  We demonstrate that the LHC will be sensitive to quantum correlations between
two quarks inside the proton. Same-sign W-boson pair production is the most
promising channel for clear measurements of double parton scattering. The
left-handed nature of the coupling between quarks and W-bosons makes it a prime
probe to measure parton spin correlations. We perform a detailed analysis of
double parton scattering, including relevant backgrounds. The analysis reveals
that measurements comparing the rate at which two muons from W boson decays are
produced in the same compared to opposite hemispheres are especially sensitive
to spin correlations between two quarks inside the proton. We provide estimates
of the significance of the measurements as a function of the integrated
luminosity.
