Hyperentanglement concentration for time-bin and polarization hyperentangled photons

TL;DR

This paper introduces two linear-optics-based schemes for concentrating hyperentangled photon states in polarization and time-bin degrees of freedom, enhancing long-distance quantum communication efficiency.

Contribution

It proposes novel hyperentanglement concentration protocols applicable to two-photon and N-photon GHZ states, requiring only one copy or two identical states, with practical feasibility.

Findings

Protocols successfully concentrate hyperentanglement in polarization and time-bin.

Schemes are feasible with current linear optics technology.

Resource savings achieved by using time-bin over spatial modes.

Abstract

We present two hyperentanglement concentration schemes for two-photon states that are partially entangled in the polarization and time-bin degrees of freedom. The first scheme distills a maximally hyperentangled state from two identical less-entangled states with unknown parameters via the Schmidt projection method. The other scheme can be used to concentrate an initial state with known parameters, and requires only one copy of the initial state for the concentration process. Both these two protocols can be generalized to concentrate N-photon hyperentangled Greenberger- Horne-Zeilinger states that are simultaneously entangled in the polarization and time-bin degrees of freedom. Our schemes require only linear optics and are feasible with current technology. Using the time-bin degree of freedom rather than the spatial mode degree of freedom can provide savings in quantum resources, which makes our schemes practical and useful for long-distance quantum communication.