M. G. Tarallo

Test of Einstein Equivalence Principle for 0-spin and half-integer-spin atoms: Search for spin-gravity coupling effects

We report on a conceptually new test of the equivalence principle performed by measuring the acceleration in Earths gravity field of two isotopes of strontium atoms, namely, the bosonic (88)Sr isotope which has no spin versus the fermionic (87)Sr isotope which has a half-integer spin. The effect of gravity on the two atomic species has been probed by means of a precision differential measurement of the Bloch frequency for the two atomic matter waves in a vertical optical lattice. We obtain the values η=(0.2±1.6)×10(-7) for the Eötvös parameter and k=(0.5±1.1)×10(-7) for the coupling between nuclear spin and gravity. This is the first reported experimental test of the equivalence principle for bosonic and fermionic particles and opens a new way to the search for the predicted spin-gravity coupling effects.

A simplified optical lattice clock

Existing optical lattice clocks demonstrate a high level of performance but they remain complex experimental devices. In order to address a wider range of applications including those requiring transportable devices, it will be necessary to simplify the laser systems and reduce the amount of support hardware. Here we demonstrate two significant steps towards this goal: demonstration of clock signals from a Sr lattice clock based solely on semiconductor laser technology, and a method for finding the clock transition (based on a coincidence in atomic wavelengths) that removes the need for extensive frequency metrology hardware. Moreover, the unexpected high contrast in the signal revealed evidence of density dependent collisions in 88Sr atoms.

Delocalization-enhanced Bloch oscillations and driven resonant tunneling in optical lattices for precision force measurements

In this paper, we describe and compare different methods used for the accurate determination of forces acting on matter-wave packets in optical lattices. The quantum interference nature responsible for the production of both Bloch oscillations and coherent delocalization is investigated in detail. We study conditions for the optimal detection of Bloch oscillation for a thermal ensemble of cold atoms with a large velocity spread. We report on the experimental observation of resonant tunneling in an amplitude-modulated optical lattice up to the sixth harmonic with Fourier-limited linewidth. We then explore the fundamental and technical phenomena which limit both the sensitivity and the final accuracy of the atomic force sensor at a

Prospect for a compact strontium optical lattice clock

{10}^{\ensuremath{-}7}

Strontium Optical Lattice Clock with All Semiconductor Sources

precision level [Poli et al., Phys. Rev. Lett. 106, 038501 (2011)], with an analysis of the coherence time of the system. We address a few simple setup changes to go beyond the current accuracy.

Coherent control of quantum transport: Modulation-enhanced phase detection and band spectroscopy

We report on our progress toward the realization of a compact optical frequency standard referenced to strontium intercombination lines. Our current setup allows the production of ultracold Sr atoms in hundreds of ms. For high resolution spectroscopy of the 1S0-3P0 doubly forbidden transition we have prepared a 698 nm clock laser stabilized on a high finesse, symmetrically suspended cavity and a high power 813 nm light source for the optical lattice trap at the magic wavelength. Due to their compactness, reliability, and low power consumption, semiconductor laser sources represent the best choice for the development of compact and transportable devices for application both on Earth and in Space. A new Sr trapping and cooling experimental setup is also presented.

Development of a transportable laser cooled strontium source for future applications in space

We report on our progress toward the realization of an optical frequency standard referenced to strontium intercombination lines. Our current setup allows the production of ultracold Sr atoms in hundreds of ms. For high resolution spectroscopy of 1S0-3P0 doubly forbidden transition we have also prepared a 698 nm clock laser stabilized on high finesse symmetrically suspended cavity and a high power 813 nm light source for the optical lattice trap at the magic wavelength. All the laser source employed are based on semiconductor device. This opens the way to the realization of compact, reliable and eventually transportable optical frequency standards.

Absolute frequency measurement of unstable lasers with optical frequency combs

Amplitude modulation of a tilted optical lattice can be used to steer the quantum transport of matter wave packets in a very flexible way. This allows the experimental study of the phase sensitivity in a multimode interferometer based on delocalization-enhanced Bloch oscillations and to probe the band structure modified by a constant force.

Optical lattice clock on bosonic Strontium atoms

We presented the first prototype of transportable laser-cooled strontium source. Novel design solutions have been discussed with a final volume, mass and power consumption budget for the atomic-package of 210 liters, 120 kg and 110 W, respectively. Most of the home made components have been assembled and tested. The system is currently under characterization and it is already able to produce a sample of about 108 atoms at 1 mK temperature. Next steps will be the integration of this system with a second stage cooling laser and with a transportable clock laser in order to realize a fully transportable optical lattice clock. Technical solutions, methods and know-how developed in this work will be used to built more robust, compact and advanced technology apparatus, with the nal aim to provide specifications for a future space optical lattice clock.

A strontium optical lattice clock apparatus for precise frequency metrology and beyond

Here we report on absolute frequency measurements of a commercial high power CW diode-pumped solid-state laser (Coherent Verdi-V5). This kind of lasers usually presents large frequency jitter (up to 50 MHz) both in the short term (1 ms time scale) and in the long term (>10 s time scale). A precise measurement of absolute frequency deviations in both temporal scales should require a set of different devices (optical cavities, optical wave-meters), each suited for measurements only at a specific integration time. Here we demonstrate how a frequency comb can be used to overcome this difficulty, allowing in a single step a full characterization of both short (<1 ms) and long term (> 103 s) absolute frequency jitter with a resolution better than 1 MHz. We demonstrate in this way the flexibility of optical frequency combs for absolute frequency measurements not only of ultra-stable lasers but also of relatively unstable lasers. The absolute frequency calibration of the Verdi laser that we have obtained have been used in order to improve the accuracy of the measurements of the local gravitational acceleration value with 88Sr atoms trapped in 1D vertical lattices.