Quantum Resource Assay for the Grid-Based Simulation of the Photodynamics of Pyrazine

TL;DR

This paper develops a fault-tolerant quantum algorithm for simulating the photodynamics of pyrazine, analyzing resource requirements and validating the approach through classical emulation, paving the way for larger molecular simulations.

Contribution

It introduces a comprehensive quantum algorithm framework for vibronic dynamics of pyrazine, including resource estimation and validation methods for high-dimensional molecular simulations.

Findings

Simulating low-dimensional pyrazine dynamics requires 17 qubits and $ ext{O}(10^5)$ gates.

Full-dimensional simulation in 24 modes needs 97 qubits and $ ext{O}(10^6)$ gates.

Classical emulations validate the quantum resource estimates.

Abstract

We establish and analyse the performance and resource requirements of an end-to-end fault-tolerant quantum algorithm for computing the absorption spectrum and population dynamics of photoexcited pyrazine. The quantum circuit construction consists of initial state preparation using uniformly controlled rotations, the time-dependent Hamiltonian propagation based on the grid-based Split Operator Quantum Fourier Transform (SO-QFT) method, and cost-effective measurements including statistical and canonical phase estimation. We use classical emulations to validate the quantum resources required for the task, and propose generalised formulae for the qubit count and gate depth calculation. Simulating the vibronic dynamics of pyrazine in a low-dimensional abstraction requires 17-qubit circuits with a gate depth of $\mathcal{O}(10^5)$, whereas a full-dimensional simulation of pyrazine in 24 modes requires at least 97-qubit circuits with a gate depth of $\mathcal{O}(10^6)$. Our work provides a foundational framework for understanding high-dimensional wavepacket-based quantum simulations of photo-induced dynamics and vibronic spectra, anticipating future applications in the simulation of even larger molecular systems on fault-tolerant quantum computers.