Measuring Entanglement in a Photonic Embedding Quantum Simulator

TL;DR

This paper demonstrates an experimental photonic embedding quantum simulator that efficiently measures bipartite entanglement, specifically concurrence, using only two observables instead of full tomography, significantly reducing complexity.

Contribution

It provides the first experimental implementation of an embedding quantum simulator in photonics for efficient entanglement measurement, reducing the observables needed from fifteen to two.

Findings

Bipartite concurrence can be extracted efficiently with two observables.

The device encodes bipartite entangling dynamics into a tripartite system.

Full quantum state tomography is unnecessary for entanglement measurement.

Abstract

Measuring entanglement is a demanding task that usually requires full tomography of a quantum system, involving a number of observables that grows exponentially with the number of parties. Recently, it was suggested that adding a single ancillary qubit would allow for the efficient measurement of concurrence, and indeed any entanglement monotone associated to antilinear operations. Here, we report on the experimental implementation of such a device---an embedding quantum simulator---in photonics, encoding the entangling dynamics of a bipartite system into a tripartite one. We show that bipartite concurrence can be efficiently extracted from the measurement of merely two observables, instead of fifteen, without full tomographic information.