  We report CO detections in 17 out of 19 infrared ultraluminous QSO (IR QSO)
hosts observed with the IRAM 30m telescope. The cold molecular gas reservoir in
these objects is in a range of 0.2--2.1$\times 10^{10}M_\odot$ (adopting a
CO-to-${\rm H_2}$ conversion factor $\alpha_{\rm CO}=0.8 M_\odot {\rm (K km
s^{-1} pc^2)^{-1}}$). We find that the molecular gas properties of IR QSOs,
such as the molecular gas mass, star formation efficiency ($L_{\rm
FIR}/L^\prime_{\rm CO}$) and the CO (1-0) line widths, are indistinguishable
from those of local ultraluminous infrared galaxies (ULIRGs). A comparison of
low- and high-redshift CO detected QSOs reveals a tight correlation between
L$_{\rm FIR}$ and $L^\prime_{\rm CO(1-0)}$ for all QSOs. This suggests that,
similar to ULIRGs, the far-infrared emissions of all QSOs are mainly from dust
heated by star formation rather than by active galactic nuclei (AGNs),
confirming similar findings from mid-infrared spectroscopic observations by
{\it Spitzer}. A correlation between the AGN-associated bolometric luminosities
and the CO line luminosities suggests that star formation and AGNs draw from
the same reservoir of gas and there is a link between star formation on $\sim$
kpc scale and the central black hole accretion process on much smaller scales.
