multipath interferometer on an...
TRANSCRIPT
• Bose-Einstein condensates on a microchip
•Atom Interferometry
• Multipath Interferometry on an AtomChip
• Results and Conclusions
Outlook
Degenerate Atoms
1925: Einstein predicts “condensation” of bosons
80’s: Development of laser cooling
1985: Magnetic Trapping of ultracold atoms
1986: Optical trapping of Na
1987: Na Magneto-Optical Trap
60’s: Development of Lasers
1995: First 87Rb Bose-Einstein Condensate
2001: First BEC of 87Rb
on an Atom Chip
Huge playground for fundamental physics:
- BEC with Li, Na, K, Cs, Fr…
- Optical gratings, collective excitations…First applications:
- Interferometry
- Earth and Space sensors
- Quantum Information
612.23 dB
n
T 300 K 10-20
Route to BEC in dilute gases
laser cooling
evaporative cooling
10-6T 10 K
T 100 nK 2.6
tem
pera
ture
Evaporative cooling
E
x
Forced evaporation in a magnetic trap
(conservative potential)
remove highest velocities
thermalization through elastic collisions
cooling
BEC on a chip
Macroscopic trap Micro-trap
I
Current ~ 100 A
Power ~ 1.5 kW
double MOT system:
Laser power ~ 500 mW
Ultra High Vacuum ~ 10-11 Torr
= 10-100 Hz Current < 1 A
Power < 10 W
single MOT system:
Laser power ~ 100 mW
High Vacuum ~ 10-9 Torr
Large BEC 106 atoms
but
production cycle > 1 min
BEC 105 atoms
and
production cycle ~ 1 s
= 1-100 kHz
• Planar Geometry gold microstrips on silicon substrates
Bwir (Iwir= 3A) Bbias = {0,3.3,1.2} Gauss
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z (m)
x (m)
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|B| (G
auss)
|B| (G
au
ss)
Iwir= 3 A ; Bbias= {0,3.3,1.2} GaussIwir= 1 A ; Bbias= {0,3.3,1.2} Gauss
BEC on a chip
BEC Generation Routine
MOT in reflection loading10^8 atoms
MOT transfer close to the chip (~1mm)
CMOT + Molasses5 x 10^7 atoms @ T ~ 10 μK
Optical pumpingAncillary magnetic trap (big Z wire)20 x 10^6 atoms @ T ~ 12 μK
Compression and transfer to themagnetic trap on chip (chip Z wire)20 x 10^6 atoms @ T ~ 50 μK (~200 μm)
Evaporation (big U under the chip)BEC with 30x10^3 atoms, Tc=0.5 μK
End of the cycle
5000
5450
5485
5490
5740
8300
time [ms] action
23000
MOT ~ 10^8 atoms
Molasses phase~ 5 x 10^7 atoms @ T ~ 15 uK
First Magnetic Trap (big Z wire)~ 20 x 10^6 atoms @ T ~ 12 uK
Magnetic Trap on Chip (chip Z wire)~ 20 x 10^6 atoms @ T ~ 50 uK
BEC~ 20 x 10^3 atoms @ T < 0.5 uK
Free fall of the BEC
BEC on a chip
• Bose-Einstein condensates on a microchip
•Atom Interferometry
• Multipath Interferometry on an AtomChip
• Results and Conclusions
Outlook
Atom Interferometer
coupling mechanism
BEC 1 BEC 1
BEC 2BEC
1,2
BEC 1
BEC 2
separation for measurement
Rabi pulse
Stern-Gerlach experiment
BEC – coherent form of matter , a wavepacket
BEC 1,2
different spin states
Atomic Ramsey
Interferometer
- Theory -
Solve SE for 1 atom
for the non-interacting BEC
1
2Δ=ω 0 -ω
ω ω0
let them evolve
for time T
mix them up again
start from
mix two states
Solve GPE for the BEC
Rabi Oscillations
mf=1mf=2mf=2
time
Tp
BEC
mf=1
BEC
mf=2B
Δ
space
Stern-Gerlach method
- pulse
Rabi frequency
Experimental Scheme:
Ramsey Interferometer
mf=2mf=2 mf=1
mf=1
mf=2B
Δ
time
space
π/2 π/2
• Bose-Einstein condensates on a microchip
•Atom Interferometry
• Multipath Interferometry on an AtomChip
• Results and Conclusions
Outlook
Parameters of the
Interferometric Signal
background
Sensitivity:
Resolution:
D’Ariano & Paris, PRA (1996)amplitude
23
Working range:
Weihs et al., Opt. Lett. (1996)
Multi-Path
interferometer
0000
000
000
000
0000
Funny enougn for N>3 the system can
be aperiodic since frequencies are
incommensurable
Even more fun they are the solutions of a
complex Fibonacci Polynomial
)()()( 11 xFxxFxF nnn
Multi-Path
interferometer
There does not exist a p/2 pulse.
To obtain the best resolution from
the interferometer one has to
optimize pulse area
• Bose-Einstein condensates on a microchip
•Atom Interferometry
• Multipath Interferometry on an AtomChip
• Results and Conclusions
Outlook
Detection of a Light-Induced Phase Shift
Polarisation σ-Polarisation σ+
Light-pulse detuning from F=2 F=3 was 6.8GHz.
31
What can you use it for?
• We have demonstrated a compact time-domain multi-path
interferometer on an atom chip
• Sensitivity can be controlled by an RF pulse acting as a controllable
state splitter.
• Resolution superior to that of an ideal two-path interferometer.
•Simultaneous measurement of multiple signals at the output enables
a range of advanced sensing applications in atomic physics and
optics
• Integration of interferometer with a chip puts it into consideration
for future portable cold-atom based measurement systems.
Conclusions
Ivan Herrera
Pietro Lombardi
A typical BEC
Jovana Petrovic
Who did it?
Atom Chip
Team