Scaling of entanglement entropy and superselection rules

Understand

Particle number conservation in fermionic systems restricts the allowed local operations on bi-partite systems.

• We show how this restriction is related to measurement entropy of particle fluctuations and compute it for several regimes of practical relevance.
• The accessible entanglement entropy restricted by particle number conservation is equal, to leading order, to the full entanglement entropy.
• The correction is bounded by the log of the variance of particle number fluctuations.