Dynamical Gaussian quantum steering in optomechanics

Einstein-Podolski-Rosen steering is a form of quantum correlation exhibiting an intrinsic asymmetry between two entangled systems. In this paper, we propose a scheme for examining dynamical Gaussian quantum steering of two mixed mechanical modes. For this, we use two spatially separated optomechanical cavities fed by squeezed light. We work in the resolved sideband regime. Limiting to the adiabatic regime, we show that it is possible to generate dynamical Gaussian steering via a quantum fluctuations transfer from squeezed light to the mechanical modes. By an appropriate choice of the environmental parameters, one-way steering can be observed in different scenarios. Finally, comparing with entanglement - quantified by the Gaussian R\'enyi-2 entropy-, we show that Gaussian steering is strongly sensitive to the thermal effects and always upper bounded by entanglement degree

Controlling photon–phonon entanglement in a three-mode optomechanical system

In this paper, we consider a three-mode optomechanical system, where two movable mirrors are coupled to a single cavity mode with different optomechanical coupling strengths. Instead of the phonon–phonon entanglement which has often been studied, here we focus on the photon–phonon entanglement. Using the logarithmic negativity, we found that stationary entanglement strongly depends on the temperature, dissipation rates, and optomechanical couplings. Furthermore, the system at hand exhibits an entanglement transfer that can be controlled using only one of the two optomechanical couplings. However, manipulating optomechanical couplings is limited by the stability conditions

Quantifying quantum correlations in a double cavity–magnon system

In this paper, we study a system consisting of two spatially separated cavities, where each cavity contains a magnon mode of YIG sphere coupled to a microwave cavity mode via a linear beam splitter interaction. The two cavities are driven by two-mode squeezed vacuum field. In (Yu et al. in J. Phys. B: At. Mol. Opt. Phys. 53:065402, 2020), it has been investigated about the logarithmic negativity as a measure of quantum entanglement between two magnon modes versus various system parameters. Motivated by this, we will look at two different types of quantum correlations (i.e., entanglement and discord) in two-mode Gaussian subsystems (cavity–cavity modes and magnon–magnon modes). We analyze the robustness of these correlations with respect to the physical and environmental parameters—temperature, squeezing and the cavity–magnon coupling—of the two studied subsystems. For this, we use the Gaussian Bures distance to quantify entanglement and the Gaussian geometric discord (GGD) to quantify correlations beyond entanglement. The entanglement of the two bi-mode subsystems proves to be more sensitive to thermal noise. In particular, under the effect of temperature, the magnon–magnon entanglement degrades much more than the cavity–cavity entanglement. In addition, the GGD is found to be more robust—in both subsystems—against thermal noise, and it can be detected even for high values of temperatures. Also, we show that nonzero quantum correlations can be captured even when entanglement vanishes completely in the two studied subsystems. Finally, two different types of entanglement transfer (i.e., light$$\rightarrow$$light and light$$\rightarrow$$matter) have been observed in the studied system