The Donostia International Physics Center (DIPC) Foundation was established in 1999 in the framework of a collaboration agreement reached by the Education and Industry Departments of the Basque Government, the University of the Basque Country, the Regional Government of Gipuzkoa, the City of Donostia and the Kutxa savings bank. Iberdrola participated in the venture during 2000-2003. In 2004 Naturcorp Multiservicios joined the project, followed by Telefónica in 2005.The DIPC was born as an intellectual center aimed at fostering and providing for the development of highest level basic research in material science. Since its early days, the DIPC has been an open institution, bound to the University of the Basque Country, committed to the internationalization of all basic science engaged in the Basque Country related to physics and material science..
Electron tunneling through a potential barrier is a salient quantum effect behind multiple practical applications such as, for example, in electronics and scanning tunneling microscopy. Often considered within the quasistatic picture, where the tunneling current flows through the system in response to an applied dc field, electron tunneling can be brought into the realm of ultrafast phenomena when triggered by the electric field of a short optical pulse. Ultrafast scanning tunneling microscopy thus emerges as a result of the combination of the ultimate spatial and temporal resolution, offering unprecedented perspectives for studying electron and phonon dynamics at surfaces. In this work, using the time-dependent density-functional theory, we address the electron tunneling triggered by short (single-cycle and several-cycle) optical pulses in narrow metallic gaps under conditions relevant for actual experiments. We identify photon-assisted tunneling with one-photon, two-photon, and higher-order-photon absorption, and discuss the effect of the tunneling barrier, applied bias, and strength of the optical field on the transition from photon-assisted tunneling (weak optical fields) to the optical-field emission at strong optical fields. Numerical single-electron calculations and an analytical strong-field theory model are implemented to gain deeper insights into the results of the time-dependent density-functional theory calculations. Additionally, our parameter-free calculations allow us to retrieve and explain recent experimental results on optically induced transport in narrow metallic gaps under an applied dc bias.
We experimentally demonstrate that a digitized counterdiabatic quantum protocol reduces the number of topological defects created during a fast quench across a quantum phase transition. To show this, we perform quantum simulations of one- and two-dimensional transverse-field Ising models driven from the paramagnetic to the ferromagnetic phase. We utilize superconducting cloud-based quantum processors with up to 156 qubits. Our data reveal that the digitized counterdiabatic protocol reduces defect formation by up to 48% in the fast-quench regime-an improvement hard to achieve through digitized quantum annealing under current noise levels. The experimental results closely match theoretical and numerical predictions at short evolution times before deviating at longer times due to hardware noise. In one dimension, we derive an analytic solution for the defect number distribution in the fast-quench limit. For two-dimensional geometries, where analytical solutions are unknown and numerical simulations are challenging, we use advanced matrix product state methods. Our findings indicate a practical way to control topological defect formation during fast quenches and highlight the utility of counterdiabatic protocols for quantum optimization and quantum simulation in material design on current quantum processors.
The last two decades has seen quantum thermodynamics become a well established field of research in its own right. In that time, it has demonstrated a remarkably broad applicability, ranging from providing foundational advances in the understanding of how thermodynamic principles apply at the nano-scale and in the presence of quantum coherence, to providing a guiding framework for the development of efficient quantum devices. Exquisite levels of control have allowed state-of-the-art experimental platforms to explore energetics and thermodynamics at the smallest scales which has in turn helped to drive theoretical advances. This Roadmap provides an overview of the recent developments across many of the field's sub-disciplines, assessing the key challenges and future prospects, providing a guide for its near term progress.
We investigate the roughening transition of an electric flux string between two static charges in a $${{\mathbb{Z}}}_{2}$$ lattice gauge theory in (2+1) dimensions. This transition is compelling because of its relation to the continuum limit. However, the entanglement growth makes it harder to access it computationally. Using numerical simulations with matrix product states, we explore the static and dynamical properties of an electric string in the confined and deconfined phases. Within the roughening region, we obtain the universal Lüscher correction to the confining potential and observe the restoration of rotational symmetry. Our simulations of the out-of-equilibrium evolution of a string reveal that the growth of the entanglement entropy of the state and the string width exhibit qualitatively different behaviors in the roughening region compared to the strongly confined one. Eventually, we find that the rate of entropy growth is consistent with an effective description of the string excitations in the roughening phase as a bosonic model. The roughening transition in Z2 lattice gauge theory remains a complex phenomenon, particularly in understanding the behavior of electric flux strings. Here, the authors use numerical simulations with matrix product states to reveal the universal Lüscher correction and distinct entanglement entropy growth, offering insights into string dynamics and symmetry restoration near deconfinement.
Fractionally charged elementary excitations, the quasielectron and quasihole, are hallmarks of the fractional Chern insulator. We observe that spontaneous spin polarization in twisted MoTe_{2} leads to multiple species of low-energy quasiparticles distinguished by their spin quantum numbers. Through large-scale exact diagonalization calculations, we investigate the nature of these excitations and develop a method to extract their energetic properties. Focusing on θ=3.7° and filling factor ν=-2/3 relevant to recent experiments, we show that spin-preserving (spinless) charge excitations have smaller gap than spin-flipping (spinful) excitations with and without band mixing. This result is in qualitative agreement with the measured magnetic field dependence of the transport gaps. Beyond spinless and spinful quasiparticle gaps, we extract the full quasielectron and quasihole "band structure" and find significant dispersion with emergent magnetic translation symmetry-a fundamental departure from the immobile excitations of the quantum Hall fluid. Our work establishes a framework for computing the properties of elementary excitations in fractional Chern insulators.
