Transferring Quantum Information In Cavity QED

Quantum information theory is an inter-discipline of quantum mechanics and information theory, which is competent in some of impossible task within the classical information science. Quantum information theory shows the superiorities beyond compare in classical information. Quantum information theory includes quantum computation and quantum communication, quantum communication is a way of effective information transmission using quantum state as information unit, including quantum teleportation, quantum dense coding, quantum secret sharing, etc.In order to implement quantum information processing, we need construct the hardware of operating qubit, cavity QED is one of the most promising candidates serving as hardware of quantum information. One of the distinct advantages of quantum information processing in the context of cavity QED is that the manipulation is very simple, and the system is easy to scalable. Up to now, quantum information processing in cavity QED is mainly in the theoretical stage, thus it is extremely important to find experimental feasible scheme for quantum information processing in the context of cavity QED. Transferring of quantum information is an important researched branch of quantum information, in this paper, quantum information transfer in cavity QED is studied, transferring of quantum information via SQUIDs-cavity field interaction is studied too, some mainly results including1. We propose schemes for transferring an unknown atomic entangled state and a two-atom product state in cavity QED. Our schemes do not require Bell-state measurement. Meanwhile the schemes only involve atom-field interaction with a large detuning and do not require the transfer of quantum information between the atoms and cavity. During the passage of the atoms the cavity is only virtually excited; thus the requirement on the quality factor of the cavity is greatly loosened. The schemes can also be extended to transfer entangled state of N-atom.2. A scheme for transferring of a two-mode entanglement of zero-and one-photon entangled states between two cavities via atom-cavity field resonant interaction is proposed. This scheme does not require Bell-state measurement and performing any transformations to reconstruct the initial state. And the transfer can occur with 100% success probability in a simple manner. And a network for transfer of a two-mode entangled state between cavities is suggested. This scheme can also be extended to transfer A-mode entangled state of cavity. This scheme can also be used to transferring an unknown atomic entangled state.3. A simple scheme for transferring of a two-atom product state based on atom-cavity field resonant interaction is proposed. The scheme does not require performing any transformations to reconstruct the initial state and does not require Bell-state measurement. In addition, the transfer of the scheme has a successful probability of 100 percent in a simple manner. And the scheme can also be extended to transfer product state of n-atom.4. We present a scheme for transferring two-atom quantum state with a single resonant interaction. The scheme only requires a single resonant interaction of the atoms with a cavity mode and does not use the cavity mode as the memory. Thus the scheme is very simple and the interaction time is very short, which is important in view of decoherence. Quantum state can be directly transferred from two atoms to the other two atoms with a successful probability of 100%.5. We also present a scheme for transferring Quantum information of two superconducting quantum interference device (SQUID) qubits in cavity QED to another two SQUID qubits. In the scheme the quantum information can be directly transferred with a successful probability of 100% in a simple manner. In addition, no quantum information is transferred between the SQUIDs and the cavities, the cavity-fields are only virtually excited, thus the requirement on the quality factor of the cavities is greatly relaxed. And meanwhile we can establish a network for transferring quantum information between SQUID qubits.