A high-accuracy mobile Al+ optical clock

Laboratory optical atomic clocks based on quantum-logic spectroscopy of the ¹S₀ ↔ ³P₀ transition in ²⁷Al⁺ have reached a systematic uncertainty of 8.6×10¹⁸ [1], enabling table-top tests of fundamental physics [2] as well as measurements of gravitational potential differences [3]. New applications in geodesy and hydrology will require that such clocks be ruggedized and packaged so that they can be deployed to and operated at sites of interest outside the laboratory. Before a high-precision global optical-frequency transfer network is realized, a portable optical clock with high accuracy could also facilitate comparison between high-accuracy clocks developed around the globe.