficiently tunable to probe (1) both HHMs and highly unconventional phonon-mediated repulsions, (2) the competition between intermediate-strength phonon- and Coulomb-mediated interactions, and (3) BKT transitions and preformed pairing that could be used to examine key hypotheses related to the pseudogap. We discuss how the quantum simulator can be used to investigate boson-mediated pairing and condensation of fermions in unconventional superconductors.

S. L. Rolston

Steffen Backes, Yuta Murakami, 志朗 酒井 +1 more

Utilizing quantum computers for real materials calculations is highly promising, but hinges on qubit fidelity and fault-tolerant quantum algorithms. Here, the authors show that a representative model for real materials, the Hubbard-Holstein model, which describes interacting electrons on a lattice coupled to bosonic degrees of freedom, can be reliably investigated using today's Quantum processors. Adapting state-of-the-art mathematical tools is shown to be critical to overcome limitations imposed by the noise level of current quantum computing devices.

J. P. Kestner, Luming Duan

Barbara Capogrosso-Sansone

In this dissertation I present results for lattice boson systems based on quantum Monte Carlo simulations by the Worm algorithm. Lattice bosons can be realized by ultracold gases in optical lattices and, under certain conditions, they are described by the Bose-Hubbard model. I will discuss the ground state, i.e. the phase diagram and properties of elementary excitations, as well as finite temperature thermodynamic properties of the two- and three-dimensional systems. These results provide bench-marks and guidance for experimentalists. I will also discuss the phase diagram of the one-dimensional hard-core Bose-Hubbard model with three-body interactions. The model is realized by cold polar molecules in optical lattices. The ground state presents a novel solid phase at unconventional filling, characterized by coexisting charge density wave and bond orders. Such phase has not been predicted by the preexisting mean field theory.