Fundamental physics with diatomic molecules

D. DeMille

CP-violation

quantum computation

hadronic weak interactions

quantum phase transitions(?)

Graduate Students:Frederik Bay, Sarah Bickman, Yong Jiang

Postdoc:Dave Kawall

Undergrads:Yulia Gurevich, Cliff Cheung

Funding: Research Corporation, Packard Foundation, NSF, NIST, Sloan Foundation, CRDF

Search for the Electron Electric Dipole Moment

T-violation: a window to new physics

•CP-violation observed in K- and B-mesons ⇒ T is NOT conserved in nature

• Observations consistent with standard model description (CKM)but also consistent with other explanations

• CP-violation in SM is minimal: extensions to SM almost inevitably include NEW sources of T-violation

• Observed baryon asymmetry in universe REQUIRES new sources of T-violation

An EDM Violates P and T B-B rrrr ⋅σµ=⋅µ−=dipoleMagneticH E- E- rrrr⋅σ=⋅= ddH dipoleElectric

CPT theorem ⇒ T-violation = CP-violation

P T

How does an electron EDM arise?not renormalizable⇒ loop diagrams

2 5 µνµνψσγψ Fde

d =L

γ

eeExperimental limit: |de| < 1.6×10-27 e⋅cm

~10-29 e·cmTechnicolor10-27-10-28 e·cmMulti-Higgs10-26-10-29 e·cmLepton flavor-changing10-26-10-28 e·cmLeft-right symmetric

< 10-25 e·cmSupersymmetry~10-41 e·cmStandard Model

Predicted |de|CP-violation model

de is a powerful probe for new physics!

General method to detect an EDM:

B

ω=2µΒ

ω=2µΒ

E

+2dE

+2dE

E

-2dE

-2dE

Energy level picture:

Figure of merit for statistical sensitivity:

( )( )NTE

NSTE

resolutionshift &⋅⋅=∝ −1//1

Selective excitation and laser-induced alignment of an Ω-doublet level:

1+1-

~12 MHz

X(0) [1Σ+]

0+

1-

2+

~10 GHz

•••

a(1) [3Σ+]

2+2-

•••

Laser pulseλ ~ 571 nm

bandwidth ~ 1 GHz ~ ∆νDoppler

m = +1m = -1m = 0

linear polarization ε ⊥ B⇒ |f> = |+1> + |-1> = |↔>

Zeeman splitting0-300 kHz typical

Present Experimental Setup

Pulsed Laser Beam5-40 mJ @ 100 Hz ∆ν ~ 1 GHz ε ⊥ B

Larmor Precessionν ~ 100 kHzPhoto-

multiplier tube B

solid quartz lightpipes

DataProcessing

Vacuum chamber

0

10

20

30

40

50

0 50 100 150 200time from laser pulse (µs)

Sign

al (m

V)

Noise consistentwith shot noise on

background

FFT Power Spectra of Signal-Exponential Fit

0

0

0

0

0

0

100 150 200 250 300 350 400Beat frequency (KHz)

Arb

. Uni

ts

~10 s integration

Observation of quantum beats in PbO

Signals at two different values of magnetic field B

Searching for Supersymmetrywith the electron EDM

Implications of current and ongoing electron EDM searches

HsFA-CP

A-UnAlign

de (e⋅ cm)10-26 10-28 10-30 10-32 10-34

NAIVE SUSY

SO(10) GUT

AC: Accidental CancellationsHsF: Heavy sFermionsA-CP: Approx. CPA-Un: Approx UniversalityAlign: AlignmentE-Un: Exact Universality

AC E-Un

The PbO EDM group

Funding: NSF ITR, Packard Foundation, Keck Foundation

Quantum computation withtrapped polar molecules

Graduate Students:Sunil Sainis, Jeremy Sage, Marco Ascoli

Postdoc:Jamie Kerman

Undergrad:Peter Gilbert

What is a quantum computer?

Register = collection of individually addressable 2-level systems

Processor = Controllable, time-dependent Hamiltonian

Any logical operation = 1-bit rotations (0a↔1a)

+ CNOT: (0a↔1a iff xb=1)

Q: So What?

A: Quantum algorithms using superpositions and entanglement

make certain problems (e.g. factoring, eigenvalues/vectors, etc.)

computationally tractablebecause of exponential speedup

CNOT requires bit-bit interactions

Without interactions:

Desired:a flips if b=1

|0>a|0>b

|1>a|0>b

|0>a|1>b

|1>a|1>b

Undesired:a flips if b=0

CNOT requires bit-bit interactions

With interaction H' = aSa⋅Sb

|0>a|0>b

|1>a|0>b

|0>a|1>b

|1>a|1>b

THIS IS A TWO-BIT QUANTUM COMPUTER!

Size of interaction term “a”determines maximum gate speed:

τ-1 ~ ∆ν ~ a

Issues for quantum computation

• Speed:how fast can you manipulate bits?

(Determined by size of bit-bit coupling)

• Decoherence & Fidelity:how many logical operations

can you perform before quantum state is destroyed?

(Determined by coupling of bits to outside world + degree of control over gate operations)

• Scaling up:how many bits can you store and manipulate?

(Determined by technical details)

H0 = -d⋅E, Ea ≠Eb; H' = -da⋅db/r3

distance between bits "r" isfixed in optical trap:

-V

+V

Standing-wave trap laser beam

Strong E-field

Weak E-field

E-field due to eachdipole influences

its neighbors

Our goal: a quantum computerwith bits = polar molecules

• Polar molecules in optical lattice trap• bits = “permanent” electric dipole moments of

polarized diatomic molecules• interaction = electric dipole-dipole

(fairly strong, a ~ 3-30 kHz)• processor = rf electric resonance (easy, like NMR)• addressing = spectroscopic, with E-field gradient• decoherence = Raman scattering from trap laser

(T ~ 5 s; Nop ~ 105 !)• readout = laser-induced ionization + imaging

(easy, but destructive)• scaling up? ( 104 bits looks reasonable!)

Technologically interesting thresholds:

Nop 104 ⇒ robust error correction OK?

Crude scaling ⇒ 300 bits, 104 ops/s = equivalent of teraflop classical computer

Why use polar molecules for quantum computation?

How to make them?Photoassociation:

(Use photon to carry away excess energy)

s1+p2=A

s1+s2= X

photo-association

laserspont. emission to high vib. level

excited-state potential

ground state potential

Internuclear Distance R

Ener

gy

stimulated Raman transfer to ground state (2 lasers)

Molecules formed at same translationaltemperature as atoms (+1-2 photon recoils)

Minimal decoherence⇒ weak trap ⇒ ultracold molecules

JeremySage

SunilSainis

JamieKerman

MarcoAscoli

Research opportunities in the DeMille group

Electron EDM: 1 student

quantum computation: 1 student(?)

hadronic weak interactions (NEW): 1-2 students

direct cooling of polar molecules (NEW):1-2 students

Dave DeMilleOffice: 46 SPL; Labs 23 & 28 SPL

david.demille@yale.edu432-3833

Many-body physics w/ultracold polar molecules

New quantum phases:K Goral et al., Phys. Rev. Lett. 88, 170406 (2002):

“Quantum Phases of Dipolar Bosons in Optical Lattices”

Tunable strength and isotropy:S. Giovanazzi, A. Goerlitz, and T. Pfau, Phys. Rev. Lett. 89, 130401 (2002):

“Tuning the Dipolar Interaction in Quantum Gases”

BCS pairing:M. Baranov, et al., Phys. Rev. A 66, 013606 (2002):“Superfluid pairing in a polarized dipolar Fermi gas”

Controlled chemical reactions:N. Balakrishnan and A. Dalgarno, Chem. Phys. Lett. 341, 652 (2001):

“Chemistry at ultracold temperatures”

Strong, long-range, anisotropic, tunable interactionsat ultracold temperatures--a new regime

Axial hadronic weak interactions

VN, AN

Ve, Ae

Z0

N = p, n

e

VeAN and AeVNterms violate parity

VeAN couplings small, barely known,

sensitive to new physics such as

quark substructure

~10% left-right asymmetry in molecules!!

γ

N

e

Z0, W±

Intra-nuclear parity-violating weak

interactions create nuclear “anapole

moment” that couples magnetically

to electron