arXiv subjects

G. Ferrari

Publications and source records attributed to G. Ferrari.

32 records · Page 2Linked to original sources

arXiv2008

Engineering the quantum transport of atomic wavefunctions over macroscopic distances

The manipulation of matterwave represents a milestone in the history of quantum mechanics. It was at the basis of its experimental validation through the observation of diffraction of matter on crystals, as well as grating and Young's double-slit interference with electrons, neutron, atoms and molecules. More recently matterwave manipulation has become a building block in the implementation of quantum devices such as quantum sensors and it plays an essential role in many proposals for implementing quantum computers. In this letter we coherently control the spatial extent of the wavefunction by reversibly stretching and shrinking the wavefunction over a millimeter distance. The remarkable experimental simplicity of the scheme would ease applications in the field of quantum transport and quantum computing.

quant-ph↗

arXiv2008

Formation Of A Cold Antihydrogen Beam in AEGIS For Gravity Measurements

The formation of the antihydrogen beam in the AEGIS experiment through the use of inhomogeneous electric fields is discussed and simulation results including the geometry of the apparatus and realistic hypothesis about the antihydrogen initial conditions are shown. The resulting velocity distribution matches the requirements of the gravity experiment. In particular it is shown that the inhomogeneous electric fields provide radial cooling of the beam during the acceleration.

physics.atom-ph↗

arXiv2008

Coherent Delocalization of Atomic Wave Packets in Driven Lattice Potentials

Atomic wave packets loaded into a phase-modulated vertical optical-lattice potential exhibit a coherent delocalization dynamics arising from intraband transitions among Wannier-Stark levels. Wannier-Stark intraband transitions are here observed by monitoring the in situ wave-packet extent. By varying the modulation frequency, we find resonances at integer multiples of the Bloch frequency. The resonances show a Fourier-limited width for interrogation times up to 2 s. This can also be used to determine the gravity acceleration with ppm resolution.

physics.atom-ph↗

arXiv2006

Laser cooling and trapping of atomic strontium for ultracold atom physics, high-precision spectroscopy and quantum sensors

This review describes the production of atomic strontium samples at ultra-low temperature and at high phase-space density, and their possible use for physical studies and applications. We describe the process of loading a magneto-optical trap from an atomic beam and preparing the sample for high precision measurements. Particular emphasis is given to the applications of ultracold Sr samples, spanning from optical frequency metrology to force sensing at micrometer scale.

physics.atom-ph↗

arXiv2006

Cooling and trapping of ultra-cold strontium isotopic mixtures

We present the simultaneous cooling and trapping of an isotopic mixture in a magneto-optical trap and we describe the transfer of the mixture into a conservative, far-off resonant dipole trap. The mixture is prepared with a new technique that applies to intermediate and heavy alkaline earth like atoms. In this work, 88Sr and 86Sr are simultaneously loaded first into the magneto-optical trap operated on the 1S0-3P1 spin-forbidden line at 689 nm, and then transferred into the dipole trap. We observe fast inter-species thermalization in the dipole trap which allows one to set a lower bound on the 88Sr-86Sr elastic cross section.

physics.atom-ph↗

arXiv2006

Long-lived Bloch oscillations with bosonic Sr atoms and application to gravity measurement at micrometer scale

We report on the observation of Bloch oscillations on the unprecedented time scale of severalseconds. The experiment is carried out with ultra-cold bosonic strontium-88 loaded into a vertical optical standing wave. The negligible atom-atom elastic cross section and the absence of spin makes $^{88}$Sr an almost ideal Bose gas insensitive to typical mechanisms of decoherence due to thermalization and to external stray fields. The small size enables precision measurements of forces at micrometer scale. This is a challenge in physics for studies of surfaces, Casimir effects, and searches for deviations from Newtonian gravity predicted by theories beyond the standard model.

physics.atom-ph↗

arXiv2006

Cooling of Sr to high phase-space density by laser and sympathetic cooling in isotopic mixtures

Based on an experimental study of two-body and three-body collisions in ultracold strontium samples, a novel optical-sympathetic cooling method in isotopic mixtures is demonstrated. Without evaporative cooling, a phase-space density of $6\times10^{-2}$ is obtained with a high spatial density that should allow to overcome the difficulties encountered so far to reach quantum degeneracy for Sr atoms.

physics.atom-ph↗

arXiv2005

Modelization of Thermal Fluctuations in G Protein-Coupled Receptors

We simulate the electrical properties of a device realized by a G protein coupled receptor (GPCR), embedded in its membrane and in contact with two metallic electrodes through which an external voltage is applied. To this purpose, recently, we have proposed a model based on a coarse graining description, which describes the protein as a network of elementary impedances. The network is built from the knowledge of the positions of the C-alpha atoms of the amino acids, which represent the nodes of the network. Since the elementary impedances are taken depending of the inter-nodes distance, the conformational change of the receptor induced by the capture of the ligand results in a variation of the network impedance. On the other hand, the fluctuations of the atomic positions due to thermal motion imply an impedance noise, whose level is crucial to the purpose of an electrical detection of the ligand capture by the GPCR. Here, in particular, we address this issue by presenting a computational study of the impedance noise due to thermal fluctuations of the atomic positions within a rhodopsin molecule. In our model, the C-alpha atoms are treated as independent, isotropic, harmonic oscillators, with amplitude depending on the temperature and on the position within the protein (alpha-helix or loop). The relative fluctuation of the impedance is then calculated for different temperatures.

q-bio.QM↗

arXiv2004

Shot Noise in Linear Macroscopic Resistors

We report on a direct experimental evidence of shot noise in a linear macroscopic resistor. The origin of the shot noise comes from the fluctuation of the total number of charge carriers inside the resistor associated with their diffusive motion under the condition that the dielectric relaxation time becomes longer than the dynamic transit time. Present results show that neither potential barriers nor the absence of inelastic scattering are necessary to observe shot noise in electronic devices.

cond-mat.mtrl-sci↗

arXiv2003

Precision frequency measurement of visible intercombination lines of strontium

We report the direct frequency measurement of the visible 5s$^2$ $^1$S$_0$-5s 5p$^3$P$_1$ intercombination line of strontium that is considered a possible candidate for a future optical frequency standard. The frequency of a cavity-stabilized laser is locked to the saturated fluorescence in a thermal Sr atomic beam and is measured with an optical-frequency comb-generator referenced to the SI second through a GPS signal. The $^{88}$Sr transition is measured to be at 434 829 121 311 (10) kHz. We measure also the $^{88}$Sr-$^{86}$Sr isotope shift to be 163 817.4 (0.2) kHz.

physics.atom-ph↗

arXiv2003

Collisional properties of ultracold K-Rb mixtures

We determine the inter-species s-wave triplet scattering length a3 for all K-Rb isotopic mixtures by measuring the cross-section for collisions between 41K and 87Rb in different temperature regimes. The positive value a3=+163(+57,-12)a0 ensures the stability of binary 41K-87Rb Bose-Einstein condensates. For the fermion-boson mixture 40K-87Rb we obtain a large and negative scattering length which implies an efficient sympathetic cooling of the fermionic species down to the degenerate regime.

cond-mat.soft↗

arXiv2002

Formation of a Matter-Wave Bright Soliton

We report the production of matter-wave solitons in an ultracold lithium 7 gas. The effective interaction between atoms in a Bose-Einstein condensate is tuned with a Feshbach resonance from repulsive to attractive before release in a one-dimensional optical waveguide. Propagation of the soliton without dispersion over a macroscopic distance of 1.1 mm is observed. A simple theoretical model explains the stability region of the soliton. These matter-wave solitons open fascinating possibilities for future applications in coherent atom optics, atom interferometry and atom transport.

cond-mat↗

arXiv2001

A quasi-pure Bose-Einstein condensate immersed in a Fermi sea

We report the observation of co-existing Bose-Einstein condensate and Fermi gas in a magnetic trap. With a very small fraction of thermal atoms, the 7Li condensate is quasi-pure and in thermal contact with a 6Li Fermi gas. The lowest common temperature is 0.28 muK = 0.2(1) T_C = 0.2(1) T_F where T_C is the BEC critical temperature and T_F the Fermi temperature. Behaving as an ideal gas in the radial trap dimension, the condensate is one-dimensional.

cond-mat.stat-mech↗

arXiv2000

Sympathetic cooling of bosonic and fermionic Lithium gases towards quantum degeneracy

Sympathetic cooling of two atomic isotopes is experimentally investigated. Using forced evaporation of a bosonic 7Li gas in a magnetic trap, a sample of 3 10^5 6Li fermions has been sympathetically cooled to 9(3)muK, corresponding to 2.2(0.8) times the Fermi temperature. The measured rate constant for 2-body inelastic collisions of 7Li |2,2> state at low magnetic field is 1.0^{+0.8}_{-0.5} 10^-14 cm^3s^-1.

cond-mat↗