Simulating open-system molecular dynamics on analog quantum computers

V. C. Olaya-Agudelo, Ben Stewart, Christophe H. Valahu +6 more

Interactions of molecules with their environment influence the course and outcome of almost all chemical reactions. However, classical computers struggle to accurately simulate complicated molecule-environment interactions because of the steep growth of computational resources with both molecule size and environment complexity. Therefore, many quantum-chemical simulations are restricted to isolated molecules, whose dynamics can dramatically differ from what happens in an environment. Here, we show that analog quantum simulators can simulate open molecular systems by using the native dissipation of the simulator and injecting additional controllable dissipation. By exploiting the native dissipation to simulate the molecular dissipation—rather than seeing it as a limitation—our approach enables longer simulations of open systems than are possible for closed systems. In particular, we show that trapped-ion simulators using a mixed qudit-boson (MQB) encoding could simulate molecules in a wide range of condensed phases by implementing widely used dissipative processes within the Lindblad formalism, including pure dephasing and both electronic and vibrational relaxation. The MQB open-system simulations require significantly fewer additional quantum resources compared to both classical and digital quantum approaches.

Bradley P. Feuston

Xiao Zheng

Igor O. Sokolov, Panagiotis Kl. Barkoutsos, Lukas Moeller +3 more

Ab initio molecular dynamics (AIMD) is a powerful tool to predict properties of molecular and condensed matter systems.However, the quality of this procedure relies on the availability of rigorous electronic structure calculations.The development of quantum processors has shown great potential for the efficient evaluation of accurate ground and excited state energies of molecular systems, opening up new avenues for molecular dynamics simulations.In this work, we address the use of variational quantum algorithms for the calculation of accurate atomic forces to be used in AIMD.In particular, we provide solutions for the alleviation of the statistical noise associated with the measurements of the expectation values of energies and forces, as well as schemes for the mitigation of the hardware noise sources (in particular, gate infidelities, qubit decoherence, and readout errors).Despite the relative large error in the calculation of the potential energy, our results show that the proposed algorithms can provide accurate MD trajectories in the microcanonical (constant energy) ensemble.Furthermore, exploiting the intrinsic noise associated to the quantum measurement process, we also propose a Langevin dynamics algorithm for the simulation of canonical, i.e., constant temperature, dynamics.Both algorithms (microcanonical and canonical) are applied to the simulation of simple molecular systems such as H 2 and H + 3 .Finally, we also provide results for the dynamics of H 2 obtained with IBM quantum computer ibmq_athens.

Jincheng Zhang

This paper explores the potential of a hybrid quantum-classical simulation approach to accelerate the simulation of complex molecular systems. Traditional molecular dynamics (MD) simulations are computationally expensive, particularly for large systems and long timescales. This research proposes a novel method that leverages the strengths of both quantum computing and classical computing to address these limitations. The core mechanism involves strategically employing quantum computation to expedite computationally demanding aspects of the MD process, while relying on classical methods for the majority of the simulation. We present a detailed framework for integrating these techniques, demonstrating the benefits of this hybrid approach through simulations of a prototypical molecular system – a small molecule with a defined structure. The results highlight the significant speed-up potential offered by this hybrid system, offering a pathway toward more efficient and comprehensive molecular dynamics studies.

Nathan Lysne, Kevin W. Kuper, Poul Jessen