Quantum Coherence And Application Based On Rydberg Atomic Ensemble

With the continuous development of quantum information and the ultracold atomictechnology, people have found many unique properties of Rydberg atoms, in theprocess of looking for effective qubit. Long-range dipole-dipole interaction andsuper-long life of state make few-body Rydberg atomic system become the hot spot,in the research such as quantum entanglement, quantum logic gates and quantumcontrol. On the other hand, combined with the technology electromagneticallyinducted transparent (EIT), Rydberg atomic ensembles, which is used in full quantumoptical device research such as single photon sources and single photon transistor,have become the focus of attention.First, we have put forward the accurate super atom model for the precisecalculation of Rydberg atomic ensemble steady-state optical response, in view of thedefects and deficiencies of theory of super atom model (SA). Comparing thecalculation results of two kinds of model, we find that the accurate theoretical modelgreatly expand the scope of the original model. Due to breaking the limitation of theweak field approximation and consideration of the high-order collective states, thecalculation of the improved model is closer to the actual physical process under thesituation when single photon process is significant. With stronger probe intensity,large frequency detuning and the large atomic density, the theoretical expectationsgiven by accurate models perfectly fit the experimental results. This work hasprovided a more reliable theory for the study of nonlinear Rydberg-EIT phenomenon,and has given us a solid foundation for the following work.Secondly, on the basis of the single Rydberg blockcade effect, we theoreticallyinvestigate the influence of the double blockcade effect, which is caused by theRydberg cross dipole-dipole interactions effect, on the response of optical system andphoton statistical distribution in the atomic system with two different Rydberg states.We find that the transmission of probe field change with probe, that is nonlinear behavior, and the property of the photon correlations show switching effect betweensingle Rydberg blockcade on double Rydberg blockacde, with the changing of theresonant positions. This work is a breakthrough on the study of Rydberg–EIT. Andwe believe that the results of correlation function modulation is helpful to furtherexplore the effective interaction between single photon, and has important applicationvalues to the research such as photonic devices and quantum information network.Finally, connecting with the dipole blocking effect, we use the standing wavecoupling electromagnetic induction transparency (EIT) medium to implement a newtheory scheme of cooperative nonlinear grating. In the grating system, we use thetechnology of the normal cooperative nonlinear EIT and abnormal nonlinear EIT toaffect the modulation of the grating. The transmission and two-photon correlationabnormal nonlinear EIT are opposite to that of normal nonlinear. With the increasingintensity of the incident probe field, transmission is significantly increasing withanti-bunching effect of the photon (sub-poisson distribution). As a result, we find thatthe new grating is extremely sensitive to the initial properties of probe field (such asprobe intensity and photon statistical rule, etc.), that is the diffraction efficiency of thegrating depends on the initial properties. The intensity and the initial two-photoncorrelation of probe field can be used as new degrees of freedom of the gratingmanipulation. In addition, the diffraction capability of grating is not sacrificed, withthe introduction of new degrees of freedom. This work is of an important applicationin the field of cooperative optical nonlinearity. And it is also helpful to furtherresearch including all light quantum devices, quantum information network and thenon-classical light control.