The Entanglement-assisted Noiseless Linear Amplification For Arbitrary Two-photon Polarization-time-bin Hyperentanglement

Quantum communication is a new research field formed by the intersection and fusion of quantum mechanics and information theory.Quantum communication uses single quantum bit or quantum entanglement as the carrier for information exchange and information processing.Compared with classical communication,quantum communication has absolute security.In recent years,quantum communication has achieved a lot of research results,and has gradually become a research hotspot around the world.Quantum entanglement is a very important phenomenon in quantum mechanics.Quantum entanglement plays an important role in long-distance information transmission.Entanglement is used in many quantum problems,such as quantum teleportation,quantum cryptography,quantum secure direct communication,quantum Repeaters,quantum key distribution and other fields.However,in practical applications,quantum entanglement is sensitive to the environmental noise in the transmission process.The environmental noise causes the photon propagation in the fiber to decay exponentially with the increase of the channel length,resulting in photon loss in the transmission process,which greatly limits the application of quantum communication in long distance.In order to improve the quality of information transmission,quantum noise-free linear amplification(NLA)is proposed as an effective way to protect single photons and entanglement from photon transmission loss.Hyperentanglement refers to the simultaneous entanglement of quantum systems in multiple degrees of freedom,which can improve the channel capacity and security of quantum communication,and has attracted extensive attention in the field of quantum communication.Similarly,the transmission loss of the hyperentangled state is inevitable in the distribution process of the actual noisy quantum channel.In the first work,a noise-free linear amplification of two-photon time-polarized hyperentangled states is realized with the aid of entangled states.The proposed scheme can effectively improve the fidelity of the two-photon time-polarization hyperentangled state,reduce the photon transmission loss,and maintain the entanglement properties of the two degrees of freedom in time and polarization.This scheme can be further extended to protect N-photon polarized-time hyperentangled systems.In the second work,a noiseless linear amplification-generalized quantum scissors scheme for FOCK photon entanglement states is proposed.This scheme is an improvement of the quantum scissors,which can effectively truncate the FOCK states of common light sources with high order,effectively control the number of photons in the FOCK states,and retain the coding information of the FOCK states.Both of the two NLA amplification devices in this paper are commonly used optical devices,which can be applied under the existing experimental conditions,and have strong applicability,and have an important application prospect in the future quantum information applications.