Chun-Wei Yang

Quantum dialogue protocols immune to collective noise

This work proposes two quantum dialogue protocols, each of which is robust against one of the following two kinds of collective noise: collective-dephasing noise and collective-rotation noise. Both quantum dialogue protocols are constructed from four-qubit DF states that consist of two Bell states. The receiver simply performs two Bell state measurements to obtain the secret message. Moreover, the proposed protocols are free from information leakage because some shared private quantum states are established in the new protocols to allow the legitimate users to exchange their secret messages securely.

Quantum private comparison of equality protocol without a third party

This paper presents a novel quantum private comparison protocol that uses Einstein–Podolsky–Rosen pairs. The proposed protocol allows two parties to secretly compare their information without exposing their actual contents. The technique of entanglement swapping enables the comparison to be achieved without the help of a third party. Moreover, because the proposed protocol employs one-step transmission and decoy photons, it is secure against the various quantum attacks in existence thus far.

EFFICIENT KEY CONSTRUCTION ON SEMI-QUANTUM SECRET SHARING PROTOCOLS

Semi-quantum secret sharings (SQSSs), as they are of now, require all the agents choose to measure the received qubits to produce the shared secret key. As a result, to share an n-bit secret key in an (m + 1)-party SQSS, the number of quanta required to transmit is n × 2m, which increases exponentially with the number of agents (i.e. m). This study proposes a new idea on the construction of the secret key for the existing SQSS such that only 2nm qubits are required to produce an n-bit secret key in the (m + 1)-party SQSS.

Quantum authencryption: one-step authenticated quantum secure direct communications for off-line communicants

This work proposes a new direction in quantum cryptography called quantum authencryption. Quantum authencryption (QA), a new term to distinguish from authenticated quantum secure direct communications, is used to describe the technique of combining quantum encryption and quantum authentication into one process for off-line communicants. QA provides a new way of quantum communications without the presence of a receiver on line, and thus makes many applications depending on secure one-way quantum communications, such as quantum E-mail systems, possible. An example protocol using single photons and one-way hash functions is presented to realize the requirements on QA.

Fault tolerant quantum key distributions using entanglement swapping of GHZ states over collective-noise channels

This work proposes two fault tolerant quantum key distribution (QKD) protocols. Each of which is robust under one kind of collective noises: collective-dephasing noise and collective-rotation noise, respectively. Due to the use of the entanglement swapping of Greenberger–Horne–Zeilinger (GHZ) state as well as the decoy logical qubits, the new protocols provide the best qubit efficiency among the existing fault tolerant QKD protocols over the same collective-noise channel. The receiver simply performs two Bell measurements to obtain the raw key. Moreover, the proposed protocols are free from several well-known attacks and can also be secure over a lossy channel.

Trojan horse attack free fault-tolerant quantum key distribution protocols

This work proposes two quantum key distribution (QKD) protocols—each of which is robust under one kind of collective noises—collective-dephasing noise and collective-rotation noise. Due to the use of a new coding function which produces error-robust codewords allowing one-time transmission of quanta, the proposed QKD schemes are fault-tolerant and congenitally free from Trojan horse attacks without having to use any extra hardware. Moreover, by adopting two Bell state measurements instead of a 4-GHZ state joint measurement for decoding, the proposed protocols are practical in combating collective noises.

Fault tolerant deterministic quantum communications using GHZ states over collective-noise channels

This study proposes two new coding functions for a GHZ state and a GHZ-like state, respectively. Based on these coding functions, two fault tolerant deterministic quantum communication (DQC) protocols are proposed. Each of the new DQC’s is robust under one kind of collective noises: collective-dephasing noise and collective-rotation noise, respectively. The sender can use the proposed coding functions to encode his/her message, and the receiver can perform the Bell measurement to obtain the sender’s message. In comparison to the existing fault tolerant DQC protocols over collective-noise channels, the proposed protocols provide the best qubit efficiency. Moreover, the proposed protocols are also free from the ordinary eavesdropping and the information leakage.

Fault tolerant authenticated quantum direct communication immune to collective noises

This study proposes two new coding functions for GHZ states and GHZ-like states, respectively. Based on these coding functions, two fault tolerant authenticated quantum direct communication (AQDC) protocols are proposed. Each of which is robust under one kind of collective noises: collective-dephasing noise and collective-rotation noise, respectively. Moreover, the proposed AQDC protocols enable a sender to send a secure as well as authenticated message to a receiver within only one step quantum transmission without using the classical channels.