Ruihao Li (Cleveland Clinic Research)

Date: Mon. November 2nd, 2026, 12:45 pm-1:45 pm
Location: Foldy room (Rockefeller 221)
Website: https://scholar.google.com/citations?user=6rH6RpcAAAAJ&hl=en
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Title: Preparing Quantum Thermal States: Circuit Design and Local Certification

Speaker: Dr. Ruihao Li

Department of Computational Life Sciences, Cleveland Clinic Research

(Host: Shulei Zhang)

Abstract: Gibbs states encode the equilibrium properties of quantum many-body systems at finite temperature. Quantum Gibbs states encode both thermal populations and the many-body energy eigenstates that carry them, making their preparation a challenge involving both statistical and quantum structure. The focus of this talk is on tractable Gibbs-state preparation.

In the first part of the talk, I will introduce a variational Gibbs-state preparation workflow that leverages tensor-network assistance. Within a classically tractable regime, matrix-product-state calculations provide access to the energy and entropy of the purification-circuit ansätze, enabling their optimization before execution on quantum hardware. Through numerical benchmarks, I will discuss how circuit architecture, entropy capacity, and classical computational cost affect the resulting thermal-state approximations.

In the second part, I will turn to a complementary, structure-based perspective. I will introduce the spectral core–tail architecture, which combines a tractable thermal “core” carrying the thermal distribution with a “tail” circuit that transforms its basis. Starting from selected exactly solvable models, this framework guides the construction of preparation circuits and systematic corrections for suitable perturbations. Under appropriate locality and thermal-response assumptions, it translates the remaining Hamiltonian mismatch into volume-uniform bounds on errors in local thermal predictions.