Front Cover: Transportable Strontium Optical Lattice Clocks Operated Outside Laboratory at the Level of 10 ⁻¹⁸ Uncertainty (Adv. Quantum Technol. 8/2021)

Transportable Optical Lattice Clock with 7×10^{-17} Uncertainty.

We present a transportable optical clock (TOC) with ^{87}Sr. Its complete characterization against a stationary lattice clock resulted in a systematic uncertainty of 7.4×10^{-17}, which is currently limited by the statistics of the determination of the residual lattice light shift, and an instability of 1.3×10^{-15}/sqrt[τ] with an averaging time τ in seconds. Measurements confirm that the syst...

Lattice-induced frequency shifts in Sr optical lattice clocks at the 10(-17) level.

We present a comprehensive study of the frequency shifts associated with the lattice potential in a Sr lattice clock by comparing two such clocks with a frequency stability reaching 5×10(-17) after a 1 h integration time. We put the first experimental upper bound on the multipolar M1 and E2 interactions, significantly smaller than the recently predicted theoretical upper limit, and give a 30-fo...

Outside Front Cover

A transportable optical lattice clock

We present the experimental setup and first results of PTB’s transportable Sr clock. It consists of a physics package, several compact laser breadboards, and a transportable high finesse cavity for the clock laser. A comparison of the transportable system with our stationary optical lattice clock yields an instability of 2.2 × 10−15 √ s/τ for the transportable clock. The current fractional unce...

Synchronization of Distant Optical Clocks at the Femtosecond Level

The use of optical clocks or oscillators in future ultraprecise navigation, gravitational sensing, coherent arrays, and relativity experiments will require time comparison and synchronization over terrestrial or satellite free-space links. Here, we demonstrate full unambiguous synchronization of two optical time scales across a free-space link. The time deviation between synchronized time scale...