Realization of quantum secure direct communication over 100 km fiber with time-bin and phase quantum states.

Rapid progress has been made in quantum secure direct communication in recent years. For practical application, it is important to improve the performances, such as the secure information rate and the communication distance. In this paper, we report an elaborate physical system design and protocol with much enhanced performance.

Generalized sparse codes for non-Gaussian channels: Code design, algorithms, and applications.

In this paper, generalized sparse (GS) codes are proposed to support reliable and efficient transmission over non-Gaussian channels. Specifically, by expanding the single-parity check (SPC) code constraints with powerful algebraic codes, GS codes generalize conventional sparse codes with enhanced error-correcting capability, as well as better code design flexibility by covering a wide range of block-lengths and coding rates with reduced encoding/decoding complexity. Moreover, by introducing a universal communication channel model, a general framework for performance analysis and code design of GS codes is formulated, by which the coding parameters can be optimized for different target channel conditions.

Entanglement protection of Ince-Gauss modes in atmospheric turbulence using adaptive optics.

In this paper, we describe the study of the faithful propagation of entangled orbital angular momentum states of light under atmospheric turbulence. The spatial mode is encoded in the Ince-Gauss modes that constitute a complete family of exact and orthogonal solutions of the paraxial wave equation in an elliptic coordinate system. Adaptive optics is employed to protect the entanglement from degradation, in which the threshold of turbulence strength could be enhanced for a reliable entanglement distribution.

Implementation and security analysis of practical quantum secure direct communication.

Rapid development of supercomputers and the prospect of quantum computers are posing increasingly serious threats to the security of communication. Using the principles of quantum mechanics, quantum communication offers provable security of communication and is a promising solution to counter such threats. Quantum secure direct communication (QSDC) is one important branch of quantum communication.

Measurement-device-independent quantum communication without encryption.

Security in communication is vital in modern life. At present, security is realized by an encryption process in cryptography. It is unbelievable if a secure communication is achievable without encryption.