QFEXT07 Leipzig, Germany, September 17-21, Recent progress on the precision measurement of the Casimir interaction Ricardo S. Decca Department of Physics, IUPUI

QFEXT07 Leipzig, Germany, September 17-21, Daniel LópezAlcatel-Lucent Technologies Ephraim FischbaschPurdue University Dennis E. Krausse Wabash College and Purdue University Valdimir M. MostepanenkoNoncommercial Partnership “Scientific Instruments”, Russia Galina L. KlimchitskayaNorth-West Technical University, Russia Eduardo OsquiguilInstituto Balseiro, Argentina. Fullbright Fellow. NSF, DOE, LANL Collaborators Funding

QFEXT07 Leipzig, Germany, September 17-21, Why does it matter? Consequences in nanotechnology (MEMS and NEMS) “Long-range” interaction between moving parts Possibility of controlling the interaction by engineering materials Consequences in quantum field theory Thermal dependence Consequences in gravitation Background to measure deviations from Newtonian potential at small separations

QFEXT07 Leipzig, Germany, September 17-21, Outline Experimental set-up -Measurement of the force between a Au-coated sphere and a Au-coated plate -Determination of the equivalent pressure between two Au-coated plates -Measurement of the separation between the bodies Casimir interaction Experimental studies of the PFA Future directions -External parameters to change  (  ) -Low temperature measurements -Constraints on Newtonian gravitation Summary

QFEXT07 Leipzig, Germany, September 17-21, Experimental setup

QFEXT07 Leipzig, Germany, September 17-21, 2007.

Dynamic measurements

QFEXT07 Leipzig, Germany, September 17-21, Separation measurement z g = ( ± 0.1) nm, interferometer z i = ~( ± 0.2) absolute interferometer z o = ( ± 0.5) nm, electrostatic calibration b = (206 ± 3)  m, optical microscope  = ~(1.000 ± 0.001)  rad zgzg z meas is determined using a known interaction z i,  are measured for each position

QFEXT07 Leipzig, Germany, September 17-21, Distance measurement Electrostatic force calibration Determine: R V Au  o 

QFEXT07 Leipzig, Germany, September 17-21, LC =(775 +/-  ) nm (low coherence), CW 1550 nm (high coherence) in x Mirror (v ~ 10  m/s)  x = z i Readout - Changes in  about 2 nm) give different curves. Intersections provide  x -Quite insensitive to jitter. Only 2  x’/( CW ) 2 Instead of 2  x’/ CW (Yang et al., Opt. Lett. 27, 77 (2005) Interferometer Distance measurement

QFEXT07 Leipzig, Germany, September 17-21, Pressure determination

QFEXT07 Leipzig, Germany, September 17-21, Pressure determination -Dark grey, Drude model approach -Light grey, Leontovich impedance approach PRD 75,

QFEXT07 Leipzig, Germany, September 17-21, Pressure determination Random error Systematic error For the first time in our experiment the random error is smaller than the systematic one

QFEXT07 Leipzig, Germany, September 17-21, Pressure determination What are the characteristics of the Au used? Plasma model Leontovich impedance

QFEXT07 Leipzig, Germany, September 17-21, Proximity force approximation Measurements as a function of R 10.5  m 31.4  m 52.3  m  m  m

QFEXT07 Leipzig, Germany, September 17-21, Proximity force approximation Insets: Fits at z =170 nm Yield the slopes  ’

QFEXT07 Leipzig, Germany, September 17-21, Proximity force approximation  ’(z<300 nm)| < 0.4 Not so clear  with  If we assume the ideal case situation, |  (z<300 nm)| < 0.6

QFEXT07 Leipzig, Germany, September 17-21, Future work External parameters to change  (  ) Negative index of refraction materials Magnetic field in manganites Quantum Hall effect Thermal dependence Check for consistency between models by lowering the temperature Corrections to Newtonian gravitation Check upturn observed at low separations Continue building new system for “Casimir-less” measurements

QFEXT07 Leipzig, Germany, September 17-21, Reduce background What’s next? -Improve signal

QFEXT07 Leipzig, Germany, September 17-21, Two orders of magnitude improvement About four orders of magnitude improvement

QFEXT07 Leipzig, Germany, September 17-21, Summary Random errors smaller than systematic ones Improved agreement with theory Experimental investigations to test PFA Continued effort towards a more sensitive “Casimir-less” experiment

QFEXT07 Leipzig, Germany, September 17-21, 2007.

Jonathan L. Feng, Science 301, 795 (’03) The strength of gravity for various numbers of large extra dimensions n, compared to the strength of electromagnetism (dotted) Without extra dimensions, gravity is weak relative to the electromagnetic force for all separation distances. With extra dimensions, the gravitational force rises steeply for small separations and may become comparable to electromagnetism at short distances. What is the background?

QFEXT07 Leipzig, Germany, September 17-21, Proximity force theorem a : energy density R Believed to be exact for Casimir interaction. Proved to produce errors smaller than a/R ~ 1/1000

QFEXT07 Leipzig, Germany, September 17-21, t w w, t = 2  m

QFEXT07 Leipzig, Germany, September 17-21, v i : Fraction of the sample at separation zi AFM image of the Au plane