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We note that the all-optical switching schemes are based on electromagnetically induced transparency. In this paper, we will study the optical switching based on another mechanism, i.e., local single-excitation resonance. The average-photon-number distribution in the steady state is studied in a system of two linearly coupled cavities, where one of cavity includs a two-level atom inside, and the cavity without the atom is driven by a classical light field. We find that the steady-state average-photon-number distribution of the two cavities can be controlled, which means that our scheme can be used as a quantum optical switching. Our finding may has potential application in quantum information and quantum computation. [ABSTRACT FROM AUTHOR]

In reference Sarma and Sarma (Phys. Rev. A 96, 053827, 2017), the photon blockade is studied in a driven cavity via parametric interaction. In this paper, we extend this work and study the influence of the phase of the driving lase to the photon blockade. The conditions for optimized photon anti-bunching are presenting with the phase of the driving lase. By the calculations of the second-order correlation function, we find that the photon blockade is strongly sensitive to the amplitude and the phase of the driving laser. Further, the results of the numerical calculations verify the above analysis. This simple scheme provides an effective way for potential applications in photon manipulation and quantum computation. [ABSTRACT FROM AUTHOR]

In the recent publications (Gerace and Savona, Phys. Rev. A 89(R), 031803 2014; Zhou et al., Opt. Express 24, 17332 2016), the unconventional photon blockades are studied in a three-mode-second-order-nonlinearity system with linear coupling between the two low frequency modes. In this paper, the unconventional photon blockade is studied in a complementary case with linear coupling between the two high frequency modes. By solving the master equation in the steady-state limit and calculating the zerodelay- time second-order correlation function, a strong photon antibunching is found in this three-mode-second-order-nonlinearity system. The optimal antibunching conditions are derived and the numerical simulations confirm the optimal conditions. Our scheme can be used as a tunable single-photon source. [ABSTRACT FROM AUTHOR]

The Hall conductivity given by the Kubo formula is a linear response of quantum transverse transport to a weak electric field. It has been intensively studied for quantum systems without decoherence, but it is barely explored for systems subject to decoherence. In this paper, we develop a formulism to deal with this issue for topological insulators. The Hall conductance of a topological insulator coupled to an environment is derived, the derivation is based on a linear response theory developed for open systems in this paper. As an application, the Hall conductance of a two-band topological insulator and a two-dimensional lattice is presented and discussed. [ABSTRACT FROM AUTHOR]

Anisotropic quantum Rabi model is a generalization of quantum Rabi model, which allows its rotating and counter-rotating terms to have two different coupling constants. It provides us with a fundamental model to understand various physical features concerning quantum optics, solid-state physics, and mesoscopic physics. In this paper, we propose an experimental feasible scheme to implement anisotropic quantum Rabi model in a circuit quantum electrodynamics system via periodic frequency modulation. An effective Hamiltonian describing the tunable anisotropic quantum Rabi model can be derived from a qubit-resonator coupling system modulated by two periodic driving fields. All effective parameters of the simulated system can be adjusted by tuning the initial phases, the frequencies and the amplitudes of the driving fields. We show that the periodic driving is able to drive a coupled system in dispersive regime to ultrastrong coupling regime, and even deep-strong coupling regime. The derived effective Hamiltonian allows us to obtain pure rotating term and counter-rotating term. Numerical simulation shows that such effective Hamiltonian is valid in ultrastrong coupling regime, and stronger coupling regime. Moreover, our scheme can be generalized to the multi-qubit case. We also give some applications of the simulated system to the Schrödinger cat states and quantum gate generalization. The presented proposal will pave a way to further study the stronger anisotropic Rabi model whose coupling strength is far away from ultrastrong coupling and deep-strong coupling regimes in quantum optics. [ABSTRACT FROM AUTHOR]

The spin chain is a system that has been widely studied for its quantum phase transition. It also holds potential for practical application in quantum information, including quantum communication and quantum computation. In this paper, we propose a scheme for conditional state transfer in a Heisenberg XXZ spin chain. In our scheme, the absence or presence of a periodic driving potential results in either a perfect state transfer between the input and output ports, or a complete blockade at the input port. This scheme is formalized by deriving an analytical expression of the effective Hamiltonian for the spin chain subject to a periodic driving field in the high-frequency limit. The influence of the derivation of the optimal parameter on the performance of the state transfer is also examined, showing the robustness of the spin chain for state transfer. In addition, the collective decoherence effect on the fidelity of state transfer is discussed. The proposed scheme paves the way for the realization of integrated quantum logic elements, and may find application in quantum information processing. [ABSTRACT FROM AUTHOR]