Optimal 1D Ly$\alpha$ Forest Power Spectrum Estimation -- II. KODIAQ,
  SQUAD & XQ-100
  We measure the 1D Ly$\,\alpha$ power spectrum \poned from Keck Observatory
Database of Ionized Absorption toward Quasars (KODIAQ), The Spectral Quasar
Absorption Database (SQUAD) and XQ-100 quasars using the optimal quadratic
estimator. We combine KODIAQ and SQUAD at the spectrum level, but perform a
separate XQ-100 estimation to control its large resolution corrections in
check. Our final analysis measures \poned at scales $k<0.1\,$s$\,$km$^{-1}$
between redshifts $z=$ 2.0 -- 4.6 using 538 quasars. This sample provides the
largest number of high-resolution, high-S/N observations; and combined with the
power of optimal estimator it provides exceptional precision at small scales.
These small-scale modes ($k\gtrsim 0.02\,$s$\,$km$^{-1}$), unavailable in Sloan
Digital Sky Survey (SDSS) and Dark Energy Spectroscopic Instrument (DESI)
analyses, are sensitive to the thermal state and reionization history of the
intergalactic medium, as well as the nature of dark matter. As an example, a
simple Fisher forecast analysis estimates that our results can improve
small-scale cut off sensitivity by more than a factor of 2.
