arXiv subjects

V. Josse

Publications and source records attributed to V. Josse.

9 recordsLinked to original sources

arXiv2008

Guided atom laser : a new tool for guided atom optics

We present a guided atom laser. A Bose-Einstein condensate (BEC) is created in a crossed hybrid magnetic and an elongated optical trap, which acts as a matterwave guide. Atoms are extracted from the BEC by radio frequency (rf) outcoupling and then guided in the horizontal optical matterwave guide. This method allows to control the acceleration of the beam and to achieve large de Broglie wavelength. We also measure the longitudinal energy of the guided atom laser using atom optical elements based on a blue light barrier.

cond-mat.other↗

arXiv2006

Universal optical amplification without nonlinearity

We propose and experimentally realize a new scheme for universal phase-insensitive optical amplification. The presented scheme relies only on linear optics and homodyne detection, thus circumventing the need for nonlinear interaction between a pump field and the signal field. The amplifier demonstrates near optimal quantum noise limited performance for a wide range of amplification factors.

quant-ph↗

arXiv2006

Many-body quantum dynamics of polarisation squeezing in optical fibre

We report new experiments that test quantum dynamical predictions of polarization squeezing for ultrashort photonic pulses in a birefringent fibre, including all relevant dissipative effects. This exponentially complex many-body problem is solved by means of a stochastic phase-space method. The squeezing is calculated and compared to experimental data, resulting in excellent quantitative agreement. From the simulations, we identify the physical limits to quantum noise reduction in optical fibres. The research represents a significant experimental test of first-principles time-domain quantum dynamics in a one-dimensional interacting Bose gas coupled to dissipative reservoirs.

quant-ph↗

arXiv2005

Beam quality of a non-ideal atom laser

We study the propagation of a non-interacting atom laser distorted by the strong lensing effect of the Bose-Einstein Condensate (BEC) from which it is outcoupled. We observe a transverse structure containing caustics that vary with the density within the residing BEC. Using WKB approximation, Fresnel-Kirchhoff integral formalism and ABCD matrices, we are able to describe analytically the atom laser propagation. This allows us to characterize the quality of the non-ideal atom laser beam by a generalized M$^2$ factor defined in analogy to photon lasers. Finally we measure this quality factor for different lensing effects.

cond-mat.other↗

arXiv2004

Efficient polarization squeezing in optical fibers

We report on a novel and efficient source of polarization squeezing using a single pass through an optical fiber. Simply passing this Kerr squeezed beam through a carefully aligned lambda/2 waveplate and splitting it on a polarization beam splitter, we find polarization squeezing of up to 5.1 +/- 0.3 dB. The experimental setup allows for the direct measurement of the squeezing angle.

quant-ph↗

arXiv2003

Polarization squeezing in a four-level system

We present a theoretical study of an ensemble of X-like 4-level atoms placed in an optical cavity driven by a linearly polarized field. We show that the self-rotation (SR) process leads to polarization switching (PS). Below the PS threshold, both the mean field mode and the orthogonal vacuum mode are squeezed. We provide a simple analysis of the phenomena responsible for the squeezing and trace the origin of vacuum squeezing not to SR, but to crossed Kerr effect induced by the mean field. Last, we show that this vacuum squeezing can be interpreted as polarization squeezing.

quant-ph↗

arXiv2002

Atomic squeezing in a Lambda system

Using a quantum theory for an ensemble of three-level atoms (lambda) placed in an optical cavity abd driven by electromagnetic fields, we show that the long-lived spin associated with the ground state sublevels can be squeezed. Two kinds of squeezing are obtained: self-spin squeezing, when the input fields are coherent states and the atomic ensemble exhibit a large non-linearity; squeezing transfer, when one of the incoming fields is squeezed.

quant-ph↗

arXiv2002

Specular reflection of matter waves from a rough mirror

We have made a high resolution study of the specularity of the atomic reflection from an evanescent wave mirror using velocity selective Raman transitions. We have observed a double structure in the velocity distribution after reflection: a peak consistent with specular reflection and a diffuse reflection pedestal, whose contribution decreases rapidly with increasing detuning. The diffuse reflection is due to two distinct effects: spontaneous emission in the evanescent wave and a roughness in the evanescent wave potential whose amplitude is smaller than the de Broglie wavelength of the reflected atoms.

physics.atom-ph↗

arXiv2001

Understanding the production of dual BEC with sympathetic cooling

We show, both experimentally and theoretically, that sympathetic cooling of $^{87}$Rb atoms in the $|F=2,m_F=2>$ state by evaporatively cooled atoms in the $|F=1,m_F=-1>$ state can be precisely controlled to produce dual or single condensate in either state. We also study the thermalization rate between two species. Our model renders a quantitative account of the observed role of the overlap between the two clouds and points out that sympathetic cooling becomes inefficient when the masses are very different. Our calculation also yields an analytical expression of the thermalization rate for a single species.

quant-ph↗