Toward Practical Quantum Encryption in Phase Space: Simulated QPSK and 16-QAM with Dynamic Displacement Operators

Abstract We propose and simulate a quantum-enhanced encryption scheme for coherentoptical communication systems based on coherent-state dynamic displacementoperators (DDOs) in phase space. The method integrates random phase shiftoperators (PSOs) and displacement operators (DOs) to dynamically manipu-late information symbols, enabling secure physical-layer encryption. Simulationresults confirm that accurate decryption is only possible with the correct operatorpair; any mismatch in displacement or phase parameters leads to bit error ratesapproaching 50%, effectively blocking unauthorized access. We further comparethe performance of unencrypted transmission with various quantum-enhancedphysical-layer security (QEPS) configurations over different fiber lengths. Theresults validate the robustness of the proposed DDO-based scheme against par-tial or incorrect decryption attempts, underscoring its potential for securing datatransmission in classical optical networks.