Laser & Photonics reviews: generation and manipulation of spatially entangled photon states using nonlinear metamaterials

Since the birth of quantum mechanics quantum entanglement is one of the most representative concepts. After some initial treatment two or more particles can enter a state of seemingly "hyperspace correlation": even if they are separated by hundreds of thouss of light years the change of one particle will affect other particles instantaneously. This phenomenon was once called "ghostly over distance action" by Einstein so quantum entanglement is often known as "Einstein's ghost". Photon system is one of the platforms used to demonstrate quantum entanglement in practice. The nonlocal correlation properties can be constructed based on many degrees of freedom of photons. In recent years more more attention has been paid to the entangled states of photon space modes because there are a lot of controllable degrees of freedom in space-time such as photon orbital angular momentum. The development of these degrees of freedom can greatly enhance the information carrying capacity of photons which is very conducive to applications such as quantum communication quantum computing so on.

as an important platform to achieve effective fine control of the spatial characteristics of light field the excellent ability of metamaterials in this aspect has been fully demonstrated in the field of classical optics but their application potential in quantum optics has not been explored. For the metamaterial composed of micro nano antenna type "artificial atoms" the interaction between them photons can lead to the entanglement of spatial degrees of freedom. Moreover the exploration in this direction directly establishes the relationship between the properties of entangled photon states the mesoscopic structure may provide some perspectives for further solving the apparent contradiction between the micro romness the macro certainty that have puzzled people for a long time.

associate professor Mingyang Professor Liu Yushen of Changshu Institute of technology together with Professor Lu Yanqing of Nanjing University have studied the generation control of spatially entangled photon states based on parametric down conversion in metamaterials with ideal optical nonlinearity. The material geometry spatial orientation lattice type of the artificial atoms can affect the overall response of the Supersurface to electromagnetic field. Therefore through flexible micro nano structure design we can effectively control the nonlinear interaction process of photons in metamaterials so as to plan the spatial characteristics of generated photons according to the needs. The theoretical framework used to describe the system is established based on the nonlinear Huygens Fresnel principle the equivalent beam splitter model: for the former each artificial atom is regarded as a secondary down conversion wave source its local interaction is described by Hamiltonian density then the global form of the entangled state is obtained by integrating the whole space; the latter is used to deal with the intrinsic loss of the system Consumption. As a specific consideration the transverse spatial distribution of micro nano antenna is in the shape of fork grating the metamaterial is used to generate the orbital angular momentum entangled state. The simulation results show its effectiveness. Relevant research results of

were published in Laser & Photonics reviews

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