Manipulation of nonreciprocal unconventional photon blockade in a cavity-driven system composed of an asymmetrical cavity and two atoms with weak dipole–dipole interaction

We present a work of manipulating collective unconventional photon blockade(UCPB)and nonreciprocal UCPB(NUCPB)in a cavity-driven system composed of an asymmetrical single-mode cavity and two interacting identical twolevel atoms(TLAs).When the atoms do not interact directly,the frequency and intensity restrictions of collective UCPB can be specified,and a giant NUCPB exists due to the splitting of optimal atom–cavity coupling strength in proper parameter regime.However,if a weak atom–atom interaction which provides a new and feeble quantum interference pathway to UCPB is taken into account,two restrictions of UCPB are combined complexly,which are rigorous to be matched simultaneously.Due to the push-and-pull effect induced by weak dipole–dipole interaction,the UCPB regime is compressed more or less.NUCPB is improved as a higher contrast is present when the two complex UCPB restrictions are matched,while it is suppressed when the restrictions are mismatched.In general,whether NUCPB is suppressed or promoted depends on its working parameters.Our findings show a prospective access to produce giant quantum nonreciprocity by a couple of weakly interacting atoms.

Unconventional photon blockade in a three-mode system with double second-order nonlinear coupling

The unconventional photon blockade(UPB)for low-frequency mode is investigated in a three-mode system with double second-order nonlinearity.By analyzing the Hamiltonian of the system,the optimal analytic condition of UPB in low-frequency mode is obtained.The numerical results are calculated by solving the master equation in a truncated Fock space,which agrees well with the analytic conditions.Through the numerical analysis of the system,it is found that the weak driving strength is favorable for the system to realize the UPB effect,and the system is insensitive to the changes of attenuation rate and environmental temperature.The comparison with the two-mode system and another similar threemode system shows that,under similar system parameters,the UPB effect of this double two-order nonlinear system is more obvious.

Unconventional photon blockade induced by the self-Kerr and cross-Kerr nonlinearities

We study the use of the self-Kerr and cross-Kerr nonlinearities to realize strong photon blockade in a weakly driven,four-mode optomechanical system.According to the Born–Oppenheimer approximation,we obtain the cavity self-Kerr coupling and the inter-cavity cross-Kerr coupling,adiabatically separated from the mechanical oscillator.Through minimizing the second-order correlation function,we find out the optimal parameter conditions for the unconventional photon blockade.Under the optimal conditions,the strong photon blockade can appear in the strong or weak nonlinearities.