Extended Data Fig. 3: Polarization state and quantum process tomography.
a, c, Poincaré sphere showing the underlying quantum process of our NPQD. The coloured spheres are the result of polarization state tomography for reflected photonic pulses for the correspondingly coloured and labelled input polarizations. b, d, NPQD underlying quantum process matrix χ which is reconstructed via a maximum-likelihood fit. \({{\mathbb{1}}}_{2}\) denotes the 2 × 2 identity matrix and σx, σy and σz denote the Pauli matrices. In a and b, the photon counts at the tomography setup are conditioned on the nondestructive qubit detection. In c and d, they are not conditioned on the nondestructive detection. The rotation around the A/D axis is described by an operator built by σx. The uncertainty of χm,n is assessed with a Monte Carlo method and represents the standard error.
