Quantum Superdense Coding And Quantum Logic Gates Based On Nondestrutive Detection

Quantum informatics has become one of the hot topics in the study of physics and information science. Compared with classical information processing, quantum information processing has great advantages, and can greatly improve the efficiency and security of information processing. The optical system is very potential for quantum information processing system. Because the optical Quantum informa-tion processing has many advantages, such as insensitivity to outside influences, easy preparation and transportation, low discoherence, and easy single qubit op-eration. This paper introduces the basic knowledge of quantum information science and the optical realization of quantum information processing, as well as the con-cept of hyperentanglement, the method of preparation of hyperentanglement and the principle and application of quantum nondestructive measure.At first, a quantum super dense coding scheme based on polarization-frequency hyperentanglement and quantum nondestructive detection is proposed in this paper. There are totally16operations which Alice can perform, corresponding to4bits classical information, so We can achieve4bits classical information transmission by sending a quantum bit. And our scheme is approximate deterministic, and won’t destroy the quantum state of the system. We propose two bits and three bits quan-tum logic gate by the use of cross-Kerr nonlinearity and nondestructive detectors. In the two bits controlled-Z gate, we use a beam splitter (BS) to adjust the phase of target bits. After the nonlinear interaction between the photons and Kerr non-linearty, We uses a BS to interfere the photon state of target bits in the two pathes. We can achieve controlled-Z gate by the corresponding unitary operations accord-ing to results of homodyne measurement and nondestructive detectors. This CNOT gate needs only one parity detector and no ancilla photon, and of cause, is almost deterministic. There are two three-bit quantum logic gate:Fredkin and Toffoli gate. After the interaction with cross Kerr nonlinear, We need to perform a U operation on the target photons according to the result of homodyne measurement. Then after the interference by BS, quantum three bits logic gate can be realized by the unitary operation in the corresponding path according to the measurement results of quantum nondestructive detectors. According to the different U operations, we can get different three bits quantum logic gates. The success probability for Fredkin or Toffoli gate is close to1. These two bits and three bits quantum logic gates can be realized in the nonlocal area.