Multiplexed Single Photons from Deterministically Positioned Nanowire Quantum Dots

Solid-state quantum emitters are excellent sources of on-demand indistinguishable or entangled photons and can host long-lived spin memories, crucial resources for photonic quantum information applications. However, their scalability remains an outstanding challenge. Here we present a scalable technique to multiplex streams of photons from multiple independent quantum dots, on-chip, into a fiber network for use off-chip. Multiplexing is achieved by incorporating a multi-core fiber into a confocal microscope and spatially matching the multiple foci, seven in this case, to quantum dots in an array of deterministically positioned nanowires. First, we report the coherent control of the emission of biexciton-exciton cascade from a single nanowire quantum dot under resonant two-photon excitation. Then, as a proof-of-principle demonstration, we perform parallel spectroscopy on the nanowire array to identify two nearly identical quantum dots at different positions which are subsequently tuned into resonance with an external magnetic field. Multiplexing of background-free single photons from these two quantum dots is then achieved. Our approach, applicable to all types of quantum emitters, can readily be scaled up to multiplex $>100$ quantum light sources, providing a breakthrough in hardware for photonic based quantum technologies. Immediate applications include quantum communication, quantum simulation, and quantum computation.Comment: 10 pages, 4 figure

The Impact of Culturing the Organ Preservation Fluid on Solid Organ Transplantation: A Prospective Multicenter Cohort Study

Background. We analyzed the prevalence, etiology, and risk factors of culture-positive preservation fluid and their impact on the management of solid organ transplant recipients. Methods. From July 2015 to March 2017, 622 episodes of adult solid organ transplants at 7 university hospitals in Spain were prospectively included in the study. Results. The prevalence of culture-positive preservation fluid was 62.5% (389/622). Nevertheless, in only 25.2% (98/389) of the cases were the isolates considered ?high risk? for pathogenicity. After applying a multivariate regression analysis, advanced donor age was the main associated factor for having culture-positive preservation fluid for high-risk microorganisms. Preemptive antibiotic therapy was given to 19.8% (77/389) of the cases. The incidence rate of preservation fluid?related infection was 1.3% (5 recipients); none of these patients had received preemptive therapy. Solid organ transplant (SOT) recipients with high-risk culture-positive preservation fluid receiving preemptive antibiotic therapy presented both a lower cumulative incidence of infection and a lower rate of acute rejection and graft loss compared with those who did not have high-risk culture-positive preservation fluid. After adjusting for age, sex, type of transplant, and prior graft rejection, preemptive antibiotic therapy remained a significant protective factor for 90-day infection. Conclusions. The routine culture of preservation fluid may be considered a tool that provides information about the contamination of the transplanted organ. Preemptive therapy for SOT recipients with high-risk culture-positive preservation fluid may be useful to avoid preservation fluid?related infections and improve the outcomes of infection, graft loss, and graft rejection in transplant patients

Towards scalable and efficient single photon sources

This thesis investigates the development of techniques to enable the creation of brighter and easier to scale single photon emitters. This is possible with the use of a novel nanoantenna design paired with a redesigned confocal microscope capable of addressing multiple sources in parallel. The nanoantenna design is based on a hemishperical cavity which is typically used in the design of lasers. These are the source of their very high directivity. The design is adapted to allow its integration with solid state sources such as quantum dots and defect centres in diamond. By modifying the properties of the mirror enclosing the cavity it is possible to precisely control the quality factor and the Purcell enhancement of the emission. Additionally, due to its monolithic nature the design is highly stable and permits the incorporation of additional contacting layers to tune the emitters. The new microscope design makes use of multicore fibres on its excitation and collection arms in order to have multiple independent focii on the sample. The design is demonstrated on a nanowire sample were two single photon streams from two separate nanowires are collected simultaneously. The new design also makes use of a quasi-4F lens configuration to minimize beam displacement and optical aberrations. Finally, a new open source tool is developed to facilitate the analysis of time correlated single photon experiments. All the algorithms are optimized to make adequate use of modern computer’s memory hierarchy and multicore nature