  We suggest that dark energy has a quantum informational origin. Landauer's
principle associated with the erasure of quantum information at a cosmic
horizon implies the non-zero vacuum energy having effective negative pressure.
Assuming the holographic principle, the minimum free energy condition, and the
Gibbons-Hawking temperature for the cosmic event horizon we obtain the
holographic dark energy with the parameter $d\simeq 1$, which is consistent
with the current observational data. It is also shown that both the
entanglement energy and the horizon energy can be related to Landauer's
principle.
