When two atomic nuclei collide, the outcome depends on their energy and the angle at which the fragments fly apart. Typically, such calculations demand enormous computing power, and accuracy hits a wall due to approximations. The authors propose a different path: shift the problem to a quantum computer, which naturally describes quantum mechanics.
The idea is as simple as a game of billiards. The initial state is two 'balls' (wave packets) heading toward each other. The quantum computer faithfully computes their time evolution, as if we were filming the collision frame by frame. Then, the overlap between incoming and outgoing packets is taken, and a Fourier transform yields the scattering matrix at the desired energy. From that, cross sections for elastic and inelastic reactions are obtained.
The method has been tested numerically on examples of elastic and inelastic scattering, and the results match exact calculations. What's especially valuable is that the approach easily scales to systems with many particles — once fault-tolerant quantum computers appear, it will become a practical tool for nuclear physics and chemistry.
The optical theorem links the total scattering cross section to the forward scattering amplitude. This means that by measuring only the probability of passing through without deflection, one can learn how often particles interact at all.
In the series 'The Expanse', fusion drives on ships require precise knowledge of nuclear reactions. Quantum computers could speed up the development of such technologies.