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International audience; This paper describes the generation of directive beams at two different frequencies with the same circular metasurface (MTS) antenna based on a surface wave (SW) excitation. Two methods are presented to achieve the desired bi-chromatic beam operation. The first one consists in mathematically superimposing two MTS modulations, each one matched to the SW wavelength at a different frequency. In the second method, the period of the MTS modulation matches the SW wavelengths at two different frequencies in two different regions of the antenna, i.e., close to the center for the high frequency band and close to the periphery for the low frequency band. The first method allows one to have different feed points for each beam in a self-diplexed structure, although it is also possible to use a single feed configuration and a diplexer. The second approach only holds for a single physical feed-point. Numerical and experimental results are shown. © 2021 Author(s).

Optical localization in strongly disordered photonic media is an attractive topic for proposing novel cavity-like structures. Light interference can produce random modes confined within small volumes, whose spatial distribution in the near-field is predicted to show hot spots at the nanoscale. However, these near-field speckles have not yet been experimentally investigated due to the lack of a high spatial resolution imaging techniques. Here, we study a system where the disorder is induced by random drilling air holes in a GaAs suspended membrane with internal InAs quantum dots. We perform deep-subwavelength near-field experiments in the telecom window to directly image the spatial distribution of the electric field intensity of disordered-induced localized optical modes. We retrieve the near-field speckle patterns that extend over few micrometers and show several single speckles of the order of λ/10 size. The results are compared with the numerical calculations and with the recent findings in the literature of disordered media. Notably, the hot spots of random modes are found in proximity of the air holes of the disordered system., This work was supported by the FET project FP7 618025 CARTOON. This work is part of the research programme of the Foundation for Fundamental Research on Matter (FOM), which is financially supported by the Netherlands Organisation for Scientific Research (NWO), and it is also supported by the Dutch Technology Foundation STW, applied science division of NWO, the Technology Program of the Ministry of Economic Affairs under Project No. 10380. F.B. acknowledges funding from the Italian Ministry for Education, University and Research within the Futuro in Ricerca (FIRB) program (project DeLIGHTeD, Protocollo RBFR12RS1W).

8 pags., 4 figs., Artificial magnetic molecules can contribute to progressing toward large scale quantum computation by (a) integrating multiple quantum resources and (b) reducing the computational costs of some applications. Chemical design, guided by theoretical proposals, allows embedding nontrivial quantum functionalities in each molecular unit, which then acts as a microscopic quantum processor able to encode error protected logical qubits or to implement quantum simulations. Scaling up even further requires “wiring-up” multiple molecules. We discuss how to achieve this goal by the coupling to on-chip superconducting resonators. The potential advantages of this hybrid approach and the challenges that still lay ahead are critically reviewed., We acknowledge funding from the European Union’s Horizon 2020 research and innovation programme (QUANTERA project SUMO, FET-OPEN Grant No. 862893 FATMOLS), the Spanish MICINN (Grant Nos. RTI2018-096075-B-C21, PCI2018-093116, and PGC2018-094792-B-I00), the Gobierno de Aragon (Grant No. E09-17R-Q-MAD), the CSIC Quantum Technology Platform PT-001, and the Italian Ministry of Education and Research (MIUR) through the co-funding of SUMO.