International and National Journals

N. Antonietti, M. Mondin, G. Catastini, G. Brida, M. Genovese
Systematic Numerical Study of the Propagation of Monochromatic Radiation through a Stationary Atmosphere in a Model of Plane-Parallel Layers
Laser Physics, Vol. 17, no. 12, pp. 1389-1397, 2007 (IF 0,696).

Quantum communication in free space is the next challenge of telecommunications. With the purpose to determine the outcome of quantum communication by means of single photons, one needs to clearly estimate atmosphere effects. In this article we present a systematical study of radiation transfer trough a static atmosphere based on numerical simulation results.

N. Antonietti, M. Mondin, G. Brida, M. Genovese
Numerical Characterization of atmospheric effects on an earth-space quantum communication channel
International Journal of Quantum Information, Vol. 5, nos. 1 & 2, pp. 241-248, 2007 (IF 0,568).

Quantum communication in free space is the next challenge of telecommunications. Since we want to determine the outcome of quantum communication by means of single photons, we must understand how a single photon interacts with the atmosphere. In this brief article, some simulation results for realistic and generic atmospheric conditions are reported, a related experiment is considered and its results are described and discussed.

G. Brida, N. Antonietti, M. Gramegna, L. Krivitsky, F. Piacentini, M.L. Rastello, I. Ruo Berchera, P. Traina, M. Genovese, E. Predazzi
Recent experiments performed at "Carlo Novero" lab at INRIM on quantum information and foundations of quantum mechanics
International Journal of Quantum Information, Vol. 5, nos. 1 & 2, pp. 265-272, 2007 (IF 0,568).

In this paper we present some recent work performed at "Carlo Novero" lab on Quantum Information and Foundations of Quantum Mechanics.

G. Brida, M. Genovese, L. A. Krivitsky, M. V. Chekhova
Dispersion spreading of polarization entangled states of light and two photon interference
Laser Physics, Vol. 17, pp. 567-575, 2007 (IF 0,696).

In this paper we present our study on the possibility of generation of a continuous set of frequency-polarization entangled states exploiting the process of spontaneous parametric down conversion (SPDC) in a single nonlinear crystal. The main idea is to make a narrow frequency selection in natural bandwidth of SPDC in collinear configuration. Similar results can be obtain by time selection. We show the experimental possibility to generate a particular singlet Bell state which is invariant under polarization fluctuations.

G. Brida, M. Chekhova, M. Genovese, A. Penin, M. L. Rastello, I. Ruo-Berchera
Absolute calibration of analog detectors by using parametric down conversion
IEEE Transactions on Instrumentation and Measurement, Vol. 56, no. 2, pp. 275-279, 2007 (IF 0,832).

In this paper we report our systematic study of a promising absolute calibration technique of analog photo-detectors, based on the properties of parametric down conversion. Our formal results and a preliminary uncertainty analysis show that the proposed method can be effectively developed with interesting applications to metrology.

G. Brida, M. Genovese, M.G.A. Paris, F. Piacentini, E. Predazzi, E. Vallauri
On reconstructing photon statistics by on/off detectors: Toward the multi-partite case
Optics and Spectroscopy, Vol. 103, no. 1, pp. 90-97, 2007 (IF 0,688).

Reconstruction of photon statistics of optical states provides fundamental information on the nature of any optical field and finds various relevant applications. Nevertheless, no detector that can well discriminate the number of incident photons is available. On the other hand reconstruction by quantum tomography is not an easily implementable technique suited for a diffuse use. Even if on/off detectors, as usual avalanche photodiodes operating in Geiger mode, seem useless as photocounters, recently it was shown how reconstruction of photon statistics is possible by considering a variable quantum efficiency. We have experimentally demonstrated the potentialities of this technique by reconstructing photon statistics for various optical fields both in cw and pulsed regime ranging from heralded photon states to multi-thermal and coherent ones. In this paper, after having introduced the method, we review the results obtained for the mono-partite case and we present in detail the extension to bi-partite case.

G. Brida, M. Genovese, F. Piacentini
Experimental local realism test without fair sampling assumption
European Physical Journal D, Vol. 44, no. 3, pp. 577-580, 2007 (IF 1,828).

Following the theoretical suggestion of a recent paper, we present experimental results addressed to test restricted families of local realistic models, but without relying on the fair sampling assumption.

G. Brida, M. Genovese, A. Krivitsky, M. Chekhova
Two-photon entanglement generation: different Bell states within the linewidth of phase-matching
Optics Express, Vol. 15, pp. 10182-10188, 2007 (IF 3,709).

It is shown that for a phase-matched nonlinear process producing entangled states, different Bell states are generated for different mismatch values. In particular, generation of the singlet Bell state is demonstrated within the natural linewidth of collinear frequency-degenerate type-II spontaneous parametric down-conversion (SPDC) without the o-e delay compensation. The singlet state can be filtered out by spectral selection or by the time selection of the two-photon amplitude at the output of a dispersive fibre. The effect is of considerable importance for fibre quantum communication.

G. Brida, M. Genovese, L.A Krivitsky, M.V. Chekova
Interference structure of two-photon amplitude revealed by dispersion spreading
Physical Review A, Vol. 75, pp. 015801, 2007 (IF 2,893).

Entanglement is a fundamental resource for various applications ranging from quantum communication and calculus to quantum imaging and metrology. Efficient sources of Polarization Entangled States (PES) represent the most widespread tool for generating entangled states. Thus, the search for efficient high visibility sources of these states is of the utmost importance. Here we present the previously undiscussed phenomenon of the presence of a continuous of maximally entangled states with different relative phases inside the angular (and frequency) bandwidth of SPDC PES sources. We show how this effect can be compensated for realizing a more efficient.

G. Brida, M. Genovese, L.A. Krivitsky, M.V. Chekova, E. Predazzi
Go and return propagation of biphotons in fibre and polarization entanglement
Journal of Physics A: Mathematical and theoretical, Vol. 40, pp. 7985-7992, 2007 (IF 1,680).

Propagation of entangled photons in optical fiber is one of the fundamental issues for realizing quantum communication protocols. When entanglement in polarization is considered, a problem of compensating for the fiber effect on photons polarization arises. In this paper we demonstrate an effective solution where a Faraday mirror allows to cancel undesired effects of polarization drift in fiber. This technique is applied to a protocol for generating Bell states by a narrow temporal selection of the second-order intensity correlation function.

G. Brida, M. Genovese, L.A. Krivitsky, M.V. Chekova
Generation of different Bell states within the SPDC phase matching bandwidth
Physical Review A, Vol. 76, pp. 053807, 2007 (IF 2,893).

We study the frequency-angular lineshape for a phase-matched nonlinear process producing entangled states and show that there is a continuous variety of maximally-entangled states generated for different mismatch values within the natural bandwidth. Detailed considerations are made for two specific methods of polarization entanglement preparation, based on type-II spontaneous parametric down-conversion (SPDC) and on SPDC in two subsequent type-I crystals producing orthogonally polarized photon pairs. It turns out that different Bell states are produced at the center of the SPDC line and on its slopes, corresponding to about half-maximum intensity level. These Bell states can be filtered out by either frequency selection or angular selection, or both. Our theoretical calculations are confirmed by a series of experiments, performed for the two above-mentioned schemes of producing polarization-entangled photon pairs and with two kinds of measurements: frequency-selective and angular-selective.

D. Calonico, A. Cina, I. H. Bendea, F. Levi, L. Lorini, A. Godone
Gravitational redshift at INRIM
Metrologia, Vol. 44, no. 5, L44-L48, 2007 (IF 1,667).

The gravitational redshift is one of the main biases in the comparison of primary frequency standards; even if it is not a limit for the present accuracy of the microwave frequency standards such as Cs beam or fountain clocks, it could be a challenge for the forthcoming generation of atomic optical clocks. In this article we report the evaluation of the gravitational redshift with respect to the Geoid reference at Istituto Nazionale di Ricerca Metrologica (INRIM) laboratories, with an accuracy of 1 × 10^-17 in terms of relative frequency. The evaluation is based on GPS/levelling measurements and on the use of both a local and a global model for the Earth Geoid; the main limitation to the accuracy is given by the Geoid reference potential itself.

C.E. Calosso, S. Micalizio, A. Godone, E. Bertacco, F. Levi
Electronics for the Pulsed Rubidium Clock: Design and Characterization
IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, Vol. 54, no. 9, pp. 1731-1740, 2007 (IF 1,654).

The paper presents the electronics we developed for a pulsed optically pumped vapor-cell frequency standard based on rubidium atoms with buffer gas. Pulsing the different operation phases of a vapor-cell clock (optical pumping, interrogation and detection) has been recognized as one of the most effective technique to reduce light shift and then to improve the stability perspectives of vapor cell clocks. However, in order to take full advantage of the pulsed scheme, a fast gated electronics is required, being the times involved of the order of milliseconds. In this paper we describe the design and the implementation of the clock electronics, that synchronizes the different phases of the clock operation, as well as of the control electronics that is mainly devoted to the thermal stabilization of the clock physics package. We also report some characterization measurements, including a measurement of the clock frequency stability. In particular, in terms of Allan deviation, we measured a frequency stability of 1.2 · 10^-12 τ^-1/2 for averaging times up to τ = 10⁵ s, a very interesting result for a possible space application of such a clock.

S. Castelletto, I. P. Degiovanni, V. Schettini, A. L. Migdall
Reduced Deadtime and Higher Rate Photon-Counting Detection Using a Multiplexed Detector Array
Journal of Modern Optics, Vol. 54, pp. 337-352, 2007 (IF 1,074).

We present a scheme for a photon-counting detection system that can be operated at incident photon rates higher than otherwise possible by suppressing the effects of detector deadtime. The method uses an array of N detectors and a 1-by-N optical switch with a control circuit to direct input light to live detectors. Our calculations and models highlight the advantages of the technique. In particular, using this scheme, a group of N detectors provides an improvement in operation rate that can exceed the improvement that would be obtained by a single detector with deadtime reduced by 1/N, even if it were feasible to produce a single detector with such a large improvement in deadtime. We model the system for continuous and pulsed light sources, both of which are important for quantum metrology and quantum key distribution applications.

J. Cheung, A. Migdall, S. Castelletto
Special issue: Single-photon: Sources, detectors, applications and measurement methods - Introduction
Journal of Modern Optics, Vol. 54, nos. 2-3, pp. 137-139, 2007 (IF 1,074).

I.P. Degiovanni, S. Castelletto, E. Puddu, A. Andreoni, M. Bondani
Ghost imaging with intense correlated light
International Journal of Quantum Information, Vol. 5, nos. 1 & 2, pp. 33-36, 2007 (IF 0,568).

We present a new ghost-imaging experiment that is realized by exploiting two intense correlated beams. The beams involved are signal and idler of a seeded parametric downconversion. The peculiarity of this scheme is that the seed field is an intense pseudo-thermal field generated by passing a laser beam through two rotating ground glass plates.

I. P. Degiovanni, M. Bondani, E. Puddu, A. Andreoni, M. G. A. Paris
Intensity correlations, entanglement properties, and ghost imaging in multimode thermal-seeded parametric downconversion: Theory
Physical Review A, Vol. 76, p. 062309, 2007 (IF 2,893).

We address parametric down-conversion seeded by multimode pseudothermal fields. We show that this process may be used to generate multimode pairwise correlated states with entanglement properties that can be tuned by controlling the seed intensities. Parametric down-conversion seeded by multimode pseudothermal fields represents a source of correlated states, which allows one to explore the classical-quantum transition in pairwise correlations and to realize ghost imaging and ghost diffraction in regimes not yet explored by experiments.

T. M. Fortier, N. Ashby, J. C. Bergquist, M. J. Delaney, S. A. Diddams, T. P. Heavner, L. Hollberg, W. M. Itano, S. R. Jefferts, K. Kim, F. Levi, L. Lorini, W. H. Oskay, T. E. Parker, J. Shirley, J. E. Stalnaker
Precision atomic spectroscopy for improved limits on variation of the fine structure constant and local position invariance
Physical Review Letters, Vol. 98, p. 070801, 2007 (IF 6,944).

We report tests of local position invariance and the variation of fundamental constants from measurements of the frequency ratio of the 282-nm ¹⁹⁹Hg⁺ optical clock transition to the ground state hyperfine splitting in ¹³³Cs. Analysis of the frequency ratio of the two clocks, extending over 6 yr at NIST, is used to place a limit on its fractional variation of < 5.8×10^-6 per change in normalized solar gravitational potential. The same frequency ratio is also used to obtain 20-fold improvement over previous limits on the fractional variation of the fine structure constant of |α/α| < 1.3×10^-16 yr^-1, assuming invariance of other fundamental constants. Comparisons of our results with those previously reported for the absolute optical frequency measurements in H and ¹⁷¹Yb⁺ vs. other ¹³³Cs standards yield a coupled constraint of -1.5×10^-15 <|α/α| <0.4×10^-15 yr^-1 and -2.7×10^-15 <d/DT [ln(µ_Cs/µ_B)] < 8.6×10^-15 yr^-1.

L. Galleani, P. Tavella
Characterization of nonstationary atomic clocks
Fluctuation and Noise Letters, Vol. 70, No. 4 (2007), pp L461 - L471, World Scientific Publishing Company (IF 0,696).

Atomic clocks are the core of a navigation system. Since an error in time results in an error in the user localization, it is fundamental that the stability is very high and constant with time. In this paper we discuss the dynamic Allan variance, or DAVAR, a representation of the time-varying stability of an atomic clock. We show by simulation its effectiveness in tracking common nonstationary behaviors of a clock.

A. Godone, F. Levi, S. Micalizio, E. Bertacco, C. E. Calosso
Frequency-stability performances of the pulsed optically pumped rubidium clock: recent results and future perspectives
IEEE Transactions on Instrumentation and Measurement, Vol. 56, no. 2, pp. 378-382, 2007 (IF 0,832).

This paper presents new results obtained with a laboratory prototype of a pulsed optically pumped (POP) frequency standard based on a vapor cell containing 87Rb diluted in a buffer gas. A frequency stability of about 1.2·10^-12 τ^-1/2 has been measured and the value of 3×10^-15 for integration times of 10⁵ s has been achieved (drift removed data). These performances show that a suitable implementation of this standard can lead to a compact vapor cell clock with a very interesting short and medium term frequency stability and consequently may be of great interest in radio-navigation systems. We also present some possible improvements of the pulsed technique.

R. Introzzi, M. Rajteri, G. Brida
Characterization of a cryogenic RF-preamplifier for superconducting photodetector readout
IEEE Transactions on Applied Superconductivity, Vol. 17, no. 2, pp. 383-386, 2007 (IF 1,551).

This work addresses the problem of designing superconducting photodetector readout circuits. A preliminary investigation of a selection of commercially available components to implement a radio-frequency, broadband, low-noise preamplifier operated in a cryogenic environment is presented. Wide band, high gain, low noise and stability under input mismatching load conditions have been the leading criteria taken into account to choose the devices. A set of Monolithic Microwave Integrated Circuits (MMIC) based on different technologies (GaAs, InP, HEMT, HBT) has been considered. The prototypes have been characterized at room temperature and low temperature by means of a cryocooler; their main parameters, gain and noise figure, have been measured.

S. Micalizio, A. Godone, F. Levi, J. Vanier
Spin-exchange frequency shift in alkali-metal-vapor cell frequency standards
Physical Review A, Vol. 73, pp. 033414, 2007 (IF 2,893).

In this paper we calculate the effect of spin exchange collisions in alkali metal vapors. In the framework of the high-energy approximation, we evaluate the spin exchange cross sections related to the line broadening and to the frequency shift of the ground state hyperfine transition. We do the calculation for the four isotopes, Na, K, Rb and Cs. The results are used in particular to evaluate the spin exchange frequency shift in Rb vapor cell frequency standards used in many applications. It turns out that, due to possible fluctuations in the atomic density, spin exchange may affect significantly the medium and long term frequency stability of the frequency standard.

E. Nunzi, L. Galleani, P. Tavella, P. Carbone
Detection of anomalies in the behavior of atomic clocks
IEEE Transactions on Instrumentation and Measurement, Vol. 56, no. 2, pp. 523-528, 2007 (IF 0,832).

In this paper, the problem of identifying variations in the nature of atomic clock noise is addressed. Two methods are proposed. One method is based on a generalized likelihood ratio test (GLRT), and the other is based on the dynamic Allan variance (DAVAR), which is a representation of the instantaneous clock stability that is able to point out possible nonstationary behaviors. Both methods efficiently track variations in the experimental clock data and, thus, appear as suitable tools for the detection of atomic clock anomalies.

E. Puddu, A. Andreoni, I.P. Degiovanni, M. Bondani, S. Castelletto
Ghost Imaging With Intense Fields From Chaotically-Seeded Parametric Down conversion
Optics Letters, Vol. 32, pp. 1132-1134, 2007 (IF 3,711).

We present the first experimental demonstration, to the best of our knowledge, of ghost imaging realized with intense beams generated by a parametric downconversion interaction seeded with pseudothermal light. As expected, the real image of the object is reconstructed satisfying the thin-lens equation. We show that the experimental visibility of the reconstructed image is in accordance with the theoretically expected one.

V. Schettini, S.V. Polyakov, I.P. Degiovanni, G. Brida, S. Castelletto, A.L. Migdall
Implementing a multiplexed system of detectors for higher photon counting rates
IEEE Journal of Selected Topics in Quantum Electronics, Vol. 123, no. 4, pp. 978-983, 2007 (IF 2,384).

Photon counting applications are typically limited by detector deadtime to operate at count rates of a few megahertz, at best, and often at significantly lower levels. This limitation is becoming more critical with the advance of photon counting applications such as photon-based quantum information. We present a first experimental proof of principle, and review the theoretical foundation of a multiplexed detection scheme that allows photons to be counted at higher rates than is possible with individual detectors or simple detector trees. In addition to this deadtime improvement, we discuss the impact of this scheme on other relevant characteristics such as afterpulsing and dark count rates.

J. Stalnaker, S.A. Diddmas, T. Fortier, K. Kim, L. Hollberg, J.C. Bergquist, W.M. Itano, M.J. Delaney, L. Lorini, W.H. Oskay, T.P. Heavner, S.R. Jefferts, F. Levi, T.E. Parker, J. Shirley
Optical-to-microwave frequency comparison with fractional uncertainty of 10^-15
Applied Physics B, Vol. 89, nos. 2-3, pp 167-176, 2007 (IF 2,280).

We report the technical aspects of the optical-to-microwave comparison for our recent measurements of the optical frequency of the mercury single-ion frequency standard in terms of the SI second as realized by the NIST-F1 cesium fountain clock. Over the course of six years, these measurements have resulted in a determination of the mercury single-ion frequency with a fractional uncertainty of less than 7×10^-16, making it the most accurately measured optical frequency to date. In this paper, we focus on the details of the comparison techniques used in the experiment and discuss the uncertainties associated with the optical-to-microwave synthesis based on a femtosecond laser frequency comb. We also present our most recent results in the context of the previous measurements of the mercury single-ion frequency and arrive at a final determination of the mercury single-ion optical frequency: f(Hg⁺) = 1 064 721 609 899 145.30(69) Hz.

I. Coddington, W.C. Swann, L. Lorini, J.C. Bergquist, Y. Le Coq, C.W. Oates, Q. Quraishi, K.S. Feder, J.W. Nicholson, P.S. Westbrook, S.A. Diddams, N.R. Newbury
Coherent optical link over hundreds of metres and hundreds of terahertz with subfemtosecond timing jitter
Nature photonics, Vol. I, pp. 283-287, 2007.

Recent developments in stabilized lasers have resulted in ultrastable optical oscillators with spectral purities below 1 Hz. These oscillators are not transportable at present and operate at a single frequency. To realize their full potential, a highly coherent, frequency-diverse fibre-optic network is needed to faithfully transfer the optical signals to remote sites and to different optical frequencies. Here we demonstrate such a coherent network composed of erbium fibre and Ti:sapphire laser-based, optical-frequency combs, stabilized optical-fibre links and cavity-stabilized lasers. We coherently transmit an optical carrier over 750 m of optical fibre with conversions to wavelengths of 657, 767, 1,126 and 1,535 nm, an overall timing jitter of 590 attoseconds, and a frequency instability of 12 mHz for the 195 THz carrier in 1 s and 250 mHz in 1,000 s. This first remote synchronization of two frequency combs also demonstrates a factor of 30 improvement in the relative stability of fibre frequency combs.

J. Hahn, D. Navarro-Reyes, R. Piriz, P. Tavella, V. Fernandez, M. Cueto, I. Sesia, F. Gonzalez, G. Cerretto, P. Waller, G. Mandorlo, D. Hannes, F. Droz, P. Rochat, J. Delporte, F. Mercier, M. Falcone, M. Gandara (GIOVE Mission Clock Experimentation Team)
Time for GIOVE-A. The Onboard Rubidium Clock Experiment
GPS World, Vol. 18, no. 5, pp. 64-69, 2007.

One candidate clock for the future Galileo satellites is the European Rubidium Atomic Frequency Standard. Two of these clocks are flying onboard the GIOVE-A test satellite which was launched on December 28, 2005. In this paper, the GIOVE clock experiment team discusses the tests which have been conducted to assess the performance of the satellite's active clock and their future plans for onboard clock assessment including the passive hydrogen maser to be flown on GIOVE--B.

Z. Ziyang, P. Tavella, W. Qing
Analysis of Frequency Stability and Type of Noise for Atomic Clocks in Galileo EPTS
Journal of Electronic Measurement and Instrument, Vol 21, no. 5, pp 35-39, 2007 (in Chinese).

The main characteristics of four atomic clocks in Galileo system Experimental Precise Timing Station (EPTS) are analyzed in this paper. Based on the signal model of atomic clock and the time domain measurement data from experiments, the frequency stabilities of all atomic clocks were calculated and analyzed using Allan variance at first. Applying Least Square algorithm, the linear fitting of short term and long term stability data in time domain was carried out. According to the slopes of fitting, the noise types affecting the atomic clocks in EPTS were identified. Experiment results show that the high short term stability Hydrogen Maser and three high long term stability Cesium atomic clocks fulfill the design requirements of generating Experimental Galileo System Time ( EGST) in the phase of Galileo System Test Bed V1 (GSTB2V1).

P. Iacomussi
Fascio piatto: un nuovo concetto di illuminazione stradale basato sulla sicurezza
Rivista Luce, pp.11-12, n.1, 2007 .

Come ben noto l'illuminazione stradale con impianti convenzionali è ottenuta con apparecchi posizionati ad una altezza variabile tra i 6 m e i 14 m, configurati in modo tale da sfruttare le proprietà di riflessione dell'asfalto onde assicurare la corretta luminanza del piano stradale. In alcuni casi è necessario, per ragioni di sicurezza, l'utilizzo di altezze di installazione decisamente inferiori. E' stato quindi studiato un metodo per illuminare intere carreggiate con apparecchi appositamente studiati per essere installati ad altezze ridotte e in grado di realizzare anche delle vere guide di luce.

P. Iacomussi
I LED per l'illuminazione: lo stato dell'arte
Rivista Luce, pp. 10-11, n. 2, 2007.

I LED sono ormai la soluzione riconosciuta per l'illuminazione di interni nell'immediato futuro. Lo sviluppo tecnologico attuale e le ricerche in corso si concentrano su quattro direzioni principali:

• l'aumento dell'efficienza luminosa;
• l'aumento della radiazione visibile prodotta;
• la riduzione delle tolleranze sulla variazione cromatica;
• l'aumento dell'indice di resa cromatica (per i soli led bianchi, ovviamente).

G. Rossi, P. Iacomussi
La normativa per l'illuminazione di esterni
Giornale dell'Architettura, Umberto Allemandi editore, 6pp., n. 56.

L'articolo prende in esame le numerose le normative afferenti al campo dell'illuminazione di esterni, soprattutto in virtù del carattere di sicurezza che questa tipologia di illuminazione riveste. Vengono presentati, in un numero speciale della rivista dedicato all'illuminazione, le normative nazionali, internazionali e i principali documenti CIE di riferimento.

Conference Proceedings

J. Achkar, P. Tuckey, P. Uhrich, D. Valat, A. Batchelor, G. Burden, A. Bauch, D. Piester, F. Cordara, P. Tavella, J. Davis, J. Delporte, R. Jones, T. Levin, G. Staton, J. Nawrocki, J.M. Piéplu
Fidelity - Progress Report on Delivering the Prototype Galileo Time Service Provider
Proceedings of EFTF '07 (European Frequency and Time Forum) and IEEE-FCS '07 (Frequency Control Symposium) - TimeNav '07, pp. 446-451, Geneva (Switzerland), May-June 2007 (cd rom).

The Fidelity consortium is currently implementing and will operate the Galileo Time Service Prototype Facility (GTSPF) in order to deliver Coordinated Universal Time (UTC) services to the Galileo satellite system during its In-Orbit Validation phase (due to begin in 2008). A key element of this plan is to integrate the Galileo timing activities into the wider time and frequency community, including the Bureau International des Poids et Mesures (BIPM). The main function of the GTSPF is to provide parameters for steering Galileo System Time (GST), as realized at the Galileo Precise Timing Facility (PTF), to UTC (modulo 1 s). This will be achieved in a three step process. First, the GST (as realized in the Galileo PTF from an ensemble of atomic clocks (active H-masers, high performance Caesium standards) with dedicated measurement equipment and clock ensemble algorithm) is compared against the participating UTC(k) time scales by Two-Way Satellite Time and Frequency Transfer (TWSTFT) and GPS P3 techniques. These raw data are sent to the GTSPF for processing. The Fidelity consortium is responsible for the calibration of the time transfer equipment. Second, the GTSPF generates a prediction of the difference UTC - GST (modulo 1 s) by means of an intermediate composite clock obtained from an ensemble of atomic standards maintained in the PTFs and in the participating European National Metrology Institutes (NMIs), and using the data of UTC - UTC(k) as computed by the BIPM. The benefits of the composite clock include enhanced stability and integrated integrity monitoring. Third, the GTSPF sends daily steering parameters to the PTF to be used to align the physical realization of GST against UTC (modulo 1 s) as required by the Galileo system specifications.

V. Andreoli, C. Gandini, A. Masoero, P. Mazzetti, E. Monticone, C. Portesi, M. Rajteri, A. Stepanescu
Analysis and Interpretation of Current Noise in High Tc Granular Superconductors during their Resistive Transition
19^th International Conference on Noise and Fluctuations; ICNF 2007, AIP Conference Proceedings, Vol. 922, pp. 223-228, 2007.

A brief review of the non stationary noise produced during the transition process of different types of superconducting materials is presented. Noise analysis evidence that very different mechanisms are at the base of the transition in monocrystalline, weak-link dominated or metallic-like granular high temperature superconductors. Models of the transition process which are in good agreement with the experimental results will be also given and discussed.

A. Andreoni, E. Puddu, I.P. Degiovanni, M. Bondani, S. Castelletto
Ghost imaging with intense entangled fields
Proceedings of SPIE 6710, 671003/1-8, 2007.

We implement a frequency degenerate seeded downconversion process in which the seed field is a spatially multimode chaotic field. The two output fields are quantum correlated in space and intensity and maintain the same spatial and temporal structure as the seeding field and thus represent two almost twin multimode fields that can be used for ghost imaging applications.

D. Calonico, F. Levi, L. Lorini, A. Godone, A. Cina, I.H. Bendea
High accuracy gravitational red-shift evaluation at INRIM
Proceedings of EFTF '07 (European Frequency and Time Forum) and IEEE-FCS '07 (Frequency Control Symposium) - TimeNav '07, pp. 62-66, Geneva (CH), May-Jun 2007 (cd rom).

The gravitational redshift is presently one of the main biases in the comparison of primary frequency standard, and it could be a challenge for the forthcoming generation of atomic optical clocks. In this paper we report the evaluation of the gravitational redshift with respect to the Geoid reference at INRIM laboratories, with an accuracy of 1×10^-17 in terms of relative frequency. The evaluation is based on GPS/levelling measurements and on the use of a local model for the Earth Geoid and its accuracy is limited by the reference potential of the Geoid.

L. Fellin, P. Iacomussi, G. Rossi, P. Soardo
Weight on sky luminance and the limiting magnitude of the sources around the site
Proceedings of XXVI CIE International Session, pp. D5-46-49, Beijing (China), July 2007.

The term "light pollution" refers normally to the increases of sky luminance and to the obstacles to astronomical observations and to the impairments on intrinsically dark sites, like national parks, due to the light emitted by road lighting installations. The paper describes an analysis method based on the measurement of the sky luminance, or of the limiting magnitude, over a site, on the installed luminous flux of the light sources (towns, villages, etc) surrounding the site, on their distances from the site and on some other environmental quantities which can be either measured or estimated on the ground of similar cases. For the calculations, the paper uses only the CIE sky glow formula for the evaluation of the reduction of the limiting magnitude and the Walker's law for the propagation of light pollution, i.e. two formulae which are accepted by both the astronomic and the lighting communities. An excel file is described which permits an easy evaluation of a site according to this method.

L. Fellin, P. Fiorentin, P. Iacomussi, G. Rossi, P. Soardo
Luminous emission of a town toward the sky: experimental results
Proceedings of International Symposium on Ligth Pollution and Urban Lighting, pp. 101-112, Istanbul (Turkey), September 2007.

The work is based on an extensive set of measurements of luminous emission of a town and on their correlation with the measured luminance of the sky. The case of town shield by mountains is analyzed; it allows the measurements are collected in well known conditions, reducing the disturbance of light sources other than the town under study. The measurements were correlated with the data on the lighting plant of town, showing the town behaves as a uniform emitter, with good approximation, when its contribution to the artificial luminance of the sky is considered.

T.M. Fortier, N. Ashby, J.C. Bergquist, M.J. Delaney, S.A. Diddams, T.P. Heavner, L. Hollberg, W.M. Itano, S.R. Jefferts, K. Kim, W.H. Oskay, T.E. Parker, J. Shirley, J.E. Stalnaker, F. Levi, L. Lorini
Improved Limits on Variation of the Fine Structure Constant and Violation of Local Position Invariance
Proceedings of EFTF '07 (European Frequency and Time Forum) and IEEE-FCS '07 (Frequency Control Symposium) - TimeNav '07, pp. 663-665, Geneva (Switzerland), May-June 2007 (cd rom).

We report tests of Local Position Invariance (LPI) and constancy of fundamental constants from measurements of the frequency ratio of the 282-nm ¹⁹⁹Hg⁺optical clock transition to the ground-state hyperfine splitting in ¹³³Cs. Analysis of the frequency ratio, extending over six years at NIST, is used to place a limit on the fractional variation of the two clocks of less than 5.8×10^-6 per change in normalized solar gravitational potential, and a limit on fractional variation of the fine structure constant at |α/α| < 1.3×10^-16 yr^-1, assuming invariance of other fundamental constants. Comparison of our results with those previously reported for the absolute optical frequency measurements of 171Yb+ versus other 133Cs standard yields a coupled constraint of -1.5×10^-15 <|α/α| <0.4×10^-15 yr^-1 and -2.7×10^-15 <d/DT [ln(µ_Cs/µ_B)] < 8.6×10^-15 yr^-1.

L. Galleani, P. Tavella
Characterization of nonstationary atomic clocks
Noise and Fluctuations in Photonics, Quantum Optics and Communications (edited by Leon Cohen), Proceedings of SPIE, Vol. 6603, 66030Z, Florence (Italy), May 2007.

Atomic clocks are ultra-precise time references, and because of this fact in the past 20 years they have found a fundamental application in navigation problems. The error in the localization of the user is highly dependent on the clock stability: variations of few nanoseconds in the clock phase result in an increase of the localization error by a factor of meters. Unfortunately atomic clocks are nonstationary, and their stability changes with time. We have recently proposed the DAVAR, or dynamic Allan variance, a representation of the instantaneous stability of an atomic clock. In this paper we will discuss the definition of the DAVAR and we will apply it to simulated nonstationary data, to prove its validity in clock noise characterization.

L. Galleani, P. Tavella
Interpretation of the dynamic Allan variance of nonstationary clock data
Proceedings of EFTF '07 (European Frequency and Time Forum) and IEEE-FCS '07 (Frequency Control Symposium) - TimeNav '07, pp. 992-997, Geneva (Switzerland), May-June 2007 (cd rom).

Atomic clocks are ultra-stable time references, and they have found fundamental applications in several fields, navigation being certainly one of the most successful. Unfortunately, atomic clocks may experience nonstationary behaviors which make their stability a function of time. Even when the change in stability is thought to be small, it can still force the system that uses the clock to fail the design requirements. In navigation systems this might turn into an unwanted degradation of the user localization error. It is therefore essential to monitor the stability of the clock, and to understand and interpret the possible nonstationary behaviors. To this aim, we have recently introduced the dynamic Allan variance, or DAVAR, a quantity that allows to represent the evolution with time of the clock stability. In this paper we show several cases of nonstationary time series, made by the combination of random processes and deterministic signals, and we discuss their dynamic Allan variance. The ultimate goal is to be able to do the inverse operation, that is to understand and classify the possible nonstationarities directly from the DAVAR representation. Examples with experimental data are presented.

M. Genovese, G. Brida, M. Gramegna, F. Piacentini, E. Predazzi. I. Ruo-Berchera
Experimental tests of hidden variable theories from dBB to stochastic electrodynamics
Journal of Physics: Conference Ser. 67, pp. 012047, 6 pp., 2007.

The studies concerning the possible existence of a deterministic theory, of which quantum mechanics would be an approximation, date to the celebrated 1935 Einstein-Podolsky-Rosen paper. Since Bell's proposal of 1964 various experiments were addressed to a general experimental test of local hidden variable theories, leading to strong indications favourable to Standard Quantum Mechanics. Nevertheless, detection loophole still persists. In this, after a short presentation of recent PDC photon experiments, we will present our recent works in this field and in particular a conclusive negative test of stochastic electrodynamics. Finally, we will also mention possible tests of non-local deterministic models and give some detail on our test of the dBB model.

M. Genovese, G. Brida, V. Caricato, M.V. Chekhova, M. Gramegna, L. Krivitsky, A. Meda, E. Predazzi, P. Traina
Bell states within the linewidth of SPDC and applications
Proceedings of SPIE 6710, 24, 2007.

In this paper we review our recent works on the generation of different Bell states within the lineshape of parametric down-conversion (SPDC) and their possible applications. Indeed, for polarization-entangled two-photon states produced via SPDC, the frequency-angular lineshape allowed by phase matching is considered. It is shown that there are always different Bell states generated for different mismatch values within the natural bandwidth. Consideration is made for two different methods of polarization entanglement preparation, based on type-II SPDC and on SPDC in two type-I crystals producing orthogonally polarized photon pairs. Different Bell states can be filtered out by either frequency selection or angular selection, or both. Our theoretical calculations are confirmed by a series of experiments, performed for the two above-mentioned ways of producing polarization-entangled photon pairs and with two kinds of measurements: frequency-selective and angular-selective. Finally, we mention possible application to quantum communication with fibers.

M. Gramegna, M. Genovese, G. Brida, A. Rossi, M. Paris
Technique for Photon Statistics Reconstruction by using On/Off detectors
Proceedings of Conference on Lasers and Electro-Optics/Quantum Electronics and Laser Science Conference and Photonic Applications Systems Technologies 2007 Technical Digest, QTuI5.

N. Guyennon, G. Cerretto, P. Tavella, F. Lahaye
Further Characterization of the Time Transfer Capabilities of Precise Point Positioning (PPP)
Proceedings of EFTF '07 (European Frequency and Time Forum) and IEEE-FCS '07 (Frequency Control Symposium) - TimeNav '07, pp. 399-404, Geneva (Switzerland), May-June 2007 (cd rom).

In recent years, many National Metrological Institutes (NMIs) have installed geodetic Global Positioning System (GPS) receivers together with their traditional GPS/GLONASS Common view (CV) receivers and Two Way Satellite Time and Frequency Transfer (TWSTFT)equipment. Many of these geodetic receivers operate within the International GNSS Service(IGS), are in continuous operation and their data are regularly processed by IGS Analysis Centers. From its global network of over 350 stations and its Analysis Centers, the IGS generates precise combined GPS products including precise ephemeredes and station and satellite clock time series referred to the IGS Time Scale. A method called Precise Point Positioning (PPP) is in use in the geodetic community allowing precise recovery of geodetic GPS receiver position, clock phase and tropospheric delay by taking advantage of the IGS precise products. The PPP method is attractive for time and frequency transfer applications due to its ease of use and low logistical requirements since data for a single station is processed. NRCan has developed a software implementing the PPP and a previous assessment of the PPP as Time Transfer method was carried out at INRiM (formerly IEN) in late 20031, showing better stability over short/medium term than the GPS CV and GPS P3 methods. Further analysis has been carried out in 20052 where, running continuously for periods of up two weeks, NRCan PPP software was able to reduce the artificial solution-boundary discontinuities, allowing then specific time-limited campaign (PTFs). In this paper, we report on follow-on work performed at INRIM and NRCan to further characterize the PPP method for time transfer application, involving the same NMIs (USNO,NIST PTB, NPL, OP, INRiM, NICT, NRC, ORB) considered in 2005. We try to take advantage of continuous PPP solution to build up a method to improve the continuity of solutions and characterize the impact of temperature hardware delays on the PPP clock solution. Data contributions of all NMIs and IGS quality products are kindly acknowledged.

J. Hahn, F. Gonzales, P. Waller, D. Navarro-Reyes, R. Piriz, V. Fernandez, P. Tavella, I. Sesia
GIOVE-A apparent clock assessment and results
Proceedings 39^th Precise Time and Time Interval (PTTI) meeting, Long Beach CA DC Nov 2007.

The performance of the Galileo space-borne clocks is of highest importance for navigation and integrity at the corresponding user level. Clock estimation and prediction errors driven by the onboard clock's frequency stability and drift are directly mapped into the User Equivalent Range Error (UERE), which has to be kept below its specified limits. The clock quality also affects the integrity performance of the Galileo system: clock "feared events" such as frequency and phase jumps have to be characterized and adequate barriers built against. In addition, the clocks operate in a rather harsh MEO-orbit radiation environment, and performance has to be guaranteed in all satellite mission phases including eclipses. Two Rubidium Atomic Frequency Standard (RAFS) units developed by Spectratime (former Temextime) were launched on the first experimental Galileo satellite, the Galileo In-Orbit Validation Element A (GIOVE-A). The RAFS already demonstrated excellent performance during on-ground qualification and acceptance tests. To verify its performance on-board, an experimentation was carried out as part of the GIOVE Mission Segment. Under this Mission, an infrastructure was deployed including a network of 13 Galileo Experimental Sensor Stations (GESS) monitoring continuously the GIOVE-A signals. Using dedicated network adjustment techniques, the processing of these observables allows the restitution of the phase difference between the on-board clock and a ground reference. Such restitution however is affected by the noise of the measurement system (e.g. on-board and averaged onground group delays, orbit residuals, etc), therefore the "apparent" clock denomination. This paper will present the GIOVE-A apparent clock results obtained since the ground infrastructure became operational for both the nominal and the redundant on-board clocks and for various signal configurations. These results will be complemented by relevant on-board Telemetry data. Finally, the assessment of the on-board clock performance will be discussed, together with the contribution of the measurement system noise.

W.M. Itano, J.C. Bergquist, A. Brusch, S.A. Diddams, T.M. Fortier, T.P. Heavner, L. Hollberg, D.B. Hume, S.R. Jefferts, L. Lorini, T.E. Parker, T. Rosenband, J.E. Stalnaker
Optical frequency standards based on mercury and aluminum ions
Proceedings of SPIE, Vol. 6673, 667303, 2007.

Single-trapped-ion frequency standards based on a 282 nm transition in ¹⁹⁹Hg⁺ and on a 267 nm transition in ²⁷Al⁺ have been developed at NIST over the past several years. Their frequencies are measured relative to each other and to the NIST primary frequency standard, the NIST-F1 cesium fountain, by means of a self-referenced femtosecond laser frequency comb. Both ion standards have demonstrated instabilities and inaccuracies of less than 1 × 10^-16.

N.R. Newbury, W.C. Swann, I. Coddington, L. Lorini, J.C. Bergquist, S.A. Diddams
Fiber laser-based frequency combs with high relative frequency stability
Proceedings of EFTF '07 (European Frequency and Time Forum) and IEEE-FCS '07 (Frequency Control Symposium) - TimeNav '07, pp. 980-983, Geneva (Switzerland), May-June 2007 (cd rom).

We describe our current low-noise fiber-laser frequency comb and present measurements of its residual instability. Through a comparison with a Ti:Sapphire frequency comb, we measure residual fractional frequency instabilities (Allan deviation) of ~6×10^-17 at 1 second and ~1.3×10^-18 at 1000 seconds. This stability demonstrates that the performance of a fiber frequency comb can rival that of current Ti:sapphire frequency combs.

G. Panfilo, T.E. Parker
A Theoretical Analysis of Frequency Uncertainty
Proceedings of EFTF '07 (European Frequency and Time Forum) and IEEE-FCS '07 (Frequency Control Symposium) - TimeNav '07, pp. 805-810, Geneva (Switzerland), May-June 2007 (cd rom).

In this work we present a preliminary study for the determination of the uncertainty on the frequency in the time measurements. The first part of this paper is dedicated to the theoretical study of the frequency uncertainty applying the law of the propagation of uncertainty and the spectral analysis approach. In the second part the theoretical results are compared with simulated results. In the final part we use real clock data and time transfer data to verify the analytical results.

G. Panfilo, P. Tavella
Algorithms for the Atomic clock prediction within the Galileo System
Proceedings 1^st colloquium on Scientific and Fund. Aspect of the Galileo Program, Toulouse, Sept 07.

Different clock prediction methods along with examples of application to the Galileo clocks are studied and presented pointing out the relationship with the clock model based on stochastic differential equations.

T.E. Parker, G. Panfilo
Experimental analysis of frequency transfer uncertainty
Proceedings of EFTF '07 (European Frequency and Time Forum) and IEEE-FCS '07 (Frequency Control Symposium) - TimeNav '07, pp. 986-991, Geneva (Switzerland), May-June 2007 (cd rom).

An experimental analysis of frequency transfer uncertainty is carried out. In situations where at least two transfer techniques are available a first difference statistic is used to determine the type and level of the transfer noise for transfer methods such as common-view GPS, carrier-phase GPS, and two-way time transfer. Frequency transfer uncertainties approaching 1×10^-16 at 30 days are possible. A method for estimating the frequency transfer uncertainty in situations where only one transfer technique is available is also examinated.

R. Piriz, V. Fernandez, M. Cueto, P. Tavella, I. Sesia, G. Cerretto, J. Hahn, D. Navarro-Reyes
Towards a Galileo Navigation Message
Proceedings of ENC-GNSS '07 (European Navigation Conference) - TimeNav '07, pp. 456-467, Geneva (Switzerland), May 2007 (cd rom).

The Galileo System Test Bed Version 2 (GSTB-V2) Mission Experimentation project is intended to mitigate the Galileo project risks by an early assessment of technical aspects like demonstration of the navigation service (including navigation message generation, uplink and broadcast), validation of critical in-orbit technology (clocks), end-to-end analysis of the Galileo Signal-In-Space, assessment of Galileo Test Receiver performance, validation of existing on-ground algorithm prototypes and testing of new ones (e.g. ionosphere and Differential Group Delay), and overall testing of timeliness and operational aspects. An additional mission goal is the implementation and evaluation of an experimental version of the so-called GPS to Galileo Time Offset (EGGTO), i.e. the predicted difference between the GPS and Galileo system times. This predicted offset will allow the user of a dual GPS/Galileo receiver to obtain a combined navigation solution from pseudorange measurements to the GPS and GIOVE satellites. This paper presents recent results from the GSTB-V2 experimentation project, and in particular the current status of the GTOVE-A navigation message.

R. Píriz, V. Fernández, G. Tobías, A. Mozo, P. Tavella, I. Sesia, G. Cerretto, R. Hernandez, J. Hahn
GGTO experimentation in the GIOVE mission
Proceedings 39^th Precise Time and Time Interval (PTTI) meeting, Long Beach CA DC Nov. 2007.

The future European radio navigation system Galileo will use its own timescale for the synchronization and dissemination of the predicted satellite clocks. Broadcast satellite clock predictions must be referred to a common and stable time reference in order for the user to be able to obtain an accurate positioning solution. The new Galileo timescale is called Galileo System Time (GST) and is the equivalent of the GPS Time (GPST) scale used in the Global Positioning System. For timing application both the GPS and Galileo systems broadcast as well the difference between their respective system times (GPST and GST) and the universal timescale (UTC), with a maximum deviation requirement of the order of 1 microsecond for GPS (although in practice the deviation is currently below 10 nanoseconds) and 50 nanoseconds for Galileo. Furthermore, for interoperability the Galileo and GPS systems are planned to transmit within their navigation messages the so-called GPS to Galileo Time Offset (GGTO), i.e. the predicted difference between the GPST and GST system times. This predicted offset will in principle allow the user of a dual GPS/Galileo receiver to obtain a combined navigation solution from pseudo-range measurements to the GPS and Galileo satellites. This paper analyses the different issues involved in GPS/Galileo interoperability for positioning and timing, including GGTO and timing biases, and presents practical experience and results related to E-GGTO, the GIOVE Mission experimental version of GGTO broadcast within the GIOVE navigation message.

G. Rossi, P. Iacomussi, A. Capuani, M. Castellano
The measurement of road marking with a mobile lab
Proceedings of XXVI CIE International Session, Beijing, 4-11 July 2007.

A system for measuring the photometric properties of horizontal road markings is described. Actually a prototype device for defining and optimizing design parameters and evaluating the measurement uncertainty is used in the 100 m long testing tunnel at I.N.Ri.M. in fixed positions or at very low moving speeds. A working device will be installed in Tiresia, a mobile lab for lighting plant characterization, in autumn next years.

G. Rossi, P. Iacomussi, M. Vio, F. Peron
A new instrument for Atmospheric turbidity evaluation
Proceedings of XXVI CIE International Session, Beijing, 4-11 July 2007.

The paper describes an instrument designed for measuring sky luminance, for evaluating sky meteorological conditions and daylight spectra. The instrument has a great measuring dynamics, does not need a solar tracking system, requires a simple calibration method and, if the measured range cover the visible spectra, it is relatively inexpensive: its cost is less then 10 000 euro. The instrument is now used to obtain local data need in simulation codes for atmospheric turbidity models. The main goal is to develop and validate, in the Italian climate, simplified models for spectral distribution of the daylight in local conditions. At the end of a preliminary measurement campaign, data obtained using more sophisticated instruments and published by the Aerosol Robotic Network (AERONET) will be compared with the results of this instrument.

M.L. Rastello
Classical and quantum techniques for photon metrology
Proceedings of the International School of Physics "Enrico Fermi", Course CLXVI "Metrology and Fundamental Constants", edited by T. Hänsch, S. Leschiutta, A.J. Wallard and M.L. Rastello, pp. 611-637, IOS Press 2007.

The quantum theory of electromagnetic radiation is reflected in the field of metrology by considering quantities related to the number of photons instead of conventional radiant quantities, intended in a Maxwellian frame. This paper is intended to introduce some basic methods for photon radiometry. First, classical standards are discussed for operation at optical power levels higher than some nanowatt, when detectors average on the incident radiation with a continuous quantity as an output. The way how to validate them is also discussed. Then, some fundamental concepts are introduced to bridge between classical radiometry and quantum photon radiometry. Finally, quantum photon techniques are introduced and their main characteristics are discussed, in particular the photon metrology with entangled photons.

M.L. Rastello
Surface Colour measurements by active vision systems
Proceedings of XXVI CIE International Session, pp. D2-50-53, Beijing (China), July 2007.

L. Sacerdote, P. Tavella
Role of noise in reliability problems: the view point of a mathematician and some application proposals
Noise and Fluctuations in Photonics, Quantum Optics and Communications (edited by Leon Cohen), Proceedings of SPIE, Vol. 6603, 66030Y, Florence (IT), May 2007.

Noise is generally considered a disturbance in understanding systems dynamics and large efforts are devoted to filter its presence in observed data. In many instances this work help the comprehension of involved phenomena but this cleaning can result in a distruction of important information. A set of examples, extracted from existing mathematical and applied literature, illustrate instances where the noise plays a positive role in determining the final dynamics of the system or allowing optimum values for signal detection. In this paper we will specifically focus on possible roles of noise when the underlining system presents non-linearities. Some of the discussed examples are toy examples useful to explain some unexpected result but we also consider the mathematical problem of determining the first passage times of stochastic processes through boundaries. These times have an immediate role in reliability theory, when alarms are tuned to prevent crashes. The fact that their behavior is highly determined by a positive role of the noise can suggest improvements for some measurement device.

I. Sesia, L. Galleani, P. Tavella
Implementation of the dynamic Allan variance for the Galileo System Test Bed V2
Proceedings of EFTF '07 (European Frequency and Time Forum) and IEEE-FCS '07 (Frequency Control Symposium) - TimeNav '07, pp. 946-949, Geneva (CH), May-June 2007 (cd rom).

The Dynamic Allan variance (DAVAR) method has been recently proposed as an extension of the classical Allan variance, with the aim of defining the instantaneous stability of an atomic clock. It is in fact known that atomic clocks may undergo sudden failures, are influenced by environmental factors, and they eventually age and stop working. Hence the stability of an atomic clock may vary with time, and in some demanding applications, such as Navigation Systems, a quick identification of clock failures is of the utmost importance. Working on the first preliminary data coming from the Galileo System Test Bed (GSTB) V2, some criticalities were encountered in the DAVAR evaluation and its graphical representation, when dealing with long periods of missing data. A new estimation method has been developed, allowing to evaluate the DAVAR in case of missing data, not equally spaced data and with large periods of missing observation. The new estimation method is presented here. The experimental results obtained by applying the improved DAVAR on the Galileo experimental satellite are also shown. Also experimental data obtained by using the Two-Way Satellite Time and Frequency Transfer (TWSTFT) method are analyzed and discussed.

P. Tavella, I. Sesia, G. Cerretto
Timing Activities at INRIM in the frame of the Galileo project
Proceedings 39^th Precise Time and Time Interval (PTTI) meeting, Long Beach CA DC Nov 2007.

Since 1999 different timing activities at the INRiM (formerly IEN G. Ferraris) are devoted to the development of the European Satellite Navigation System Galileo in collaboration with European space industries and the European Space Agency (ESA). Currently three main projects are in progress. In early 2006, an experimental phase called "Galileo System Test Bed V2 (GSTB V2)" has been launched supported by ESA and INRiM takes part to it hosting a Galileo prototype receiver connected to the time reference signals, and analyzing the data coming from the first experimental Galileo satellites in order to characterize the on board clocks. In addition INRiM is also involved in the Galileo development (phaseCDE1) supported by ESA by designing the time scale algorithm of one of the Galileo ground time laboratories named Precise Time Facility. A consortium of different industries and UTC(k) laboratories are developing the prototype of the Galileo Time Service Provider, supported by the European Union, with the aim to provide to the Galileo system the necessary corrections to maintain the Galileo system time in agreement with the UTC. INRiM contributes as one of the UTC(k) laboratories supporting also the algorithm, standardization and BIPM interface activities.

R. Zanello, M. Mascarello, P. Tavella, L. Galleani, E. Detoma, A. Bellotti
The Galileo Precise Timing Facility
Proceedings of EFTF '07 (European Frequency and Time Forum) and IEEE-FCS '07 (Frequency Control Symposium) - TimeNav '07, pp. 458-462, Geneva (CH), May-June 2007 (cd rom).

Consorzio Torino Time (CTT) is conducting the C/D/E1 phase for the implementation of the Precise Timing Facility (PTF) Element, part of the Galileo Mission Segment. The PTF is in charge to generate the Galileo System Time, the physical time reference of Galileo. The PTF detailed design phase is on-going, based on the experience acquired by CTT in the Galileo System Test Bed - V1 (GSTB-V1). The paper presents the PTF overview, its architecture and the design status of the software, algorithms and hardware.

C. Calosso, V. Pettiti, E. Bertacco, F. Cordara
TFTS - Campione per confronti interlaboratorio di frequenza ed intervallo di tempo
Atti del V Congresso Metrologia & Qualità, Torino, marzo 2007 (cd rom).

Questo articolo analizza lo studio e la realizzazione di un campione viaggiatore per confronti interlaboratorio nel settore della frequenza e dell'intervallo di tempo. Questo dispositivo può consentire, da parte del laboratorio di riferimento, la necessaria verifica periodica delle capacità metrologiche riconosciute ai centri di taratura del SIT.

F. Cordara, V. Pettiti
Le incertezze di misura (CMC) dell'INRIM nelle tarature di Tempo e Frequenza
Atti del V Congresso Metrologia & Qualità, Torino, marzo 2007 (cd rom).

In questo articolo si descrive il processo che ha portato alla stesura ed all'approvazione delle capacità di misura - Calibration Measurement Capabilities (CMC) - dei laboratori di riferimento europei per il tempo e la frequenza. In particolare si analizzano quelle riconosciute dal 2005 all'INRIM in questo settore, nell'ambito del Mutual Recognition Arrangement" (MRA) del CIPM (Comité International des Poids et Mesures).

L. Fellin, P. Fiorentin, P. Iacomussi, G. Rossi
Analisi del flusso luminoso emesso verso l'alto da una città
Atti del XXIV Congresso GMEE, pp. 293-294, Torino, settembre 2007.

Un modello che rappresenta l'emissione luminosa verso l'alto di una città permetterebbe di stimare il contributo di origine artificiale alla luminanza del cielo notturno, a partire dalla conoscenza del flusso luminoso installato per l'illuminazione esterna. Si presenta una metodologia per la valutazione sperimentale del contributo di una città alla luminanza del cielo. Sono inoltre riportati i risultati ottenuti applicando l'approccio descritto ad una città del nord Italia. Essi dimostrano la fondatezza delle ipotesi sulle quali si basa un modello a cavità, cioè che la luce emessa dagli apparecchi usati per 'illuminazione esterna è in gran parte sottoposta a riflessioni multiple prima di essere inviata verso il cielo.

A. Pesatori, V. Calabrese, M. Norgia, C. Svelto, G. Galzerano, E. Bava
Stabilizzazione di un laser a cavità estesa sulla riga di assorbimento dello ioduro d'idrogeno a 1.541 µm
Atti del XXIV Congresso GMEE, pp. 25-26, Torino, settembre 2007.

Books

Proceedings of the Advances in Foundations of Quantum Mecchanics and Quantum Information with Atoms and Photons
edited by M. Genovese, G. Brida, M.L. Rastello and A. Garuccio, World Scientific 2007, published as a special issue in the International Journal of Quantum Information (IJQI).

Technical Reports and Reports for Research Contracts

R. Costa, F. Cordara, V. Pettiti
Contributo del laboratorio di tempo e frequenza dell'INRIM al servizio Galileo Time Service Provider
Rapporto Tecnico INRIM n. 68, ottobre 2007.

Con questo rapporto si intende descrivere il servizio per il Time Service Provider (TSP), a cui il laboratorio di tempo e frequenza dell'INRIM contribuisce come uno dei laboratori di riferimento nell'ambito del consorzio Fidelity, per il progetto del sistema di navigazione satellitare europeo Galileo. L'INRIM ha partecipato alle precedenti fasi sperimentali di questo progetto, come il Galileo System Test Bed (GSTB) V1 e V2. Questa attività prevede la fornitura giornaliera di una serie di dati degli orologi atomici del laboratorio e dei sistemi di sincronizzazione satellitari GPS e a due vie (TWSTFT), elaborati e resi disponibili secondo un formato ed una cadenza stabilita. Infine vengono analizzati alcuni risultati generati dall'NPL e forniti dal Galileo Time Service Prototype Facility (GTSPF). Inoltre sono brevemente descritti i programmi utilizzati, per l'elaborazione dei diversi dati di misura sviluppati con compilatore Microsoft Visual Basic 5 in ambiente Windows, e per il trasferimento in remoto dei dati finali via File Transfer Protocol (FTP) sviluppato in ambiente Linux.

R. De Paoli
Acquisizione di pellicole cinematografiche a 4800 DPI e 48 bit/pixel mediante scanner piano e software per il taglio dei fotogrammi guidato dalle perforazioni
Rapporto Tecnico INRIM n. 79, novembre 2007.

R. De Paoli
Acquisizione digitale di immagini di piastrelle o tasselli di note proprietà densitometriche e colorimetriche utilizzando periferiche non calibrate
Rapporto Tecnico INRIM n. 80, dicembre 2007.

S. Micalizio, F. Levi
Feasibility study for POP atomic clock
ASI Contract, November 2007.

In this ASI contract, the task of INRIM was to design, implement and test a physics unit of POP maser. The goal was to demonstrate the feasibility of a laboratory prototype of maser based on the pulsed scheme and An overview of the activities we carried out at INRIM will be provide in this work.

P. Iacomussi, G. Rossi
The evaluation of uncertainty in spectral reflectance/transmittance factor measurement intercomparison
Rapporto Tecnico INRIM n. 60, giugno 2007.

The evaluation of measurement uncertainty is a normative requirement in all activities where measurements are considered and used to take decision. The International Commission on Glass, TC 10, organizes an intercomparison on spectral reflectance transmittance factors measurements. INRIM studied the methodologies for a fast and industrial reliable method for measurement uncertainty evaluation.