Engineering and Control of Cold Molecules

1. Engineering and Control of Cold Molecules Molecule N. P. Bigelow University of Rochester

2. Why Cold (Polar) Molecules ?

3. Why Cold (Polar) Molecules ? Talks from: Shlyapnikov Pfau Burnett Sengstock . . .

4. Why Cold (Polar) Molecules ? Talks from: Shlyapnikov Pfau Burnett Sengstock . . . More Reasons Later in Talk

5. So what about cold molecules? Hard to find cycling transitions  Laser cooling of molecules is hard if not impossible

6. Doyle approach - Thermalization with cold helium gas & magnetic trapping Dilution Refrigerator ~mK Paramagnetic molecules Large samples

7. Meijer - time and spatially varying E fields – decelerator – (à la high-energy in reverse; H. Gould) accelerate

8. Meijer - decelerator (à la high-energy; H. Gould) decelerate

9. Here “Build” the molecules from a gas of pre-cooled atoms via photoassociation

10. A Quick Review ofPhotoassociationStarting with Homonuclears

11. Molecular potentials Homonuclear Singly excited state Ground state

12. Photoassociation Singly excited state photon Ground state 600-1000Å

13. Ground state molecule formation? Excited state photon Sp. emission Ground state

14. (transition rate) (collision rate& pair distribution)* (excitation rate)* (survival rate)*(process probability)* (density2)*(volume) These factors determine molecular production rates

15. Ground state molecule formation Poor Franck-Condon factors are discouraging  f  i   0 i  photon Sp. emission f 

16. In 1997 Pierre Pillet and co-workers startled the community by showing the Cs2 ground-state molecules were produced in a conventional optical trap

19. R-transfer method Frank-Condon Matching

22. Why not heteronuclear molecules?

23. Molecular potentials Far better Franck-Condon factors…. Singly excited state Ground state

25. We might be CLOBBERED by the pair distribution function Rhomo/Rhetero = 950/76 ~ 13 (Rhomo/Rhetero = 950/76 ~ 1/10)2 ~ 100 ! The interaction time is also smaller by a factor of ~ 13!

26. Nevertheless, several groups built multi-species MOTs - including Rochester and Sao Carlos and

27. Kasevich Arimondo Ingusio Weidemuller Windholz DeMille Stwalley/Gould Wang/Buell Ruff others Bose-Fermi&Isotopic: Jin, Salamon, Ertmer, Ketterle, Hulet, Sengstock… Sukenik NaCs NaK NaRb RbCs KRb LiCs LiNa ? Most “reactive”

28. We started with Na + Cs

29. Search for ground state molecules - the detection pathway 20-200 J 9ns 580-589 nm 2 mm2

30. NaCs formation and detection Traps 9ns 100J pulse @ 575-600nm time (s) -30 0 20 105

31. Choice of pulsed laser wavelength 575-600 nm was chosen • To implement a resonant ionization pathway • It has enough energy to 2-photon ionize NaCs  It will NOT resonantly ionize Cs

32. Na+Cs Lin Scale Zoom Time of Flight photons cold Na Cold Cs Cold NaCs Thermal Na Na2 Cs2

34. Is NaCs formed by the ionizing pulse ? Traps Na-push beam 9ns Ionizing Pulse time (s) -30 -15 0 20 105

35. Push –beam experiment

36. How cold are the molecules? We use time-of-flight from the interaction zone as our probe

37. NaCs Temp TNaCs ~ 260 K 0.2 m/s (kinetic temp)

38. KNaCs : The rate of formation • We detect 500 molecules in 10,000 pulses • Estimate ionization and detection efficiency ~ 10% • Kinetic model : 90% of NaCs drifts out of the trapping region between pulses. Production rate ~ 50 Hz   d [NaCs] / dt = KNaCs [Na][Cs] KNaCs ~ 7.4 x 10-15 cm3 s-1 

39. Measured depth of the triplet is 137-247 cm-1 Neumann & Pauly Phys. Rev. Lett.20, 357-359 (1968). and J. Chem. Phys.52, 2548-2555 (1970) We have scanned 0 – 268 cm-1 and found strong ion signals (includes 5% of singlet potential) We have a mixture of singlets and triplets C. Haimberger, J. Kleinert, npb PRA Rapid Comm. 70, 021402 (R) Aug 2004 NaCs has largest polarizability (measured) of all bi-alkalis

40. Coherent Transfer - State Selective Ro-vibrational ground state (lower dipole moment) or Single excited ro-vibrational state Incoherent transfer results already at Yale

41. The most important part of this part of our work: C. Haimberger J. Kleinert (M. Bhattacharya, J. Shaffer & W. Chalupczak)

42. KRb

43. RbCs

44. KRb 40,000 molecules/sec !!

45. Franck-Condon Factors for hetero-pairs based on long range (dispersion) potentials Wang & Stwalley, J. Chem Phys.

46. Cold (Polar) Moleculesand Quantum Information

47. Heteronuclear molecules are highly polarizable The dipole-dipole coupling of the molecules can be harnessed for quantum information applications (see protocols for EDMs in Quantum Dots - e.g. Barenco, et al PRL 82 1060) Polar Molecules Allow Coupling Enabling Quantum Information Applications

48. atoms bound molecular states Polar Molecules Allow Couplings Enabling Quantum Information Applications(based on scheme by Côté, Yellin [Lukin])

49. atoms bound molecular states Polar Molecules Allow Coupling Enabling Quantum Information Applications • Start with two molecules in same state

50. atoms bound molecular states Polar Molecules Allow Coupling Enabling Quantum Information Applications • Start with two molecules in same state • Use Raman pulses - create superposition