We demonstrate Si-based single core/shell (Si/SiO₂) nanoparticles which exhibit the Fano resonance associated with ultrahigh scattering directionality. The SiO₂ shell plays a crucial role in achieving zero backscattering at the Fano resonance wavelength along with strongly-enhanced forward scattering. As a result, the front-to-back scattering-intensity ratio is five orders of magnitude greater than that of a Si nanoparticle. Furthermore, the Fano resonance wavelength is controlled over the entire visible region by changing the core diameter. The Fano spectra also show distinctive intensity modulations depending on the index of refraction of the surrounding medium. These unique features make Si/SiO₂ nanoparticles promising for the design of low-loss nano-antennas, metamaterials, and other nanophotonic devices.

We fabricated a single-crystalline rubrene microcavity using a simple solution technique and observed cavity polaritons in the microcavity at room temperature (RT). Large Rabi splitting energies were obtained from dispersion of the cavity polaritons. Furthermore, photoluminescence from the cavity polaritons was observed at RT. The findings will be of importance for the application of cavity polaritons.

The visible electromagnetic resonances of Si/SiO2 core–shell nanoparticles are controlled by thermal oxidation. The core–shell nanoparticles comprising silicon and silicon dioxide are fabricated through laser ablation and thermal oxidation. The resonant wavelengths of magnetic and electric dipoles excited in the particles are experimentally demonstrated to be controlled in the visible region by the variation of the core diameter, through thermal oxidation.

We perform a comprehensive numerical analysis on the optical binding forces of a multiple-resonant silicon nanodimer induced by the normal illumination of a plane wave in the visible region. The silicon nanodimer provides either repulsive or attractive forces in water while providing only attractive forces in air. The enhancement of the magnetic dipole mode is attributed to the generation of repulsive forces. The sign (attractive/repulsive) and the amplitude of the optical forces are controlled by incident polarization and separation distance between the silicon nanoparticles. These optomechanical effects demonstrate a key step toward the optical sorting and assembly of silicon nanoparticles.

We show that optically active coupled quantum dots embedded in a superconducting microwave cavity can be used to realize a fast quantum interface between photonic and transmon qubits. Single photon absorption by a coupled quantum dot results in generation of a large electric dipole, which in turn ensures efficient coupling to the microwave cavity. Using cavity parameters achieved in prior experiments, we estimate that bi-directional microwave-optics conversion in nanosecond timescales with efficiencies approaching unity is experimentally feasible with current technology. We also outline a protocol for in-principle deterministic quantum state transfer from a time-bin photonic qubit to a transmon qubit. Recent advances in quantum dot based quantum photonics technologies indicate that the scheme we propose could play a central role in connecting quantum nodes incorporating cavity-coupled superconducting qubits.Introduction. A quantum interface between flying photonic and stationary matter qubits is widely regarded as an essential element of quantum networks [1][2][3]. Remarkable advances over the last decade have established that circuit-QED, consisting of superconducting (SC) qubits non-perturbatively coupled to a common microwave (MW) cavity, is particularly promising for realization of small-scale quantum information processors [4,5]. The most prominent limitation in realization of quantum networks consisting of circuit-QED based processors is the difficulty in transferring quantum information over distances exceeding meters. Motivated by overcoming this roadblock, several groups have embarked on research aimed at creating a quantum interface between SC qubits and propagating photonic qubits. Among the several ingenuous proposals [6][7][8][9][10][11][12][13][14][15] to resolve this conundrum, the approach based on using optomechanical coupling [16][17][18][19][20] has proven to be particularly successful: pioneering experiments have demonstrated conversion efficiency of 10% with a bandwidth of 30 kHz [20]. A limitation for most if not all of these approaches is the relatively small effective coupling strength between the single optical and MW photons, which in turn prevents conversion of quantum information on time-scales much shorter than typical SC qubit coherence times.

Laser-scanning-assisted tip-enhanced optical microscopy was developed for robust optical nanospectroscopy. The laser-scanning system was utilized to automatically set and keep the center of a tight laser-focusing spot in the proximity of a metallic tip with around 10 nm precision. This enabled us to efficiently and stably induce plasmon-coupled field enhancement at the apex of the metallic probe tip. The laser-scanning technique was also applied to tracking and compensating the thermal drift of the metallic tip in the spot. This technique is usable for long-term tip-enhanced optical spectroscopy without any optical degradation.

No abstract

Quantum transducers between microwave and optical photons are essential for long-distance quantum networks based on superconducting qubits. An optically active self-assembled quantum dot molecule (QDM) is an attractive platform for the implementation of a quantum transducer because an exciton in a QDM can be efficiently coupled to both optical and microwave fields at the single-photon level. Recently, the transduction between microwave and optical photons has been demonstrated with a QDM integrated with a superconducting resonator. In this paper, we present a design of a QD-high impedance resonator device with a low microwave loss and an expected large single-microwave photon coupling strength of 100s of MHz. We integrate self-assembled QDs onto a high-impedance superconducting resonator using a transfer printing technique and demonstrate a low-microwave loss rate of 1.8 MHz and gate tunability of the QDs. The corresponding microwave photon decay time of 88 ns is longer than the time necessary for the optical-microwave transduction process as well as the transmon-resonator swap operation time. This feature will facilitate efficient quantum transduction between an optical and microwave qubit.