  Using the IRAM Plateau de Bure Interferometer, we report the detection of the
158 micron [CII] emission line and underlying dust continuum in the host galaxy
of the quasar ULAS J112001.48+064124.3 (hereafter J1120+0641) at
z=7.0842+/-0.0004. This is the highest redshift detection of the [CII] line to
date, and allows us to put first constraints on the physical properties of the
host galaxy. The [CII] line luminosity is (1.2+/-0.2)x10^9 Lsun, which is a
factor ~4 lower than observed in a luminous quasar at z=6.42 (SDSS J1148+5251).
The underlying far-infrared (FIR) continuum has a flux density of 0.61+/-0.16
mJy, similar to the average flux density of z~6 quasars that were not
individually detected in the rest-frame FIR. Assuming the FIR luminosity of
L_FIR = 5.8x10^11-1.8x10^12 Lsun is mainly powered by star-formation, we derive
a star-formation rate in the range 160-440 Msun/yr and a total dust mass in the
host galaxy of 6.7x10^7-5.7x10^8 Msun (both numbers have significant
uncertainties given the unknown nature of dust at these redshifts). The [CII]
line width of sigma_V=100+/-15 km/s is among the smallest observed when
compared to the molecular line widths detected in z~6 quasars. Both the [CII]
and dust continuum emission are spatially unresolved at the current angular
resolution of 2.0x1.7 arcsec^2 (corresponding to 10x9 kpc^2 at the redshift of
J1120+0641).
