Repulsively bound hadrons in a Z₂ lattice gauge theory

The Z₂ lattice gauge theory is a paradigmatic model that exhibits gauge-field-mediated confinement of pairs of particles into mesons, drawing connections to quantum chromodynamics. In the absence of any additional attractive interactions between particles, mesons are not known to bind in this model. In this talk, I will show that resonant pair-production terms give rise to two separate mechanisms to form stable “hadron” bound states of two mesons: either induced by an effective attractive interaction, or a new dynamical binding mechanism induced by an effective repulsion. The repulsively bound hadron is a high-energy state stabilized by being energetically separated from the two-meson continuum. The quantum fluctuations of the gauge fields are crucial contributors to the energy of this hadron state, reminiscent of how gluon fluctuations significantly contribute to the mass of protons and neutrons in the theory of strong nuclear force.  I will discuss the dynamical formation of this bound state starting from local excitations, making it amenable to experimental observation on modern quantum hardware such as superconducting qubits, trapped ions, and Rydberg atom arrays.