Biomedical subjects

M Inguscio

Publications and source records attributed to M Inguscio.

At least 19 recordsLinked to original sources

PubMed2005

Effect of optical disorder and single defects on the expansion of a Bose-Einstein condensate in a one-dimensional waveguide.

We investigate the one-dimensional expansion of a Bose-Einstein condensate in an optical guide in the presence of a random potential created with optical speckles. With the speckle the expansion of the condensate is strongly inhibited. A detailed investigation has been carried out varying the experimental conditions and checking the expansion when a single optical defect is present. The experimental results are in good agreement with numerical calculations based on the Gross-Pitaevskii equation.

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PubMed2005

Sensitive measurement of forces at the micron scale using Bloch oscillations of ultracold atoms.

We show that Bloch oscillations of ultracold fermionic atoms in the periodic potential of an optical lattice can be used for a sensitive measurement of forces at the micrometer length scale, e.g., in the vicinity of a dielectric surface. In particular, the proposed approach allows us to perform a local and direct measurement of the Casimir-Polder force which is, for realistic experimental parameters, as large as 10(-4) gravity.

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PubMed2005

Upper limits on gravitational-wave emission in association with the 27 Dec 2004 giant flare of SGR1806-20.

At the time when the giant flare of SGR1806-20 occurred, the AURIGA "bar" gravitational-wave (GW) detector was on the air with a noise performance close to stationary Gaussian. This allows us to set relevant upper limits, at a number of frequencies in the vicinities of 900 Hz, on the amplitude of the damped GW wave trains, which, according to current models, could have been emitted, due to the excitation of normal modes of the star associated with the peak in x-ray luminosity.

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PubMed2005

Bose-Einstein condensate in a random potential.

An optical speckle potential is used to investigate the static and dynamic properties of a Bose-Einstein condensate in the presence of disorder. With small levels of disorder, stripes are observed in the expanded density profile and strong damping of dipole and quadrupole oscillations is seen. Uncorrelated frequency shifts of the two modes are measured and are explained using a sum-rules approach and by the numerical solution of the Gross-Pitaevskii equation.

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PubMed2004

Observation of dynamical instability for a Bose-Einstein condensate in a moving 1D optical lattice.

We have experimentally studied the unstable dynamics of a harmonically trapped Bose-Einstein condensate loaded into a 1D moving optical lattice. The lifetime of the condensate in such a potential exhibits a dramatic dependence on the quasimomentum state. This is unambiguously attributed to the onset of dynamical instability, after a comparison with the predictions of the Gross-Pitaevskii theory. Deeply in the unstable region we observe the rapid appearance of complex structures in the atomic density profile, as a consequence of the condensate phase uniformity breakdown.

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PubMed2004

Radio frequency selective addressing of localized atoms in a periodic potential.

We study the localization and addressability of ultracold atoms in a combined parabolic and periodic potential. Such a potential supports the existence of localized stationary states and we show that applying a radio frequency field allows us to selectively address atoms in these states. This method is used to measure the energy and momentum distribution of the atoms in the localized states. We also discuss possible extensions of this scheme to address and manipulate atoms in single lattice sites.

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PubMed2004

Insulating behavior of a trapped ideal Fermi gas.

We investigate theoretically and experimentally the center-of-mass motion of an ideal Fermi gas in a combined periodic and harmonic potential. We find a crossover from a conducting to an insulating regime as the Fermi energy moves from the first Bloch band into the band gap of the lattice. The conducting regime is characterized by an oscillation of the cloud about the potential minimum, while in the insulating case the center of mass remains on one side of the potential.

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PubMed2004

Atom interferometry with trapped fermi gases.

We realize an interferometer with an atomic Fermi gas trapped in an optical lattice under the influence of gravity. The single-particle interference between the eigenstates of the lattice results in macroscopic Bloch oscillations of the sample. The absence of interactions between fermions allows a time-resolved study of many periods of the oscillations, leading to a sensitive determination of the acceleration of gravity. The experiment proves the superiority of noninteracting fermions with respect to bosons for precision interferometry and offers a way for the measurement of forces with microscopic spatial resolution.

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PubMed2004

Collisionally induced transport in periodic potentials.

We study the transport of ultracold atoms in a tight optical lattice. For identical fermions the system is insulating under an external force while for bosonic atoms it is conducting. This reflects the different collisional properties of the particles and reveals the role of interparticle collisions in establishing a macroscopic transport in a perfectly periodic potential. Also in the case of fermions we can induce a transport by creating a collisional regime through the addition of bosons. We investigate the transport as a function of the collisional rate and observe a transition from a regime in which the mobility increases with increasing collisional rate to one in which it decreases. We compare our data with a theoretical model for electron transport in solids introduced by Esaki and Tsu.

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PubMed2004

Expansion of a Fermi gas interacting with a Bose-Einstein condensate.

We study the expansion of an atomic Fermi gas interacting attractively with a Bose-Einstein condensate. We observe a slower evolution of the radial-to-axial aspect ratio which reveals the importance of the mutual attraction between the two samples during the first phase of the expansion. For large atom numbers, we also observe a bimodal momentum distribution of the Fermi gas, which reflects the spatial distribution of the mixture in trap. This effect allows us to extract important information on the overlap of the two species across the collapse.

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PubMed2004

Absolute frequency measurements of the 2(3)S1-->2(3)P 0,1,2 atomic helium transitions around 1083 nm.

We measure the frequency of the 2(3)S1-->2(3)P(0,1,2) transitions of helium in a metastable beam using an optical frequency comb synthesizer. The relative uncertainty of these measurements ranging from 5x10(-11) to 7x10(-12) is, to our knowledge, the most precise result for any optical helium transition. Considering existing accurate values of the 2(3)P fine structure, we measure a centroid value of the 2(3)S-2(3)P frequency of 276 736 495 624.6(2.4) kHz, improving the previous interferometric measurement by 30 times. New accurate values of the 2(3)S-2(3)P and 2(3)P Lamb-shift energies are obtained.

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PubMed2003

Optically induced lensing effect on a Bose-Einstein condensate expanding in a moving lattice.

We report the experimental observation of a lensing effect on a Bose-Einstein condensate expanding in a moving 1D optical lattice. The effect of the periodic potential can be described by an effective mass dependent on the condensate quasimomentum. By changing the velocity of the atoms in the frame of the optical lattice, we induce a focusing of the condensate along the lattice direction. The experimental results are compared with the numerical predictions of an effective 1D theoretical model. In addition, a precise band spectroscopy of the system is carried out by looking at the real-space propagation of the atomic wave packet in the optical lattice.

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PubMed2003

Magnetic control of the interaction in ultracold K-Rb mixtures.

We predict the presence of several magnetic Feshbach resonances in selected Zeeman sublevels of the isotopic pairs 40K-87Rb and 41K-87Rb at magnetic fields up to 10(3) G. Positions and widths are determined combining a new measurement of the 40K-87Rb inelastic cross section with recent experimental results on both isotopes. The possibility of driving a K-Rb mixture from the weak to the strong interacting regime tuning the applied field should allow one to achieve the optimal conditions for boson-induced Cooper pairing in a multicomponent 40K-87Rb atomic gas and for the production of ultracold polar molecules.

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PubMed2003

Collective excitations of a trapped Bose-Einstein condensate in the presence of a 1D optical lattice.

We study low-lying collective modes of an elongated 87Rb condensate produced in a 3D magnetic harmonic trap with the addition of a 1D periodic potential which is provided by a laser standing wave along the axial direction. While the transverse breathing mode remains unperturbed, quadrupole and dipole oscillations along the optical lattice are strongly modified. Precise measurements of the collective mode frequencies at different heights of the optical barriers provide a stringent test of the theoretical model recently introduced [M. Krämer, Phys. Rev. Lett. 88, 180404 (2002)]].

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PubMed2002

Two atomic species superfluid.

We produce a quantum degenerate mixture composed by two Bose-Einstein condensates of different atomic species, 41K and 87Rb. We study the dynamics of the superfluid system in an elongated magnetic trap, where off-axis collisions between the two interacting condensates induce scissorlike oscillations.

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PubMed2002

Fermi-Bose quantum degenerate 40K-87Rb mixture with attractive interaction.

We report on the achievement of simultaneous quantum degeneracy in a mixed gas of fermionic 40K and bosonic 87Rb. Potassium is cooled to 0.3 times the Fermi temperature by means of an efficient thermalization with evaporatively cooled rubidium. Direct measurement of the collisional cross-section confirms a large interspecies attraction. This interaction is shown to affect the expansion of the Bose-Einstein condensate released from the magnetic trap, where it is immersed in the Fermi sea.

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PubMed2002

Collisional properties of ultracold K-Rb mixtures.

We determine the interspecies s-wave triplet scattering length a(3) for all K-Rb isotopic mixtures by measuring the elastic cross section for collisions between 41K and 87Rb in different temperature regimes. The positive value a(3)=+163(+57)(-12)a(0) ensures the stability against collapse of binary (41)K- (87)Rb Bose-Einstein condensates. For the fermion-boson mixture (40)K- (87)Rb, we obtain a large and negative scattering length which implies an efficient sympathetic cooling of the fermionic species down to the degenerate regime.

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PubMed2001

Expansion of a coherent array of Bose-Einstein condensates.

We investigate the properties of a coherent array containing about 200 Bose-Einstein condensates produced in a far detuned 1D optical lattice. The density profile of the gas, imaged after releasing the trap, provides information about the coherence of the ground-state wave function. The measured atomic distribution is characterized by interference peaks. The time evolution of the peaks, their relative population, as well as the radial size of the expanding cloud are in good agreement with the predictions of theory. The 2D nature of the trapped condensates and the conditions required to observe the effects of coherence are also discussed.

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