Quasiparticle dynamics of symmetry-resolved entanglement after a quench: Examples of conformal field theories and free fermions

The time evolution of the entanglement entropy is a key concept to understand the structure of a nonequilibrium quantum state. In a large class of models, such evolution can be understood in terms of a semiclassical picture of moving quasiparticles spreading the entanglement throughout the system. However, it is not yet known how the entanglement splits between the sectors of an internal local symmetry of a quantum many-body system. Here, guided by the examples of conformal field theories and free-fermion chains, we show that the quasiparticle picture can be adapted to this goal, leading to a general conjecture for the charged entropies whose Fourier transform gives the desired symmetry-resolved entanglement S-n(q). We point out two physically relevant effects that should be easily observed in atomic experiments: a delay time for the onset of S-n(q) which grows linearly with vertical bar Delta q vertical bar (the difference between the charge q and its mean value) and an effective equipartition when vertical bar Delta q vertical bar is much smaller than the subsystem size.

Automated summary

The time evolution of entanglement entropy is crucial for understanding the structure of nonequilibrium quantum states, often described by moving quasiparticles spreading entanglement. Studies using examples from conformal field theories and free fermion chains suggest that the quasiparticle picture can be adapted to understand how entanglement splits in systems with internal local symmetry. Physically relevant effects, such as delay time for onset of charged entropies and effective equipartition, can be easily observed in atomic experiments.