Cavity Control in a Single-Electron Quantum Cyclotron

Transcription

1 Cavity Control in a Single-Electron Quantum Cyclotron An Improved Measurement of the Electron Magnetic Moment David Hanneke Michelson Postdoctoral Prize Lectures 13 May 2010

2 The Quantum Cyclotron Single electron Resolve lowest cyclotron and spin states via QND measurement

3 Acknowledgements Principal Investigator Gerald Gabrielse Postdocs Maarten Jansen Kamal Abdullah 20 years Graduate Students Josh Dorr Shannon Fogwell David Hanneke (2007) Brian Odom (2004) Brian D Urso (2003) Steve Peil (1999) Daphna Enzer (1996) Ching-hua Tseng (1995) Joseph Tan (1992) 7 theses

4 Outline I. Introduction II. Measurement overview III. Novel techniques IV. Measurement details V. Uncertainties VI. Experimental challenges VII.What s next

5 Magnetic Moments Orbital angular momentum Intrinsic angular momentum (Dirac point particle) Structure of the vacuum (QED) Structure of the particle (proton) g =

6 , g, and QED

7 Exact Values for C i 1 Feynman diagram 7 diagrams 72 diagrams C 8 has 891 diagrams Known to 0.2 % numerically Exact calculation underway C 10 has diagrams Numeric calculation just beginning Largest uncertainty in! J. Schwinger, Phys. Rev. 73, 416 (1948) C.M. Sommerfield, Phys. Rev. 107, 328 (1957) S. Laporta and E. Remiddi, Phys. Lett. B 379, 283 (1996) T. Kinoshita and M. Nio, Phys. Rev. D 73, (2006) T. Kinoshita and M. Nio, Phys. Rev. D 73, (2006) T. Aoyama et al, Phys. Rev. Lett (2007)

8 Measurement Results g/2 = (28) [0.28 ppt] -1 = (51) [0.37 ppb] D. Hanneke, S. Fogwell, and G. Gabrielse, Phys. Rev. Lett. 100, (2008) B. Odom, D. Hanneke, B. D Urso, and G. Gabrielse, Phys. Rev. Lett. 97, (2006) G. Gabrielse, D. Hanneke, T. Kinoshita, M. Nio, and B. Odom, Phys. Rev. Lett. 97, (2006). Ibid (E) (2007)

9 Outline I. Introduction II. Measurement overview III. Novel techniques IV. Measurement details V. Uncertainties VI. Experimental challenges VII.What s next

10 Experimenter s g g in free-space (with a magnetic field) What should we measure? Frequency! B

11 Experimenter s g Special Relativistic corrections The cyclotron is an anharmonic oscillator. No relativistic correction to a.

12 Experimenter s g Penning Trap s electrostatic quadrupole

13 Experimenter s g A real Penning trap has distortions in the electrostatic quadrupole misalignment of the quadrupole axis and B Brown-Gabrielse Invariance Theorem L.S. Brown and G. Gabrielse, Rev. Mod. Phys. 58, 233 (1986) required hierarchy cavity shift

14 Our Trap Frequencies B ~ 5.36 T V 0 ~ V d ~ 3.5 mm (0.14 in) motion frequency damping time axial 200 MHz 0.2 s cyclotron GHz 5 s spin GHz 2 yr magnetron 133 khz 4 Gyr hierarchy satisfied ~ 180 Hz

15 Our Trap

16 The Whole Apparatus

17 A Tabletop Experiment

18 Outline I. Introduction II. Measurement overview III. Novel techniques IV. Measurement details V. Uncertainties VI. Experimental challenges VII.What s next

19 Low Temperatures Cool the blackbody photons ( n << 1) Allows quantum jump spectroscopy S.Peil and G.Gabrielse, Phys. Rev. Lett. 83, 1287 (1999)

20 Low Temperatures Exact relativistic shifts

21 Low Temperatures Narrow line widths

22 Cavity Control The radiation modes of a cylindrical cavity are Well understood Resonant near c = 150 GHz ( ~ 2 mm) Coupled to the cyclotron motion if the geometry is right TE GHz J.D. Jackson, Classical Electrodynamics, 3 rd Ed., Sect. 8.7 L.S. Brown et al., Phys. Rev. A 32, 3204 (1985)

23 Cavity Control Control the cyclotron damping rate, c Inhibited spontaneous emission Free space damping rate ~1/(100 ms) = (6.70 ± 0.18) s = 73.6 x free space

24 Cavity Control Shift the cyclotron frequency Details later

25 Outline I. Introduction II. Measurement overview III. Novel techniques IV. Measurement details V. Uncertainties VI. Experimental challenges VII.What s next

26 Determining g Measure f c, a, z Calculate Calculate /

27 Axial Detection

28 Self Excited Oscillator First single-particle SEO Enhanced S/N B. D Urso, R. Van Handel, B. Odom, D. Hanneke, and G. Gabrielse, Phys. Rev. Lett. 94, (2005)

29 Cyclotron/Spin Detection QND measurement:

30 Quantum Leaps

31 Cyclotron Procedure With the e - in the 0, state, pulse the cyclotron drive (150 GHz) Look for excitations to n = 1 Make a histogram of excitations versus frequency

32 Anomaly Procedure With the e - in the 0, state, pulse the anomaly drive (174 MHz) to move the e - through the gradient Look for a decay to 0, (slow!) Make a histogram of spin flips versus frequency Pump the electron back to 0, state before each measurement.

33 Determining the Cavity Shifts Two mode-detection techniques A synchronized cloud of electrons The single electron itself Synchronized electron technique: J. Tan and G Gabrielse, Phys. Rev. Lett. 67, 3090 (1991)

34 Determining the Cavity Shifts locations of our g-value measurements Determine the locations of the coupled modes Calculate the g value shift Uncertainty in mode location uncertainty in g L.S. Brown et al., Phys. Rev. A 32, 3204 (1985)

35 Applying the Cavity Shifts

36 Outline I. Introduction II. Measurement overview III. Novel techniques IV. Measurement details V. Uncertainties VI. Experimental challenges VII.What s next

37 Uncertainties g/2 = (28) [0.28 ppt] c / GHz = Uncertainties for g in parts-per-trillion. Statistics Cavity shift Uncorrelated lineshape model Correlated lineshape model Total

38 Lineshape Model Uncertainty Concern about magnetic field noise Get f c, a with a weighted-mean method Check with fits How well do they agree? L.S. Brown, Ann. Phys. (N.Y.) 159, 62 (1985)

39 Lineshape Model Uncertainty

40 Outline I. Introduction II. Measurement overview III. Novel techniques IV. Measurement details V. Uncertainties VI. Experimental challenges VII.What s next

41 Magnetic Field Stability Self-shielding solenoid reduces fluctuations by > 150. External fluctuations Magnet settling G. Gabrielse and J. Tan, J. Appl. Phys. 63, 5143 (1988)

42 Magnetic Field Stability Electrode motion in an inhomogeneous field

43 Temperature Regulation

44 Construction

45 Outline I. Introduction II. Measurement overview III. Novel techniques IV. Measurement details V. Uncertainties VI. Experimental challenges VII.What s next

46 Short Term Outlook New high-stability apparatus

47 Medium Term Outlook e + g-value / CPT test Cavity-assisted axial-cyclotron sideband cooling and other line-narrowing techniques Speed up the measurement cycle ( -pulses and adiabatic fast passage) μ p, μ p (first single-proton spin flip, improve the antiproton measurement by 10 6 ) Nick Guise Josh Dorr Shannon Fogwell

48 Long Term Outlook m p / m e Planar electrode geometries Electron as qubit S. Stahl, et al, Eur. Phys. J. D 32, 139 (2007) Josh Goldman Jack DiSciacca

49 Summary First improvements in g in 20 years (factor of 15 total) Cavity effects no longer dominate the uncertainties More to come... g/2 = (28) [0.28 ppt] -1 = (51) [0.37 ppb] D. Hanneke, S. Fogwell, and G. Gabrielse, Phys. Rev. Lett. 100, (2008) B. Odom, D. Hanneke, B. D Urso, and G. Gabrielse, Phys. Rev. Lett. 97, (2006) G. Gabrielse, D. Hanneke, T. Kinoshita, M. Nio, and B. Odom, Phys. Rev. Lett. 97, (2006). Ibid (E) (2007) High-Energy Physics with Low-Energy Symmetry Studies Friday, May 14, 12:30pm, Miller Room