To test the synchronicity of two clocks — one at Argonne and one at Fermilab — scientists transmitted a traditional clock signal (blue) and a quantum signal (orange) simultaneously between the two clocks. The signals were sent over the Illinois Express Quantum Network. Researchers found that the two clocks remained synchronized within a time window smaller than 5 picoseconds, or 5 trillionths of a second. Image: Lee Turman, Argonne