We propose a hybrid photonic-plasmonic resonant structure which consists of a metal nanoparticle (MNP) and a whispering gallery mode (WGM) microcavity. It is found that the hybrid mode enables a strong interaction between the light and matter, and the single-atom cooperativity is enhanced by more than two orders of magnitude compared to that in a bare WGM microcavity. This remarkable improvement originates from two aspects: (1) the MNP offers a highly enhanced local field in the vicinity of an emitter, and (2), surprisingly, the high-Q property of WGMs can be maintained in the presence of the MNP. Thus the present system has great advantages over a single microcavity or a single MNP, and holds great potential in quantum optics, nonlinear optics and highly sensitive biosening.PACS numbers: 42.50. Pq, 42.50.Ct, 42.50.Dv, Owing to the size mismatch between light and single emitters such as single atoms, the interaction between them is very weak, so that it is of importance to create a light-matter interface enabling strong interactions. One way to bridge this mismatch is to employ the strong interaction within cavity quantum electrodynamics (QED) [1,2]. Cavity QED offers an almost ideal platform for the study of physics at the interface of classical and quantum mechanics, and provides a technology for various devices in the field of quantum information [3][4][5]. Experiments on strong coupling regime in cavity QED have made great advances over the past two decades [6]. Among them, whispering gallery mode (WGM) microcavities [7] are promising because they possess ultrahigh quality (Q) factor and allow for mass production on a chip. However, the relatively large cavity mode volume makes it difficult to realize strong coupling. On the other hand, due to the localized surface plasmon resonance (LSPR) [8], metal nanoparticles (MNPs) [9] enable subwavelength confinement of the optical field [10][11][12][13][14]. Unfortunately, MNPs suffer from serious absorption and scattering losses.Against this backdrop, in this Letter, taking advantages from both ultralow-loss WGMs and highly localized plasmon, we propose a WGM microcavity-MNP resonant system. In this composite system, the high-Q WGM microcavity serves as a low-loss storage of the optical field, while the MNP plays the role of an optical antenna which creates a hot spot and magnifies the local optical field. Remarkably, the high-Q property of WGMs can be maintained in the presence of the MNP. As a result, the cooperativity parameter (defined as C = 2G 2 /κγ s [15], with G being the single photon coupling strength, γ s the spontaneous decay of the emitter and κ the decay of the cavity field) achieves a more than 100-fold increase compared with that of the WGM cavity alone. It should be pointed out that, this composite cavity QED structure is significantly different from previous designs where a silica disk or toroid was completely covered with a metal layer, which led to strong degrading of the Q-factor [16,17]. Figure 1 illustrates a schematic of the system. A MNP is ...
We propose a scheme for implementing cross Kerr nonlinearity between two superconducting transmission line resonators (TLR) via their interaction with a coupler which is constructed by two superconducting charge qubits connected to each other via a superconducting quantum interference device. When suitably driven, the coupler can induce very strong cross phase modulation (XPM) between the two TLRs due to its N-type level structure and the consequent electromagnetically induced transparency in its lowest states. The flexibility of our design can lead to various inter-TLR coupling configurations. The obtained cross Kerr coefficient is large enough to allow many important quantum operations in which only few photons are involved. We further show that this scheme is very robust against the fluctuations in solid state circuits. Our numerical calculations imply that the absorption and dispersion resulted from the decoherence of the coupler are very small compared with the strength of the proposed XPM.
Microchromosomes are prevalent in nonmammalian vertebrates [P. D. Waters et al. , Proc. Natl. Acad. Sci. U.S.A. 118 (2021)], but a few of them are missing in bird genome assemblies. Here, we present a new chicken reference genome containing all autosomes, a Z and a W chromosome, with all gaps closed except for the W. We identified ten small microchromosomes (termed dot chromosomes) with distinct sequence and epigenetic features, among which six were newly assembled. Those dot chromosomes exhibit extremely high GC content and a high level of DNA methylation and are enriched for housekeeping genes. The pericentromeric heterochromatin of dot chromosomes is disproportionately large and continues to expand with the proliferation of satellite DNA and testis-expressed genes. Our analyses revealed that the 41-bp CNM repeat frequently forms higher-order repeats (HORs) at the centromeres of acrocentric chromosomes. The centromere core regions where the kinetochore attaches often encompass telomeric sequence (TTAGGG)n, and in a one of the dot chromosomes, the centromere core recruits an endogenous retrovirus (ERV). We further demonstrate that the W chromosome shares some common features with dot chromosomes, having large arrays of hypermethylated tandem repeats. Finally, using the complete chicken chromosome models, we reconstructed a fine picture of chordate karyotype evolution, revealing frequent chromosomal fusions before and after vertebrate whole-genome duplications. Our sequence and epigenetic characterization of chicken chromosomes shed insights into the understanding of vertebrate genome evolution and chromosome biology.
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