Novel Schemes for Directly Measuring Entanglement of General States

TL;DR

This paper introduces a new framework for directly measuring entanglement in general quantum states, demonstrating that simple local measurements can determine the concurrence of two-qubit states without full state tomography.

Contribution

It proposes a novel scheme utilizing rank-1 local factorizable measurements to directly quantify entanglement, simplifying the measurement process for arbitrary states.

Findings

Rank-1 local measurements suffice for direct concurrence measurement.

The scheme requires only one copy of the entangled state at a time.

It establishes a connection between entanglement measures and measurement schemes.

Abstract

An intrinsic relation between maximally entangled states and entanglement measures is revealed, which plays a role in establishing connections for different entanglement quantifiers. We exploit the basic idea and propose a framework to construct schemes for directly measuring entanglement of general states. In particular, we demonstrate that rank-1 local factorizable projective measurements, which are achievable with only one copy of entangled state involved at a time in a sequential way, are sufficient to directly determine the concurrence of arbitrary two-qubit entangled state.