Deterministic coupling between photonic nodes in a quantum network is an essential step toward implementing various quantum technologies. The omnidirectionality of free-standing emitters, however, makes this coupling highly inefficient, in particular if the distant nodes are coupled via low numerical aperture (NA) channels such as optical fibers. This limitation requires placing quantum emitters in nanoantennas that can direct the photons into the channels with very high efficiency. Moreover, to be able to scale such technologies to a large number of channels, the placing of the emitters should be deterministic. In this work, we present a method for directly locating single free-standing quantum emitters with high spatial accuracy at the center of highly directional bullseye metal–dielectric nanoantennas. We further employ non-blinking, high quantum yield colloidal quantum dots for on-demand single-photon emission that is uncompromised by instabilities or non-radiative exciton recombination processes. Taken together, this approach results in a record-high collection efficiency of 85% of the single photons into a low NA of 0.5, setting the stage for efficient coupling between on-chip, room temperature nanoantenna-emitter devices and a fiber or a remote free-space node without the need for additional optics.

Engineering the directionality and emission rate of quantum light sources is essential in the development of modern quantum applications. In this work we use numerical calculations to optimize the brightness of a broadband quantum emitter positioned in a hybrid metal-dielectric circular periodic nanoantenna. The optimized structure features a photon collection efficiency of 74% (82%) and a photon flux enhancement of over 10 (6) into a numerical aperature of 0.22 (0.50) respectively, corresponding to a direct coupling into two types of multimode fibers. In order to enhance the emission rate, we present a new circular nanoantenna design where a quantum emitter is attached to a silver nanocone at the center of the antenna. After optimization, we find a collection efficiency of 61% (78%) into a numerical aperature of 0.22 (0.50), giving a brightness enhancement of 1000 (600) for an unpolarized emitter. The enhancements in both structures are broadband due to the low quality factor of the device and are therefore ideal for room-temperature sources. This type of a scalable design can be utilized towards on-chip, high brightness quantum light sources operating at room temperature. arXiv:1703.00163v2 [physics.optics] 1 May 2017

Efficient, high rate photon sources with high single photon purity are essential ingredients for quantum technologies. Single photon sources based on solid state emitters such as quantum dots are very advantageous for integrated photonic circuits, but they can suffer from a high two-photon emission probability, which in cases of non-cryogenic environment cannot be spectrally filtered. Here we propose two temporal purificationby-heralding methods for using a two photon emission process to yield highly pure and efficient single photon emission, bypassing the inherent problem of spectrally overlapping bi-photon emission at elevated temperatures. We experimentally emulate their feasibility on the emission from a single nanocrystal quantum dot at room temperature, 1 arXiv:1805.00201v4 [quant-ph]

Single quantum emitters coupled to different plasmonic and photonic structures are key elements for integrated quantum technologies. In order to fully exploit these elements, e.g., for quantum enhanced sensors or quantum repeaters, a reliable fabrication method as enabling technology is crucial. In this work, we present a method that allows for positioning of individual nanocrystals containing single quantum light sources on non-transparent conductive samples with sub-micrometer precision. We induce long-range electrostatic forces between an atomic force microscope tip, which carries a nanoparticle, and the target surface. This allows for mapping of the target area in the non-contact mode. Then, the placement site can be identified with high accuracy without any tip approach, eliminating the risk of a particle loss. We demonstrate the strength of the method by transferring a diamond nanocrystal containing a single nitrogen-vacancy defect to the center of a micrometer-sized silver bullseye antenna with nanometer resolution. Our approach provides a simple and reliable assembling technology for positioning single nano-objects on opaque substrates with high reproducibility and precision.

Deterministic GHz-rate single photon sources at room-temperature would be essential components for various quantum applications. However, both the slow intrinsic decay rate and the omnidirectional emission of typical quantum emitters are two obstacles towards achieving such a goal which are hard to overcome simultaneously. Here we solve this challenge by a hybrid approach, using a complex monolithic photonic resonator constructed of a gold nanocone responsible for the rate enhancement, and a circular Bragg antenna for emis-1 arXiv:2010.15016v2 [quant-ph] 3 Nov 2020 sion directionality. A repeatable process accurately binds quantum dots to the tip of the antenna-embedded nanocone. As a result we achieve simultaneous 20-fold emission rate enhancement and record-high directionality leading to an increase in the observed brightness by a factor as large as 580 (120) into an NA = 0.22 (0.5). We project that such miniaturised on-chip devices can reach photon rates approaching 2.3 × 10 8 single photons/second thus enabling ultrafast light-matter interfaces for quantum technologies at ambient conditions.