Time-resolved digital quantum simulation of cosmological particle creation in a de Sitter-radiation transition

TL;DR

This paper demonstrates a time-resolved digital quantum simulation of cosmological particle creation during a de Sitter-radiation transition, analyzing the build-up of particle pairs with various simulation methods and a shallow quantum hardware implementation.

Contribution

It introduces a discretized, time-resolved quantum simulation approach for cosmological particle creation, enabling analysis of dynamics during non-adiabatic transitions.

Findings

Simulator results match the analytic sudden-transition benchmark.

IBM hardware executes shallow circuits but shows residual errors.

Quantitative hardware reconstruction of the particle spectrum is limited by current NISQ devices.

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 $(+\mathbf{k},-\mathbf{k})$, 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 $n_k=1/[4(k\eta_e)^4]$ 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.