Hogan proposed that the holographic principle implies a fundamental, universal quantum uncertainty ('holographic noise') in the transverse position of spacetime at the Planck scale, and co-led the Fermilab Holometer -- twin co-located, power-recycled Michelson interferometers -- to search for it, ruling out the simplest models to high significance. This is a distinct fundamental-light-physics/quantum-sensing approach from squeezed-light-enhanced GW interferometers (e.g., LIGO), using precision laser interferometry to probe quantum properties of spacetime itself rather than squeezing quantum noise in a detector.