Characterizing High-Quality High-Dimensional Quantum Key Distribution by State Mapping Between Different Degrees of Freedom

Quantum key distribution (QKD) guarantees the secure communication between legitimate parties with quantum mechanics. High-dimensional QKD (HDQKD) not only increases the secret key rate but also tolerates higher quantum bit error rate (QBER). Many HDQKD experiments have been realized by utilizing orbital-angular-momentum (OAM) photons as the degree of freedom (DOF) of OAM of the photon is a prospective resource for HD quantum information. In this work, we propose that a high-quality HDQKD based on polarization-OAM hybrid states can be realized by utilizing state mapping between different DOFs and we characterize this HDQKD. Both the preparation and measurement procedures of the proofof- principle verification experiment are simple and stable. Our experiment verifies that a 0.60% +/- 0.06% QBER and a 1.849 +/- 0.008-bit secret key rate per sifted signal can be achieved for a four-dimensional QKD with the weak coherent light source and decoy state method.