Rôle des corrélations de l’espace de Fock dans la localisation à plusieurs corps / Simulation quantique sur ordinateurs quantiques bruyants (NISQ). – (Thibault Scoquart / LPT / Seminar). – 10/12/2024, 14H

Séminaire LPT

Thibault Scoquart (Institut de technologie de Karlsruhe)

Seminar LPT, 10/12/2024, 14H, 3R4, salle de conférence

Summary :
In this seminar, I will discuss two (more or less) unrelated projects that I worked on during my postdoc at KIT.
In a first part, I will present our conclusions regarding the role of correlations of Fock-space matrix elements in ergodicity-to-Many-Body Localization (MBL) transitions [1]. To study this, we introduce five different disordered spin models and describe analytically and numerically the scaling of their finite-size critical disorder Wc(n) with the system size n. The MBL transition in these models can be seen as the Anderson localization problem for a fictitious particle hopping over their hypercube Fock space structure. The models are built such that they have the same distributions of diagonal (energy) and off-diagonal (hopping) Fock-space matrix elements but very different correlations. One of these models is a typical disordered 1D spin chain, paradigmatic for the study of MBL, and another is the quantum random energy model (QREM) with no Fock-space correlations at all, making it analytically more tractable. The three other models bridge the gap between these two extremes. A cross-comparison of Wc(n) for all five models demonstrates to which extent the scaling of the MBL transition is governed by a combined effect of Fock-space correlations of diagonal and off-diagonal matrix elements.
In a second part of the talk, I will give an overview of our work on digital quantum simulations performed on IBM superconducting quantum computers, one of the main current im- plementations of Noisy Intermediate-Scale Quantum computers (NISQ). The focus will be on our work about noise characterization, noise tailoring and error mitigation via quantum circuit sampling on such devices, using short-scale simulations of BCS dynamics as a benchmark [2, 3]. I will also discuss some perspectives on the quantum simulation of quenched thermalizing dynamics on NISQ [4].

[1] T. Scoquart, I. Gornyi and A. Mirlin, Role of Fock-space correlations in many-body localization, Physical Review B 109, 214203, (2024)

[2] H. Perrin, T. Scoquart, A. Shnirman, J. Schmalian, and K. Snizhko, Mitigating crosstalk errors by randomized compiling : Simulation of the BCS model on a superconducting quantum computer, Phys. Rev. Research 6, 013142 (2024)

[3] T. Scoquart, H. Perrin and K. Snizkho, Noise-tailoring for error mitigation on a digital quantum computer (Soon to appear on arXiv)

[4] H. Perrin, T. Scoquart, A. I. Pavlov, N. V. Gnezdilov, Dynamic thermalization on noisy quantum hardware, arXiv:2407.04770