Exact interferometers for the concurrence and residual 3-tangle

TL;DR

This paper introduces quantum circuits capable of directly measuring two- and three-qubit entanglement measures, specifically concurrence and 3-tangle, without adding noise, advancing quantum entanglement characterization methods.

Contribution

The paper presents novel circuit designs for exact measurement of concurrence and residual 3-tangle, improving precision in entanglement quantification for quantum states.

Findings

Circuits accurately measure concurrence without added noise

Extension to measure 3-tangle for pure three-qubit states

Provides a practical approach for entanglement quantification

Abstract

In this paper we describe a set of circuits that can measure the concurrence of a two qubit density matrix without requiring the deliberate addition of noise. We then extend these methods to obtain a circuit to measure one type of three qubit entanglement for pure states, namely the 3-tangle.