Detection of mode-intrinsic quantum entanglement

TL;DR

This paper introduces a practical method to detect a special form of non-Gaussian entanglement in continuous-variable quantum systems, which is crucial for quantum computing advantages, using minimal measurements.

Contribution

It proposes a new entanglement witness that detects mode-intrinsic non-Gaussian entanglement with simple, basis-independent measurements, enhancing experimental feasibility.

Findings

The witness can detect entanglement in any mode basis.

It requires only measurements in one basis, simplifying experiments.

It does not need full quantum state tomography.

Abstract

Quantum correlations are at the core of the power of quantum information and are necessary to reach a quantum computational advantage. In the context of continuous-variable quantum systems, another necessary ressource for quantum advantages is non-Gaussianity. In this work, we propose a witness, based on previously known relations between metrological power and quantum correlations, to detect a strong form of entanglement that only non-Gaussian states possess and that cannot be undone by passive optical operations, i.e., entanglement in all mode bases. The strength of our witness is two-fold: it only requires measurements in one basis to check entanglement in any arbitrary mode basis; it can be made applicable experimentally using homodyne measurements and without requiring a full tomography of the state.