176Lu+ clock comparison at the 10-18 level via correlation spectroscopy.

The extreme precision of optical atomic clocks has led to an anticipated redefinition of the second by the International System of Units. Furthermore, accuracies pushing the boundary of 1 part in 1018 and beyond will enable new applications, such as in geodesy and tests of fundamental physics. The 1S0 to 3D1 optical transition in 176Lu+ has exceptionally low sensitivity to external perturbations, making it suitable for practical clock implementations with inaccuracy at or below 10-18. Here, we perform high-accuracy comparisons between two 176Lu+ references using correlation spectroscopy. A comparison at different magnetic fields is used to obtain a quadratic Zeeman coefficient of -4.89264(88) Hz/mT for the reference frequency. With a subsequent comparison at low field, we demonstrate agreement at the low 10-18 level, statistically limited by the averaging time of 42 hours. The evaluated uncertainty in the frequency difference is 9 × 10-19 and the lowest reported in comparing independent optical references.

Erratum: Realization of the Dicke Model Using Cavity-Assisted Raman Transitions [Phys. Rev. Lett. 113, 020408 (2014)].

This corrects the article DOI: 10.1103/PhysRevLett.113.020408.

Realization of the Dicke model using cavity-assisted Raman transitions.

We realize an open version of the Dicke model by coupling two hyperfine ground states using two cavity-assisted Raman transitions. The interaction due to only one of the couplings is described by the Tavis-Cummings model and we observe a normal mode splitting in the transmission around the dispersively shifted cavity. With both couplings present the dynamics are described by the Dicke model and we measure the onset of superradiant scattering into the cavity above a critical coupling strength.

Detection of ion micromotion in a linear Paul trap with a high finesse cavity.

We demonstrate minimization of ion micromotion in a linear Paul trap with the use of a high finesse cavity. The excess ion micromotion projected along the optical cavity axis or along the laser propagation direction manifests itself as sideband peaks around the carrier in the ion-cavity emission spectrum. By minimizing the sideband height in the emission spectrum, we are able to reduce the micromotion amplitude along two directions to approximately the spread of the ground state wave function. This method is useful for cavity QED experiments as it describes the possibility of efficient 3-D micromotion compensation despite optical access limitations imposed by the cavity mirrors. We also show that, in principle, sub-nanometer micromotion compensation is achievable with our current system.