H2CO

OHH2O

HCO

QED

e- e-

e- e-

Quantum dipolar gasPrecision test

Chemical reactionsQuantum measurement

Cold and Ultracold Molecules

EuroQUAM, Durham, April 18, 2009

J. Ye, JILA, NIST & CUhttp://jilawww.colorado.edu/YeLabs

Why ultracold matter?

• We can understand it• We can control it

The most precise measurements ever !

Quantum control, Quantum simulations, Quantum information

Fundamental understandings in condensed matter

Dipolar quantum systems

Atoms Polar molecules

R+

_

+

_

RMagneticdipoles

Electricdipoles

d ~ Debyed ~ Bohr magneton

e.g. BEC of Crd=6 B

(T. Pfau, Stuttgart)

EI~10-3 - 10-1 nK @ n=1012-1014/cm3

EI~10 - 1000 nK @ n=1012-1014/cm3

log 10

(den

sity

[cm

-3])

log10(temperature [K])-9 -6 -3 0

3

6

9

12

Dipolar crystal Phase transition

& many-bodyDipolar quantum gasQuantum informationUltracold Chemistry

Molecule optics & circuitryCold controlled chemistry

Novel collisionsFundamental testsPrecision measurement

Science with cold molecules

High density,

Ultracold temperature

~ KBT

log 10

(den

sity

[cm

-3])

log10(temperature [K])-9 -6 -3 0

3

6

9

12

Stark,magnetic,optical

deceleration

Buffer-gascooling

Photo-association

Coherent statetransfer

Quantumdegeneracy

Enhanced PA?Laser cooling?Sympathetic cooling?Evaporative cooling?

Technology for cold moleculesCarr, DeMille, Krems, & Ye, New. J. Phys. Special Issue (2009).

• Molecules in single quantum states, under precise control,for internal & external motions

• Unprecedented study of fundamentally important reactions (Dial the rates):

OH + HBr, OH + H2CO, CN + O2, OH + NO, OH + OH, CN + NH3, OH + H

Ultracold molecules: Precision Chemistry

H2CO

OH

H2O

HCO

Controlled molecular collisions Ultracold chemical reactions

Electric field

Stereo-Chemistry

E. Hudson et al.,Phys. Rev. A 73, 063404 (2006).

Cold ground-state molecules - Stark slower

370 m/s

336 m/s

300 m/s

259 m/s

211 m/s

148 m/s 33 m/s

Bethlem, Berden, Meijer, Phys. Rev. Lett. 83 1558 (1999). Bochinski et al, Phys. Rev. Lett. 91, 243001 (2003).

v

0 = 00

200 300 400

800

550 m/s to rest

1 K to 10 mK

104 – 106 molecules

Density:105 – 107 /cm3

H2CO

OH

Magnetic trapping of OHSawyer et al., Phys. Rev. Lett. 98, 253002 (2007).

decelerator

Magnetic trap

O

ds

H

Permanent-Magnet Trap

NdFeB (N42SH) Top = 120oC Bres = 1.24 T

10mm

Trap Loading

0 V +12 kV -12 kV

0 V 0 V 0 V

Trap Loading

~ 2 x 106 cm-3

70 mK

OH

He, D2, NH3 , …

beam source

Ecm ~ 5 cm-1 – 230 cm-1

Quantum threshold collisions Resonant energy transfer

Sawyer et al.,Phys. Rev. Lett. 101, 203203 (2008).

Trap and collisions

Absolute collision cross sections

Ecm (cm-1)

J = 5/2

J = 3/2

23/2

84 cm-1

OHD2: (1) J = 1 quadrupole moment (2) J = 1 J =3 (300 cm-1)

Electric Quadrupole guide:

13.5 cm ROC+/- 5 kV~130 m/s ND3

OH Magnet trap

Buffer gas-cooledmolecule source

H

O N

H/D

Ecm < 5 cm-1H/D

H/D

The possibility to probe polar collisions?

Doyle, Rempe, …

1''13 JX

(a) (b) (c)

(d)

A Molecular MOT ? B. K. Stuhl et al., “A magneto-optical trap for polar molecules,” Phys. Rev. Lett. 101, 243002 (2008).

TiO

Polar molecules near quantum degeneracy

J. Bohn (JILA), J. Hutson (Durham)

S. Ospelkaus, K.-K. Ni, M. Miranda, B. Neyenhuis, D. Wang, S. Kotochigova, P. S. Julienne,

D. Jin, and J. Ye

KRb molecules

40K Fermions 87Rb Bosons

Temperature ~400nK T/TF=3 Density ~1012/cm3

=0.01 Dipole ~0.5 Debye Long lived (~200ms)

|f(R)|2

EK

|g(R)|2

|e(R)|2

Laser

Internuclear distance R

En

erg

y

Traditional photo-association

PilletStwalleyHeinzenBigelow… …

|f(R)|2

EK

Laser

|e(R)|2

|g(R)|2

En

erg

y

Internuclear distance R

Resonant enhancementDeMilleWeidemüller

|FR(R)|2

|e(R)|2

EK

Laser

Internuclear distance R

En

erg

y

Resonant enhancement – in the ground

Côte

molecules

>

V(R)

Ebinding

Magneticfield

Colliding atoms

B

RRRR

EnergyEnergy

Magnetic-field Feshbach resonance

Field-tunable scattering resonance

Zirbel et al., Phys. Rev. Lett. 100, 143201 (2008).

Going to really deep ground potential

The problem – overlap

Laser fields:

1. Impractically strong

2. Nonlinear excitations

GroundElectronic state

PumpDump

Excited electronic

state

Coherent weak fields to achieve strong field effect

Pump pulseDump

pulse

Wave-packet dynamics bridge the overlap mismatch

Coherent accumulations resolve single quantum state

Pe’er, Shapiro, Stowe, Shapiro, Ye,Phys. Rev. Lett. 98, 113004 (2007).

Excited electronic

state

GroundElectronic state

PumpDump

1

2

3

1

3

1

Inter-nuclear distance R

Energ

y

v = 0, N = 0, J = 0

Good Franck-Condon for bothup and down transitions.

Excited state is triplet + singlet mixture

Sr

2

1

2

Frequency comb assisted STIRAP

Feshbach + STIRAP Ni et al., Science 322, 231 (2008)

Ospelkaus et al., Nature Phys. 4, 622

(2008)

JILA Sr optical atomic clocks

Inaccuracy ~ 1 x 10-16

(uncertainty in SI unit of time: 4 x 10-16)

Ludlow et al., Science 319, 1805 (2008). Campbell et al., Science 324, 360 (2009).

Counting the light ripple

Raman + EIT Dark Resonance

1 scanned, 2 fixed

1 fixed, 2 scanned

Sta

rk S

hift

(MH

z) B=1.1139(1) GHz

d=0.566(17) Debye

Stark Spectroscopy

4μs one-way transfer

Coherent Transfer - STIRAP

92% efficiency

No heating

T/TF=2.5

No Heating in Transfer Process

Direct Imaging of Molecules

0 ms

1 ms

3 ms

6 ms

Trapped Ground state polar molecules

Trap oscillation

Lifetime ~ 150 ms

EPol

||

Ospelkaus et al., Faraday Discussions 142

Atom-molecule collisions

3x104 K, =70(10)ms

3x105 K, =6(1)ms

KRb+ K

KRb+ K KRb+ Rb

=5.4(1.0) 10-11 cm3/s =6.5(1.0) 10-11 cm3/s

Atom-molecule collisions

A harpoon mechanism? J. Bohn

D. HerschbachJ. Hutson

P. Julienne

ionization energy- electron affinity

(1) Near unity probability loss due to short-range reactions(2) Quantum threshold behavior - long-range potential (van der Waals “Length”) characterizes universal inelastic scattering

Upper bound: 11 x10-11 cm3/s (KRb + K); 7.9 x10-11 cm3/s (KRb + Rb)

Rb2

KRb

K2

KRb+ K -> K2+Rb+ exothermic

endothermicKRb+ Rb -> Rb2+K-

Atom-molecule collisions

Nuclear spin states for v = 0, N = 0

We populate a single nuclear spin stateJ. AldegundeJ. Hutson

Dipolar collision resonance?

Collisions of two ground-state Fermionic polar molecules

Evaporative cooling?

Control of elastic/inelastic collisions?

J. Bohn

U(R

)

(nK

)

Shape or Feshbach?We will know soon.

• Quantum information (strong dipolar interactions, long coherence time)

• Quantum degeneracy (e.g. BEC) (anisotropic interactions)

• Dipolar phase transition (Condensed matter system)

Ultracold molecules: quantum physics

DeMille, Phys. Rev. Lett. 88, 067901 (2002).H.P. Buchler et al., PRL 98, 060404 (2007). T. Koch et al., Nature Phys. 4, 218 (2008). Micheli, Brennen, Zoller, Nature Physics 2, 341 (2006).

Special thanks

J. Bohn (JILA) P. Julienne (NIST), S. Kotochigova (Temple), J. Hutson (Durham)

OH and H2CO

B. SawyerB. StuhlM. Yeo

E. Hudson (UCLA)B. Lev (Illinois UC)H. Lewandowski (JILA)J. Bochinski (NC State)

KRb

S. OspelkausK.-K. NiM. MirandaB. NeyenhuisD. Wang

A. Pe’er (Israel)J. Zirbel

Deborah Jin