Figure 6: Reconstructed causal maps.
Reconstruction of the real and imaginary parts of the Choi state 
when targeting four combinations of cause-effect and common-cause mechanisms: (a) PROBC, (b) PHYSC, (d) PROBQ and (d) COH. The causal maps for a,b are given in the local bases that diagonalize the target map, to make explicit their classical nature; no such bases exist for c,d. Blue (red) colour bars represent positive (negative) values. The fidelities30, 
, to the theoretically calculated Choi state τth are high, at (98.1±0.2)%, (98.06±0.08)%, (97.1±0.1)% and (93.7±0.3)%, respectively, verifying that the experiment is performing as intended. Uncertainties on fidelities indiciate one s.d. and are estimated using Monte-Carlo simulations with Poissonian noise on photon counts. Notation for polarization states: 
, horizontal, 
vertical, 
diagonal, 
anti-diagonal, 
right-circular, 
left-circular.
