Preparation of $km$-photon concatenated GHZ states for observing distinct quantum effects at macroscopic scale

TL;DR

This paper proposes scalable methods to experimentally generate multipartite concatenated GHZ states, which are highly stable entangled states suitable for observing quantum effects at macroscopic scales.

Contribution

It introduces two scalable experimental schemes for preparing $km$-photon C-GHZ states using multiphoton entanglers and control gates, advancing quantum state engineering.

Findings

Proposed scalable experimental realization methods.

Schemes for creating $km$-photon C-GHZ states from $km$ single photons.

Enhanced stability of C-GHZ states under decoherence.

Abstract

As a class of multipartite entangled states, the multipartite concatenated GHZ (C-GHZ) states remain superior stability under the influence of decoherence. We propose two scalable experimental realization of the multiphoton C-GHZ states based on the entanglers of multiphoton GHZ state. Given a $km$-photon GHZ state as an input state, if $m$ is odd, one can create a $km$-photon C-GHZ state. Also, generally, we design a scheme to prepare $km$-photon C-GHZ states from $km$ single-photon states by using $k$ entanglers of $m$-photon GHZ state and $k$ $m$-control Toffoli gates.