Control of Attosecond Entanglement and Coherence.

Calculations are presented of vibrational wave packet dynamics in H_{2}^{+} ions formed by ionization of neutral H_{2} by a pair of attosecond extreme ultraviolet laser pulses, using time-delayed dissociation of the cation by an ultraviolet probe pulse. The strength of experimentally observable two-level quantum beats as a function of the attosecond two-pulse delay can be related to ion+photoelectron entanglement resulting from the ionization process. This conclusion is supported by an evaluation of the purity of the reduced ion and photoelectron density matrices.