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

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

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

Lorentz Invariance and the Standard Model Kostelecky and Mewes introduced a modification of QED (Phys. Rev .D, 66, 056005) 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

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

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

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, 056005 (2002) Latest modifications 2. Muller et al. Phys. Rev .Lett, 91, 020401 (2003) 3. J.A. Lipp Phys. Rev .Lett, 90, 060403 (2003) 4. Tobar, M., Wolf, P., Fowler, A., Hartnett, J. G. gr-qc/0408006 4 May 2006

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

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

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

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

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

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

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

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

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

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

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

Gravitational Frame Dragging 4 May 2006

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

4 May 2006