Fig. 1. Illustration of heterodyne measurement USD strategy in a post-selection region of phase space

Fig. 2. Schematic of quantum measurement scheme

Fig. 3. Schematic of the hybrid measurement scheme for USD of QPSK coherent states

Fig. 4. Illustration of the HD in classic measurement stage of phase space

Fig. 5. Illustration of displacement operation in phase space. (a) Dis-placement operations with \begin{document}$ \widehat{D}\left(-{\gamma }_{1}\right) $\end{document}; (b) Displacement opera-tions with \begin{document}$ \widehat{D}\left(-{\gamma }_{2}\right) $\end{document}

Fig. 6. Total process of the hybrid measurement scheme

Fig. 7. Schematic of the optimal partition ratio for \begin{document}$ M=1+2 $\end{document} partitional USD hybrid measurement scheme

Fig. 8. Simulation results diagram of \begin{document}$ M=1+2 $\end{document} partitioned USD hybrid measurement scheme. (a) Correct rate; (b) Error ratio

Fig. 9. Schematic of the optimal partition ratio for \begin{document}$ M=1+3 $\end{document} partitional USD hybrid measurement scheme

Fig. 10. Simulation results diagram of \begin{document}$ M=1+3 $\end{document} partitioned USD hybrid measurement scheme. (a) Correct rate; (b) Error ratio