Researchers from the University of Trento, the InQubator for Quantum Simulations, and Lawrence Livermore National Laboratory (LLNL) recently published an algorithm for a quantum computer that faithfully mimics scattering in Physical Review C.
When quantum mechanical particles scatter, it shifts the position of their wave. The new algorithm accurately measures these shifts, opening the way to quantum simulations of scattering processes. Image Credit: Sofia Quaglioni
Scattering occurs on both big and small sizes throughout the universe. The nuclei of atoms clash to power the stars and form heavy elements, and sound waves alter their course when they strike airborne particles.
Gaining insight into this scattering can help us understand the forces governing the cosmos.
Scattering experiments help us probe fundamental particles and their interactions. The scattering of particles in matter [materials, atoms, molecules, nuclei] helps us understand how that matter is organized at a microscopic level.
Sofia Quaglioni, Scientist, Lawrence Livermore National Laboratory
The study looks at nonrelativistic elastic scattering, where a projectile particle bounces off a stationary target particle without losing any energy and its speed is significantly slower than that of light.
The computer resources needed for a simulation rise exponentially with the number of particles included. Quantum computers can encode and process more data than classical computers, which frequently can't keep up.
“Quantum computers are naturally good at realizing the time evolution of two interacting particles, which is directly connected to the scattering of the particles,” added Quaglioni.
"High-performance computing simulations based on microscopic physics for nuclei relevant to stellar explosions would require a moon-scale supercomputer," added LLNL scientist Kyle Wendt.
The initial state of the particle system, which describes how the projectile and target particles are moving toward one another, as well as details about their interactions, are sent into the team's algorithm. It then uses a detector and a variational "trick" to trace the impact of the collision while playing the dispersion forward in time.
Particles in quantum physics behave similarly to waves. Particle scattering causes a wave's position within its cycle to change. The method creates and modifies a detector wave at each step until it fits the particle wave in order to measure this shift.
The researchers first tested the method using a traditional computer for simulation. Once its reliability was confirmed, they conducted simulations on IBM quantum processors. The variational method employed to measure changes in the dispersed particle wave proved resilient against the noise sources that typically challenge advancements in quantum computing hardware.
The suggested quantum algorithm is a major breakthrough in the field of quantum simulations because of its resilience to quantum hardware noise and its scaling, which is mostly determined by the dynamics of real-time evolution.
Although demonstrated on the simplest scattering process under the most basic conditions, this approach can be extended to more complex processes that currently exceed the capabilities of classical high-performance computing, except for systems involving only a very small number of particles.
Journal Reference:
Turro, F. et. al. (2025) Evaluation of phase shifts for nonrelativistic elastic scattering using quantum computers. Physical Review C. doi.org/10.1103/PhysRevC.110.054604