Measurement of the recoil velocity by atom interferometry
Measurement of the recoil velocity by atom interferometry Permanent staff: Pierre Cladé François Biraben Saïda Guellati-Khelifa François Nez Lucile Julien Catherine Schwob Benoît Grémeau Post-docs: Satya Bade June Sun Ph. D students: L. Morel M. Andia R. Jannin C. Courvoisier R. Bouchendira M. Cadoret P. Cladé R. Battesti
The metrology Group of the LKB: 1983. . . The group was founded François Biraben (F 1) and Lucile Julien with the scientific support of Bernard Cagnac • In 1983, F 1 decided to use the tunable cw monomode laser he had himself developed to excite two-photon transitions in atomic hydrogen • The goal was the determination of the Rydberg constant from the measurement of 2 S – n. S and 2 S-n. D hydrogen transitions. F 1: Very good expertise in high-resolution spectroscopy, (twophoton transitions in sodium and rare gas atoms). Lucile: had previously measured atomic structures and Lamb shifts in excited hydrogen states by an anticrossing method
Over more than 30 years of high precision spectroscoy of simple atomic systems E 0 exact Proton radius puzzle • • • p m- H/D spectroscopy + QED µp spectroscopy + QED 2 S Corrections QED (1/n 3), Correction relativiste rayon de charge du proton (1/n 3), electron-proton scattering reanalysis 4 S 3 S 243 nm 205 nm 1 S 0, 879 (11) fm 0. 8760 (78) fm 194 nm p e- 0. 84087 (37) fm fm Nature 466, 213 (2010), Science 339, 417 (2013), Science 353, 669 (2016) Accurate determinations of fundamental physical constants: Rydberg constant R∞, proton radius r. P and fine structure constant for testing the quantum electrodynamics and the Standard Model
Over more than 30 years, Biraben’s group • Laser technology (frequency control techniques. . . ) • Developement of methods for absolute measurement of optical frequencies The hidden force of the team is the collaboration with LNE-SYRTE • 1993, the first absolute frequency measurement of hydrogen transitions using two frequency standards: the I 2 -stabilized He–Ne laser at 473 THz (633 nm) and the CH 4 -stabilized He-Ne laser at 88 THz (3. 39 μ m) : Determination of the Rydberg Constant with an uncertainty of 2. 2 x 10 -11. • In 1994, the first optical fiber link between two laboratories (in the world) placed underground between LKB and the LPTF (LNE-SYRTE). • Two-photon Rubidium frequency standard, measurement of the 2 S– 8 S/8 D hydrogen transitions • Now, an optical frequency comb referenced to the Cs clock of the LNE-SYRTE laboratory.
h/m project: 1998. . .
Determinations of a: state of art in 1998 -2002 Electron magnetic-moment anomaly measurement and QED calculations Electrical measurements Transition frequencies measurement Muonium ground-state hyperfine splitting quantum Hall effect 2 e/h Josephson effect RK =h/e 2=µ 0 c/2 a muonium s. h. f Codata 98 Codata 02 h/M 10 -7 137, 035 990 g – 2 of the electron Solid-state physics QED ae = f (a/p) h / M(neutron) Mv=h/l atomic interferometry h / M(Cs) 137, 036 000 137, 036 010 a-1
S. Chu experiment (1992) Atomic interferometer and a succession of N p-Raman pulses Uncertainty on a of 10 -7, with Np=20 D. S. Weiss et al. , Phys. Rev. Lett. 70, 2706 (1993)
Coherent acceleration of atoms in accelerated optical lattice by transferring a large number of photon momenta first Brillouin zone
Proposal of the experiment
First experimental configuration Bloch oscillations in vertical standing wave E n m -ħk + ħk p The originality of our approach in comparison to Chu’s experiment: • Acceleration of atoms with B. O instead a succession of p-Raman transitions • Velocity sensor based on two p-Raman pulses instead atomic interferometer ( too sensitive to parasitic and incontrollable phase shifts)
ICAP, in Firenze, 2000 They really believe they could compete with S. Chu's group Very interesting !! ?
Measurement of the local acceleration of gravity P. Cladé et al. , Europhys. Lett. , 71, 730 -736 (2005) Uncertainty on g of 10 -6, losses due to collisions with residual gas and later limited by the transverse expansion of the atomic cloud
Detailled study of systematic effects
We started doing atomic interferometry in 2006 M. Cadoret et al. , Phys. Rev. Lett 101, 230801 (2008) Demonstration of atomic elevator based on B. O
The comparison with the g-2 value provides the most stringent test of the QED. The precision was large enough to verify for the first time the muonic and hadronic contributions to this anomaly.
Recoil velocity of atom in a distorted wavefront New laser system (11 W @ 780 nm for Bloch laser) : larger waist Ø Statistical uncertainty on h/m of 2 x 10 -10 Ø New systematic effect that depends on the intensity of the laser used for coherent acceleration
Recoil velocity of atom in a distorted wavefront § Quality of optics: atoms experiment distorted Optical Field Local amplitude fluctuations induce momentum corrections (in paraxial approximation): where If the probability P(I) to transfer light momentum to the atoms depends on the intensity, the average correction is: For BOs, the probability P(I) is governed by the Landau-Zener losses.
Recoil velocity of atom in a distorted wave front S. Bade et al. , Phys. Rev. Lett. 121, 073603 (2018)
Recent measurement h/m. Cs from Berkeley group Parker et al. , Science 360, 191– 195 (2018) most accurate measurement of the fine-structure constant to date, shifted by 2. 5 s from the g-2 value
New experimental setup
Typical spectra (5 min integration time)
Statistical uncertainty 5 times better than the Berkeley group measurement
Study of systematic effects in progress ! Systematic effects Beams alignment Second order Zeeman effect Gravity gradient Coriolis acceleration Phase shift in RF chains Wavefront curvature and Gouy phase Wavefront distortions Phase shifts during Raman transitions
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