Miniaturization of quantum optical devices down to μm-dimensions and integration into fibre optical networks is a major prerequisite for future implementations of quantum information communication and processing applications. Also scalability, long-term stability and room-temperature operation are important properties of such devices. Lately there have been major improvements in down-sizing logical structures and functionalizing optical fibers. Here we present an alignment free, μm-scale single photon source consisting of a single quantum emitter on an optical fiber operating at room temperature. It easily integrates into fiber optic networks for quantum cryptography or quantum metrology applications. Near-field coupling of a single nitrogen-vacancy center is achieved in a bottom-up approach by placing a pre-selected nanodiamond directly on the fiber facet. Its high photon collection efficiency is equivalent to a far-field collection via an objective with a numerical aperture of 0.82. Furthermore, simultaneous excitation and recollection through the fiber is possible introducing a fiber-connected single emitter sensor that allows near-field probing with quantum mechanical properties.
Miniaturization of quantum optical devices down to μm-dimensions and integration into fibre optical networks is a major prerequisite for future implementations of quantum information communication and processing applications. Also scalability, long-term stability and room-temperature operation are important properties of such devices. Lately there have been major improvements in down-sizing logical structures and functionalizing optical fibers. Here we present an alignment free, μm-scale single photon source consisting of a single quantum emitter on an optical fiber operating at room temperature. It easily integrates into fiber optic networks for quantum cryptography or quantum metrology applications. Near-field coupling of a single nitrogen-vacancy center is achieved in a bottom-up approach by placing a pre-selected nanodiamond directly on the fiber facet. Its high photon collection efficiency is equivalent to a far-field collection via an objective with a numerical aperture of 0.82. Furthermore, simultaneous excitation and recollection through the fiber is possible introducing a fiber-connected single emitter sensor that allows near-field probing with quantum mechanical properties.
An alignment free, micrometer-scale single photon source consisting of a single quantum emitter on an optical fiber operating at room temperature is demonstrated. It easily integrates into fiber optic networks for quantum cryptography or quantum metrology applications.(1) Near-field coupling of a single nitrogen-vacancy center is achieved in a bottom-up approach by placing a preselected nanodiamond directly on the fiber facet. Its high photon collection efficiency is equivalent to a far-field collection via an objective with a numerical aperture of 0.82. Furthermore, simultaneous excitation and re-collection through the fiber is possible by introducing a fiber-connected single emitter sensor.
Further miniaturization of funcionalized quantum optical systems down to nm-dimensions and their integration into fibre optical networks is a major challange for future implementations of quantum information, quantum communication and quantum processing applications. Furthermore, scalability, long-term stability and room- as well as liquid helium temperature operation are benchmarking properties of such systems. In this paper, we present the realizations of fiber-coupled diamond-based single photon systems. First, an alignment free, μm-scale single photon source consisting of a single nitrogen vacancy center facet coupled to an optical fiber operating at room temperature is presented. Near-field coupling of the single nitrogen vacancy center is realized by placing a pre-selected nanodiamond directly on the fiber facet in a bottom-up approach. Its photon collection efficiency is comparable to a far-field collection via an air objective with a numerical aperture of 0.82. As the system can be simultaneously excited and its photons be recollected through the fiber, it can be used as a fiber-connected single quantum sensor that allows optical near-field probing on the quantum level. Secondly single nanodiamonds that contain nitrogen vacancy defect centers, are near-field coupled to a tapered fiber of 300 nanometer in diameter. This system provides a record-high number of 97 kcps single photons from a single defect center into a single mode optical fiber. The entire system can be cooled to liquid Helium temperatures and reheated without breaking. Furthermore, the system can be evanescently coupled to various nanophotonic structures, e.g. microresonators. The system can also be applied for integrated quantum transmission experiments and the realization of two-photon interference. It can be used as a quantum-randomnumber generator as well as a probe for nano-magnetometry.
A central goal in quantum information science is to efficiently interface photons with single optical modes for quantum networking and distributed quantum computing. Here, we introduce and experimentally demonstrate a compact and efficient method for the low-loss coupling of a solid-state qubit, the nitrogen vacancy (NV) center in diamond, with a single-mode optical fiber. In this approach, single-mode tapered diamond waveguides containing exactly one high quality NV memory are selected and integrated on tapered silica fibers. Numerical optimization of an adiabatic coupler indicates that near-unity-efficiency photon transfer is possible between the two modes. Experimentally, we find an overall collection efficiency between 16% and 37% and estimate a single photon count rate at saturation above 700 kHz. This integrated system enables robust, alignment-free, and efficient interfacing of single-mode optical fibers with single photon emitters and quantum memories in solids.
We report the realization of a device based on a single Nitrogen-Vacancy (NV) center in diamond coupled to a fiber-cavity for use as single photon source (SPS). The device consists of two concave mirrors each directly fabricated on the facets of two optical fibers and a preselected nanodiamond containing a single NV center deposited onto one of these mirrors. Both, cavity in- and out-put are directly fiber-coupled, and the emission wavelength is easily tunable by variation of the separation of the two mirrors with a piezo-electric crystal. By coupling to the cavity, we achieve an increase of the spectral photon rate density by two orders of magnitude compared to free-space emission of the NV center. With this work, we establish a simple all-fiber based SPS with promising prospects for the integration into photonic quantum networks.
The development of integrated quantum technologies relies on efficient single-photon sources and deterministic quantum operations. Solid-state quantum emitters coupled to nanophotonic structures present a promising solution. This work investigates color centers in nanodiamonds,particularly Germanium Vacancy (GeV) [1], Silicon Vacancy (SiV), and Magnesium Vacancy (MgV) centers, a novel, understudied emitter [2], at both room and cryogenic temperatures. These nanodiamonds are chosen for their stability and superior coherence properties at cryogenic conditions. To collect their emission we have successfully deposited a single GeV- nanodiamond on tapered optical nanofibers by gently contacting a diluted droplet to the nanofiber [3], demonstrating an average coupling of 15% into a conventional optical fiber through the confined evanescent field of the nanofiber mode and single photon emission. Building on this achievement, we aim to study the system at cryogenic temperatures, which should enable the demonstration of efficient and indistinguishable single photons coupling to conventional optical fibers.Current collection efficiencies are intrinsically limited to 30% with the nanofiber[4], and improving light-matter coupling efficiency remains a key goal for high-performance single-photon sources and more advanced applications.To achieve this, we are investigating a newly developed technique [5]: the deterministic fabrication of dielectric and plasmonic nanostructures directly on the nanofiber surface using an “electron beam induced deposition” (EBID). The precision and versatility of this technique openthe way to different applications: Purcell enhancement of the quantum emitter emission using metallic nanoantennas and efficient light-matter coupling using dielectric structures. Our first calculation shown that optimizing the composition, geometry, and placement of these nanostructures a simple pattern of carbon pillars around the emitter should increase coupling efficiency up to 69% while maintaining high transmission in the nanofiber. We also demonstratethe fabrication of those nanostructures on top of the nanofiber.This work advances integrated nanophotonic devices for single-photon sources.[1] M. Nahra et al.,Single germanium vacancy centers in nanodia-monds with bulk-like spectral stability, AVS Quantum Science3(1), (2021).[2] E. Corte et al, Magnesium-Vacancy Optical Centers in Diamond, ACS Photonics, 10(1), p101-110, (2023)[3] Pierini et al. Highly Photostable Perovskite Nanocubes : TowardIntegrated Single Photon Sources Based on Tapered Nanofibers.ACS Photonics, 7(8), p.2265-2272, (2020).[4] Fujiwara et al., Highly efficient coupling of photons from na-noemitters into single-mode optical fibers, Nano Letters, 11(10),4362–4365, (2011).[5] A.Balena et al, Deterministic Bottom-Up Fabrication of Plasmonic Nanostructures on OpticalNanofibers via Blurred Electron Beam Deposition (soon to be published in Advance Material).
Abstract Photonic quantum technology is essentially based on the exchange of individual photons as information carriers. Therefore, the development of practical single-photon sources that emit single photons on-demand is a crucial contribution to advance this emerging technology and to promote its first real-world applications. In the last two decades, a large number of quantum light sources based on solid-state emitters have been developed on a laboratory scale. Corresponding structures today have almost ideal optical and quantum-optical properties. For practical applications, however, one crucial factor is usually missing, namely direct on-chip fiber coupling, which is essential, for example, for the direct integration of such quantum devices into fiber-based quantum networks. In fact, the development of fiber-coupled quantum light sources is still in its infancy, with very promising advances having been made in recent years. Against this background, this review article presents the current status of the development of fiber-coupled quantum light sources based on solid-state quantum emitters and discusses challenges, technological solutions and future prospects. Among other things, the numerical optimization of the fiber coupling efficiency, coupling methods, and important realizations of such quantum devices are presented and compared. Overall, this article provides an important overview of the state-of-the-art and the performance parameters of fiber-coupled quantum light sources that have been achieved so far. It is aimed equally at experts in the scientific field and at students and newcomers who want to get an overview of the current developments.