Photon Antibunching In A Cavity-QED System With Rydberg-Rydberg Interaction Atoms

Photon antibunching is an important quantum mechanical phenomenon of light,in which photons tend to arrive one by one rather than together.In general,photon antibunching effect in a quantum optical system is caused by the nonlinear energy level of the system,which is called the conventional photon blockade.Recently,another mechanism that enables the system to generate photon blockade has been discovered.This is known as the unconventional photon blockade,and it originates from the interference between the pathways.In the previous theoretical and experimental studies,the above two mechanisms to generate photon antibunching effect are generally used to realize the single photon emitter.In addition,from the study of Rydberg atoms,we know that the Rydberg blockade between Rydberg atoms induces optical nonlinearity in the Rydberg ensemble,and then produces the conventional photon blockade.Therefore,we expect to combine the unconventional photon blockade effect with the conventional photon blockade produced by the Rydberg ensemble,so as to obtain a relatively perfect single photon emitter.In this paper,we investigate photon antibunching in the Rydberg atom-–cavity system.Two two–level Rydberg atoms are embedded in the optical lattice of the cavity.By solving the time–dependent Schr?dinger equation,we obtain the optimal conditions for the system to achieve photon antibunching under the conditions of the atom–driven and cavity–driven scheme respectively.In order to fully reflect the photon characteristics of the Rydberg atom–cavity system,a numerical simulation is carried out by solving the master equation.We find that in the atom–driven scheme,not only the conventional photon blockade induced by energy level nonlinearity,but also the unconventional photon blockade induced by the quantum interference between different pathways occurs in the Rydberg atom–cavity system.For the unconventional photon blockade under the atom-–driven scheme,we find that the larger the cavity field–laser frequency detuning,the stronger the unconventional photon blockade in the system.In the cavity field–laser frequency positive detuning region,the photon antibunching enhances with the increase of Rydberg coupling strength.On the contrary,we find that the photon antibunching weaken with the increase of Rydberg coupling strength when the cavity field–laser frequency detuning is negative.For conventional photon blockade under the atom–driven scheme,we find that the large Rydberg coupling causes strong photon antibunching when the cavity field–laser frequency detuning is positive.More importantly,when we combine the conventional photon blockade and the unconventional photon blockade together,we will get extremely strong photon antibunching in the system,and the average number of photons in the cavity will reach a maximum.In the case of the cavity–driven scheme,we find that the system has a strong interference induced photon antibunching when there is no Rydberg coupling between two Rydberg atoms.With the increase of the Rydberg coupling strength,the unconventional photon blockade decreases gradually.We also find that only when the strength of the driving cavity field is weak,the system can produce strong photon antibunching.By contrast,we also find that the weakening degree of unconventional photon blockade by dipole–dipole interaction is significantly stronger than that of Rydberg coupling.These results will help to guide the implementation of the single photon emitter in the Rydberg atoms–cavity system.