Search

Microwave-optics entanglement plays a crucial role in building hybrid quantum networks with quantum nodes working in the microwave and optical frequency bands. However, there are limited efficient ways to produce such entanglement due to the large frequency mismatch between the two regimes. Here, we present a new mechanism to prepare microwave-optics entanglement based on a hybrid system of two coupled opto- and magnomechanical microspheres, i.e., a YIG sphere and a silica sphere. The YIG sphere holds a magnon mode and a vibration mode induced by magnetostriction, while the silica sphere supports an optical whispering-gallery mode and a mechanical mode coupled via an optomechanical interaction. The two mechanical modes are close in frequency and directly coupled via physical contact of the two microspheres. We show that by simultaneously activating the magnomechanical (optomechanical) Stokes (anti-Stokes) scattering, stationary entanglement can be established between the magnon and optical modes via mechanics-mechanics coupling. This leads to stationary microwave-optics entanglement by further coupling the YIG sphere to a microwave cavity and utilizing the magnon-microwave state swapping. Our protocol is within reach of current technology and may become a promising new approach for preparing microwave-optics entanglement, which finds unique applications in hybrid quantum networks and quantum information processing with hybrid quantum systems., Comment: accepted to Laser Photonics Reviews

We show how to prepare magnonic squeezed states in an optomagnomechanical system, in which magnetostriction induced mechanical displacement couples to an optical cavity via radiation pressure. We discuss two scenarios depending on whether the magnomechanical coupling is linear or dispersive. We show that in both cases the strong mechanical squeezing obtained via two-tone driving of the optical cavity can be efficiently transferred to the magnon mode. In the linear coupling case, stationary magnon squeezing is achieved; while in the dispersive coupling case, a transient magnonic squeezed state is prepared in a two-step protocol. The proposed magnonic squeezed states find promising applications in quantum information processing and quantum sensing using magnons., Comment: Special Topic on "Brillouin Scattering and Optomechanics" in APL Photonics

Exciton optomechanics, bridging cavity exciton polaritons and optomechanics, opens new opportunities for the study of light-matter strong interactions and nonlinearities, due to the rich nonlinear couplings among excitons, phonons, and photons. Here, we propose to entangle two exciton modes in an exciton-optomechanics system, which consists of a semiconductor microcavity integrated with two quantum wells. The quantum wells support two exciton modes, which simultaneously couple to an optical cavity mode via a linear dipole interaction and to a mechanical vibration mode via a nonlinear deformation potential interaction. We show that by strongly driving the microcavity with a red-detuned laser field and when the two exciton modes are respectively resonant with the Stokes and anti-Stokes sidebands scattered by the mechanical motion, stationary entanglement between the two exciton modes can be established under realistic parameters. The protocol is within reach of current technology and may become a promising approach for preparing excitonic entanglement.

To go beyond quantum optics in free-space setups, atom-light interfaces with structured photonic environments are often employed to realize unconventional quantum electrodynamics (QED) phenomena. However, when employed as quantum buses, those long-distance nanostructures are limited by fabrication disorders. In this work, we alternatively propose to realize structured lightmatter interactions by engineering multiple coupling points of hybrid giant atom-conventionalenvironments without any periodic structure. We present a generic optimization method to obtain the real-space coupling sequence for multiple coupling points. We report a broadband chiral emission in a very wide frequency regime, with no analog in other quantum setups. Moreover, we show that the QED phenomena in the band gap environment, such as fractional atomic decay and dipole-dipole interactions mediated by a bound state, can be observed in our setup. Numerical results indicate that our proposal is robust against fabrication disorders of the coupling sequence. Our work opens up a new route for realizing unconventional light-matter interactions., Comment: 19 pages, 11 figures

We propose a novel quantum electrodynamics (QED) platform where quantum emitters interact with a Hofstadter-ladder waveguide. We demonstrate several intriguing phenomena stemming from the exotic dispersion relation and vacuum mode properties led by the effective spin-orbit coupling, which have no analog in other QED setups. First, by assuming emitter's frequency to be resonant with the lower band, we find that the spontaneous emission is chiral with most photonic field decaying unidirectionally. Both numerical and analytical results indicate that the Hofstadter-ladder waveguide can be engineered as a well-performed chiral quantum bus. Second, the dynamics of emitters of giant atom form is explored by considering their frequencies below the lower band. Due to quantum interference, we find that both the emitter-waveguide interaction and the amplitudes of bound states are periodically modulated by giant emitter's size. The periodical length depends on the positions of energy minima points induced by the spin-orbit coupling. Last, we consider the interaction between two giant emitters mediated by bound states, and find that their dipole-dipole interaction vanishes (is enhanced) when maximum destructive (constructive) interference happens., Comment: 13 pages; 8 figures

It is interesting to ask whether electron interaction can turn a topologically trivial superconductor into a nontrivial one without the presence of spin-obital coupling. In this paper we solve a correlated $s$-wave superconducting model exactly. The variation of the fermion number parity of the superconducting ground state as a function of the electron interaction is calculated and the topological phase diagram is obtained. Topological $s$-wave superconducting states are revealed in the doped Mott insulators, which is further confirmed by the numerical investigation of the topological boundary zero mode., Comment: 6 pages, 4 figures