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Many causes potentially underline pain in the lower extremities, presenting a real challenge for primary care clinicians in the recognition of the source of the patient’s complaints. Peripheral arterial disease (PAD) is defined as a total or partial blockage of the vessels that supply blood from the heart to the periphery. PAD of the lower extremities may masquerade as lumbosacral radiculopathy (LSR)—a common source of leg pain. Physiotherapists should be able to screen for PAD in people presenting with pain in the lower extremities. Failure to correctly screen for PAD could put the patient at risk of severe disability and possible permanent sequelae. This case report outlines the relevant concepts relating to the pathophysiology, screening, and differential diagnosis of PAD, and then further describes the relevant findings from the history and physical examination from the physiotherapist’s perspective in a patient with an unusual symptom presentation. Although the patient was referred by a physician with a diagnosis of LSR, our case highlights the pivotal role of skilled physiotherapists in triaging a severe lower-limb PAD in need of referral. Therefore, this case report aims to increase clinicians’ awareness of the clinical features of a complex case of PAD.

Many conditions could potentially cause pain in the lower limbs. One of these is peripheral arterial disease (PAD). PAD is often a real challenge to be recognized for clinicians due to symptoms that commonly mimic musculoskeletal conditions. PAD is defined as a total or partial blockage of the vessels that supply blood from the heart to the periphery. Its prevalence is around 7 percent in subjects between 55 and 59, reaching almost 25% in individuals between 95 and 99 years old. The most dominant symptom of PAD is lower limb pain. Also, PAD can produce other symptoms such as discoloration, altered skin temperature, and, when arterial blood flow is insufficient to meet the metabolic demands of resting muscle or tissue, focal areas of ischemia. In our view, physical therapists should be capable of triaging for PAD in a direct access setting. Therefore, in this Professional Issue, we present the main characteristics of PAD and the physiotherapy role in its management. A supplementary step-by-step guide will provide further resources for testing PAD.

To improve non-invasively the specificity in the diagnosis of breast cancer after a positive screening mammography or doubt/suspicious ultrasound examination, the SOLUS project developed a multimodal imaging system that combines: Bmode ultrasound (US) scans (to assess morphology), Color Doppler (to visualize vascularization), shear-wave elastography (to measure stiffness), and time domain multi-wavelength diffuse optical tomography (to estimate tissue composition in terms of oxy- and deoxy-hemoglobin, lipid, water, and collagen concentrations). The multimodal probe arranges 8 innovative photonic modules (optodes) around the US transducer, providing capability for optical tomographic reconstruction. For more accurate estimate of lesion composition, US-assessed morphological priors can be used to guide the optical reconstructions. Each optode comprises: i) 8 picosecond pulsed laser diodes with different wavelengths, covering a wide spectral range (635-1064 nm) for good probing of the different tissue constituents; ii) a large-area (variable, up to 8.6 mm2 ) fast-gated digital Silicon Photomultiplier; iii) the acquisition electronics to record the distribution of time-of-flight of the re-emitted photons. The optode is the basic element of the optical part of the system, but is also a stand-alone, ultra-compact (about 4 cm3 ) device for time domain multi-wavelength diffuse optics, with potential application in various fields.

We present an InGaAs/InP single-photon avalanche diode (SPAD) with $10 \mu \mathrm{m}$ -diameter active area, designed for fiber-based quantum applications. Improved design and fabrication lead to low dark count rate (1000 cps at 225 K), 25% photon detection efficiency and 100 ps (FWHM) timing jitter.

We present the design and the experimental characterization of a new InGaAs/InP single-photon avalanche diode (SPAD), with two different diameters: i) a 10 μm device, suitable for optical fiber-based quantum applications; ii) a 25 μm one, more appropriate for free-space applications. Compared to a previous generation, we improved the design of the double zinc diffusion and optimized the layer structure. We achieved low dark count rate, around 1 kcps and 4 kcps at 225 K and 5 V excess bias for 10 μm and 25 μm devices, respectively, and down to few tens of counts per seconds at 175 K for the 10 μm detector. At 5 V excess bias and 225 K temperature, both devices also show a high photon detection efficiency (33% at 1064 nm, 31% at 1310 nm and 25% at 1550 nm for the 10 μm SPAD). Afterpulsing has been measured with a custom readout integrated circuit, achieving very low probability values. Timing jitter is comparable to previous-generation devices.

To improve the specificity of breast cancer diagnosis SOLUS combines ultrasound, shear-wave elastography and time-domain diffuse optical tomography in a multimodal imaging system. An innovative compact device for time-domain multi-wavelength diffuse optics was also developed.

Quantum key distribution (QKD), the distribution of quantum secured keys useful for data encryption, is expected to have a crucial impact in the next decades. However, although the notable achievements accomplished in the last twenty years, many practical and serious challenges are limiting the full deployment of this novel quantum technology in the current telecommunication infrastructures. In particular, the co-propagation of quantum signals and high-speed data traffic within the same optical fiber, is not completely resolved, due to the intrinsic noise caused by the high intensity of the classical signals. As a consequence, current co-propagation schemes limit the amount of classical optical power in order to reduce the overall link noise. However, this ad-hoc solution restrains the overall range of possibilities for a large-scale QKD deployment. Here, we propose and demonstrate a new method, based on up-conversion assisted receiver, for co-propagating classical light and QKD signals. In addition, we compare the performances of this scheme with an off-the-shelf quantum receiver, equipped with a standard InGaAs detector, over different lengths of an installed fiber link. Our proposal exhibits higher tolerance for noise in comparison to the standard receiver, thus enabling the distribution of secret keys in the condition of 4 dB-higher classical power., Comment: 13 figures

The versatility of silicon photonic integrated circuits has led to a widespread usage of this platform for quantum information based applications, including Quantum Key Distribution (QKD). However, the integration of simple high repetition rate photon sources is yet to be achieved. The use of weak-coherent pulses (WCPs) could represent a viable solution. For example, Measurement Device Independent QKD (MDI-QKD) envisions the use of WCPs to distill a secret key immune to detector side channel attacks at large distances. Thus, the integration of III-V lasers on silicon waveguides is an interesting prospect for quantum photonics. Here, we report the experimental observation of Hong-Ou-Mandel interference with 46\pm 2% visibility between WCPs generated by two independent III-V on silicon waveguide integrated lasers. This quantum interference effect is at the heart of many applications, including MDI-QKD. Our work represents a substantial first step towards an implementation of MDI-QKD fully integrated in silicon, and could be beneficial for other applications such as standard QKD and novel quantum communication protocols., 5 pages, 3 figures

Global, secure quantum channels will require efficient distribution of entangled photons. Long distance, low-loss interconnects can only be realized using photons as quantum information carriers. However, a quantum light source combining both high qubit fidelity and on-demand bright emission has proven elusive. Here, we show a bright photonic nanostructure generating polarization-entangled photon pairs that strongly violates Bell's inequality. A highly symmetric InAsP quantum dot generating entangled photons is encapsulated in a tapered nanowire waveguide to ensure directional emission and efficient light extraction. We collect ~200 kHz entangled photon pairs at the first lens under 80 MHz pulsed excitation, which is a 20 times enhancement as compared to a bare quantum dot without a photonic nanostructure. The performed Bell test using the Clauser-Horne-Shimony-Holt inequality reveals a clear violation (S

Global, secure quantum channels will require efficient distribution of entangled photons. Long distance, low-loss interconnects can only be realized using photons as quantum information carriers. However, a quantum light source combining both high qubit fidelity and on-demand bright emission has proven elusive. Here, we show a bright photonic nanostructure generating polarization-entangled photon pairs that strongly violates Bell’s inequality. A highly symmetric InAsP quantum dot generating entangled photons is encapsulated in a tapered nanowire waveguide to ensure directional emission and efficient light extraction. We collect ~200 kHz entangled photon pairs at the first lens under 80 MHz pulsed excitation, which is a 20 times enhancement as compared to a bare quantum dot without a photonic nanostructure. The performed Bell test using the Clauser-Horne-Shimony-Holt inequality reveals a clear violation (SCHSH > 2) by up to 9.3 standard deviations. By using a novel quasi-resonant excitation scheme at the wurtzite InP nanowire resonance to reduce multi-photon emission, the entanglement fidelity (F = 0.817 ± 0.002) is further enhanced without temporal post-selection, allowing for the violation of Bell’s inequality in the rectilinear-circular basis by 25 standard deviations. Our results on nanowire-based quantum light sources highlight their potential application in secure data communication utilizing measurement-device-independent quantum key distribution and quantum repeater protocols.

Single photon avalanche diodes (SPADs) have been recently studied as photodetectors for applications in space missions. In this presentation we report the results of radiation hardness test on large area SPAD (actual results refer to SPADs having 500 mu m diameter). Dark counts rate as low as few kHz at -10 degrees C has been obtained for the 500 mu m devices, before irradiation. We performed bulk damage and total dose radiation tests with protons and gamma-rays in order to evaluate their radiation hardness properties and their suitability for application in a Low Earth Orbit (LEO) space mission. With this aim SPAD devices have been irradiated using up to 20 krad total dose with gamma-rays and 5 krad with protons. The test performed show that large area SPADs are very sensitive to proton doses as low as 2 x 10(8) (1 MeV eq) n/cm(2) with a significant increase in dark counts rate (DCR) as well as in the manifestation of the "random telegraph signal" effect. Annealing studies at room temperature (RT) and at 80 degrees C have been carried out, showing a high decrease of DCR after 24-48 h at RT. Lower protons doses in the range 1-10 x 10(7) (1 MeV eq) n/cm(2) result in a lower increase of DCR suggesting that the large-area SPADs tested in this study are well suitable for application in low-inclination LEO, particularly useful for gamma-ray astrophysics. (c) 2013 Elsevier B.V. All rights reserved.

Single-photon avalanche diodes (SPADs) achieving high timing resolution (≈20–50 ps) developed for time-correlated single-photon counting (TCSPC) generally have very small photosensitive areas (25–100 μm in diameter). This limits the achievable photon counting rate and signal-to-noise ratio and may lead to long counting times. This is detrimental in applications requiring several measurements, such as fluorescence lifetime imaging (FLIM) microscopy, which requires scanning, and time-domain diffuse optical tomography (TD-DOT). We show in this work that the use of an immersion lens directly affixed onto the photosensitive area of the SPAD helps alleviate this problem by allowing more light to be concentrated onto the detector. Following careful optical design and simulations, our experimental results show that it is actually possible to achieve the predicted theoretical increase in the photon counting rate (we achieve a factor of ≈4 here). This work is of high relevance in high timing resolution TCSPC with small photosensitive area detectors and should find widespread interest in FLIM and TD-DOT with SPADs.

The construction of a new prototype visible-light intensity interferometer for use in stellar astronomy is described. The instrument is located in New Haven, Connecticut, at Southern Connecticut State University, but key components of the system are also portable and have been taken to existing research-class telescopes to maximize sensitivity and baseline. The interferometer is currently a two-station instrument, but it is easily expandable to several stations for simultaneous measurement using multiple baselines. The design features single photon avalanche diode (SPAD) arrays, which increase the throughput and signal-to-noise ratio of the instrument. Predicted system performance and preliminary observations will be discussed.

Single Photon Avalanche Diodes (SPADs) are optical detectors with diameters ranging from few tens to few hundreds of microns. In case of single pixels, many research and industrial applications, such as Quantum Key Distribution systems, Particle Sizing measurements or single molecule experiments, require these detectors to be coupled with optic fibres. Article not available.

New detector modules exploit recent progress in the technology of silicon single-photon avalanche diodes (SPADs) and in the design of associated electronic circuits. SPAD detectors with diameter up to 100 mu m, good photon detection efficiency (48% peak at 550 nm wavelength) and low dark counting rate are used in these modules. Monolithic integrated active-quenching circuits (iAQC) and fast time-pickoff circuits ensure efficient photon counting and timing, with better than 50 ps FWHM time resolution and less than 50 ps centroid shift for counting rates LIP to 4 Mc/s. Experimental tests of the module performance and an application example are presented.

Optical quantum random number generators (QRNGs) are a special class of physical random data sources, whose randomness is established on elementary quantum optics processes. We present a QRNG based on a CMOS chip which overcomes the limitations of the commonly used optical QRNG and which achieves a random bit generation rate up to 200 Mb/s. The CMOS chip is based on an array of single-photon avalanche diodes (SPADs) and digital counters. We prove the absolute randomness of the generated random data through statistical test suites and even more stringent correlation and bias tests applied to 32 Gbit streams. The QRNG passes all tests; hence, it proves to be one of the fastest and more reliable CMOS optical QRNGs currently available.

A monolithic circuit has been designed for active-quenching and active-reset of single-photon avalanche diodes (SPADs), which operate above the breakdown voltage V/sub BD/ for detecting single photons. To the best of our knowledge, this is the first fully integrated circuit of this kind ever reported. It can operate with any available SPAD device, since it generates pulses high enough to quench detectors biased up to 20 V above V/sub BD/. The deadtime after each photon detection is adjustable; the minimum value is 50 ns, corresponding to 20 Mcounts/s maximum saturated photon-counting rate. The power dissipation is low (20-mW standby), suitable also for portable instruments. The small size and high reliability of the circuit make it possible to develop miniaturized detector modules and SPAD-array detector instruments. The circuit opens the path to new developments in many applications of photon counting, from DNA sequencing to ultrahigh-sensitivity imaging.

Design and fabrication of single photon avalanche detector (SPAD) in planar technology is reported. Device design and critical issues in the technology are discussed. Experimental test procedures are described for dark-counting rate, afterpulsing probability, photon timing resolution, and quantum detection efficiency. Low-noise detectors are obtained, with dark counting rates down to 10 c/s for devices with 10 /spl mu/m diameter, down to 1 kc/s for 50 /spl mu/m diameter. The technology is suitable for monolithic integration of SPAD detectors and associated circuits.

A bright photon source that combines high-fidelity entanglement, on-demand generation, high extraction efficiency, directional and coherent emission, as well as position control at the nanoscale is required for implementing ambitious schemes in quantum information processing, such as that of a quantum repeater. Still, all of these properties have not yet been achieved in a single device. Semiconductor quantum dots embedded in nanowire waveguides potentially satisfy all of these requirements; however, although theoretically predicted, entanglement has not yet been demonstrated for a nanowire quantum dot. Here, we demonstrate a bright and coherent source of strongly entangled photon pairs from a position controlled nanowire quantum dot with a fidelity as high as 0.859 +/- 0.006 and concurrence of 0.80 +/- 0.02. The two-photon quantum state is modified via the nanowire shape. Our new nanoscale entangled photon source can be integrated at desired positions in a quantum photonic circuit, single electron devices and light emitting diodes., Article and Supplementary Information with open access published at: http://www.nature.com/ncomms/2014/141031/ncomms6298/full/ncomms6298.html

We present a photon-counting module based on InGaAs/InP SPAD (Single-Photon Avalanche Diode) for detecting single photons up to 1.7 μm. The module exploits a novel architecture for generating and calibrating the gate width, along with other functions (such as module supervision, counting and processing of detected photons, etc.). The gate width, i.e. the time interval when the SPAD is ON, is user-programmable in the range from 500 ps to 1.5 μs, by means of two different delay generation methods implemented with an FPGA (Field-Programmable Gate Array). In order to compensate chip-to-chip delay variation, an auto-calibration circuit picks out a combination of delays in order to match at best the selected gate width. The InGaAs/InP module accepts asynchronous and aperiodic signals and introduces very low timing jitter. Moreover the photon counting module provides other new features like a microprocessor for system supervision, a touch-screen for local user interface, and an Ethernet link for smart remote control. Thanks to the fullyprogrammable and configurable architecture, the overall instrument provides high system flexibility and can easily match all requirements set by many different applications requiring single photon-level sensitivity in the near infrared with very low photon timing jitter.

With the recent progresses in quantum technologies, single photon sources have gained a primary relevance. Herewe present a heralded single photon source characterized by an extremely low level of noise photons, realizedby exploiting low-jitter electronics and detectors and fast custom-made electronics used to control an opticalshutter (a LiNbO 3 waveguide optical switch) at the output of the source. This single photon source showed asecond-order autocorrelation function g (2) (0) = 0: 005(7), and an Output Noise Factor (de ned as the ratio ofnoise photons to total photons at the source output) of 0 :25(1)%, among the best ever achieved.Keywords: quantum technologies, quantum information, quantum optics, single photon sources. 1. INTRODUCTION Many applicative and fundamental research elds such as quantum information, 1{3 quantum metrology, 4{8 andquantum mechanics foundations investigation 9{12 nd a fundamental tool in single photon sources, and as aconsequence there is much interest and e ort in improving their performances.

In the last years many progresses have been made in the field of silicon Single Photon Avalanche Diodes (SPAD) thanks to the improvements both in device design and in fabrication technology. Particularly, the Dipartimento di Elettronica e Informazione of Politecnico di Milano and the CNR-IMM of Bologna have been in the forefront of this research activity by designing and fabricating a new device structure enabling the fabrication of SPADs with red enhanced photon detection efficiency. In this paper we present a compact photon counting and timing module that fills the gap between the high temporal resolution and the high detection efficiency systems. The module exploits Red-Enhanced SPAD technology to attain a Photon Detection Efficiency (PDE) as high as 37 % at 800 nm (peak of 58 % at 600 nm) while maintaining a temporal resolution of about 100 ps FWHM, even with light diffused across the whole active area. A thermo-electric cooling system guarantees a noise as low as few counts per second for a 50 mu m diameter SPAD while a low threshold avalanche pick-up circuit assures a limited shift in the temporal response.

Low noise single-photon sources are a critical element for quantum technologies. We present a heralded single-photon source with an extremely low level of residual background photons, by implementing low-jitter detectors and electronics and a fast custom-made pulse generator controlling an optical shutter (a LiNbO3 waveguide optical switch) on the output of the source. This source has a second-order autocorrelation g^{(2)}(0)=0.005(7), and an "Output Noise Factor" (defined as the ratio of the number of noise photons to total photons at the source output channel) of 0.25(1)%. These are the best performance characteristics reported to date.

We present the design and performances of a radiation detector based on plastic scintillating fibers with doubleside readout by means of large-area Single Photon Avalanche Diodes (SPAD). This can be the basic step toward the realization of a large-area, cost-effective position sensitive detector to be employed in future space gammaray observatories. SPADs are silicon devices operated above the junction breakdown voltage (with the typical overvoltage of 5V), for which a single photon interacting in the active region is sufficient to trigger a selfsustainable avalanche discharge. SPADs can thus be used for the detection of very low light levels with a fast time response around 50ps FWHM for single photon detection, without spectroscopic capabilities. Large-area SPAD (500 μm in diameter) have been designed and fabricated at the CNR-IMM facility, with an intrinsic noise lower than 10kHz at -15°C, and are optically coupled to both ends of 3-meter long scintillating fibers, with the same diameter. Double-side readout is required to operate the devices in coincidence (10ns coincidence window), in order to reduce the rate of false detections to the level of 1Hz. The detectors have been tested with minimum ionizing particles at CERN PS demonstrating a detection efficiency larger than 90% and a moderate position resolution along the fiber due to the difference in time of arrival between the two photodetectors. Radiation hardness tests on SPADs have also been carried out, showing that large-area SPADs can be safely employed in low-inclination low Earth orbits.

We study the possibility to use Single Photon Avalanche Diodes (SPADs) optically coupled to scintillating fibers as a novel type of gamma-ray detector for space applications. SPADs are silicon devices operating under polarization conditions above the junction breakdown voltage (typical overvoltage of 5V), for which a single photon interacting in the active region is sufficient to trigger a self sustainable avalanche discharge. SPADs can thus be used for the detection of very low light levels with an absolute timing accuracy of about 30 ps for single photon detection, without spectroscopic capabilities. In this presentation we report the preliminary results on large area SPAD (actual results refers to SPADs having 200 µm diameter, with the aim to grow up to 500 µm SPADs) coupled to scintillating fibers as the basic module for a particle tracker for space application. Dark counts rate as low as few tens of kHz at room temperature, lowering down to few kHz at −10°C have been obtained for the 200 µm devices, in accordance with the basic requirements for the proposed application. Similar instruments based on silicon photomultiplier (SiPM) readout have already been studied, but none based on SPAD has been realized up to now. Moreover, since very few information is available on SPADs for the use in a space environment, we performed bulk damage and total dose radiation tests with protons and gamma-rays in order to evaluate their radiation hardness properties and their suitability for application in a Low Earth Orbit (LEO) space mission. With this aim the SPAD devices have be irradiated using up to 20 krad total dose with gamma-rays and 5 krad with protons.

Recent advances in fluorescence measurements for single molecule spectroscopy, genomics, proteomics and medical diagnostics require single-photon detectors with high quantum efficiency in the extended red spectral range (from 600 nm to 900 nm) and low noise (

We present a fully-integrated time-to-digital converter, in a standard 0.8/spl mu/m-CMOS technology, based on a cyclic pulse-shrinking design, that provides the lowest channel width of 20ps ever reported in literature for a single-shot measurements performed by monolithic circuits, with differential linearity errors lower than 10ps (less than 0.5LSB), conversion time shorter than 20/spl mu/s, and 18ns full-scale-range.

A technique for a separate experimental characterization of generation centres and deep levels in junctions is presented. The test device required is a small junction that operates in Geiger-mode above the breakdown level. Time-resolved measurements of correlated afterpulsing effects are exploited for separating noise contributions due to generation centres and to carrier trapping in deep levels. Release transients down to the nanosecond range are characterised and lifetimes of individual trap levels are measured. Experimental data for devices fabricated with different technologies illustrate the information gained about the efficiency of the fabrication process and in particular of gettering steps.

El objetivo de esta revisión fue de recopilar la información correspondiente a las bases y criterios para la obturación del sistema de conductos radiculares así como de los nuevos sistemas de obturación disponibles a nivel mundial, evaluando sus características, ventajas y desventajas.

Design and fabrication of single photon avalanche detector (SPAD) in planar technology is reported. Device design and critical issues in the technology are discussed. Experimental test procedures are described for dark-counting rate, afterpulsing probability, photon timing resolution, and quantum detection efficiency. Low-noise detectors are obtained, with dark counting rates down to 10 c/s for devices with 10 m diameter, down to 1 kc/s for 50 m diameter. The technology is suitable for monolithic integration of SPAD detectors and associated circuits.

The process-dependent defectivity of p-n junctions was investigated through the measurement of the avalanche triggering rate of single-photon avalanche diodes used as process probes. A nonlinear dependence of the ignition rate with the area of circular junctions is reported, which can be ascribed to a nonuniform density of the thermal generation centers, due to gettering. This has been verified by means of microscopic inspection and comparison with other available data. Technological hints are finally derived to counteract this nonuniformity.