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Brain tissue is ubiquitous in the archaeological record. Multiple, independent studies report the finding of black, resinous or shiny brain tissue, and Petrone et al. [2020 “Heat-induced Brain Vitrification from the Vesuvius Eruption in C.E. 79.” N Engl J Med. 382: 383–384; doi:10.1056/NEJMc1909867] raise the intriguing prospect of a role for vitrification in the preservation of ancient biomolecules. However, Petrone et al. (2020) have not made their raw data available, and no detailed laboratory or analytical methodology is offered. Issues of contamination and misinterpretation hampered a decade of research in biomolecular archaeology, such that addressing these sources of bias and facilitating validation of specious findings has become both routine and of paramount importance in the discipline. We argue that the evidence they present does not support their conclusion of heat-induced vitrification of human brain tissue, and that future studies should share palaeoproteomic data in an open access repository to facilitate comparative analysis of the recovery of ancient proteins and patterns of their degradation.

Growing interest in quantum computing for practical applications has led to a surge in the availability of programmable machines for executing quantum algorithms1,2. Present-day photonic quantum computers3–7 have been limited either to non-deterministic operation, low photon numbers and rates, or fixed random gate sequences. Here we introduce a full-stack hardware−software system for executing many-photon quantum circuit operations using integrated nanophotonics: a programmable chip, operating at room temperature and interfaced with a fully automated control system. The system enables remote users to execute quantum algorithms that require up to eight modes of strongly squeezed vacuum initialized as two-mode squeezed states in single temporal modes, a fully general and programmable four-mode interferometer, and photon number-resolving readout on all outputs. Detection of multi-photon events with photon numbers and rates exceeding any previous programmable quantum optical demonstration is made possible by strong squeezing and high sampling rates. We verify the non-classicality of the device output, and use the platform to carry out proof-of-principle demonstrations of three quantum algorithms: Gaussian boson sampling, molecular vibronic spectra and graph similarity8. These demonstrations validate the platform as a launchpad for scaling photonic technologies for quantum information processing. A system for realizing many-photon quantum circuits is presented, comprising a programmable nanophotonic chip operating at room temperature, interfaced with a fully automated control system.

Entangled multiphoton states lie at the heart of quantum information, computing, and communications. In recent years, topology has risen as a new avenue to robustly transport quantum states in the presence of fabrication defects, disorder and other noise sources. Whereas topological protection of single photons and correlated photons has been recently demonstrated experimentally, the observation of topologically protected entangled states has thus far remained elusive. Here, we experimentally demonstrate the topological protection of spatially-entangled biphoton states. We observe robustness in crucial features of the topological biphoton correlation map in the presence of deliberately introduced disorder in the silicon nanophotonic structure, in contrast with the lack of robustness in nontopological structures. The topological protection is shown to ensure the coherent propagation of the entangled topological modes, which may lead to robust propagation of quantum information in disordered systems., Comment: 17 pages, 5 figures

We report demonstrations of both quadrature squeezed vacuum and photon number difference squeezing generated in an integrated nanophotonic device. Squeezed light is generated via strongly driven spontaneous four-wave mixing below threshold in silicon nitride microring resonators. The generated light is characterized with both homodyne detection and direct measurements of photon statistics using photon number-resolving transition edge sensors. We measure $1.0(1)$~dB of broadband quadrature squeezing (${\sim}4$~dB inferred on-chip) and $1.5(3)$~dB of photon number difference squeezing (${\sim}7$~dB inferred on-chip). Nearly-single temporal mode operation is achieved, with measured raw unheralded second-order correlations $g^{(2)}$ as high as $1.95(1)$. Multi-photon events of over 10 photons are directly detected with rates exceeding any previous quantum optical demonstration using integrated nanophotonics. These results will have an enabling impact on scaling continuous variable quantum technology., Comment: Minor revisions, and Fig. 5 corrected; Now published in Science Advances

We report our experimental results on topologically protected path-entangled photonic states using dimer chains in silicon photonics. These results highlight the potential of the lattice topology to protect photonic quantum information.

Defect modes in two-dimensional periodic photonic structures have found use in diverse optical devices. For example, photonic crystal cavities confine optical modes to subwavelength volumes and can be used for enhancement of nonlinearity, lasing and cavity quantum electrodynamics. Defect-core photonic crystal fibres allow for supercontinuum generation and endlessly single-mode fibres with large cores. However, these modes are notoriously fragile: small structural change leads to significant detuning of resonance frequency and mode volume. Here, we show that photonic topological crystalline insulator structures can be used to topologically protect the mode frequency at mid-gap and minimize the volume of a photonic defect mode. We experimentally demonstrate this in a femtosecond-laser-written waveguide array by observing the presence of a topological zero mode confined to the corner of the array. The robustness of this mode is guaranteed by a topological invariant that protects zero-dimensional states embedded in a two-dimensional environment—a novel form of topological protection that has not been previously demonstrated. Eigenmodes of photonic crystal defects have now been topologically protected in an experimental demonstration that also shows how to minimize the mode volume.

There has long been debate over the origins of dairy consumption within European populations. Whilst it was previously assumed that lactase persistence (LP) was under positive selection following the advent of agriculture, recent genetic studies of prehistoric human remains have revealed LP may have only emerged in Europe in the last 4000 years. These findings stand in contrast to organic residue analysis of Neolithic pottery indicating the utilisation of dairy products, and zooarchaeological mortality profiles consistent with dairying herds at Neolithic sites. The recent discovery of the milk protein β-lactoglobulin (BLG) within human dental calculus presents a new method via which to explore dairy product consumption in the archaeological past. Here, we apply shotgun proteomic analysis to dental calculus samples from three British Neolithic sites, revealing the earliest identification of BLG in human dental calculus to date. The presence of BLG peptides in individuals who are unlikely to possess LP provides new insight into dairying in the British Neolithic, suggesting the potential processing of milk by Neolithic populations to reduce the lactose content of dairy products.

We review our experimental demonstration of topological protection of the spatial entanglement of photonic quantum states in a nanophotonic array of coupled silicon nanowires. Our results provide new avenues towards robust quantum circuits.

Motivation Classification of archaeological animal samples is commonly achieved via manual examination of matrix-assisted laser desorption/ionization time-of-flight (MALDI-ToF) spectra. This is a time-consuming process which requires significant training and which does not produce a measure of confidence in the classification. We present a new, automated method for arriving at a classification of a MALDI-ToF sample, provided the collagen sequences for each candidate species are available. The approach derives a set of peptide masses from the sequence data for comparison with the sample data, which is carried out by cross-correlation. A novel way of combining evidence from multiple marker peptides is used to interpret the raw alignments and arrive at a classification with an associated confidence measure. Results To illustrate the efficacy of the approach, we tested the new method with a previously published classification of parchment folia from a copy of the Gospel of Luke, produced around 1120 C.E. by scribes at St Augustine’s Abbey in Canterbury, UK. In total, 80 of the 81 samples were given identical classifications by both methods. In addition, the new method gives a quantifiable level of confidence in each classification. Availability and implementation The software can be found at https://github.com/bioarch-sjh/bacollite, and can be installed in R using devtools. Supplementary information Supplementary data are available at Bioinformatics online.

Cattle were domesticated ∼10,000 years ago, but analysis of modern breeds has not elucidated their origins. Verdugo et al. performed genome-wide analysis of 67 ancient Near Eastern Bos taurus DNA samples. Several populations of ancient aurochs were progenitors of domestic cows. These genetic lineages mixed ∼4000 years ago in a region around the Indus Valley. Interestingly, mitochondrial analysis indicated that genetic material likely derived from arid-adapted Bos indicus (zebu) bulls was introduced by introgression.Science, this issue p. 173Genome-wide analysis of 67 ancient Near Eastern cattle, Bos taurus, remains reveals regional variation that has since been obscured by admixture in modern populations. Comparisons of genomes of early domestic cattle to their aurochs progenitors identify diverse origins with separate introgressions of wild stock. A later region-wide Bronze Age shift indicates rapid and widespread introgression of zebu, Bos indicus, from the Indus Valley. This process was likely stimulated at the onset of the current geological age, ~4.2 thousand years ago, by a widespread multicentury drought. In contrast to genome-wide admixture, mitochondrial DNA stasis supports that this introgression was male-driven, suggesting that selection of arid-adapted zebu bulls enhanced herd survival. This human-mediated migration of zebu-derived genetics has continued through millennia, altering tropical herding on each continent.

Reliable sources of photons will be required to develop many photonic quantum technologies. Current on-demand sources are lacking in brightness, compactness, and scalability. Here, we review the use of silicon photonic crystal waveguides as nonlinear photon generators in the 1550 nm band. We show that these photon sources can create strong frequency correlations, that the predictability of photon generation can be improved through the active multiplexing of many sources, and that photons from these sources can be useful for quantum communication.

We present an automated and stable method to measure an arbitrary portion of the joint spectral intensity of quantum photonic devices with an unprecedented resolution of 10 GHz in the telecommunication band. The method is applied to a 20 cm chalcogenide As2S3 fiber that generates correlated photons via spontaneous four-wave mixing. Good qualitative agreement between our measurements and an idealized theoretical model is obtained. The entanglement present in the system is extracted via a Schmidt decomposition where the reduction in the Schmidt number compared to that calculated via the model is attributed to the high amount of spontaneous Raman scattered noise photons present in chalcogenide fiber.

A key resource for quantum optics experiments is an on-demand source of single and multiple photon states at telecommunication wavelengths. This letter presents a heralded single photon source based on a hybrid technology approach, combining high efficiency periodically poled lithium niobate waveguides, low-loss laser inscribed circuits, and fast (>1 MHz) fibre coupled electro-optic switches. Hybrid interfacing different platforms is a promising route to exploiting the advantages of existing technology and has permitted the demonstration of the multiplexing of four identical sources of single photons to one output. Since this is an integrated technology, it provides scalability and can immediately leverage any improvements in transmission, detection and photon production efficiencies.

Analysis of ancient cattle husbandry is compromised by the need for conventional analysis of sex and age at death to use different elements of the skeleton, usually from different individuals. We demonstrate a technique using aDNA acquired from cattle mandibles and combined with age-at-death estimation based on dental eruption in the same specimens. Application to small sample groups from two sites in Na h-Eileanan Siar (the Scottish Western Isles) show a high success rate, and demonstrates the potential for a more nuanced interpretation of ancient cattle husbandry.

We employ “photonic boron nitride” — a silicon photonic crystal slab composed of a honeycomb lattice of holes — to observe Dirac physics of guided optical modes. The lattice is composed of two component triangular lattices of different hole-size Δr, which breaks the Dirac cone and opens up an observable band gap.

We experimentally demonstrate topologically protected optical waveguiding in silicon at the interface between two topologically distinct dimer chains. Further, we propose and demonstrate beating between topological and trivial defect modes.

It is a fundamental challenge in quantum optics to deterministically generate indistinguishable single photons through non-deterministic nonlinear optical processes, due to the intrinsic coupling of single- and multi-photon-generation probabilities in these processes. Actively multiplexing photons generated in many temporal modes can decouple these probabilities, but key issues are to minimize resource requirements to allow scalability, and to ensure indistinguishability of the generated photons. Here we demonstrate the multiplexing of photons from four temporal modes solely using fibre-integrated optics and off-the-shelf electronic components. We show a 100% enhancement to the single-photon output probability without introducing additional multi-photon noise. Photon indistinguishability is confirmed by a fourfold Hong–Ou–Mandel quantum interference with a 91±16% visibility after subtracting multi-photon noise due to high pump power. Our demonstration paves the way for scalable multiplexing of many non-deterministic photon sources to a single near-deterministic source, which will be of benefit to future quantum photonic technologies., Deterministically generated single photons are useful for quantum communications, but the processes that create such light are often non-deterministic. Here, the authors enhance the single-photon output probability by multiplexing photons from four temporal modes using fibre-integrated optics.

We show topological waveguiding of single and correlated photons generated in a spatially modulated array of silicon nanowires. These are the first experiments with correlated quantum states in any topological photonic system.

We experimentally demonstrate topologically protected optical waveguiding in silicon at the interface between two topologically distinct dimer chains. Further, we propose and demonstrate beating between topological and trivial defect modes.

We employ planar silicon photonic crystal “photonic boron nitride” to observe Dirac physics in guided optical modes, by breaking the inversion symmetry of a honeycomb lattice of air holes to open an observable optical bandgap.

Image analysis techniques have been used to investigate the likelihood of being able to classify and assign a probability regarding the plant origin of individual starch granules in a collection of granules. Quantifiable variables were used to characterize the granules, and the assignments and probabilities were calculated objectively. We consider the classification of images containing granules of a single species and of mixed species and the possibility of assigning a class to granules of unknown species in an image of a slide obtained from the dental calculus of chimpanzees.

The integration of microfluidics and microphotonics brings the ability to tune and reconfigure ultra-compact optical devices. This flexibility is essentially provided by three characteristics of fluids that are scalable at the micron-scale: fluid mobility, large ranges of index modulation, and abrupt interfaces that can be easily reshaped. Several examples of optofluidic devices are presented here to illustrate the achievement of flexible devices on (semi) planar and compact platforms. First, we report an integrated geometry for a compact and tunable interferometer that exploits a sharp and mobile air/water interface. We then describe a class of optically controlled devices that rely on the actuation of optically trapped micron-sized objects within a fluid environment. The last architecture results from the infiltration of photonic crystal devices with fluids. This produces tunable and reconfigurable photonic devices, like optical switches. Higher degrees of functionality could be achieved with sophisticated optofluidic platforms that associate complex microfluidic delivery and mixing schemes with microphotonic devices. Moreover, optofluidics offers new opportunities for realizing highly responsive and compact sensors.

We investigate the generation of random numbers via the quantum process of spontaneous Raman scattering. Spontaneous Raman photons are produced by illuminating a highly nonlinear chalcogenide glass ( As2S3) fiber with a CW laser at a power well below the stimulated Raman threshold. Single Raman photons are collected and separated into two discrete wavelength detuning bins of equal scattering probability. The sequence of photon detection clicks is converted into a random bit stream. Postprocessing is applied to remove detector bias, resulting in a final bit rate of ∼650 kb/s. The collected random bit-sequences pass the NIST statistical test suite for one hundred 1 Mb samples, with the significance level set to α=0.01. The fiber is stable, robust and the high nonlinearity (compared to silica) allows for a short fiber length and low pump power favourable for real world application.

We use classical stimulated four-wave mixing to directly characterize quantum spectral correlations generated in a silicon nanowire for two different pump durations. Signal to noise is increased and acquisition time reduced compared to coincidence detection.

By harnessing quantum mechanical effects we can create technology with greatly improved functionality including enhanced sensing, exponentially faster computing, the simulation of previously inaccessible quantum systems, and the secure transfer of information. In our ever more connected world, it is important that we can communicate securely, and as technology develops into the quantum regime it will become important for distant quantum processors to exchange information over a quantum network. Here we discuss how quantum information can be encoded and transferred around a such a network. We concentrate on the use of nonlinear optics to generate and manipulate photons, and present schemes for fully secure quantum communication.

Background: As high utilizers of health care resources, frequent attenders to medical practices pose a significant issue for primary health care. Studies documenting content of visits and characteristics of frequent attenders have paid limited attention to community health center populations. This study profiles these high utilizers comparing them to non-frequent attenders. Methods: Through medical record abstraction, retrospective and longitudinal patient data were obtained for a 30-month time period for 382 established patients. Results: Older patients 45 to 64 years (OR = 1.85; 95% CI: 0.92, 3.70) and Medicaid recipients (OR = 3.22; 95% CI: 1.54, 6.72) were more likely to be frequent attenders. Patients residing furthest away from the CHC were also the most frequent of attenders (OR = 3.68; 95% CI: 1.22, 11.13), as were those with a diagnosis of diabetes (OR = 5.03; 95% CI: 2.17, 11.70) or depression (OR = 1.85; 95% CI: 0.96, 3.56). Patients who used the Emergency Department more (OR = 1.54; 95% CI: 1.23,1.91) had the highest number of visits, although those patients who missed more appointments as a proportion of the number of scheduled appointments were less likely to be frequent attenders (OR = 0.49; 95% CI: 0.36, 0.66). Conclusions: Through developing interventions such as customized social report cards and applying elements of the Chronic Care Model, these results can help administrators and policy makers ensure that frequent attenders are cared for adequately and that safety net providers’ resources are appropriate to the tasks demanded of them.

In order to assess the distribution of African Palaeolithic sites and hominin remains, we need an understanding of the factors that may affect the preservation of archaeological material in the fossil record. One of the main factors that is thought to affect seriously the global distribution of fossil remains is taphonomy, but it would seem that taphonomic processes may themselves be overprinted by collagen degradation. The rate of collagen loss is highly temperature dependent, and it has been shown that bone is more likely to be preserved in areas of lower temperature and so lower collagen loss. Hence, it would be expected that fossil fauna remains would be distributed in areas of low collagen loss, i.e. low temperature. Conversely, lithics will not be subject to a temperature bias in their preservation. We have tested this hypothesis through the use of archaeological material. Our results show that the distributions of both lithic and faunal assemblages are non-random across the African continent, with all archaeological sites being found in areas of relatively low collagen degradation. This implies that bone collagen degradation is not the only factor affecting the distribution of African Palaeolithic sites and hominin remains. We suggest that the site distribution is not a reflection of bias in excavation history, but is a real phenomenon reflecting hominin habitat choice.

Gelatine is a component of a wide range of foods. It is manufactured as a by-product of the meat industry from bone and hide, mainly from bovine and porcine sources. Accurate food labelling enables consumers to make informed decisions about the food they buy. Since labelling currently relies heavily on due diligence involving a paper trail, there could be benefits in developing a reliable test method for the consumer industries in terms of the species origin of gelatine. We present a method to determine the species origin of gelatines by peptide mass spectrometry methods. An evaluative comparison is also made with ELISA and PCR technologies. Commercial gelatines were found to contain undeclared species. Furthermore, undeclared bovine peptides were observed in commercial injection matrices. This analytical method could therefore support the food industry in terms of determining the species authenticity of gelatine in foods.

Reliable sources of photons are imperative to the development of photonic quantum technologies. I will review the use of ultra-compact slow light photonic crystal structures to create heralded single photon sources using nonlinear processes.

In recent years integrated waveguide devices have emerged as an attractive platform for scalable quantum tech- nologies. In contrast to earlier free-space investigations, one must consider additional effects induced by the media. In amorphous materials, spontaneous Raman scattered photons act as a noise source. In crystalline materials two-photon absorption (TPA) and free carrier absorption (FCA) are present at large intensities. While initial observations noted TPA affected experiments in integrated semiconductor devices, at present the nuanced roles of these processes in the quantum regime is unclear. Here, using single photons generated via spontaneous four-wave mixing (SFWM) in silicon, we experimentally demonstrate that cross-TPA (XTPA) between a classical pump beam and generated single photons imposes an intrinsic limit on heralded single photon generation, even in the single pair regime. Our newly developed model is in excellent agreement with experimental results.

We discuss the hybrid integration of multiple components for the production of telecom band single photon sources. We implement four, on-chip, waveguide channels capable of producing four spatially separated collinear pairs of single photons. Using laser inscribed waveguide circuits and point-by-point bre Bragg gratings (FBG), we interface, separate and lter generated photon pairs. We propose using fast switches to actively route multiple heralded single photons to a single output producing an enhanced rate while maintaining a xed noise level.

We demonstrate spatial multiplexing of two heralded single photon sources created by bi-directionally pumping a single 96 μm photonic crystal waveguide. This enhances the source brightness by 51.2±4.0% whilst maintaining the coincidence to accidental ratio.

We generate a quantum random bit-string at 650kb/s by frequency binning spontaneous Raman scattered photons from a highly-nonlinear As2S3 glass detected using superconducting single photon detectors. The bit-sequences pass all the NIST statistical randomness tests.

International audience; This paper presents the first study that combines the use of ancient crop and animal stable isotopes (carbon and nitrogen) and Zooarchaeology Mass Spectrometry species identication (ZooMS) for reconstructing early farming practices at Kouphovouno, a MiddleeLate Neolithic village in southern Greece (c. 5950e4500 cal. BC). Debate surrounding the nature of early farming predominantly revolves around the intensity of crop cultivation: did early farmers move around the landscape while practicing temporary farming methods such as slash and burn agriculture or did they create more permanent elds by investing high labor inputs into smaller pieces of land that produced higher crop yields? The need to address these questions using a direct assessment of the intensity and scale of cultivation is apparent, and an integrated stable isotope approach provides such an opportunity. The results of this study support the model of small-scale mixed farming, where crop cultivation and animal husbandry are closely integrated. The farmers directed their intensive management towards crops grown for human consumption (free-threshing wheat), while growing fodder crop (hulled barley) more extensively. Pulses were cultivated under a high-manuring/high-watering regime, likely in garden plots in rotation with free-threshing wheat. The diets of the livestock enable us to investigate which parts of the landscape were used for browsing and grazing and indicate that animal management changed in the Late Neolithic. The sheep and goats were now kept in smaller numbers and grazed together and new pasture grasses may have been sought for the grazing of cattle. This study demonstrates that beyond its applicability for palaeodietary reconstruction, analysis of stable isotopes of archaeological crop and animal remains has important implications for understanding the relationship between humans, plants and animals in an archaeological context.

Single photons are of paramount importance to future quantum technologies, including quantum communication and computation. Nonlinear photonic devices using parametric processes offer a straightforward route to generating photons, however additional nonlinear processes may come into play and interfere with these sources. Here we analyse these sources in the presence of multi-photon processes for the first time. We conduct experiments in silicon and gallium indium phosphide photonic crystal waveguides which display inherently different nonlinear absorption processes, namely two-photon (TPA) and three-photon absorption (ThPA), respectively. We develop a novel model capturing these diverse effects which is in excellent quantitative agreement with measurements of brightness, coincidence-to-accidental ratio (CAR) and second-order correlation function g(2)(0), showing that TPA imposes an intrinsic limit on heralded single photon sources. We devise a new figure of merit, the quantum utility (QMU), enabling direct comparison and optimisation of single photon sources., 6 figures, 12 pages

Age estimation in cadavers, human remains and living individuals may clarify issues with significant legal and social ramifications for individuals as well as for the community. In such cases methods for estimating age should fulfil the following specific demands: (1) they must have been presented to the scientific community, as a rule by publication in peer-reviewed journals, (2) clear information concerning accuracy of age estimation by the method should be available, (3) the methods need to be sufficiently accurate and (4) in cases of age estimation in living individuals principles of medical ethics and legal regulations have to be considered. We have identified and summarized the methods that essentially fulfil these specific demands. In childhood and adolescence morphological methods based on the radiological examination of dental and skeletal development are to be recommended. In adulthood, the accuracy of most morphological methods is much reduced. Here a biochemical method based on aspartic acid racemization in dentine provides the most accurate estimates of age, followed by special morphological dental and skeletal methods. The choice of method has to take account of the individual circumstances of each case. Most methods require either the consultation of specialised and trained scientists or an adequate calibration by the "user". Very few attempts have been made to find common standardisation, calibration and evaluation procedures or to develop means of quality assurance for methods of age estimation. Efforts in these directions are necessary to guarantee quality standards and adequate answers to the important legal and social issue of age estimation in forensic medicine.

Accurate age determination of adult cadavers and human remains is a key requirement in forensic practice. The current morphological methods lack accuracy and precision, require specialist training and are costly. The use of aspartic acid racemization (AAR) in human dentine provides a simple, cost-effective solution and the method can achieve accuracies of +/- 3 years at best. Currently, there are differences in AAR methodology between laboratories which produce different results on the rate of racemization in teeth. These inconsistencies must be resolved if the technique is to be successfully applied to age determinations in forensic cases. This paper reviews the differences in protocol which have been used, discusses how each method will affect the results obtained from AAR analysis and gives recommendations for optimization of the methological protocol as a first step towards international standardization.

We acknowledge the financial support of the European Commission through the Marie Curie program (FP7, ALLOPTICS), as well as the Faculty of Science at the University of Sydney and the Australian Research Council (ARC) through the Centre of Excellence (CUDOS), Discovery project (DP110100003) and DECRA programs (DE120100226, DE120101329, DE130101148). J.L. was supported by the grant of NKBRSF (G2010CB923200), NNSFC (11204386) and GNSF (S2012040007812). The ability to use coherent light for material science and applications is linked to our ability to measure short optical pulses. While free-space optical methods are well established, achieving this on a chip would offer the greatest benefit in footprint, performance and cost, and allow the integration with complementary signal-processing devices. A key goal is to achieve operation at sub-watt peak power levels and on sub-picosecond timescales. Previous integrated demonstrations require either a temporally synchronized reference pulse, an off-chip spectrometer or long tunable delay lines. Here we report a device capable of achieving single-shot time-domain measurements of near-infrared picosecond pulses based on an ultra-compact integrated CMOS-compatible device, which could operate without any external instrumentation. It relies on optical third-harmonic generation in a slow-light silicon waveguide. Our method can also serve as an in situ diagnostic tool to map, at visible wavelengths, the propagation dynamics of near-infrared pulses in photonic crystals. Postprint

We present the first near-unit efficiency demonstration of single photon frequency conversion through Bragg scattering four-wave mixing in a dispersion engineered highly nonlinear fiber.

The non-deterministic nature of photon sources is a key limitation for single-photon quantum processors. Spatial multiplexing overcomes this by enhancing the heralded single-photon yield without enhancing the output noise. Here the intrinsic statistical limit of an individual source is surpassed by spatially multiplexing two monolithic silicon-based correlated photon pair sources in the telecommunications band, demonstrating a 62.4% increase in the heralded single-photon output without an increase in unwanted multipair generation. We further demonstrate the scalability of this scheme by multiplexing photons generated in two waveguides pumped via an integrated coupler with a 63.1% increase in the heralded photon rate. This demonstration paves the way for a scalable architecture for multiplexing many photon sources in a compact integrated platform and achieving efficient two-photon interference, required at the core of optical quantum computing and quantum communication protocols., Photonic quantum technologies will require efficient single-photon sources and spatial multiplexing has been explored as a route to achieve this. Here, the authors present a scheme to integrate several single-photon sources using spatial multiplexing for on-chip applications at telecommunications wavelengths.

Summary form only given. Raman scattering can be exploited for amplification in optical fiber telecommunications or, chemical identification in spectroscopy, but represents a source of detrimental noise photons for quantum communications. The spectral distribution of spontaneous Raman scattering (SpRS) can be measured in bulk samples with the free-space 90° scattering method [1]. In long fibers the SpRS spectra can be measured using a pulsed laser to achieve measurable signals [2], incompatible with the damage threshold of many on-chip devices. Measurements of stimulated Raman scattering have been performed using nonlinear pump-probe techniques [3], requiring the addition of either a highly tunable or ultra-broad bandwidth probe. Recently photon-counting techniques have been demonstrated to measure weak SpRS signals in fibers [4-6], however no direct measurements of the SpRS spectra of nanophotonic chip-devices over a broad bandwidth have been performed.In this work, we report for the first time a direct measurement of the SpRS spectra over a broad bandwidth in a photonic integrated platform using photon-counting spectroscopy. We apply it to amorphous silicon (a-Si) and crystalline silicon (c-Si) nanowire devices, where both platforms are CMOS compatible. The method, outlined in Fig. 1a), uses a CW laser to excite SpRS in the waveguide, a spatial light modulator (Finisar waveshaper) to resolve the spectral distribution, and a single photon detector to provide the sensitivity needed to measure the small signal associated with the SpRS in chip-scale waveguides. The results shown in Figure 1b) display a narrow Raman peak for c-Si at the frequency shift of ~525cm-1 with a bandwidth of

Here we present the first experimental demonstration of spatial multiplexing of two integrated heralded single photon sources so as to enhance the heralded photon rate for a given single waveguide output power.

In this Letter we demonstrate frequency conversion in the single-photon regime through Bragg-scattering four-wave mixing with near-unit efficiency in a 750 m long commercially available dispersion-engineered highly nonlinear fiber, where all photons and pump laser frequencies are in the low-loss telecommunications band. We achieve 99.1%±4.9% downconversion and 98.0%±5.0% upconversion of photons by 12 nm using a weak coherent state with an average input of 0.27 photons per detection gate window.

We demonstrate low Raman-noise correlated photon-pair generation in a dispersion-engineered 10 mm As2S3 chalcogenide waveguide at room temperature. We show a coincidence-to-accidental ratio (CAR) of 16.8, a 250 times increase compared with previously published results in a chalcogenide waveguide, with a corresponding brightness of 3×10(5) pairs·s(-1)·nm(-1) generated at the chip. Dispersion engineering of our waveguide enables photon passbands to be placed in the low spontaneous Raman scattering (SpRS) window at 7.4 THz detuning from the pump. This Letter shows the potential for As2S3 chalcogenide to be used for nonlinear quantum photonic devices.

Single photons generated in a nonlinear silicon photonic crystal waveguide are transmitted on multiple modes of the same fiber for the first time, demonstrating 35dB isolation between orthogonal modes for simultaneous quantum and classical communication.

We experimentally demonstrate a 10 times enhancement to the coincidence-to-accidental ratio of a correlated photon-pair source from a chalcogenide Ge 11.5 As 24 Se 64.5 nanowire. This improvement is enabled by the low-Raman window of the device.

We describe an automated, high resolution method to measure an arbitrary portion of the joint spectral intensity of spontaneous four-wave mixing generated photons. This allows us to quantify the spectral entanglement generated by the device.

We demonstrate a silicon chip based all-optical device capable of providing single shot time-domain measurements of picosecond pulses near λ=1550nm. The 96µm long device relies on optical third harmonic generation between two pulses in a slow light photonic crystal waveguide.

We show how slow-light enhanced four-wave mixing in dispersion engineered photonic crystal waveguides can result in ultra-compact devices enabling different applications, namely time-division demultiplexing of 160Gbaud data streams and the generation of correlated photon pairs.

We show a reduction of spontaneous Raman scattering in chalcogenide at 77 K, which improves the photon statistics of correlated pair generation only in the frequency range close to the pump (Δf < 3 THz).