Study for the development of a cavity enhanced single photon source

The nitrogen-vacancy defect in diamond (NV centre) is a leading candidate for solid-state implementations of quantum information technologies. Among other useful properties, it is a bright source of single photons. It is difficult, though, to collect the emitted photons in a single spatial and spectral mode which is often needed for quantum information applications. One way to improve the single-mode collection efficiency is to embed an NV centre in a high-finesse cavity. The coupling of the NV centre dipole to the cavity mode gives rise to the Purcell enhancement -- an increase of the emission into the cavity's spectral and spatial mode. The goal of this project will be to develop a fibre-based microcavity and to use it for the observation of enhanced single-photon emission from a diamond nanocrystal. It will involve a wide range of experimental techniques, for example basic optics (particularly Gaussian beam propagation), CO2 laser ablation, surface analysis by optical and atomic force microscopes, interferometry, photon counting, etc. There will also be a certain amount of data analysis, simulations and theoretical calculations.ope

Integrating cold caesium atoms into optical waveguides

This project focuses on a novel experimental method for interfacing cold atoms with optical waveguides. This relies on the introduction of cold atoms into microscopic laser-drilled holes that are perpendicular to the propagation axis of the waveguide. Direct interfacing of cold atoms with the guided mode of a waveguide is an attractive mechanism by which to create atom-photon interfaces, as the small mode area increases the interaction rate. Unlike many previous approaches, this technique can be applied in almost any existing waveguide system, including chip-based waveguide arrays and other complex environments. It therefore has great promise as a way of creating hybrid atom-photon quantum devices. Using this method, we demonstrate coupling between cold atoms and the light propagating in the core of an untapered single-mode optical fibre. This was achieved by laser-drilling a cylindrical, transverse hole (30 μm diameter) through the core of the fibre. Ensembles of cold caesium atoms can be tightly confined through an optical dipole trap within the microscopic void. Probe light, resonant with the Cs D2 line, is then coupled into the fibre. By measuring the transmitted optical power through the interface, it was determined that up to 87% of the probe power could be absorbed by the atoms. The corresponding optical depth per unit length of the atom cloud is over 700 cm^(-1), higher than any value reported to date for a comparable system. This will be a key parameter for the miniaturisation of atom-optical systems as well as for enhancing spatial resolution in sensing applications. The dependence of this absorption on several experimental parameters was also characterised and found to be in line with theoretical expectations. The atomic transition is not noticeably broadened by the presence of the fibre. We have also carried out numerical simulations of light transmission across wave-guide junctions of this type, proving that tailored hole geometries can enable enhanced optical transmission. The achievable degree of improvement is such that it is conceivable to place the void within an optical resonator, for example using laser-written Bragg gratings, and to achieve the strong coupling between the atoms and the guided light. Altogether this work demonstrates the potential of this technique to interface atoms with tightly confined light, allowing for integration in otherwise purely photonic circuits. In such environment the interaction between the atomic ensemble and the light can act as a node for the storage and processing of quantum information

Candidate biomarkers from the integration of methylation and gene expression in discordant autistic sibling pairs

While the genetics of autism spectrum disorders (ASD) has been intensively studied, resulting in the identification of over 100 putative risk genes, the epigenetics of ASD has received less attention, and results have been inconsistent across studies. We aimed to investigate the contribution of DNA methylation (DNAm) to the risk of ASD and identify candidate biomarkers arising from the interaction of epigenetic mechanisms with genotype, gene expression, and cellular proportions. We performed DNAm differential analysis using whole blood samples from 75 discordant sibling pairs of the Italian Autism Network collection and estimated their cellular composition. We studied the correlation between DNAm and gene expression accounting for the potential effects of different genotypes on DNAm. We showed that the proportion of NK cells was significantly reduced in ASD siblings suggesting an imbalance in their immune system. We identified differentially methylated regions (DMRs) involved in neurogenesis and synaptic organization. Among candidate loci for ASD, we detected a DMR mapping to CLEC11A (neighboring SHANK1) where DNAm and gene expression were significantly and negatively correlated, independently from genotype effects. As reported in previous studies, we confirmed the involvement of immune functions in the pathophysiology of ASD. Notwithstanding the complexity of the disorder, suitable biomarkers such as CLEC11A and its neighbor SHANK1 can be discovered using integrative analyses even with peripheral tissues

A Case for Quantum Memories in Space

It has recently been theoretically shown that Quantum Memories (QM) could enable truly global quantum networking when deployed in space [1, 2] thereby surpassing the limited range of land-based quantum repeaters. Furthermore, QM in space could enable novel protocols and long-range entanglement and teleportation applications suitable for Deep-Space links and extended scenarios for fundamental physics tests. In this white paper we will make the case for the importance of deploying QMs to space, and also discuss the major technical milestones and development stages that will need to be considere

Terrestrial Very-Long-Baseline Atom Interferometry:Workshop Summary

This document presents a summary of the 2023 Terrestrial Very-Long-Baseline Atom Interferometry Workshop hosted by CERN. The workshop brought together experts from around the world to discuss the exciting developments in large-scale atom interferometer (AI) prototypes and their potential for detecting ultralight dark matter and gravitational waves. The primary objective of the workshop was to lay the groundwork for an international TVLBAI proto-collaboration. This collaboration aims to unite researchers from different institutions to strategize and secure funding for terrestrial large-scale AI projects. The ultimate goal is to create a roadmap detailing the design and technology choices for one or more km-scale detectors, which will be operational in the mid-2030s. The key sections of this report present the physics case and technical challenges, together with a comprehensive overview of the discussions at the workshop together with the main conclusions

VizieR Online Data Catalog: Mrk 421 multi-wavelength variability, 2007-2009 (Ahnen+, 2016)

Data of Mrk 421 are presented for the following instruments and bands from radio to very high energy gamma-rays: Metsahovi (37GHz), OVRO (15GHz), GASP (R band), RXTE/ASM (2-10keV), Swift/BAT(15-50keV), MAGIC (>400 GeV). The observation period is from 10th February 2007 (MJD 54141) to 23rd July 2009 (MJD 55035). Figure 2 includes the light curves of the above mentioned instruments. Figure 3 and 4 show the fractional variability F_var for these light curves of the above mentioned light curves for the whole time span (Fig. 3) and for the separate time spans P1, P2, P3 (Fig. 4). (3 data files). <P /