Search

We study multiphoton blockade effects in a single-mode cavity interacting with two three-level atoms in $\Lambda$-configuration having position-dependent atom-field coupling. We consider the effects of dipole-dipole interaction (DDI) between the three-level atoms and show how the presence of DDI strongly influences the multiphoton blockade. For symmetric coupling of the atoms with the field, the DDI induces an asymmetry in the emission spectra as a function of pump field detuning. At positive detuning, the single-photon blockade gets stronger as a function of DDI strength, leading to photon antibunching. However, it becomes weaker at negative detuning and can also completely vanish. We show that this vanishing single-photon blockade is associated with a strong two-photon blockade, leading to two-photon bunching. Therefore, by just tuning the frequency of the pump field, we can achieve two very distinct features. We also study the effects of DDI when the atoms are asymmetrically coupled with the field and show that the proposed system exhibits two-photon bunching. We believe our results are important for the experimental realization of such systems where DDI may be present., Comment: 12 pages, 10 figures

We propose a method to enhance bipartite and tripartite entanglement in cavity magnomechanics using an optical parametric amplifier (OPA). We analyze this system and identified parametric regimes where different types of entanglement are enhanced. We show that a proper choice of the phase of the parametric amplifier leads to the enhancement of the bipartite entanglements. Moreover, the tripartite entanglement is also significantly enhanced in the presence of OPA. The OPA not only enhances the strength of entanglement but also increases the domain of entanglement over a wider space of detunings as compared to the system when no OPA is present. Similarly, the robustness of entanglement against temperature is also enhanced. Another important consequence of OPA is the fact that it relaxes the requirement of strong magnon-phonon coupling to generate cavity-magnon entanglement which is necessary for the case when OPA is not present. We believe that the presented scheme is a step forward to realize robust quantum entanglement using current technology., Comment: 8 pages, 7 figures

Zero-photon catalysis (ZPC) introduces noiseless attenuation and can be implemented by existing technologies in quantum key distribution (QKD) protocols. In this paper, we present a ZPC-based eight-state measurement-device-independent continuous-variable QKD (MDI-CV-QKD) combined with discrete modulation and reverse reconciliation. This ZPC-involved eight-state protocol shows better efficiency in terms of optimal modulation variances, secret key rates, transmission distances, tolerable excess noises, and reconciliation efficiency compared to the eight-state protocol without ZPC, the four-state protocol without ZPC, and the four-state protocol with ZPC, at a low signal-to-noise ratio (SNR)., Comment: 11 pages, 9 Figures

We propose a scheme to study coherent control of the atomic Talbot effect using an N-type four-level atomic system in the Raman regime. We show that the intensity of the atomic Talbot image can be efficiently manipulated using Rabi frequency of the control field. However, this manipulation strongly depends on the proper choice of Raman and control field detunings. In particular, the sign of control field detuning leads to two distinct features. In one case, the intensity increases up to a maximum as a function of the control field, followed by a decreasing trend, while in other case, we find only a monotonically decreasing trend.