The Study On Quantum Key In The Quantum Information

Quantum information is a new cross-discipline subject, which is just emerging in recent years. It combines the advantages of quantum mechanics and information science. And it includes such two parts as quantum communication and quantum computing. Among them, quantum communication is the core of quantum information, because it can provide a safer method for the transmission of information. In recent years, this technology has been the transition from the initial theoretical study to the experimental and a lot of achievements in theory and experiment have been made. And the technology is moving towards a practical use. The main contents of the current quantum communication, including the following aspects: quantum dense coding, quantum teleportation, quantum key distribution, quantum secret sharing, quantum key agreement and quantum remote state preparation.Among them, Quantum dense coding technology and quantum teleportation technology are very important. They are widely used in the transmission of information in the process. It can be said that these two plays a vital role in the development of quantum communication.As we all know, information plays a vital role in people’s lives, who grasp the latest information on who will be able to hold a dominant position in the increasingly fierce competition. Thus ensuring the security of the information has become a more and more important task. In order to ensure that the information is not stolen, people to traditional cryptography and quantum technology and have achieved better result.At present, many kinds of physical systems are used to process quantum information. Such as the cavity QED system, the linear optical systems, the magnetic resonance imaging system and so on.Due to that the optical system has lots of advantages, such as it has long decoherence time, photons being easily transported, prepared and manipulated. It has boarder prospects for development. This paper has done some research on a branch of quantum communication-Quantum Key Agreement Scheme. The results are as follows:(1) A new quantum key agreement protocol via the block transmission of the EPR pairs. In this protocol, we use the technology of quantum dense coding to coded message and transfer the message using EPR pairs. We greatly improve the efficiency of quantum key agreement. And two times of security test was adopted to guarantee the security of this protocol.(2) A linear optical protocol of quantum key agreement by using polarization entangled photons.In this protocol, we use single-phone two-qubit states to transfer the information. Two parts can add their contribution on the states by doing unitary operations. And two kinds of distinguish devices can distinguish among all of the single-photon two-qubit Bell-state. They can derive the key.