The cosmological constant from informational Landauer erasure at the Planck-Hubble boundary

The cosmological constant problem — the ~10^121 discrepancy between quantum field theory vacuum energy and the observed dark energy density — remains one of the deepest puzzles in theoretical physics. I propose that this discrepancy can be understood through a chain of three physically motivated postulates. First, the covariant entropy bound on the Hubble volume defines the number of independent degrees of freedom accessible to observation. Second, a minimum of N_crit = 2 distinguishable states (one bit) is required for any non-degenerate quantum measurement, setting an irreducible Landauer erasure cost per holographic degree of freedom. Third, the Unruh radiation associated with the Planck-scale ultraviolet cutoff consists of massless quanta obeying radiation thermodynamics (γ = 4/3), so that erasure costs the radiation enthalpy rather than the non-relativistic thermal minimum. Together these yield ρ_Λ = 4ℏc ln2 / (3π² ℓ_P² R_H²), giving 6.016 × 10⁻¹⁰ J/m³ versus the Planck 2018 measurement of 5.96 × 10⁻¹⁰ J/m³ — agreement to 0.94%. Once the three postulates are adopted, the framework contains no fitted dimensionless parameter. The predicted H₀ = 67.08 km/s/Mpc is consistent with CMB measurements (0.6σ from Planck 2018) and in 5.7σ tension with the SH0ES distance-ladder value.