Quantum simulations of ultrafast optical spectroscopy of semiconductors on digital quantum computers in the semi-classical approximation

We present a digital quantum simulation framework for ultrafast optical spectroscopy of semiconductor materials. The framework is based on Brillouin-zone discretization and the second-quantization formalism, and is designed as a quantum alternative to classical simulations based on the semiconductor Bloch equations. Its current capabilities include quantum simulations of linear absorption and optical gain spectra, incorporating Lorentzian broadening, finite-temperature band-filling effects, and reduced-dimensionality effects. Benchmark comparisons with classical simulations for GaAs demonstrate quantitative agreement in the noiseless limit. The inclusion of realistic hardware noise of NISQ-era quantum computers effectively manifests itself as an additional source of scattering processes, resulting in increased spectral broadening. While no exponential quantum advantage is expected in the single-particle approximation, the framework naturally extends to many-body regimes where classical simulations face the hierarchy problem and exponential scaling and provable quantum advantage will be possible. The quantum simulations considered in this work capture central elements of semiconductor spectroscopy, the aspects such as open quantum systems, light-matter interactions, statistical mechanics, non-equilibrium quantum dynamics, and many-body physics. As such, it provides a physically motivated and scalable model for benchmarking quantum computers in applications to complex, real-world problems.