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Cryogenics is a pivotal aspect in the development of quantum technologies. Closed-cycle devices have recently emerged as an environmentally friendly and low-maintenance alternative to liquid helium cryostats. Yet the larger level of vibrations in dry cryocoolers forbids their use in most sensitive applications. In a recent work, we have proposed an inertial, broadband, contactless sensor based on the piezospectroscopic effect, i.e., the natural sensitivity of optical lines to strain exhibited by impurities in solids. This sensor builds on the exceptional spectroscopic properties of rare earth ions and operates below 4 K, where spectral hole burning considerably enhances the sensitivity. In this paper, we investigate the fundamental and technical limitations of this vibration sensor by comparing a rigid sample attachment to the cold stage of a pulse-tube cryocooler and a custom-designed exchange gas chamber for acoustic isolation. [ABSTRACT FROM AUTHOR]

In this paper we present a spectral analyzer for wideband RF signals with a spectral hole-burning-based architecture operating at telecom wavelength. This device is based on a codoped Er3 + :Sc3 + :Y2SiO5 crystal whose inhomogeneous linewidth allows for wideband operation. With time-resolved holeburning spectroscopy experiments we study the homogeneous linewidth and spectral diffusion in an unusual magnetic field configuration. We finally demonstrate the spectral analysis of RF signals with 28 GHz instantaneous bandwidth and MHz resolution. This work opens the way towards more complex architectures such as direction finding with wideband capacity. [ABSTRACT FROM AUTHOR]

Vibrations in cryocoolers are a recurrent concern to the end user. They appear in different parts of the acoustic spectrum depending on the refrigerator type, Gifford McMahon or pulse-tube, and with a variable coupling strength to the physical system under interest. Here, we use the piezospectroscopic effect in rare-earth doped crystals at a low temperature as a high resolution, contact-less probe for the vibrations. With this optical spectroscopic technique, we obtain and analyze the vibration spectrum up to 700 kHz of a 2 kW pulse-tube cooler. We attempt an absolute calibration based on known experimental parameters to make our method partially quantitative and to provide a possible comparison with other well-established techniques. [ABSTRACT FROM AUTHOR]

We report on the experimental demonstration of a multi-gigahertz bandwidth RF spectrum analyzer based on spectral hole burning in a 3 K-cooled rare-earth ion-doped crystal. We implemented the so-called “rainbow” architecture in which the optically carried spectral components of the incoming signal are angularly separated by the crystal, and are then acquired with a pixelated photo-detector. With this setup, we have been able to monitor and record the spectrum of complex microwave signals over an instantaneous bandwidth above 20 GHz, with a time resolution below 100 μs, 400 resolvable frequency components and a 100% probability of intercept. RF pulsed signals in the µs range are perfectly analyzed with this high time-resolved set-up. The best achievable sensitivity for pulsed signals is computed and compared with another spectral hole burning technique. [ABSTRACT FROM PUBLISHER]

Limits on the long-term stability and accuracy of a second generation cold atom gravimeter are investigated. We demonstrate a measurement protocol based on four interleaved measurement configurations, which allows rejection of most of the systematic effects, but not those related to Coriolis acceleration and wave-front distortions. Both are related to the transverse motion of the atomic cloud. Carrying out measurements with opposite orientations with respect to the Earth's rotation vector direction allows us to separate the effects and correct for the Coriolis shift. Finally, measurements at different atomic temperatures are presented and analyzed. In particular, we show the difficulty of extrapolating these measurements to zero temperature, which is required in order to correct for the bias due to wave-front distortions. [ABSTRACT FROM AUTHOR]

We report on the comparison between three absolute gravimeters that took place in April 2010 at the Laboratoire National de Métrologie et d'Essais. The three instruments (FG5#209 from METAS, Switzerland, IMGC-02 from INRIM, Italy, and CAG from LNE-SYRTE, France) rely on different methods: optical and atomic interferometry. We discuss their differences and their similarities. We compare their measurements of the gravitational acceleration in four points of the same pillar, in the perspective of absolute determination of g for a watt balance experiment. The three instruments performed repeatable g measurements but do not agree at the level aimed for. This work calls for additional studies on systematic effects. [ABSTRACT FROM AUTHOR]