フェルミの「黄金律」を利用する新しい理論設計を提案（’Check your ingredients’: A new blueprint for using Fermi’s ‘Golden Rule’）

2026-07-09 イェール大学

＜関連情報＞

• https://news.yale.edu/2026/07/09/check-your-ingredients-new-blueprint-using-fermis-golden-rule
• https://www.nature.com/articles/s41567-026-03316-1

量子多体システムにおけるフェルミの黄金律の出現 Emergence of Fermi’s golden rule in a quantum many-body system

Jianyi Chen,Songtao Huang,Yunpeng Ji,Grant L. Schumacher,Alan Tsidilkovski,Alexander Schuckert,Gabriel G. T. Assumpção & Nir Navon
Nature Physics  Published:09 July 2026
DOI:https://doi.org/10.1038/s41567-026-03316-1

Abstract

Fermi’s golden rule links certain measurable observables—such as transition rates—to fundamental microscopic properties such as the density of states or spectral functions. Understanding the regime of validity of Fermi’s golden rule is critical for the proper interpretation of spectroscopic experiments. Although its assumptions are straightforward in simple models, assessing their validity in quantum many-body systems remains difficult. Here we demonstrate the emergence and breakdown of Fermi’s golden rule in a strongly interacting homogeneous spin-1/2 Fermi gas coupled to a radio-frequency field. By measuring the transition probability into an outcoupled internal state, we map the system’s dynamical response diagram as a function of pulse duration t and probe coupling strength. For weak drives, we identify an early time regime where the transition probability takes off as t², an intermediate-time regime consistent with Fermi’s golden rule regime and a long-time non-perturbative regime. Beyond a threshold coupling strength, Rabi oscillations appear. Our results provide a blueprint for the applicability of linear response theory to the spectroscopy of quantum many-body systems.