Fig. 1. (a) Classical and (b) entanglement-assisted polarimeter configurations.

Fig. 2. Experimental setup and the property of the entangled source. (a) Quantum polarimeter configuration. WP, wave plate set, including a HWP and a QWP; PBS, polarizing beam splitter; DM, dichroic mirror; DPBS, dichroic PBS (@405 nm&810 nm); DHWP, dichroic HWP (@405 nm&810 nm); PSM, off-axis parabolic silver mirror; PPKTP, periodically poled KTP crystal; F, bandpass filter (@810 nm); FC, fiber collimator; SPAD, single-photon avalanche diode; TDC, time-digital converter. (b), (c) Properties of the polarization-entangled photon source. (b) Coincidence counts in 10 s as a function of the HWP angle with the horizontal (diagonal) projection bases. The background dark coincidence is not subtracted. The error bars are obtained from multiple measurements. (c-1) and (c-2) The real and imaginary parts of the reconstructed density matrix of the prepared polarized entangled source using the maximum-likelihood estimation method.

Fig. 3. Phase retardance measurements of the PSA quantum polarimeter. (a)–(c) Measurement results for an HWP. (d)–(f) Measurement results for a QWP. (a) and (d) Single measurement for the HWP and the QWP. Error bars are obtained from multiple measurements. (b) and (e) Phase retardation under varying sample axes θ. (c) and (f) Time stability over 2.5 h.

Fig. 4. Performance comparison for relative phase retardance measurements. All results are measured from the H-base. Green line, data from a PSCA quantum polarimeter; red line, data from a PSCA classical polarimeter; purple line, data from a PSA quantum polarimeter (same as the purple lines in Fig. 3). (a),(d), (b),(e), and (c),(f) Same test items as Fig. 3.