Title: Toward real-time hadronic physics with quantum computers Speaker:  Chung-Chun Hsieh (QuICS) Date & Time:  July 7, 2026, 10:00am Where to Attend:  PSC 3150
Understanding how hadrons form, scatter, and respond to external probes is crucial for particle and nuclear physics. These questions are intrinsically of real-time nature and emerge from the strongly coupled quantum chromodynamics (QCD), where perturbation theory loses control. The standard first-principles tool, lattice QCD, simulates the theory on a discrete spacetime grid and has reached remarkable precision for the static properties of hadrons. Real-time dynamics, however, lie beyond its direct reach because lattice QCD works in imaginary time, and numerical instability of analytic continuation obstructs many dynamical observables. A Hamiltonian description instead treats real time directly, at the cost of tracking a quantum state in a Hilbert space that grows exponentially with the number of lattice sites. Quantum computers provide a natural framework for this Hamiltonian approach, encoding the state on qubits and evolving it in real time. Each qubit is a two-level quantum system, and a register of them spans a Hilbert space whose dimension grows exponentially with their number.
This thesis develops digital quantum algorithms for real-time hadronic physics, following the three stages of state preparation, time evolution, and measurement. A hadron is a bound state of matter and gauge fields, subject to the gauge symmetry of the theory, which makes its preparation nontrivial. Here, we prepare localized hadronic wave packets to simulate scattering processes. Importantly, the hadronic wave packets are built from a systematically improvable ansatz with fixed quantum numbers. This procedure yields high-fidelity mesons in the Z2 and U(1) lattice gauge theories coupled to matter in 1+1 dimensions. We then time-evolve two such wave packets, each given a chosen momentum-space profile, bringing them into collision. The corresponding quantum circuits realize hadronic scattering on present-day trapped-ion hardware. A complementary question concerns the internal structure of a single hadron, encoded in an object called the hadronic tensor. The hadronic tensor is determined by a real-time correlation function of currents. We compute this correlator with quantum circuits, using the state-preparation and time-evolution methods developed in this thesis. As a proof of concept, we carry out the calculation in the U(1) lattice gauge theory coupled to matter in 1+1 dimensions and benchmark the quantum-circuit implementation.
Together, this thesis establishes a digital-quantum-simulation route to preparing hadronic states, evolving them in real time, and extracting physical observables. It provides concrete steps toward quantum algorithms for first-principles studies of real-time hadronic physics, with the long-term aim of reaching QCD.