The Study Of Photon Blockade In Parametrically Amplified Photonic Molecules

In the early twentieth century,quantum mechanics was gradually established.The formation and improvement of quantum mechanics have greatly promoted the development of other disciplines such as atomic physics,solid state physics,nuclear physics and so on.Among them,the combination of quantum mechanics and information science forms a new interdisciplinary subject-quantum information.In quantum information science,the single photon source is the core resource of quantum information technology.Since the single photon source is an important part of quantum information and quantum communication technology,the preparation and operation of single photon source has always been an important research topic.In this paper,we propose a theoretical scheme for the preparation and manipulation of a single photon source in a parametrically amplified photonic molecule.Parametric amplifiers are placed in two cavities coupled by photon tunneling to form a photonic molecule system.Under the coherent driving of the external laser field,there is a significant photon blockade effect in the system.Firstly,in order to understand the phenomenon of photon blockade in the system,we use the Schrodinger equation to approximate the analytical calculation by appropriately truncating the Fock state space of the cavity field.The approximate analytical expression of the second-order correlation function of the system is solved and the optimal conditions for the photon blockade effect in the system are derived.We give the energy level diagram and excitation paths of the system,and explain that the physical mechanism of photon blockade is due to the destructive quantum interference of different two-photon excitation paths.The ideal condition of photon blockade in the system given by the analytical solution shows that we can control the statistical properties of photons better by adjusting the parameters that are easy to control in the experiment,such as adjusting the relative phase between two pump fields and the tunneling rate between two cavity modes.This reduces the difficulty of the experiment and increases the feasibility of the scheme.Secondly,the master equation of photons in the system is obtained by rotating the Hamiltonian of the system,and the statistical properties of the photons are analyzed by solving the second-order correlation function numerically.The approximate analytical solution of the second-order correlation function derived from the schrodinger equation is compared with the numerical solution of the second-order correlation function derived from the master equation.The comparison shows that the results of the two methods are consistent.The optimal conditions for the photon blockade effect given by the analytical solution are further verified by the numerical solution.Finally,we study the influence of several important system parameters(such as the relative phase between two pump fields,the tunneling rate between two cavities and nonlinear gain and so on)on the photon statistical properties of the system.The results show that the system can maintain good photon antibunching properties in a wide range of parameters,which to a certain extent reduces the difficulty of experimental realization of single photon source.In a certain region,the controllable switching from antibunching to bunching(and vice versa)also provides a feasible way to control the statistical properties of photons.Therefore,we can better control the statistical characteristics of photons in the parametrically amplified photonic molecule,which provides a new scheme for the preparation and control of single photon source and injects fresh vitality into the development of quantum information technology.