Spatial and polarization entanglement of three photons in a discrete-time quantum walk

TL;DR

This paper explores the generation of multipartite spatial and polarization entanglement among three photons using a discrete-time quantum walk setup on a square lattice, with potential applications in quantum technology.

Contribution

It extends previous two-photon entanglement results to three photons, analyzing the creation of W and GHZ states in both spatial and polarization degrees of freedom.

Findings

Three-photon entanglement classes can be generated using the proposed setup.

Spatial and polarization entanglement can be simultaneously achieved.

The setup offers a simple method for producing multipartite entangled states.

Abstract

We investigate quantum entanglement of three photons performing discrete-time quantum walk (DTQW) on the nearest-neighbor sites of a square lattice. Such a DTQW setup has already been proposed to be realizable using linear optical elements. Each lattice site corresponds to the sequential action of a half-wave plate and a polarizing beam splitter. Two-dimensional DTQW can be mapped to an effective one-dimensional DTQW with a four-sided coin that depends on the polarization and direction of motion of the photons. It is known that such a system is capable to spatially entangle two photons, prepared in a separable state initially. We generalize the result to the case of three photons to explore if distinct entanglement classes, namely W and GHZ states, can be produced by this setup. In addition to spatial entanglement, we analyze the possibility of entanglement in the polarization basis, too. Our results can be significant for a simple and fast generation of multipartite entangled photonic states demanded by practical quantum technology applications.