Quantum-Compute Algorithm for Exact Laser-Driven Electron Dynamics in Molecules

Abstract

In this work, we investigate the capability of known quantum computing algorithms for fault-tolerant quantum computing to simulate the laser-driven electron dynamics of excitation and ionization processes in small molecules such as lithium hydride, which can be benchmarked against the most accurate time-dependent full configuration interaction (TD-FCI) calculations. The conventional TD-FCI wave packet propagation is reproduced using the Jordan−Wigner transformation for wave function and operators and the Trotter product formula for expressing the propagator. In addition, the time-dependent dipole moment, as an example of a time-dependent expectation value, is calculated using the Hadamard test. To include non-Hermitian operators in the ionization dynamics, a similar approach to the quantum imaginary time evolution (QITE) algorithm is employed to translate the propagator, including a complex absorption potential, into quantum gates. The computations are executed on a quantum computer simulator. By construction, all quantum computer algorithms, except for the QITE algorithm used only for ionization but not for excitation dynamics, would scale polynomially on a quantum computer with fully entangled qubits. In contrast, TD-FCI scales exponentially. Hence, quantum computation holds promises for substantial progress in the understanding of electron dynamics of excitation processes in increasingly large molecular systems, as has already been witnessed in electronic structure theory.

Jellyfish: A modular code for wave function‐based electron dynamics simulations and visualizations on traditional and quantum compute architectures

“…Additionally to the above outlined traditional way of simulating TDCI dynamics, Jellyfish also was used to develop algorithms for quantum computing. 55 Quantum computing promises for great advancement in electronic structure theory [56][57][58] as well as quantum dynamics. 59 Likewise, the field of electron dynamics would benefit from quantum computers and would make exact calculations in much larger molecules finally feasible.…”

“…Additionally to the above outlined traditional way of simulating TDCI dynamics, Jellyfish also was used to develop algorithms for quantum computing 55 . Quantum computing promises for great advancement in electronic structure theory 56–58 as well as quantum dynamics 59 .…”

“…Time-dependent expectation values can be determined with the help of a module for the Hadamard test. 65 More information about the complete algorithm developed with it can be found in Langkabel et al 55 4 | EXAMPLE APPLICATIONS…”

“…The time‐dependent NTOs show the formation of hole and particle in terms of the rising population in the excited states, cf., Figure 6 Thus, the NTOs are essentially excited state quantities/properties, since they are calculated with the ground state contributions are being removed to ensure orthogonality during time propagations (cf., Ref. 55).…”

Noise‐Based Damping of Chaotic Entanglement in Pulsed Driven Two‐Qubit System

“…Careful quantification of environment-induced decoherence mechanisms and pulse engineering of entanglement may advance quantum control capabilities for emerging quantum systems. Laser pulse-driven quantum dynamics enables unprecedented control and manipulation of quantum systems, with broad applications across quantum optics, [42] information science, [43] and materials research. [44] This paper is structured as follows: In Section 2, we describe the physical system under study-a pair of two-level quantum bits (qubits) subjected to pulsed laser excitation modeled by a sinusoidal squared envelope.…”