Sub-recoil clock-transition laser cooling enabling shallow optical lattice clocks

TL;DR

This paper demonstrates a novel pulsed cooling method using the ultranarrow clock transition in ytterbium, achieving sub-recoil temperatures and enabling shallow lattice clocks with improved accuracy and stability.

Contribution

It introduces a pulsed radial cooling scheme with sideband cooling on the clock transition, allowing for sub-recoil temperatures and shallow lattice clocks with minimal tunneling shifts.

Findings

Achieved cooling down to tens of nanokelvin.

Prepared atoms in shallow lattices at 6 recoil energies.

Reduced limits on lattice clock accuracy and instability.

Abstract

Laser cooling is a key ingredient for quantum control of atomic systems in a variety of settings. In divalent atoms, two-stage Doppler cooling is typically used to bring atoms to the uK regime. Here, we implement a pulsed radial cooling scheme using the ultranarrow 1S0-3P0 clock transition in ytterbium to realize sub-recoil temperatures, down to tens of nK. Together with sideband cooling along the one-dimensional lattice axis, we efficiently prepare atoms in shallow lattices at an energy of 6 lattice recoils. Under these conditions key limits on lattice clock accuracy and instability are reduced, opening the door to dramatic improvements. Furthermore, tunneling shifts in the shallow lattice do not compromise clock accuracy at the 10-19 level.