Abstract
We present a time-resolved digital quantum simulation of cosmological particle creation in a de~Sitter--radiation FLRW transition. Instead of compiling only the final Bogoliubov transformation into a one-shot circuit, we discretize the conformal-time evolution and implement the dynamics as a Trotterized sequence of short-time circuit blocks. This formulation gives access not only to the late-time particle number, but also to the build-up of fixed-basis pair occupation during the non-adiabatic transition. Using a four-qubit single-excitation encoding for a momentum pair (+k,-k), we compare matrix-Trotter evolution, noiseless statevector simulation, finite-shot Qiskit Aer simulation, and a shallow N=1 IBM hardware implementation. The simulator results are consistent with the analytic sudden-transition benchmark n_k=1/[4(kη_e)⁴] in the controlled single-excitation regime. The IBM experiment demonstrates execution of the shallow circuit block, but exhibits a residual hardware error of order 10⁻², indicating that quantitative hardware reconstruction of the particle spectrum remains beyond current NISQ performance.