Title:Quantifying entanglement dimensionality from the quantum Fisher information matrix

Abstract:Entanglement is known to be an essential resource for a number of tasks, including quantum-enhanced metrology, and can thus be quantified by figures of merit related to those tasks. In quantum metrology this is emphasized by the connections between the quantum Fisher information (QFI), providing the ultimate bounds of precision, and multipartite entanglement quantifiers such as the depth of entanglement. In systems composed by many qudits, it is also important to characterize the dimensionality of entanglement across bipartitions, i.e., loosely speaking, the minimal number of levels that must be entangled with each other in a given bipartition. However, the impact of high-dimensional entanglement on the QFI remains unexplored. In this work, we fill this gap by deriving a quantum Fisher information matrix (QFIM) criterion for witnessing the entanglement dimensionality across bipartitions, along with scalar corollaries, which we also extend to the multipartite scenario. To further emphasize the significance of our results, we draw connections with the precision of multiparameter estimation, which also provides a practical way of implementing our methods in experiments.