Quantum dialogue mediated by EPR-type entangled coherent states

• Published in: Quantum information processing Vol. 20; no. 3
• Main Author: An, Nguyen Ba
• Format: Journal Article
• Language: English
• Published: New York Springer US 01-03-2021; Springer Nature B.V
• Subjects: Coherence; Continuity (mathematics); Control methods; Data Structures and Information Theory; Entangled states; Mathematical Physics; Physics; Physics and Astronomy; Quantum Computing; Quantum cryptography; Quantum Information Technology; Quantum Physics; Security; Spintronics; Quantum dialogue; Entangled coherent states; Information leakage; Eve in the line; Two types of control round; Communication round
• ISSN: 1570-0755; 1573-1332
• DOI: 10.1007/s11128-021-03007-1

Talking with each other on the telephone is convenient but insecure because the conversation content can be eavesdropped perfectly. Quantum dialogue protocols have thus been devised to enable two parties to talk with a reasonable level of security suited to urgent situations without the need of a prior quantum key distribution. Existing protocols use either discrete-variable or continuous-variable entangled states each of which has its own pros and cons. Here we employ Einstein–Podolky–Rosen-type entangled coherent states with fixed and large enough amplitudes which are intermediate between discrete- and continuous-variable states. The outstanding pros is the possibility of unambiguous and efficient identification of a given entangled coherent state which is necessary for the decoding process. Single-mode gates required for the encoding process are executable as well, possibly with the assistance of additional resources. Two types of control methods are introduced to protect the quantum dialogue from outsider’s attacks. The information leakage problem is also discussed showing that it hardly influences the protocol security for a long enough dialogue.