jats:titleAbstract</jats:title> jats:pWe present ALMA band 3 observations of the CO(6–5), CO(7–6), and [C jats:sci</jats:sc>] 369 jats:italicμ</jats:italic>m emission lines in three of the highest-redshift quasar host galaxies at jats:inline-formula jats:tex-math

</jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjaa81cbieqn1.gif" xlink:type="simple" /> </jats:inline-formula>. These measurements constitute the highest-redshift CO detections to date. The target quasars have previously been detected in [C jats:scii</jats:sc>] 158 jats:italicμ</jats:italic>m emission and the underlying FIR dust continuum. We detect (spatially unresolved, at a resolution of >2″, or ≳14 kpc) CO emission in all three quasar hosts. In two sources, we detect the continuum emission around 400 jats:italicμ</jats:italic>m (rest-frame), and in one source we detect [C jats:sci</jats:sc>] at low significance. We derive molecular gas reservoirs of (1–3) × 10jats:sup10</jats:sup> jats:inline-formula jats:tex-math

</jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjaa81cbieqn2.gif" xlink:type="simple" /> </jats:inline-formula> in the quasar hosts, i.e., approximately only 10 times the mass of their central supermassive black holes. The extrapolated [C jats:scii</jats:sc>]-to-CO(1–0) luminosity ratio is 2500–4200, consistent with measurements in galaxies at lower redshift. The detection of the [C jats:sci</jats:sc>] line in one quasar host galaxy and the limit on the [C jats:sci</jats:sc>] emission in the other two hosts enables a first characterization of the physical properties of the interstellar medium in jats:italicz</jats:italic> ∼ 7 quasar hosts. In the sources, the derived global CO/[C jats:scii</jats:sc>]/[C jats:sci</jats:sc>] line ratios are consistent with expectations from photodissociation regions, but not X-ray-dominated regions. This suggest that quantities derived from the molecular gas and dust emission are related to ongoing star-formation activity in the quasar hosts, providing further evidence that the quasar hosts studied here harbor intense starbursts in addition to their active nucleus.</jats:p>