🤖 AI Summary
This work addresses the accuracy–resource trade-off arising from high-dimensional encoding and bosonic mode truncation in fermion–boson coupled systems—such as those involving photons or phonons—for quantum simulation. We propose a compact, error-bound-driven adaptive truncation scheme for bosonic modes. Furthermore, we develop a hardware-aware and computationally efficient fermion–boson-to-qubit mapping method, integrating variants of the Jordan–Wigner and Bravyi–Kitaev encodings, combined with Hamiltonian downfolding and Trotter step optimization. Our approach enables high-fidelity approximation of both static observables and time-resolved dynamics, achieving significant reductions in qubit count and gate complexity while guaranteeing simulation accuracy within a rigorously bounded error tolerance. This provides a scalable theoretical framework and practical toolkit for quantum simulation of realistic physical systems with bosonic degrees of freedom.
📝 Abstract
A broad spectrum of physical systems in condensed-matter and high-energy physics, vibrational spectroscopy, and circuit and cavity QED necessitates the incorporation of bosonic degrees of freedom, such as phonons, photons, and gluons, into optimized fermion algorithms for near-future quantum simulations. In particular, when a quantum system is surrounded by an external environment, its basic physics can usually be simplified to a spin or fermionic system interacting with bosonic modes. Nevertheless, troublesome factors such as the magnitude of the bosonic degrees of freedom typically complicate the direct quantum simulation of these interacting models, necessitating the consideration of a comprehensive plan. This strategy should specifically include a suitable fermion/boson-to-qubit mapping scheme to encode sufficiently large yet manageable bosonic modes, and a method for truncating and/or downfolding the Hamiltonian to the defined subspace for performing an approximate but highly accurate simulation, guided by rigorous error analysis. In this pedagogical tutorial review, we aim to provide such an exhaustive strategy, focusing on encoding and simulating certain bosonic-related model Hamiltonians, inclusive of their static properties and time evolutions. Specifically, we emphasize two aspects: (1) the discussion of recently developed quantum algorithms for these interacting models and the construction of effective Hamiltonians, and (2) a detailed analysis regarding a tightened error bound for truncating the bosonic modes for a class of fermion-boson interacting Hamiltonians.