Optical Quantum Information Processing Based On Cross-kerr Effect

The robustness and the characteristic of easy to be transmitted make pho-ton one of ideal quantum information carrier. Hence, optical system has always been the research hot spot for the physical implementation of quantum informa-tion. Qubit is usually encoded on the vertical and horizontal polarization states of linearly polarized light, and optical quantum information task is achieved by using linear optical elements. However, because of the difficulty for photonic inter-action and the probabilistic nature of linear optical quantum gates, it is difficult to achieve deterministic optical quantum-information processing in linear optical system. Cross-Kerr medium can induce interaction between the photons in probe mode and signal mode by cross phase modulation, which offers an ideal playground for deterministic optical quantum information processing.In this dissertation, we first summarize the basic principles and methods of optical quantum information processing by using cross-Kerr nonlinearity in detail. Then we investigate the optical quantum information processing based on both weak and giant cross-Kerr nonlinearity. The main research contents are following:(1) Based on weak cross-Kerr nonlinearity, we propose a simplified photonic qubit parity meter. Compared with the existing parity meters, the present one includes fewer optical elements and decreases the error probability from10-5to10-72. On the other hand, if we have the same error probability as the existing parity meters, the phase shift required in our scheme reduces to half, which will be more feasible in the experiment. Using the simplified parity meter, We design a complete Bell-state analyzer. The analyzer can completely distinguish the four Bell states with unit probability, which is also used to achieve the perfectly teleportation of an arbitrary unknown single-qubit state. Moreover, with the aid of classical feedforward, we propose a scheme for generating multi-particle cluster states.(2) Based on giant cross-Kerr nonlinearity, we construct a complete N-photon Greenberger-Horne-Zeilinger (GHZ)-state analyzer with the idea of disentanglement. The present analyzer includes fewer optical elements and simpler operations than the exiting ones. Another advantage is that the analyzer is invertible, i.e. by interchanging the input ports and the output ports of the disentangler in our GHZ-state analyzer, the disentangler can become into a entangler for generating GHZ states. With the aid of the GHZ-state analyzer, we propose a multi-bit dense coding scheme using only an Einstein-Podolsky-Rosen (EPR) channel, which indicates that whatever the number of the classical bits is, the quantum channel is always a Bell state. The present dense coding process, meanwhile, can extra prepare non-local multi-particles GHZ states at one of the participants. The quantum circuits of this dense coding process are constructed, followed by deterministic implementation methods in optical system based on cross-Kerr nonlinearity. Finally, we propose a quantum teleportation protocol of an arbitrary non-maximally iV-qubit GHZ-class state. The scheme requires a maximum GHZ states as entangled channel shared by two communication parties, and the receiver can perfectly reconstruct the teleported state by local operations and classical communication. This is the first theoretical scheme for deterministic implementation of multi-qubit GHZ-class state in optical system. All of these schemes are nearly deterministic in the regime of little noise, so they have very important value for the research of quantum information processing based on optical system and can provide reliable theory basis for the experiment implementation of optical quantum information and quantum computation.