Reflected entropy and computable cross-norm negativity: Free theories and symmetry resolution

TL;DR

This paper explores new entanglement measures like reflected entropy and CCNR negativity in free theories, deriving exact formulas, analyzing symmetry resolution, and confirming results with conformal field theory and numerical methods.

Contribution

It introduces a reflected version of CCNR negativity, derives exact formulas for free theories, and studies symmetry-resolved entanglement measures with CFT validation.

Findings

Exact formulas for free fermionic and bosonic theories

Perfect agreement between CFT results and numerics for charged moments

Observation of equipartition of reflected entropies and negativities

Abstract

We investigate a separability criterion based on the computable cross-norm (CCNR), and a related quantity called the CCNR negativity. We introduce a reflected version of the CCNR negativity, and discuss its connection with other well-established entanglement-related quantities, namely the reflected entropy and the operator entanglement entropy. For free fermionic and bosonic theories, we derive exact formulas in terms of two-point correlation functions, which allow for systematic numerical investigations and, in principle, analytical treatments. For systems with a global $U(1)$ symmetry, we study the symmetry-resolved reflected entropy and CCNR negativity. We provide conformal field theory (CFT) results for the charged moments in the case of adjacent intervals, finding perfect agreement with the numerics. We observe an equipartition of reflected entropies and CCNR negativities, both for free-fermions and free-boson models. The first charge-dependent corrections are conjectured for fermions, and worked out from the CFT calculations for bosons.