Multipath Interferometer on an AtomChip. Francesco Saverio Cataliotti

Transcription

1 Multipath Interferometer on an AtomChip Francesco Saverio Cataliotti

2 Outlook Bose-Einstein condensates on a microchip Atom Interferometry Multipath Interferometry on an AtomChip Results and Conclusions

3 Degenerate atoms T e m p e r a t u r a Fermioni Bosoni T < T F T < T C E F

4 Degenerate Atoms 1925: Einstein predicts condensation of bosons 6 s: Development of Lasers 8 s: Development of laser cooling 1985: Magnetic Trapping of ultracold atoms 1986: Optical trapping of Na 1987: Na Magneto-Optical Trap 1995: First 87 Rb Bose-Einstein Condensate First applications: - Interferometry - Earth and Space sensors - Quantum Information Huge playground for fundamental physics: - BEC with Li, Na, K, Cs, Fr - Optical gratings, collective excitations 21: First BEC of 87 Rb on an Atom Chip

5 Route to BEC in dilute gases n 3 db T 3 K 1-2 laser cooling T 1 K 1-6 evaporative cooling T 1 nk 2.6

6 Magneto Optical Trap (MOT) F=- v-kz cooling trapping

7 temperature Evaporative cooling remove highest velocities thermalization through elastic collisions cooling Forced evaporation in a magnetic trap (conservative potential) E x

8 BEC on a chip Macroscopic trap Micro-trap I Current ~ 1 A Power ~ 1.5 kw Ultra High Vacuum ~ 1-11 Torr double MOT system: Laser power ~ 5 mw = 1-1 Hz Large BEC 1 6 atoms but production cycle > 1 min Current < 1 A Power < 1 W = 1-1 khz High Vacuum ~ 1-9 Torr single MOT system: Laser power ~ 1 mw BEC 1 5 atoms and production cycle ~ 1 s

9 Laser Cooling close to a surface s + s - s + s + s - s -

10 B (Gauss) B (Gauss) BEC on a chip Planar Geometry gold microstrips on silicon substrates B wir (I wir = 3A) B bias = {,3.3,1.2} Gauss z (m) I wir = 31 A ; B bias = {,3.3,1.2} Gauss x (m)

11 BEC on a chip

12 BEC Generation Routine time [ms] action MOT in reflection loading 1^8 atoms MOT transfer close to the chip (~1mm) CMOT + Molasses 5 x 1^7 T ~ 1 μk Optical pumping Ancillary magnetic trap (big Z wire) 2 x 1^6 T ~ 12 μk Compression and transfer to the magnetic trap on chip (chip Z wire) 2 x 1^6 T ~ 5 μk (~2 μm) Evaporation (big U under the chip) BEC with 3x1^3 atoms, Tc=.5 μk End of the cycle

13 BEC on a chip MOT ~ 1^8 atoms Molasses phase ~ 5 x 1^7 T ~ 15 uk First Magnetic Trap (big Z wire) ~ 2 x 1^6 T ~ 12 uk Magnetic Trap on Chip (chip Z wire) ~ 2 x 1^6 T ~ 5 uk Free fall of the BEC BEC ~ 2 x 1^3 T <.5 uk

14 Outlook Bose-Einstein condensates on a microchip Atom Interferometry Multipath Interferometry on an AtomChip Results and Conclusions

15 Atom Interferometer BEC coherent form of matter, a wavepacket BEC 1 BEC 2 BEC 1,2 BEC 2 BEC 1,2 different spin states BEC 1 BEC 1 coupling mechanism Rabi pulse separation for measurement Stern-Gerlach experiment

16 BEC on a chip

17 Atomic Ramsey Interferometer - Theory - Solve GPE for the BEC 2 Δ=ω -ω start from mix two states ω ω let them evolve 1 Solve SE for 1 atom for the non-interacting BEC for time T mix them up again

18 space Rabi Oscillations Stern-Gerlach method mf=2 Tp mf=2 mf=1 Δ B BEC mf=2 time - pulse BEC mf=1 Rabi frequency

19 Rabi Oscillation mf -2-1 π/2 1 2 Rabi frequency ~ 5KHz

20 space Experimental Scheme: Ramsey Interferometer π/2 π/2 Δ B mf=2 mf=2 mf=1mf=2 mf=1 time

21 Ramsey Interferometer Oscillation frequency = 1/RF = 1/65KHz = 1.5 μs

22 Outlook Bose-Einstein condensates on a microchip Atom Interferometry Multipath Interferometry on an AtomChip Results and Conclusions

23 Parameters of the Interferometric Signal amplitude D Ariano & Paris, PRA (1996) Resolution: Working range: background Sensitivity: Weihs et al., Opt. Lett. (1996) 23

24 Multi-path Interferometer

25 Multi-Path interferometer 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 ) ( ) ( ) ( 1 1 x F x xf x F n n n

26 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

27 Multi-Path interferometer

28 Multi-Path interferometer

29 Outlook Bose-Einstein condensates on a microchip Atom Interferometry Multipath Interferometry on an AtomChip Results and Conclusions

30 What can you use it for? Detection of a Light-Induced Phase Shift Polarisation σ+ Polarisation σ- Light-pulse detuning from F=2 F=3 was 6.8GHz. 31

31 Conclusions 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.

32 Who did it? A typical BEC Ivan Herrera Jovana Petrovic Atom Chip Pietro Lombardi Team