Scientists have developed a new model based on variational quantum circuits to represent pion fragmentation functions (FFs). These functions are crucial in particle physics to describe how quarks and gluons (partons) fragment into observable hadrons, such as pions. The innovative approach uses a quantum circuit to encode FFs, leveraging quantum mechanics properties for a more efficient and precise representation.

The model imposes isospin and charge-conjugation symmetries to construct an independent six-flavor basis, covering charged and neutral pion production. It incorporates physics-inspired Ansätze, such as logarithmic feature maps and mass thresholds, to encode the relevant kinematics. This quantum architecture significantly reduces circuit redundancies and improves optimization convergence. Using the DSS14 pion FF set as a benchmark, the team initially developed a one-dimensional variational representation (FF-VQR) in momentum fraction at a fixed energy scale.

Results show that entanglement between quark and gluon FFs yields a substantial improvement, achieving high accuracy with just two variational layers. A spectral analysis further demonstrated that the quantum model exhibits high expressivity with a limited number of Fourier modes, making it suitable as a compact non-perturbative parametrization for DGLAP evolution. Subsequently, the FF-VQR was extended to two dimensions, incorporating energy-scale dependence. By encoding all flavor channels within a single entangled quantum circuit, the model provides a unified representation with higher accuracy than independent encoding for each partonic species.