The Preparation Of Multi Degree Of Freedom Hybrid Entangled Quantum States

It is well known,quantum entangled state is one of the key resources for quantum information and quantum computing.Therefore,the preparation of quantum entangled states is extremely important and has also been developed rapidly.In recent years,the preparation of entangled states with multiple degrees of freedom has attracted extensive attention.This is because it can make not only quantum communication have a larger channel capacity,but also quantum information processes more efficiently.In this context,this thesis will focus on the study of the preparation of entangled states of photons with multiple degrees of freedom.By using optical devices to control quantum states,we propose an experimental scheme for the preparation of two-photon three-degree-of-freedom hybrid entangled W states.First,we use nonlinear crystals such as HWP and PDBS to generate two-degree-of-freedom(polarization and path)hybrid entangled W state for two-photon.Next,by using Q-Plate to convert the polarization state of one photon into the orbital angular momentum state,we then get the three-degree-of-freedom hybrid entangled W state for the two photon.That is,the hybrid entangled W state with multiple-degree-of-freedom is realized by using less resources.However,it does not allow us for the direct projective measurement.Therefore,we propose an experimental scheme on how to indirectly detect and verify the resulted hybrid W state.It is based on that the pure three-qubit state can be uniquely determined by the reduced density matrix of two two-qubit states.This verification greatly improves the efficiency of state preparation.The produced W state not only has the ability to transmit more quantum information,but also has better anti-interference.If a qubit is lost during transmission,its fidelity can obtain 5/9.In addition,we also study two-photon three-degree-of-freedom hybrid entangled W-like states for quantum teleportation.Finally,by adjusting the optical path and modifying the parameters of the PDBS,we generate the single-photon three-degree-of-freedom hybrid entangled W state and the two-photon four-qubit cluster state.The preparation efficiency of these states is 1/2,which is much more improved compared to the existing schemes.Consequently,we can efficiently prepare more kinds of multi-degree-of-freedom entangled states through similar schemes.It not only helps to achieve more secure and compatible quantum network communication,but also promotes the development of quantum state preparation for quantum information.