Synchronization of quantum communications over an optical classical communications channel

Precise synchronization between a transmitter and receiver is crucial for quantum communications protocols such as quantum key distribution (QKD) to efficiently correlate the transmitted and received signals and increase the signal-to-noise ratio. In this work, we introduce a synchronization technique that exploits a co-propagating classical optical communications link and tests its performance in a free-space QKD system. Previously, existing techniques required additional laser beams or relied on the capability to retrieve the synchronization from the quantum signal itself; this approach, however, is not applicable in high channel loss scenarios. On the contrary, our method exploits classical and quantum signals locked to the same master clock, allowing the receiver to synchronize both the classical and quantum communications links by performing a clock-data-recovery routine on the classical signal. In this way, by exploiting the same classical communications already required for post-processing and key generation, no additional hardware is required, and the synchronization can be reconstructed from a high-power signal. Our approach is suitable for both satellite and fiber infrastructures, where a classical and quantum channel can be transmitted through the same link.

Fully Integrated Silicon Photonic Erbium-Doped Nanodiode for Few Photon Emission at Telecom Wavelengths

Recent advancements in quantum key distribution (QKD) protocols opened the chance to exploit nonlaser sources for their implementation. A possible solution might consist in erbium-doped light emitting diodes (LEDs), which are able to produce photons in the third communication window, with a wavelength around 1550 nm. Here, we present silicon LEDs based on the electroluminescence of Er:O complexes in Si. Such sources are fabricated with a fully-compatible CMOS process on a 220 nm-thick silicon-on-insulator (SOI) wafer, the common standard in silicon photonics. The implantation depth is tuned to match the center of the silicon layer. The erbium and oxygen co-doping ratio is tuned to optimize the electroluminescence signal. We fabricate a batch of Er:O diodes with surface areas ranging from 1 µm × 1 µm to 50 µm × 50 µm emitting 1550 nm photons at room temperature. We demonstrate emission rates around 5 × 106 photons/s for a 1 µm × 1 µm device at room temperature using superconducting nanowire detectors cooled at 0.8 K. The demonstration of Er:O diodes integrated in the 220 nm SOI platform paves the way towards the creation of integrated silicon photon sources suitable for arbitrary-statistic-tolerant QKD protocols.

The deep space quantum link: prospective fundamental physics experiments using long-baseline quantum optics

The National Aeronautics and Space Administration's Deep Space Quantum Link mission concept enables a unique set of science experiments by establishing robust quantum optical links across extremely long baselines. Potential mission configurations include establishing a quantum link between the Lunar Gateway moon-orbiting space station and nodes on or near the Earth. This publication summarizes the principal experimental goals of the Deep Space Quantum Link. These goals, identified through a multi-year design study conducted by the authors, include long-range teleportation, tests of gravitational coupling to quantum states, and advanced tests of quantum nonlocality.

Imaging of head and neck lipoblastoma: case report and systematic review

Lipoblastoma is a rare and benign tumour arising from embryonal fat cells, predominantly diagnosed in children younger than 3 years old. The most frequent locations are the extremities and trunk, while the head and neck areas are more rarely affected (10-15% of total cases). Clinically, the most common presentation is a fast-growing painless mass. Ultrasound is the first-line imaging examination, but Magnetic Resonance Imaging (MRI) allows for better definition of the relationships with the adjacent vascular and muscular structures. It can help to identify the lipomatous components, and it is useful for preoperative planning. However, the definitive diagnosis is provided by histopathological examination. Complete surgical excision is the first-line treatment, with a good prognosis in case of total eradication. We report the case of a 7-month-old male child with a rapidly growing mass that had typical radiological features of lipoblastoma.

Resource-effective quantum key distribution: a field trial in Padua city center

Field trials are of key importance for novel technologies seeking commercialization and widespread adoption. This is also the case for quantum key distribution (QKD), which allows distant parties to distill a secret key with unconditional security. Typically, QKD demonstrations over urban infrastructures require complex stabilization and synchronization systems to maintain a low quantum bit error and high secret key rates over time. Here we present a field trial that exploits low-complexity self-stabilized hardware and a novel synchronization technique, to perform QKD over optical fibers deployed in the city center of Padua, Italy. Two techniques recently introduced by our research group are evaluated in a real-world environment: the iPOGNAC polarization encoder was used for preparation of the quantum states, while temporal synchronization was performed with the Qubit4Sync algorithm. The results here presented demonstrate the validity and robustness of our resource-effective QKD system, which can be easily and rapidly installed in an existing telecommunication infrastructure, thus representing an important step towards mature, efficient, and low-cost QKD systems.

Stable, low-error, and calibration-free polarization encoder for free-space quantum communication

Polarization-encoded free-space quantum communication requires a quantum state source featuring fast modulation, long-term stability, and a low intrinsic error rate. Here we present a polarization encoder that, contrary to previous solutions, generates predetermined polarization states with a fixed reference frame in free-space. The proposed device does not require calibration either at the transmitter or at the receiver and achieves long-term stability. A proof-of-concept experiment is also reported, demonstrating a quantum bit error rate lower than 0.2% for several hours without any active recalibration.

All-fiber self-compensating polarization encoder for quantum key distribution

Quantum key distribution (QKD) allows distant parties to exchange cryptographic keys with unconditional security by encoding information on the degrees of freedom of photons. Polarization encoding has been extensively used for QKD along free-space, optical fiber, and satellite links. However, the polarization encoders used in such implementations are unstable, expensive, and complex and can even exhibit side channels that undermine the security of the protocol. Here we propose a self-compensating polarization encoder based on a lithium niobate phase modulator inside a Sagnac interferometer and implement it using only commercial off-the-shelf (COTS) components. Our polarization encoder combines a simple design and high stability reaching an intrinsic quantum bit error rate as low as 0.2%. Since realization is possible from the 800 to the 1550 nm band using COTS devices, our polarization modulator is a promising solution for free-space, fiber, and satellite-based QKD.

Hong-Ou-Mandel interference between independent III-V on silicon waveguide integrated lasers

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±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. This Letter 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.

Source-device-independent heterodyne-based quantum random number generator at 17 Gbps

Random numbers are commonly used in many different fields, ranging from simulations in fundamental science to security applications. In some critical cases, as Bell's tests and cryptography, the random numbers are required to be both private and to be provided at an ultra-fast rate. However, practical generators are usually considered trusted, but their security can be compromised in case of imperfections or malicious external actions. In this work we introduce an efficient protocol which guarantees security and speed in the generation. We propose a source-device-independent protocol based on generic Positive Operator Valued Measurements and then we specialize the result to heterodyne measurements. Furthermore, we experimentally implemented the protocol, reaching a secure generation rate of 17.42 Gbit/s, without the need of an initial source of randomness. The security of the protocol has been proven for general attacks in the finite key scenario.

Direct Reconstruction of the Quantum Density Matrix by Strong Measurements

New techniques based on weak measurements have recently been introduced to the field of quantum state reconstruction. Some of them allow the direct measurement of each matrix element of an unknown density operator and need only O(d) different operations, compared to d^{2} linearly independent projectors in the case of standard quantum state tomography, for the reconstruction of an arbitrary mixed state. However, due to the weakness of these couplings, these protocols are approximated and prone to large statistical errors. We propose a method which is similar to the weak measurement protocols but works regardless of the coupling strength: our protocol is not approximated and thus improves the accuracy and precision of the results with respect to weak measurement schemes. We experimentally apply it to the polarization state of single photons and compare the results to those of preexisting methods for different values of the coupling strength. Our results show that our method outperforms previous proposals in terms of accuracy and statistical errors.

Thyroid ultrasonography reporting: consensus of Italian Thyroid Association (AIT), Italian Society of Endocrinology (SIE), Italian Society of Ultrasonography in Medicine and Biology (SIUMB) and Ultrasound Chapter of Italian Society of Medical Radiology (SIRM)

Thyroid ultrasonography (US) is the gold standard for thyroid imaging and its widespread use is due to an optimal spatial resolution for superficial anatomic structures, a low cost and the lack of health risks. Thyroid US is a pivotal tool for the diagnosis and follow-up of autoimmune thyroid diseases, for assessing nodule size and echostructure and defining the risk of malignancy in thyroid nodules. The main limitation of US is the poor reproducibility, due to the variable experience of the operators and the different performance and settings of the equipments. Aim of this consensus statement is to standardize the report of thyroid US through the definition of common minimum requirements and a correct terminology. US patterns of autoimmune thyroid diseases are defined. US signs of malignancy in thyroid nodules are classified and scored in each nodule. We also propose a simplified nodule risk stratification, based on the predictive value of each US sign, classified and scored according to the strength of association with malignancy, but also to the estimated reproducibility among different operators.

Postselection-Loophole-Free Bell Violation with Genuine Time-Bin Entanglement

Entanglement is an invaluable resource for fundamental tests of physics and the implementation of quantum information protocols such as device-independent secure communications. In particular, time-bin entanglement is widely exploited to reach these purposes both in free space and optical fiber propagation, due to the robustness and simplicity of its implementation. However, all existing realizations of time-bin entanglement suffer from an intrinsic postselection loophole, which undermines their usefulness. Here, we report the first experimental violation of Bell's inequality with "genuine" time-bin entanglement, free of the postselection loophole. We introduced a novel function of the interferometers at the two measurement stations, that operate as fast synchronized optical switches. This scheme allowed us to obtain a postselection-loophole-free Bell violation of more than 9 standard deviations. Since our scheme is fully implementable using standard fiber-based components and is compatible with modern integrated photonics, our results pave the way for the distribution of genuine time-bin entanglement over long distances.

Exploring the boundaries of quantum mechanics: advances in satellite quantum communications

Recent interest in quantum communications has stimulated great technological progress in satellite quantum technologies. These advances have rendered the aforesaid technologies mature enough to support the realization of experiments that test the foundations of quantum theory at unprecedented scales and in the unexplored space environment. Such experiments, in fact, could explore the boundaries of quantum theory and may provide new insights to investigate phenomena where gravity affects quantum objects. Here, we review recent results in satellite quantum communications and discuss possible phenomena that could be observable with current technologies. Furthermore, stressing the fact that space represents an incredible resource to realize new experiments aimed at highlighting some physical effects, we challenge the community to propose new experiments that unveil the interplay between quantum mechanics and gravity that could be realizable in the near future.This article is part of a discussion meeting issue 'Foundations of quantum mechanics and their impact on contemporary society'.

Drug importation into Italy by body packing: An analysis of the UNODC Individual Drug Seizures Database

Internal concealment and transportation of illegal substances by body packing is a major business with very high profits, attracting criminals all over the world. As body packers are rarely arrested, it is difficult to quantify their proportion in the general population and, consequently, identify the countries involved in this kind of drug traffic; as a consequence, the percentage of undetected cases is undoubtedly high. The aim of this study is to provide useful information concerning the country of origin of body packers travelling to Italy through the analysis of the United Nations Office on Drugs and Crime Individual Drug Seizures Report database in the period 2010-2015. Results of our study highlighted a total of 85 cases, producing a total of 52.4 kg of drugs transported through body packing towards Italy. Data obtained from our analysis could represent an useful starting point to: (a) enhance police controls on people coming from targeted countries and improve collaborations between Italian Police Forces and those of other countries; (b) understand the reason why some cities/airports are so frequently used in drug trafficking through body packing and, as a consequence, enhance police controls in these places; and (c) train airport security staffs in international airports recognized as important departure points for body packers travelling to Italy.

Heroin-piracetam mixture: Suggested mechanisms of action and risks of misinterpretation for drug users

Piracetam is a positive allosteric modulator of the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor that has been frequently used in the treatment of cognitive disorders. Press and internet reports indicate that the use of piracetam, as a heroin adulterant, has spread rapidly in some countries, especially in Asia and Europe. Its use, as adulterant, is believed to produce more profound desirable effects, while decreasing hangover. Recent surveys demonstrated that piracetam protects neurons from heroin-induced apoptosis. The protective role of this adulterating substance may be related to restoration of beta-endorphin levels and to its neuroprotective effects. The aim of this paper is to review the relevant literature and suggest the main hypothetical mechanisms that justify its use as a heroin adulterant, try to understand if its use could help people who want to come off heroin by reducing withdrawal symptoms and, finally, give useful information that permit us to understand why drug trafficking organisations started to use piracetam as heroin adulterant.

Extending Wheeler's delayed-choice experiment to space

Gedankenexperiments have consistently played a major role in the development of quantum theory. A paradigmatic example is Wheeler's delayed-choice experiment, a wave-particle duality test that cannot be fully understood using only classical concepts. We implement Wheeler's idea along a satellite-ground interferometer that extends for thousands of kilometers in space. We exploit temporal and polarization degrees of freedom of photons reflected by a fast-moving satellite equipped with retroreflecting mirrors. We observe the complementary wave- or particle-like behaviors at the ground station by choosing the measurement apparatus while the photons are propagating from the satellite to the ground. Our results confirm quantum mechanical predictions, demonstrating the need of the dual wave-particle interpretation at this unprecedented scale. Our work paves the way for novel applications of quantum mechanics in space links involving multiple photon degrees of freedom.

Integrated optical modulator manipulating the polarization and rotation handedness of Orbital Angular Momentum states

Recent studies demonstrated that the optical channels encoded by Orbital Angular Momentum (OAM) are capable candidates for improving the next generation of communication systems. OAM states can enhance the capacity and security of high-dimensional communication channels in both classical and quantum regimes based on optical fibre and free space. Hence, fast and precise control of the beams encoded by OAM can provide their commercial applications in the compatible communication networks. Integrated optical devices are good miniaturized options to perform this issue. This paper proposes a numerically verified integrated high-frequency electro-optical modulator for manipulation of the guided modes encoded in both OAM and polarization states. The proposed modulator is designed as an electro-optically active Lithium Niobate (LN) core photonic wire with silica as its cladding in a LN on Insulator (LNOI) configuration. It consists of two successive parts; a phase shifter to reverse the rotation handedness of the input OAM state and a polarization converter to change the horizontally polarized OAM state to the vertically polarized one. It is shown that all four possible output polarization-OAM encoded states can be achieved with only 6 V and 7 V applied voltages to the electrodes in the two parts of the modulator.

Role of beam waist in Laguerre-Gauss expansion of vortex beams

Laguerre-Gauss (LG) modes represent an orthonormal basis set of solutions of the paraxial wave equation. LG modes are characterized by two integer parameters n and ℓ that are related to the radial and azimuthal profile of the beam. The physical dimension of the mode is instead determined by the beam waist parameter w₀: only LG modes with the same w₀ satisfy the orthogonality relation. Here, we derive the scalar product between two LG modes with different beam waists and show how this result can be exploited to derive different expansions of a generic beam in terms of LG modes. In particular, we apply our results to the recently introduced circular beams by deriving a previously unknown expansion. We finally show how the waist parameter must be chosen in order to optimize such expansion.

Source-Device-Independent Ultrafast Quantum Random Number Generation

Secure random numbers are a fundamental element of many applications in science, statistics, cryptography and more in general in security protocols. We present a method that enables the generation of high-speed unpredictable random numbers from the quadratures of an electromagnetic field without any assumption on the input state. The method allows us to eliminate the numbers that can be predicted due to the presence of classical and quantum side information. In particular, we introduce a procedure to estimate a bound on the conditional min-entropy based on the entropic uncertainty principle for position and momentum observables of infinite dimensional quantum systems. By the above method, we experimentally demonstrated the generation of secure true random bits at a rate greater than 1.7 Gbit/s.

Influence of short-term selenium supplementation on the natural course of Hashimoto's thyroiditis: clinical results of a blinded placebo-controlled randomized prospective trial

BACKGROUND

The real efficacy of selenium supplementation in Hashimoto's thyroiditis (HT) is still an unresolved issue.

OBJECTIVES

We studied the short-term effect of L-selenomethionine on the thyroid function in euthyroid patients with HT. Our primary outcome measures were TSH, thyroid hormones, thyroid peroxidase antibody (TPOAb), thyroglobulin antibody (TGAb) levels and thyroid echogenicity after 6 months of L-selenomethionine treatment. The secondary outcome measure was serum CXCL10 levels.

METHODS

In a placebo-controlled randomized prospective study, we have enrolled untreated euthyroid patients with HT. Seventy-six patients were randomly assigned to receive L-selenomethionine 166 µg/die (SE n = 38) or placebo (controls n = 38) for 6 months. TSH, free T₄ (FT₄), free T₃ (FT₃), TPOAb and CXCL10 serum levels were assayed at time 0, after 3 and 6 months. An ultrasound examination of the left and right thyroid lobe in transverse and longitudinal sections was performed. A rectangular region, the region of interest, was selected for analysis.

RESULTS

TSH, FT4, FT3, TPOAb, thyroid echogenicity and CXCL10 were not statistically different between SE and control groups at time 0, after 3 and 6 months. In the SE group, FT₄ levels were significantly decreased (P < 0.03) after 3 months, while FT₃ increased (P < 0.04) after 3 and 6 months versus baseline values. In the control group, the FT₃ decreased after 3 and 6 months (P < 0.02) compared to baseline.

CONCLUSION

The short-term L-selenomethionine supplementation has a limited impact on the natural course in euthyroid HT. Our results tip the balance toward the ineffectiveness of short-term L-selenomethionine supplementation in HT.

Birth and evolution of an optical vortex

When a phase singularity is suddenly imprinted on the axis of an ordinary Gaussian beam, an optical vortex appears and starts to grow radially, by effect of diffraction. This radial growth and the subsequent evolution of the optical vortex under focusing or imaging can be well described in general within the recently introduced theory of circular beams, which generalize the hypergeometric-Gaussian beams and which obey novel kinds of ABCD rules. Here, we investigate experimentally these vortex propagation phenomena and test the validity of circular-beam theory. Moreover, we analyze the difference in radial structure between the newly generated optical vortex and the vortex obtained in the image plane, where perfect imaging would lead to complete closure of the vortex core.

Interference at the Single Photon Level Along Satellite-Ground Channels

Quantum interference arising from the superposition of states is striking evidence of the validity of quantum mechanics, confirmed in many experiments and also exploited in applications. However, as for any scientific theory, quantum mechanics is valid within the limits in which it has been experimentally verified. In order to extend such limits, it is necessary to observe quantum interference in unexplored conditions such as moving terminals at large distances in space. Here, we experimentally demonstrate single photon interference at a ground station due to the coherent superposition of two temporal modes reflected by a rapidly moving satellite a thousand kilometers away. The relative speed of the satellite induces a varying modulation in the interference pattern. The measurement of the satellite distance in real time by laser ranging allows us to precisely predict the instantaneous value of the interference phase. We then observed the interference patterns with a visibility up to 67% with three different satellites and with a path length up to 5000 km. Our results attest to the viability of photon temporal modes for fundamental tests of physics and quantum communication in space.

Free-space optical channel estimation for physical layer security

We present experimental data on message transmission in a free-space optical (FSO) link at an eye-safe wavelength, using a testbed consisting of one sender and two receiver terminals, where the latter two are a legitimate receiver and an eavesdropper. The testbed allows us to emulate a typical scenario of physical-layer (PHY) security such as satellite-to-ground laser communications. We estimate information-theoretic metrics including secrecy rate, secrecy outage probability, and expected code lengths for given secrecy criteria based on observed channel statistics. We then discuss operation principles of secure message transmission under realistic fading conditions, and provide a guideline on a multi-layer security architecture by combining PHY security and upper-layer (algorithmic) security.

Strong Measurements Give a Better Direct Measurement of the Quantum Wave Function

Weak measurements have thus far been considered instrumental in the so-called direct measurement of the quantum wave function [4J. S. Lundeen, Nature (London) 474, 188 (2011).]. Here we show that a direct measurement of the wave function can be obtained by using measurements of arbitrary strength. In particular, in the case of strong measurements, i.e., those in which the coupling between the system and the measuring apparatus is maximum, we compared the precision and the accuracy of the two methods, by showing that strong measurements outperform weak measurements in both for arbitrary quantum states in most cases. We also give the exact expression of the difference between the original and reconstructed wave function obtained by the weak measurement approach; this will allow one to define the range of applicability of such a method.

Experimental Satellite Quantum Communications

Quantum communication (QC), namely, the faithful transmission of generic quantum states, is a key ingredient of quantum information science. Here we demonstrate QC with polarization encoding from space to ground by exploiting satellite corner cube retroreflectors as quantum transmitters in orbit and the Matera Laser Ranging Observatory of the Italian Space Agency in Matera, Italy, as a quantum receiver. The quantum bit error ratio (QBER) has been kept steadily low to a level suitable for several quantum information protocols, as the violation of Bell inequalities or quantum key distribution (QKD). Indeed, by taking data from different satellites, we demonstrate an average value of QBER=4.6% for a total link duration of 85 s. The mean photon number per pulse μ_{sat} leaving the satellites was estimated to be of the order of one. In addition, we propose a fully operational satellite QKD system by exploiting our communication scheme with orbiting retroreflectors equipped with a modulator, a very compact payload. Our scheme paves the way toward the implementation of a QC worldwide network leveraging existing receivers.

On the properties of circular beams: normalization, Laguerre-Gauss expansion, and free-space divergence

Circular beams were introduced as a very general solution to the paraxial wave equation carrying orbital angular momentum. Here, we study their properties by looking at their normalization and their expansion in terms of Laguerre-Gauss modes. We also study their far-field divergence and, for particular cases of the beam parameters, their possible experimental generation.

Free-space quantum key distribution by rotation-invariant twisted photons

"Twisted photons" are photons carrying a well-defined nonzero value of orbital angular momentum (OAM). The associated optical wave exhibits a helical shape of the wavefront (hence the name) and an optical vortex at the beam axis. The OAM of light is attracting a growing interest for its potential in photonic applications ranging from particle manipulation, microscopy, and nanotechnologies to fundamental tests of quantum mechanics, classical data multiplexing, and quantum communication. Hitherto, however, all results obtained with optical OAM were limited to laboratory scale. Here, we report the experimental demonstration of a link for free-space quantum communication with OAM operating over a distance of 210 m. Our method exploits OAM in combination with optical polarization to encode the information in rotation-invariant photonic states, so as to guarantee full independence of the communication from the local reference frames of the transmitting and receiving units. In particular, we implement quantum key distribution, a protocol exploiting the features of quantum mechanics to guarantee unconditional security in cryptographic communication, demonstrating error-rate performances that are fully compatible with real-world application requirements. Our results extend previous achievements of OAM-based quantum communication by over 2 orders of magnitude in the link scale, providing an important step forward in achieving the vision of a worldwide quantum network.

Ultrasound scanning in infants with biliary atresia: the different implications of biliary tract features and liver echostructure

OBJECTIVE

To evaluate ultrasonographic features of the liver and biliary tree, including the presence of the triangular cord, in infants with biliary atresia and to analyze the correspondence between hepatic echostructure and histological aspects of the liver.

MATERIALS AND METHODS

35 consecutive infants (19 males) with documented diagnosis of biliary atresia were included. Ultrasonography evaluation, performed at a mean age of 63.1 ± 34.9 days, was focused on the extrahepatic bile ducts, characteristics of the gallbladder and liver, and the presence of the triangular cord. Liver biopsies were examined with particular regard to the presence and severity of fibrosis.

RESULTS

On ultrasound, the gallbladder was not seen in 11 (31 %) cases, while in the remaining 24 patients the gallbladder was regular in 6 patients and irregular in 18 cases. The triangular cord was identified in 9 (26 %) of 35 patients. In 21 patients the liver echostructure appeared normal, while in 14 infants the liver parenchyma was more echogenic and coarse than normal. Liver biopsy showed signs of cirrhosis or fibrosis in all cases, including patients with a normal hepatic echostructure.

CONCLUSION

Although the triangular cord was visualized in one-fourth of the infants with biliary atresia, abnormalities of the gallbladder on ultrasound (absence or abnormalities of length/shape) were detected in 83 % of the patients. Therefore, ultrasound evaluation of the liver and biliary tree plays an important role in suspecting biliary atresia. On the other hand, a low correspondence between liver echostructure aspects and the presence and severity of fibrosis at liver biopsy was identified. Therefore, severe liver disease in infants with biliary atresia cannot be excluded only on the basis of ultrasound findings.

Imperforate hymen causing congenital hydrometrocolpos

A 3-day-old girl in good health was referred to our department for the evaluation of an abdominal mass detected at birth. Prenatal ultrasound (US) examinations had shown no anomaly. US examination revealed the presence of a hypoechoic and corpusculated cystic formation of about 8 × 5 × 4 cm located in the mid region of the abdomen. The uterus was not visible and the kidneys were normal with no sign of hydronephrosis. The ovaries were normal. Physical examination confirmed US findings revealing the presence of a curved membrane which covered the vaginal opening. Based on these findings, the patient was diagnosed to have hydrometrocolpos. Hymenectomy was performed and about 100 ml of milky fluid was subsequently removed by aspiration. The patient presented no other congenital anomalies and US follow-up showed a normal structure of the uterus.

Gastrointestinal perforation: ultrasonographic diagnosis

Gastrointestinal tract perforations can occur for various causes such as peptic ulcer, inflammatory disease, blunt or penetrating trauma, iatrogenic factors, foreign body or a neoplasm that require an early recognition and, often, a surgical treatment.Ultrasonography could be useful as an initial diagnostic test to determine, in various cases the presence and, sometimes, the cause of the pneumoperitoneum.The main sonographic sign of perforation is free intraperitoneal air, resulting in an increased echogenicity of a peritoneal stripe associated with multiple reflection artifacts and characteristic comet-tail appearance.It is best detected using linear probes in the right upper quadrant between the anterior abdominal wall, in the prehepatic space.Direct sign of perforation may be detectable, particularly if they are associated with other sonographic abnormalities, called indirect signs, like thickened bowel loop and air bubbles in ascitic fluid or in a localized fluid collection, bowel or gallbladder thickened wall associated with decreased bowel motility or ileus.Neverthless, this exam has its own pitfalls. It is strongly operator-dependant; some machines have low-quality images that may not able to detect intraperitoneal free air; furthermore, some patients may be less cooperative to allow for scanning of different regions; sonography is also difficult in obese patients and with those having subcutaneous emphysema. Although CT has more accuracy in the detection of the site of perforation, ultrasound may be particularly useful also in patient groups where radiation burden should be limited notably children and pregnant women.

Optimization of two-photon wave function in parametric down conversion by adaptive optics control of the pump radiation

We present an efficient method for optimizing the spatial profile of entangled-photon wave function produced in a spontaneous parametric down conversion process. A deformable mirror that modifies a wavefront of a 404 nm CW diode laser pump interacting with a nonlinear β-barium borate type-I crystal effectively controls the profile of the joint biphoton function. The use of a feedback signal extracted from the biphoton coincidence rate is used to achieve the optimal wavefront shape. The optimization of the two-photon coupling into two, single spatial modes for correlated detection is used for a practical demonstration of this physical principle.

Impact of turbulence in long range quantum and classical communications

The study of the free-space distribution of quantum correlations is necessary for any future application of quantum and classical communication aiming to connect two remote locations. Here we study the propagation of a coherent laser beam over 143 km (between Tenerife and La Palma Islands of the Canary archipelagos). By attenuating the beam we also studied the propagation at the single photon level. We investigated the statistic of arrival of the incoming photons and the scintillation of the beam. From the analysis of the data, we propose the exploitation of turbulence to improve the signal to noise ratio of the signal.

Experimental quantum networking protocols via four-qubit hyperentangled Dicke states

We report the experimental demonstration of two quantum networking protocols, namely quantum 1→3 telecloning and open-destination teleportation, implemented using a four-qubit register whose state is encoded in a high-quality two-photon hyperentangled Dicke state. The state resource is characterized using criteria based on multipartite entanglement witnesses. We explore the characteristic entanglement-sharing structure of a Dicke state by implementing high-fidelity projections of the four-qubit resource onto lower-dimensional states. Our work demonstrates for the first time the usefulness of Dicke states for quantum information processing.

Two-particle bosonic-fermionic quantum walk via integrated photonics

Quantum walk represents one of the most promising resources for the simulation of physical quantum systems, and has also emerged as an alternative to the standard circuit model for quantum computing. Here we investigate how the particle statistics, either bosonic or fermionic, influences a two-particle discrete quantum walk. Such an experiment has been realized by exploiting polarization entanglement to simulate the bunching-antibunching feature of noninteracting bosons and fermions. To this scope a novel three-dimensional geometry for the waveguide circuit is introduced, which allows accurate polarization independent behavior, maintaining remarkable control on both phase and balancement.

Experimental realization of optimal noise estimation for a general Pauli channel

We present the experimental realization of the optimal estimation protocol for a Pauli noisy channel. The method is based on the generation of 2-qubit Bell states and the introduction of quantum noise in a controlled way on one of the state subsystems. The efficiency of the optimal estimation, achieved by a Bell measurement, is shown to outperform quantum process tomography.

Intrahepatic portal-vein gas associated with rotavirus infection

Rotavirus enteritis is an infectious disease of the small bowel caused by an RNA reovirus. It is manifested by cytotoxic diarrhea [1]. Rotavirus is the most common viral cause of enteritis (incidence 15-35%) [2]. In infants and children with abdominal pain and diarrhea, ultrasonography is the diagnostic study of choice, and its use has increased significantly in young patients. We describe two cases in which portal-vein gas was detected on abdominal ultrasound scans in children with severe dehydration secondary to rotavirus gastroenteritis, which resolved rapidly after treatment.

Hyperentangled mixed phased Dicke states: optical design and detection

A recently introduced family of multipartite entangled states, the 4-qubit phased Dicke states, has been created by 2-photon hyperentanglement. Our experimental method allows high state fidelity and generation rate. By introducing quantum noise in the multipartite system in a controlled way, we have tested the robustness of these states. To this purpose the entanglement of the resulting multipartite entangled mixed states has been verified by using a new kind of structural witness.

Polarization entangled state measurement on a chip

The emerging strategy to overcome the limitations of bulk quantum optics consists of taking advantage of the robustness and compactness achievable by integrated waveguide technology. Here we report the realization of a directional coupler, fabricated by femtosecond laser waveguide writing, acting as an integrated beam splitter able to support polarization-encoded qubits. This maskless and single step technique allows us to realize circular transverse waveguide profiles which are able to support the propagation of gaussian modes with any polarization state. Using this device, we demonstrate quantum interference with polarization-entangled states and singlet state projection.

Experimental entanglement and nonlocality of a two-photon six-qubit cluster state

We create a six-qubit linear cluster state by transforming a two-photon hyperentangled state in which three qubits are encoded in each particle, one in the polarization and two in the linear momentum degrees of freedom. For this state, we demonstrate genuine six-qubit entanglement, persistency of entanglement against the loss of qubits, and higher violation than in previous experiments on Bell inequalities of the Mermin type.

Multipath entanglement of two photons

We present a novel optical device based on an integrated system of microlenses and single-mode optical fibers. It allows us to collect and direct into many modes two photons generated by spontaneous parametric down-conversion. By this device multiqubit entangled states and/or multilevel qudit states of two photons, encoded in the longitudinal momentum degree of freedom, are created. The multipath photon entanglement realized by this device is expected to find important applications in modern quantum information technology.

Proposed bell experiment with genuine energy-time entanglement

Franson's Bell experiment with energy-time entanglement [Phys. Rev. Lett. 62, 2205 (1989)10.1103/PhysRevLett.62.2205] does not rule out all local hidden variable models. This defect can be exploited to compromise the security of Bell inequality-based quantum cryptography. We introduce a novel Bell experiment using genuine energy-time entanglement, based on a novel interferometer, which rules out all local hidden variable models. The scheme is feasible with actual technology.

Active one-way quantum computation with two-photon four-qubit cluster states

By using 2-photon 4-qubit cluster states we demonstrate deterministic one-way quantum computation in a single qubit rotation algorithm. In this operation feed-forward measurements are automatically implemented by properly choosing the measurement basis of the qubits, while Pauli error corrections are realized by using two fast driven Pockels cells. We realized also a C-NOT gate for equatorial qubits and a C-PHASE gate for a generic target qubit. Our results demonstrate that 2-photon cluster states can be used for rapid and efficient deterministic one-way quantum computing.

Realization and characterization of a two-photon four-qubit linear cluster state

We report on the experimental realization of a four-qubit linear cluster state via two photons entangled both in polarization and linear momentum. This state was investigated by performing tomographic measurements and by evaluating an entanglement witness. By use of this state we carried out a novel nonlocality proof, the so-called "stronger two observer all-versus-nothing" test of quantum nonlocality.

Endocrine dysfunction in patients with Fabry disease

BACKGROUND

Fabry disease (FD) is a genetic disorder caused by lysosomal alpha-galactosidase-A deficiency and is characterized by the systemic accumulation of globotriaosylceramide. All endocrine glands are susceptible to globotriaosylceramide accumulation because of their high vascularization and low cellular proliferation rate. Nevertheless, this endocrine system has never been investigated in detail.

OBJECTIVE

We aimed to investigate the function and morphology of the endocrine glands in FD.

PATIENTS

The thyroid, gonadal, adrenal, and GH/IGF-I axes were evaluated in 18 FD patients (nine females and nine males, aged 21-64 yr) and 18 sex- and age-matched healthy subjects.

STUDY DESIGN

We conducted an observational, analytical, open, prospective study.

INTERVENTIONS

Ten of the 18 patients received enzyme replacement therapy (ERT) with recombinant human alpha-galactosidase-A (agalsidase beta) at a dose of 1 mg/kg body weight every 2 wk.

RESULTS

FD patients had higher baseline TSH levels than controls (P < 0.01). Three subjects were diagnosed with an early stage of subclinical primary hypothyroidism associated with negative antithyroid antibodies. A history of menses abnormalities, miscarriage, or assisted delivery was found in 89% of FD women. Asthenozoospermia, oligozoospermia, or both were found in all FD men through seminal fluid analysis. FD patients had significantly higher circulating ACTH and lower cortisol levels than controls (P < 0.05). In patients under ERT, a suboptimal cortisol response to the 250-microg ACTH test was found in 10%, and the ACTH-stimulated cortisol peak was significantly correlated to the health status profile (P < 0.05).

CONCLUSION

A variety of latent endocrine dysfunctions, including life-threatening conditions, occur in patients with FD. Endocrine dysfunctions are also present in patients already receiving ERT and are in part related to their persistent poor quality of life. An endocrine work-up should be recommended in all FD patients. Adequate monitoring and hormonal therapy, when required, have to be performed in cases of subclinical endocrine dysfunction to avoid life-threatening events.

Enhancing the violation of the einstein-podolsky-rosen local realism by quantum hyperentanglement

Mermin's observation [Phys. Rev. Lett. 65, 1838 (1990)] that the magnitude of the violation of local realism, defined as the ratio between the quantum prediction and the classical bound, can grow exponentially with the size of the system is demonstrated using two-photon hyperentangled states entangled in polarization and path degrees of freedom, and local measurements of polarization and path simultaneously.

[Current trend in the diagnosis and treatment of primary non refluxing megaureter]

BACKGROUND

The terms megaureter or hydroureteronephrosis are non-specific because indicate various pathologic entities recognise different causes (obstruction, reflux, obstruction-reflux, primary and secondary). An undeveloped renal function in neonatal period makes more difficult the therapeutic approach. Actually the problem is to find the indicators that consent us the individualization of patients more suitable for nonoperative management.

METHODS

From 1996 to 2002, we observed 60 patients with 74 megaureters. In 24 cases the diagnosis was antenatal, 6 cases were diagnosed immediately after birth, 13 in the first year of life and 17 after the first year (2y-10y). Patients were classified in two groups based on age; 43 cases diagnosed in the first year of life and 17 after. Both of them were classified in two further groups based on ureteral size and renal function, scintigraphically evaluated.

RESULTS

In the first group (A) ureters with 10 mm of dilatation improved in 38.9% of the cases. Were stationary 50% and impaired 11,1% of them. Ureters with dilatation between 7 and 10 mm improved in 24%, were stationary in 72% and impaired in in 4% of the cases. Ureters with less than 7mm dilatation improved in 35.2% and were stationary in 64.8%. In the group A renal scintigraphy MAG3 demonstrated, in the patients with acceptable renal function and washout, an improvement in 65% of the cases. Was stationary in 30% and impaired in 10%.

CONCLUSIONS

The grade of dilatation evaluated with ultrasonographic exam and the study of renal function with diuresis renal scintigraphy using Tc-99m MAG3 and washout grade with diuresis renal scintigraphy are remarkable markers for the treatment choice.