C3NT workshop: Quantum Information Science in High Energy Nuclear Physics (QIS-HENP)

Understanding confinement and gauge-field dynamics beyond the reach of classical computation is one of the driving motivations for quantum simulation. I will present two complementary advances using superconducting circuits as a platform for lattice gauge theories (LGTs).

First, I will report on a digital quantum simulation of the Z2-Higgs model in (2+1) dimensions on a superconducting processor with up to 144 qubits and circuit depths reaching 192 two-qubit layers. Matter and gauge fields are mapped directly onto vertex and link qubits of a heavy-hex architecture. Combining error suppression, mitigation, and correction strategies, we observe in real time the string modes of motion of electric flux tubes connecting dynamical charges, providing a direct window into the stringy nature of confinement.

Second, I will introduce a superconducting-circuit architecture for analog quantum simulation of compact U(1) LGT that exploits the intrinsic infinite-dimensional Hilbert space of phase and charge variables. Gauss's law emerges exactly from local charge conservation, without auxiliary stabilizers, penalty terms, or Hilbert-space truncation, while the magnetic plaquette interaction is generated perturbatively through Josephson nonlinearities. Numerical diagonalization confirms the emergence of compact electrodynamics and coherent vortex excitations. Together, these results establish superconducting circuits as a scalable, versatile platform for probing non-perturbative gauge dynamics.

Parton distribution functions (PDFs), generalized parton distributions (GPDs), and hadronic tensors provide complementary information about the internal structure of hadrons. Quantum computing offers a Hamiltonian real-time simulation framework for these observables and may help overcome the sign problem that limits conventional Monte Carlo approaches.

In this talk, I will introduce recent progress along this direction. I will first discuss the direct quantum simulation of PDFs in the 1+1 dimensional Nambu–Jona-Lasinio model, where hadronic states are prepared by a quantum-number-resolving variational algorithm and light-front correlation functions are measured on quantum circuits. I will then extend the discussion to gauge theories, focusing on PDFs and GPDs in the Schwinger model, where gauge invariance and Wilson lines must be incorporated into the quantum algorithm.

Finally, I will discuss the non-Abelian case. Since the gauge links in PDF operators become significantly more complicated in QCD-like theories, an alternative strategy is to probe hadron structure through the hadronic tensor, computed from real-time current-current correlation functions. This provides a practical route to extract form factors and, in the future, to access deep-inelastic structure functions. Together, these studies outline a possible route toward quantum simulations of hadron structure, from PDFs and GPDs in the Schwinger model to hadronic tensors in 1+1 dimensional SU(2) gauge theory.