A TWO-STEP CHANNEL-ENCRYPTING QUANTUM KEY DISTRIBUTION PROTOCOL

A two-step channel-encrypting quantum key distribution protocol is proposed. Using the previously shared EPR pairs as the quantum key, two bits of classical key can be established via one information carrier EPR state on average. In theory, the efficiency of this protocol reaches 100%, and there is no need to consume any entangled states including both the quantum key and the information carriers in ideal condition. The protocol can resist the particular attack that is fatal to other some channel-encrypting schemes. Principally, we prove the security against the most general individual attack of this protocol. Entanglement collapse in practical situation, as well as the realistic implementation of this protocol is also discussed.

DYNAMIC PROPERTIES OF THE LARGE-DETUNING CAVITY QED SYSTEM IN THE PRESENCE OF CAVITY DECAY

We consider a physical process of two Λ-type three-level atoms interacting with a bimodal cavity including the influence of the cavity decay. We analyze the influence of cavity decay on several physical quantities of the process, such as atomic population probability, residual entanglement, concurrence of two atoms, average population inversion, average photon number, the fidelity for quantum phase gate, and the fidelity of generating atomic EPR state. It is found that all of these physical quantities decrease with the increase of cavity decay when the other relevant parameters are fixed.

EFFICIENT SCHEME FOR EPR STATE AND CLUSTER STATES GENERATION WITH SQUID QUBITS VIA RAMAN TRANSITION

In this paper, a theoretical scheme is proposed to generate the EPR state of two SQUID qubits and create the multipartite cluster states of many SQUID qubits in cavity via Raman transition. We also show how to transfer quantum information from one SQUID qubit to another directly. In this scheme, the cavity field is only virtually excited and thus the cavity decay is suppressed. The quantum information processing and cluster states generation are realized by using only two lower flux states of the SQUID system and the excited state would not be excited. Therefore, the effect of decoherence caused from the levels of the SQUID system is possibly minimized.

REPLY TO: "ON COHEN'S CLASSICAL TELEPORTATION OF CLASSICAL STATES"

In response to a recently published protocol for classical teleportation of classical states [1], Hrasko [2] has made some remarks in connection with the impossibility of precise quantum teleportation if a classical mixture is used in place of the EPR state, and with regard to the epistemological interpretation of quantum states. The purpose of this note is to attempt to clarify these issues and their relevance for the argumentation presented in [1].