Ultrastable Free-Space Laser Links for a Global Network of Optical Atomic Clocks
D.R. Gozzard, L. Howard, B.P. Dix-Matthews, S.F.E. Karpathakis, C.T. Gravestock, and S.W. Schediwy. Ultra-stable Free-Space Laser Links for a Global Network of Optical Atomic Clocks. Physical Review Letters 128 (2022) 020801.
Abstract
A global network of optical atomic clocks will enable unprecedented measurement precision in fields including tests of fundamental physics, dark matter searches, geodesy, and navigation. Free-space laser links through the turbulent atmosphere are needed to fully exploit this global network, by enabling comparisons to airborne and spaceborne clocks. We demonstrate frequency transfer over a 2.4 km atmospheric link with turbulence comparable to that of a ground-to-space link, achieving a fractional frequency stability of 6.1×1021 in 300 s of integration time. We also show that clock comparison between ground and low Earth orbit will be limited by the stability of the clocks themselves after only a few seconds of integration. This significantly advances the technologies needed to realize a global timescale network of optical atomic clocks.