Effect of Photon Addition on Genuine Tripartite Entanglement of Continuous Variable States

Abstract

The enumeration of multipartite entanglement is an essential, yet challenging task in quantum information processing. A new measure for calculating genuine tripartite entanglement, called the concurrence fill (CF), has been added to the list of entanglement measures. In this article, we employ the CF to calculate the extent of entanglement present in the three-mode continuous variable states, such as the quasi-GHZ state and quasi-W state. The above mentioned states mimic their respective discrete variable states for moderate coherent strength, while for lower coherent strength, the states are far from possessing maximum entanglement. The photon addition in these states at the single mode and three-mode levels results in the states reaching their respective maximum amount of entanglement even for the lower coherent amplitude. In continuation, a nonlocal tripartite photon addition is implemented on a product three-mode coherent state, and the resultant state is shown to have W-type entanglement.