Mechanism Of Efficient Multiparticle Quantum Entanglement Purification

Quantum entanglement plays an important role in quantum information processing and provides a reliable theoretical basis for the realization of long-distance quantum communication schemes based on quantum entanglement.In order to ensure the security,high efficiency and fidelity of quantum communication,the entangled system shared by all communication parties must maintain the maximum entangled state.However,due to the influence of channel noise,the entanglement channel with high fidelity is inevitably transformed into the entanglement channel with low fidelity.In order to restore the maximum entangled state and improve the fidelity of the non-local mixed state,a quantum entanglement purification model was proposed.For entanglement purification models of multi-particle systems,there are some problems that require initial fidelity greater than 1/2 and have low utilization rate of quantum resources.Therefore,it is particularly important to study an efficient multi-particle entanglement purification model with low initial fidelity and full utilization of quantum resources.Based on the quantum gate and hyperentanglement transfer of the micro-cavity solid state spin ensemble system,an efficient three-photon hyperentanglement purification model is designed.The high efficiency of the model mainly comes from two aspects: on the one hand,a robust quantum state swap gate is used to transfer the high probability of two three-photon subsystems with different degrees of freedom to the same three-photon system,so that the threephoton system has high probability of two degrees of freedom,on the other hand,some hyperentangled three-photon systems are extracted from the hyperentangled two-photon subsystems by hyperentangled links.The model is more than four times more efficient when the initial fidelity is less than half.In addition,imperfect operation caused by cavity boundary leakage can predict whether the model is effective or not by the fast and accurate response of the detector.Therefore,the fidelity theory of the quantum gate can reach 100%,and this warning function is expected to realize the absolutely safe fidelity transmission of quantum information.In addition,the hyperentanglement purification model can be directly extended to multi-photon entanglement systems with one degree of freedom or multi-degree of freedom.An efficient three-electron spin state entanglement purification model was designed based on predictable parity detection gate and spin entanglement link in a micro-cavity solid spin system.Our model uses a predictable parity gate to directly obtain a high fidelity three-electron spin entanglement mixed state,and to extract a two-electron spin entanglement system from a cross term discarded in a conventional three-electron spin purification scheme.Furthermore,some entangled three-electron spin systems are extracted from entangled two-electron spin subsystems by entangled links.The model is more than twice as efficient when the initial fidelity is less than half.In addition,the scattering bias due to microcavity leakage and the finite coupling operation between quantum dots and cavity modes can be predicted by the accurate response of the detector,so our model can be performed in a heralded way.