We propose a scheme to generate squeezed states of magnon and phonon modes and verify squeezing transfer between different modes of distinct frequencies in a cavity magnomechanical system which is composed of a microwave cavity and a yttrium iron garnet sphere. We present that by activating the magnetostrictive force in the ferrimagnet, realized by driving the magnon mode with red-detuned and blue-detuned microwave fields, the driven magnon mode can be prepared in a squeezed state. Moreover, the squeezing can be transferred to the cavity mode via the cavity-magnon beamsplitter interaction with strong magnomechanical coupling. We show that under the weak coupling regime, large mechanical squeezing of phonon mode can be achieved, which verifies that our scheme can find the existence of quantum effects at macroscopic scales. Furthermore, distinct parameter regimes for obtaining large squeezing of the magnons and phonons are given, which is the principal feature of our scheme. The considered scheme can be extended to hybrid optical systems, and can facilitate the advancement for realization of strong mechanical squeezing in cavity magnomechanical systems.

We study the effects of parity-time ($\mathcal{PT}$) symmetry on the photon blockade and distinguish the different blockade mechanisms in a double-cavity optomechanical system. By studying the light statistics of the system, we find the completely different photon blockade behaviors when the $\mathcal{PT}$ symmetry is broken or unbroken, which is related to the $\mathcal{PT}$ phase transition. Furthermore, an interesting phenomenon that the two cavities are blocked at the same time is found with the appropriate system parameters. Those statistical phenomena are all analyzed in detail and demonstrated by analytically solving the Schrödinger equation and numerically simulating the master equation, respectively. Finally, we also consider the non-$\mathcal{PT}$-symmetric situations which further reveal the physical essence of the photon blockade by comparing those results. Different from the usual photon blockade, our proposal is feasible even with weak parameter mechanism, i.e., the proposal neither requires the strong optomechanical coupling nor the large tunneling coupling between cavities.

Using linear optical manipulation, single photons, entangled photon pairs, photon measurement, and classical communication, we propose a scheme for a two-spin-qubit phase gate and the teleportation of a controlled-not gate between two electron spins from acting on local qubits to acting on remote qubits using quantum dots in optical microcavities. The scheme is based on spin selective photon reflection from the cavity and is achieved in a deterministic way by the sequential detection of photons and the single-qubit rotations of a single electron spin in a self-assembled GaAs-InAs quantum dot. The feasibility of the scheme is assessed showing that high average fidelities of the gates are achievable in the weak-coupling regime when the side leakage and cavity loss are low. The scheme opens promising possibilities for long-distance quantum communication, distributed quantum computation, and construction of remote quantum-information-processing networks.

A scheme is proposed to cool a rotating mirror close to its ground state in a double-Laguerre-Gaussian-cavity optomechanical system, where an auxiliary cavity and a two-level atomic ensemble simultaneously couple to the original optomechanical cavity. By choosing parameters reasonably, we find that the cooling process of the rotating mirror can be strengthened greatly while the heating process can be suppressed effectively. We show that the proposed ground-state cooling scheme can work well no matter whether in the weak or strong coupling regime for the atomic ensemble and original cavity. Compared with previous related schemes, our scheme works in the unresolved sideband regime with fewer strict limitations for the auxiliary systems.

We propose a simple scheme to generate quantum entanglement and one-way steering between distinct mode pairs in a generic cavity magnomechanical system, which is composed of a microwave cavity and a yttrium iron garnet sphere supporting magnon and phonon modes. The microwave cavity is pumped by a weak squeezed vacuum field, which plays an important role for establishing quantum entanglement and steering. It is found that when the magnon mode is driven by the red-detuned laser, the maximum entanglement between cavity mode and phonon mode and the maximum phonon-to-photon one-way steering can be effectively generated via adjusting the ratio of two coupling rates. While under the much weaker magnomechanical coupling, the quantum entanglement and one-way steering between cavity mode and magnon mode can be achieved, where the steering direction is determined merely by the relative dissipation strength of the cavity to the magnon mode. More interestingly, we reveal that the robustness to the temperature for entanglement and steering between any mode pairs can be evidently enhanced by selecting the squeezing parameter appropriately.