Preprint
Oct 2026
Quantum impurity models: easy at equilibrium, universal in motion
A quantum impurity model describes a small interacting subsystem embedded into a large bath of free fermions. Here we study the computational complexity of calculating the ground energy, thermal equilibrium, and dynamical properties of these models. Our work reveals a sharp contrast: equilibrium properties can be effic...
Srinivasan Arunachalam, S. Bravyi, Anirban Narayan Chowdhury et al.
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