Symmetric inseparability and number entanglement in charge-conserving mixed states

Zhanyu Ma, Cheolhee Han, Yigal Meir, Eran Sela

Research output: Contribution to journalArticlepeer-review

Abstract

We explore sufficient conditions for inseparability in mixed states with a globally conserved charge, such as a particle number. We argue that even separable states may contain entanglement in fixed charge sectors, as long as the state cannot be separated into charge-conserving components. As a witness of symmetric inseparability we study the number entanglement (NE), ?Sm, defined as the entropy change due to a subsystem's charge measurement. Whenever ?Sm>0, there exist inseparable charge sectors, having finite (logarithmic) negativity, even when the full state either is separable or has vanishing negativity. We demonstrate that the NE is not only a witness of symmetric inseparability, but also an entanglement monotone. Finally, we study the scaling of ?Sm in thermal one-dimensional systems combining high-temperature expansion and conformal field theory.

Original languageEnglish
Article number042416
JournalPhysical Review A
Volume105
Issue number4
DOIs
StatePublished - Apr 2022

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