  We present a submillimetre continuum survey ('SCUBA2 High rEdshift bRight
quasaR surveY', hereafter SHERRY) of 54 high redshift quasars at $5.6<z<6.9$
with quasar bolometric luminosities in a range of (0.2$-$$
5)\times10^{14}\,L_{\odot}$, using the Submillimetre Common-User Bolometer
Array-2 (SCUBA2) on the James Clerk Maxwell Telescope. About 30% (16/54) of the
sources are detected with a typical 850$\mu$m rms sensitivity of 1.2 $\rm
mJy\,beam^{-1}$ ($S\rm _{\nu,850\,\mu m} = 4$-5 mJy, at $>3.5\sigma$). The new
SHERRY detections indicate far-infrared (FIR) luminosities of $\rm
3.5\times10^{12}$ to $\rm 1.4\times10^{13}$ $L_{\odot}$, implying extreme star
formation rates of 90 to 1060 $M_{\odot}$ yr$^{-1}$ in the quasar host
galaxies. Compared with $z =$ 2$-$5 samples, the FIR luminous quasars ($L_{\rm
FIR} > 10^{13}\,L_{\odot}$) are more rare at $z \sim 6$. The
optical/near-infrared (NIR) spectra of these objects show 11% (6/54) of the
sources have weak Ly$\alpha$, emission line features, which may relate to
different sub-phases of the central active galactic nuclei (AGNs). Our SCUBA2
survey confirms the trend reported in the literature that quasars with
submillimeter detections tend to have weaker ultraviolet (UV) emission lines
compared to quasars with nondetections. The connection between weak UV quasar
line emission and bright dust continuum emission powered by massive star
formation may suggest an early phase of AGN-galaxy evolution, in which the
broad line region is starting to develop slowly or is shielded from the central
ionization source, and has unusual properties such as weak line features or
bright FIR emission.
