Greenberger-Horne-Zeilinger-type violation of local realism by mixed states

TL;DR

This paper demonstrates that a specific four-photon mixed state derived from cluster states can violate local realism in a GHZ-type manner, highlighting the robustness of cluster states even when some qubits are lost.

Contribution

The study shows a GHZ-type violation of local realism using a mixed state from cluster states, extending understanding of non-locality in lossy quantum systems.

Findings

Successfully generated a four-photon mixed state equivalent to a partial cluster state

Demonstrated GHZ-type violation of local realism with the mixed state

Showed robustness of cluster states under qubit-loss conditions

Abstract

Cluster states are multi-particle entangled states with special entanglement properties particularly suitable for quantum computation. It has been shown that cluster states can exhibit Greenberger-Horne-Zeilinger (GHZ)-type non-locality even when some of their qubits have been lost. In the present work, we generated a four-photon mixed state, which is equivalent to the partial, qubit-loss state of an N-qubit cluster state up to some local transformations. By using this mixed state, we then realize a GHZ-type violation of local realism. Our results not only demonstrate a mixed state's GHZ-type non-locality but also exhibit the robustness of cluster states under qubit-loss conditions.