Bidirectional transfer of quantum information for unknown photons via cross-Kerr nonlinearity and photon-number-resolving measurement

We propose an arbitrary controlled-unitary （CU） gate and a bidirectional transfer scheme of quantum information （BTQI） for unknown photons. The proposed CU gate utilizes quantum non-demolition photon-number-resolving measure- ment based on the weak cross-Kerr nonlinearities （XKNLs） and two quantum bus beams; the proposed CU gate consists of consecutive operations of a controlled-path gate and a gathering-path gate. It is almost deterministic and is feasible with current technology when a strong amplitude of the coherent state and weak XKNLs are employed. Compared with the existing optical multi-qubit or controlled gates, which utilize XKNLs and homodyne detectors, the proposed CU gate can increase experimental realization feasibility and enhance robustness against decoherence. According to the CU gate, we present a BTQI scheme in which the two unknown states of photons between two parties （Alice and Bob） are mutually swapped by transferring only a single photon. Consequently, by using the proposed CU gate, it is possible to experimentally implement the BTQI scheme with a certain probability of success.

Controlled mutual quantum entity authentication using entanglement swapping

In this paper, we suggest a controlled mutual quantum entity authentication protocol by which two users mutually certify each other on a quantum network using a sequence of Greenberger–Horne–Zeilinger（GHZ）-like states. Unlike existing unidirectional quantum entity authentication, our protocol enables mutual quantum entity authentication utilizing entanglement swapping; moreover, it allows the managing trusted center（TC） or trusted third party（TTP） to effectively control the certification of two users using the nature of the GHZ-like state. We will also analyze the security of the protocol and quantum channel.

Quantum secure direct communication network with hyperentanglement

We propose a quantum secure direct communication protocol with entanglement swapping and hyperentanglement. Any two users, Alice and Bob, can communicate with each other in a quantum network, even though there is no direct quantum channel between them. The trust center, Trent, who provides a quantum channel to link them by performing entanglement swapping, cannot eavesdrop on their communication. This protocol provides a high channel capacity because it uses hyperentanglement, which can be generated using a beta barium borate crystal.

Bidirectional quantum teleportation of unknown photons using path-polarization intra-particle hybrid entanglement and controlled-unitary gates via cross-Kerr nonlinearity

We propose an arbitrary controlled-unitary （CU） gate and a bidirectional quantum teleportation （BQTP） scheme. The proposed CU gate utilizes photonic qubits （photons） with cross-Kerr nonlinearities （XKNLs）, X-homodyne detectors, and linear optical elements, and consists of the consecutive operation of a controlled-path （C-path） gate and a gathering-path （G- path） gate. It is almost deterministic and feasible with current technology when a strong coherent state and weak XKNLs are employed. Based on the CU gate, we present a BQTP scheme that simultaneously teleports two unknown photons between distant users by transmitting only one photon in a path-polarization intra-particle hybrid entangled state. Consequently, it is possible to experimentally implement BQTP with a certain success probability using the proposed CU gate.

A Quantum Network System of QSS-QDC Using χ-Type Entangled States

A multiuser quantum direct communication network system for N users utilizing χ-type entangled states is prupused. The network system is composed of a communication center,N users,and N quantum lines linking the center and the N users.There is no quantum line among users,and therefore only N quantum lines are necessary for communication between users.Using one χ-type entangled state, in this protocol we are able to send two bits of information through direct communication and,at the same time,share two bits of quantum keys. The security of the protocol is then analyzed.

A Quantum Communication Protocol Transferring Unknown Photons Using Path-Polarization Hybrid Entanglement

We propose a protocol for transferring photons of unknown states to a distant location using path-polarization hybrid entanglement.Our protocol uses a polarizing beam splitter(PBS),a beam splitter(BS),a CNOT-operation,four unitary operations and polarizing detectors.In our protocol,the hybrid entangled states are generated by the PBS,and it is transmitted through the quantum channel containing the BS and CNOT-gate.The measurement results of the polarizing detectors and classical communications determine which unitary operation will be used in the last step for recovering initial states.The security of the channel in transmitting unknown photons between two parties is confirmed by the results of the measurement of each target photon in the control mode.