  Engineering apparatus that harness quantum theory offers practical advantages
over current technology. A fundamentally more powerful prospect is the
long-standing prediction that such quantum technologies could out-perform any
future iteration of their classical counterparts, no matter how well the
attributes of those classical strategies can be improved. Here, we
experimentally demonstrate such an instance of \textit{absolute} advantage per
photon probe in the precision of optical direct absorption measurement. We use
correlated intensity measurements of spontaneous parametric downconversion
using a commercially available air-cooled CCD, a new estimator for data
analysis and a high heralding efficiency photon-pair source. We show this
enables improvement in the precision of measurement, per photon probe, beyond
what is achievable with an ideal coherent state (a perfect laser) detected with
$100\%$ efficient and noiseless detection. We see this absolute improvement for
up to $50\%$ absorption, with a maximum observed factor of improvement of 1.46.
This equates to around $32\%$ reduction in the total number of photons
traversing an optical sample, compared to any future direct optical absorption
measurement using classical light.
