Beyond the Standard Quantum Limit in the Synchronization of Low-Earth-Orbit Satellites

Highly-accurate time synchronization between satellites provides for a plethora of fundamental physics investigations as well as providing for a range of enhanced-engineering applications. However, current state-of-the-art synchronization techniques in space are limited by the Standard Quantum Limit (SQL), thereby limiting progress. Squeezed light, however, offers a pathway to overcome the SQL — an example of the ‘quantum advantage’ offered by non-classical states of light. Here we investigate, for the first time, the practicality of achieving such a quantum advantage between low-Earth-orbit satellites. Among other deployed-platform issues, we pay particular attention to the impact photon loss and pointing error have on the transmitted squeezing level. A key finding of our work is the identification of the conditions under which quantum enhancement, via squeezed light alone, can deliver a factor of two improvement in timing resolution between two satellites. Our work, for the first time, sets the baseline for quantum timing enhancements in satellite networks achievable with current technology. We discuss how advanced quantum techniques beyond squeezed light could improve upon the results presented here.