Some Theoretical And Experimental Studies On Practical Quantum Communication

Quantum communications is a new frontier subject of science born from thorough overlaps between quantum physics and information science. The quantum communica-tion field presently includes quantum key distribution, quantum teleportation, quantum secret sharing, quantum digital signatures, relativistic quantum bit commitment, quan-tum fingerprinting, quantum repeaters, quantum data locking, and so on. The quantum superposition principle is the core of quantum physic, and utilizing this characteris-tic can allow quantum communication protocols to be more advantageous than their classical counterparts can. Because of these advantages, researchers were motivated to explore the theory and experiments, and advance different quantum communication protocols to practical application directions. Currently, practical technologies in quan-tum key distribution are developing rapidly. For example, the construction of fiber transmission based Beijing-Shanghai Route and Shanghai-Hangzhou Route are set for completion at the end of this year, and the first quantum satellite based on free space transmission in the world "Mozi" and Tiangong 2, which executes the space-ground quantum key distribution tasks, were successfully launched.However, as practical quantum key distribution advances, researchers found dif-ferences between theoretical proofs and the realistic systems, which would open loop-holes in realistic systems and allow quantum hackers to attack them accordingly. These include for instance the photon number splitting attack aiming at sources that emit mul-tiphotons and bright light blinding attacks aiming at the detectors. Therefore, research in the security of realistic systems is one of the most important topics of quantum key distribution. Compared with quantum key distribution, other quantum communication protocols such as quantum fingerprinting, quantum digital signatures, quantum secret sharing and etc. are still in the preliminary stages of theoretical research and proof-of-principle demonstrations, which are still far from the goal of practical uses.The author’s main researches during the doctors program include theoretical and experimental works in quantum key distribution, quantum fingerprinting, and quan-tum digital signatures. Specifically, the author simulated and achieved higher secure key rates and longer secure transmission distance for measurement device independen-t quantum key distribution by using coherent-state superpositions; investigated decoy state measurement device independent quantum key distribution theory based on Bell inequalities; calculated the unconditional secure key rate generation equation for six state SARG04 protocol, which achieved higher error rate threshold; proposed detector decoy round robin differential phase shift quantum key distribution, which removed the requirement of photon number resolving detectors; demonstrated field test of a quantum key distribution network in the presence of an untrusted relay; increased the maximum secure transmission distance of measurement device independent quantum key distribu-tion to 404 km; experimentally observed quantum fingering beating the classical limit that based on a double Sagnac interferometer; experimentally demonstrated uncondi-tionally secure quantum digital signatures over 102 km.