The Fit and the PendulumQuantum Mechanics and New Clocks

M. CrescimannoDepartment of Physics and Astronomy

Youngstown State University&

R. Walsworth , D. Phillips, Irina Novikova and Christine Wang

Harvard -Smithsonian Center for Astrophysics

$$$ : ONR, NASA, Research Corporation, Cluster Ohio Program, YSU PACER funds

"No one can serve two masters;for a slave will either hate one andlove the other or be devoted to theone and despise the other."

IDEAL CLOCK

Bright: need good SNR to "split" the line.

Dark: period needs to be immune from environment.

Based on regularity of periodic behavior must be:

Gerard David "Rest on the Flight into Egypt" 1512(?)

A Brief History of Time......Measurement

Mercury IonStability

103-4 104-6 107-10 1014

Size/Cost

RoomsTableQuarter?

Why Small Atomic Clocks?

Cell Phone Repeaters

GPS System

Rb Atomic Clock6.8 GHz 87Rb

microwave cavityOptical table: lasers, optics and magnetic shields

QL = 15,000split endplate design for double bulbmechanical tuningaccess for fiber optical detector

(Source: D. Phillips)

Level Scheme

What the experimentalist knows...

Level Scheme Simplified

What the theorist thinks...

Atomic Clock: Traditional Maser

Good:

Bad:

Simple , Bright

Light shifts, environment couplings large, bulky

Microwave Cavity

Shield

Light

RF Pickup

Need to shine some dark on this clock...

(Use interference)

Fountain Clocks

(Reduce time atoms spend in cavity)

CPT Clock

Coherent Population Trapped Clock

= optical pumping to a superposition hyperfine ground states

gbc

Wac

|a>

|c>|b>

Wab

Atomic population's dipole vanishes

"Dark State"

No microwave cavity Small Size

Simple construction

Low light readout

CPT = Electromagnetically Induced Transparency

Light Collisions, ...

RWA

o1

CPT = Electromagnetically Induced Transparency

Static Solution (exact)

Im(rho_01) = probe beam absorption

Little spike of transparency in middle...

Dispersion: Large index of refraction = slow- and stopped light

EIT window

CPT clock: lock to center of EIT window

CPT clock: Elements

2 Lasers

Shield

Photodetector

Schematic of "All-Optical" Atomic Clock

cellovensolenoidshields

gbc

Wac

|a>

|c>|b>

Wab

(Source: D. Phillips, R. Walsworth)

isolator

power level = +17 dBmfreq=6.834 GHz

x2 Multplier

VCXO

12 GHzphotodetector

cellovensolenoidshields

6.84 GHz LO

3.42 GHz drive

3.42 GHz EOM

DC feedback signal

laserdiode

Why so good?

Environmental susceptibility

(Data from I. Novikova)

Medium Term stability at the 1012 Level

Simulation

vapor cell inputs:gas, pressure, laser power,

beam diameter

diffusion coefficient, line shifts, broadenings...

gbc

Wac

|a>

|c>|b>

Wab

3-level density matrix solveraverage over velocities, diffusion

r dv

v

output lineshapes

calculations performed in C/GSL/IDL

parameters chosen to match experimental

conditions

from literature and our measurements

Detection

Simulation

Doppler effect + Motional Averaging (Lamb-Dicke)

Analytic solution for steady state

AC Stark Effect due to carrier

Lockin detection modulation dependent effects - (EIT line asymmetry)

Includes...

Preliminary ComparisonsSo many knobs to twist !

DATATHEORY

DATA

THEORY

Detuning Slope

w1/w0 ~ 10 mHz/MHZ

Slope is negative !

Dependence on Modulation

DATA

THEORY

Carrier Intensity Stark Effect

DATA

THEORY

CONCLUSIONS:

CPT clock may be promising

Experiment and QO theory are converging

QO theory informing design compromises