PTB's Optical Ytterbium Single-ion Clock (IMAGE) Physikalisch-Technische Bundesanstalt (PTB) Caption Radio-frequency trap of PTB's optical ytterbium single-ion clock Credit (Photo: PTB) Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.