QFEXT07 Leipzig, Germany, September 17-21, 2007.
Recent progress on the precision measurement of the Casimir interaction
Ricardo S. DeccaDepartment of Physics, IUPUI
QFEXT07 Leipzig, Germany, September 17-21, 2007.
Daniel López Alcatel-Lucent Technologies
Ephraim Fischbasch Purdue University
Dennis E. Krausse Wabash College and Purdue University
Valdimir M. Mostepanenko Noncommercial Partnership “Scientific Instruments”, Russia
Galina L. Klimchitskaya North-West Technical University, Russia
Eduardo Osquiguil Instituto Balseiro, Argentina. Fullbright Fellow.
NSF, DOE, LANL
Collaborators
Funding
QFEXT07 Leipzig, Germany, September 17-21, 2007.
Why does it matter?
• Consequences in nanotechnology (MEMS and NEMS)“Long-range” interaction between moving partsPossibility of controlling the interaction by engineering materials
• Consequences in quantum field theoryThermal dependence
• Consequences in gravitationBackground to measure deviations from Newtonian potential at smallseparations
QFEXT07 Leipzig, Germany, September 17-21, 2007.
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, 2007.
703.4 703.6 703.8 704.0 704.20.0
0.2
0.4
0.6
0.8
1.0
Nor
mal
ized
am
plitu
de
Freq (Hz)
Hzrad10 9
400 600 800 10001E-15
1E-14
1E-13
1E-12
1E-11
F N
/Hz1/
2
Freq (Hz)
22
2
1
41
elth
el
o
B
FFb
AQ
Tk
bF
elF
thF
QFEXT07 Leipzig, Germany, September 17-21, 2007.
Dynamic measurements
z
F
I
b C
oor 2
222 1
CC
CC PRz
FERF
22
400 600 800 10000
50
100
150
200
250
PC (
mP
a)
z (nm)
R = 300 m R = 150 m
100 200 300 400 500 600 700 800
-2
0
2
4
6
8
10
P (
mP
a)
z (nm)
QFEXT07 Leipzig, Germany, September 17-21, 2007.
Separation measurement
bzzzz goimetal
zg = (2172.8 ± 0.1) nm, interferometer
zi = ~(12000.0 ± 0.2) absolute interferometer
zo = (8162.3 ± 0.5) nm, electrostatic calibration
b = (206 ± 3) m, optical microscope
= ~(1.000 ± 0.001) rad
zg
zmeas is determined using a known interaction
zi, are measured for each position
QFEXT07 Leipzig, Germany, September 17-21, 2007.
Distance measurement
Electrostatic force calibration
-15 -10 -5 0 5 10 15 20 250.0
0.2
0.4
0.6
0.8
1.0
(
rad
)
VAu
(mV)
z = 3 mz = 5 m
3.00 3.25 3.50 3.75 4.00 4.25 4.50 4.75 5.00
100
125
150
175
200
225
250
275
300
325
350
Fe (
pN
)
z (m)
V = 0.35 V
V = 0.27 V
)2()( 2
ometalAuoe z
RVVF
Determine:• R• VAu
• o
• ometalzz 2
QFEXT07 Leipzig, Germany, September 17-21, 2007.
LC =(775 +/- ) nm (low coherence),
CW 1550 nm (high coherence) in
x
Mirror (v ~ 10 m/s)
x = zi
Readout
- Changes in about 2 nm) give different curves. Intersections provide x
-Quite insensitive to jitter. Only 2x’/(CW)2 Instead of 2x’/CW
(Yang et al., Opt. Lett. 27, 77 (2005)
)2(mod)()(
int4
2
21
xxS
SSz
DDphase
phasefringeCW
i
CWLCD
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
1.1
1.2
1.3
1.4
1.5
D
= 1.7 nm = -2.1 nm
0 2 4 6 8 10 12 14 16 18 20 22 24-1
0
1
2
3
4
5
6
7
CW
x (m)
Interferometer
Distance measurement
QFEXT07 Leipzig, Germany, September 17-21, 2007.
Pressure determination
-Dark grey, Drude model approach-Light grey, Leontovich impedance approach
PRD 75, 077101
QFEXT07 Leipzig, Germany, September 17-21, 2007.
Pressure determination
Random error
Systematic error
For the first time in our experimentthe random error is smaller than the systematic one
QFEXT07 Leipzig, Germany, September 17-21, 2007.
Pressure determination
2/32
4)(
pp
TT
eV)1.09.8( p
What are the characteristics of the Au used?
Plasma model
Leontovich impedance
QFEXT07 Leipzig, Germany, September 17-21, 2007.
Proximity force approximation
z
F
RR
zzPRzP
R
zzRRzF
Cppeff
ppCasimirC
2
1...1)(,
...12,
'
Measurements as a function of R
10.5 m31.4 m52.3 m
102.8 m148.2 m
400 600 800 10000
50
100
150
200
250
PC (
mP
a)
z (nm)
R = 300 m R = 150 m
QFEXT07 Leipzig, Germany, September 17-21, 2007.
Proximity force approximation
Insets:Fits at z =170 nm
Yield the slopes ’
z
F
RR
zzPRzP
R
zzRRzF
Cppeff
ppCasimirC
2
1...1)(,
...12,
'
QFEXT07 Leipzig, Germany, September 17-21, 2007.
Proximity force approximation
’(z<300 nm)| < 0.4
Not so clearwith
If we assume the ideal case situation,
|(z<300 nm)| < 0.6
QFEXT07 Leipzig, Germany, September 17-21, 2007.
Future work
• External parameters to change ()Negative index of refraction materialsMagnetic field in manganitesQuantum Hall effect
• Thermal dependenceCheck for consistency between models by lowering the temperature
• Corrections to Newtonian gravitationCheck upturn observed at low separationsContinue building new system for “Casimir-less”measurements
QFEXT07 Leipzig, Germany, September 17-21, 2007.
-Reduce background
What’s next?
Si
Ti
Si
Si
Ti
Si
Si
Ti
Si Au
Si
Ti
Si Au
Glass
Au
Ti
Si Au
Glass
r/n
-Improve signal
QFEXT07 Leipzig, Germany, September 17-21, 2007.
1 0
- 7
1 0
- 6
1 0
- 5
1 0
- 4
1 0
2 0
1 0
1 6
1 0
1 2
1 0
8
1 0
4
1 0
0
5
3
4
m e t e r s
1
Gau ged Baryon s
Excludedby
exper im ents
Glu
on
mod
ulus
2
Str
ang
e m
od
ulu
s
Two orders of magnitude improvement
About four orders ofmagnitude improvement
QFEXT07 Leipzig, Germany, September 17-21, 2007.
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, 2007.
Proximity force theorem
a
k,4
122
kCC hRERF
CE : 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, 2007.
bQf
TkF
r
B 12
serp
Sis L
Ewt
6
3
t
w
L
tEw Sir 3
2 3
w, t = 2m
40r
s