Precision a Measurement: Atom Recoil Method Review

1
Precision a Measurement Atom Recoil Method Review

• Victor Acosta
• Physics 250 Atomic Physics
• Prof. Dima Budker

2
Motivation

• a shows up all over in EM calcs
• Methods using g-2 involve lengthy QED equations
  which undergo frequent revision
• Working Toward an Electronic Kilogram

3
Electronic Kg

• Balance Gravity Force with EMF
• Find value for h, Plancks Constant
• Deduce me from

4
Physical Constant Uncertainties
5
Determining a

• Measuring R8
• Compare transition frequencies in Hydrogen using
  frequency chain or comb.
• de Beauvoir et. al. Eur Phys J D 2000, Udem et.
  al. 1997
• Measuring mp/me and MAtom/mp

6

• Penning Trap
• Hans Dehmelt, Nobel Prize 1989

Sub ppb UC for most mass ratios
7
Atom Recoil
10 kHz
So for ppb UC, we need µHz sensitivity!
8
Chu Atom Interferometer

• Use 4 p/2 Raman pulses
• Creates 2 Atom Interferometers
• Sensitivity Limited by Phase number of photon
  Recoils

9
Chus Clever Trick
Adding N (here N2) p-pulses allows for N times
greater recoil shift.
10
Results

• 7.7 ppb UC
• Problems
• Recoil Efficiency 94
• Allows other Zeeman sublevels to be populated
• Nrecoillt60

11
Clade Bloch Oscillations in Optical Lattice

1. Laser Cooling in a MOT down to 3 mK,
2. As in Chu expt, there is a p pulse pumping atoms
   of particular velocity class into F1,
3. Force N Bloch Oscillations using Optical Lattice
   to build up atom recoil momentum
4. Another p pulse tuned to F1 -gt F'2 to measure
   final velocity via TOF.

12
Bloch Oscillations Tilted Lattice

• Marble would fall (classically), but atom-waves
  oscillate!
• Periodicity of Bloch solutions requires the
  oscillations

13
Creating the Constant Force

• Could use gravity or E-field
• These are undesirable
• Solution Sweep the frequency of one of the
  lasers in the Standing Wave!
• Wave only stands in accelerated reference frame
• Think of nodes/antinodes moving accelerating down
  the line as the frequency is swept

14
Apparatus
15
Results

• 6.7 ppb (Chu 7.7 ppb)
• g-2 record is 3.9 ppb, Gabrielse et. al.
• Recoil Efficiency 99.7 (Chu 94)
• Nrecoil 900 (Chu 60)