Our goals are ( i ) to search for BAO and large-scale structure in current QSO survey data and ( ii ) to use these and simulation/forecast results to assess the science case for a new , \ga 10 \times larger , QSO survey .
We first combine the SDSS , 2QZ and 2SLAQ surveys to form a survey of \approx 60000 QSOs .
We find a hint of a peak in the QSO 2-point correlation function , \xi ( s ) , at the same scale ( \approx 105 h ^ { -1 } Mpc ) as detected by Eisenstein et al .
( 21 ) in their sample of DR5 LRGs but only at low statistical significance .
We then compare these data with QSO mock catalogues from the Hubble Volume N-body light-cone simulation used by Hoyle et al .
( 33 ) and find that both routes give statistical error estimates that are consistent at \approx 100 h ^ { -1 } Mpc scales .
Mock catalogues are then used to estimate the nominal survey size needed for a 3-4 \sigma detection of the BAO peak .
We find that a redshift survey of \approx 250000 z < 2.2 QSOs is required over \approx 3000 deg ^ { 2 } .
This is further confirmed by static log-normal simulations where the BAO are clearly detectable in the QSO power spectrum and correlation function .
The nominal survey would on its own produce the first detection of , for example , discontinuous dark energy evolution in the so far uncharted 1 < z < 2.2 redshift range . We further find that a survey with \approx 50 % higher QSO sky densities and 50 % bigger area will give an \approx 6 \sigma BAO detection , leading to an error \approx 60 % of the size of the BOSS error on the dark energy evolution parameter , w _ { a } .

Another important aim for a QSO survey is to place new limits on primordial non-Gaussianity at large scales .
In particular , it is important to test tentative evidence we have found for the evolution of the linear form of the combined SDSS + 2QZ + 2SLAQ QSO \xi ( s ) at z \approx 1.6 , which may be caused by the existence of non-Gaussian clustering features at high redshift .
Such a QSO survey will also determine the gravitational growth rate at z \approx 1.6 via redshift-space distortions , allow lensing tomography via QSO magnification bias while also measuring the exact luminosity dependence of small-scale QSO clustering .