  I show that a generic quantum phenomenon can drive cosmic acceleration
without the need for dark energy or modified gravity. When treating the
universe as a quantum system, one typically focuses on the scale factor (of an
FRW spacetime) and ignores many other degrees of freedom. However, the
information capacity of the discarded variables will inevitably change as the
universe expands, generating "quantum bias" (QB) in the Friedmann equations
[Phys. Lett. A 382, 36, 2555 (2018)|arXiv:1707.05789]. If information could be
stored in each Planck-volume independently, this effect would give rise to a
constant acceleration $10^{120}$ times larger than that observed, reproducing
the usual cosmological constant problem. However, once information capacity is
quantified according to the holographic principle, cosmic acceleration is far
smaller and depends on the past behaviour of the scale factor. I calculate this
holographic quantum bias, derive the semiclassical Friedmann equations, and
obtain their general solution for a spatially-flat universe containing matter
and radiation. Comparing these QB-CDM solutions to those of $\Lambda$CDM, the
new theory is shown to be falsifiable, but nonetheless consistent with current
observations. In general, realistic QB cosmologies undergo phantom acceleration
($w_\mathrm{eff}<-1$) at late times, predicting a Big Rip in the distant
future.
