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

Niles Bohr Institute

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

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

The experimental setup Niles Bohr Institute The experimental setup

Block Sphere representation Niles Bohr Institute Block Sphere representation Jy Jx Jz

-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

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

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, 230801

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

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

Niles Bohr Institute Headline Content