Research Of Ghost Imaging And Quantum Multiple Access Communication Based On Entanglement Of Photon Orbital Angular Momentum

Entangled photons are separated into two different optical paths, and object is set in one ofthem. By means of recording coincidence rates, the image is obtained in another optical path.This kind of imaging is named correlated imaging or ghost imaging. For its unique properties,ghost imaging has attracted more and more attentions recently. It will have extensiveapplications in military, medical, astronomy, searching and rescuing fields.In this paper, we analyze ghost imaging process with phase object based on obital angularmomentum of photons. Since the relationship between coincidence rate and angles originatingfrom the superposition states on the equator of Bloch sphere is a cosine function, we propose anew encoding method for multiple grey scales object. We verify the effectiveness of thisalgorithm by numerical simulation, and compare them with the result using the method in [16].Simulation results show that for a multiple gray scale object, our proposed encoding algorithmcan significantly improve the image quality.Based on it, we test the proposed encoding algorithm in experimental by using quantumentanglement experiment platform, and achieve the experimental result with the method in [16].Experimental gives the same result to the numerical simulation. In order to show quantumfeature of the system, we calculated the correlation coefficient experimentally by means ofscaning Bloch sphere. The results (S=2.54 when l=1, S=2.32 when l=2) violate a Bell inequality,it implies that the ghost imaging system is based on quantum entanglement..Moreover, we further propose a quantum multiple access communications scheme based onentanglement of OAM. Quantum states with different OAM values are orthogonal and composeda complete basis. Borrowing the concept from Code Division Multiple Access,,we map symbolsof different users to OAM states on Bloch sphere equator with different eigen states, and let thesuperposition of all users'state be transported by the signal light. At idler path, different detectorhas a different measurement basis. Because each user's measurement basis is orthogonal toothers'. each user can detect his own information. Numerical simulations show the effectivenessof the scheme.. We give the schematic experimental setup of the scheme at last.