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Optimization of a Prototype Atomic Clock Based onCoherent Population Trapping

Eugeniy Mikhailov,Nathan Belcher, and Irina Novikova

The College of William&Mary

October 30, 2008Southeastern Section of the American Physical Society

Eugeniy Mikhailov (WM) CPT Atomic clock October 30, SESAPS 2008 1 / 11

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Time keeping history

Ancient time: sun clocks, water clockspendulum clocks

1656 Huygens (1 minute per day)1721 Graham (1 second per day)1761 Harrison (1/5 second per day)1920 Shott a free-pendulum clock (10−7 or a few seconds per year)

1929 quartz clocks accuracy 10−7

1952 Cs atomic clocks accuracy 10−10

2001 Cs fountain clock accuracy 4 · 10−16

Since 1967 in International System of Units (SI) second.9,192,631,770 periods of the radiation of the ground state hyperfinetransition in cesium-133 atom (since 1967).

Example

Once we have a clock accurate to 10−10 we can find distances acrossUS with 1mm precision

Eugeniy Mikhailov (WM) CPT Atomic clock October 30, SESAPS 2008 2 / 11

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Coherent Population Trapping (CPT)

|b〉

|c〉ωbc

|a〉

ωp

0

0.2

0.4

0.6

0.8

1

-100 -50 0 50 100

Tra

nspa

renc

y [A

rb. U

nit]

Probe detuning [Arb. Unit]

Probe transparency dependence on its detuning.

Coherent Population TrappingDark |D〉 = Ωd |b〉 − Ωp|c〉 and Bright |B〉 = Ωd |c〉+ Ωp|b〉 statesresonance width (∼ 10kHz) much smaller then natural line width

Eugeniy Mikhailov (WM) CPT Atomic clock October 30, SESAPS 2008 3 / 11

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Coherent Population Trapping (CPT)

|b〉

|c〉ωbc

ωd

|a〉

ωp

0

0.2

0.4

0.6

0.8

1

-100 -50 0 50 100

Tra

nspa

renc

y [A

rb. U

nit]

Probe detuning [Arb. Unit]

Probe transparency dependence on its detuning.

Coherent Population TrappingDark |D〉 = Ωd |b〉 − Ωp|c〉 and Bright |B〉 = Ωd |c〉+ Ωp|b〉 statesresonance width (∼ 10kHz) much smaller then natural line width

Eugeniy Mikhailov (WM) CPT Atomic clock October 30, SESAPS 2008 3 / 11

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Coherent Population Trapping (CPT)

|b〉

|c〉ωbc

ωd

|a〉

ωp

0

0.2

0.4

0.6

0.8

1

-100 -50 0 50 100

Tra

nspa

renc

y [A

rb. U

nit]

Probe detuning [Arb. Unit]

Probe transparency dependence on its detuning.

Coherent Population TrappingDark |D〉 = Ωd |b〉 − Ωp|c〉 and Bright |B〉 = Ωd |c〉+ Ωp|b〉 statesresonance width (∼ 10kHz) much smaller then natural line width

Eugeniy Mikhailov (WM) CPT Atomic clock October 30, SESAPS 2008 3 / 11

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CPT observation

Rb cell inside magnetic shielding

VCSEL

λ/4 PD

Solenoid

Oscillator

DAVLL

Oscilloscope

Laser System

Rubidium Cell

Optical Laser Lock

Oscillator

0.20

0.18

CP

T r

eso

na

nce

(a

rb.

un

its)

-200 -100 0 100 200

Two-photon detuning (kHz)

19 kHz

2.30

2.25

2.20

2.15

CP

T r

eso

na

nce

(a

rb.

un

its)

-200 -100 0 100 200

Two-photon detuning (kHz)

55 kHz

(a) (b)

Eugeniy Mikhailov (WM) CPT Atomic clock October 30, SESAPS 2008 4 / 11

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Clock setup

Rb cell inside magnetic shielding

VCSEL

λ/4 PD

6.835GHz frequency

synthesizer

Lock-In amplifier

Slow frequency modulation

Solenoid

PIDcontroller

Oscillator

Frequencycounter

DAVLL

Eugeniy Mikhailov (WM) CPT Atomic clock October 30, SESAPS 2008 5 / 11

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Stability

Eugeniy Mikhailov (WM) CPT Atomic clock October 30, SESAPS 2008 6 / 11

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Stability

Allan deviation of 6 · 10−12 corresponds to 1 second per 5000 yearsclock inaccuracy.

Eugeniy Mikhailov (WM) CPT Atomic clock October 30, SESAPS 2008 7 / 11

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Miniature atomic clock

NIST clock with 1cm3 volume

Eugeniy Mikhailov (WM) CPT Atomic clock October 30, SESAPS 2008 8 / 11

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There is no 3-level atom and Rb is not one of them

CPT with circularly polarized light

m=−2 m=−1 m=0 m=1 m=2

F=2

F=2

F=1

Eugeniy Mikhailov (WM) CPT Atomic clock October 30, SESAPS 2008 9 / 11

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CPT with linearly polarized light

Suggested by A.V. Taichenachev, V.I. Yudin, and S.A. Zibrov

m=−2 m=−1 m=0 m=1 m=2

F=2

F=1

F=1

-400 -200 0 200 400

CP

T r

eson

ance

(ar

b.un

its)

Two-photon detuning (kHz)

B=0B=220 mG

Eugeniy Mikhailov (WM) CPT Atomic clock October 30, SESAPS 2008 10 / 11

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Summary

Clock with Allan deviation of 6 · 10−12 demonstratedSimilar stability for magneto insensitive configurationdemonstratedNathan Belcher, Eugeniy E. Mikhailov, and Irina NovikovaarXiv:0810.2071

Eugeniy Mikhailov (WM) CPT Atomic clock October 30, SESAPS 2008 11 / 11