Preparation Of Logical W States And Fusion Of Hybrid W States

Quantum entanglement is an important physical resource in quantum information processing.During the past few decades,entanglement has been widely used in many branches of quantum communication and quantum computation,such as quantum teleportation,quantum key distribution,quantum secure direct communication and some other important applications.There are many forms of quantum entanglement.In a two-particle system,Bell state belongs to two-particle entanglement.In a multi-particle system,there are GHZ state,W state,and so on.However,entanglement is easily affected by the environment.For example,noise can cause photon loss or decoherence.Studies have found that in actual physical systems,the W state is more suitable for quantum computing or quantum communication.Comparing with other entanglements,even when the photon is lost or decohered,other particles can maintain the entanglement relationship well.For other entanglements,for example,when a particle is lost in the GHZ state,the entanglement relationship between all particles will be broken.Therefore,the W state has good anti-noise and decoherence ability.In addition,studies have shown that the larger the size of multi-particle entanglement,the more obvious its quantum advantage in quantum communication and quantum computing.For this characteristic,they have studied how to prepare large-scale hybrid entangled W states.At the same time,for physical bits,if a physical bit is encoded into a logical bit,the robustness of the quantum state in the channel will be greatly enhanced.So preparing the logical W state is also another important research direction of this paper.This paper uses cascade and fusion to realize the preparation of the above logical W state and large-scale hybrid entangled W state.In order to enhance the robustness of quantum states,logic coding is widely used.The cascaded GHZ state is a logical bit entangled state.Experiments have shown that it can greatly enhance the anti-interference of the GHZ state.Based on this,they propose a deterministic cascaded W state preparation method to construct a logical W state.Through their solution,logical W states of any size can be prepared.They first encode each physical bit of the W state into a two-particle GHZ state,then generalize to the W state of any scale,and encode the physical bits into a GHZ state of any scale.On the other hand,because large-scale quantum entanglement has obvious advantages,they designed two and three hybrid entangled W state fusion schemes using quantum fusion technology to prepare larger-scale mixed entangled W states.They use coherent state and polarization state hybrid qubits to form this kind of hybrid entanglement resource.This fusion process is completed only by using the hybrid Bell state measurement formed by the polarization beam splitter and the detector.The formation of a special hybrid entangled W state formed by the coherent state and the polarization state may greatly increase the fault tolerance threshold of quantum computing and will greatly reduce resource consumption.