Calibration robust entanglement detection beyond Bell inequalities

TL;DR

This paper develops robust entanglement detection methods for intermediate scenarios with partial measurement knowledge, avoiding Bell inequality violations and tolerating calibration errors, even for bound entanglement.

Contribution

It introduces new entanglement detection criteria applicable under partial measurement assumptions, bridging the gap between fully characterized and device-independent approaches.

Findings

Detection criteria are robust against calibration errors.

Criteria can detect bound entanglement with limited assumptions.

No Bell inequality violation needed for entanglement detection.

Abstract

In its vast majority entanglement verification is examined either in the complete characterized or totally device independent scenario. The assumptions imposed by these extreme cases are often either too weak or strong for real experiments. Here we investigate this detection task for the intermediate regime where partial knowledge of the measured observables is known, considering cases like orthogonal, sharp or only dimension bounded measurements. We show that for all these assumptions it is not necessary to violate a corresponding Bell inequality in order to detect entanglement. We derive strong detection criteria that can be directly evaluated for experimental data and which are robust against large classes of calibration errors. The conditions are even capable of detecting bound entanglement under the sole assumption of dimension bounded measurements.