Nature, Published online: 01 April 2026; doi:10.1038/s41586-026-10230-2Dissociative ionization of H2 molecules by the combination of a phase-locked attosecond laser pair and a few-cycle NIR laser shows that ion–photoelectron entanglement influences electronic coherence in H2+, allowing control over the degree of entanglement by varying the delay between the pulses.