1. Atomic Clocks Niles Bohr Institute PhD Student: Johannes Borregaard
Supervisor: Anders S. Sørensen
Niels Bohr Institute

2. Niles Bohr Institute

3. Overview of the talk Basic principles of an atomic clock
Niles Bohr Institute
Overview of the talk
Basic principles of an atomic clock
The quantum noise
Squeezing the noise
Adaptive measurements

4. Definition of the second
Niles Bohr Institute
Definition of the second
Cs-133 6s
f=9,192,631,770 Hz

5. The experimental setup
Niles Bohr Institute
The experimental setup

6. Block Sphere representation
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Block Sphere representation Jy Jx Jz

7. -π π -π/2 π/2 π/2+φ Ramsey Spectroscopy N/2 Jz Jz Jy Jx Jy Jx
Niles Bohr Institute
Ramsey Spectroscopy Jy Jx Jz -π π
-π/2
π/2
π/2+φ
N/2 Jy Jx Jz
D. J. Wineland, J. J Bollinger and W. M. Itano, Phys. Rev. A, 1994, vol 50, 67

8. Quantum Noise Heisenberg’s uncertainty relation
Niles Bohr Institute
Quantum Noise
Heisenberg’s uncertainty relation
For coherent spin state (CSS) Jx Jz Jy

9. Squeezing the noise Jz Jz Jy Jy φ φ Jz Jx Jx 1 1
Niles Bohr Institute
Squeezing the noise Jz Jz Jy Jy φ φ 1 Jz Jx Jx 1
A. André, A.S. Sørensen and M. D. Lukin, Phys. Rev. Lett., vol 92,

10. Adaptive measurements
Niles Bohr Institute
Adaptive measurements
Idea: Do weak measurements and feedback on the atoms Jz Jy Jz Jy Jz Jy Jz Jy
φest,3
φest,4
φest,2
φest,1
D. W. Berry and H. M. Wiseman, Phys. Rev. Lett., vol 85, 5098

11. Thank you for your attention
Niles Bohr Institute
Thank you for your attention

12. Niles Bohr Institute
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