Error-Detected Generation of High-Fidelity Photonic Hyperentanglement in Polarization-Spatial-Time Three Degrees of Freedom Assisted by Quantum-Dot Spins.

Photonic hyperentanglement, which involves photons simultaneously entangled in more than one degree of freedom (DOF), has many important applications in quantum information processing, especially in high-capacity quantum communications. Interestingly, single-photon qubits encoded in the time-bin DOF are robust for long-distance transmissions in noisy channels. In this paper, we present a hyperentangled-Bell-state generation (HBSG) scheme for preparing two-photon six-qubit states which are simultaneously entangled in the polarization, spatial-mode, and time-bin DOFs. Compared with previous HBSG schemes, we construct an error-detected circuit unit with a quantum-dot (QD) spin in a double-sided optical microcavity, with which errors due to imperfect interactions between photons and QD systems can be easily detected, so that the error-detected circuit unit can relax the experimental requirement and improve the fidelity of our scheme largely. Meanwhile, our scheme is used to prepare two-photon hyperentangled states in polarization-spatial-time three DOFs, which is significant for faithful entanglement distribution and quantum repeater. These features make our scheme more feasible and useful in high-capacity and long-distance quantum communications with hyperentanglement. [ABSTRACT FROM AUTHOR]