Probing Defects with Quantum Simulator Snapshots

Snapshots, i.e. projective measurements of local degrees of freedom, are the most standard data taken in experiments on quantum simulators. Snapshots are usually used to probe local physics. In this work we propose a simple protocol to experimentally probe physics of defects with these snapshots. Our protocol relies only on snapshots from the bulk system, without introducing the defect explicitly; as such, the physics of different kinds of defects can be probed using the same dataset. In particular, we demonstrate that with snapshots of local spin configurations of, for example, the $1d$ Rydberg atom realization of the quantum Ising criticality, we can (1) extract the ``defect entropy", and (2) access the continuous line of fixed points of effective defect conformal field theory, which was recently discussed in the context of the ``weak-measurement altered criticality".