Photon blockade is an effective way to generate single photon, which is of great significance in quantum state preparation and quantum information processing. Here we investigate the statistical ...properties of photons in a double-cavity optomechanical system with nonreciprocal coupling, and explore the photon blockade in the weak and strong coupling regions respectively. To achieve the strong photon blockade, we give the optimal parameter relations under different blockade mechanisms. Moreover, we find that the photon blockades under their respective mechanisms exhibit completely different behaviors with the change of nonreciprocal coupling, and the perfect photon blockade can be achieved without an excessively large optomechanical coupling, i.e., the optomechanical coupling is much smaller than the mechanical frequency, which breaks the traditional cognition. Our proposal provides a feasible and flexible platform for the realization of single-photon source.
The magnon blockade effect in a parity‐time (PT) symmetric‐like three‐mode cavity magnomechanical system involving the magnon–photon and magnon–phonon interactions is investigated. In the broken and ...unbroken PT‐symmetric regions, the second‐order correlation function is calculated analytically and numerically, respectively, and the optimal value of detuning is further determined. By adjusting different system parameters, the different blockade mechanisms are studied and it is found that the perfect magnon blockade effect can be observed under the weak parameter mechanism. This work paves a way to achieve the magnon blockade in experiment.
Based on a parity‐time symmetric‐like three‐mode cavity magnomechanical system, a new type of magnon blockade scheme is proposed. The magnon blockade effect in different blockade mechanisms is discussed. It is found that the perfect magnon blockade effect can be obtained under the weak parameter mechanism. This work paves a way to achieve the magnon blockade in experiment.
We report that linker ligand substitution involving just one atom induces a shape‐memory effect in a flexible coordination network. Specifically, whereas SIFSIX‐23‐Cu, Cu(SiF6)(L)2n, ...(L=1,4‐bis(1‐imidazolyl)benzene, SiF62−=SIFSIX) has been previously reported to exhibit reversible switching between closed and open phases, the activated phase of SIFSIX‐23‐CuN, Cu(SiF6)(LN)2n (LN=2,5‐bis(1‐imidazolyl)pyridine), transformed to a kinetically stable porous phase with strong affinity for CO2. As‐synthesized SIFSIX‐23‐CuN, α, transformed to less open, γ, and closed, β, phases during activation. β did not adsorb N2 (77 K), rather it reverted to α induced by CO2 at 195, 273 and 298 K. CO2 desorption resulted in α′, a shape‐memory phase which subsequently exhibited type‐I isotherms for N2 (77 K) and CO2 as well as strong performance for separation of CO2/N2 (15/85) at 298 K and 1 bar driven by strong binding (Qst=45–51 kJ/mol) and excellent CO2/N2 selectivity (up to 700). Interestingly, α′ reverted to β after re‐solvation/desolvation. Molecular simulations and density functional theory (DFT) calculations provide insight into the properties of SIFSIX‐23‐CuN.
Linker engineering of a flexible SiF62− (SIFSIX) pillared network via single atom substitution profoundly changes the sorption behavior and affords a kinetically stable shape‐memory material. The ‘memorized’ open phase efficiently purifies a CO2/N2 (15/85) mixture in a manner which would be infeasible for the nonporous variant.
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.
A hybrid optomechanical system which is composed of an atomic ensemble and a standard optomechanical cavity driven by a periodically modulated external laser field is investigated. Based on the ...simple periodic modulation forms of the driving amplitude and effective optomechanical coupling, respectively, the atom‐mirror entanglement is discussed in detail. It is found that the maximum of the entanglement in the unresolved‐sideband regime can be further enhanced compared with the non‐modulation regime. On the other hand, we find that the introduction of the atomic ensemble permits the mechanical squeezing induced by the periodic amplitude modulation can be successfully generated even in the unresolved‐sideband regime. Due to the self‐cooling mechanism constructed by the atomic ensemble, the mechanical squeezing scheme no longer requires the extra precooling technologies.
The periodic modulation technologies of the driving amplitude and effective optomechanical coupling are applied to a hybrid optomechanical system which is composed of an atomic ensemble and a standard optomechanical cavity. The modulation not only further enhances the maximum of the atom‐mirror entanglement in an unresolved‐sideband cavity, but also successfully generates the mechanical squeezing in the unresolved‐sideband regime.
We propose a scheme to show that the system consisting of two macroscopic oscillators separated in space which are coupled through Coulomb interaction displays the classical-to-quantum transition ...behavior under the action of optomechanical coupling interaction. Once the optomechanical coupling interaction disappears, the entanglement between the two separated oscillators disappears accordingly and the system will return to classical world even though there exists sufficiently strong Coulomb coupling between the oscillators. In addition, resorting to the squeezing of the cavity field generated by an optical parametric amplifier inside the cavity, we discuss the effect of squeezed light driving on this classical-to-quantum transition behavior instead of injecting the squeezed field directly. The results of numerical simulation show that the present scheme is feasible and practical and has stronger robustness against the environment temperature compared with previous schemes in current experimentally feasible regimes. The scheme might possibly help us to further clarify and grasp the classical-quantum boundary.
Closed-to-open structural transformations in flexible coordination networks are of potential utility in gas storage and separation. Herein, we report the first example of a flexible SiF6 2–-pillared ...square grid material, Cu(SiF6)(L)2 n (L = 1,4-bis(1-imidazolyl)benzene), SIFSIX-23-Cu. SIFSIX-23-Cu exhibits reversible switching between nonporous (β1) and several porous (α, γ1, γ2, and γ3) phases triggered by exposure to N2, CO2, or H2O. In addition, heating β1 to 433 K resulted in irreversible transformation to a closed polymorph, β2. Single-crystal X-ray diffraction studies revealed that the phase transformations are enabled by rotation and geometrical contortion of L. Density functional theory calculations indicated that L exhibits a low barrier to rotation (as low as 8 kJmol–1) and a rather flat energy surface. In situ neutron powder diffraction studies provided further insight into these sorbate-induced phase changes. SIFSIX-23-Cu combines stability in water for over a year, high CO2 uptake (ca. 216 cm3/g at 195 K), and good thermal stability.
The various properties of the output spectrum for a probe field in a hybrid optomechanical system that is composed of two cavities, each containing an atomic ensemble and a mechanical resonator, is ...analyzed. Also, the normal‐mode splitting behaviors induced by the interactions between subsystems in detail are discussed and their respective effects are clarified. The interpretations for the linear variation of the separation between two absorption peaks is given out. In the available parameter regime, three tunnel coupling critical points, which describe the transition behaviors between absorption and amplification, are determined. Based on the first critical point, the influence of the two‐level atomic ensemble on absorption (amplification) effect is studied. The effect of the two‐level atomic ensemble not only splits the absorption peak (amplification dip), but also realizes the enhancement of the absorption (amplification) effect and the transformation between absorption and amplification effects. Meanwhile, the one‐to‐one correspondence location relations between the transparency dip and absorption peak for the double optomechanically induced transparency‐like and optomechanically induced absorption‐like, respectively, are also investigated. With a multi‐level atomic ensemble, the multi‐transparency (absorption) effect is realized readily. These rich spectrum properties of the probe field may benefit forward achieving of the optical switch in experiment and possible applications in coherent control of light pulses.
The influence of the atomic ensemble on output spectrum is studied in the hybrid optomechanical system in detail. The effect of atomic ensemble not only enhances absorption (amplification) phenomenon, but also realizes the transformation between absorption and amplification phenomena. Furthermore, the multi‐transparency (absorption) effect appears with a multi‐level atomic ensemble.
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.
PDF
