Quantum Simulation of the Polaron-Molecule Transition on a NISQ Device

Abstract: The simulation of strongly correlated fermionic systems remains one of the most significant challenges in computational physics due to the exponential growth of the Hilbert space and the fermionic sign problem. In this work, we present a digital quantum simulation framework to explore the Fermi polaron and the Bose-Einstein Condensate (BEC) to Bardeen-Cooper-Schrieffer (BCS) crossover. We develop a unified Hamiltonian formalism that bridges pairing superfluidity and impurity physics, mapping the system onto a gate-based quantum processor via the Jordan-Wigner transformation. Using a first-order Trotter-Suzuki decomposition, we implement a Ramsey interferometry protocol to extract the real-time dynamics and spectral response of the system. Our results demonstrate a smooth transition from a dressed quasiparticle (polaron) regime to a stable molecular bound state, characterized by a linear energy renormalization in the strong-coupling limit. We validate our simulation against exact classical benchmarks and report successful execution on the Barcelona Supercomputing Center quantum hardware. Despite the inherent noise of the quantum hardware, the hybrid variational approach shows remarkable resilience, accurately capturing the bifurcation of the spectral density