1. Precision Tests of Fundamental Physics
Group Members
The Micromaser
G. Wilkes
M. Jones
B. Sanguinetti
M. Everitt
H. Omer
Precision Tests
M. Blackman
J. Cotter
M. Hill
Project students
K. Vijiakuma
N. Fletcher
R. Lin
Postdoc
Dr. P. Blythe
Past Members
C. Moscrip
P. Batchelor
M. Grabbe
J. New
Dr. Lijun Li
Precision Tests of Fundamental Physics
Using Slow Light
Ben Varcoe
Quantum Information Group
University of Sussex
(University of Leeds)
4 May 2006

2. Overview Why Test Lorentz Invariance What might we see?
How are tests performed?
What could experiments show?
The “Slow Light” Interferometer
Slow Light
Tests of Lorentz Invariance
Future Directions
4 May 2006

3. Dark Matter (WIMPS, Axions?), Inflation (Dark Energy?)
Modern Physics
Nuclear
Physics
(QCD)
Particle
Physics
(Weak Force)
Light and Matter
(QED)
Gravity
(Gen. Relativity)
Standard
Model
T.O.E.
Quantum Gravity?
String Loop Theory?
String Theory?
Electro-weak
Hints…
Neutrino Mass,
Dark Matter (WIMPS, Axions?),
Inflation (Dark Energy?)
G.U.T.
Super-symmetry?
4 May 2006

4. Lorentz Invariance and the Standard Model
Kostelecky and Mewes introduced a modification of QED (Phys. Rev .D, 66, ) to account for potential violations…
QED
CPT-odd
CPT-even
The CPT–odd term leads to instabilities in the theory
Result: the coefficient, (kAF)k , must be zero
(i.e. any violation of Lorentz Invariance must be CPT even)
The CPT even term, (kF)klmn, is rather less well known
This coefficient contains 19 independent parameters in the photon sector of QED
10 parameters can be tested astronomically – leaving 9 that are most applicable to “bench top” tests
This extension has been added, to account for the possibility of Lorentz violating effects
The correct way to view this extension to the standard model is to see it as the remnant of a deeper Lorentz violating theory
This extension makes no assumptions about the nature of a Lorentz violating effect.
It allows for Lorentz violation to enter the theory in ways which may or may not impact on other areas
A highly sensitive measurement in one field may not necessarily rule out a Lorentz violating effect in another
c.f. Hidden variables and Bell states in quantum optics
Two possible methods of testing
Using astro-physical parameters
Using interferometric tests
4 May 2006

5. Lorentz Invariance and the Standard Model
The coefficient (kF)klmn, is conveniently parameterized by the coupling between E and B fields (Maxwell’s equations in a dielectric)
where
Which leads naturally to a new Lagrangian for the electromagnetic field
4 May 2006

6. Testing Lorentz Invariance
1. Michelson Interferometer: Fringe Shift Detection
Vframe
2. Cavity Based Experiments: Frequency Shift Detection
Spectrum
analysis
Michelson Interferometer
Beat Freq.
amplitude
Kennedy-Thorndike test
Atomic Sample
Spectrum
analysis
Beat Freq.
amplitude
Ives-Stillwell Measurement
Atomic Sample (n0)
Velocity (Vatom) na
na nb / n02 = 1 + e (Vatom) nb
k0+, ke-
k0+, ke-, ktr
Vatom=0.064c
4 May 2006

7. Current Experimental Tests1
Astrophysical Tests Laboratory Tests
Coeff.
no.
Velocity1
Polarisation1
Optical2,4
Microwave3
ke+ 5
10-16
10-32 -
ke-
10-15
(4 only)
ko+ 3
10-11
ko-
ktr 1
10-5 (guess)
1. Table from Kostelecky and Mewes Phys. Rev .D, 66, (2002)
Latest modifications
2. Muller et al. Phys. Rev .Lett, 91, (2003)
3. J.A. Lipp Phys. Rev .Lett, 90, (2003)
4. Tobar, M., Wolf, P., Fowler, A., Hartnett, J. G. gr-qc/
4 May 2006

8. The solar system has a velocity of nearly 400km/s relative to the CMB
Motion of The Earth
The large velocities are needed to provide a suitable platform for tests
2 days
1 year
The solar system has a velocity of nearly 400km/s relative to the CMB
4 May 2006

9. Detecting Lorentz Invariance (An Ives-Stillwell Experiment)
Leaves a
refractive index term
Atomic Sample (n0)
nb-dn
Three ways to proceed
Measure the “absolute shift”
Propotional to vatom (Very Hard)
Measure the “Fresnel drag” caused by motion through the medium
Proportional to v2atom and vmedium
Measure the relativistic change in density of the medium (relative shift)
Proportional to vatom and vmedium
na+dn
batom=Vatom/c
4 May 2006

10. Overview Experimental Tests of Lorentz Invariance Why test it?
How are tests performed?
What can they show?
The “Slow Light” Interferometer
Slow Light
A Slow Light Ives Stilwell Experiment
Future Directions
4 May 2006

11. Implementing Slow Light
Experimental Region
Strong
Drive Laser
Absorption
Rubidium - 87 gas cell
Refractive
Index
|3> W D
|1>
|2>
4 May 2006

12. Implementing Slow Light
Experimental Region
Strong
Drive Laser
Rubidium - 87 gas cell
Wave Plates
Polarising Beam Splitter
Weak
Probe Laser
|3> W W P D
|1>
|2>
Drive Laser
Probe Laser
4 May 2006

13. Preliminary Measurements
Frequency Scan by Zeeman shifting degenerate states
Oscillating
B-Field
300kHz
G. Jundt, G. T. Purves, C. S. Adams and I.G. Hughes Eur. Phys. J. D 27, 273 (2003)
|a> W W P D
|b>
|c>
4 May 2006

14. Preliminary Measurements
Long Coherence Times, More Atoms  Narrower Resonance
Group Velocity = 1/(1-ng) g
|a> W
|b>
gbc
Position measured with
5 Hz error
|c>
N – atomic density
l – wavelength
g – decay rate
DwD – Doppler width
4 May 2006

15. Current Sensitivity
We look for a 12Hr period in the frequency separation of peaks in the data
Measuring the maximum possible frequency splitting in the resonance we find a splitting of 11±51 Hz
4 May 2006

16. Future Direction… What can we achieve?
How do we increase the sensitivity of the apparatus?
Increase V
increases Doppler Shift
Decrease Linewidth
By increasing atomic density
Higher temperature or
Using a beam rather than a cell
Increase Laser Stability and Narrow Linewidth
increases resolution
What can we achieve?
4 May 2006

17. Gravitational Frame Dragging
The General Relativistic line element, in cylindrical coordinates for an infinitely long massive cylinder rotating with and angular frequency W is
The final term describes frame dragging induced by the motion which introduces a general rotation to the frame.
4 May 2006

18. Gravitational frame dragging
Rotating heavy object
Ion Source
Neutralisation
Acceleration
Potential
Atom Beam
Ives Stillwell Laser Excitation
780nm
776nm
5S1/2
5P3/2
5D5/2
770km/s
The motion generates a frequency difference
between the two beams of
4 May 2006

19. Gravitational Frame Dragging
4 May 2006

20. Summary
We have made one of the first direct tests of the refractive index of space
Our current measurement shows an “in principle” accuracy of a part in 1011
A 1000,000 fold improvement in sensitivity
Future directions include a laboratory scale measurement of gravitational frame dragging.
4 May 2006

21. 4 May 2006