High accuracy measure of atomic polarizability in an optical lattice clock

Despite being a canonical example of quantum mechanical perturbation theory, as well as one of the earliest observed spectroscopic shifts, the Stark effect contributes the largest source of uncertainty in a modern optical atomic clock through blackbody radiation. By employing an ultracold, trapped atomic ensemble and high stability optical clock, we characterize the quadratic Stark effect with unprecedented precision. We report the ytterbium optical clock's sensitivity to electric fields (such as blackbody radiation) as the differential static polarizability of the ground and excited clock levels: 36.2612(7) kHz (kV/cm)^{-2}. The clock's fractional uncertainty due to room temperature blackbody radiation is reduced an order of magnitude to 3 \times 10^{-17}.Comment: 5 pages, 3 figures, 2 table

Generation of an ultrastable 578 nm laser for Yb lattice clock

In this paper we described the development and the characterization of a 578 nm laser source to be the clock laser for an Ytterbium Lattice Optical clock. Two independent laser sources have been realized and the characterization of the stability with a beat note technique is presente

An atomic clock with 10−1810^{-18} instability

Atomic clocks have been transformational in science and technology, leading to innovations such as global positioning, advanced communications, and tests of fundamental constant variation. Next-generation optical atomic clocks can extend the capability of these timekeepers, where researchers have long aspired toward measurement precision at 1 part in $\bm{10^{18}}$. This milestone will enable a second revolution of new timing applications such as relativistic geodesy, enhanced Earth- and space-based navigation and telescopy, and new tests on physics beyond the Standard Model. Here, we describe the development and operation of two optical lattice clocks, both utilizing spin-polarized, ultracold atomic ytterbium. A measurement comparing these systems demonstrates an unprecedented atomic clock instability of $\bm{1.6\times 10^{-18}}$ after only $\bm{7}$ hours of averaging

Detailed X-ray spectroscopy of the magnetar 1E 2259+586

Magnetic field geometry is expected to play a fundamental role in magnetar activity. The discovery of a phase-variable absorption feature in the X-ray spectrum of SGR 0418+5729, interpreted as cyclotron resonant scattering, suggests the presence of very strong non-dipolar components in the magnetic fields of magnetars. We performed a deep XMM-Newton observation of pulsar 1E 2259+586, to search for spectral features due to intense local magnetic fields. In the phase-averaged X-ray spectrum, we found evidence for a broad absorption feature at very low energy (0.7 keV). If the feature is intrinsic to the source, it might be due to resonant scattering/absorption by protons close to star surface. The line energy implies a magnetic field of ~ 10^14 G, roughly similar to the spin-down measure, ~ 6x10^13 G. Examination of the X-ray phase-energy diagram shows evidence for a further absorption feature, the energy of which strongly depends on the rotational phase (E >~ 1 keV ). Unlike similar features detected in other magnetar sources, notably SGR 0418+5729, it is too shallow and limited to a small phase interval to be modeled with a narrow phase-variable cyclotron absorption line. A detailed phase-resolved spectral analysis reveals significant phase-dependent variability in the continuum, especially above 2 keV. We conclude that all the variability with phase in 1E 2259+586 can be attributed to changes in the continuum properties which appear consistent with the predictions of the Resonant Compton Scattering model

THE TALE OF THE TWO TAILS OF THE OLDISH PSR J2055+2539

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A Large Area Fiber Optic Gyroscope on multiplexed fiber network

We describe a fiber optical gyroscope based on the Sagnac effect realized on a multiplexed telecom fiber network. Our loop encloses an area of 20 km2 and coexists with Internet data traffic. This Sagnac interferometer achieves a sensitivity of about (10-8 rad/s)/sqrt(Hz), thus approaching ring laser gyroscopes without using narrow linewidth laser nor sophisticated optics. The proposed gyroscope is sensitive enough for seismic applications, opening new possibilities for this kind of optical fiber sensors

Robust optical frequency dissemination with a dual-polarization coherent receiver

Frequency dissemination over optical fiber links relies on measuring the phase of fiber-delivered lasers. Phase is extracted from optical beatnotes and the detection fails in case of beatnotes fading due to polarization changes, which strongly limit the reliability and robustness of the dissemination chain. We propose a new method that overcomes this issue, based on a dual-polarization coherent receiver and a dedicated signal processing that we developed on a field programmable gated array. Our method allowed analysis of polarization-induced phase noise from a theoretical and experimental point of view and endless tracking of the optical phase. This removes a major obstacle in the use of optical links for those physics experiments where long measurement times and high reliability are required

Realization of an Ultrastable 578-nm Laser for an Yb Lattice Clock

In this paper, we describe the development of an ultrastable laser source at 578 nm, realized using frequency sum generation. This source will be used to excite the clock transition 1S0-3P0 in an ytterbium optical lattice clock experiment. Two independent ultrastable lasers have been realized, and the laser frequency noise and stability have been characterize

On the puzzling high-energy pulsations of the energetic radio-quiet γ\gamma-ray pulsar J1813−-1246

We have analyzed the new deep {\it XMM-Newton} and {\it Chandra} observations of the energetic radio-quiet pulsar J1813$-$1246. The X-ray spectrum is non-thermal, very hard and absorbed. Based on spectral considerations, we propose that J1813 is located at a distance further than 2.5 kpc. J1813 is highly pulsed in the X-ray domain, with a light curve characterized by two sharp, asymmetrical peaks, separated by 0.5 in phase. We detected no significant X-ray spectral changes during the pulsar phase. We extended the available {\it Fermi} ephemeris to five years. We found two glitches. The $\gamma$-ray lightcurve is characterized by two peaks, separated by 0.5 in phase, with a bridge in between and no off-pulse emission. The spectrum shows clear evolution in phase, being softer at the peaks and hardenning towards the bridge. The X-ray peaks lag the $\gamma$-ray ones by 0.25 in phase. We found a hint of detection in the 30-500 keV band with {\it INTEGRAL} IBIS/ISGRI, that is consistent with the extrapolation of both the soft X-ray and $\gamma$-ray emission of J1813. The peculiar X and $\gamma$-ray phasing suggests a singular emission geometry. We discuss some possibilities within the current pulsar emission models. Finally, we develop an alternative geometrical model where the X-ray emission comes from polar cap pair cascades.Comment: 26 pages, 10 figures, 2 tables, submitted to Astrophysical Journa

Interval Sentinel Lymph Nodes: An Unusual Localization in Patients with Cutaneous Melanoma

Background. Recent studies have demonstrated that there exists a great variation in the lymphatic drainage in patients with malignant melanoma. Some patients have drainage to lymph nodes outside of conventional nodal basins. The lymph nodes that exist between a primary melanoma and its regional nodal basin are defined “interval nodes”. Interval node occurs in a small minority of patients with forearm melanoma. We report our experience of the Melanoma Unit of University Hospital Spedali Civili Brescia, Italy. Methods. Lymphatic mapping using cutaneous lymphoscintigraphy (LS) has become a standard preoperative diagnostic procedure to locate the sentinel lymph nodes (SLNs) in cutaneous melanoma. We used LS to identify sentinel lymph nodes biopsy (SLNB) in 480 patients. Results. From over 2100 patients affected by cutaneous melanoma, we identified 2 interval nodes in 480 patients with SLNB . The melanomas were both located in the left forearm. The interval nodes were also both located in the left arm. Conclusion. The combination of preoperative LS and intraoperative hand-held gamma detecting probe plays a remarkable role in identifying these uncommon lymph node locations. Knowledge of the unusual drainage patterns will help to ensure the accuracy and the completeness of sentinel nodes identification