State preparation and detection for quantum simulation of particle collisions

Quantum simulators have emerged as a powerful approach for simulating the dynamics of quantum many-body systems, competing directly with state-of-the-art classical computational techniques [1, 2]. A promising application is the simulation of scattering processes, akin to those occurring in particle colliders [3–12]. In this setting, the theory of interest is modeled as a lattice Hamiltonian, and the particles are the low-energy excitations (quasiparticles) carrying well-defined momentum. Quantum simulators can reproduce the collision of two such particles in real time, probing not only the scattering matrix (which encodes the probabilities of the final asymptotic states), but also the state of the system during the collision or shortly after. This capability opens the door to studying phenomena such as the emergence of hydrodynamics, thermalization, and aspects of heavy-ion collisions in controlled quantum many-body systems [13, 14]. Quantum simulators may become particularly advantageous in the high-energy regime, where the energy is much larger than the mass gap and inelastic channels with many particles become accessible. Since the entanglement entropy generated in a scattering event is expected to increase with the number of particles produced, such processes are challenging to simulate using tensor-network methods [15]. While tensor networks have proven highly successful at low…