基于具有极化和空模自由度的单光子的带第三方的半量子对话和半量子会议

This paper proposes a novel semiquantum dialogue (SQD) scheme with a third party (TP) by using single photons in both polarization and spatial-mode degrees of freedom, in order to accomplish the goal that two semiquantum communicants can synchronously exchange their secret messages under the assistance of a semi-honest TP possessing complete quantum capabilities. In order to guarantee the decoding synchronization of this SQD scheme, TP is responsible for publishing the final ciphertext to two semiquantum secrecy communicants so that they can decode out each other’s secret message. This SQD scheme utilizes the method of one-time pad (OTP) to erase the risk of information leakage. The merits of this SQD scheme are as follows: (1) it adopts single photons in both polarization and spatial-mode degrees of freedom as quantum resources, rather than quantum entangled states; (2) it implements single-photon measurements rather than quantum entangled state measurements; (3) quantum participant (i.e., TP) does not need to implement any unitary operation; (4) semiquantum participants do not need any quantum memory; (5) it has the decoding synchronization. Finally, this paper enlarges the number of semiquantum secrecy communicants and suggests the first semiquantum conference (SQC) scheme with a TP, where multiple semiquantum secrecy communicants can synchronously exchange each other’s secret message with the assistance of a semi-honest TP possessing complete quantum capabilities.