Generation And Manipulation Of Multiphoton Frequency Correlation In Optical Superlattice

Based on the principle of quantum mechanics,such as principle of superposition,and quantum entanglement,quantum information science with its unique advantages has become one of the most active area of research in physics and information science.It can realize more efficient quantum computation,absolutely secure quantum communication and accurate measurement.In recent decades,quantum information science has achieved fruitful results in a wide range of fields and has made remarkable progress in a variety of physical systems,including linear optics,ion trap,quantum dot,NV center in diamond,superconducting circuit,cold atoms and nuclear magnetic resonance,etc.Among all these systems,the photon system provides a very competitive physical platform with the advantages of fast information transmission,strong coherence and mature technology.Remarkable progress has been made in the field of theoretical and experimental quantum optics in recent years.At present,optical superlattice is one of the most commonly used materials that are used for the generation of entangled photon in quantum optical experiment.It is possible to efficiently produce different types of entangled states by designing various of periodic domain structures in nonlinear optical crystals.Furthermore,waveguide and electro-optical modulation module can be integrated in a same optical superlattice which has become one of the main platforms to prepare quantum photonic chips.The integrated chip has a small size,good scalability and stable phase,which can overcome the drawbacks of traditional optical circuits.The development of quantum photonic chip has promoted the practical process of quantum information technology.Although the entangled states of 10 qubits has already been realized in bulk crystal,the problem of extensibility for the qubits on integrated circuits arises.The improvement of the number of entangled bits on optical chips is still a problem to be solved.This thesis is dedicated to study the multiphoton entangled state on optical superlattice,especially the generation and manipulation of three-photon frequency correlation.The three-photon here which have intrinsic time and space correlation is not derived from two indistinguishable photon pairs,but from cascaded nonlinear process.On one hand,the three-photon entangled state is a very important physical resource which plays important roles in quantum information processing,for example,multiparty quantum communication and quantum secret sharing requires stable and scalability multiparticle entangled states.On the other hand,as a fundamental problem of quantum mechanics,these three-body entanglement have rich physical connotations.Different potential applications need different specific degrees of frequency entanglement.Based on the important role of these two aspects,we carried out this research work.And the contents of this dissertation mainly include the following aspects.(1)We investigate the generation and manipulation of frequency correlation for biphoton EPR states generated from optical superlattice waveguide.We calculated the generation rate of photon pairs in both the bulk and waveguide crystal.We find the generation rate of photon pairs can be increased by about several orders of magnitude in the waveguide chip compared to that in the bulk crystal.An efficient and heralded single photon source can be designed on a PPLN chip by means of the manipulation of two photon frequency correlation.(2)We investigate how to manipulate the tripartite frequency correlation of triplets which are generated from cascaded spontaneous parametric down conversions.A monolithic quadratic nonlinear crystal is designed to contain two segments of periodically poled lithium niobate waveguide as nonlinear mediums to produce cascaded photon pairs both under phase-matching and group velocity-matching conditions.By choosing proper pump bandwidth and crystal length,the tripartite frequency will show a full correlation,partial correlation or no correlation,corresponding a none-separable triplet,separable one photon and biphoton or three separable photons,respectively.At the same time,we found that when the physical parameters were adjusted,the spacetime wave packets of the three photons could show a variety of fine structures.This research plays an important role in understanding the basic properties of multi-body correlation.(3)We theoretically studied another scheme of three-photon entangled state generated from a hybird ?2 nolinear process.To generate a third photon,two idlers from two independent SPDCs are annihilated in a frequency up-conversion process.The corresponding spectral function of the three photon state is derived.In the same way,the frequency correlation of the three-photon can be manipulated by adjusting pump bandwidth and crystal length under extend-phase matching condition.We also analyze the generation rate of three photon produced in a cavity which is composed of high reflective dielectric mirror coatings deposited on the waveguide end faces.We consider two different regimes:Singly resonant cavities where the signal and idler modes are resonant and doubly resonant cavities where the pump mode is also resonant.We also theoretically analyze the basic characteristics of three-photon entangled state generated from the third order nonlinear effects.We found that frequency correlation of the threephoton state can be manipulated by adjusting several physical parameters in order to achieve different types of entanglement.The scheme of integrating all processes and operations on a single chip is proposed to improve the non-linear action intensity and the technical scheme of designing resonant cavity to further increase the multi-photon yield.(4)We theoretically analyze the two different kind of localization effects in quantum walk.First,we revisit the one-dimensional discrete-time three states quantum walk,which is the simplest model that exhibits localization in quantum walk.The key factor of the localization in the three-state quantum walk is the degeneracy of eigenvalues.The evolutionary behavior of the next-nearest neighbors coupling in waveguide array is analogous to the four-state continuous-time quantum walk.When selecting a appropriate value of the relative coupling strength,the localized phenomenon of the optical field is also observed.The reason for the localization can be explained as the appearance of the flat band in the band structure.Compared the two kind of localization effects in discrete-time and continuous-time quantum walk,we find they are consistent in essence.However,they are different from Anderson localization which is caused by disorder in the lattice.