arXiv subjects

Saïda Guellati-Khélifa

Publications and source records attributed to Saïda Guellati-Khélifa.

18 recordsLinked to original sources

arXiv2022

Quantum interference measurement of the free fall of anti-hydrogen

We analyze a quantum measurement designed to improve the accuracy for the free-fall acceleration of anti-hydrogen in the GBAR experiment. Including the effect of photo-detachment recoil in the analysis and developing a full quantum analysis of anti-matter wave propagation, we show that the accuracy is improved by approximately three orders of magnitude with respect to the classical timing technique planned for the current experiment.

quant-ph↗

arXiv2021

Improving the statistical analysis of anti-hydrogen free fall by using near edge events

An accurate evaluation of the gravity acceleration from the timing of free fall of anti-hydrogen atoms in the GBAR experiment requires to account for obstacles surrounding the anti-matter source. These obstacles reduce the number of useful events but may improve accuracy since the edges of the shadow of obstacles on the detection chamber depends on gravity, bringing additional information on the value of $g$. We perform Monte Carlo simulations to obtain the dispersion and give a qualitative understanding of the results by analysing the statistics of events close to an edge. We also study the effect of specular quantum reflections of anti-hydrogen on surfaces and show that they do not degrade the accuracy that much.

physics.atom-ph↗

arXiv2021

Analysis of the timing of freely falling antihydrogen

We evaluate the accuracy to be expected for the measurement of free fall acceleration of antihydrogen in the GBAR experiment, accounting for the recoil transferred in the photodetachment process. We show that the uncertainty on the measurement of gravity comes mainly from the initial velocity dispersion in the ion trap so that the photodetachment recoil is not the limiting factor to the precision as a naive analysis would suggest. This result will ease the constraints on the choice of the photodetachment laser parameters.

physics.atom-ph↗

arXiv2020

Velocity-dependent phase shift in a light-pulse atom interferometer

Atom interferometry relies on the separation and recombination of atom wavepackets. When the two paths overlap perfectly at the end of the interferometer, the phase is insensitive to the atomic velocity distribution. Here, we show that, when the separation and recombination is performed using a Raman transition there is a displacement of the atomic wavepacket due to a phase shift during light pulses. Because of the variation of the laser intensity seen by the atoms, there is an imperfect cancellation of these displacements. The observation of a velocity-dependent phase shift on the interferometer is the signature of this effect, which has been modeled. Thanks to the signature we have identified, we are able to compensate for this effect by applying laser power ramps during the interferometer to mitigate intensity variations.

physics.atom-ph↗

arXiv2018

Observation of Extra Photon Recoil in a Distorted Optical Field

Light carries momentum which induces on atoms a recoil for each photon absorbed. In vacuum, for a monochromatic beam of frequency $ν$, the global momentum per photon is bounded by general principles and is smaller than $h ν/c$ leading to a limit on the recoil. However, locally this limit can be broken. In this paper, we give a general formula to calculate the recoil in vacuum. We show that in a laser beam with a distorted optical field, there are regions where the recoil can be higher than this limit. Using atoms placed in those regions we are able to measure directly the extra recoil.

physics.atom-ph↗

arXiv2014

In-line extraction of an ultra-stable frequency signal over an optical fiber link

We demonstrate in-line extraction of an ultra-stable frequency signal over an optical link of 92-km of installed telecommunication fibers, following the proposition of G. Grosche in 2010. We show that the residual frequency noise at the extraction end is noticeably below that at the main link output when the extraction is near the input end, as expected from a simple model of the noise compensation. We obtain relative frequency instabilities, expressed as overlapping Allan deviation, of 8x10-16 at 1 s averaging time and a few 10-19 at 1 day. These results are at the state-of-the-art for a link using urban telecommunication fibers. We also propose an improved scheme which delivers an ultra-stable signal of higher power, in order to feed a secondary link. In-line extraction opens the way to a broad distribution of an ultra-stable frequency reference, enabling a wide range of applications beyond metrology.

physics.optics↗

arXiv2013

State of the art in the determination of the fine structure constant: test of Quantum Electrodynamics and determination of h/mu

The fine structure constant $α$ has a particular status in physics. Its precise determination is required to test the quantum electrodynamics (QED) theory. The constant $α$ is also a keystone for the determination of other fundamental physical constants, especially the ones involved in the framework of the future International System of units. This paper presents Paris experiment, where the fine structure constant is determined by measuring the recoil velocity of a rubidium atom when it absorbs a photon. The impact of the recent improvement of QED calculations of the electron moment anomaly and the recent measurement of the cesium atom recoil at Berkeley will be discussed. The opportunity to provide a precise value of the ratio $h/m_{\mathrm{u}}$ between the Planck constant and the atomic mass constant will be investigated.

quant-ph↗

arXiv2013

Compact atomic gravimeter based on a pulsed and accelerated optical lattice

We present a new scheme of compact atomic gravimeter based on atom interferometry. Atoms are maintained against gravity using a sequence of coherent accelerations performed by the Bloch oscillations technique. We demonstrate a sensitivity of 4.8$\times 10^{-8}$ with an integration time of 4 min. Combining this method with an atomic elevator allows to measure the local gravity at different positions in the vacuum chamber. This method can be of relevance to improve the measurement of the Newtonian gravitational constant $G$.

physics.atom-ph↗

arXiv2010

New determination of the fine structure constant and test of the quantum electrodynamics

We report a new measurement of the ratio $h/m_{\mathrm{Rb}}$ between the Planck constant and the mass of $^{87}\mathrm{Rb}$ atom. A new value of the fine structure constant is deduced, $α^{-1}=137.035\,999\,037\,(91)$ with a relative uncertainty of $6.6\times 10^{-10}$. Using this determination, we obtain a theoretical value of the electron anomaly $a_\mathrm{e}=0.001~159~652~181~13(84)$ which is in agreement with the experimental measurement of Gabrielse ($a_\mathrm{e}=0.001~159~652~180~73(28)$). The comparison of these values provides the most stringent test of the QED. Moreover, the precision is large enough to verify for the first time the muonic and hadronic contributions to this anomaly.

physics.atom-ph↗

arXiv2010

Theoretical Analysis of a Large Momentum Beamsplitter using Bloch Oscillations

In this paper, we present the implementation of Bloch oscillations in an atomic interferometer to increase the separation of the two interfering paths. A numerical model, in very good agreement with the experiment, is developed. The contrast of the interferometer and its sensitivity to phase fluctuations and to intensity fluctuations are also calculated. We demonstrate that the sensitivity to phase fluctuations can be significantly reduced by using a suitable arrangement of Bloch oscillations pulses.

physics.atom-ph↗

arXiv2009

Large Momentum Beamsplitter using Bloch Oscillations

The sensitivity of an inertial sensor based on an atomic interfermometer is proportional to the velocity separation of atoms in the two arms of the interferometer. In this paper we describe how Bloch oscillations can be used to increase this separation and to create a large momentum transfer (LMT) beamsplitter. We experimentally demonstrate a separation of 10 recoil velocities. Light shifts during the acceleration introduce phase fluctuations which can reduce the contrast of the interferometer. We precisely calculate this effect and demonstrate that it can be significantly reduced by using a suitable combination of LMT pulses. We finally show that this method seems to be very promising to realize LMT beamsplitter with several 10s of recoil and a very good efficiency.

physics.atom-ph↗

arXiv2008

Determination of the fine structure constant with atom interferometry and Bloch oscillations

We use Bloch oscillations to transfer coherently many photon momenta to atoms. Then we can measure accurately the recoil velocity $\hbar k/m$ and deduce the fine structure constant $α$. The velocity variation due to Bloch oscillations is measured using atom interferometry. This method yields to a value of the fine structure constant $α^{-1}= 137.035 999 45 (62)$ with a relative uncertainty of about $4.5 \times 10^{-9}$.

physics.atom-ph↗

arXiv2008

Combination of Bloch oscillations with a Ramsey-Bordé interferometer : new determination of the fine structure constant

We report a new experimental scheme which combines atom interferometry with Bloch oscillations to provide a new measurement of the ratio $h/m_{\mathrm{Rb}}$. By using Bloch oscillations, we impart to the atoms up to 1600 recoil momenta and thus we improve the accuracy on the recoil velocity measurement. The deduced value of $h/m_{\mathrm{Rb}}$ leads to a new determination of the fine structure constant $α^{-1}=137.035 999 45 (62)$ with a relative uncertainty of $4.6\times 10^{-9}$. The comparison of this result with the value deduced from the measurement of the electron anomaly provides the most stringent test of QED.

physics.atom-ph↗

arXiv2008

Precise determination of h/m_Rb using Bloch oscillations and atomic interferometry: a mean to deduce the fine structure constant

We use Bloch oscillations to transfer coherently many photon momenta to atoms. Then we can measure accurately the ratio h/m_Rb and deduce the fine structure constant alpha. The velocity variation due to the Bloch oscillations is measured thanks to Raman transitions. In a first experiment, two Raman $π$ pulses are used to select and measure a very narrow velocity class. This method yields to a value of the fine structure constant alpha^{-1}= 137.035 998 84 (91) with a relative uncertainty of about 6.6 ppb. More recently we use an atomic interferometer consisting in two pairs of pi/2 pulses. We present here the first results obtained with this method.

physics.atom-ph↗

arXiv2008

Atom interferometry based on light pulses : application to the high precision measurement of the ratio h/m and the determination of the fine structure constant

In this paper we present a short overview of atom interferometry based on light pulses. We discuss different implementations and their applications for high precision measurements. We will focus on the determination of the ratio h/m of the Planck constant to an atomic mass. The measurement of this quantity is performed by combining Bloch oscillations of atoms in a moving optical lattice with a Ramsey-Bordé interferometer.

physics.atom-ph↗

arXiv2005

A new determination of the fine structure constant based on Bloch oscillations of ultracold atoms in a vertical optical lattic

We report an accurate measurement of the recoil velocity of Rb atoms based on Bloch oscillations in a vertical accelerated optical lattice. We transfer about 900 recoil momenta with an efficiency of 99.97 % per recoil. A set of 72 measurements of the recoil velocity, each one with a relative uncertainty of about 33 ppb in 20 min integration time, leads to a determination of the fine structure constant alpha with a statistical relative uncertainty of 4.4 ppb. The detailed analysis of the different systematic errors yields to a relative uncertainty of 6.7 ppb. The deduced value of 1/alpha is 137.03599878(91).

physics.atom-ph↗

arXiv2005

A promising method for the measurement of the local acceleration of gravity using Bloch oscillations of ultracold atoms in a vertical standing wave

An obvious determination of the acceleration of gravity g can be deduced from the measurement of the velocity of falling atoms using a pi-pi pulses sequence of stimulated Raman transitions. By using a vertical standing wave to hold atoms against gravity, we expect to improve the relative accuracy by increasing the upholding time in the gravity field and to minimize the systematic errors induced by inhomogeneous fields, owing to the very small spatial amplitude of the atomic center-of-mass wavepacket periodic motion. We also propose to use such an experimental setup nearby a Watt balance. By exploiting the g/h (h is the Planck constant) dependence of the Bloch frequency, this should provide a way to link a macroscopic mass to an atomic mass.

physics.atom-ph↗

arXiv2005

Noise sensitivity of an atomic velocity sensor

We use Bloch oscillations to accelerate coherently Rubidium atoms. The variation of the velocity induced by this acceleration is an integer number times the recoil velocity due to the absorption of one photon. The measurement of the velocity variation is achieved using two velocity selective Raman pi-pulses: the first pulse transfers atoms from the hyperfine state 5S1/2 |F=2, mF=0> to 5S1/2, |F=1, mF = 0> into a narrow velocity class. After the acceleration of this selected atomic slice, we apply the second Raman pulse to bring the resonant atoms back to the initial state 5S1/2, |F=2, mF = 0>. The populations in (F=1 and F=2) are measured separately by using a one-dimensional time-of-flight technique. To plot the final velocity distribution we repeat this procedure by scanning the Raman beam frequency of the second pulse. This two pi-pulses system constitutes then a velocity sensor. Any noise in the relative phase shift of the Raman beams induces an error in the measured velocity. In this paper we present a theoretical and an experimental analysis of this velocity sensor, which take into account the phase fluctuations during the Raman pulses.

physics.atom-ph↗