Degenerate Quantum Gases manipulation on AtomChips

Francesco Saverio Cataliotti

• Bose-Einstein condensates on a microchip

• Atom Interferometry

• Multipath Interferometry on an AtomChip

• Results and Conclusions

Outlook

Degenerate atoms

Temperatura

T < TC

Bosoni T < TF

EF

Fermioni

Degenerate Atoms1925: 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 dBn

T 300 K 10-20

Route to BEC in dilute gases

laser cooling

evaporative cooling

10-6T 10 K

T 100 nK 2.6

F=- v-kz

coolingtrapping

Magneto Optical Trap (MOT)

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 chipMacroscopic trap Micro-trap

I

Current ~ 100 APower ~ 1.5 kW

double MOT system: Laser power ~ 500 mW

Ultra High Vacuum ~ 10-11 Torr

n = 10-100 Hz Current < 1 APower < 10 W

single MOT system: Laser power ~ 100 mW

High Vacuum ~ 10-9 Torr

Large BEC 106 atomsbutproduction cycle > 1 min

BEC 105 atomsandproduction cycle ~ 1 s

n = 1-100 kHz

s+s+

s- s-

s+ s-

Laser Cooling close to a surface

• Planar Geometry gold microstrips on silicon substrates

Bwir (Iwir= 3A) Bbias = {0,3.3,1.2} Gauss

1000 2000 3000 4000 5000

12345678

2000 1000 1000 2000

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z (mm)

x (mm)

1000 2000 3000 4000 5000

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2000 1000 1000 2000

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|B| (

Gau

ss)

|B| (

Gau

ss)

Iwir= 3 A ; Bbias= {0,3.3,1.2} Gauss Iwir= 1 A ; Bbias= {0,3.3,1.2} Gauss

BEC on a chip

BEC on a chip

BEC Generation RoutineMOT in reflection loading10^8 atoms

MOT transfer close to the chip (~1mm)

CMOT + Molasses 5 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

lens

CCD cameraatoms

Imaging cold atoms

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

BEC on a chip

Atomic Ramsey Interferometer

- Theory -

Solve SE for 1 atomfor the non-interacting BEC

1

2Δ=ω 0 -ω

ω ω0let them evolvefor time T

mix them up again

start from

mix two states

Solve GPE for the BEC

Rabi Oscillations

mf=1mf=2mf=2

time

Tp

BECmf=1

BECmf=2

B

Δ

spac

e

Stern-Gerlach method

- pulse

Rabi frequency

Rabi Oscillation

Rabi frequency ~ 50KHz

π/2

-2 -1

0

1

2

mf

Experimental Scheme:Ramsey Interferometer

mf=2mf=2 mf=1

mf=1

mf=2B

Δ

time

spac

e

π/2 π/2

Oscillation frequency = 1/RF = 1/650KHz = 1.5 μs

Ramsey Interferometer

• 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

24

Working range:

Weihs et al., Opt. Lett. (1996)

Multi-path Interferometer

Multi-Path interferometer

0000

000

000

000

0000W W W W

Funny enougn for N>3 the system can be aperiodic since frequencies are incommensurableEven 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

Multi-Path interferometer

Multi-Path interferometer

• 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.

32

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

Atom Chip Team

Ivan Herrera

Pietro Lombardi

our typical signal

Jovana Petrovic

Those who really did it

Ivan Herrera

Pietro Lombardi

A typical BEC

Jovana Petrovic

Who did it?